This is followed by a phase of cardiovascular depression with reduced cardiac output and hypotension. This may lead to complete cardiovascular collapse with no pulse, no blood pressure and no cardiac rhythm. For example, the dose needed for cardiovascular collapse divided by the dose needed for convulsions is 3.7 for bupivacaine compared with 7.1 for lidocaine. When bupivacaine toxicity occurs, it is more likely to result in ventricular arrhythmias than with other agents. As indicated, these arrhythmias are best treated with bretylium.
Pregnant women appear to be more sensitive to bupivicaine cardiac toxicity.
Finally, this toxicity is enhanced by acidosis and hypercarbia.