The Annals of thoracic surgery
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The primary goal of monitoring cerebral blood flow and metabolism is to improve our understanding of the association with cardiopulmonary bypass and deep hypothermic circulatory arrest so that effective brain protection strategies can be developed and employed. A review of our cerebral blood flow/cardiopulmonary bypass database, presently totaling 275 neonates and infants, for the purposes of this publication, reveals certain trends and some conclusions that can be drawn. Deep hypothermic circulatory arrest continues to be a factor in the delayed recovery of cerebral blood flow and metabolism in these patients. ⋯ We have also examined in our series of 275 patients selective neuroprotection strategies for their potential for improving recovery of cerebral blood flow and cerebral metabolism. Duration of cooling on cardiopulmonary bypass correlates directly with suppression of metabolism due to hypothermia. Low-flow cardiopulmonary bypass instead of deep hypothermic circulatory arrest, and topical brain cooling with ice during deep hypothermic circulatory arrest, improve cerebral blood flow and cerebral metabolic recovery.
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Comparative Study
Revascularization for acute regional infarct: superior protection with warm blood cardioplegia.
Continuous retrograde warm blood cardioplegia was compared with two widely used hypothermic myocardial protection techniques in a canine model of acute regional myocardial ischemia with subsequent revascularization. Animals (n = 30) underwent 45 minutes of left anterior descending coronary artery occlusion then cardioplegic arrest (60 minutes), followed by separation from cardiopulmonary bypass and data collection. The cold oxygenated crystalloid cardioplegia group (CC; n = 8) and the cold blood cardioplegia group (CC; n = 10) had cardiopulmonary bypass at 28 degrees C, antegrade arrest, and intermittent retrograde delivery. ⋯ Left anterior descending coronary artery regional adenosine triphosphate/adenosine diphosphate ratios were significantly (p = 0.02) worse for CC (WB, 10.2 +/- 2.3; CB, 9.4 +/- 2.6; CC, 5.6 +/- 1.5). Myocardial edema significantly (p = 0.03) increased over time only in the CC animals (WB, 0.4% +/- 2.3%; CB, -0.3% +/- 3.6%; CC, 5.5% +/- 2.3%). In this model of acute regional myocardial ischemia and revascularization, continuous retrograde warm aerobic blood cardioplegia provided superior myocardial protection compared with cold oxygenated crystalloid cardioplegia with intermediate results for cold blood cardioplegia.
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Practice Guideline Guideline
Practice guidelines in cardiothoracic surgery. Council of the Society of Thoracic Surgeons.
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We examined the oxygen tension, carbon dioxide tension, and pH in canine brains under profound hypothermia to evaluate the effects of perfusion (circulatory arrest for 1 hour; 25 and 50 mL.kg-1 x min-1 for 2 hours) with and without pulsatile assistance. The effects of pulsatile flow on cerebral blood flow and metabolism were also evaluated in dogs supported by low-flow perfusion (25 mL.kg-1 x min-1) for 2 hours. ⋯ Brain tissue acidosis with hypercapnia was moderated by perfusion at a rate of flow of 50 mL.kg-1 x min-1. Pulsatile low-flow perfusion (25 mL.kg-1 x min-1) moderated cerebral hypercapnia and made the cerebral metabolism aerobic without affecting the total cerebral blood flow and consumption of oxygen.
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The etiology and incidence of neurologic injury occurring after cardiac operations employing cardiopulmonary bypass is reviewed. Results of studies demonstrating the role of microemboli generated by pump oxygenators, and evidence for the efficacy of arterial line filtration to decrease delivery of emboli into the cerebral circulation and to decrease postoperative neuropsychological dysfunction, are similarly reviewed. The impact of different strategies for management of pH during moderate hypothermic cardiopulmonary bypass on cerebral blood flow and coupling of cerebral flow and metabolism, as well as their impact on the incidence of postoperative cognitive dysfunction, are also discussed, along with the results of studies examining the efficacy of various agents including thiopental, nimodipine, and nafamostat to decrease cognitive dysfunction subsequent to bypass.