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Cerebral protection during moderate hypothermic circulatory arrest: Histopathology and magnetic resonance spectroscopy of brain energetics and intracellular pH in pigs
LITERATURE REVIEW Frederick W. Campbell, MD Section Editor
SCIENTIFIC ARTICLES
Stecker MM, Cheung AP, Patterson T, et al: Detection of stroke during cardiac operations with somatosensory-evoked responses. J Thorac Cardiovasc Surg 112:962-972, 1996 Preoperative and postoperative neurological examinations and intraoperative somatosensory-evoked potential recording were performed in 25 patients undergoing cardiac operations. Two of 25 patients had intraoperative strokes. Only these two patients had somatosensoryevoked potential changes suggesting cerebral ischemia during operations; unilateral disappearance of cortical somatosensory potential waves correlated significantly with stroke outcome (p < 0.004). Acute unilateral decreases in cortical potential amplitude were more useful than changes in latency for detection of stroke. Ischemic changes were related to removal of aorta cross-clamp in one patient and initiation of bypass in the other.
Regragui I, Birdi I, Izzat MB, et ah The effects of cardiopulmonary bypass temperature and neuropsychologic outcome after coronary artery operations: A prospective randomized trial. J Thorac Cardiovasc Surg 112:1036-1045, 1996 Five neuropsychological tests adapted from the Wechsler adult intelligence scale and two from the Wechsler memory scale were administered to 96 adult patients undergoing elective coronary revascularization with cardiopulmonary bypass at 28°C, 32°C, or 37°C systemic perfusion temperature. No major neurological complications occurred. The number of neuropsychological tests in which there was preoperative to postoperative (6 weeks) deterioration was related to cardiopulmonary bypass temperature (p = 0.021); the number with bypass at 37°C is significantly greater than the number with bypass at 32°C (p = 0.015). Further cooling to 28°C provided no additional benefit in cognitive function. The small number of patients studied, choice of neuropsychological tests, and analysis of results may be questioned. Furthermore, strategies that minimize neuropsychological deterioration resulting from global cerebral injury or other factors may not effectively prevent focal cerebral injury and stroke.
Filgueiras CL, Ryner L, Ye J, et ah Cerebral protection during moderate hypothermic circulatory arrest: Histopathology and magnetic resonance spectroscopy of brain energetics and intracellular pH in pigs. J Thorac Cardiovasc Surg 112:1073-1080, 1996 Pigs were subjected to antegrade (perfusion through carotid arteries at 180 to 210 mL/min flow rate; n = 6) or retrograde (perfusion through superior vena cava at 300 to 500 mL/min flow rate; n = 8) brain perfusion during moderate hypothermic (28°C) circulatory arrest. Anesthetized and hypothermic cardiopulmonary bypass animals served as controls. Brain intracellular pH and high-energy metabolites did not change during the study course in anesthetized and hypothermic 530
cardiopulmonary bypass control animals. In antegrade perfusion animals, adenosine triphosphate and intracellular pH were unchanged during 2 hours of ischemia and i hour of reperfusion. In the retrograde perfusion group, intracellular pH, adenosine triphosphate, and phosphocreatine levels decreased within 30 minutes of circulatory arrest and remained low; high-energy phosphates did not return to initial levels during reperfusion. Histopathological injury was observed in all brain regions examined in retrograde perfusion animals; cell structure was preserved in the antegrade perfusion and control groups.
Helm RE, Klemperer JD, Rosengart TK, et ah Intraoperative autologous blood donation preserves red cell mass but does not decrease postoperative bleeding. Ann Thorac Surg 62:1431-1441, 1996 Ninety patients undergoing cardiac surgery with cardiopulmonary bypass were studied in a prospective, randomized, controlled trial with standardized transfusion guidelines. Maximum volume intraoperative autologous donation (IAD) (to target bypass hematocrit 18%) in the experimental group yielded an average volume of 1,540 mL harvested before skin incision in citrated bags and reinfused after bypass. Postoperative hematocrit was significantly greater in the IAD group despite a significant decrease in allogeneic red blood cell transfusion (17% IAD patients v 52% control patients; p < 0.01) and the number of red blood cell units transfused per patient (0.28 and 1.14 units; p < 0.01). Conversely, chest tube output, postoperative prothrombin time, and platelet and coagulation factor transfusion requirements did not differ between groups. Blood conservation resulted from decreased intraoperative red blood cell loss related to the normovolemic hemodilution in the IAD group and was not related to hemostatic function and postoperative blood loss.
Christenson JT, Reuse J, Badel P, et ah Plateletpheresis before redo CABG diminishes excessive blood transfusion. Ann Thorac Surg 62:1373-1379, 1996 Immediate preoperative plateletpheresis produced a mean platelet yield 27% (range, 20% to 37%) in patients (n = 20) randomized to the treatment group. Average total chest tube blood loss was 423 mL in the platelet-rich plasma (PRP) group compared with 1,462 mL in controls (n = 20; p < 0.001). Fourteen patients in the control group required blood transfusions postoperatively compared with one patient in the PRP group (p < 0.001). A cost-benefit analysis showed a $3,100 reduction in the total cost for redo coronary artery bypass graft using PRP harvest. Platelet yield during PRP is directly related to the efficacy of this blood conservation strategy.
D'Ambra MN, Akins CW, Blackstone EH, et ah Aprotinin in primary valve replacement and reconstruction: A multicenter, double-blind, placebocontrolled trial. J Thorac Cardiovasc Surg 112:10811089, 1996 In a standardized protocol, 212 patients undergoing primary sternotomy for valve replacement or repair randomly received high-dose
Journal o f Cardiothoracic and Vascular Anesthesia, Vol 11, No 4 (June), 1997: pp 530-532
SCIENTIFIC ARTICLES
Stecker MM, Cheung AP, Patterson T, et al: Detection of stroke during cardiac operations with somatosensory-evoked responses. J Thorac Cardiovasc Surg 112:962-972, 1996 Preoperative and postoperative neurological examinations and intraoperative somatosensory-evoked potential recording were performed in 25 patients undergoing cardiac operations. Two of 25 patients had intraoperative strokes. Only these two patients had somatosensoryevoked potential changes suggesting cerebral ischemia during operations; unilateral disappearance of cortical somatosensory potential waves correlated significantly with stroke outcome (p < 0.004). Acute unilateral decreases in cortical potential amplitude were more useful than changes in latency for detection of stroke. Ischemic changes were related to removal of aorta cross-clamp in one patient and initiation of bypass in the other.
Regragui I, Birdi I, Izzat MB, et ah The effects of cardiopulmonary bypass temperature and neuropsychologic outcome after coronary artery operations: A prospective randomized trial. J Thorac Cardiovasc Surg 112:1036-1045, 1996 Five neuropsychological tests adapted from the Wechsler adult intelligence scale and two from the Wechsler memory scale were administered to 96 adult patients undergoing elective coronary revascularization with cardiopulmonary bypass at 28°C, 32°C, or 37°C systemic perfusion temperature. No major neurological complications occurred. The number of neuropsychological tests in which there was preoperative to postoperative (6 weeks) deterioration was related to cardiopulmonary bypass temperature (p = 0.021); the number with bypass at 37°C is significantly greater than the number with bypass at 32°C (p = 0.015). Further cooling to 28°C provided no additional benefit in cognitive function. The small number of patients studied, choice of neuropsychological tests, and analysis of results may be questioned. Furthermore, strategies that minimize neuropsychological deterioration resulting from global cerebral injury or other factors may not effectively prevent focal cerebral injury and stroke.
Filgueiras CL, Ryner L, Ye J, et ah Cerebral protection during moderate hypothermic circulatory arrest: Histopathology and magnetic resonance spectroscopy of brain energetics and intracellular pH in pigs. J Thorac Cardiovasc Surg 112:1073-1080, 1996 Pigs were subjected to antegrade (perfusion through carotid arteries at 180 to 210 mL/min flow rate; n = 6) or retrograde (perfusion through superior vena cava at 300 to 500 mL/min flow rate; n = 8) brain perfusion during moderate hypothermic (28°C) circulatory arrest. Anesthetized and hypothermic cardiopulmonary bypass animals served as controls. Brain intracellular pH and high-energy metabolites did not change during the study course in anesthetized and hypothermic 530
cardiopulmonary bypass control animals. In antegrade perfusion animals, adenosine triphosphate and intracellular pH were unchanged during 2 hours of ischemia and i hour of reperfusion. In the retrograde perfusion group, intracellular pH, adenosine triphosphate, and phosphocreatine levels decreased within 30 minutes of circulatory arrest and remained low; high-energy phosphates did not return to initial levels during reperfusion. Histopathological injury was observed in all brain regions examined in retrograde perfusion animals; cell structure was preserved in the antegrade perfusion and control groups.
Helm RE, Klemperer JD, Rosengart TK, et ah Intraoperative autologous blood donation preserves red cell mass but does not decrease postoperative bleeding. Ann Thorac Surg 62:1431-1441, 1996 Ninety patients undergoing cardiac surgery with cardiopulmonary bypass were studied in a prospective, randomized, controlled trial with standardized transfusion guidelines. Maximum volume intraoperative autologous donation (IAD) (to target bypass hematocrit 18%) in the experimental group yielded an average volume of 1,540 mL harvested before skin incision in citrated bags and reinfused after bypass. Postoperative hematocrit was significantly greater in the IAD group despite a significant decrease in allogeneic red blood cell transfusion (17% IAD patients v 52% control patients; p < 0.01) and the number of red blood cell units transfused per patient (0.28 and 1.14 units; p < 0.01). Conversely, chest tube output, postoperative prothrombin time, and platelet and coagulation factor transfusion requirements did not differ between groups. Blood conservation resulted from decreased intraoperative red blood cell loss related to the normovolemic hemodilution in the IAD group and was not related to hemostatic function and postoperative blood loss.
Christenson JT, Reuse J, Badel P, et ah Plateletpheresis before redo CABG diminishes excessive blood transfusion. Ann Thorac Surg 62:1373-1379, 1996 Immediate preoperative plateletpheresis produced a mean platelet yield 27% (range, 20% to 37%) in patients (n = 20) randomized to the treatment group. Average total chest tube blood loss was 423 mL in the platelet-rich plasma (PRP) group compared with 1,462 mL in controls (n = 20; p < 0.001). Fourteen patients in the control group required blood transfusions postoperatively compared with one patient in the PRP group (p < 0.001). A cost-benefit analysis showed a $3,100 reduction in the total cost for redo coronary artery bypass graft using PRP harvest. Platelet yield during PRP is directly related to the efficacy of this blood conservation strategy.
D'Ambra MN, Akins CW, Blackstone EH, et ah Aprotinin in primary valve replacement and reconstruction: A multicenter, double-blind, placebocontrolled trial. J Thorac Cardiovasc Surg 112:10811089, 1996 In a standardized protocol, 212 patients undergoing primary sternotomy for valve replacement or repair randomly received high-dose
Journal o f Cardiothoracic and Vascular Anesthesia, Vol 11, No 4 (June), 1997: pp 530-532