Sleep & Anaesthesia Flashcards
What is the circadian rhythm?
- 00 - Midnight
- 00 - Deepest sleep
- 30 - Lowest body temperature
- 00 - Morning
- 45 - Sharpest rise in blood pressure
- 30 - Melatonin secretion stops
- 00 - Highest testosterone secretion
- 00 - Highest alertness
- 00 - Noon
- 30 - Best coordination
- 30 - Fastest reaction time
- 00 - Greatest cardiovascular efficiency + muscle strength
- 00 - Evening
- 30 - Highest blood pressure
- 00 - Highest body temperature
- 00 - Melatonin secretion starts
- 00 - Midnight
The hormone ______ is involved in
melatonin
synchronising circadian rhythm
Clock - A circadian clock
is a 24hour timing mechanism that is composed of molecular oscillators
Circadian rhythm
a biological rhythm with an approx. 24 hr period that persists in constant conditions
Oscillator is
a system of components that interact to produce a rhythm that occurs with a definable period length.
A circadian oscillator can drive a rhythmic output but needs other oscillators (known as pacemakers) for its function.
A circadian oscillator can therefore be self-sustained but cannot operate properly independently of other oscillators.
Circadian pacemaker
is a specialised oscillator that operates independently of other oscillators to drive rhythmic outputs, either directly or through other oscillators, and is entrained by environmental cues.
Entrainment
Process by which an environmental rhythm e.g light-dark cycle, regulates the period and phase relationship of a self-sustained oscillator
Zeitgeber
Any external or environmental cue that synchronises an organism’s biological rhythm to Earth’s 24-hour light/dark cycle and 12 month cycle e.g. light, temperature, exercise
What is the suprachiasmatic nucleus?
A small region of the brain that sits on top of the optic chiasm in the anteroventral region of hypothalamus
SCN is a type of
specialised oscillator - pacemaker
SCN can regulate process such as
locomotor activity
electrical firing
Where may some other oscillators be present?
Heart
Lung
Liver
Kidney
Heart Lung Liver Kidney all may regulate processes such as
heart rate, systolic blood pressure, vasodilation, gene expression, melatonin levels
How is the brain kept awake? What may lead to constant sleep?
the activity of the Ascending Reticular Formation
lesions to this brain area
Melatonin has ______ actions on SCN
inhibitory
EEG stands for __________________. It measures
electroencephalograpgh.
electrical activity produced by the brain (cerebral cortex) and recorded from electrodes placed on scalp.
From highest to lowest frequency, what waves do EEGs detect?
beta
alpha
theta
delta
Which radio wave is present during alert wakefulness?
beta
Which radio wave is present during quiet wakefulness?
alpha
Which radio wave is present during Stage 1 sleep?
low voltage and spindles
Which radio wave is present during Stage 2 and 3 sleep?
Theta waves
Which radio wave is present during Stage 4 slow wave sleep?
Delta
Which radio wave is present during Stage 5 REM sleep?
Beta
Stages and what happens during sleep cycle
Stage 1 - interim between consciousness and sleep
Stage 2 - Heat rate slows, brain does less complicated sleep
Stage 3 - Body makes repairs
Stage 4 - Body temperature and BP decrease
Stage 5 - Increase in eye movement, heart rate, breathing, BP and temperature
The awake stage is characterised by
high frequency activity with variable amplitude, combined with active electromyography (EMG)
The REM stage is characterised by
high frequency activity with high amplitude and no active EMG
The non-REM stage 4 sleep is characterised by
low frequency and high amplitude
Stage 4 occurs during the
first hour of going to sleep
REM has _____ body muscle activity than Stage 4
more
Stage 5/ REM sleep is also known as
paradoxical sleep
What is the most refreshing part of sleep? What occurs during this stage?
REM sleep
- muscle relaxation
- increased heart rate
- dreaming
- deep regular breathing
Prolonged activity of the brain may cause production of a ‘sleep producing substance’
Glucose is the main nutrient of the brain, carried by blood.
The more the brain is active, the more glucose needed.
Surrounding astrocytes supply extra energy in the form of glycogen
Glycogen metabolism increases adenosine level
Adenosine accumulation induces higher delta activity in the next sleep session
If sleep does not take place, accumulation of adenosine causes cognitive and emotional effects seen after sleep deprivation
Sleep regulatory substances seem to be involved in ________ scaling
synaptic
Synaptic scaling is a slow
homeostatic process that occurs over hours/ days; it serves in part to balance/ to scale Hebbian plasticity changes that occur rapidly as a consequence of neuronal activity
During wake period
- synaptic __________
-
- ________ regulation
potentiation
learning
circadian
During sleep period
- synaptic __________
-
- ________ regulation
homeostasis
memory consolidation
circadian regulation
Lesioning the brain can cause
sleep disorders
What are some causes of insomnia? and examples
- Physical e.g pain
- Physiological e.g. noise, caffeinated/ stimulant drinks
- Psychological e.g excitement, stress
- Psychiatric e.g. depression
- Drug induced e.g beta blockers
- Unknown cause
What are three degrees/ types of insomnia?
- Transient: jet-lag, novel environment
- Short-term: occupational stress
- Chronic: psychiatric illness
Hypnotics are
short-to-medium acting (so that they enable the person to fall asleep) but their action is not so long that it presents problems of waking up at the right time
What are the most commonly-used drugs used for the treatment of insomnia?
Benzodiazepine
How do BZs work?
Enhance actions of inhibitory GABA neurotransmitter. This acts on GABA chloride channel
BZs reduce the …….
and increase the ……
but both effects…
time taken to get to sleep
duration of sleep
decline with continued use (tolerance)
Because of their CNS depressant effects, all hypnotics have a tendency to depress
REM sleep.
BZs depress REM ____ than other agents
less
Delta wave (slow, deep) sleep is also reduced by
BZs
Ideal hypnotic is one that
acts long enough to allow the person to get sleep but doesn’t depress REM or delta wave sleep
How does ethanol depress neuronal activity?
disruption to cell membrane
Ethanol acts on GABA receptor which is a _______ _______ modulator. It also acts on ______ receptor which is a negative allosteric modulation. It also works on adenosine reuptake inhibitor
positive allosteric
NMDA
Problems with long acting hypnotics?
- may cause problems with hang over effects
- high doses may increase risk of hang over without prolonging sleep
- withdrawal may induce nightmares (increased REM)
It is generally considered that hypnotic agents should not be used for long periods of time, with the maximum being about _________. An alternative approach is to use the agents _______, as required, so that REM ________, and subsequent rebound _________ REM does not occur.
2 weeks
intermittently
deprivation
increased
Which gland releases melatonin?
Pineal
Normally, AP is generated by opening of VG sodium channels, which allow influx of sodium and thus depolarisation. Local anaesthetics…
block VG sodium channel, prevents depolarisation and thus prevents propagation of AP
Most local anaesthetics are weak ___, with a pKa between 8 and 9, so they are mainly but not completely ionised at physiological pH. What is the pharmacology?
bases uncharged species (B) penetrates nerve sheath and axonal membrane and is then converted into BH+ active form, which then blocks sodium channels
Many local anaesthetics are use dependent…
because the molecules gain access more readily when the channel is open
Local anaesthetics block conduction in which order? This means that _______ and _______ transmission are blocked first
small myelinated non myelinated large myelinated nociceptive sympathetic
What are the four different types of local anaesthetics?
- surface anaesthesia; drug applied directly to surface that is the be anaesthetised e.g cornea
- topical anaesthesia; drug applied to skin in form of cream
- infiltration; drug injected below skin at multiple sites close to area to be anaesthetised. Permits incision/ excision of the anaesthetised tissue
- nerve block; inject local anaesthesia into major nerve bundle. All nerve conduction to or form tissues to nerve block are inhibited
Benefits of epidural anaesthesia instead of spinal anaesthesia, for example during childbirth, is?
the ability to anaesthetise a defined area e.g. pelvic organs without disrupting more distal tissues e.g. legs
The extent of block with spinal anaesthesia depends on site of injection, thus
anaesthesia in lower spine anaesthetises a more limited area than anaesthesia in cervical region (upper spine)
More lipid soluble anaesthetics have a _____ duration of action
greater
Local anaesthetics are only effective when they are
blocking the VG sodium channel. They lose efficacy as the drug diffuses from the channel and away from the site of action. Once the drug has diffused away, the nerve function is fully regained.
Sometimes, local anaesthetics are injected along with _____ in order to limit the _______ of the anaesthetic, and thus extending the __________
adrenaline, vasoconstriction
diffusion
duration of action
Name a epidural anaesthetic
Ropivacaine
Name a surface + infiltration anaesthetic
Lignocaine
General anaesthetics are divided into two distinct classes
with different mechanisms of action and different uses:
- inhalation anaesthetics e.g. gases, vapours
- intravenous anaesthetics
Lipid theory of anaesthesia?
Drugs act by dissolving into and disrupting function of cell membrane
Protein theory of anaesthesia?
anaesthetics act by interacting with proteins within the cell membrane, most notably ion channels and receptor proteins.
Place these intravenous general anaesthetics in order of ultra-short acting, to short acting, to longer acting
Thiopentone
Etomidate
Methohexitone
What is ketamine used for?
NMDA receptor antagonist
- used for induction and to maintain anaesthesia
What is propofol for?
it potentiates GABAa receptor activity
General IV anaesthetic
Doesn’t cause analgesia therefore should be combined with fentanyl to alleviate pain
Anaesthetic practice says to induce anaesthesia with ______ and then maintain with
IV agent
inhalation agent
Balanced anaesthesia has 3 aspects to it:
- Hypnosis (suppression of consciousness)
- Analgesia (suppression of physiological response to stimuli)
- Relaxation (suppression of muscle tone)
Name three inhalation agents
Nitrous oxide
Halothane
Isoflurane
Nitrous oxide is a ____ anaesthetic agent but a very ______ analgesic agent. It cannot be used alone as an analgesic as it will cause ______. Therefore, Entonox is give which is ___% N2O and ___ % ____. It is used in anaesthesia mainly for its ______ properties
weak potent hypoxia 50 50 O2 analgesic
Halothane and Isoflurane are both
potent anaesthetics but poor analgesic agents.
Which out of halothane and isoflurane is more cardiotoxic?
halothane
Which out of halothane and isoflurane causes greater respiratory depression?
Isoflurane
Which out of halothane and isoflurane can be used for children?
halothane
Which out of halothane and isoflurane can cause hepatic dysfunction/ problems?
halothane
Cardiac out must be considered when giving anaesthesia. Why? When there is decreased cardiac output, there is decreased perfusion
of tissues e.g. muscle/ fat therefore need to increase concentration of anaesthetic agent that accumulates in the brain
Recovery from general anaesthetic is due to redistribution of drug away from brain and
back to the lungs for excretion
In obese patients, great distribution of anaesthetic to fat stores therefore _____ recovery time from anaesthesia. This is because there is _______ excreton
longer
slower
What are the stages of anaesthesia?
- Analgesia
- Excitement
- Surgical anaesthesia
- Represents medullary depression
What are the stages of anaesthesia?
- Analgesia
- Excitement
- Surgical anaesthesia
- Represents medullary depression
Patient passes through steps 1-3, but in reverse, during recovery.
What else can be administered along with anaesthetic agents?
- BZ - reduce patient anxiety
What happens during stage 1 of anaesthesia? When can this stage be useful?
Analgesia
Patient conscious but drowsy, reduced response to painful stimuli
Using nitrous oxide during child birth
What happens during stage 2 of anaesthesia?
w
What happens during stage 2 of anaesthesia?
Excitement
This stage occurs because inhibition is lost before consciousness.
May result in euphoria + uncontrolled laughing
What happens during stage 3 of anaesthesia?
Surgical anaesthesia
All reflexes are lost. Respiration is regular and muscle tone is eventually lost.
Loss of thoracic muscle tone may necessitate mechanical ventilation for maintenance of breathing and loss of vasc
