Influence of intra-abdominal hypertension on renal artery and vein flow in the porcine kidney

Background

In man, intra-abdominal hypertension (IAH) has been shown to impair renal perfusion due to decreased renal artery flow (RAF). Renal venous hypertension and decreased renal venous flow (RVF) are other potential contributing mechanisms. We used a porcine model of IAH to evaluate the role of RVF and renal venous pressure (RVP) in renal dysfunction due to IAH.

Methods

We studied nine anesthetized and ventilated pigs in the prone position (46 ± 3 kg) after insertion of a renal vein catheter and after placement of flow probes around the renal artery and vein. Following baseline measurements, RAF, RVF and RVP were measured during incremental intra-abdominal pressure (IAP) levels (10, 20 and 30 mmHg during 45 min each) by infusing warmed saline into the peritoneal cavity. Standard hemodynamic parameters, obtained from Swan-Ganz monitoring, were also recorded.

Results

RAF and RVF decreased in parallel at an IAP of 20 and 30 mmHg (Table 1) without dropping to zero flow. RVP paralleled the increase in IAP, but always exceeded IAP by 3–4 mmHg. Renal perfusion pressure (RPP = MAP – RVP) decreased significantly with increasing IAP, in spite of significantly increased MAPs. RAF/ CO decreased from 44% to 34%, indicating a flow redistribution away from the kidney in IAH. In parallel, renal vascular resistance (RVR = RPP / RAF) increased from 0.75 to 1.1 mmHg.min/ml with increasing IAP (Table 1).

Table 1

Conclusion

Decreased renal perfusion in IAH is not only due to decreased RAF, but also due to a regional effect of redistribution away from the kidney. Renal venous hypertension can account for this observation.