THE EFFECT OF KETAMINE ON TRANSMEMBRANE POTENTIALS OF PURKINJfi FIBRES OF THE PIG HEART

The action of ketamine upon spontaneously active and electrically driven Purkinje fibres of the moderator band of the pig heart has been studied using a floating microelectrode technique. Ketamine hydrochloride altered the transmembrane potential in a dose-related and reversible manner. Concentrations of 1X 10M were subthreshold whereas 5 X 10'M and 1X 10~M slowed the frequency and increased the action potential duration of spontaneous preparations, actions consistent with an antiarrhythmic effect. Higher concentrations of 5 X 10'M ketamine initially led to a shortening of the action potential duration, then failure of the original spontaneous activity. During recovery pacemaker-like activity developed associated with a loss of resting membrane potential. In electrically driven preparations 5 X 10"M ketamine significantly shortened the duration of the action potentials between evoked potentials and markedly augmented the response to adrenaline, actions consistent with an arrhythmogenic effect. These findings suggest a basis for isolated reports of cardiac side effects.