Hemodynamic effects of tracheal administration of vasopressin in dogs

Background: Intravenous administration of vasopressin during cardiopulmonary resuscitation (CPR) has been shown to be more effective than optimal doses of epinephrine. Earlier studies had been performed on a porcine model, but pigs produce lysine vasopressin hormone, while humans and dogs do not. This study was designed to compare the effects of tracheal vasopressin with those of NaCl 0.9% (placebo) on haemodynamic variables in a dog model. Methods: Five dogs were allocated to receive either vasopressin 1.2 U/kg or placebo (10 ml of NaCl 0.9%) via the tracheal route after being anesthetized and ventilated. Haemodynamic variables were determined and arterial blood gases were measured. Results: All animals of the vasopressin group demonstrated a significant increase of the systolic (from 135 ± 7 to 165 ± 6 mmHg, P < 0.05), diastolic (from 85 ± 10 to 110 ± 10 mmHg, P < 0.05) and mean blood pressure (from 98.5 ± 3 to 142.2 ± 5, P < 0.05). Blood pressure rose rapidly and lasted for more than an hour (plateau effect). Heart rate decreased significantly following vasopressin (from 54 ± 9 to 40 ± 5 beats per min, P < 0.05) but not in the placebo group. These changes were not demonstrated with placebo injection. Conclusion: Tracheal administration of vasopressin was followed by significantly higher diastolic, systolic and mean blood pressures in the vasopressin group compared with the placebo group. Blood gases remained unchanged in both groups. Vasopressin administered via the trachea may be an acceptable alternative for vasopressor administration during CPR, when intravenous access is delayed or not available, however, further investigation is necessary.