Scientific Principles |
|Part B:||Intravenous Anesthetics|
|Chapter 9:||Nonbarbiturate Intravenous Anesthetics|
Side Effects and Contraindications
The common psychologic emergence reactions are discussed earlier. Contraindications to ketamine relate to specific pharmacologic actions and patient diseases. Patients with increased ICP and with intracranial mass lesions should not receive ketamine because it can increase ICP and has been reported to cause apnea on this basis. 231 The S-(+) enantiomer also increases CBF and is probably similarly contraindicated. 232 Ketamine is also contraindicated in patients with an open eye injury or other ophthalmologic disorder, in whom a ketamine-induced increase in intraocular pressure would be detrimental (Ch. 63). Because ketamine has a propensity to cause hypertension and tachycardia, with a commensurate increase in myocardial oxygen consumption, it is contraindicated as the sole anesthetic in patients with ischemic heart disease. 181 Likewise, it is unwise to give ketamine to patients with vascular aneurysms because of the possible sudden change in arterial pressure. Psychiatric disease such as schizophrenia or a history of adverse reaction to ketamine or one of its congeners also constitutes a contraindication. 119 One should also consider carefully using ketamine when there is a possibility of postoperative delirium from other causes (e.g., delirium tremens, possibility of head trauma) and a ketamine-induced psychomimetic effect would cloud the differential diagnosis.
Other side effects include potentiation of nondepolarizing neuromuscular blockade by an undefined mechanism. 233, 234 Finally, because ketamines preservative, chlorobutanol, has been demonstrated to be neurotoxic, subarachnoid administration is contraindicated. 235 It is probably unwise to administer the drug epidurally for this reason.
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