Dobutamine, not dopamine, improves gastric intramucosal pH during resuscitation from hemorrhagic shock in dogs.

Abstract

To the Editor: Preservation of splanchnic perfusion is considered an important goal of resuscitation because the derangement of gastrointestinal mucosal perfusion is the main cause of the progression of hemorrhagic shock into an irreversible state.1 When measuring systemic oxygenation only, the possibility of overlooking serious gastrointestinal mucosal ischemia is high, hence the need to monitor mucosal oxygenation selectively.2 We examined the effects of dopamine or dobutamine on the recovery of mucosal perfusion in a canine model of hemorrhagic shock. Thirty dogs were bled to a mean arterial pressure of 40 mmHg and maintained in this state for 90 min. After volume resuscitation, dogs were randomized to receive dopamine (DP, 4 μg·kg–1·min–1, n=10 ), dobutamine (DB, 7 μg·kg–1·min– 1, n=10 ), or no drug (C, n=10 ) and followed up for 180 min. The gastric intramucosal PCO2 and pH (pHi) were measured with a Trip® NGS catheter (Datex, Engstrom, Finland). The cardiac index was maintained higher with DP than with DB or C after resuscitation. However, the pHi was maintained higher with DB than with DP or C, while DP was not significantly different from C (Figure). We conclude that low-dose dopamine has little effect on the restoration of gastrointestinal mucosal oxygenation despite a significant improvement of cardiac index, and that dobutamine is effective to improve gastrointestinal mucosal oxygenation after volume resuscitation from hemorrhagic shock. This result may be explained by the dopamineinduced redistribution of perfusion away from the mucosal area3 and an increase in oxygen requirements greater than supply.4 Dobutamine may selectively dilate the intramucosal vessels to direct perfusion towards the mucosal and/or increase oxygen delivery more than oxygen requirements.5