Background: Increased intra-abdominal pressure (IAP) (pneumoperitoneum) during laparoscopic surgery may result in adverse effects on kidney function. The mechanisms underlying this phenomenon have not been fully determined.
Objective: The present study was designed to: (1) investigate the effects of incremental increases in IAP on renal function in normal rats and (2) evaluate whether the nitric oxide (NO) system is involved in renal dysfunction characterizing pneumoperitoneum.
Methods: Male rats were organized into two groups. The first group was subjected to IAP of 0 (baseline), 7 or 14 mmHg, over 1 h for each pressure, followed by a deflation period of 60 min (recovery). Two additional groups were pretreated with: (1) non-depressor dose of nitroglycerine (NTG) and (2) nitro-L-arginine-methylester (L-NAME), an NO synthase inhibitor, before applying 14 mmHg for 1 h. Urine flow rate (V), Na+ excretion (U(Na)V), glomerular filtration rate (GFR), renal plasma flow (RPF), and blood pressure were determined throughout the experiments.
Results: There were no significant changes in V, U(Na)V, GFR, and RPF during 7 mmHg insufflation. However, significant reductions in these parameters were observed during 14 mmHg: V from 8.49 +/- 0.92 to 6.12 +/- 0.54 microl/min, U(Na)V from 1.29 +/- 0.28 to 0.39 +/- 0.09 microEq/min, and FE(Na) from 0.37 +/- 0.11 to 0.27 +/- 0.04%. These alterations in excretory functions were associated with a considerable decline in GFR from 1.85 +/- 0.09 to 0.88 +/- 0.09 ml/min, p < 0.05, (-46.3 +/- 5.2% from baseline) and RPF from 8.66 +/- 0.62 to 4.33 +/- 0.49 ml/min, p < 0.05, (-51.93 +/- 5.24% from baseline), without a significant change in mean arterial blood pressure (MAP). When the animals were pretreated with NTG, the adverse effects of pneumoperitoneum on V, U(Na)V, GFR, and RPF were substantially improved, suggesting that NO system plays a beneficial counter-regulatory role during laparoscopy. In line with this notion, pretreatment with L-NAME remarkably aggravated pneumoperitoneum-induced renal hypoperfusion and dysfunction.
Conclusion: Decreased renal perfusion and function are induced by IAP pressure of 14 mmHg. These adverse effects are probably related to interference with the NO system, and could be partially ameliorated by pretreatment with NTG.