NEW YORK (Reuters Health) – There is no conclusive evidence that anti-arryhthmic drugs extend overall survival after cardiac arrest, the authors of a new research review conclude.

These medications are standard treatment for cardiac arrest patients, but there is actually very little research on whether they improve clinical outcomes, Dr. Marcus Eng Hock Ong of Singapore General Hospital and his colleagues note in a March 26 online publication in Resuscitation.

To investigate whether these drugs indeed have benefits, the researchers searched the medical literature for studies of lidocaine, procainamide, amiodarone, bretylium, and magnesium in adults with cardiac arrest, defined as asystole, pulseless electrical activity, pulseless ventricular tachycardia (VT) and ventricular fibrillation (VF).

Dr. Ong and his colleagues identified 25 peer-reviewed studies, including nine randomized controlled trials, nearly all of which looked at VT and VF. Only one study included patients with pulseless electrical activity and asystole. Most of the studies compared one drug to another, rather than to placebo.

Two randomized double-blind controlled studies found that amiodarone improved survival to admission compared to lidocaine for patients experiencing refractory VT or VF outside the hospital, but no benefit was seen for overall survival or survival without neurological impairment, the researchers found. Another study found amiodarone improved 24-hour survival compared to lidocaine for hospitalized patients in extended VT.

Evidence for the benefits of the other drugs was mixed, with some studies finding that certain medications actually decreased survival.

Hypothermia has now been proven to improve return of spontaneous circulation in out-of-hospital cardiac arrest due to VF, Dr. Ong and his team note. The studies that found benefits for amiodarone over lidocaine, which were published in 2005 and changed the standard of care, were done before hypothermia’s benefits were known, they add.

“While we are waiting for more data it is reasonable to administer amiodarone in cardiac arrest victims with the hope that as our post arrest treatment improves the overall survival will ultimately improve,” the researchers write.

“There is inadequate evidence,” they conclude, “to support or refute the use of lidocaine and other antiarrhythmic agents in the same settings.”

Resuscitation