OP21 - Urine partial oxygen pressure as early marker of acute kidney injury after paediatric cardiac surgery

Abstract

Acute kidney injury (AKI) is the common and serious complication which occurs in open-heart surgery (HS) using cardiopulmonary bypass (CPB). The renal medulla is one the first affected tissues from decreased perfusion during the procedure of cardiopulmonary bypass. Partial pressure of the urine taken from the renal pelvis is related to the perfusion of renal medulla was shown. Neutrophil gelatinase-associated lipocalin (NGAL) is accepted as an early biomarker and a predictor of AKI in a variety of clinical settings. We sought to evaluate the relationship between urine pO2 and kidney function-injury biomarkers and contribution of glycocalyx derangement after paediatric cardiac surgery. Twenty paediatric patients with normal preoperative renal function as assessed by the creatinine level, undergoing HS with CPB were included in this prospective clinical observational study. Besides routine hemodynamics and cerebral tissue oxygen saturation monitoring, patients were assessed for the partial pressure of the bladder urine (PuO2) and renal tissue oxygen saturation monitoring by NIRS intraoperatively (after induction, before CPB, after CPB) and postoperative (admission of ICU, 3rd, 6th, 9th, 12th in ICU) periodically. Additionally, syndecan-1, hyaluronan, cystatin-c, and NGAL levels were measured in plasma and urine samples. PuO2 was found wavy throughout the operation (p>0.05) and increased at the 6th (p<0.05), 9th (p<0.001) and 12th (p<0.001) hours of ICU admission. Renal tissue oxygen saturation (rSO2) monitored by NIRS was found stable throughout the operation and postoperative 12 hours. Plasma NGAL and hyaluronan levels were significantly found to rise at the 12th hour of ICU admission compared to the anaesthesia induction (p<0.001); meanwhile syndecan and cystatin-c were remained constant (p>0.05). A significant correlation between PuO2 and other measurements as renal tissue oxygen saturation (rSO2), arterial blood lactate, NGAL and hyaluronan levels was not determined at any time points. Coexistence of urine pO2 fluctuations and increment of plasma NGAL-hyaluronan levels suggest that urine pO2 could be early marker of kidney injury in paediatric patients undergoing HS. Further investigation in the role of urine pO2 plays in ischemic organ injury and its potential diagnostic implications is needed. 1. Clin Exp Pharmacol Physiol. 2008 Sep;35(9):1109-12