sleep

Nota:

• a natural periodic state of rest for the mind and the body, in which the eyes usually close and consciousness is completely or partially lost, so there is  decrease in bodily movement and responsiveness to external stimuli

1. sleeping patterns vary amongst people
   1. we spend about a 1/3 of our lives sleeping
2. What happens when someone is sleep deprived?
   1. grumpiness
   2. grogginess
   3. irratability
   4. forgetfullness
   5. language, memory, planing and sense of time - severely affected
3. How to measure sleep?
   1. questionnaire

      Nota:

      • results can be limiting! increased error due to BIAS
   2. physiological measurements

      Nota:

      • results are limited by methods used, mostly free from bias and are reproducible
      1. Neurochemial
         1. normally via blood samples
      2. neurophysiological
         1. electroencephalography (EEG)

            Nota:

            • involves the recording of a gross average of electrical potentials of the cells and fibres in the brain areas closed to each electrode attached to the scalp
            1. an EEG shows the electrical activity of a particular brain region relative to another, usually one region being higher then the other
               1. increased activity is displayed as larger amplitude, or bigger peaks, than the baseline recording
4. Stages of sleep
   1. stage 1 non-REM sleep: awake and relaxed

      Nota:

      • dominated by irregular, jagged, low voltage waves brain activity is still high but will start to decline
      1. stage 2 non-REM sleep

         Nota:

         • contains: -sleep spindles: 12-14Hz bursts for at least 500msec - generated by oscillating interactions between cells in thalamus and the cortex -K-complex: sharp high-amplitude positive wave followed by a smaller slow negative wave - occur randomly and in response to auditory stimuli
         1. stage 3 non-REM sleep

            Nota:

            • Delta waves: slow, large amplitude waves neural activity is highly synchronised
            1. stage 4 non-REM sleep

               Nota:

               • increased delta wave activity stages 3 and 4 are known as alow-wave-sleep (SWS) sleepwalking, nightmares, bedwetting can occur at this stage of sleep
               1. (rapid eye movement) REM sleep

                  Nota:

                  • irregular, low voltage, fast waves similar to those in stage 1 of non-REM sleep increased brain activity may be associated with a state of dreaming
                  1. physiological changes
                     1. postural muscles become more relaxed - deep REM sleep
                     2. HR, BP, breathing rate are all much more variable than in other stages of sleep
                     3. increased blood supply to reproductive organs
   2. sleep cycle lasts approx 60-90 mins
5. physiological changes during sleep
   1. cardiovascular
      1. NREM sleep
         1. reduction in heart rate, CO, BP
      2. REM sleep
         1. HR and BP increase, vasoconstriction in skeletal muscle
   2. respiratory system
      1. NREM sleep
         1. slight hypoventilation, PCO2 levels rise, PO2 levels decrease
         2. decrease in firing of inspiratory neurons, breathing is under chemical and mechanical control (no active mechanism present)
      2. REM sleep
         1. higher and variable respiratory rate, lower tidal volume, probably driven by higher cortical control
         2. increase of resistance in upper airway due to loss of muscle tone during REM sleep
      3. sleep apnea

         Nota:

         • lack of breathing during sleep for at least 10 seconds -older patients or infants -in adults associated with daytime sleepiness and snoring -sudden infant death syndromme (SIDS) -most death occur in the morning when SIDS babies have increased REM sleep -increased incidence odSIDS in younger mothers, low birthweight, paternal cocaine use -placing babies on backs when sleeping reducesSIDS
   3. renal system
      1. decreased urine production, increased conc
      2. decrease in GFR and renal plasma flow
      3. secretion of aldosterone and ADH increase
   4. GI
      1. decreased motility
      2. decreased gastric acid secretion
      3. swallowing reflex slows down
   5. nervous system
      1. overall reduced discharge rate and metabolism during NREM sleep
      2. the increase/decrease in neuronal activity is very much dependent on the brain region
6. Insomnia

   Nota:

   • the inability to sleep
   1. chronic insomnia

      Nota:

      • lasting for weeks, months or years
   2. transient insomnia

      Nota:

      • short lived, lasting for only a few nights or weeks, usually resulting from a stressful event
   3. 1st line: non drug treatments
      1. change in the environment

         Nota:

         • bed, light etc
      2. change in lifestyle

         Nota:

         • exercise, establish a routine
      3. avoiding stimulants eg caffeine
   4. drug treatments
      1. benzodiazepines

         Nota:

         • act allosterically to increase affinity of GABA for its receptors -increase chloride conductance
         1. decrease the time taken to get to sleep and increase the duration of sleep
         2. reduce REM sleep
         3. next day residual effects: headache, nausea, 'hangover syndrome', psychomotor impairment
      2. sedative antihistamines
      3. z-drugs
         1. zaleplon

            Nota:

            • t1/2 = 1 hour for patients who have difficulty falling asleep. severe case
         2. zolpidem

            Nota:

            • t1/2 = 2.5 hours for short term treatment in patients where insomnia is debilitating or is causing severe distress treatment <4 weeks
         3. zopiclone

            Nota:

            • t1/2 = 3.5-6.5hours for patients suffering from severe sleep disruption doses should be as low as possible and treatment should not last longer then 4 weeks