Supplementary Material for: Association between Brain and Kidney Near-Infrared Spectroscopy and Early Postresuscitation Mortality in Asphyxiated Newborn Piglets

Background: Early outcome predictors after delivery room cardiopulmonary resuscitation (CPR) of asphyxiated newborns are needed. Objectives: To investigate if cerebral (rScO₂) and renal (rSrO₂) tissue oxygen saturation 30 min after return of spontaneous circulation (ROSC) are different between surviving versus nonsurviving piglets with asphyxia-induced cardiac arrest and CPR. Further, to investigate the relationship of rScO₂ and rSrO₂ to cardiac output (CO), blood pressure (BP), and biochemical variables 30 min and 4 h after ROSC. Methods: Anesthetized, mechanically ventilated piglets (1-3 days, 1.7-2.4 kg) were used. rScO₂, rSrO₂, SpO₂, right common carotid artery flow, and arterial BP were measured continuously. CO was measured with echocardiography. The piglets were asphyxiated until cardiac arrest and resuscitated. Piglets that survived 4 h after ROSC (n = 12) were compared with piglets that died before planned euthanasia at 4 h (n = 13). Left ventricular, and kidney and brain tissue lactate were analyzed. Correlations between variables were assessed. Results: Thirty minutes after ROSC, median rSrO₂ (43% [n = 10] vs. 25% [n = 2], p = 0.003) but not rScO₂ (46% [41-55] [n = 10] vs. 40% [22-45] [n = 5], p = 0.08) was higher in survivors than in nonsurvivors. Arterial lactate was negatively correlated and pH positively correlated with rScO₂ and rSrO₂. Left ventricular, but not kidney or brain lactate was negatively correlated with rScO₂ and rSrO₂. There was no correlation between CO or BP and rScO₂ or rSrO₂. Conclusions: Despite satisfactory CO and BP vital organ oxygenation can be poor. Tissue oxygen saturation, pH, and lactate, as measures of anaerobic metabolism, may reflect vital organ oxygenation and outcome.