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 det ect differences in oxyhaemoglobin signal when applied to the abdomens of ne onates 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 ident ified, neonates with acute abdomens referred for surgery and those with nor mal abdomens admitted for medical reasons. Interventions: Tissue oxygenation indexes (TOI) of cerebral and splanchnic regions were measured using near infrared spectroscopy (NIRS) and their rel ative values expressed as a cerebro-splanchnic oxygenation ratio (CSOR). Me asurements were made on admission or immediately prior to surgery and subse quently 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 fou r with necrotising enterocolitis (NEC), 29 controls with normal abdomens an d one with cerebral hypoxic ischaemic injury. Median CSOR for the control g roup was 0.96 (interquartile range 0.83-1.02) whereas the acute abdomen gro up had a significantly lower median CSOR value of 0.66 (0.45-0.69) (p < 0.0 01). 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 isc haemia as less than 0.75, intestinal ischaemia was identified with a positi ve predictive value of 0.75 (0.43-0.95) and excluded with a negative predic tive value of 0.96 (0.81-1.0). This was a better performance than using abd ominal 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 d etect when splanchnic ischaemia develops. CSOR had a 90 % (56-100 %) sensit ivity 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.