Unexpected return of cardiac action after termination of cardiopulmonary resuscitation.

Application of sodium bicarbonate is still an option when resuscitation efforts remain unsuccessful. Despite this, there are no recommendations on how long resuscitation should be performed after administration of this drug. Here we describe a case in which prehospital resuscitation efforts were terminated about 35 min after cardiac arrest. Seven minutes after all efforts had been discontinued, spontaneous sinus rhythm appeared from a zero-line ECG, giving normal hemodynamic values. The underlying reason might be unexpected and unrecognized hyperkalemia, which was diminished by administration of sodium bicarbonate, even under the conditions of cardiocirculatory arrest.