Unit 3-General Anesthetics Flashcards
Nitrous Oxide
Class
Inorganic gas
Nitrous Oxide
Mechanism
NMDA receptor antagonist
Nitrous Oxide
Uses
Mask induction in children; adjuvant to volatile anesthetics for maintenance, opioids
But does not produce muscle relaxation
Nitrous Oxide
Side effects
Post-operative nausea and vomiting; inactivates vitamin B12 (leading to abnormal embryonic development, abortion); accumulates in closed, air-containing spaces (bowel, middle ear, pneumothoraces, air emboli) because N2O insoluble in blood
Isoflurane
Class
Volatile anesthetic
Isoflurane
Uses
Most potent
Gold standard for maintenance of anesthesia
Isoflurane
Side effects
Pungent; dose dependent CNS depression, increase in cerebral blood flow and intracranial pressure; dose dependent decrease in systemic BP, decrease in respiratory function; relaxes skeletal muscle; increase in HR; malignant hyperthermia
Desflurane
Class
Volatile anesthetic
Desflurane
Uses
Least soluble, least potent bc completely fluorinated (allows for rapid emergence from anesthesia)
Maintenance of anesthesia
Desflurane
Side effects
Most pungent (airway irritation symptoms); dose dependent CNS depression, increase in cerebral blood flow and intracranial pressure; dose dependent decrease in systemic BP, decrease in respiratory function; relaxes skeletal muscle; increase in HR; malignant hyperthermia
Sevoflurane
Class
Volatile anesthetic
Sevoflurane
Uses
Less soluble, less potent (but not irritating)
Mask induction in children and adults; maintenance of anesthesia
Sevoflurane
Side effects
Can form CO if not combined with CO2 correctly; dose dependent CNS depression, increase in cerebral blood flow and intracranial pressure; dose dependent decrease in systemic BP, decrease in respiratory function; relaxes skeletal muscle; malignant hyperthermia
Methohexital
Class
Barbiturates
Methohexital
Mechanism
GABAa receptor agonist, antagonist of NMDA-glutamate receptor; produce hypnosis & sedation, but is anti-analgesic
Redistribute from brain to muscle and fat, metabolized by liver; dosed based on lean body mass
Methohexital
Uses
Induce general anesthesia
Propofol
Class
Alkylphenol (a fatty acid)
Propofol
Mechanism
GABAa receptor agonist (hypnosis), antagonist of NMDA-glutamate receptor; some a2 receptor activity;
acts on GABAa and glycine receptors in spinal cord
rapid onset and offset
Propofol
Uses
Anti-emetic at low doses; induction and maintenance of general anesthesia; sedation in ICU, procedural sedation
Propofol
Side effects
Propofol infusion syndrome: being given for several days leads to metabolic acidosis, rhabdomyolysis, heart & renal failure, lowering of BP, bradycardia, and death (likely due to fatty acid oxidation)
Painful injection site; supports bacterial growth
Administered IV in a lipid emulsion (cause of pain); be aware of allergies (egg and soy in emulsion); no malignant hyperthermia
Etomidate
Class
Carboxylated imidazole
Etomidate
Mechanism
GABAa receptor agonist (only D-isomer)
Etomidate
Uses
Hypnosis; no analgesic activity
Etomidate
Side effects
Pain on administration (due to solvent, propylene glycol); involuntary myoclonic movements due to subcortical disinhibition (not a seizure); post-operative nausea and vomiting; single dose inhibits cortisol synthesis
Minimal cardiorespiratory depression (good agent in patients with minimal cardiac reserve)
Ketamine
Class
Phencyclidine
Ketamine
Mechanism
NMDA receptor antagonist, kappa opiate agonist; leads to dose-dependent unconsciousness, amnesia, analgesia
Causes functional disorganization by depressing parts of cortex and thalamus, stimulating limbic system
Ketamine
Uses
Sedative/anesthetic for pediatric/developmentally delayed patients; induction in patients with reactive airway disease, hypovolemia (trauma patients), cardiac disease; with propofol for IV procedural sedation; adjuvant during and after surgery to reduce opiod use; part of multimodal pain therapy regimen; depression treatment
Ketamine
Side effects
Stimulates sympathetic nervous system outflow; increases cerebral blood flow, ICP; emergence delerium; nystagmus, lacrimation, salivation, and dissociative anesthesia
Racemic mixture (S more potent); metabolized by P450 (norketamine, a third to a fifth as effective); great bronchodilator; contraindicated in CAD patients and those with with intracranial lesions