Effects of dopamine in lung-transplanted pigs at 32 degrees C

Background: We have used hypothermia successfully in patients with acute re spiratory failure after lung transplantation. However, we have observed tha t dopamine may cause a substantial decrease in mean arterial pressure (MAP) in hypothermic subjects. Furthermore, a dopamine-induced increase in pulmo nary vascular resistance (PVR) has been reported in the literature, and thi s could aggravate the increase in PVR which is often seen both in the early postoperative phase after lung transplantation, and during hypothermia. We thus hypothesized that dopamine would decrease MAP and increase PVR in hyp othermic lung-transplanted subjects. Methods: Left single lung transplantation combined with right pneumonectomy was performed in 6 pigs anesthetized with ketamine and midazolam and muscl e relaxed with pancuronium. After an observation period of 24 h, the effect of dopamine infused at 5 and 12 mu g . kg(-1) . min(-1) was studied in nor mothermia (38 degrees C) and after cooling by cold-water immersion to 32 de grees C. Results: Systemic vascular resistance index (SVRI) increased and cardiac in dex (CI) decreased in hypothermia. Dopamine decreased SVRI and increased CI , both in normothermia and at 32 degrees C. MAP decreased during infusion o f dopamine in hypothermia. Dopamine had no effect on the pulmonary vascular resistance index (PVRI). Conclusion: The results suggest that dopamine may be used to increase cardi ac output after lung transplantation in moderate hypothermia as well as in normothermia, but one should be aware that dopamine may cause a substantial decrease in blood pressure, depending on the prevailing hemodynamic condit ions at the start of its administration.