Ch: 20/21 General Anesthetics

Front 1

The 4 A's of gen. anesthesia?

Back 1

Amnesia, Analgesia, Akinesia, Autonomic and sensory reflex block

Front 2

What's MAC?

Back 2

Minimum Alveolar Concentration: The steady-state min. alveolar conc. of an inhalational agent required for immobility in 50% of patients.

Front 3

MAC values

Back 3

0.5 MAC: MAC Awake: 50% pts can be awakened
1.0MAC: MAC: 50% pts will not move at surgical incision
1.3MAC: ED95: 95% pts will not move
1.5-2.0 MAC: MAC-BAR: 50% have blocked autonomic response

Front 4

Inhaled anesthetics pharmacokinetics

Back 4

Quicker action with the following: low plasma solubility, high inspired concentration, increased ventilation, DECREASED pulmonary blood flow, elimination only relevant for halothane.

Front 5

Inhaled anesthetics pharmacodynamics

Back 5

possibly action through ligand-gated Chloride channels gated by inhibitory GABAa receptors.

Front 6

Inhaled anesthetics CV effects

Back 6

most decrease MAP and vasc. resistance BUT Halothane sensitizes myocardium to catecholamines and may result in ventricular arrhythmias.

Front 7

Inhaled anesthetics Respiratory effects

Back 7

depressed, desensitization to CO2 so low response to hypoxia

Front 8

Inhaled anesthetics Brain effects

Back 8

decreased metabolic rate but INCREASED blood flow, which can be minimized by prior hyperventilation

Front 9

Inhaled anesthetics kidney and liver effects

Back 9

decreased blood flow

Front 10

What's malignant hyperthermia?

Back 10

a genetic susceptibility where succinycholine plus inhaled agent causes altered muscle tone, hyperthermia, CO2 productin, and acidosis. Treat with Dantrolene (a Ca blocker). Dx made with muscle biopsy only.

Front 11

Inhalational drugs

Back 11

halothane (high solubility, arrythmias), Isoflurane (most widely used in modern countries, airway irritation, decrease MAP, increase HR), Desflurane, Sevoflurane, Nitrous Oxide (non-halogenated gas, used as adjunct)

Front 12

IV anesthetics: Barbiturates

Back 12

via GABA action, Thiopental: most commonly IV for GA. Rapid onset and short lived.//
Issues: decrease in preload, MAP and CO results in HR increase (not good in pt in hypovolumic shock)NO ANALGESIA

Front 13

IV anesthetics: Etomidate

Back 13

via GABA action, good b/c no changes in Respiratory rate or Cardiac output. //
Issues: adrenocortical suppression with overuse, NO ANALGESIA

Front 14

IV anesthetics:Propofolol

Back 14

via GABA action, similar to barbiturates with slightly more rapid recovery, no compens. HR changes unlike barbiturates, has anti-emetic effects, useful in total intravenous anesthesia (TIVA). NO ANALGESIA

Front 15

IV anesthetics: Opioids

Back 15

via mu, kappa, delta receptors., minimal circulatory deteriation, dose dep. respiratory depression. I.E. sufentanil, remifentanil. Antagonized by Naloxone. ANALGESIC

Front 16

IV anesthetics:Benzodiazepines

Back 16

GABA mediated, anxiolytic/amnestic, e.g Midazolam. Inhibited by flumazenil

Front 17

IV anesthetics: Ketamine

Back 17

action through glutamic acid and NMDA receptor, produces state of DISSOCIATIVE anesthesia (catatonia, amnesia and ANALGESIA). Can be used for sedation and GA. Produces CV stimulation (via decreasing reuptake of catecholamines). If no catchecholamine then depresses CV. so ideal in hypovolumic shock pts. No change in resp. rate. Increase in cerebral flow and metabolic rate.