Ketamineisadirect-actinganestheticthatiswidelyusedinpediatricpractice because of its dissociative properties and perceived beneficial cardiovascular effects. It is frequently used in the emergency department setting for minor procedures and is used in other areas for induction of anesthesia. Most other sedative and anesthetic agents result in some degree of cardiovascular depressionintheformofhypotension,bradycardia,ordirectnegativeinotropic effects. Ketamine, in contrast, typically causes an increase in heart rate, systemic blood pressure, and systemic vascular resistance. These effects result partially from inhibition of catecholamine reuptake, but also from direct sympathetic stimulation, resulting in increased release of catecholamines. Various studies have shown that ketamine can have either a negative or positive inotropic effect on cardiac function, with the overall effect being dosage dependent but generally negative. Because of these somewhat unpredictable cardiovascular effects, ketamine must be used with caution in certain situations, especially when patients are catecholamine depleted.
Ketamine should be used cautiously in patients who are critically ill or who are acutely traumatized. In these clinical settings, the patient may be effectively catecholamine depleted and unable to mount a sympathetic response to counteract the negative inotropic effect of ketamine. This combination could result in cardiovascular collapse in patients who are septic or otherwise critically ill. Similarly, ketamine should be avoided in patients with limited myocardial reserve or congestive heart failure. These patients may similarly be catecholamine depleted and unable to increase sympathetic tone. Alternatively, those patients who can mount a sympathetic response may have a reduced cardiac output resulting from increased afterload in the setting of a failing myocardium with limited reserve.
Ketamine should, likewise, be avoided in patients who cannot otherwise tolerate an increased afterload, such as those patients with significant preexisting hypertension or those at risk for myocardial ischemia. Ketamine has also been shown to increase both intracranial and intraocular pressure, so it should be used cautiously in patients who have a space-occupying central nervous system lesion or who are at risk for increased intracranial or intraocular pressures.
Bovill JG. Intravenous anesthesia for the patient with left ventricular dysfunction. Semin Cardiothorac Vascu Anesth. 2006;10(1):43–48.
Sprung J, Schuetz SM, Stewart RW, et al. Effects of ketamine on the contractility of failing and
nonfailing human heart muscles in vitro. Anesthesiology. 1998;88(5):1202–1210.
Waxman K, Shoemaker WC, Lippmann M. Cardiovascular effects of anesthetic induction with
ketamine. Anesthes Analg. 1980;59(5):355–358.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6 
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