General Anesthesia Flashcards
anesthesia
*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
regional anesthesia
*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
general anesthesia vs sedation
*basically just a continuum
*minimal sedation -> moderate sedation -> deep sedation -> general anesthesia (no response, even with painful stimulus)
3 phases of anesthesia care
- preoperative (review procedure, hx, and PE; develop anesthetic plan: technique, airway management; medication administration)
- intraoperative (carry out plan; physiologic monitoring)
- postoperative (monitoring, post-op regiment, disposition, follow up)
3 divisions of the intraoperative phase, when using general anesthesia
- induction (going to sleep)
- maintenance (staying asleep)
- emergence (waking up)
induction phase
*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)
maintenance phase of anesthesia
*fairly easy
*most commonly maintained with inhalational volatile anesthetics
*3 components of anesthesia:
1. amnesia - volatile anesthetic
2. akinesis - muscle relaxants
3. analgesia - opioids
minimum alveolar concentration (MAC)
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
factors leading to increased MAC requirements
*acute amphetamine toxicity
*cocaine
*chronic alcohol use
*young age (highest at 6mo of age, decreases for the rest of life)
*hyperthermia
*red hair
factors leading to decreased MAC requirements
*propofol, etomidate, barbiturates, benzos, ketamine
*alpha-2 agonist (clonidine, etc)
*acute alcohol use
*local anesthetics
*opioids
*chronic amphetamine use
*advanced age
*hypercarbia
*hypothermia
*pregnancy
emergence from anesthesia
*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)
solubility of inhaled anesthetics
*decreased solubility in blood = rapid induction/recovery
*increased solubility in lipids = increased potency = 1/MAC
general onset and offset of IV anesthetics
REDISTRIBUTION of the drug leads to rapid onset and offset of IV anesthetics
types of IV anesthetics
*propofol
*barbiturates
*benzos
*ketamine
*etomidate
IV anesthetic: propofol
*most commonly used
*NO analgesic properties
*has anti-emetic properties
*profound respiratory depressant
*decreases cerebral blood flow
IV anesthetic: benzos
*most commonly used for procedural sedation and anxiolysis
*cause anterograde amnesia (does not make new memories)
IV anesthetic: ketamine
*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)
IV anesthetic: etomidate
*adrenocortical suppression
*increased nausea and vomiting
neuromuscular blockers
*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)
neuromuscular blocker: succinylcholine
*rapid onset and ultrashort duration
*used for rapid sequence induction
*side effects: HYPERKALEMIA, cardiac dysrhythmias, fasciculations, myalgias, trismus, MALIGNANT HYPERTHERMIA
when should succinylcholine be AVOIDED?
*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)
malignant hyperthermia
*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
non-depolarizing neuromuscular blockers
*compete for ACh at postjunctional nicotinic cholinergic receptors, preventing ion permeability (inhibits depolarization)
*termination of effect:
-classically, anticholinesterase + anticholinergic
-recently, sugamadex
airway management
*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
airway assessment - things to look at
*oral aperture/incisor gap
*thyromental distance
*cervical ROM / atlanto-occipital extension
*BMI > 30 = increased risk of airway difficulty
*Malampatti classification
Malampatti Classification
*amount of oropharyngeal tissue individual has; relevant for ability to intubate pt
*class I (best) - class IV (worst)
pre-oxygenation
*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
