Cardiovascular effects of convulsant and supraconvulsant doses of amide local anesthetics
de Jong, R.H.; Ronfeld, R.A.; DeRosa, R.A.
Anesthesia and Analgesia 61(1): 3-9
1982
ISSN/ISBN: 0003-2999 PMID: 7198411 Document Number: 187931
Because resuscitation from toxic responses to bupivacaine (B) or etidocaine (E) is difficult, the cardiovascular effects of these 2 local anesthetics were compared with those of lidocaine (L) in 40 lightly anesthetized, ventilated cats. First, the circulatory effects of a threshold convulsant dose (1 .RTM. CD) of local anesthetic were determined. One hour later, local anesthetic was infused beyond the onset of convulsions until the blood pressure (BP) decreased to < 50 torr, or until the electroencephalogram (EEG) became flat. When drugs were infused at equiconvulsant rates (1 mg/kg per min for B and E; 4 mg/kg per min for L), electrical convulsions began after 4-6 min. Nodal and ventricular cardiac arrhythmias regularly appeared with B and E, but not with L. BP increased with B and E, but decreased slightly with L, B and E seizures lasted approximately 2 times longer than L seizures; BP and electreocardiogram (ECG) returned to control levels within 10 min. After full recovery, local anesthetic infusion was restarted; all cats survived at least 2 .times. CD. Arrhythmias reappeared after approximately 0.6 .times. CD of B or E. Only 8 of 15 cats had arrhythmias after 2 .times. CD of L. After the onset of seizures, BP decreased progressively with B or E, more rapidly with L. When BP reached 50% of control levels after 2.3 .times. CD of L, 12 cats were given ephedrine, 1 mg, and survived 3 .times. CD of L; of the other 3 cats, 2 died before 3 .times. CD of L. Cats given B or E did not require ephedrine, and 8 of 9B and 13 of 15E cats recovered after 3 .times. CD. Cats apparently survived at least 2 times the convulsant dose of amide local anesthetics, provided oxygenation and ventilation are supported. With higher doses, cardiac arrhythmias and hypotension increasingly compromise circulation.