anaesthesia Flashcards
What are drugs available for sedation?
Alcohol (disinhibition, nausea, slow recovery)
Tetrahydrocannabinol (nausea, illegal)
Opiates (euphoria, nausea, resp depression)
Major tranquillisers (profound anxiety, hypotension)- CHLORPROMAZINE, HALOPERIDOL
Minor tranquillisers (drowsiness, prolonged effect)- BENZODIAZEPINE
What are benzodiazepines?
ORAL
Long interval, variable, small effect
IV
Cannulation, limited duration of action, need for monitoring, written record
MECHANISM OF ACTION
Bind to GABA receptor at allosteric sites
Increases frequency of opening of Cl channel
Membrane hyperpolarisation
CNS depression
What are examples of benzodiazepines?
Diazepam- irritant, skin necrosis
Midazolam- slow onset, less predictable, rapid metabolism
Diazemul- rapid onset, brief action, psychoactive metabolites w long half life
Prop
What is propofol?
Short acting
Fast recovery
In subanaesthetic doses
No analgesia
Continuous infusion
Expensive delivery system
Vasodilation
Painful on injection
Rapid pleasant onset
What is unconsiousness?
Unrousability
Loss of protective reflexes (aspiration, obstruction and nerve damage potential)
What is the process of GA?
1. INDUCTION
IV or gaseous/volatile
2. SECURE AIRWAY
Optimum head position, LMA, ETT
3. MAINTENANCE
IV or gaseous/volatile
Analgesia
Muscle relaxant
4. EMERGENCE
Reversal of muscle relaxant
What are induction drugs?
IV
Propofol, thiopentone, ketamine, etomidate
VOLATILE
Sevoflurane
What is thiopentone?
Rapid onset
Offset due to redistribution
Slow metabolism
Cumulative
Hypotension
Odd complications (arterial spasm, porphyria, anaphylaxis rare)
What is ketamine?
Rapid onset
Hypertension
Powerful analgesic
Muscle rigidity
Unpleasant hallucinations
What is etomidate?
Cardiovascular stability
Odd complication- inhibition of steroid synthesis, death due to induced Addisons
What are examples of muscle relaxants?
Overcomes laryngeal reflexes
Atracurium
Rocuronium
Suxamethonium
Etc
All come w side effects such as, histamine release, prolonged paralysis, tachycardia, hypotension
What are maintenance drugs?
GASEOUS/VOLATILE
Nitrous oxide
Isoflurane, sevoflurane, desflurane
IV
Propofol
What are complications during an operation?
PATIENT
Preexisting disease (cardiac, resp, diabetes)
ANAESTHESIA
Awareness, overdose, anaphylaxis, hypoxia, resp depression, aspiration, peripheral nerve damage
SURGEON
Haemorrhage
How do you do an anaesthetic history?
Proposed procedure
Past med history
-drugs/allergies
-previous GA, problems, family
-medical (cardiac IHD, valvular, other, resp obstructive/restrictive, GI aspiration risk [Hiatus Hernia], renal impairment, diabetes)
Airway assessment
What are signs of haemorrhage?
Falling BP
Rising HR
Suction container full of blood
Loads of wet swabs being piled in a corner
How do you treat haemorrhage?
Permissive loss of Hb (~80)
Restore circulation w crystalloid
Chloride anion
Is a drop in BP expected?
Propofol reduces arterial blood pressure without affecting HR
BP expected to rise shortly after w/o intervention
If not- administer IV fluids/other
