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Evaluation of the effects of intraabdominal hypertension on equine central venous pressure.

OBJECTIVE
To evaluate the effect of changes in intraabdominal pressure (IAP) on central venous pressure (CVP) in normal horses.


DESIGN
Experimental, in vivo study.


SETTING
University Teaching Hospital.


ANIMALS
Convenience sample of 7 mixed breed horses-5 geldings and 2 mares.


INTERVENTIONS
Pneumoperitoneum was induced in horses under standing sedation with carbon dioxide gas using a laparoscopic insufflator for a total of 60 minutes to simulate clinical elevation in IAP. Pressure was increased stepwise to 20 mm Hg over 30 minutes, and maintained at that pressure for 30 minutes to evaluate the effect of sustained intraabdominal hypertension. CVP was obtained from the cranial vena cava, concurrent with pressure obtained from the peritoneal cavity.


MEASUREMENTS AND MAIN RESULTS
CVP increased as IAP increased up to 12 mm Hg, and declined as IAP increased further. The changes in CVP over time were significantly different (P < 0.03). Repeated measures correlation was positive, and highest, for mean CVP as IAP increased from 0 to 12 mm Hg (r = .70; 95% CI, .43-.85; P < 0.0001). Correlation of mean CVP with insufflation pressure became negative as IAP increased further from 15 to 20 mm Hg (r = -.47; 95% CI, -.66 to -.21; P = 0.0006).


CONCLUSIONS
This report provides preliminary data demonstrating a biphasic trend in equine CVP caused by changes in IAP, similar to that observed in other species. Further investigations are needed to evaluate this trend and to confirm these results in clinical patients.