Near-infrared spectroscopy combined with partial jugular venous occlusion (JVO) offers promise for determining cerebral venous saturation (CSvO 2 ) in sick preterm infants, but has not been validated in the newborn brain or under conditions of hypoxaemia. We assessed the accuracy of the CSvO 2 estimate using cerebral venous oxygen saturation in superior sagittal sinus blood (SSSO 2 ) as the 'gold standard'. Comparisons were made in seven newborn lambs over a wide range of arterial oxygen saturations (SaO 2 ) of 20% to 100%. Overall, median (range) CSvO 2 was 49.8% (10.6% to 88.5%), whereas SSSO 2 was 45.5% (4.3% to 76.6%); Bland-Altman analysis revealed a mean difference (CSvO 2 ÀSSSO 2 ) of 5.1% and limits of agreement of 627.4%. The change in cerebral blood volume (DCBV) induced by JVO increased with SaO 2 (P < 0.05). In addition, the strength of the correlation of CSvO 2 with SSSO 2 progressively improved with increasing change in total haemoglobin concentration (DHbT) induced by JVO. With Bland-Altman analysis repeated for data with DHbT > 30 lmol cm, the mean difference (CSvO 2 ÀSSSO 2 ) decreased to 2.4% with limits of agreement of 618.8%. We conclude that the accuracy of estimating CSvO 2 varies with the DCBV induced by JVO. Potential differences of optical properties between the head of the lamb and the human infant suggest that caution be exercised in directly applying these data to the human newborn. Nevertheless, this critical aspect of the JVO technique needs to be taken into consideration in developing an accurate measurement for sick preterm human infants.

BACKGROUND: Near Infrared Spectroscopy (NIRS) combined with the method of partial jugular venous occlusion (JVO) has been introduced to measure cerebral venous saturation (CVSO2) at the bedside. As yet, the method has not been validated in the newborn brain. We aimed to validate the JVO procedure in a newborn lamb model using cerebral venous oxygen saturation in withdrawn superior sagittal sinus blood as the 'gold standard'.METHOD: Seven newborn lambs were anaesthetised and ventilated using 10 -40% inspired oxygen to generate a range of oxygen saturations from normoxia (SPO2 Ͼ 95%) and hypoxia (SPO2 Ͻ 95%). Unilateral JVO was performed by compressing the jugular vein for 20s. NIRS (Hamamatsu NIRO-500) measurements of cerebral oxyhaemoglobin (delta HbO) and total haemoglobin (delta HbT) concentrations were used to calculate CVSO2 (CVSO2 ϭ (delta HbO / delta HbT) x100%). Blood samples drawn from the superior sagittal sinus were analysed for oxgyen saturation (SSSO2; Radiometer Hemoximeter) as the 'gold standard' for comparison with CVSO2.RESULTS: Median (range) SSSO2 was 45.5% (4.3-76.6%). Median (range) CVSO2 measured by NIRS was 49.8% (10.6 -88.5%) with significant correlation between the two measurements (rϭ0.7, pϽ0.0001). The mean difference (SD) between SSSO2 and CVSO2 was 5.1% (13.7%). Median percentage change in cerebral blood volume (CBV, calculated using delta HbT) induced by JVO during hypoxia was significantly less than what was induced during normoxia (14.7% and 23.3% respectively, pϽ0.001). When only occlusions inducing change of CBV Ͼ10% were included, mean difference (SD) betweeen SSSO2 and CVSO2 reduced to 2.7% (9.3%) with further improved correlation (rϭ0.9).CONCLUSION: The accuracy of NIRS with JVO in estimating CVSO2 varies according to the changes in cerebral venous blood volume induced by JVO. This critical aspect of the JVO technique needs to be taken into consideration in developing an accurate measurement in human infants. CEREBRAL OXYGEN DELIVERY AND CONSUMPTION INCREASE WITH POSTNATAL AGE IN PRETERM INFANTS ON INOTROPES RITCHIE CENTRE FOR BABY HEALTH RE-SEARCH, MONASH UNIVERSITY , 2 NEWBORN SERVICES, MONASH MEDICAL CENTRE (AUS-TRIA)BACKGROUND: The effect of inotropic medication on cerebral oxygen metabolism of preterm infants remains unknown. We recently validated the method of Near Infrared Spectroscopy (NIRS) combined with partial jugular venous occlusion to measure cerebral venous saturation (CVSO2) in the newborn lamb brain (separate abstract). Using NIRS, we studied normotensive infants (NT) and infants who were on inotropes (INO, dopamine) for hypotension, and compared their cerebral oxygen delivery (CDO2) and consumption (CMRO2) in the first few days of life.METHOD: Nineteen infants in the NT group and ten infants in the INO group, born at median (range) gestational age of 26 (24 -30) weeks, were studied at median (range) postnatal age (PNA) of 17 (2.4 -77) hours. Using NIRS (Hamamatsu NIRO-500), cerebral blood flow (CBF) and CVSO2 were measured to compute CDO2 (CDO2 ϭ CBF x cereb...