Perfusion
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Randomized Controlled Trial Clinical Trial
The combination of mannitol and albumin in the priming solution reduces positive intraoperative fluid balance during cardiopulmonary bypass.
During cardiopulmonary bypass (CPB) an adequate reservoir volume is maintained by the addition of crystalloid, colloid or packed cells to the reservoir. This volume contributes to the overall perioperative positive fluid balance. ⋯ There was a large and highly significant reduction in volume of fluid added to the reservoir during CPB (2137 +/- 1499 ml versus 144 +/- 230 ml), the fluid balance during bypass, including prime volume (3236 +/- 650 ml versus 5876 +/- 1465 ml), and perioperative fluid balance (4470 +/- 936 ml versus 7023 +/- 1760 ml) in the group receiving both mannitol and albumin in the pump prime compared with the group receiving only lactated Ringer's solution. There were no differences between the groups with respect to both measured indices of oxygenation measured on return to ICU (alveolar-arterial oxygen tension difference (DA-aO2) or arterial oxygen tension to inspired oxygen fraction ratio (PaO2/FiO2), or time from ICU admission to extubation.
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The relationship between oxygen delivery (DO2) and uptake (VO2) has been studied during moderately hypothermic cardiopulmonary bypass (CPB) in 15 patients undergoing myocardial revascularization. As soon as nasopharyngeal temperature was lowered to 32 degrees C, blood flow was decreased from 2.4 to 2.0 l/min/m2. Arterial and mixed venous blood gas analyses were performed five and eight minutes later and DO2 and VO2 were calculated; VO2 stabilized in five minutes after changing blood flow and neither DO2 nor VO2 values changed three minutes later (DO2: 217 +/- 19 versus 215 +/- 17 ml/min/m2; VO2: 63 +/- 12 versus 66 +/- 14 ml/min/m2). ⋯ Consequently, lower VO2 values suggest inadequate oxygen supply to tissues. Critical DO2 at 32 degrees C is lower than 283 ml/min/m2 in 97.5% of patients. Finally, arterial vasoconstriction does not seem to play a significant role in tissue hypoperfusion.