Abstract

Lightly anesthetized, ventilated, paralyzed cats had convulsions induced by lidocaine (n = 40) or bupivacaine (n = 45). The mean control arterial Po₂ (Fio₂ ⋍ 0.3) was 176 torr; the lowest Po₂ anytime thereafter was never less than 120 torr. At the onset of convulsions, arterial pH was 0.04 (bupivacaine group) to 0.06 (lidocaine group) units less than control; Pco₂ was 1.1 (bupivacaine group) to 2.1 (lidocaine group) torr greater than control; plasma bicarbonate ion concentration decreased 1.1 (bupivacaine group) to 1.4 mmol/L (lidocaine group). To yield long-lasting seizures, local anesthetic infusion was continued until twice the convulsant dose (bupivacaine 10.6 mg/kg, lidocaine 56.0 mg/kg) had been given. Some 15 minutes later, arterial Pco₂ and pH had not changed significantly from threshold ictal values. We conclude that adequate alveolar ventilation will maintain acid-base balance and aid survival after massive overdoses of amide local anesthetics.