Increased Intra-Abdominal Pressure during Pneumoperitoneum Stimulates Endothelin Release in a Canine Model

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Abstract
Prolonged pneumoperitoneum during laparoscopic surgery has been associated with oliguria in clinical experimental studies. Although the pathophysiology of this oliguria is thought to be renal parenchymal and venous compression, the role of the potent vasoconstrictor endothelin (ET) has not been studied. The purpose of this study was to investigate the effect of pneumoperitoneum on endothelin release and renal function in a canine model. Two groups of dogs were studied during pneumoperitoneum (Group 1, N = 7) or isolated left renal vein compression (Group 2, N = 6). Urine and plasma samples were collected for urine output, glomerular filtration rate (GFR), urine sodium, and plasma endothelin measurements. In Group 1, GFR fell significantly (p < 0.05) by 49% from a control of 0.88 +/- 0.12 mL/min per gram of kidney weight. Urine volume fell by 79% (p < 0.05) from a control value of 0.014 +/- 0.003 mL/min/gkw. Sodium excretion was decreased by 88%. Sodium reabsorption was significantly enhanced during pneumoperitoneum (99.56 +/- 0.15% v 98.44 +/- 0.25%). Arterial plasma ET concentrations were elevated by 8% during the first 20 minutes of pneumoperitoneum (30.8 +/- 3.6 v 33.3 +/- 3.4 pg/mL; p < 0.05). In Group 2, left renal vein compression resulted in a 31% decrease (p < 0.05) in GFR in the left kidney and a 25% decrease in the right kidney. Urine volume fell by 67% in the left kidney and 40% in the right. Renal venous ET concentrations also increased after renal vein compression. Although the mechanism by which oliguria occurs during pneumoperitoneum is not fully understood, the ET concentration was elevated. Because ET can decrease RBF, GFR, and sodium excretion, it may contribute to the oliguria observed during long periods of pneumoperitoneum.