VARIOUS DEGREES of acute elevation of blood pressure have been reported to produce complications, ranging in severity from headache, nausea, and vomiting to serious or even fatal vascular accidents.1-5We consider any abrupt increase in systolic blood pressure of 30% or more to be a distinct threat, and classify it arbitrarily as an "acute hypertensive crisis." Acute hypertensive crises during and after operation are commonly the result of faulty anesthetic equipment or technique, particularly errors that cause hypercapnia, hypoxia, or a sudden increase in blood volume. Prudence dictates that such causes should be meticulously investigated and remedied before reliance is placed on a drug to treat one sign of a serious physiologic disturbance. Occasionally correction of all detectable errors fails to restore an elevated blood pressure to normal; or factors beyond the control of the anesthetist, such as untoward responses to pressor drugs, the patient's underlying disease, or the