Influence of intra-abdominal hypertension on microvascular flow in the porcine renal cortex

Background

In man, intra-abdominal hypertension (IAH) has been shown to impair renal perfusion. Renal microcirculation is difficult to study in vivo and little is known about the effect of increased intra-abdominal pressure (IAP) on kidney microcirculation. For the first time, we evaluated renal cortex microcirculation with side-stream dark field (SDF) imaging in a porcine model of IAH.

Methods

We studied five anesthetized and ventilated pigs (46 ± 3 kg) during incremental IAP levels (10, 20 and 30 mmHg during 45 min each) by infusing warmed saline into the peritoneal cavity. The renal venous pressure (RVP) was measured with a renal vein catheter. After right mini-lumbotomy and gentle removal of the renal capsule, the SDF device was positioned intermittently on the renal cortex, avoiding pressure artefacts. Subsequently, representative video-clips (10 s) were captured and the microvascular flow index (MFI) was scored blindly by three independent observers, based on the semiquantitative method of Boerma and colleagues [1].

Results

The MFI decreased significantly from 2.51 ± 0.30 to 1.76 ± 0.26 (P < 0.03) when the IAP increased from 10 to 30 mmHg. The RVP increased significantly from 10 ± 4 to 34 ± 5 mmHg (P < 0.00003) with the IAP increasing from 6 to 30 mmHg. There was an inverse correlation (r = -0.63, P < 0.003) between the MFI and RVP (Fig. 1).

Figure 1

Conclusion

Increased IAP impairs renal cortex microcirculation in a porcine model of IAH. Renal venous hypertension may account for this observation.