[The effect of acid-base management on the oxygen uptake of the human body during hypothermic extracorporeal circulation].
The effects of two different systems of acid-base management on whole-body oxygen consumption during and following hypothermic cardiopulmonary bypass were investigated in 42 patients undergoing coronary artery bypass grafting or valve replacement surgery. In group I (22 patients) pH-stat management and in group II (20 patients) alpha-stat management was used. METHODS. Anesthesia was performed with fentanyl, midazolam, and pancuronium bromide. Halothane was added whenever MAP exceeded 100 mmHg. Cardiopulmonary bypass was conducted with a membrane oxygenator and a roller pump. Pump flow varied between 2 and 2.5 l/min per m2 body surface area. Once patients had been initially cooled down to a venous blood temperature of 27 degrees C they were kept stable between 28 degrees C and 30 degrees C during the ischemic phase. Measurements were performed after sternotomy during normothermia (control values) and every 15 min from the start until termination of bypass. RESULTS AND DISCUSSION. Neither hemodynamic parameters (MAP, CI, SVR) nor rectal or skin temperatures differed significantly between the two groups during the entire study period. Although at 27 degrees C oxygen availability fell by 43% and 35% in groups I and II, respectively, mixed venous oxygen saturation was significantly elevated compared with the control value, because of a decrease of 60% and 51%, respectively, in the arterio-venous oxygen content difference and of 62% and 55%, respectively, in oxygen consumption. Rewarming led to normalization of the metabolic parameters except for oxygen availability, which was still decreased as a result of low hemoglobin content. After termination of the bypass oxygen consumption increased steadily, which may have been due either to the beginning of shivering or to repayment of an oxygen debt caused by hypothermic bypass. As statistically significant differences were detected between the two groups in metabolic parameters during the course of the investigation, the hypothesis of Rahn and Reeves [2, 3], according to which oxygen consumption must be expected to be higher with alpha-stat than with pH-stat management, could not be verified by this study.
Mündemann
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A
Zentrum Anaesthesiologie, Rettungs- und Intensivmedizin, Universität Göttingen.
Stephan
H
H
Weyland
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A
Wellhausen
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A
Sonntag
H
H
D000137:Acid-Base Imbalance / Q000628:therapy*; D000368:Aged; D002315:Cardiopulmonary Bypass; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*
Einfluss des Säure-Basenmanagements auf die Sauerstoffaufnahme des menschlichen Körpers während hypothermer extrakorporaler Zirkulation.