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A multicenter randomized controlled trial to assess the feasibility of testing modified ultrafiltration as a blood conservation technology in cardiac surgery
Boodhwani M, Hamilton A, de Varennes B, Mesana T, Williams K, Wells GA, Nathan H, Dupuis JY, Babaev A, Wells P, et al
The Journal of Thoracic and Cardiovascular Surgery. 2010;139((3):):701-6.
Abstract
OBJECTIVES Modified ultrafiltration is a technique after cardiopulmonary bypass whereby blood withdrawn from the aortic cannula is passed across a semipermeable membrane to hemoconcentrate. Unblinded trials have suggested that modified ultrafiltration is efficacious for blood conservation. The objective of this trial was to assess the feasibility of a model testing modified ultrafiltration in which all members of the surgical team were blinded to the intervention. METHODS Patients (<65kg) undergoing procedures involving cardiopulmonary bypass were randomized to undergo either modified ultrafiltration (n=29) or sham (circulation without an interposed filter, n=36) for 15 minutes. The circuit was shielded from all members of the team except the perfusionist. A questionnaire was administered to determine the blinding success. RESULTS Modified ultrafiltration resulted in a removal of 1000+/-251mL of fluid and a reduction in the pump balance (1025+/-807 vs 1804+/-838; P < . 001) with an increase in hemoglobin immediately after intervention (increase of 7. 7+/-8. 8g/L in modified ultrafiltration vs 3. 8+/-5. 1g/L in sham; P=. 04). Introduction or increase in dose of vasopressors was more frequent in the modified ultrafiltration group (52% vs 28%; P=. 048). Differences in red cell transfusion rates between groups did not reach statistical significance (P=. 59). Blinding was successful for the anesthetist (blinding index 0. 13 [95% confidence interval, 0. 11-0. 38] and the intensivist (blinding index, 0. 09 [95% confidence interval, 0. 14-0. 31]) but not for the surgeon (blinding index, 0. 24 [95% confidence interval, 0. 05-0. 42]). The compliance rate for the transfusion protocol was greater than 90%. CONCLUSIONS Modified ultrafiltration was effective for hemoconcentration after cardiopulmonary bypass in patients of low body weight, but it is associated with an increased need for vasopressor support. The anesthetist and intensivist were successfully blinded to the intervention.
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Effects of shed mediastinal blood on cardiovascular and pulmonary function: a randomized, double-blind study
Boodhwani M, Nathan HJ, Mesana TG, Rubens FD, Cardiotomy Investigators
The Annals of Thoracic Surgery. 2008;86((4):):1167-73.
Abstract
BACKGROUND Shed mediastinal blood during cardiopulmonary bypass (cardiotomy blood) contains fat, particulate matter, and vasoactive mediators that can adversely affect the pulmonary and systemic vasculature, as well as impair gas exchange. Our aim was to evaluate the effects of processing cardiotomy blood on cardiovascular and pulmonary function after cardiac surgery. METHODS Patients undergoing coronary artery bypass or aortic valve surgery, or both, using cardiopulmonary bypass were randomly allocated to receiving processed (treated, n = 132) or unprocessed shed blood (control, n = 134) In the treated group, shed blood was processed by centrifugation, washing, and additional filtration. Pulmonary function, arterial and venous blood gases, and hemodynamics were measured before, immediately after, and 2 hours after cardiopulmonary bypass in a consecutive subset of patients (n = 154). Patients and treating physicians were blinded to treatment assignment. RESULTS Preoperative characteristics were similar between groups. There were no significant differences between groups in indexes of pulmonary mechanical function at any of the measured time points. Patients in the treated group demonstrated reduced pulmonary and systemic vascular resistance (both p < 0. 01) as well as increased cardiac index in the perioperative period (2. 6 +/- 0. 07 versus 2. 3 +/- 0. 06 L . min(-1) . m(-2) at 2 hours after CPB, p = 0. 004). Larger volumes of cardiotomy blood were associated with greater changes in systemic and pulmonary vascular resistance. Indicators of pulmonary gas exchange were similar between groups at all measured time points. Treated patients demonstrated a trend toward reduced length of ventilation (11. 0 +/- 1. 9 versus 13. 9 +/- 2. 4 hours, p = 0. 12). CONCLUSIONS Processing of shed mediastinal blood improves cardiopulmonary hemodynamics and may reduce ventilatory requirements after cardiac surgery.
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The cardiotomy trial: a randomized, double-blind study to assess the effect of processing of shed blood during cardiopulmonary bypass on transfusion and neurocognitive function
Rubens FD, Boodhwani M, Mesana T, Wozny D, Wells G, Nathan HJ, Cardiotomy Investigators
Circulation. 2007;116((11 Suppl):):I89-97.
Abstract
BACKGROUND Reinfusion of unprocessed cardiotomy blood during cardiac surgery can introduce particulate material into the cardiopulmonary bypass circuit, which may contribute to postoperative cognitive dysfunction. On the other hand, processing of this blood by centrifugation and filtration removes coagulation factors and may potentially contribute to coagulopathy. We sought to evaluate the effects of cardiotomy blood processing on blood product use and neurocognitive functioning after cardiac surgery. METHODS AND RESULTS Patients undergoing coronary and/or aortic valve surgery using cardiopulmonary bypass were randomized to receive unprocessed blood (control, n=134) or cardiotomy blood that had been processed by centrifugal washing and lipid filtration (treatment, n=132). Patients and treating physicians were blinded to treatment assignment. A strict transfusion protocol was followed. Blood transfusion data were analyzed using Poisson regression models. The treatment group received more intraoperative red blood cell transfusions (0. 23+/-0. 69 U versus 0. 08+/-0. 34 U, P=0. 004). Both red blood cell and nonred blood cell blood product use was greater in the treatment group and postoperative bleeding was greater in the treatment group. Patients were monitored intraoperatively by transcranial Doppler and they underwent neuropsychometric testing before surgery and at 5 days and 3 months after surgery. There was no difference in the incidence of postoperative cognitive dysfunction in the 2 groups (relative risk: 1. 16, 95% CI: 0. 86 to 1. 57 at 5 days postoperatively; relative risk: 1. 05, 95% CI: 0. 58 to 1. 90 at 3 months). There was no difference in the quality of life nor was there a difference in the number of emboli detected in the 2 groups. CONCLUSIONS Contrary to expectations, processing of cardiotomy blood before reinfusion results in greater blood product use with greater postoperative bleeding in patients undergoing cardiac surgery. There is no clinical evidence of any neurologic benefit with this approach in terms of postoperative cognitive function.
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A decision aid for autologous pre-donation in cardiac surgery--a randomized trial
Laupacis A, O'Connor AM, Drake ER, Rubens FD, Robblee JA, Grant FC, Wells PS
Patient Education and Counseling. 2006;61((3):):458-66.
Abstract
OBJECTIVES The objective of this randomized, controlled study was to determine the usefulness of a decision aid on pre-donation of autologous blood before elective open heart surgery. METHODS The decision aid (DA) group received a tape and booklet which described the options for peri-operative transfusion in detail. The no decision aid (NDA) group received information usually given to patients about autologous donation. RESULTS A total of 120 patients were randomized. The DA group rated themselves better prepared for decision making and showed significant improvements in knowledge (p = 0. 001) and realistic risk perceptions (p = 0. 001). In both groups there was an increase in the proportion of patients choosing allogeneic blood between baseline and follow-up (p = 0. 001). Patients in the DA group were significantly more satisfied with the amount of information they received, how they were treated and with the decision they made, than patients in the NDA group. CONCLUSION The decision aid is useful in preparing patients for decision making. PRACTICE IMPLICATIONS The next stage is to explore strategies to make it available to all appropriate patients.
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Ultrafiltration reduces blood transfusions following cardiac surgery: A meta-analysis
Boodhwani M, Williams K, Babaev A, Gill G, Saleem N, Rubens FD
European Journal of Cardio-Thoracic Surgery. 2006;30((6):):892-7.
Abstract
BACKGROUND Although used routinely in pediatric patients, ultrafiltration techniques that reverse hemodilution are infrequently used in adults. Data from small, unblinded clinical trials suggest that the use of ultrafiltration can reduce inflammatory mediators, improve cardiac function, and reduce hemodilution. We conducted a meta-analysis of randomized trials to evaluate the effects of ultrafiltration on blood transfusions and blood loss following adult cardiac surgery. METHODS Medline, EMBASE, and Cochrane databases were searched and randomized controlled trials evaluating modified and/or conventional ultrafiltration, meeting pre-determined selection criteria, were obtained. Quality evaluation and data extraction were performed by two independent observers blinded to study source. Random effects models were used to determine pooled effect estimates and sources of heterogeneity were explored using meta-regression. RESULTS One hundred and thirty two studies were screened and 10 randomized trials evaluating 1004 patients (control, n = 495; ultrafiltration, n = 509) were identified of which only two were double-blinded. The use of ultrafiltration was associated with a reduction in postoperative blood transfusions (weighted mean difference (95% CI) of -0.73 units (-1.16, -0.31); p = 0.001). This reduction was greater in studies evaluating modified ultrafiltration. Use of ultrafiltration was also associated with reduced postoperative bleeding (-70 ml, (-118, -21); p = 0.005), which was driven primarily by trials evaluating modified rather than conventional ultrafiltration. CONCLUSIONS Use of ultrafiltration is associated with a significant reduction in postoperative blood transfusions as well as reduced bleeding in adults undergoing cardiac surgery. The efficacy and cost-effectiveness of ultrafiltration as a blood conservations strategy should be evaluated in a large, randomized, double-blinded study.
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Feasibility of blinding in a randomized controlled trial comparing preoperative autologous blood donation and acute normovolemic hemodilution in adult cardiac surgery
Rubens FD, Dupuis JY, Robblee J, Rock G, Bryson GL, Wells PS
Transfusion. 2000;40((9):):1058-62.
Abstract
BACKGROUND Acute normovolemic hemodilution and preoperative autologous donation have been shown to be effective techniques for decreasing the exposure of patients to allogeneic blood during cardiac surgery. They have not, however, been compared to each other, because of perceived difficulties in blinding in such a clinical study. The feasibility of blinding was tested in a pilot trial. STUDY DESIGN AND METHODS Ten patients were randomly assigned to undergo preoperative autologous blood donation or acute normovolemic hemodilution during cardiac surgery. Patients were blinded during this process by shielding of the arm and by insertion of an intravenous line in each patient. Every attempt was made to blind the clinical staff during and after surgery. The effectiveness of this blinding was determined by using a questionnaire. RESULTS In the 10 cases, six patients, four surgeons, and one anesthetist answered, "I do not know," with respect to whether preoperative autologous blood donation had occurred. The remaining people interviewed believed the blinding was unsuccessful. However, correct answers were given by 75 percent of the patients (95% CI, 19-99%), 83 percent of the surgeons (95% CI, 36-99.6%), and 66 percent of the anesthetists (95% CI, 29.9-92.5%). The frequency of correct answers did not differ significantly from the 50 percent expected by chance, but the CIs are wide. CONCLUSIONS Blinding of patients and all members of the surgical team during both the preoperative donation process and acute normovolemic hemodilution in the operating theater was successful most of the time, as the frequency of correct answers did not differ significantly from the 50 percent expected by chance. However, more accurate estimates of the success of blinding require a study with a larger sample. It is possible that, with a larger series, the physician's ability to determine patient assignment would be significantly better than that by chance alone.