General Anaesthetic Agents

Descripción

Doctorate Anaesthesia Mapa Mental sobre General Anaesthetic Agents, creado por melian.yates el 21/10/2013.
melian.yates
Mapa Mental por melian.yates, actualizado hace más de 1 año
melian.yates
Creado por melian.yates hace alrededor de 11 años
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Resumen del Recurso

General Anaesthetic Agents
  1. General Anaesthesia
    1. Unconsciousness
      1. Analgesia
        1. Muscle relaxation
      2. Anaesthetics
        1. Interaction w/ ligand gated channels
          1. GABAa
            1. Glycine receptor
              1. NMDA
                1. Nicotenic Acetylcholine receptor
          2. Potency correlated to Lipid solubility
        2. Injectable
          1. More action on Brain
            1. Minimal Equipment required
              1. Some require ventilation
              2. No pollution from Gases & Inhalation agents
                1. Recovery relies on Redistribution & Metabolism
                  1. Not all drugs are suitable for maintenance
                    1. Induction
                      1. Short procedures
                      2. Maintenance
                        1. TIVA
                          1. Incremental doses
                            1. Continuous rate infusion (CRI)
                        2. Supplementation to Inhalational Anaesthesia
                          1. Long term sedation in ICU
                            1. Tx of Status Epilepticus
                              1. Absorption
                                1. IV (Most)
                                  1. Cause loss of consciousness in 1 injection site - brain circulation time
                                    1. Exception: Ketamine
                                  2. IM
                                    1. IP
                                      1. SC
                                        1. Intra- animal...
                                  3. Ideal Properties
                                    1. No drugs have all Ideal characteristics
                                    2. Drugs
                                      1. Barbituates
                                        1. Derivatives of Barbituric Acid
                                          1. Thiopental
                                            1. Used most often in Clinical Practice
                                              1. Not licensed
                                                1. Absorption
                                                  1. Na+ salt formulation
                                                    1. Alkaline solution (pH: 10.5)
                                                      1. Very irritant on Perivascular injection
                                                        1. Necrosis!
                                                          1. If accidental Extravascular injection
                                                            1. Dilute w/ sterile saline
                                                        2. Hypoproteinaemia: Reduced Dose
                                                        3. Distribution
                                                          1. Ultra-short acting
                                                            1. Rapid loss of Consciousness
                                                              1. Crosses Placenta
                                                              2. Side Effects
                                                                1. Dose dep. Resp. depression
                                                                  1. Apnoea (possible) after induction
                                                                    1. CV depression
                                                                      1. Hypotension
                                                                        1. Reduction of myocardial contractility
                                                                          1. Reduces SVR
                                                                            1. Compensatory Tachycardia possible
                                                                              1. Ventricular Arrhythmias possible
                                                                                1. Sensitizes heart to Catecholamines
                                                                        2. CNS
                                                                          1. Poor muscle relaxation
                                                                            1. NO Analgesic properties (Hyperalgesia)
                                                                            2. Anti-convulsant
                                                                              1. Decreases Intracranial pressure
                                                                              2. Cheap
                                                                                1. Uses
                                                                                  1. IV induction (Dogs & Cats)
                                                                                    1. IV Catheter
                                                                                      1. Premeds decrease dose
                                                                                        1. Not recommended for Maintanence
                                                                                  2. Pentobarbital
                                                                                    1. Not used in clinical practice much anymore - Long recovery time
                                                                                      1. Licensed for Euthanasia of small animals and cattle
                                                                                        1. Oxygen analogue of Thiopental
                                                                                          1. Absorption
                                                                                            1. Soluble in H20 - Unstable
                                                                                              1. Presented in Propylene Glycol
                                                                                                1. IV (IP)
                                                                                                2. Distribution
                                                                                                  1. Slow Onset (Max effects)
                                                                                                    1. Long duration of action
                                                                                                    2. Metabolism
                                                                                                      1. Rapid (Sheep, Goats & Horses)
                                                                                                      2. Elimination
                                                                                                        1. Low Clearance: Dogs, Cats & Pigs
                                                                                                        2. NOT recommended for Anaesthesia
                                                                                                        3. Phenobarbital
                                                                                                          1. Methohexital
                                                                                                            1. Not used much in clinical practice yet
                                                                                                            2. Low doses: Sedatives & Hypnotics
                                                                                                              1. Higher doses: Anaesthetic agents
                                                                                                                1. Slow onset & prolonged action
                                                                                                              2. Increased Lipid Solubility
                                                                                                                1. Increases Potency
                                                                                                                  1. Rapid onset of action
                                                                                                                    1. Shortens duration of action
                                                                                                                  2. C5: Increasing carbon chain
                                                                                                                    1. Branched chains e.g. thio, metho
                                                                                                                      1. Double/triple bonds
                                                                                                                        1. C2: Replacing O with S
                                                                                                                          1. e.g. thio
                                                                                                                      2. Added phenyl group confers Anti-convulsant properties
                                                                                                                        1. Ex. Phenobarbital
                                                                                                                      3. Methohexital > Thiopental > Pentobarbital
                                                                                                                      4. pKa & Protein binding
                                                                                                                        1. Ex. Thiopental
                                                                                                                          1. pKa = 7.6 (61% unionized @ pH 7.4)
                                                                                                                            1. PPB: 85%
                                                                                                                            2. Only unionized unbound drug is free to cross membranes
                                                                                                                              1. Lipid soluble drugs cross faster
                                                                                                                            3. Distribution
                                                                                                                              1. Vd: Large (> 1L/kg)
                                                                                                                                1. Rapid distribution to tissues
                                                                                                                                  1. Accumulation in Fatty tissues
                                                                                                                                    1. Redistribution important for Recovery
                                                                                                                                2. Drug injected into circulation
                                                                                                                                  1. Distribution to highly vascularized tissues (secs)
                                                                                                                                    1. [Thiopental] in brain reaches high level quickly after injection
                                                                                                                                      1. Above yellow line: Unconsciousness
                                                                                                                                        1. Below yellow line: Consciousness
                                                                                                                                      2. Takes longer to equilibriate with tissues
                                                                                                                                        1. Fat poorly perfused (vs. muscle, etc.) takes longest to equilibriate w/ blood
                                                                                                                                  2. Metabolism
                                                                                                                                    1. Liver
                                                                                                                                      1. Slow: Cats, Dogs, Horses
                                                                                                                                        1. Fast: Ruminants
                                                                                                                                          1. Oxidation & Desulfation
                                                                                                                                          2. Prolonged Recovery
                                                                                                                                            1. Large Doses
                                                                                                                                              1. Repeated Doses
                                                                                                                                                1. Accumulation: Repeated administration of Thiopental
                                                                                                                                                2. Note: Greyhounds
                                                                                                                                            2. Phenols
                                                                                                                                              1. Propofol
                                                                                                                                                1. Absorption
                                                                                                                                                  1. White aqueous/oil emulsion - soybean oil, egg lecithin & glycerol
                                                                                                                                                    1. Lipid formulation - Very good culture medium
                                                                                                                                                    2. Lipid free micro-emulsion, antimicrobial preservative
                                                                                                                                                      1. IV
                                                                                                                                                        1. Non-irritant Extravascularly
                                                                                                                                                          1. Pain on injection
                                                                                                                                                          2. Crosses Placenta
                                                                                                                                                            1. Dose given to Effect
                                                                                                                                                            2. Distribution
                                                                                                                                                              1. Very lipid soluble
                                                                                                                                                                1. Almost entirely unionized at pH: 7.4
                                                                                                                                                                  1. PPB: 98%
                                                                                                                                                                    1. Rapid induction
                                                                                                                                                                      1. Vd: Large (>4L/kg)
                                                                                                                                                                      2. Metabolism
                                                                                                                                                                        1. Much higher metabolism than Thiopental
                                                                                                                                                                          1. Better Pharmakinetics for Repeated Doses
                                                                                                                                                                            1. Can infuse for many Hrs (Dog)
                                                                                                                                                                              1. I.e. Rapid recovery
                                                                                                                                                                              2. Liver
                                                                                                                                                                                1. Quinol sulfate & Glucuronide conjugates
                                                                                                                                                                                  1. Note: Cats
                                                                                                                                                                                2. Extrahepatic Clearance
                                                                                                                                                                                  1. Lungs, Kidneys, Blood
                                                                                                                                                                                3. Elimination
                                                                                                                                                                                  1. Rapid Clearance (10-20x faster than Thiopental)
                                                                                                                                                                                  2. Licensed in Dogs & Cats
                                                                                                                                                                                    1. Side Effects
                                                                                                                                                                                      1. Dose dependent Resp. depression
                                                                                                                                                                                        1. Post- induction Anpnoea > Thiopental
                                                                                                                                                                                          1. Post- induction cyanosis
                                                                                                                                                                                            1. Due to opening of shunts in the lungs
                                                                                                                                                                                              1. Concern if existing respiratory compromise
                                                                                                                                                                                                1. Transient - improves w/ intubation & O2
                                                                                                                                                                                            2. Administer SLOWLY
                                                                                                                                                                                              1. Dose dependent cardiovascular depression
                                                                                                                                                                                                1. Reduced SVR
                                                                                                                                                                                                  1. No Compensatory Tachycardia
                                                                                                                                                                                                2. Dose Dependent
                                                                                                                                                                                                  1. High Doses: More pronounced
                                                                                                                                                                                                3. Effects
                                                                                                                                                                                                  1. Not Arrhytmogenic & does not sensitize heart to Catecholamines
                                                                                                                                                                                                    1. Occasional Muscle twitching or Opistotonus
                                                                                                                                                                                                      1. Can cause Overdose
                                                                                                                                                                                                        1. Usually good muscle relaxation
                                                                                                                                                                                                        2. Decreases Intracranial pressure
                                                                                                                                                                                                          1. Bronchodilation
                                                                                                                                                                                                            1. Anti-convulsant
                                                                                                                                                                                                              1. Low Doses: Sedation in ICU
                                                                                                                                                                                                        3. Uses
                                                                                                                                                                                                          1. Same day, Short Procedures
                                                                                                                                                                                                            1. TIVA (Dogs)
                                                                                                                                                                                                              1. Rabbits, birds, reptiles
                                                                                                                                                                                                                1. Dose decreased by pre-med
                                                                                                                                                                                                            2. Cyclohexanones
                                                                                                                                                                                                              1. Derivatives of Phencyclidine
                                                                                                                                                                                                                1. LSD, Ectasy
                                                                                                                                                                                                                2. Ketamine
                                                                                                                                                                                                                  1. Racemic mixture
                                                                                                                                                                                                                    1. S(+) more potent
                                                                                                                                                                                                                      1. R(-) More cardiac depression & delirium
                                                                                                                                                                                                                      2. Licensed Dogs, Cats, Horses, non-human Primates
                                                                                                                                                                                                                        1. Absorption
                                                                                                                                                                                                                          1. Pain on IM Injection
                                                                                                                                                                                                                            1. IV
                                                                                                                                                                                                                              1. SC
                                                                                                                                                                                                                                1. IP
                                                                                                                                                                                                                                  1. MM
                                                                                                                                                                                                                                    1. Mucous membranes
                                                                                                                                                                                                                                      1. Health & Safety concerns
                                                                                                                                                                                                                            2. Distribution
                                                                                                                                                                                                                              1. Rapid after IV
                                                                                                                                                                                                                                1. PPB: 25-30%
                                                                                                                                                                                                                                  1. Accumulation possible - Not as quickly as Thiopental
                                                                                                                                                                                                                                  2. Longer than other Injectables, changes conformation post-injection before crossing BBB
                                                                                                                                                                                                                                  3. Placental transfer
                                                                                                                                                                                                                                  4. Metabolism
                                                                                                                                                                                                                                    1. Liver
                                                                                                                                                                                                                                      1. Enzymatic induction
                                                                                                                                                                                                                                    2. Elimination
                                                                                                                                                                                                                                      1. Kidneys (Urine)
                                                                                                                                                                                                                                        1. Active Metabolite ( Norketamine)
                                                                                                                                                                                                                                      2. CNS
                                                                                                                                                                                                                                        1. NMDA receptor antagonist
                                                                                                                                                                                                                                          1. Nicotinic, muscarinic, opiod, monoaminergic receptors
                                                                                                                                                                                                                                            1. Anti-hyperalgesic properties
                                                                                                                                                                                                                                              1. Reduces MAC
                                                                                                                                                                                                                                            2. Unconsciousness
                                                                                                                                                                                                                                              1. Dissociative Anaesthesia
                                                                                                                                                                                                                                                1. Should NEVER be given on it's own (+ Sedative)
                                                                                                                                                                                                                                              2. Cranial nerve reflexes maintained
                                                                                                                                                                                                                                              3. Uses
                                                                                                                                                                                                                                                1. Chronic pain
                                                                                                                                                                                                                                                  1. Horses: (after alpha 2 agonist)
                                                                                                                                                                                                                                                    1. Induction
                                                                                                                                                                                                                                                      1. Top-up/ Maintenance
                                                                                                                                                                                                                                                    2. Cats & Dogs: Combined with ACP, alpha 2 agonists, opiods, benziadiazepines
                                                                                                                                                                                                                                                      1. Cattle, sheep, pigs
                                                                                                                                                                                                                                                        1. Small mammals, birds & exotics
                                                                                                                                                                                                                                                    3. CVS
                                                                                                                                                                                                                                                      1. Increased sympathetic tone
                                                                                                                                                                                                                                                        1. Increased HR & Contractility
                                                                                                                                                                                                                                                          1. Increased CO & ABP
                                                                                                                                                                                                                                                            1. Increased mVO2
                                                                                                                                                                                                                                                        2. Direct -ve Inotropic Effect
                                                                                                                                                                                                                                                        3. Resp.
                                                                                                                                                                                                                                                          1. Laryngeal & Pharangeal reflexes maintained
                                                                                                                                                                                                                                                            1. Transient resp. depression
                                                                                                                                                                                                                                                              1. Apneustic pattern
                                                                                                                                                                                                                                                                1. Bronchodilation
                                                                                                                                                                                                                                                            2. Side Effects
                                                                                                                                                                                                                                                              1. Increased ICP, CMRO2, IOP & Mydriasis
                                                                                                                                                                                                                                                                1. Seizures possible
                                                                                                                                                                                                                                                                  1. Increased Salivation
                                                                                                                                                                                                                                                                    1. Muscle rigidity & spontaneous muscle movements common
                                                                                                                                                                                                                                                                  2. Dissociative Anaesthesia
                                                                                                                                                                                                                                                                    1. Maintains reflexes
                                                                                                                                                                                                                                                                      1. Analgesia
                                                                                                                                                                                                                                                                    2. Steroids
                                                                                                                                                                                                                                                                      1. Alphaxalone
                                                                                                                                                                                                                                                                        1. + Alphadalone (Saffan)
                                                                                                                                                                                                                                                                          1. Weak anaesthetic
                                                                                                                                                                                                                                                                            1. Increases solubility of Alphaxalone
                                                                                                                                                                                                                                                                            2. Small mammals & birds
                                                                                                                                                                                                                                                                              1. GABAa receptor binding
                                                                                                                                                                                                                                                                                1. Absorption
                                                                                                                                                                                                                                                                                  1. Viscous solution
                                                                                                                                                                                                                                                                                    1. Cremophor EL
                                                                                                                                                                                                                                                                                      1. Causes Histamine release
                                                                                                                                                                                                                                                                                        1. Do NOT use in Dogs
                                                                                                                                                                                                                                                                                          1. Potentially fatal Anaphylactoid Rxn
                                                                                                                                                                                                                                                                                            1. Oedema & flushing of paws
                                                                                                                                                                                                                                                                                              1. Tx w/ antihistamines, corticosteroids
                                                                                                                                                                                                                                                                                    2. IV & IM
                                                                                                                                                                                                                                                                                      1. Non-irritant
                                                                                                                                                                                                                                                                                        1. Can be topped-up
                                                                                                                                                                                                                                                                                          1. TIVA
                                                                                                                                                                                                                                                                                        2. No bacteriostatic agent
                                                                                                                                                                                                                                                                                          1. Preceiptates (refridgerated)
                                                                                                                                                                                                                                                                                        3. Distribution
                                                                                                                                                                                                                                                                                          1. Rapid Onset (IV): 5-20 min
                                                                                                                                                                                                                                                                                            1. Lower doses: Sedation (IM)
                                                                                                                                                                                                                                                                                              1. PPB: < 50%
                                                                                                                                                                                                                                                                                                1. Top-up (IV): Induction
                                                                                                                                                                                                                                                                                            2. Metabolism
                                                                                                                                                                                                                                                                                              1. Liver
                                                                                                                                                                                                                                                                                              2. High therapeutic index
                                                                                                                                                                                                                                                                                                1. CVS
                                                                                                                                                                                                                                                                                                  1. Transient Hypotension
                                                                                                                                                                                                                                                                                                  2. Resp.
                                                                                                                                                                                                                                                                                                    1. Resp. depression (Dose dependent)
                                                                                                                                                                                                                                                                                                    2. CNS
                                                                                                                                                                                                                                                                                                      1. Muscle relaxation
                                                                                                                                                                                                                                                                                                        1. Twitching (Recovery)
                                                                                                                                                                                                                                                                                                    3. Potent anaesthetic
                                                                                                                                                                                                                                                                                                      1. No cremaphor
                                                                                                                                                                                                                                                                                                        1. No Histamine release
                                                                                                                                                                                                                                                                                                        2. Not irritant if extravascular
                                                                                                                                                                                                                                                                                                          1. IM, CRI
                                                                                                                                                                                                                                                                                                            1. Licensed for Dog & Cat
                                                                                                                                                                                                                                                                                                              1. Premeds Imp.
                                                                                                                                                                                                                                                                                                                1. Very expensive
                                                                                                                                                                                                                                                                                                                2. Progesterone derivatives
                                                                                                                                                                                                                                                                                                                  1. Etomidine
                                                                                                                                                                                                                                                                                                                    1. GABAa receptors
                                                                                                                                                                                                                                                                                                                      1. Absorption
                                                                                                                                                                                                                                                                                                                        1. Propylene glycol + H2O mixture
                                                                                                                                                                                                                                                                                                                          1. Soybean oil, glycerol egg
                                                                                                                                                                                                                                                                                                                        2. Distribution
                                                                                                                                                                                                                                                                                                                          1. PPB: 75%
                                                                                                                                                                                                                                                                                                                            1. Rapid Onset
                                                                                                                                                                                                                                                                                                                          2. Metabloism
                                                                                                                                                                                                                                                                                                                            1. No accumulation
                                                                                                                                                                                                                                                                                                                              1. Hepatic & Plasmatic esterases
                                                                                                                                                                                                                                                                                                                                1. Inactive metabolites
                                                                                                                                                                                                                                                                                                                          3. Etomidate
                                                                                                                                                                                                                                                                                                                            1. Not licensed in animals
                                                                                                                                                                                                                                                                                                                              1. Expensive
                                                                                                                                                                                                                                                                                                                                1. Minimal cardiovascular effects
                                                                                                                                                                                                                                                                                                                                  1. Suitable for animals w/ CV problems
                                                                                                                                                                                                                                                                                                                                    1. Minimal effect on ICP, CPP, CBF
                                                                                                                                                                                                                                                                                                                                      1. Minimal Resp. depression
                                                                                                                                                                                                                                                                                                                                    2. Inhibition of Cortisol synthesis
                                                                                                                                                                                                                                                                                                                              2. Inhalation
                                                                                                                                                                                                                                                                                                                                1. More action on spinal cord
                                                                                                                                                                                                                                                                                                                                  1. Rapid recovery after hrs of maintenance
                                                                                                                                                                                                                                                                                                                                    1. No (or little) metabolism of drugs
                                                                                                                                                                                                                                                                                                                                      1. More equipment needed
                                                                                                                                                                                                                                                                                                                                        1. Need to scavenge
                                                                                                                                                                                                                                                                                                                                        Mostrar resumen completo Ocultar resumen completo

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