Case StudyA 18-year-old male is in the intensive care unit after suffering from a fall. Injuries include multiple facial lacerations and fractures. He was intubated due to combativeness and for airway protection. Initial sedation was with midazolam and fentanyl, but switched to another drug to facilitate neurologic exam. Fentanyl and morphine were given as bolus to maintain analgesia. He became unstable on day 5 and required phenylephrine and epinephrine infusions. Lab findings show hyperkalemia, metabolic acidosis, hyperlipidemia, increased creatine kinase, and acute kidney injury. Liver enzymes were also elevated. Later he developed cardiac arrhythmia progressing to cardiac arrest. He was unable to be resuscitated. What happened?
Learning Objectives1.Describe the reason for using multiple general anesthetics in combination2.Compare potency and rate of induction/elimination of inhalation anesthetics based on partition coefficient and minimal alveolar concentration3.Discuss and compare the limitations of individual inhalation anesthetics4.Explain the importance of context-sensitive halftime of intravenous anesthetics with relations to clinical uses of induction or maintenance 5.Compare and contrast the mechanism of action, side effects, advantages, and disadvantages of intravenous anesthetics
OutlineI.HistoryII.General Anesthetics1.Inhalation AnestheticsA.Stages of AnesthesiaB.Uptake and DistributionC.Minimal Alveolar ConcentrationD.Rate of Induction/ EliminationE.Partition CoefficientF.Analgesic IndexG.Mechanism of ActionH.Side Effects 2.Intravenous AnestheticsIII. Summary
I. History➢For centuries, surgeries were limited to rapid procedures (limb amputations)➢1846, 1stpublic demonstration of anesthesia using diethyl ether was performed at Massachusetts General Hospital (revolutionary event)➢Diethyl ether is no longer used in US due to slow rate of induction, postoperative nausea and vomiting, and high inflammability➢1847, chloroform introduced, which has a more pleasant odor and is nonflammable; causes severe hepatotoxicity and cardiac depression➢1929, cyclopropane introduced, which is pleasant-smelling and has rapid induction and recovery; highly explosive ➢1956, halothane introduced, nonflammable hydrocarbon
II. General Anesthetics➢Two main types of general anesthetics:1.Inhalation2.Intravenous➢Five desired effects of general anesthetics:1.Analgesia2.Amnesia (benzo/barbiturates)3.Immobility4.Inhibition of autonomic reflexes5.Unconsciousness➢None of the current general anesthetics can achieve all five desired effects when used as monotherapy➢Modern practice uses combination of inhalation and intravenous general anesthetics➢Balanced anesthesia
II.1.A. Stages of Anesthesia➢Anesthetic states are traditionally (diethyl ether) divided into four stages➢Modern anesthesia have faster induction and avoids stage II➢Stage III is the stage where surgery