Anesthetics Flashcards
Anesthetic drugs with decreased solubility in blood exhibit…
Rapid induction and recovery times
Anesthetic drugs with increased solubility in lipids exhibit…
Increased potency
Anesthetic potency =
1 / MAC
What is the MAC of an inhaled anesthetic?
MAC = Minimum Alveolar Concentration (of inhaled anesthetic) required to prevent 50% of subjects from moving in response to noxious stimulus (e.g., skin incision)
Nitrous oxide (N2O) has…
Low blood and lipid solubility and thus exhibits fast induction and low potency.
Halothane has high lipid and blood solubility and thus…
Slow induction but high potency
List some inhaled anesthetics.
- Halothane
- Enflurane
- Isoflurane
- Sevoflurane
- Methoxyflurane
- Nitrous oxide
Effects of inhaled anesthetics
- Myocardial depression
- Respiratory depression
- Nausea/emesis
- Increased cerebral blood flow (decreased cerebral metabolic demand)
Toxicities associated with inhaled anesthetics
- Hepatotoxicity (halothane)
- Nephrotoxicity (methoxyflurane)
- Proconvulsant (enflurane)
- Expansion of trapped gas in a body cavity (N2O)
- Malignant hyperthermia – rare, life-threatening hereditary condition in which inhaled anesthetics (except N2O) and succinylcholine induce fever and severe muscle contractions
Treatment for malignant hyperthermia
Dantrolene
Barbiturate used intravenously for induction of anesthesia and short surgical procedures.
Thiopental – exhibits high potency, high lipid solubility, and rapid entry into brain
Effect of thiopental terminates naturally by…
Rapid redistribution of thiopental into tissue (i.e., skeletal muscle) and fat.
Thiopental decreases…
Cerebral blood flow
Benzodiazepine used intravenously for anesthesia in endoscopic procedures; also used adjunctively with gaseous anesthetics and narcotics
Midazolam
When used as an IV anesthetic, midazolam may cause…
Severe postoperative respiratory depression, decreased blood pressure (treat overdose with flumazenil), and anterograde amnesia
What are arylcyclohexylamines (e.g., ketamine) and how do they work?
PCP analogs that act as dissociative anesthetics; block NMDA receptors
Describe the physiologic effects of ketamine.
- Disorientation
- Hallucination
- Bad dreams
- Cardiovascular stimulation
- Increased cerebral blood flow
…and…are opioids used intravenously with other CNS depressants during general anesthesia.
Morphine; fentanyl
Used for sedation in ICU, rapid anesthesia induction, short procedures
Propofol
How does propofol work?
Potentiates GABAA activity.
Propofol causes less…than thiopental.
Postoperative nausea
CNS drugs must be…or be…
Lipid soluble (cross the BBB); actively transported
List some local anesthetics
- Esters – procaine, cocaine, tetracaine
- Amides – lidocaine, mepivacaine, bupivacaine
Remember: amides have 2 I’s in the name
How do local anesthetics works?
Block Na+ channels by binding to specific receptors on inner portion of channel; preferentially bind to activated Na+ channels, so most effective in rapidly firing neurons; tertiary amine local anesthetics penetrate membrane in uncharged form and then bind to ion channels as charged form
