Effects of norepinephrine and phenylephrine on intestinal oyxgen supply and mucosal tissue oxygen tension

Objectives: To investigate effects of intravenous norepinephrine (NE) and p henylephrine (PE) on intestinal oxygen supply in an autoperfused, innervate d jejunal segment. Design and setting: Prospective, randomized animal study in an animal resea rch laboratory. Materials and methods: In 24 anesthetized and normoventilated pigs a segmen t of the jejunal mucosa was exposed by midline laparotomy and antimesenteri c incision. Mucosal oxygen tension (PO(2)muc; Clarktype surface oxygen elec trodes), microvascular hemoglobin oxygen saturation (HbO(2), tissue reflect ance spectrophotometry), and microvascular blood flow (perfusion units, PU; laser Doppler velocimetry), systemic hemodynamics, mesenteric-venous acid base and blood gas variables, and systemic acid base and blood gas variable s were recorded after a resting period and at 20-min intervals during infus ion of NE (0.01, 0.05, 0.1, 0.5, 1, 2 mu gxkg(-1)xmin(-1); n = 8) or PE (0. 1, 0.5, 1, 2, 5, 10 mu gxkg(-1)xmin(-1); n = 8) and in controls (n = 8) wit hout treatment. Results: NE infusion led to significant tachycardia, an increase in cardiac output, and systemic oxygen delivery and consumption while PE progressivel y increased mean arterial pressure with only small effects on systemic bloo d flow. NE or PE infusion did not affect mesenteric venous oxygen tension ( baseline: PE 53 +/- 5, NE, 52 +/- 4.2 mmHg), mesenteric oxygen extraction r atio (baseline: PE 0.29 +/- 0.08, NE 0.3 +/- 0.06), jejunal microvascular b lood flow (baseline: PE 254 +/- 127, NE 282 +/- 72 PU), PO(2)muc (baseline: PE 31 +/- 9.1, NE 33 +/- 11 mmHg), and HbO(2) (base line: PE 52 +/- 9.6 %, NE 58 +/- 11.6%). Conclusion: Despite major differences in systemic hemodynamics jejunal tiss ue oxygen supply is not affected by progressively increasing intravenous in fusion of norepinephrine and phenylephrine.