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.


OBJECTIVE
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 (DeltacO2Hb), deoxyhemoglobin (DeltacHHb), and cerebral arterial oxygenation (DeltacHbD; the difference between DeltacO2Hb and DeltacHHb), and cerebral blood volume (DeltaCBV) 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 DeltacO2Hb and DeltacHbD, and negatively with DeltacHHb 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) micromol/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 DeltacO2Hb, DeltacHHb, DeltacHbD and DeltaCBV can be used to assess the decline in brain cell function during hypoxemia in lambs born near term.
Van Os
Sandra
S
Division of Neonatology, Department of Pediatrics, University Medical Center Nijmegen, Nijmegen, The Netherlands.
Klaessens
John
J
Hopman
Jeroen
J
Liem
Djien
D
Van de Bor
Margot
M
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002536:Cerebral Arteries; D005311:Fetal Hypoxia / Q000378:metabolism*; D006454:Hemoglobins / Q000032:analysis; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000032:analysis; D012756:Sheep; D019265:Spectroscopy, Near-Infrared
D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen