Cardiac Surgery in a Patient Taking Monoamine Oxidase Inhibitors (original) (raw)

1994, Anesthesia & Analgesia

M onoamine oxidase inhibitors (MAOIs), are used to treat endogenous psychotic depression. The MAOIs do not inhibit catecholamine synthesis; rather they block the oxidative deamination of endogenous catecholamines into inactive vanillylmandilic acid. This block of MA0 produces an accumulation of endogenous catecholamines in adrenergically active tissues, such as the brain, which is thought to be responsible for alleviation of depression. Major concerns with the clinical use of MAOIs are related to 1) the risk of dietary intake of tyramine, an indirect sympathomimetic, which can trigger a release of accumulated catecholamines, 2) drug interactions, specifically with opioids, which have been reputed to cause a syndrome of hyperpyrexia, hypertension, tachycardia, and coma (1 1, and 3) hepatotoxicity, which does not seem to be related to dose or duration of treatment. When patients on MAOIs require urgent surgery or the relief of severe pain, there is concern about these potentially fatal drug interactions. Despite such potential interactions and risks, adverse outcomes are rarely reported in clinical practice. However, there are 12 case reports in the world literature implicating the combination of meperidine and MAOIs as potentially fatal, this being related to an inhibition of 5-hydroxytryptamine (5-HT) uptake by both the opioid and MA01 in the brain leading to increased levels of 5-HT at the synaptic cleft and consequent adverse reactions including hyperpyrexia, hypertension, hypotension, tachycardia, or convulsions (2-12). There has been only one case described of an adverse morphine/MAOI interaction (13). This involved a patient who became hypotensive and unconscious after receiving morphine (6 mg intravenously [IV]), but the etiology was uncertain. Five cases have been reported of fentanyl being administered to patients on chronic MA01 therapy (14-16); four of these cases did not have an adverse outcome