Cerebral Arterial Oxygen Content Research Articles

Peri-operative characteristics of cerebral oxygen metabolism in patients with encephalopathy after orthotopic liver transplantation

To investigate the feature of cerebral oxygen metabolism during peri-operative stage of orthotopic liver transplantation (OLT), in order to identify the difference between the patients with or without complicating encephalopathy after OLT, and the relationship between the cerebral oxygen metabolism and encephalopathy after OLT. Thirty patients undergoing OLT were studied. The patients were divided into two groups according to occurrence or not of encephalopathy after OLT: encephalopathy group and non-encephalopathy group. Blood samples were taken from radial artery and jugular vein simultaneously for blood gas analysis before operation, 25 minutes after onset of anhepatic phase, 30 minutes after graft reperfusion , 3 hours after graft reperfusion , and 24 hours after graft reperfusion. Cerebral arterial oxygen content (CaO(2)), oxygen content of jugular vein blood (CjvO(2)), cerebral arterial-venous oxygen content difference (Ca-jvO(2)), cerebral oxygen extraction ratio (CERO(2)) and cerebral blood flow/cerebral metabolic rate of oxygen ratio (CBF/CMRO(2)) were calculated, and the levels of blood glucose and lactic acid were recorded. There were 11 patients (36.7%) complicated by encephalopathy after OLT. The quantity of red blood cell infusion, blood loss and the dosage of noradrenalin in encephalopathy group were significantly larger compared with non-encephalopathy group. The overall tendency of change in cerebral oxygen metabolism index was about the same for both groups, while CaO(2) and Ca-jvO(2) at 25 minutes after onset of anhepatic phase, 30 minutes after graft reperfusion and 3 hours after graft reperfusion , and CERO(2) at 30 minutes after graft reperfusion and 3 hours after graft reperfusion were significantly decreased compared with those before operation [CaO(2) (ml/L) in encephalopathy group: 132.4 ± 23.5 , 125.9 ± 17.6, 133.4 ± 11.1 vs. 148.5 ± 28.8, in non-encephalopathy group: 135.7 ± 22.4, 130.5 ± 20.0, 139.9 ± 21.2 vs. 148.9 ± 28.2; Ca-jvO(2) (ml/L) in encephalopathy group: 42.9 ± 13.2, 31.4 ± 12.3 , 32.3 ± 6.5 vs. 52.9 ± 23.5, in non-encephalopathy group: 33.0 ± 14.1, 26.6 ± 9.1, 30.6 ± 10.3 vs. 50.2 ± 23.2; CERO(2) in encephalopathy group: (24.9 ± 9.7)%, (24.4 ± 5.5)% vs. (35.4 ± 11.5)%, in non-encephalopathy group: (20.6 ± 7.3)%, (21.9 ± 7.0)% vs. (33.4 ± 13.1)%, all P < 0.05], and they returned to the levels before operation at 24 hours after graft reperfusion. Jugular venous oxygen saturation (SjvO(2)) and CBF/CMRO(2) ratio were significantly increased at 30 minutes after graft reperfusion and 3 hours after graft reperfusion compared with the levels before operation [SjvO(2) in encephalopathy group: 0.838 ± 0.105, 0.835 ± 0.065 vs. 0.709 ± 0.125, in non-encephalopathy group: 0.854 ± 0.074, 0.824 ± 0.074 vs. 0.713 ± 0.138; CBF/CMRO(2) ratio in encephalopathy group: 37.8 ± 16.6, 31.9 ± 6.8 vs. 20.9 ± 6.7 , in non-encephalopathy group: 37.8 ± 14.1, 35.7 ± 13.7 vs. 24.3 ± 14.0, all P <0.05], and they returned to the levels before operation at 24 hours after graft reperfusion. The overall tendency of change in blood glucose and lactic acid was about the same in both groups, while the levels of blood glucose increased significantly from anhepatic phase to 24 hours after graft reperfusion compared with the levels before operation , and the levels of lactic acid increased significantly from anhepatic phase to 3 hours after graft reperfusion compared with the levels before operation and returned to the levels before operation at 24 hours after graft reperfusion. There are significant changes in the features of cerebral oxygen metabolism during OLT, but there is no difference between encephalopathy group and non-encephalopathy group. The occurrence of encephalopathy can be attributed to many factors, so the prevention and treatment should be comprehensive considered.

423 Cerebral Oxygen Delivery and Consumption Increase with Postnatal Age in Preterm Infants on Inotropes

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 = CBF x cerebral arterial oxygen content), and CMRO2 (CMRO2 = CBF x cerebral arterial minus venous oxygen content). RESULTS: In INO infants, CDO2 increased with PNA (r=0.7, p<0.001), but not so in NT infants. Similarly, CMRO2 in INO infants increased with PNA (r=0.6, p<0.01), but not so in NT infants. Before PNA of 24 hours, median (IQR) CDO2 and CMRO2 in INO infants were 2.0 (1.6–2.4)ml/100g/min and 0.5 (0.4–0.9)ml/100g/min respectively, both lower (p<0.05) than the CDO2 and CMRO2 in NT infants (2.7 (2.3–3.1)ml/100g/min and 0.8 (0.7–1.0)ml/100g/min respectively). However, after PNA of 24 hours, no significant difference in CDO2 and CMRO2 was found between the two groups. There was no difference in cerebral oxygen extraction ((arterial saturation-CVSO2)/arterial saturation) between the two groups at any PNA, implying the increase in CMRO2 in INO infants was not delivery-dependent. CONCLUSION: Infants on inotrope had lower cerbral oxygen delivery and consumption in the first day of life, which increased with postnatal age to equate values in normotensive infants.

Brain Cell Function during Hypoxemia in Near-Term Lambs: A Near-Infrared Spectroscopy Study

Background: Sufficient O₂ supply to the brain is necessary for adequate cerebral energy metabolism, function and growth. Objectives: To elucidate the relation between changes in cerebral arterial O₂ content and cerebral O₂ supply and changes in the oxygenation state of cerebral hemoglobin, and to determine whether concentration changes in oxyhemoglobin (ΔcO₂Hb), deoxyhemoglobin (ΔcHHb), and cerebral arterial oxygenation (ΔcHbD; the difference between ΔcO₂Hb and ΔcHHb), and cerebral blood volume (ΔCBV) can be used to assess the decline in brain cell function during hypoxemia in lambs born near term. Methods: 17 preterm lambs were delivered at a mean gestational age of 133 days. Decreases in cerebral arterial oxygen content were induced by a stepwise reduction in inspired oxygen concentration. Mean values of all continuous variables were calculated over the last 180 s of each hypoxemic level. Cerebral arterial blood gases were analyzed at the end of each level to calculate cerebral arterial O₂ content and cerebral O₂ supply. Results: Changes in cerebral arterial O₂ content and cerebral O₂ supply were positively linearly related with ΔcO₂Hb and ΔcHbD, and negatively with ΔcHHb and the concentration changes in total hemoglobin. Electrocortical brain activity remained stable until the cO₂Hb and cHbD decreased to >3.0 ± 0.9 and >8.1 ± 1.9 (mean ± SD) µmol/100 g, respectively, and cHHb and CBV increased to >4.3 ± 1.7 and 1.37 ± 0.48 ml/100 g, respectively, as compared to baseline. Conclusions: Changes in cerebral arterial O₂ content and cerebral O₂ supply are adequately reflected by changes in the oxygenation state of cerebral hemoglobin. Concentration changes in ΔcO₂Hb, ΔcHHb, ΔcHbD and ΔCBV can be used to assess the decline in brain cell function during hypoxemia in lambs born near term.