Electrocardiographic and hemodynamic effects of intravenous cocaine in awake and anesthetized dogs.

Graded bolus and infusion doses of cocaine were given to 18 dogs, 6 under general anesthesia and 12 awake, to determine the range of hemodynamic and electrocardiographic effects. Blood pressure, electrocardiographic measurements, cocaine plasma levels, temperature, electrolytes, and arterial blood gases were measured before and after the initial bolus and/or infusion at 10 minutes and each 30 minutes up to a maximum of 180 minutes. At the end of the infusion, a single large intravenous terminal bolus of cocaine was given. The hemodynamic and electrocardiographic changes occurred by 10 minutes after the bolus and resolved by 30 minutes, independent of the infusion rate and dose. Only anesthetized dogs could tolerate the highest cocaine doses. Three ranges of bolus doses were given: the lowest range was the average initial bolus dose received by the awake group; the intermediate range was the average initial bolus dose received by the anesthetized group; and the highest range was the average terminal bolus dose. The heart rate changes were unpredictable and did not change significantly at any dose range. The blood pressure increased in the lowest dose range, remained unchanged at intermediate doses, and fell at the highest doses in four of six dogs. Electrocardiographic intervals increased as the dose range increased. Only at the highest doses did potentially lethal ventricular arrhythmia (ventricular tachycardia and an idioventricular escape rhythm) occur. Intravenous cocaine causes hemodynamic and electrocardiographic effects that are related to the dose and rate of administration. At high doses, hypotension, arrhythmia, and electrocardiographic changes consistent with infranodal and/or intraventricular conduction slowing can occur.