Effects of arginine–vasopressin on jejunal mucosal oxygen supply in healthy pigs

Introduction

Arginine–vasopressin (AVP) may promote intestinal ischemia. We studied the effects of increasing doses of AVP on mucosal tissue oxygen tension (PO₂muc), microvascular haemoglobin oxygen saturation (HbO₂), and microvascular blood flow (PU) in a jejunal segment.

Methods

A small segment of jejunal mucosa was exposed by midline laparotomy and antimesenteric incision in 16 anesthetized, paralyzed, and normoventilated pigs. PO₂muc (Clark-type surface oxygen electrodes), HbO₂ (tissue reflectance spectrophotometry), and PU (laser-Doppler velocimetry) were measured. Systemic haemodynamics, mesenteric–venous acid–base and blood gas variables, and systemic acid–base and blood gas variables were recorded. Measurements were performed after a stabilizing period and baseline measurements at 20-min intervals during increasing dosages of AVP (AVP group; n = 8; 0.007, 0.014, 0.029, 0.057, 0.114, and 0.229 U/kg/hour) or saline placebo (CTRL group; n = 8).

Results

AVP infusion lead to a significant decrease in cardiac index (121 ± 31 ml/kg/min vs 77 ± 27 ml/kg/min) and systemic oxygen delivery (13.7 ± 3.0 ml/kg/min vs 9.1 ± 3.4 ml/kg/min) concomitant with an increase in systemic oxygen extraction ratio (31 ± 4% vs 48 ± 10%). AVP decreased significantly microvascular blood flow (133 ± 47 PU vs 82 ± 35 PU), mesenteric venous oxygen tension (25.6 ± 7.1 mmHg vs 6.9 ± 2.4 mmHg) and microvascular hemoglobin oxygen saturation (51.3 ± 9.0% vs 26.4 ± 12.2%) without a statistical increase in mesenteric venous lactate concentration (2.3 ± 0.8 mmol/l vs 3.4 ± 0.7 mmol/l).

Conclusion

Intravenously administered AVP decreases in a dose-dependent manner intestinal oxygen supply and mucosal tissue oxygen tension via reduction in microvascular blood flow in healthy pigs.