Wyer PC, Perera P, Jin Z, et al: Vasopressin or Epinephrine for Out-of-Hospital Cardiac Arrest. Annals of Emergency Medicine. 2006. 48:86–97.
The authors of this study attempted to review the world s literature comparing vasopressin and epinephrine for out-of-hospital cardiac arrest. They limited their scope to studies that measured survival to discharge and neurologic outcome. Using a very exhaustive search and stringent criteria, they reviewed in great detail three high-quality randomized trials and one meta-analysis (a comparison of many studies). They determined that there was no evidence to support the benefit of vasopressin over epinephrine.
As a system medical director, I know full well the pressure to make changes to current drug regimens to be compliant with a perceived standard of care. It s especially true for cardiac arrest treatment because of the publicity associated with the 2005 AHA guidelines. However, the guidelines state that vasopressin may be substituted for epinephrine not must be. There are practical advantages to giving a single dose of 40 units of vasopressin for V-tach/fib and asystole, and I m all for practicality in the controlled chaos of the cardiac arrest scene. Also, animal data indicates increased coronary artery and cerebral perfusion pressures with the use of vasopressin over epinephrine. But the drug is more expensive, and controversy surrounds the issue of what to do if the patient is unresponsive to vasopressin.
This paper might provide your medical director with the necessary science to help them decide whether to add vasopressin, but it s important to recognize its limitations. The authors only examined research that measured the rate of survival to hospital discharge. As we have seen in many recent studies regarding advances in cardiac arrest care, this is not necessarily the best outcome on which to base prehospital care.
In EMS, a successful resuscitation is one in which the patient arrives at the hospital with a pulse or attains one soon afterward and is admitted. However, many other factors affect whether a patient survives to discharge, including the decision to remove them from life support or the development of medical complications, such as renal failure or sepsis.
Although studies like this one are helpful in defining the current state of the science, they do little to provide the practical knowledge necessary to make changes to EMS practice that measures success in different terms. Further complicating the understanding of the significance of such studies is that they are based on cardiac arrest care using the old 2000 AHA guidelines. Who knows what, if any, differences we may detect between the vasopressin and epinephrine when used with the new pump hard, pump fast protocols.