Learning from aprotinin--mandatory trials of comparative efficacy and safety needed

Tranexamic acid use during total hip arthroplasty: A single center retrospective analysis

BACKGROUND

Tranexamic acid (TXA) is an antifibrinolytic agent that has shown promise in reducing blood loss during total hip arthroplasty (THA). Several studies have reported side effects of high-dose TXA administration, including myocardial infarction (MI), thromboembolic events, and seizures. These possible side effects have prevented the widespread adoption of TXA in the surgical community.

METHODS

We conducted a retrospective chart review of 564 primary and revision THAs performed at a single academic center. Surgical patients received either no TXA or 1 g IV TXA at the beginning of surgery followed by a second bolus just before the surgical wound closure, at the surgeon's discretion. We analyzed differences in hemoglobin (Hb), hematocrit (Hct), estimated blood loss (EBL), and adverse events in patients receiving TXA versus patients not receiving TXA up to 2 days following surgery.

RESULTS

Significantly higher Hb and Hct values were found across all time points among patients undergoing primary posterior or revision THA who had received TXA. In addition, transfusion rates were significantly decreased in both primary posterior THAs and revision THAs when TXA was administered. Patients who received TXA experienced significantly fewer adverse events than those who did not for all surgery types.

CONCLUSION

Administration of low-dose intravenous (IV) and intra-articular (IA) TXA does not appear to increase rates of adverse events and may be effective in minimizing blood loss, as reflected by Hb and Hct values following THA.

A new prize system for drug innovation

We propose a new prize (reward) system for drug innovation which pays a price based on the value of health benefits accrued over time. Willingness to pay for a unit of health benefit is determined based on the cost-effectiveness ratio of palliative/nursing care. We solve the problem of limited information on the value of health benefits by mathematically relating reward size to the uncertainty of information including information on potential drug overuse. The proposed prize system offers optimal incentives to invest in research and development because it rewards the innovator for the social value of drug innovation. The proposal is envisaged as a non-voluntary alternative to the current patent system and reduces excessive marketing of innovators and generic drug producers.

Seizures after open heart surgery: comparison of ε-aminocaproic acid and tranexamic acid

OBJECTIVE

Although the lysine analogs tranexamic acid (TXA) and aminocaproic acid (EACA) are used widely for antifibrinolytic therapy in cardiac surgery, relatively little research has been performed on their safety profiles, especially in the setting of cardiac surgery. Two antifibrinolytic protocols using either TXA or aminocaproic acid were compared according to postoperative outcome.

DESIGN

A retrospective analysis.

SETTING

A university-affiliated hospital.

PARTICIPANTS

Six hundred four patients undergoing cardiac surgery.

INTERVENTIONS

One cohort of 275 consecutive patients received TXA; a second cohort of 329 consecutive patients was treated with EACA. Except for antifibrinolytic therapy, the anesthetic and surgical teams and their protocols remained unchanged.

MEASUREMENTS AND MAIN RESULTS

Besides major outcome criteria, namely postoperative bleeding, the need for allogeneic transfusions, operative revision because of bleeding, postoperative renal dysfunction, neurologic events, heart failure, and in-hospital mortality, the authors specifically sought differences between the groups concerning seizures. The 2 cohorts were comparable over a range of perioperative factors. Postoperative seizures occurred significantly more frequently in TXA patients (7.6% v 3.3%, p = 0.019), whereas EACA patients had a higher incidence of postoperative renal dysfunction (20.0% v 30.1%, p = 0.005). There were no differences in all other measured major outcome factors.

CONCLUSION

Both lysine analogs are associated with significant side effects, which must be taken into account when performing risk-benefit analyses of their use. Their use should be restricted to patients at high risk for bleeding; routine use on low-risk patients undergoing standard surgeries should face renewed critical reappraisal.

Platelet-rich-plasmapheresis for minimising peri-operative allogeneic blood transfusion

BACKGROUND

Concerns regarding the safety of transfused blood have generated considerable enthusiasm for the use of technologies intended to reduce the use of allogeneic blood (blood from an unrelated donor). Platelet-rich plasmapheresis (PRP) offers an alternative approach to blood conservation.

OBJECTIVES

To examine the evidence for the efficacy of PRP in reducing peri-operative allogeneic red blood cell (RBC) transfusion, and the evidence for any effect on clinical outcomes such as mortality and re-operation rates.

SEARCH STRATEGY

We identified studies by searching MEDLINE (1950 to 2009), EMBASE (1980 to 2009), The Cochrane Library (Issue 1, 2009), the Internet (to March 2009) and the reference lists of published articles, reports, and reviews.

SELECTION CRITERIA

Controlled parallel group trials in which adult patients, scheduled for non-urgent surgery, were randomised to PRP, or to a control group which did not receive the intervention.

DATA COLLECTION AND ANALYSIS

Primary outcomes measured were: the number of patients exposed to allogeneic RBC transfusion, and the amount of RBC transfused. Other outcomes measured were: the number of patients exposed to allogeneic platelet transfusions, fresh frozen plasma, and cryoprecipitate, blood loss, re-operation for bleeding, post-operative complications (thrombosis), mortality, and length of hospital stay. Treatment effects were pooled using a random-effects model. Trial quality was assessed using criteria proposed by Schulz et al (Schulz 1995).

MAIN RESULTS

Twenty-two trials of PRP were identified that reported data for the number of patients exposed to allogeneic RBC transfusion. These trials evaluated a total of 1589 patients. The relative risk (RR) of exposure to allogeneic blood transfusion in those patients randomised to PRP was 0.73 (95%CI 0.59 to 0.90), equating to a relative risk reduction (RRR) of 27% and a risk difference (RD) of 19% (95%CI 10% to 29%). However, significant heterogeneity of treatment effect was observed (p < 0.00001; I² = 79%). When the four trials by Boldt are excluded, the RR is 0.76 (95% CI 0.62 to 0.93). On average, PRP did not significantly reduce the total volume of RBC transfused (weighted mean difference [WMD] -0.69, 95%CI -1.93 to 0.56 units). Trials provided inadequate data regarding the impact of PRP on morbidity, mortality, and hospital length of stay. Trials were generally small and of poor methodological quality.

AUTHORS' CONCLUSIONS

Although the results suggest that PRP is effective in reducing allogeneic RBC transfusion in adult patients undergoing elective surgery, there was considerable heterogeneity of treatment effects and the trials were of poor methodological quality. The available studies provided inadequate data for firm conclusions to be drawn regarding the impact of PRP on clinically important endpoints.

Outcomes research using quality improvement databases: evolving opportunities and challenges

The challenges to prospective randomized controlled trials have necessitated the exploration of observational data sets that support research into the predictors and modulators of preoperative adverse events. The primary purpose and design of quality improvement databases is quality assessment and improvement at the local, regional, or national level. However, these data can also provide the opportunity to robustly study specific questions related to patient outcomes with no additional clinical risk to the patient. The virtual explosion of anesthesia-related registries has opened seemingly limitless opportunities for outcomes research in addition to generating hypothesis for more rigorous prospective analysis.

Aprotinin and classic wound drainage are unnecessary in total hip replacement - a prospective randomized trial

BACKGROUND

Classic wound drainage is still common in hip replacement but its benefit is doubtful. The role of systemic administration of proteinase inhibitors like aprotinin to avoid perioperative blood loss is still unclear.

PATIENTS AND METHODS

In a prospective randomized trial, the perioperative blood loss in alloplastic hip replacement under the influence of proteinase inhibitor (aprotinin, Trasylol®) using wound drainage as well as compression treatment alone were compared. 80 patients were prospectively randomized in 4 arms. Patients received either aprotinin or placebo during surgery as well as drainage or targeted external wound compression.

RESULTS

Observing the "drug therapy" aprotinin had no effect on the intra- or postoperative blood loss (p>0.05), a trend to lower postoperative hemoglobin decline was found, but without significance. Thrombosis occurred in neither the aprotinin nor in the placebo group. Two patients had a severe allergic drug reaction and were excluded from the study. Under "non drug therapy" with compression therapy and wound drainage a significant difference in blood loss was found (p<0.001). The blood loss was higher under the wound drainage. There was no influence on the infection rate. Yet we could observe increased bruising under the sole external compression treatment.

CONCLUSION

The administration of aprotinin did not achieve the desired reduction of perioperative blood loss. Hence, costs and two severe allergic drug reactions in our study represent arguments against its use in regular treatment. Furthermore, it seems that wound drainage is neglectable in hip replacement and can be substituted by a sole compression treatment.

Aprotinin in severe acute pancreatitis

Aprotinin, a Kunitz protease inhibitor, has a wide inhibitory action with particular activity against trypsin, chymotrypsin and kallikrein, making it theoretically attractive in ameliorating the effects of acute pancreatitis. Its use in acute pancreatitis has been studied for the last 50 years with disappointing results. In this paper, we review the previous studies and argue that all the studies have not been adequately powered, have inappropriate end-points, but most importantly have not attained adequate plasma and peritoneal levels of aprotinin to produce sufficient inhibitory activity. We hypothesise that a well-powered study with adequate aprotinin dosing may clarify its clinical benefit in severe acute pancreatitis.

The year in cardiothoracic and vascular anesthesia: selected highlights from 2008

The 2008 highlights in cardiovascular and thoracic anesthesia include the ultimate departure of aprotinin from clinical practice. However, a new antihypertensive drug, clevidipine, was approved for perioperative control of hypertension. There were also advances in pharmacologic myocardial conditioning with agents such as cyclosporine, sodium nitroprusside, and levosimendan. Furthermore, ischemic preconditioning appears ready for testing in large clinical trials designed to improve ischemic outcomes after cardiac surgery. With regard to transfusion, a landmark study suggests that transfused red blood cells stored for >2 weeks may significantly worsen major outcome after cardiac surgery. Furthermore, a second study suggests that relative rather than absolute hemoglobin reduction significantly determines adverse outcomes after cardiac surgery. These studies may greatly affect future transfusion guidelines. Left-sided valve replacement has been revolutionized by transcatheter technology, which progressed significantly in 2008. Important advances in percutaneous coronary intervention included drug-eluting bioabsorbable stents and further insights into the clinical consequences of platelet resistance. These 2008 themes represent a sampling of the total highlights for the year. Many of the advances not covered have been reviewed and discussed in the literature review sections of the Journal in 2008.

The aprotinin saga and the risks of conducting meta-analyses on small randomised controlled trials - a critique of a Cochrane review

Background

Aprotinin for reducing blood loss during coronary artery bypass surgery was withdrawn from the market after early termination of a large randomised controlled trial (RCT) showing excess mortality for patients receiving aprotinin compared to lysine analogues. Several meta-analyses of small RCTs did not show excess mortality and even indicated reduced mortality, while several observational studies showed excess mortality. The aim of this paper is to review the quality of the meta-analysis of a Cochrane report.

Methods

The 52 studies included in the meta-analysis of the Cochrane report were reviewed according to whether an objective to study mortality was formulated in advance, whether follow-up method or time were specified, and whether the study had statistical power to show any effect.

Results

The Cochrane report restricted the analysis to RCTs, but the largest study should not have been included given that it was a prospective observational study with 1 784 patients rather than an RCT. None of the RCTs had sufficient statistical power to detect differences in mortality. Most studies had fewer than 100 patients. Seven out of 51 RCTs had mortality outcome as one of their objectives. Only very few described follow-up method or time.

Conclusion

It is doubtful whether small studies should be included in meta-analyses if they do not have the purpose of studying the specified outcome and if the follow-up method or time are not adequately described. The aprotinin saga shows overconfidence in small RCTs of inferior quality compared to well-conducted observational studies.

The risks of aprotinin and tranexamic acid in cardiac surgery: a one-year follow-up of 1188 consecutive patients

BACKGROUND

Our aim was to investigate postoperative complications and mortality after administration of aprotinin compared to tranexamic acid in an unselected, consecutive cohort.

METHODS

Perioperative data from consecutive cardiac surgery patients were prospectively collected between September 2005 and June 2006 in a university-affiliated clinic (n = 1188). During the first 5 mo, 596 patients received aprotinin (Group A); in the next 5 mo, 592 patients were treated with tranexamic acid (Group T). Except for antifibrinolytic therapy, the anesthetic and surgical protocols remained unchanged.

RESULTS

The pre- and intraoperative variables were comparable between the treatment groups. Postoperatively, a significantly higher incidence of seizures was found in Group T (4.6% vs 1.2%, P < 0.001). This difference was also significant in the primary valve surgery and the high risk surgery subgroups (7.9% vs 1.2%, P = 0.003; 7.3% vs 2.4%, P = 0.035, respectively). Persistent atrial fibrillation (7.9% vs 2.3%, P = 0.020) and renal failure (9.7% vs 1.7%, P = 0.002) were also more common in Group T, in the primary valve surgery subgroup. On the contrary, among primary coronary artery bypass surgery patients, there were more acute myocardial infarctions and renal dysfunction in Group A (5.8% vs 2.0%, P = 0.027; 22.5% vs 15.2%, P = 0.036, respectively). The 1-yr mortality was significantly higher after aprotinin treatment in the high risk surgery group (17.7% vs 9.8%, P = 0.034).

CONCLUSION

Both antifibrinolytic drugs bear the risk of adverse outcome depending on the type of cardiac surgery. Administration of aprotinin should be avoided in coronary artery bypass graft and high risk patients, whereas administration of tranexamic acid is not recommended in valve surgery.

Tranexamic acid and aprotinin in primary cardiac operations: an analysis of 220 cardiac surgical patients treated with tranexamic acid or aprotinin

BACKGROUND

Antifibrinolytics are widely used in cardiac surgery to reduce bleeding. Allogeneic blood transfusion, even in primary cardiac operations with low blood loss, is still high. In the present study we evaluated the impact of tranexamic acid compared to aprotinin on the transfusion incidence in cardiac surgical patients with low risk of bleeding.

METHODS

This prospective, randomized, double-blind study included 220 patients undergoing primary coronary artery revascularization (coronary artery bypass grafting [CABG]) or aortic valve replacement (AVR). Randomized in blocks of 20, patients received either tranexamic acid (approximately 6 g) or full-dose aprotinin (approximately 5-6 x 10(6) Kallikrein Inhibiting Units). Transfusion was guided by a strict transfusion algorithm. Molecular markers of hemostasis were determined to assess differences in the mode of action of the two drugs. Primary end-points were the incidence of allogeneic red cell transfusion and 24-h postoperative blood loss. Data were analyzed according to the intention-to-treat principle and compared using the chi(2) and Mann-Whitney U-test.

RESULTS

Two-hundred-twenty patients were enrolled (CABG: 134, AVR: 86). In the aprotinin Group 47% of patients received allogeneic blood during the hospital stay as compared to 61% in the tranexamic acid group (P = 0.036). Aprotinin conferred a 23% reduction in allogeneic transfusion risk (RR 0.77, 95% CI 0.53-0.88). Overall, no significant difference in postoperative bleeding was observed, although 24-h blood loss was reduced in aprotinin-treated CABG patients (500, 350-750 mL vs 650, 475-875 mL (median, 25th-75th percentile); P = 0.039). Despite the lower transfusion rate, the hemoglobin concentration on the first postoperative day was higher in the aprotinin group (11.3, 9.9-12.1 vs 10.6, 9.9-11.6 mg/dL; P = 0.023). The fibrinolytic activity at the end of operation determined by D-Dimer was comparable in both groups. (0.15, 0.11-0.17 mg/L [aprotinin] versus 0.18, 0.12-0.24 mg/L [tranexamic acid]). The activated partial thromboplastin time was prolonged up to 4 h postoperatively in the aprotinin group, while the heparin requirement was reduced: 19% of the patients in the aprotinin group and 45% in the tranexamic acid group received at least one additional bolus heparin during cardiopulmonary bypass (P < 0.001). Troponin T levels postoperatively and on postoperative day 1 were significantly higher in the tranexamic acid group (P = 0.017). No differences in renal, cardiac, or mortality outcomes were observed.

CONCLUSION

Considering the rate of transfusion of red blood cells, tranexamic acid was slightly inferior in patients undergoing CABG, but there was no difference in patients receiving AVR. Tranexamic acid seems to be less effective in operations with increased bleeding such as CABG. Clinical benefit depends on specific patient and institution characteristics (ClinicalTrials.gov NCT00396760).

Aprotinin exacerbates left ventricular dysfunction after ischemia/reperfusion in mice lacking tumor necrosis factor receptor I

Aprotinin is a serine protease inhibitor with diverse biological effects; until recently, it was utilized in the context of ischemia/reperfusion (I/R). It has been hypothesized that a signaling pathway modulated by aprotinin in the context of I/R is the tumor necrosis factor-alpha receptor (TNFR) pathway. An intact mouse model of I/R (30 min ischemia and 60 min reperfusion) was used and left ventricular (LV) peak + maximal rate of left ventricular (LV) peak pressure (dP/dt) was measured in wild-type mice (WT, C57BL/6; n = 10), WT mice with aprotinin (4 mL/kg; n = 10), transgenic mice devoid of the TNFRI (TNFRI-null; n = 10), and TNFRI-null with aprotinin (n=10). Following I/R, LV peak + dP/dt decreased in both WT groups, but remained similar to baseline values in the TNFRI-null group. In contrast, aprotinin caused a marked reduction in LV peak + dP/dt in the TNFRI-null group following I/R. Soluble plasma TNF levels increased in the WT and TNFRI-null mice with I/R and was reduced with aprotinin. Soluble TNFRI and TNFRII levels, indicative of TNF activation, increased in the WT mice following I/R and remained elevated with aprotinin. Soluble TNFRII levels were increased in the TNFRI-null mice following I/R and remained elevated with aprotinin. The new and unique findings of this study were twofold. First, aprotinin failed to improve LV function after I/R despite a reduction in circulating TNF levels. Second, genetic ablation of TNFRI uncovered a negative inotropic effect of aprotinin. These findings demonstrate that complex biological pathways and interactions are affected with broad spectrum serine protease inhibition, which are relevant to myocardial function in the context of I/R.

Platelet-rich-plasmapheresis for minimising peri-operative allogeneic blood transfusion

BACKGROUND

Concerns regarding the safety of transfused blood have generated considerable enthusiasm for the use of technologies intended to reduce the use of allogeneic blood (blood from an unrelated donor). Platelet-rich plasmapheresis (PRP) offers an alternative approach to blood conservation.

OBJECTIVES

To examine the evidence for the efficacy of PRP in reducing peri-operative allogeneic red blood cell (RBC) transfusion, and the evidence for any effect on clinical outcomes such as mortality and re-operation rates.

SEARCH STRATEGY

Studies were identified by: computer searches of MEDLINE, EMBASE, Current Contents, and the Cochrane Library (to June 2001). These searches were supplemented by checking the reference lists of published articles, reports, and reviews.

SELECTION CRITERIA

Controlled parallel group trials in which adult patients, scheduled for non-urgent surgery, were randomised to PRP, or to a control group who did not receive the intervention.

DATA COLLECTION AND ANALYSIS

Main outcomes measured were: the number of patients receiving an allogeneic RBC transfusion, and the amount of RBC transfused. Trial quality was assessed using criteria proposed by Schulz et al. (Schulz 1995) and Jadad et al. (Jadad 1996).

MAIN RESULTS

Nineteen trials of PRP were identified that reported data for the number of patients exposed to allogeneic RBC transfusion. These trials evaluated a total of 1452 patients. The pooled relative risk (RR) of exposure to allogeneic blood transfusion in those patients randomised to PRP was 0.71 (95%CI: 0.56, 0.90), equating to a relative risk reduction (RRR) of 29%; the average absolute risk reduction (ARR) was 19% (RD = -0.19: 95%CI: -0.29, -0.09). On average, PRP did not significantly reduce the total volume of RBC transfused (weighted mean difference [WMD] = -0.69: 95%CI: -1.93, 0.56 units). Substantial statistical heterogeneity was observed (p < 0.001). Trials provided inadequate data regarding the impact of PRP on morbidity, mortality, and hospital length of stay. The majority of trials were small and of poor methodological quality.

REVIEWER'S CONCLUSIONS

Although the results suggest that PRP is effective in reducing allogeneic RBC transfusion in adult patients undergoing elective surgery, there was considerable heterogeneity in treatment effects and the trials were of poor methodological quality. As the majority of trials were unblinded, transfusion practices may have been influenced by knowledge of the patient's allocation status, potentially exaggerating the true magnitude of the beneficial effect of PRP. The available studies provided inadequate data for firm conclusions to be drawn regarding the impact of PRP on clinically important endpoints.