The Effect on Blood Pressure of Putting Large Doses of Adrenaline into the Airways FREE

Adrenaline, a naturally occurring hormone that raises blood pressure, is used as part of the standard cardiopulmonary resuscitation (CPR) protocol. Adrenaline is usually given through an intravenous catheter, a small tube that is put into a vein. When an intravenous catheter is not available, experts have suggested putting large doses of adrenaline into the bronchial tubes (airways). You do this by putting it through the breathing tube put into a patient's airways during CPR. It has been assumed that adrenaline will be rapidly absorbed from the airways into the bloodstream, but no effects have yet been demonstrated in adult humans.

To learn the actual effects of giving adrenaline through the airway.

Patients who are undergoing CPR are unable to agree to be in a study, so the researchers could not study actual CPR patients. Instead, they studied 34 patients who were having surgery to get an implantable cardioverter defibrillator, a device that treats potentially deadly heart rhythms. All of these patients had severe heart disease; 18 had CPR before surgery.

The study was done while the patients were under general anesthesia for the surgical procedure. The researchers first determined the intravenous dose of adrenaline that would raise the patient's mean arterial pressure (a special measure of blood pressure) by at least 10 mm Hg. Then, whenever a patient's mean arterial pressure decreased below 80 mm Hg during the surgery, the researchers gave the patient a large dose of adrenaline. They gave the adrenaline either through a special catheter inserted deep into the airways (the first 17 patients) or slowly through a breathing tube inserted less deep into the airways (the second 17 patients). Ten forced ventilations distributed adrenaline deep into the lungs. In 13 patients, the researchers measured the blood levels of adrenaline.

Mean arterial pressure increased in all patients who got airway adrenaline, whether it was introduced deep in the airways or less deep. The blood pressure and the level of adrenaline in the bloodstream increased more with airway adrenaline than with intravenous adrenaline.

The study included only a small number of patients, none of whom were undergoing CPR. The results might be different in actual CPR situations, since blood circulation is less effective during CPR than during anesthesia.

This study supports the international recommendation to give adrenaline through the airway when an intravenous catheter is not available. Because no potentially deadly heart rhythms occurred, even larger adrenaline doses might be warranted.