Abstract
BackgroundThe aim of the study was to describe the effects of intra-abdominal hypertension (IAH) on regional and microcirculatory intestinal blood flow, renal blood flow, and urine output, as well as their response to increases in blood pressure induced by norepinephrine.MethodsThis was a pilot, controlled study, performed in an animal research laboratory. Twenty-four anesthetized and mechanically ventilated sheep were studied. We measured systemic hemodynamics, superior mesenteric and renal blood flow, villi microcirculation, intramucosal-arterial PCO2, urine output, and intra-abdominal pressure. IAH (20 mm Hg) was generated by intraperitoneal instillation of warmed saline. After 1 h of IAH, sheep were randomized to IAH control (n = 8) or IAH norepinephrine (n = 8) groups, for 1 h. In this last group, mean arterial pressure was increased about 20 mm Hg with norepinephrine. A sham group (n = 8) was also studied. Fluids were administered to prevent decreases in cardiac output. Differences between groups were analyzed with two-way repeated measures of analysis of variance (ANOVA).ResultsAfter 2 h of IAH, abdominal perfusion pressure decreased in IAH control group compared to IAH norepinephrine and sham groups (49 ± 11, 73 ± 11, and 86 ± 15 mm Hg, P < 0.0001). There were no differences in superior mesenteric artery blood flow, intramucosal-arterial PCO2, and villi microcirculation among groups. Renal blood flow (49 ± 30, 32 ± 24, and 102 ± 45 mL.min−1.kg−1, P < 0.0001) and urinary output (0.3 ± 0.1, 0.2 ± 0.2, and 1.0 ± 0.6 mL.h−1.kg−1, P < 0.0001) were decreased in IAH control and IAH norepinephrine groups, compared to the sham group.ConclusionsIn this experimental model of IAH, the gut and the kidney had contrasting responses: While intestinal blood flow and villi microcirculation remained unchanged, renal perfusion and urine output were severely compromised.Electronic supplementary materialThe online version of this article (doi:10.1186/s40635-015-0046-1) contains supplementary material, which is available to authorized users.
Highlights
The aim of the study was to describe the effects of intra-abdominal hypertension (IAH) on regional and microcirculatory intestinal blood flow, renal blood flow, and urine output, as well as their response to increases in blood pressure induced by norepinephrine
Systemic effects There were no differences in mean arterial pressure (MAP) at baseline and at 60 min among groups; but at 120 min, MAP was lower in the IAH control group compared to the others
At 120 min, abdominal perfusion pressure (APP) in IAH norepinephrine group increased to higher values than in IAH control group, but not different from the sham group
Summary
The aim of the study was to describe the effects of intra-abdominal hypertension (IAH) on regional and microcirculatory intestinal blood flow, renal blood flow, and urine output, as well as their response to increases in blood pressure induced by norepinephrine. Some studies found severe reductions in gut perfusion induced by an IAP of 15 mm Hg maintained for 2 h [7], while others showed preservation of intestinal blood flow after 3 h of 20 mm Hg [8]. These contradictory findings might be related to different models of IAH and to the particular behavior of cardiac output in each animal model. The decrease in regional and tissue intestinal blood flow might not be completely dissociated from the alterations in systemic hemodynamics
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