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221 Oliguria in paediatric spinal instrumentation surgery: is it acute kidney injury (aki)?

Purpose of study A recent retrospective study found that 20% of paediatric spinal surgery patients had post-operative oliguria, suspected to be related to AKI. We aimed to determine if oliguria in this population is related to AKI by comparing urine biomarker neutrophil gelatinase-associated lipocalin (NGAL) concentrations in patients with and without post-operative oliguria. Methods used This is an ongoing single centre prospective cohort study. To date, we have enrolled 19 children (mean age 14.1 years, SD 3.2 years; 8 males) undergoing spinal surgery for non-idiopathic scoliosis repair from Jul 2016-Aug 2017. Hourly urine output (U/O) was recorded until post-op day (POD) 3. Stage 1 and 2 oliguria were defined as <0.5 cc/kg/hr for at least 6 hours and 12 hours respectively using KDIGO (Kidney Disease: Improving Global Outcomes) U/O AKI criteria. Urine NGAL, corrected for urine creatinine, was collected at 4 time points: pre-op, 3 hours intra-op, surgery end, and 24 hours post-surgery start time. The association of urine NGAL and oliguria was determined using Area under the Receiver Operating Characteristic curve (AUC). Summary of results 14/19 patients (74%) met oliguria criteria (n=7 Stage 1, n=7 Stage 2). No patients met serum creatinine criteria for AKI. Urine NGAL concentrations did not show an appreciable rise at any time point. Creatinine-corrected urine NGAL was poorly associated with oliguria at all time points (AUC range 0.44–0.67). Mean cumulative fluid balance peaked on POD 2 for non-oliguric patients (+2.6 L, SD 1.2 L) and peaked on POD 3 for oliguric patients (+3.4 L, SD 2.7 L). Mean cumulative fluid balance by POD 3 was higher for oliguric patients (+3.4 L, SD 2.7 L) than for non-oliguric patients (+2.3 L, SD 1.7 L), but was not statistically significant (p=0.475). Conclusions Preliminary biomarker results suggest that post-op oliguria in spinal surgery patients may occur due to reasons other than AKI. Regardless of the cause of oliguria, strategies for improved fluid management post-op should be implemented to prevent fluid overload and its associated complications for these patients.