General Anesthesia

Question 1

anesthesia

Answer 1

*insensitivity to pain or painful stimuli (ie surgery)
*can be achieved essentially 2 ways:
1. general anesthesia - anesthetizing the “big ganglion”; loss of consciousness
2. regional anesthesia - anesthetizing local nerves; loss of consciousness not necessary, but often provided for personal comfort

Question 2

regional anesthesia

Answer 2

*a technique for providing locoregional anesthesia to a specific part of the body without necessarily affecting consciousness; achieved through the selective use of local anesthetics
*examples: peripheral nerve blocks, fascial plane blocks, spinal anesthesia, epidural anesthesia

Question 3

general anesthesia vs sedation

Answer 3

*basically just a continuum
*minimal sedation -> moderate sedation -> deep sedation -> general anesthesia (no response, even with painful stimulus)

Question 4

3 phases of anesthesia care

Answer 4

1. preoperative (review procedure, hx, and PE; develop anesthetic plan: technique, airway management; medication administration)
2. intraoperative (carry out plan; physiologic monitoring)
3. postoperative (monitoring, post-op regiment, disposition, follow up)

Question 5

3 divisions of the intraoperative phase, when using general anesthesia

Answer 5

1. induction (going to sleep)
2. maintenance (staying asleep)
3. emergence (waking up)

Question 6

induction phase

Answer 6

*inhalational or IV induction used to put the patient to sleep
*can be dangerous:
-transition from negative pressure to positive pressure ventilation (spontaneous to mechanical)
-hemodynamic compromise secondary to IV induction agents -> hypotension
**managing the airway (intubation, supra-glotic airway, native airway)

Question 7

maintenance phase of anesthesia

Answer 7

*fairly easy
*most commonly maintained with inhalational volatile anesthetics
*3 components of anesthesia:
1. amnesia - volatile anesthetic
2. akinesis - muscle relaxants
3. analgesia - opioids

Question 8

minimum alveolar concentration (MAC)

Answer 8

gas analyzer on anesthesia machine can calculate MAC values for expiratory volatile anesthetic concentration (used to determine how much anesthetic you need to keep someone asleep and unaware)
*1.0 MAC = 50% of patients are akinetic
*1.2 MAC = 95% of patients are akinetic

Question 9

factors leading to increased MAC requirements

Answer 9

*acute amphetamine toxicity
*cocaine
*chronic alcohol use
*young age (highest at 6mo of age, decreases for the rest of life)
*hyperthermia
*red hair

Question 10

factors leading to decreased MAC requirements

Answer 10

*propofol, etomidate, barbiturates, benzos, ketamine
*alpha-2 agonist (clonidine, etc)
*acute alcohol use
*local anesthetics
*opioids
*chronic amphetamine use
*advanced age
*hypercarbia
*hypothermia
*pregnancy

Question 11

emergence from anesthesia

Answer 11

*turn off gas, stop TIVA, etc… allow the patient to metabolize or offload the offending agent
*assess adequacy of analgesia
*prophylactic administration of anti-emetic medications
*reversal of muscle relaxants
*can be dangerous: transition from mechanical to spontaneous ventilation (risk of hypoventilation, laryngospasm, bronchospasm)

Question 12

solubility of inhaled anesthetics

Answer 12

*decreased solubility in blood = rapid induction/recovery
*increased solubility in lipids = increased potency = 1/MAC

Question 13

general onset and offset of IV anesthetics

Answer 13

REDISTRIBUTION of the drug leads to rapid onset and offset of IV anesthetics

Question 14

types of IV anesthetics

Answer 14

*propofol
*barbiturates
*benzos
*ketamine
*etomidate

Question 15

IV anesthetic: propofol

Answer 15

*most commonly used
*NO analgesic properties
*has anti-emetic properties
*profound respiratory depressant
*decreases cerebral blood flow

Question 16

IV anesthetic: benzos

Answer 16

*most commonly used for procedural sedation and anxiolysis
*cause anterograde amnesia (does not make new memories)

Question 17

IV anesthetic: ketamine

Answer 17

*dissociative anesthesia - cataleptic akinetic state where patient’s eyes remain open with slow nystagmic gaze
*profound analgesic
*profund vasodilator
*pt will breath spontaneously and won’t move
*emergence reactions (vivid colorful dreams, hallucinations)

Question 18

IV anesthetic: etomidate

Answer 18

*adrenocortical suppression
*increased nausea and vomiting

Question 19

neuromuscular blockers

Answer 19

*a group of drugs that cause muscle relaxation to facilitate endotracheal intubation and/or akinesis during operative procedures
*2 classes: depolarizing (succinylcholine) and non-depolarizing (vecuronium, rocuronium, cisatracurium)

Question 20

neuromuscular blocker: succinylcholine

Answer 20

*rapid onset and ultrashort duration
*used for rapid sequence induction
*side effects: HYPERKALEMIA, cardiac dysrhythmias, fasciculations, myalgias, trismus, MALIGNANT HYPERTHERMIA

Question 21

when should succinylcholine be AVOIDED?

Answer 21

*24-72 hrs after major burns, trauma, immobility or extensive denervation (stroke, spinal cord injury) = severe hyperkalemia secondary to release from extrajunctional Ach receptors
*muscular dystrophy (FDA warning for use in peds; only for use in emergent intubation)

Question 22

malignant hyperthermia

Answer 22

*inherited disorder of skeletal muscle metabolism that can be triggered by inhaled volatile anesthetics and succinylcholine
*sx: tachycardia, muscle rigidity, hyperthermia, hyperkalemia, acidosis
*fatal if untreated/unrecognized
*tx: discontinue offending agent, immediate administration of IV DANTROLENE

Question 23

non-depolarizing neuromuscular blockers

Answer 23

*compete for ACh at postjunctional nicotinic cholinergic receptors, preventing ion permeability (inhibits depolarization)

*termination of effect:
-classically, anticholinesterase + anticholinergic
-recently, sugamadex

Question 24

airway management

Answer 24

*concept of assisting in the oxygenation and ventilation of a patient
*many techniques:
-mask ventilation / ambu-bag
-endotracheal intubation
-supro-glottic device
-cricothyroidotomy
-transtracheal jet ventilation

Question 25

airway assessment - things to look at

Answer 25

*oral aperture/incisor gap
*thyromental distance
*cervical ROM / atlanto-occipital extension
*BMI > 30 = increased risk of airway difficulty
*Malampatti classification

Question 26

Malampatti Classification

Answer 26

*amount of oropharyngeal tissue individual has; relevant for ability to intubate pt
*class I (best) - class IV (worst)

Question 27

pre-oxygenation

Answer 27

*denitrogenates the functional residual capacity
(room air = 70% nitrogen; medical oxygen = 100% O2)
*provides a reserve of oxygen, which still exists even when you stop breathing
*MOST IMPORTATNT STEP WHEN INDUCING A PATIENT AND INTUBATING ASLEEP