Previous Notes Flashcards
How to differentiate between ASA 1-6
ASA 1: normal, healthy, non smoker
ASA 2: controlled systemic disease, no functional limitation (ie controlled HTN/DM, pregnant, smoker)
ASA 3: severe systemic disease w/ functional limitation (morbid obesity, ESRD on HD)
ASA 4: severe disease that is constant threat to life (ESRD but not on routine HD, recent <3mo TIA/MI, HFrEF, valve dysfunction)
ASA 5: moribund, not expected to survive without OR (ie massive trauma, ICH w mass effect, ruptured AAA)
ASA 6: brain dead, organ retrieval
Do we continue or stop these meds prior to surgery:
- ACEi/ARB
- Diuretic
- alpha 2 agonist
- ACEi/ARB: STOP - due to risk of refractory hypotension, need vasopressin or norepi
- Diuretic: STOP - due to risk of hypokalemia from loop diuretics and hypovolemia
- Alpha 2 agonist: CONTINUE - risk of rebound HTN
Do we continue or stop these meds prior to surgery:
- Metformin
- MAOi (selegiline)
- TCA (nortriptyline)
- Betablockers
- Metformin: CONTINUE in healthy patients
STOP in renal disease or surgeries affecting renal fx due to risk of metformin induced metabolic acidosis - MAOi (selegiline): CONTINUE - risk of pre-op HTN, but be wary and avoid meperidine (5HT reuptake inhibit) due to risk of Serotonin Syndrome and avoid sympathomimetics ie ephedrine and phenylephrine risk of hypertensive crisis
- TCA (nortriptyline): CONTINUE - check ECG in pre-op for prolonged QT and wide QRS due to sodium channel blockade
- Beta blockers: CONTINUE - risk of rebound HTN
Perioperative risks of morbid obesity and #1 cause of mortality in obese patients
risk of airway obstruction (hypercarbia), reduced wound healing/infection, hyperglycemia
DVT > PE is #1 cause of mortality in obese patients
What anatomy pertains to nausea?
Medication effects on areas?
Area postema: medulla, controls vomiting and opioids act in this area to trigger nausea
Nucleus tractus solitarii: dexamethasone acts on this
chemoreceptor trigger zone: near base of 4th ventricle which involve receptors of 5-HT, dopamine, and opioid (IE ondasetron)
What are MOA of ondasetron and aprepitant? side effects?
ondansetron: 5HT antagonist at chemoreceptor trigger zone
SFX: prolonged QT > headache > transaminitis > dystonia > cardiac event
aprepitant: NK1 receptor antagonist
SFX: malaise, rash, nausea
What are MOA of scopalamine and droperidol? side effects?
Scopalamine: antimuscarinic
SFX: dry mouth, tachycardia, blurry vision, urinary retention, constipation
(Tx anticholinergic crisis with physostigmine)
Droperidol: CNS antidopaminergic
SFX: extrapyramidal symptoms, dystonic rxn, prolonged QT
Mechanism of metoclopramide, uses?
Central: antidopaminergic
Peripheral: cholinergic agonist
- Increases lower esoph sphicter tone
- Use for enhanced GI motility
- PONV dose must be 25-50mg, otherwise ineffective at PONV for primary or secondary agent
Aspiration ppx regimen, who is at higher risk?
- Metoclopramide (antidopamine)
- Ranitidine (H2 antagonist, longer acting and less sfx than cimetidine)
- Na bicarbonate in pregnancy
High risk: pregnancy, delirium, severe DM (delayed gastric empty), hiatal hernia, morbid obesity, scleroderma, emergent surgery
What decreases lower esophageal sphincter tone? What increases it?
Lowers: pregnancy, obesity, inhaled anesthetics, opioid, propofol
Increases: succinylcholine, metoclopramide
Where will aspirated material usually end up in Supine patient
Posterior segment of right lower lobe
Anterior vs posterior ischemic optic neuropathy risk factors and presentation
Painless loss of vision, sluggish pupils
Anterior- risk after cardiac surgery
Posterior- risk after spine surgery
Vascular rf - prone, cad, dm, smoking, spine fusion, htn
Phase 1 vs phase 2 hypothermia
Phase 1: 1st hr anesthesia, heat loss from drug induced redistribution usually 1-2 degrees
Phase 2: heat loss due to radiation»_space; conduction, convection, evaporation
Describe neonates thermogenesis
Nonshivering thermogenesis from brown fat and skeletal muscle triggered by norepi, corticosteroids, and thyroxine
Drugs eliminated by RBC esterases
Remifentanil
Esmolol
Clevidipine
Drugs eliminated by pseudocholinesterase (aka plasma cholinesterase)
- Succinylcholine
- Ester-type LA (1× i), procaine, benzocaine, tetracaine
- Mivacurium
(Amide-type LA is two i’s, Lidocaine, bupivicaine, ropivicaine)
CYP and opioid pharmacology of codeine, hydrocodone, and oxycodone
CYP 2D6 activates codeine into morphine and also activates tramadol (peds have higher sensitivity to codeine due to higher CYP2D6 activity than neonates)
CYP2D6 metabolizes oxycodone into oxymorhone and noroxycodone which are weaker, and also hydrocodone into hydromorphone (strong active metabolite ie dilaudid)
SSRI and st John wort effects on CYP
St John wort induces CYPs
Most SSRI inhibit 3A4 and 2D6 like fluoextine, paroxetine, and sertraline
(2D6 is for opioid metabolism)
(3A4 for propofol, midazolam, Lidocaine metabolism)
How does Beta 2 agrenergic agonism cause bronchodilation
GPCR causes increase of cAMP and decrease of intracellular Ca
symptoms of propofol infusion syndrome
metabolic lactic acidosis
rhabdomyolysis
hyperkalemia
renal failure
HLD (high triglycerides)
pancreatitis
cardiac failure
NMDA receptors are activated by what and how do they function
activated by glutamate
increase intracellular Ca from depolarized voltage gated Ca channels
Ketamine MOA
NMDAr antagonist by blocking glutamate
indirect GABA/mu agonism
direct negative inotrope activity but causes CNS stimulation that increases sympathetic outflow
dissociates thalamus from the RAS
Etomidate MOA
GabaA agonist
can cause adrenal suppression by inhibiting 11Bhydroxylase
medications used to treat muscle spasms
baclofen
dantrolene
tizanidine
diazepam
anesthesia drugs metabolized by CYP3A4
propofol, alfentanil, midazolam, lidocaine
what are IgE-related symptoms of with adverse reaction to medications
urticaria
angioedema
dyspnea
dysphagia
bronchospasm
anaphylaxis
what effect does intrapulmonary or intracardiac shunts have on gas vs IV inductions?
intrapulmonary shunt will slow gas induction but no effect on IV induction with higher effect on less soluble gas
intracardiac right>left shunt will slow gas induction and increase IV induction
intracardiac left>right shunt has no effect on gas or IV induction speed
what is the physiology of muscle action potential
presynaptic nerve depolarizes from Ca channels which releases ACh
Postsynaptic nerve has ACh receptors which activate Na channels that lead to action potential
motor end plate, nicotinic AChr require two ACh or one succinylcholine molecule (which is 2x ACh attached by acetate methyl), these bind at the alpha subunits
what is prochlorperazine moa and use? what are risks and subsequent treatment?
antidopaminergic, can be used for nausea
risk of dystonia (facial/neck spasms)/extrapyramidal symptoms, treatment is diphenhydramine or benztropine
what is the pathway of pain signaling
1st order = transduction to dorsal horn
2nd order = dorsal horn decussate to contralateral spinothalamic tract and ascends to thalamus
3rd order = thalamus to postcentral gyrus
what type of information does the spinothalamic tract carry
crude touch, pain, and temperature
when blocking nerves what characteristics influence which are first to be blocked
small n are blocked before larger n due to having larger SA:Vol ratio (ie more exposure to LA)
myelinated nerves are blocked before unmyelinated nerves (unmyelinated nerves have more SA to cover than myelinated for access to receptors)
sensitivity to LA order:
C > a- delta > a-beta > a-alpha
what do these nerves sense/purpose, size, and myelination status:
A-alpha
A-beta
A-delta
C
A-alpha: motor, myelinated and large size
A-beta: touch, myelinated and medium size
A-delta: sharp pain, myelinated small
C: temperature, preganglionic unmyelinated
Dosing for neostigime and glycopyrrolate for reversal
Neo: 0.04-0.07 mcg/kg
Glyco: 0.2mg per 1mg of neo
Titrate in 1cc each every 5-10min
How to calculate time remaining of O2 cylinder
Maximum pressure of E cylinder is 2200psig
Formula:
Hours remaining = cylinder factor × remaining pressure/(flow rate in L/min)
D = 0.16
E cylinder = 0.28
what are the three inhibitory descending pathways that play a role in CRPS?
serotonergic, muscarinic, and noradrenergic
what functions does Mu1 opioid receptor contribute to?
analgesia and physical dependence
What is the delta opioid receptor involved in?
analgesia, physical dependence, and antidepression
compare metabolites of morphine: M3G and M6G
M3G is asoc with hyperalgesia, agitation, myoclonus, and delirium
M6G is assoc with drowsy, Nausea/vomit, coma, respiratory depression
what characteristics of alfentanil allow for its fast onset
lowker pKa, meaning high amounts are not ionized
approximately 6.5 for pKa and 89% non-ionized
moderate lipid solubility
mechanisms of tramadol
NMDA antagonist, SNRI, and weak opioid R agonist
how is codeine metabolized
CYP2D6 will activate codeine into morphine
NSAIDs effects on prostaglandins
decrease PG synthesis which will result in decrease centrally transmitted pain signals at the dorsal horn and decrease substance P and glutamate
How does gabapentin work?
works as an anticonvulsant and alleviates neuropathic pain and it decreases glutamate by binding to the alpha2-delta subunit of the voltage gated Calcium Channel
What are the risk factors for post-puncture headache following attempted epidural injection
young female, thin, pregnant, previous PDPH, larger needle, beveled needles over pencil tip, and air LOR over saline
what is the duration of holding therapeutic vs ppx lovenox prior to conducting neuraxial procedure?
therpeutic enoxaparin = 24hr
ppx enoxaparin = 12 hr
which type of local anesthetic has higher rates of allergic reaction?
aminoamides such as lidocaine have methylparaben which has historically caused higher rates of rxn
when considering a high spinal, what levels are the cardiac accelerators located
T1-4
during femoral nerve block, what does it mean when you nerve stim a patellar twitch vs a sartorius twitch
femoral nerve gives rise to the saphenous nerve which innervates the medial lower leg and foot
causing patellar twitch indicates correct proximity to the femoral nerve
causing sartorius twitch means you need to proceed lateral and deeper
what is the difference between adductor canal block and the femoral block
both aim at the distal branches of the femoral nerve (saphenous) but ADDC block is noninferior to femoral block and has less ris kof falls. Indicated for knee surgery
popliteal fossa nerve block aims at what? what are the distal branches of nerves here?
sciatic nerve which divides into the common peroneal and posterior tibial nerve in the popliteal fossa
common peroneal further divides into the deep peroneal which gives sense between 1-2 toes and and motor to the toe extensors and anterior tibialis, and the superficial peroneal which sense to the dorsum of foot and evert foot
posterior tibial n gives off sural nerve branch at the gastrocnemius which provides sense to the posterolateral calf
are the layers of a tap block?
external oblique, internal oblique, and transversus abdominus
what is the function of musculocutaneous nerve and which block will directly cover this?
axillary block or can isolate MCn at coracobrachialis
MC nerve gives sense to lateral forearm and motor to the brachialis
what are the max lidocaine and epi doses during tumescent liposuction
max lidocaine dose is 35-55mg/kg with amx concentration of 0.1%
max epi dose is 0.055mg/kg (1:1,000,000)
what nerve provides afferent sensory info for the gag relfex
glossopharyngeal n
how does ability to prognath compare to mallampati score for difficult airway
prognath ability has higher PPV and accuracy than MP
what structure are you moving during jaw thrust maneuver
lifting genioglossus muscle which anchors the tongue to the mandible
what is the equation for SVR and how to convert woods to dynes
SVR = 80(MAP-RAP)/CO
where RAP is similar to CVP
during right dominant cardiac anatomy, what supplies the AV node? what about in left dominant anatomy?
right dominant: posterior descending artery supplies AV node
left dominant: left circumflex can occassionally supply but usually supplied by right coronary
what are the major venous structures of the heart?
coronary sinus drains most of the heart and empties into the the junction of the right atrium and the vena cava
great cardiac vein: LAD/LCA
anterior cardiac vein: RCA
middle cardiac vein: PDA
what is ficks principle state
oxygen uptake of a tissue is equal to the product of the oxygen delivered to the tissue and the difference in oxygen content of the blood approaching and leaving the tissue
Ficks equation of oxygen consumption. what can you calculate with this
vO2 = CO(CaO2-CvO2)
where vO2 is consumption
amiodarone mechanism, indications, SFX, and contraindications
block potassiun channels, class III antiarrhythmic
used fro refractory ventricular arrhythmia
however sfx include bradycardia, hypotension, and prolonged QT
cIND: complete heart block and preexisting bradyacardia
nicardipine mechanism, metabolism
calcium channel blocker
directly causes cerebral vasodilation with mild inc in CBF
hepatic metabolism, has increased half life in liver failure patients
no effect on cardiac function, purely systemic by decreasing afterload with arterial dilation
diltiazem mechanism
CCB that acts peripherally and on cardiac
cardiac depressant that can treat angina.
describe transcranial doppler use during carotid endarterectomy
monitors for cerebral hyperperfusion and athersclerotic plaque emboli via blood flow of MCA (temporal)
reduction of >50% is indication of shunting while doubling of flow is hyperemia and anes can decrease cerebral perfusion pressure
how do EEG and SSEP monitoring correlate with blood flow in carotid endarterectomy
EEG can detect regional and global decrease in cerebral blood flow that can lead to intraop stroke
SSEP can detect cortex ischemia
however most strokes from CEA are thromboembolic, not ischemic)
describe deep hypothermic circulatory arrest and what is its target temperature and goal duration
target temp 15-22C
cooling process over 30-60min
lowers metabolic rate of brain
normal duration is about 30-40min depending on temperature
what physiologic changes occur when cross clamping aorta (include arterial and venous)
causes increase in catecholamine release which causes venoconstriction, increasing CVP
coronary perfusion increases but cardiac output decreases, increase PAWP and increase blood volume, with increases arterial BP proximal to clamp
decrease perfusion to kidneys
how does PA catheter measure CO
thermodilution by cold injection at right heart and measure temp at PA
multiple measurements and take average
can be inaccurate during low cardiac state or tricuspid regurgitation
how much does atrial kick contribute to left ventricle volume
up to 40%
what is the target temp for post-arrest hypothermia?
32-36C for 12-24hrs
fastest coolling is endovascular cooling which can decrease temp by 4C/hr
rewarm slowly over 24hrs to goal 37C
risks of rewarming include arrhythmias, electrolyte abn, hypotension, GI bleed, infection
milrinone mechanism
PDE3 inhibitor increasing cAMP and is effective in betablockade!
increases cardiac index without increasing myocardial demand while decreasing SVR, PVR, preload, and afterload by dilating pulm and systemic arteries
needs to be renally adjusted
dobutamine mechanism
selective B1 agonist, 1st line for dec CO but adequate BP
norepinephrine receptor target affinity
alpha»_space;>B1>B2
do nto give IM due to risk of ischemia and tissue necrosis (phenylephrine has reduced risk of necrosis)
anaphylaxis treatment intraop, what is epi dose for peds vs adults
remove offending agent
100% O2
DC anesthetic agents
25cc/kg IVF
epinephrine (peds = 1mcg/kg, adults = 50-100mcg IV)
