Effects of epinephrine on intestinal oxygen supply and mucosal tissue oxygen tension in pigs

Objective: To study the effects of increasing dosages of epinephrine given intravenously on intestinal oxygen supply and, in particular, mucosal tissu e oxygen tension in an autoperfused, innervated jejunal segment. Design: Prospective, randomized experimental study. Setting: Animal research laboratory. Subjects: Domestic pigs. Interventions: Sixteen pigs were anesthetized, paralyzed, and normoventilat ed. A small segment of the jejunal mucosa was exposed by midline laparotomy and antimesenteric incision. Mucosal oxygen tension was measured by using Clark-type surface oxygen electrodes. Microvascular hemoglobin oxygen satur ation and microvascular blood flow (perfusion units) were determined by tis sue reflectance spectrophotometry and laser-Doppler velocimetry. Systemic h emodynamics, mesenteric-venous acid-base and blood gas variables, and syste mic acid-base and blood gas variables were recorded. Measurements were perf ormed after a resting period and at 20-min intervals during infusion of inc reasing dosages of epinephrine (n = 8; 0.01, 0.05, 0.1,0.5, 1, and 2 mug kg -l min-l) or without treatment (n = 8). In addition, arterial and mesenteri c-venous lactate concentrations were measured at baseline and at 60 and 120 mins. Measurements and Main Results: Epinephrine infusion led to significant tach ycardia; an increase in cardiac output, systemic oxygen delivery, and oxyge n consumption; and development of lactic acidosis. Epinephrine significantl y increased jejunal microvascular blood flow (baseline, 267 +/- 39 perfusio n units; maximum value, 443 +/- 35 perfusion units) and mucosal oxygen tens ion (baseline, 36 +/- 2.0 torr [4.79 +/- 0.27 kPa]; maximum value, 48 +/- 2 .8 torr [6.39 +/- 0.37 kPa]) and increased hemoglobin oxygen saturation abo ve baseline. Epinephrine increased mesenteric venous lactate concentration (baseline, 2.9 +/- 0.6 mmol.L-1; maximum value, 5.5 +/- 0.2 mmol.L-1) witho ut development of an arterial-mesenteric venous lactate concentration gradi ent. Conclusions: Epinephrine increased jejunal microvascular blood flow and muc osal tissue oxygen supply at moderate to high dosages. Lactic acidosis that develops during infusion of increasing dosages of epinephrine is not relat ed to development of gastrointestinal hypoxia.