The debate over the administration of sodium bicarbonate in cardiac arrest has been going on for several decades, swinging like a pendulum from "first-line drug" to "not indicated" to the recent guidelines advocating "a small bolus under special conditions (metabolic acidosis, intoxication, long-term resuscitation)". A targeted, blood-gas controlled application under optimised ventilation conditions has not yet been evaluated prehospitally. Our preliminary studies have shown that an arterial puncture/line as well as measurement of blood gases is feasible in preclinical conditions. This multicentre trial including 5 centres and 10 physician-staffed emergency systems is designed to compare, in a prospective randomised controlled study, the effect of a calculated dosage of sodium bicarbonate based on the patient´s base deficit and weight, on ROSC (= return of spontaneous circulation) and on the secondary survival of cardiac arrest patients. The null hypothesis is that there is no or negative impact on survival.

Inclusion Criteria:

• prehospitally started cardiopulmonary resuscitation (CPR)
• advanced cardiac life support provided
• age >18 years
• arterial pH < 7,2
• arterial BE < -12
• arterial pCO2 15-75 mmHg
• arterial pO2 >35 mmHg

Exclusion Criteria:

• women of childbearing age
• traumatic cardiac arrest