Dopamine under alpha1-blockade, but not dopamine alone or fenoldopam, increases depressed gastric mucosal oxygenation.
OBJECTIVE
To compare the effects of dopamine, both in the presence and absence of alpha1-blockade, and fenoldopam on microvascular gastric mucosal oxygenation and systemic oxygen transport under compromised circulatory conditions, both without and with fluid resuscitation.


METHODS
Randomized controlled animal study.


METHODS
University department of anesthesiology.


METHODS
Eight anesthetized dogs with chronically implanted ultrasound flow probes around the pulmonary artery for continuous measurement of cardiac output.


METHODS
On different days, the dogs received in random order either dopamine (2.5 and 5.0 microg.kg(-1).min(-1), with or without alpha1-blocker pretreatment), the selective DA1-agonist fenoldopam (0.1 and 1.0 microg.kg(-1).min(-1), with and without DA1-blocker pretreatment), or saline (control). These interventions were performed under compromised cardiocirculatory conditions (induced by ventilation with positive end-expiratory pressure [PEEP] of 10 cm H2O), both without and with fluid resuscitation.


RESULTS
We continuously measured regional microvascular hemoglobin saturation (microHbO2) in gastric mucosa by reflectance spectrophotometry and systemic oxygen transport ([U1E0A]O2). Ventilation with PEEP significantly decreased [U1E0A]O2 (from 19 +/- 2 to 9 +/- 1 mL.kg(-1).min(-1), mean +/- sem) and gastric mucosal microHbO2 (from 57 +/- 2% to 37 +/- 3%). Fluid resuscitation restored [U1E0A]O2 back to baseline (from 9 +/- 1 to 19 +/- 2 mL.kg(-1).min(-1)) but only partially restored microHbO2 (from 37 +/- 3% to 50 +/- 4%). Under both conditions, dopamine with and without alpha1-blockade significantly increased [U1E0A]O2 (by about 5 mL.kg-1.min-1 in the nonresuscitated state and 10 mL.kg-1.min-1 in the fluid resuscitated state, respectively), but only dopamine in the presence of alpha1-blockade also significantly increased gastric mucosal microHbO2 (by 5 +/- 1% and 7 +/- 2% in the nonresuscitated and fluid resuscitated states, respectively). Fenoldopam under all study conditions did not significantly affect [U1E0A]O2 or microHbO2, either in the presence or absence of DA1-blockade.


CONCLUSIONS
During compromised cardiocirculatory conditions, alpha1-receptor activation during dopamine infusion prevented an increase in gastric mucosal oxygenation. Furthermore, selective DA1-stimulation (by fenoldopam) was insufficient to overcome the PEEP-induced depression of microHbO2. The responses of gastric mucosal oxygenation did not parallel changes in systemic oxygen transport. These findings were independent of fluid resuscitation.
Schwarte
Lothar A
LA
Department of Anesthesiology, University Hospital of Duesseldorf, Germany. SchwarteLothar@aol.com
Picker
Olaf
O
Schindler
Achim W
AW
Fournell
Artur
A
Scheeren
Thomas W L
TW
D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D018818:Fenoldopam / Q000494:pharmacology*; D005753:Gastric Mucosa / Q000098:blood supply*; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D011175:Positive-Pressure Respiration; D011336:Probability; D011897:Random Allocation; D012039:Regional Blood Flow; D012680:Sensitivity and Specificity
D018492:Dopamine Antagonists; D018818:Fenoldopam; D004298:Dopamine