anaesthetics Flashcards
where does general anaesthetic provide sensensibility
whole body
implies loss of consciousness and global lack of awareness
where does regional anaesthetic provide sensensibility
an area or region of the body
Nerve and plexus blocks
where does local anaesthetic provide sensensibility
local relevant area - direct to tissue being anaesthetised
what type of anaesthetics are spinal/ epidurals
regional
what is the triad of anaesthetics
hypnosis
analgesiia
relaxation (skeletal muscle)
what does hypnosis mean
unconscious
what is the aim of pain relief
removal of perception of unpleasant stimulus
what are some problems of balanced anaesthesia
¥ Polypharmacy - Inc chance of drug reactions / allergies
¥ Muscle relaxation - requirement for artificial ventilation, means of airway control
¥ Separation of muscle relaxation & hypnosis – awareness – patients awake from wrong dose yet paralysed so unable to communicate
what are the principles of balanced anaesthesia
¥ Different drugs to do different jobs
¥ Titrate doses separately & therefore more accurately to requirements
¥ Avoid overdosage
Control over individual components of the triad
how are general anaesthetics given
inhaled (maintenance) or IV (induction)
(Inhalational agents dissolve in lipid membranes Direct physical effect
Intravenous agents -allosteric binding e,g. GABA receptors also open chloride channels)
what ion channel is sully targeted in GA and why
chlorine
Hyperpolarise neurones = Less likely to “fire” (suppress excitatory synaptic activity)
after GA what functions are lost first
most complex then primitive lost later
are reflexes spared in GA
yes
what must be managed when the patient is under GA
airway and cardiovascular
what is the name of the pump system that allows accurate infusion to achieve specific blood or brain concentrations of agents using complex pharmacokinetic algorithms
target controlled infusion (TCI)
what is a problem with IV anaesthesia and how is this controlled
can’t measure drug concentration in real time
Use computers to calculate a guess
are IV anaesthesia drugs fat or water soluble
fat - cross membrane quickly
what is the rapid recovery form IV anaesthesia due to
drug leaving the circulation and moving to other parts of the body eg muscle and viscera organs
list some anaesthetics that are given IV
thiopentone
propofol
list some anaesthetics that are inhaled
halogenated hydrocarbons
which organ does the uptake and excretion of inhaled anaesthestics
lung
(concentration gradient - lungs > blood > brain
cross alveolar BM easily
arterial concn equates closely to alveolar partial pressure)
what is the MAC (mean alveolar concentration) a measure of (inhaled anaesthetic)
measure of potency
low number = high potency
(less concentration to produce the same affect)
why are really high doses of inhaled anaesthesia given for induction
gas down the concentration gradient in to the patients blood and finally brain to achieve a high enough partial pressure there to produce unconsciousness
what is the main role of inhalation agents
extension or continuation of anaesthesia
what are the central CVS effects of GA
depress cardiovascular centre
reduce sympathetic outflow
negative inotropic/chronotropic effect on heart
reduced vasoconstrictor tone → vasodilation
what do anaesthetics do to respiratory system
depress
Reduce hypoxic and hypercarbic drive
Decreased tidal volume & increase rate
paralyse cilia
what is the exception to all anaesthetics being CVS depressant
ketamine
why does CO fall under anaesthesia
vasodilation reduces venous return to the heart
what are the differences between anaesthetic and opiate respiratory depression
opiate - preserves tidal volume, low respiratory rate
anaesthetic - reduced tidal volume, high respiratory rate
why do some post op patients need anaesthetics for several days
greatly reduced lung volume can interfere with ventilation/ perfusion matching
what are indications for muscle relaxants
ventilation & Intubation
when immobility is essential - microscopic surgery, neurosurgery
body cavity surgery (access)
list some problems with muscle relaxants
awareness
incomplete reversal → airway obstruction, ventilatory insufficiency in immediate post op period
apnoea = dependence on airway & ventilatory support
why is anaesthetic given intra-operatively
Prevention of arousal (pain)
Opiates contribute to hypnotic effect of GA
Suppression of reflex responses to painful stimuli (hypertension, tachycardia)
which system is relatively spared in regional anaesthetic compared to general
respiratory
what are the 7 steps in the process of anaesthesia
pre-opeartive assessment preparation induction maintenace (monitoring) emergence recovery post operative assessment
what is the time of onset for IV induction of anaesthetic
one arm brain circulation - 20s
do you remain conscious with local and regional anaesthetics
yes
CVS derangement proportional to size of area
what is a limiting factor for use of local anaesthetic
toxicity
why is toxicity a risk factor in local anaesthetics
absorption > rate of metabolism = high plasma levels
what things does the toxicity of LA depend on
dose used
rate of absorption (site dependant - perfusion)
patient weight
drug ( bupivacaine > lignocaine > prilocaine )
list some signs and symptoms of local anaesthetic toxicity
Circumoral and lingual numbness and tingling Light-headedness Tinnitus, visual disturbances Muscular twitching Drowsiness Cardiovascular depression Convulsions Coma Cardiorespiratory arrest
why are some areas easier to block with LA than others (differential block)
different nerve fibre types - thickness and myelination
what makes pain fibres easier to block with LA than motor fibres
thinner and less myelinated
during anaesthesia what is a cough depednent on
abdominal muscles (expiratory function)
during anaesthesia which is more spared, inspiration or expiration
inspiration (instercostaals and accessory muscles higher root nerves)
list some considerations in the pre-operative preparation of GA
Planning - checklist - Right patient, right operation
Right (or left) side
Pre-medication (sedatives/ analgesia)
Right equipment, right personnel Drugs drawn up
IV access - Monitoring
what agents may be used for the IV induction of anaesthesia
Propofol - standard, less hangover, quick, less side effects
thiopentone - barbiturate, maternity hospital
why do you need good airway control in GA
apnoea very common
what drug may be used for the gaseous induction of anaesthesia
sevoflurane
in what patients is gaseous induction of anaesthesia better than gaseous
younger children
IV drug users
what is the triple airway manoeuvre in airway maintenance
head tilt, chin lift, jaw thrust
what manoeuvre can solve an airway obstruction but to loss on tone from the tongue
jaw thrust
what is the minimum monitoring in anaesthetics
SpO2, ECG, NIBP, FiO2, ETCO2
temperature, urine output
what is a common post operative side effect of anaesthesia
nausea and vomitting
what are different planes of anaesthesia
analgesia
excitation
anaesthesia
overdose
list some different methods of airway management
Oropharyngeal airway (Guedel) Laryngeal mask endotracheal intubation
which patents can tolerate a Oropharyngeal airway (Guedel
unconscious
what is a laryngeal mask airway
Cuffed tube with ‘mask’ sitting over glottis
Maintains, but does not protect the airway
what reflex must be abolished before endotracheal intubation
laryngeal
what is the most common airway complication
Ineffective Triple Airway Manoeuvre
list some complications of airway management
Ineffective Triple Airway Manoeuvre
Airway device malposition or kinking
laryngospasm
aspiration - gastric contents, blood, surgical debris
what is the only thing that protects the airway from contamination
cuffed tube in the trachea
list reasons for intubating
Protect airway from gastric contents
Need for muscle relaxation artificial ventilation
Shared airway with risk of blood contamination- e.g. tonsillectomy in ENT
Need for tight control of blood gases
Restricted access to airway - e.g. Maxillo-facial surgery
what are anaesthetic risks to an unconscious patient
“Airway, Airway, Airway” Temperature Loss of other protective reflexes - eg corneal, joint position (dislocate shoulder) Venous thromboembolism risk Consent & Identification Pressure areas
what are the main complications of anaesthesia
airway, breathing, circulation
related to techniques. position
awareness
what are some of the anaesthetists roles pre-op
Assess patient as whole for procedure Identify high risk - high morbidity and mortality Optimise patients to minimise risk Inform and support patients decisions Consent from patient
should you continue a patients medications before an operation
mostly
especially Inhalers, Anti-anginals, Anti-epileptics,
Most cardio/ respiratory medications
what medications should be discontinued before an operation
anti-diabetic medication
anticoagulants (if safe to stop)
what is the point in an anaesthetists pre-op assessment
Reduces;
Anxiety
Delays Cancellations (resources)
Complications Length of stay Mortality (well planned)
what things may be asked in the history for an anaesthetist’s pre-op assessment
Known co-morbidities (Severity, Control)
Unknown co-morbidities - (Systemic enquiry, Clinical examination)
Ability of withstand stress - Exercise tolerance, Reason for limitation, Cardio-respiratory disease focus
Drugs and allergies - DDIs
Previous surgery and anaesthesia reaction
describe the ASA grading of surgical patients
ASA1 - Otherwise healthy patient
ASA2 -Mild to moderate systemic disturbance
ASA3 - Severe systemic disturbance
ASA4 - Life threatening disease
ASA5 - Moribund patient (ASA6 Organ retrieval)
list some risk assessment tools for pre-op anaesthesia
GUPTA perioperative cardiac risk
Surgical outcome risk tool American college of surgeons surgical risk calculator
STOP-BANG questionnaire P-POSSUM/ CR-POSSUM/ Q-POSSUM/ V-POSSUM
what things are considered in the cardiac risk index for anaesthesia pre op assessment
High risk surgery Ischaemic heart disease
Congestive heart failure Cerebrovascular disease
Diabetes Renal failure
what is the METS way of measuring exercise tolerance
Without getting breathless -
Walk around the house- 2 METS
Do light housework - 3 METS
Walk 100-200 metres on the flat- 4 METS
Climb a flight of stairs or walk up a hill - 5 METS
Walk on the flat at a brisk pace - 6 METS
Play golf, mountain walk dance, or any form of exercise - 7 METS
Run a short distance - 8 METS
Do either strenuous exercise or heavy physical work - 9 METS
(15% reduction in mortality risk per MET score point)
list some things a patient can do pre-op to improve their outcomes
Optimum medical control - Hypertension, Ischaemic heart disease, Heart failure,Asthma, COPD, Epilepsy, Diabetes
Lifestyle – smoking, alcohol, obesity,
exercise - improve fitness
what are the 0-3 levels of care
0 - primary care
1- Ward-based
2- High dependency unit – single organ support
3- ITU – multi-organ support
where is the only place invasive ventilation can be done
ITU
what is the main difference in the need for HDU and ITU
HDU -single organ support
ITU - multiple organ support
what are the nice guidelines for Na+ fluid replacement
1 – 2mmol/kg/day
what are the nice guidelines for K+ fluid replacement
0.5 – 1mmol/kg/day
what are the nice guidelines for max fluid replacement
25-30ml/kg/day
what are the nice guidelines for glucose replacement
50-100g/day
how would you support GI failure
unblocking any blockages
stenting
TPN with a nasogastric tube.
how would you support renal failure
dialysis
how would you support pancreatic failure
support diabetes, digestive enzyme control
what are the outcomes of liver failure
self limiting
transplant
die
what GCU will be intubated below
8
how would you support brain failure
Ensure the brain is getting O2 and CO2 clearance by vasodilation/ vasopressin, drugs to stop vasospasm, manage raised ICP, sedate, moderate temperature for tissue recovery.
what are the fatality rates of ITU
25-30%
what are benefits of a tracheostomy over a endotracheal tube in ITU
inserted in neck so don’t need sedation of gag reflex
what are the 2 jobs of the lungs
get O2 in
get CO2 out
which respiratory failure is more common in ITU
type 1 (easier to treat - give O2)
what is the most sensitive marker of a deteriorating patient
increasing RR - tachypnoea
what 4 was can oxygen be given in critical care
High-flow nasal cannula. – max 4l a min Facemask – 10L/min CPAP. Intubation and invasive ventilation. ECMO.
what are peoples normal o2 sats
99% on 21% O2
why do people find high flow nasal cannulas uncomfortable
cold dry air blasted up nose
what is the best treatment of type 2 respiratory failure in critical care
invasive ventilation
what does positive pressure from ventilators do to the lungs
ventilators opens lung up so blood can be oxygenated
also cause lung damage so shorten time
why is CO hard to measure
difficult to measure SV
what drugs speed up the heart
chronotropes
what drugs affect the contractility of the heart
inotropes (beta1 agonists)
what drugs affect the pre load or after load of the heart
pre - fluids
after - vasopressors
what type of drugs are vasopressors
alpha-1 agonists - constrict blood vessels (mostly veins) - noradrenaline
give an example of a vasopressor drug
noradrenalien/ adrenaline
alpha-1 agonist
where are central lines most commonly placed and why
R interval jugular vein - goes straight to SVC
what is a benefit of central lines over peripheral cannulas
can be left in for 7-10 days but a cannula only 3 days
what is lactate a marker of
tissue of hypo perfusion (produced in anaerobic metabolism)
>2 abnormal, >4 really bad
what is pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
what is the number 1 disease for years lost to disability worldwide
lower back pain
what are the physical benefits or treating pain
Improved sleep, Better appetite
Better movement Fewer medical complication e.g. heart attack, pneumonia
what are the psychological/social benefits of treating pain
Reduced suffering Less depression, anxiety better family ember able to keep working lower health costs contribute to community
what is the difference between acute and chronic
Acute:Pain of recent onset and probable limited duration
Chronic: Pain lasting for more than 3 months, lasting after normal healing, often with no identifiable cause
Can get acute on chronic (flare up )
what are the 3 most common classifications for pain
acute vs chronic
nociceptive vs neuropathic
cancer (progressive) vs non- cancer
how long does chronic pain last
> 3 months
what is the difference between nociceptive and neuropathic pain
nociceptive - damage to afferent nerves
neuropathic - nervous system damage or abnormality
what type of pain has a physiological protective function
nociceptive
how is nociceptive pain commonly described
Sharp ± dull, Well localised (or visceral)
how is neuropathic pain commonly described
Burning, shooting ± numbness, pins and needles, Not well localised (all over)
give examples of neuropathic pain
nerve trauma diabetic pain (neuropathy), fibromyalgia chronic tension headache (dysfunction) very common after thoracic surgery (intercostal nerves)
what are the pathological mechanisms involved in neuropathic pain
Increased receptor numbers – amplification
Abnormal sensitisation of nerves –Peripheral or Central – ie light touch
Chemical changes in the dorsal horn – neurotransmitters, neuromodulators, noradrenaline, serotonin, Ca
Loss of normal inhibitory modulation
what are the 4 steps of pain physiology
1 peripheral tissue injury
2 travels up spinal cord (spinothalamic)
3 brain - thalamus secondary relay station, pain perception in cortex
4 modulation - descending pathway from brain to dorsal horn to decrease signal
what chemicals do tissues release in response to pain
prostaglandin
substance P
what are pain receptors called
nociceptors
what type of nerves do pain signals travel in
A(delta)
C fibres
what treatments can be given to target the peripheral tissue injury (pain)
RICE (rest, ice, compression, elevation),
NSAIDs
LA (damp down response – C fibres, Aδ
what is the 1st and second relay station for pain
1st - dorsal horn
2nd - thalamus
where do pain fibres cross the spinal cord
at the level they enter
describe the route of the 1st and 2nd nerve in the physiology of pain
1st - tissue to dorsal horn
2nd - opposite side of spinal cord
what treatments can be used to target the spinal cord in pain management
acupuncture, massage, TENS
Local anesthetics, opioids, ketamine
where does pain perception occur
cortex of brain
what is the gate theory of pain
Gate theory of pain - painful signal travels into dorsal horn interneuron can be switched off - this can be stimulated by Abeta nerve and stop pain firing
what treatments target the brain for pain management
paracetamol, opioids, amitriptyline, clonidine, psychological (cognitive behavior therapy)
what is the physiology of modulation of pain
Descending pathway from brain to dorsal horn
Usually decreases pain signal
list 2 classes of simple analgesics
paracetamol
NSAIDs
what are advantages of paracetamol
Cheap, safe, Can be given orally, rectally or intravenously
what are disadvantages of paracetamol
liver failure in overdose
what is the antidote to opiates
naloxone
give examples of mild opiods
codeine
dyhydrocodeine
give examples of strong opiods
Morphine, Oxycodone, Fentanyl
what are advantages of mild opiates
Cheap, safe, Good for mild-moderate acute nociceptive pain,
Best given regularly with paracetamol (synergism)
what are disadvantages of mild opiates
Constipation, Not good for chronic pain
what are advantages of strong opiates
Cheap generally safe Can be given orally, IV, IM, SC Effective if given regularly Got an antidote. Good for Mod-severe acute nociceptive pain (e.g. post-op pain), Chronic cancer pain
what are disadvantages of strong opiates
Constipation Respiratory depression in high dose nausea, addiction (Controlled drug, not good for neuropathic
are opiates good for neuropathic pain
no
what is tramadol
(Mixed opiate and 5HT/NA reuptake inhibitor)
plus inhibitor of serotonin and noradrenaline reuptake (modulation
what are advantages of tramadol
Less respiratory depression, can be used with opioids and simple analgesics, Now a controlled drug
what is amitriptyline
tricyclic antidepressant (TCA
what are advantages of amitriptyline
cheap, safe in low dose, good for neuropathic pain, also treats depression, poor sleep
what are disadvantages of amitriptyline
Anti-cholinergic side effects (e.g. glaucoma, urinary retention)
what anticonvuslantsa re used for pain manangemtn
gabapentin (Neurontin)
sodium valproate (epilim)
carbamazepine (tegretol)
membrane stabilisers – reduce abnormal firing of nerves (Good for neuropathic pain)
what is ketamine
NMDA Receptor antagonist
how may LA be administered
Epidural
Intrathecal
Wound Catheters Local Infiltration of wounds
Nerve Plexus Catheters (brachial/ femoral/ sciatic)
name a topical agent used to manage neuropathic pain
capsaicin
list ways to assess pain
Verbal rating score – no, mild, moderate, severe, excruciating
Numerical rating score – 0-10 – most people don’t like numbers, hard to interpret
Visual analogue scale – line with scale
Smiling faces – paediatric
Abbey pain scale - confused patients, looks at pain and patient behaviour
list some non-drug methods of managing pain
Physical - Rest, ice, compression, elevation
Surgery
Acupuncture, massage, physiotherapy
Psychological- Explanation – expected, Reassurance
Counselling – positive psychology
where on the WHO pain ladder do you start with mild pain
Start at Bottom of Pain Ladder
where on the WHO pain ladder do you start with moderate pain
Bottom of Pain Ladder plus Middle Rung
where on the WHO pain ladder do you start with severe pain
Bottom of Pain Ladder plus Top of Ladder.
Miss out the middle
is it ok to start at the top of the WHO pain ladder
severe/ unbearable pain
would you stop NSAIDs or paracetamol first
NSAIDs as more adverse effects
what type of pain is the WHO ladder for
nociceptive NOT neuropathic
what is step 1 of the WHO pain ladder
aspirin, NSAIDs, paracetamol
what is step 2of the WHO pain ladder
mild opiods eg codeine
what is step 3 of the WHO pain ladder
strong opiods e.g. morpheine
what does the RAT assessment stand for
R - recognise
A- assess
T - treat
what drugs should be used for neuropathic pain
Amitriptylline, Gabapentin, Duloxetine
what is involved is the ‘Recognise’ of RAT assessment
Does the patient have pain? Ask, Look (frowning, moving easily, sweating)
Do other people know the patient has pain? Other health workers, Patient’s family
what is involved is the ‘Assess’ of RAT assessment
Severity - pain score at rest and with movement, how is pain affecting the patient? Can they move, cough, work
Type – acute, chronic, cancer, non-cancer, nociceptive, neuropathic (burning/ shooting, phantom limb, pins and needles, numbness)
Other factors – other illnesses (physical), lack of social support, home circumstances, work (social), anger, anxiety, depression (psychological)
how should you treat moderate nociceptive pain
Paracetamol (± NSAIDs)
how should you treat mild nociceptive pain
Paracetamol (± NSAIDs) + codeine/ alternative
how should you treat severe nociceptive pain
Paracetamol (± NSAIDs) + morphine
what should you always remember to do when treating your patient for pain
Reassess the patient: Is your treatment working?
Are other treatments needed? Up or down pain ladder
