Cerebro-splanchnic oxygenation ratio (CSOR) using near infrared spectroscopy may be able to predict splanchnic ischaemia in neonates

Objective: To investigate whether near infrared spectroscopy (NIRS) can detect differences in oxyhaemoglobin signal when applied to the abdomens of neonates with surgically proven splanchnic ischaemia. Design: Prospective, observational cohort study Setting: Tertiary neonatal referral centre. Patients: Medical and surgical neonates were studied. Two groups were identified, neonates with acute abdomens referred for surgery and those with normal abdomens admitted for medical reasons. Interventions: Tissue oxygenation indexes (TOI) of cerebral and splanchnic regions were measured using near infrared spectroscopy (NIRS) and their relative values expressed as a cerebro-splanchnic oxygenation ratio (CSOR). Measurements were made on admission or immediately prior to surgery and subsequently repeated on a daily basis, whenever possible. until discharge from our unit. The area under the receiver operating characteristic (ROC) curve was evaluated and optimum diagnostic cut-off values determined. Results: Forty neonates were studied: 10 with acute abdomens, including four with necrotising enterocolitis (NEC), 29 controls with normal abdomens and one with cerebral hypoxic ischaemic injury. Median CSOR for the control group was 0.96 (interquartile range 0.83-1.02) whereas the acute abdomen group had a significantly lower median CSOR value of 0.66 (0.45-0.69) (p < 0.001). The area under the ROC was 0.91 (95 % confidence limits 0.78-1.00) for CSOR. Taking a boundary value of CSOR for the prediction of splanchnic ischaemia as less than 0.75, intestinal ischaemia was identified with a positive predictive value of 0.75 (0.43-0.95) and excluded with a negative predictive value of 0.96 (0.81-1.0). This was a better performance than using abdominal TOI alone. Conclusions: By comparing the TOI of cerebral and splanchnic regions it may be possible to establish the presence of normal splanchnic perfusion and detect when splanchnic ischaemia develops. CSOR had a 90 % (56-100 %) sensitivity to detect splanchnic ischaemia in neonates. Further work is necessary to confirm these early findings and establish whether abdominal NIRS has a clinical role in detecting splanchnic ischaemia.