Hemodynamic and central nervous system effects of intravenous bolus doses of lidocaine, bupivacaine, and ropivacaine in sheep.

Lidocaine hydrochloride (HCl) (80-320 mg), bupivacaine HCl (20-80 mg), and ropivacaine HCl (30-120 mg) were administered as intravenous bolus doses to conscious sheep (n = 18; average body weight 45 kg) that had previously placed intravascular cannulae for hemodynamic monitoring and for obtaining blood samples. The mean convulsive doses and arterial blood concentrations were approximately 110 mg and 40 mg/L, respectively, for lidocaine HCl, 45 mg and 14 mg/L for bupivacaine HCl, and 60 mg and 20 mg/L for ropivacaine HCl. After subconvulsive doses of each agent, there were minimal cardiovascular effects. After convulsive doses, there were marked increases in heart rate, mean arterial pressure, pulmonary artery pressure, cardiac output, systemic vascular resistance, left ventricular end diastolic pressure, and myocardial contractility. Ventricular fibrillation caused death in two sheep after bupivacaine (80 mg) and in two sheep after ropivacaine (90 and 120 mg) administration. With sublethal doses, the hemodynamic responses to these agents were qualitatively and quantitatively similar when compared with their local anesthetic potencies.