Evaluation of the effects of medial saphenous venous pressures as an indirect method of measurement of intra-abdominal pressures in the horse.

Abstract

To evaluate the effect of changes in intra-abdominal pressure (IAP) on medial saphenous venous pressure (MSVP) and hemodynamics in normal horses. Experimental, in-vivo study. University Teaching Hospital. Convenience sample of 7 mixed breed horses; 5 geldings, and 2 mares. 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 20mm Hg over 30 minutes, and maintained at that pressure for 30 minutes to evaluate the effect of sustained intra-abdominal hypertension. The MSVP and vital parameters were recorded, along with direct arterial blood pressure from the transverse facial artery. As IAP increased, MSVP increased in a stepwise manner, in concert with changes in IAP. The consistency in measurement between MSVP and IAP was high (intraclass correlation coefficient=0.92; P<0.001) and repeated measures correlation was excellent (r=0.98; P<0.001). Heart rate was unchanged over the course of the experiment (P=0.09), however, respiratory rate increased with increasing IAP (P<0.001). Arterial blood pressure also increased with insufflation (P<0.001), with a significant difference at an IAP of 15mm Hg (P=0.04). This report provides preliminary data demonstrating a strong correlation between equine MSVP and changes in IAP, similar to that observed in other species. Further investigations are needed to evaluate this relationship, and to confirm these results in clinical patients.