Anesthesia Flashcards
3 different types of anesthesia and the body part it covers
- general: insensibility to the whole body + LOC (centrally acting drugs)
- regional: administered specific spinal cord/nerve root level (region of body), still conscious
- local: administered directly to the target tissue, still conscious
ASA (American Society of Anesthesia) 1-6
ASA 1: healthy
ASA 2: mild systemic disease, no functional limits
ASA 3: moderate systemic disease, some functional limits
ASA 4: severe systemic disease, incapacitating
ASA 5: moribund, will not live 24 hrs without immediate surgery
ASA 6: brain dead, suitable for organ harvest
3 areas covered by anesthesia and their definitions
- analgesia: pain relief without LOC
- hypnosis: loss of physical awareness +/- LOC
- relaxation: decreased muscle tone
4 main medication types used in anesthesia and which area they cover
- local/regional anesthesia: analgesia (MAIN) + relaxation
- opioids: analgesia (MAIN) + hypnosis
- general anesthesia: hypnosis (MAIN) + relaxation + analgesia (least)
- muscle relaxants: just relaxation
why is analgesia still needed in an unconscious patient?
because noxious stimuli causes autonomic reflexes like tachycardia and HTN –> might wake up
an example of RA/LA
lidocaine
different types of opioids (divided into strong and weak, short and long acting)
strong:
- short-acting (intraoperative): remifentanil, fentanyl
- long acting (intra + postop): morphine, oxycodone
weak: codeine, dihydrocodeine, tramadol
what are some of the issues of LA/RA?
- CVS: vasodilation
2. cerebral: sympathectomy (sweating, flushing), neurological sequelae
what is the mechanism of action of LA/RA?
blocks Na+ channels –> hyperpolarization –> decreased AP –> CVS and cerebral effects
what is one benefit LA/RA has over GA in term of side effects
respiratory depression spared
what are the modes of LA/RA administration? In which of these can opioids be added to enhance pain management?
- USS guided
- spinal/epidural +/- opioids
- intrathecal +/- opioids
- wound catheters
- nerve plexus catheters
- topical (patches)
modes of administration of GA (2). What are some of the differences between the two?
- inhalation agents: slower onset/recovery (washout slower), depends on partial pressure gradient and therefore high doses needed (lungs>blood>brain)
- most adults
- dissolves in lipid cell membrane –> direct physical effect on surface receptors
- slow metabolism (what goes in comes out)
- flexible duration (just keep inhaling as needed)
- Intravenous agents: fast onset/recovery
- most children
- quickly distributes into the tissues and dissolves into lipid membrane (depends on perfusion, although highest affinity for lipids doesn’t go to fat due to low perfusion)
- targets Cl - channels –> hyperpolarization
- wait for excretion by body
what are the medications used with each mode of GA?
- inhalation: halogenated hydrocarbons (desflurane, sevoflurane, isoflurane)
- IV: propofol (MAIN, fast), thiopental sodium (slow), etomidate, ketamine (children)
issues with GA (3) and their management
- respiratory:
- decreased hypoxic/hypercarbic drive
- decreased residual capacity and tidal volume –> V/Q mismatch –> increased RR
- paralyzed cilia
solution: O2 + ventilation
- CVS:
- direct (negative inotropic effect on heart –> decreased CO, decreased vascular tone –> vasodilation)
- indirect (vaso/venodilation –> decreased SV, CO, and peripheral resistance)
- pressure injury: positioning + gel padding
indications for using muscle relaxant (3)
- intubation/ventilation
- when accessing body cavity for surgery
- when immobility is required (neuro/microsurgery)
issues with muscle relaxant (3)
- awareness
- incomplete reversal –> airway obstruction
- apnoea
what are the 3 different types of surgery in the context of pre-op assessment and optimization?
- elective planned surgery (months): assessment (6-8 weeks before surgery by anesthetists) + optimization (GP)
- urgent surgery (weeks): assessment + little optimization
- emergency surgery: only assessment
what extra things must be done intra + post op for emergency surgery patients?
intraoperative: beat by beat invasive monitoring
postop: critical care
what is rapid sequence induction (RSI) and when is it needed?
a way of achieving airway control while minimizing aspiration risks
- used in those with reflux or not NBM (emergency)
what are some of the things to look for in anesthetic preop assessment?
- comorbidities, exercise/stress tolerance, identify unknown conditions, FH, etc.
- drug history, allergies, previous addiction
- previous surgery, anesthesia complications
- risks: respi/airway issues, spine deformities, obesity, reflux disease/hasn’t fasted
cardiac risk index (used with ASA) - 6
a point for each, >= 2 means high risk
- high surgical grade
- congestive heart failure
- ischemic heart disease
- cerebrovascular disease
- DM
- renal failure
metabolic equivalent score (MET) (8) - measure of exercise tolerance, with MET2-4 = more morbidity and MET5-9 is less
can do the following without getting breathless: MET2: walk around the house MET3: light housework MET4: walk 100-200 meters MET5: walk up hill or up the stairs MET6: walk briskly on flat ground MET7: light exercise MET8: run a short distance MET9: strenuous exercise
what is cardiopulmonary exercise testing and why is it quickly becoming a GOLD standard for pre-op anesthesia assessment?
OBJECTIVE measure of ECG, O2 consumption, bp –> correlates with post-op morbidity
- all the other scores are subjective
what are some of the lifestyle risks in pre-op assessment? What are the effects of each of these? (3)
- smoking: septic complications and decreased wound healing
- alcohol: septic complications
- obesity: poorer outcomes
what is the best pre-op optimization method and why?
exercise (GOLD standard) - increases the anaerobic threshold –> improved outcomes by 15% per met
what are some medications that SHOULD be continued despite NIB?
inhalers, antianginals, antiepileptics
what are some medications that can be considered stopping before anesthesia?
anticoagulants (warfarin), DM meds
- if prostatic heart valve or CVS symptoms, the consider bridging therapy (replacing warfarin with LMWH)
what are the 5 different stages of administering GA?
- (preparation)
- induction
- maintenance (phase 1)
- monitoring
- emergence (phase 2)
- recovery
- postop care
what are some of the crucial things that happen during the preparation before the induction?
- patient consent + identity check
- IV access
- pre-oxygenation
what are the medications given during the induction for GA?
analgesia (fentanyl, alfentanil) + hypnotics (propofol, thiopentone, ketamine, benzodiazepine) +/- muscle relaxants (preferably avoid)
after induction and before surgery commences, check to make sure these 5 things are in place for monitoring - what do each of these mean?
- 3 lead ECG - arrhythmia
- O2 saturation
- noninvasive bp cuff - (at least every 5 mins) monitor drop in bp from vasodilation (might need vasopressor)
- end tidal CO2 - airway patency + blood gas
- airway pressure monitoring - ventilation quality (separate machine)
what happens during maintenance?
- anticipation of key surgical moments and constant adjustment
- advocate for the unconscious patient
what are the 4 things that anesthetists must document for every surgery?
- prescription record
- observation chart
- ventilation chart
- fluids chart
explain the process of emergence (in the context of patient management)
stopping anesthetics + reversing muscle relaxants if used –> return of spontaneous breathing + airway reflexes –> remove ventilator –> recovery room
- care of delirious patient as needed