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Abstract & Commentary
Source: Wenzel V, et al, for the European Resuscitation Council Vasopressor during Cardiopulmonary Resuscitation Study Group. A comparison of vasopressin and epinephrine for out-of-hospital cardiopulmonary resuscitation. N Engl J Med 2004;350:105-113.
From 1999 to 2002, these Austrian investigators randomly assigned adults with out-of-hospital cardiac arrest to receive two injections of either 40 IU of vasopressin or 1 mg of epinephrine, followed by additional treatment with epinephrine, if needed. The primary endpoint was survival to hospital admission, and the secondary endpoint was survival to discharge from the hospital. In all, 1186 patients were analyzed; 589 were assigned to receive vasopressin, and 597 to receive epinephrine. Each group had similar clinical profiles. Cardiopulmonary resuscitation was documented according to the Utstein style. Vasopressin and epinephrine fared similarly when used to treat ventricular fibrillation and pulseless electrical activity. However, among patients with asystole, vasopressin use resulted in higher rates of hospital admission (29.0% vs 20.3 % in the epinephrine group, P = 0.02) and hospital discharge (4.7 % vs. 1.5 %, P = 0.04). Additionally, when vasopressin had no immediate effect, but was followed by additional treatment with epinephrine in asystole patients (n = 732), patients experienced significant improvement in rates of survival to hospital admission and hospital discharge (hospital admission rate 25.7 % for vasopressin plus epinephrine, vs 16.4 % for epinephrine plus epinephrine, P = 0.002; hospital discharge rate 6.2 % vs 1.7 %; P = 0.002). Cerebral performance was similar in both groups.
The authors conclude that the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity, but vasopressin was superior to epinephrine in patients with asystole. Vasopressin followed by epinephrine may be more effective than epinephrine alone in the treatment of refractory cardiac arrest.
Commentary by Richard Hamilton, MD, FAAEM, ABMT
Vasopressin, also known as antidiuretic hormone, offers many advantages in cardiac arrest. Vasopressin causes vasoconstriction via peripheral vasopressin receptors, even during hypoxia and severe acidosis. These effects are greatest in splanchnic, muscular, and cutaneous vessels, while paradoxical vasodilatation is seen in pulmonary, coronary, and the vertebrobasilar circulation. Critical care specialists have used vasopressin in shock resistant to norepinephrine because it increases systemic vascular resistance and decreases cardiac output. This allows for a clinical effect at a lower catecholamine dose. The advantages of a drug of this nature in cardiac arrest in the field are intuitive. This study nicely demonstrates that in the case of asystole, vasopressin may have an immediate effect to restore spontaneous circulation and improve the chances that a patient will survive. Additionally, there may be value in developing vasopressin as a primer drug for making a patient more sensitive to the effects of catecholamine, especially in asystole. Certainly, the place to use this approach is in the field. Frankly, even a small improvement in the chances for patient survival from asystole would be welcome.
Dr. Hamilton, Associate Professor of Emergency Medicine, Residency Program Director, Department of Emergency Medicine, Drexel University College of Medicine, Philadelphia, PA, is on the Editorial Board of Emergency Medicine Alert.