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J Thorac Cardiovasc Surg 2007;134:1421-1428
© 2007 The American Association for Thoracic Surgery
Surgery for Congenital Heart Disease |
a Division of Cardiovascular–Thoracic Surgery, Department of Surgery, Northwestern University Feinberg School of Medicine, Chicago, Ill
b Division of Kidney Diseases, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Ill
c Childrens Memorial Hospital, and the Department of Pediatrics and Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, Ill. and Mary Ann and J. Milburn Smith Child Health Research Program, Childrens Memorial Research Center, Chicago, Ill.
Read at the Eighty-seventh Annual Meeting of The American Association for Thoracic Surgery, Washington, DC, May 5-9, 2007.
Received for publication May 16, 2007; revisions received July 19, 2007; accepted for publication August 7, 2007. * Address for reprints: Carl L. Backer, MD, Division of Cardiovascular-Thoracic Surgery, Childrens Memorial Hospital, 2300 Childrens Plaza, mc 22, Chicago, IL 60614. (Email: cbacker{at}childrensmemorial.org).
| Abstract |
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Methods: We compared a cohort of all pediatric cardiopulmonary bypass operations from 1994–1999, when aprotinin was not used (n = 1230), with a cohort from 2000–2006, when all patients received high-dose aprotinin (n = 1251). Primary end points were operative and late mortality, acute kidney failure, need for dialysis, and neurologic complications. Association of aprotinin with primary end points was assessed by means of univariate analysis, multivariate logistic regression, and Cox regression analysis, where appropriate.
Results: The aprotinin group was younger (mean age, 3.49 ± 1.84 vs 3.64 ± 4.75 years; P = .019) and had a higher Aristotle score (7.8 ± 2.3 vs 7.2 ± 2.6, P < .001). Univariate and multivariate analysis showed no significant difference between the no-aprotinin and aprotinin groups for operative mortality (55 [4.5%] vs 47 [3.8%], P = .508), acute kidney failure (68 [6.0%] vs 69 [5.7%], P = .77), need for temporary dialysis (6 [0.49%] vs 12 [0.96%], P = .17), or neurologic complications (14 [1.1%] vs 17 [1.4%], P = .62). By means of Cox regression analysis, aprotinin had no influence on late mortality (24 vs 10 deaths, P = .078).
Conclusion: In this retrospective cohort study of pediatric patients undergoing cardiopulmonary bypass, there was no association between the use of aprotinin and acute kidney failure, need for dialysis, neurologic complications, and operative or late mortality. We continue to use aprotinin for all pediatric patients undergoing cardiopulmonary bypass.
| Introduction |
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Aprotinin (Trasylol; Bayer Pharmaceutical, West Haven, Conn) is an antifibrinolytic serine protease inhibitor purified from bovine lung. Aprotinin was approved by the US Food and Drug Administration to reduce perioperative blood loss in high-risk patients undergoing cardiopulmonary bypass (CPB) for coronary artery bypass grafting in 1993.1
Aprotinin reduces bleeding by delaying the rapid plasmin-mediated lysis of the fibrin clot. Several randomized, prospective, placebo-controlled, carefully performed trials on aprotinin use have shown that it reduces requirements for blood transfusion in adult cardiac surgery.2-4
Aprotinin has also been shown to decrease the inflammatory response to CPB.5,6
After completing an internal study that demonstrated that aprotinin reduced operative closure time and blood product use after pediatric cardiac bypass, our center began routinely using aprotinin in all of our patients undergoing CPB in early 2000.7
Several other pediatric cardiac surgery centers have shown that the use of aprotinin in pediatric patients undergoing CPB is associated with decreased use of blood products and cost savings from decreased operative time.8,9
Recently, the safety of aprotinin use in adult cardiac surgery has been called into question, particularly in 2 separate reports published by Mangano and colleagues.10,11
They reported that aprotinin use was associated with increased risk of perioperative acute kidney failure, cerebral vascular accidents, and long-term mortality. Both studies have elicited numerous letters to the editor and editorials.12-14
The purpose of our study was to determine whether the use of aprotinin was associated with adverse outcomes, particularly mortality and impairment of kidney function, in pediatric patients (<18 years of age) undergoing CPB. We also analyzed the patients with regard to postoperative new-onset neurologic injury. The conduct of this study was facilitated by our change in treatment protocols to include aprotinin in all of our patients undergoing CPB in early 2000. This study was not directed at the efficacy of aprotinin; it was limited to the safety issues recently raised.
| Materials and Methods |
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2 tests. All outcomes of interest were as follows: biochemical acute kidney failure, postoperative temporary dialysis, operative mortality, and late mortality are binary. In addition to aprotinin, predictors studied included age, sex, body surface area, operative status (emergency status vs nonemergency status), Aristotle score, deep hypothermic circulatory arrest (DHCA; yes vs no), preoperative ventilator support (yes vs no), prior open cardiothoracic operations (yes vs no), CPB time, aortic crossclamp time, and preoperative serum creatinine level. The data consisted of multiple operations per patient over the study period. The repeated nature of the data was taken into consideration in the regression analyses.
A Cox regression frailty model (Therneau) with a random effect for patient was used to determine predictors of late mortality.17
Time at risk was defined by using the Anderson–Gill approach. Time at risk for patients with multiple operations was from one surgical date to the next. Follow-up times were censored at April 27, 2007. A generalized linear model for binary outcome (Liang and Zeger) with logit link was used to determine predictors of the other 3 outcomes. Repeated measures were modeled by using compound symmetry structure.18
The overall strategy was to use results from univariate associations as a data reduction tool to identify candidates for a multiple-predictor model. Univariate models included each predictor one at a time, controlling for aprotinin. A P value of .1 determined inclusion in a multiple-predictor model in addition to predictors that were statistically significantly different between the 2 study groups. In addition, the interaction effect between aprotinin and risk stratification based on the median Aristotle score was explored. Separate models for each level were considered if this effect was statistically significant. Power considerations allowed for multiple-predictor models for biochemical acute kidney failure and operative mortality outcomes. Odds ratios and corresponding 95% confidence intervals are presented for statistically significant categorical predictors. The incidence of neurologic outcomes was low, and hence the
2 test was used to test the association between aprotinin and outcome if adverse outcomes were observed in at least 10 operations. The low incidence did not allow for repeated-measures analyses of multiple operations.
Statistical analyses were conducted with SAS statistical software (version 9.1; SAS, Cary, NC) and S-Plus (version 6.2; Insightful Corp, Seattle, Wash). All conclusions were made at the .05 level of significance.
| Results |
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Temporary Dialysis
In the no-aprotinin group 6 (0.49%) of 1229 patients required temporary dialysis in the postoperative period. In the aprotinin group this was 12 (0.96%) of 1251 (P = .166). Temporary dialysis was associated with a 61% mortality rate because 11 of these 18 patients died. It should be noted that all of these were very complex procedures; no patient who had a straightforward cardiac procedure had postoperative acute kidney failure. The mean Aristotle score of the no-aprotinin group to require dialysis was 7.7, and the mean score in the aprotinin group requiring dialysis was 10.1. Mortality related to temporary dialysis was similar in both groups. There were 5 (0.41%) deaths in dialyzed patients in the no-aprotinin group and 6 (0.48%) deaths in dialyzed patients in the aprotinin group (P > .99). There was no power for multivariable models beyond the 2 predictor models. Odds ratios for predictors are from the univariate model. Predictors of temporary dialysis were emergency status, use of DHCA, preoperative ventilator support, higher Aristotle score, longer CPB time, and higher preoperative serum creatinine level (Table 6). No patient required permanent dialysis.
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Adverse Reactions and Re-exposures
Two patients had a possible anaphylactic reaction to aprotinin. In both cases it was their first exposure to the drug, and neither patient had a reaction to the initial test dose. The first patient became hypotensive on aprotinin administration, with a decrease in systolic blood pressure from 110 to 50 mm Hg. Systolic blood pressure recovered to baseline after discontinuation of aprotinin and with administration of dopamine and fluids. The second patient had decreased lung compliance after aprotinin administration, necessitating discontinuation of aprotinin. The patient recovered to baseline pulmonary function after administration of epinephrine boluses and dopamine.
There were 91 patients who were re-exposed to aprotinin once within 1 year of their first exposure. Three additional patients were re-exposed more than once within a year of their exposure to aprotinin. No adverse events were associated with re-exposure to aprotinin in this series.
Late Mortality
As determined by means of Cox regression analysis, aprotinin had no influence on late mortality (24 deaths in the no-aprotinin group vs 10 deaths in the aprotinin group, P = .078). This analysis was of course complicated by the separate time cohorts, with significantly more follow-up in the no-aprotinin group. However, this was counterbalanced by the relatively short mean time to late mortality in all groups. The mean time to late death in all groups was 1.7 ± 2.3 years (median, 0.77 years). In the no-aprotinin group mean time to late death was 2.23 ± 2.49 years (median, 1.3 years), and in the aprotinin group mean time to late death was 0.44 ± 6.5 years (median, 0.22 years). The mean follow-up time in the no-aprotinin group was 8.54 ± 3.79 years (median, 9.4 years), and in the aprotinin group the mean follow-up was 3.47 ± 1.99 years (median, 3.3 years). Mean and median follow-up times in the aprotinin group encompass the mean and median times to late mortality. Table 7
shows the predictors of late mortality. These included preoperative ventilator support, preoperative emergency status, prior open cardiothoracic operation, higher Aristotle score, and longer CPB time.
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The analyses of aprotinin risk in relation to postoperative neurologic deficit and seizure are based on complication incidence, as recorded in our comprehensive cardiac surgery database. We found no statistically significant difference between the 2 groups for either outcome. However, these patients did not have routine postoperative examinations by a neurologist or routine postoperative neurologic imaging, and therefore this analysis is not comprehensive. Manifestations of neurologic injury can be subtle and might only become evident over time.
| Discussion |
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The impetus for this study was the recent article, "The risk associated with aprotinin in cardiac surgery," by Mangano and associates.10
This was a propensity-adjusted observational study that reported that aprotinin use (n = 1295) was associated with a doubling of the risk of perioperative acute kidney failure and cerebral vascular accidents in patients undergoing CPB grafting. This study has elicited numerous letters to the editor and editorials and has called into question the use of aprotinin for patients undergoing CPB.12,14
Another report from Mangano and associates11
correlated the use of aprotinin (n = 1072) with a significantly increased late mortality in patients undergoing coronary artery bypass graft surgery. This report was also the subject of an editorial response.14
The primary questions raised regarding the Mangano studies are related to the reason the patients receive the drug therapy (aprotinin) in the first place and the influence of that selection bias on the patient data collection process and analysis and patient outcomes.12-14
Our review would indicate that for pediatric patients, the use of aprotinin (n = 1251) was not associated with an increase in the risk of biochemical acute kidney failure, need for dialysis, or neurologic complications and also was not associated with increased risk of operative or late mortality. This was despite the fact that the aprotinin group of patients was statistically younger and had a higher Aristotle score.
One counterintuitive finding was that the preoperative serum creatinine level in the patients who had biochemical acute kidney failure was less preoperatively than the level in those patients who did not have biochemical acute kidney failure. The answer to why the lower serum creatinine value was a predictor of postoperative acute kidney failure is probably explained by the fact that younger children tended to have kidney failure (2.0 vs 3.5 years). The younger cohort of children has a lower muscle mass and therefore a lower serum creatinine level as normal baseline. Our definition of biochemical acute kidney failure as an increase in serum creatinine level to twice or more than the preoperative level uses each patients preoperative serum creatinine level as his or her own control, a practice that is consistent with our (Childrens Memorial Hospital) internal standard for the definition of acute kidney failure, as well as that of our cardiac surgery database (personal e-mail communication with J. P. Jacobs, Multi-Societal Pediatric and Congenital Cardiac Database Taskforce, 2007). In addition, it should be noted that although the preoperative serum creatinine values were lower in those children who had acute kidney failure, the respective values of 0.39 versus 0.51 mg/dL, although statistically different, are not clinically different.
It should be clearly noted that our study was not performed to demonstrate the efficacy of aprotinin in pediatric patients. There have been numerous previous studies to indicate that aprotinin is indeed efficacious in pediatric patients undergoing CPB. A recent meta-analysis by Arnold and colleagues20
reported that aprotinin reduced the proportion of children who received red blood cell or whole blood transfusions during cardiac surgery by 33%. Our own study published in 2003 demonstrated that with the use of aprotinin, children were exposed to 3 instead of 5 red blood cell units. Operative closure time was less (ie, 93 vs 127 minutes, a savings of 34 minutes). The Ann Arbor group in 1996 reported in a prospective, randomized, placebo-controlled, double-blind trial that aprotinin resulted in fewer exposures to bank-blood components and was also associated with a savings in the patient charges for blood components, operating room time, and duration of hospitalization.8
The group from Eggleston Childrens Hospital in 1998 reported similar findings.9
A recent study at the University of California, San Francisco, evaluated the use or nonuse of aprotinin in patients undergoing the Norwood, Glenn, and Fontan procedures. The authors concluded the following: "The key point of these data is that we did not see evidence of clinical concern in this population of children with ... aprotinin. If anything our data support the safety of these drugs for use in children undergoing the repair of congenital cardiac defects."21
The Milwaukee group, in particular, has demonstrated the utility and safety of aprotinin use and reuse in pediatric patients undergoing cardiothoracic procedures.22,23
They concluded that the risk of hypersensitivity reactions to aprotinin is low (approximately 1%), even with multiple exposures to the medication. Our analysis of the risk of re-exposure confirms the Milwaukee analysis; we had no adverse responses in 94 patients re-exposed within 1 year.
In our study of 2090 pediatric patients undergoing CPB, there was no association between the use of high-dose aprotinin and operative or late mortality, biochemical acute kidney failure, need for temporary dialysis, or neurologic complications. Given the previous studies demonstrating its efficacy, we continue to use aprotinin in all pediatric patients undergoing CPB.
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