Antifibrinolytic agents in cardiac surgery: Current controversies

[Haemorrhage and morbidity associated with the use of tranexamic acid in cardiac surgery: a retrospective, multicentre cohort study]

INTRODUCTION

Postoperative bleeding is common complication, affecting up to 20% of patients, after cardiac bypass surgery. Fibrinolysis is one of the causes of this excessive bleeding, and for this reason the use of tranexamic acid is recommended. The problem with using this is that there are numerous guidelines and differences in the dose to be administered. Our aim was to evaluate whether there were any differences in postoperative bleeding and morbidity after cardiac surgery with the administering of different tranexamic acid doses in three university hospitals.

MATERIAL AND METHODS

A retrospective, multicentre cohort study was conducted. A total of 146 patients who were subjected to elective cardiac bypass surgery according to the anaesthetic-surgical protocol of each hospital were included in the study. The clinical histories were reviewed, and they were divided into two groups according to the tranexamic acid dose: Group A (high doses), initial dose of 20mg/kg and continuous infusion of 4 mg/kg/hour until closure of the sternotomy. A further 100mg was added to prime the bypass machine. Group B (low doses), initial dose of 10mg/kg followed by a continuous infusion of 2mg/kg/hour until closure of the sternotomy. A further 50mg was added to prime the bypass machine. Variables, such as age, sex, weight, height, type of surgical procedure (valvular, coronary or mixed), haematocrit, INR, and preoperative platelet count, time and temperature of the bypass machine, and haematocrit on sternum closure, were recorded. Among the post-operative variables collected were: debit due to drainage at 6, 12 and 24 hours after surgery, number and type of blood products transfused in the first 24 hours, need for further surgery due to haemorrhage, CVA, TIA, or a new acute myocardial infarction, convulsions, and mortality.

RESULTS

The incidence of increased bleeding (patients in the 90 percentile) was higher in Group B at all the study evaluation times (P<.05). The incidence of further surgery due to bleeding, and the need for transfusion of ≥ 3 units of packed red cells was lower in Group A (5.56%) than in Group B (13.89%). There were no significant differences in the requirements for blood products transfusions between the groups. As regards associated morbidity, there was one isolated case of convulsion and a perioperative AMI in another case in Group A, and three cases of perioperative AMI in Group B.

CONCLUSIONS

Elevated doses of tranexamic acid in cardiac bypass surgery appear to significantly reduce bleeding in the first hours after surgery compared to low doses. However, this decrease did not lead to a reduction in the needs for blood products.

Off-pump coronary artery bypass: techniques, pitfalls, and results

In an attempt to advance the surgical treatment of coronary artery disease, surgeons sought a way to offer the proven benefits of coronary revascularization and avoid the side effects of cardiopulmonary bypass by performing revascularization in the beating heart (off-pump coronary artery bypass). This review will describe the development and refinement of the technique, pitfalls to its widespread adoption, and an up-to-date assessment of current results.

Tranexamic acid reduces postoperative bleeding in off-pump coronary artery bypass grafting

OBJECTIVE

Tranexamic acid (TA) reduces blood loss in coronary artery surgery with cardiopulmonary bypass. The present prospective study was designed to investigate its hemostatic effect in off-pump coronary artery bypass (OPCAB).

METHOD

Seventy-six patients undergoing elective OPCAB were randomized into two groups, received TA (0.75 g loading dose before surgery and 250 mg/h during surgery, gross dose: 1.5 g, n=36) and saline solution (control, n=40), respectively. Perioperative blood samples were collected. Hematochemical parameters including platelet adhesion rate, D-dimer and fibrinopeptide-A (FPA) were analysis. Volume of blood loss, blood transfusion and other clinical data were recorded throughout the perioperative period.

RESULTS

Cumulative blood loss was significantly reduced in the TA group as compared to the controls postoperatively (6 hrs (median [25th-75th]): TA: 200.0 [140.0-230.0] ml,

CONTROL

225.0 [200.0-347.5.0] ml, p=0.009; 24 hrs: TA: 440.0 [270.0-605.0] ml,

CONTROL

655.0 [500.0-920.0] ml, p<0.001). Number of patients received blood transfusion in each group was similar. Levels of D-dimer rose significantly after surgery, and were significantly lower in the TA group than that in controls. Platelet adhesion rate and FPA levels remained at baseline levels after the operation in two groups. Early clinical outcomes were similar between groups.

CONCLUSION

The results indicated that tranexamic acid limits fibrinolysis and reduces blood loss after off-pump coronary artery bypass surgery.

Evaluating the safety implications of aprotinin use: The Retrospective Evaluation of Aprotinin in Cardio Thoracic Surgery (REACTS)

OBJECTIVES

Aprotinin is a drug used to reduce bleeding in patients undergoing cardiothoracic surgery with cardiopulmonary bypass. A recent cohort evaluation found elevated risks of renal, cardiovascular, and cerebrovascular events when aprotinin was used. We sought to determine the impact of aprotinin on safety variables among patients receiving cardiothoracic surgery with cardiopulmonary bypass from a single US hospital that reserves aprotinin for complex surgeries and Jehovah's Witnesses and does not utilize celite-based activated clotting time determinations.

METHODS

We performed a cohort evaluation with multivariate logistic regression, including propensity score adjustment comprising patients from January 1, 2000 and December 31, 2005. We evaluated 3348 patients having cardiothoracic surgery in a single tertiary care medical center. We observed aprotinin use or lack of aprotinin in cardiothoracic surgery. The main outcome measures were odds (expressed as an odds ratio with 95% confidence interval) of developing myocardial infarction, cerebrovascular events, and renal dysfunction after cardiothoracic surgery between groups.

RESULTS

Patients receiving aprotinin were less likely to experience a cerebrovascular event compared with control [0.65 (0.46-0.91)] and did not have an elevated odds of myocardial infarction [1.04 (0.53-2.04)] but were more likely to experience postoperative renal dysfunction [2.03 (1.37-3.01)].

CONCLUSIONS

Aprotinin was not associated with negative myocardial or cerebrovascular risks but did increase the risk of renal dysfunction. It is not known whether the renal dysfunction reflects renal damage or a transient reduction in glomerular filtration pressure.

Efficacy and safety of aprotinin use for reoperative valvular surgery

BACKGROUND

Preservation of the hemostatic system during cardiac surgery is a main concern, primarily after repeated cardiac operations.

METHODS

We compared the outcomes of adult patients undergoing isolated reoperative valvular surgery receiving full-dose of aprotinin (redo group, n = 70) with patients experiencing primary isolated valvular surgery not receiving aprotinin (primary group, n = 135).

RESULTS

The mean age was lower in the redo group (45 +/- 14 years vs 50 +/- 17 years, p = 0.036). The redo group had more female patients (73% vs 51%, p = 0.003), patients in functional class IV (15% vs 4% p = 0.009), and patients with chronic atrial fibrillation (48% vs 24%, p = 0.001). The cardiopulmonary bypass duration was longer in the redo group (119 +/- 50 minutes vs 103 +/- 41 minutes, p = 0.014). However, the blood loss was significantly lower (300 +/- 279 mL vs 776 +/- 584 mL, p = 0.001) and fewer patients needed transfusions (3.0% vs 13%, p = 0.023) in the redo group. The postoperative morbidity was similar in both groups. The postoperative in-hospital mortality was 7% in the primary group and 10% in the redo group (p = 0.419). Factors associated with postoperative in-hospital mortality were the following: age greater than 60 years (p = 0.040, odds ratio [OR] 3.0), New York Heart Association class IV (p = 0.022, OR 5.0), preoperative critical state (p < 0.001, OR 12), emergent operation (p = 0.012, OR 7.0), endocarditis (p = 0.004, OR 10.0), and reoperation due to mechanical mitral prosthesis dysfunction (p = 0.009, OR 7).

CONCLUSIONS

The mortality and morbidity in redo valve surgery with aprotinin administration was comparable with primary valve surgery without aprotinin. Bleeding and transfusion requirements were significantly lower in redo patients receiving aprotinin.