Effect of vasopressin and norepinephrine on renal blood flow in a canine model of raised intra-abdominal pressure

Introduction

Increasing intra-abdominal pressure (IAP) is associated with a decrease in renal blood flow [1]. Abdominal perfusion pressure (APP) is calculated as the mean arterial pressure (MAP) – IAP. We investigated whether restoration of APP in dogs with the use of vasopressin (VP) and norepinephrine (NE) could increase renal blood flow under conditions of raised IAP.

Methods

Ten mongrel dogs (average weight 20 ± 3 kg) were anaesthetized and mechanically ventilated with 100% oxygen and halothane. The IAP was altered by filling a 3 l intraperitoneal bag with varying volumes of normal saline and the IAP was measured by the urinary catheter technique. Ultrasonic transit-time flow probes were placed around the ascending aorta and left renal artery. After baseline readings, the IAP was increased to 10, 20 and 30 mmHg. Preload was maintained by a continuous infusion of 500 ml/hour normal saline. At each level of IAP, the MAP was restored to achieve the baseline APP with VP and NE infusion, followed by decompression. The MAP, IAP, and renal blood flow (RBF) were measured.

Results

The average baseline MAP was 75 ± 10 mmHg. The mean baseline RBF was 180 ± 60 ml/min. Incrementally increasing the IAP from baseline resulted in a progressive decrease in RBF (Table 1). The RBF (ml/min) achieved following the use of NE and VP to return the APP to the baseline APP of 70–75 mmHg is shown (Table 1). RBF after decompression (no vasopressor) is also shown.

Table 1

Conclusion

In dogs an increase in IAP results in an incremental decrease in RBF. Using VP to restore the APP to baseline does not reverse the decrease in RBF. At moderate levels of IAH, using NE improves restoring APP to baseline and improves RBF, but does not return it to baseline values.