Coronary artery bypass graft surgery—care globalization: The impact of national care on fatal and nonfatal outcome

The current place of aprotinin in the management of bleeding

There is a considerable difference between the mechanism of action of the lysine analogues, tranexamic acid and epsilon-aminocaproic acid, and the serine protease inhibitor aprotinin. Aprotinin acts to inactivate free plasmin, but with little effect on bound plasmin, whereas the lysine analogues are designed to prevent excessive plasmin formation by fitting into plasminogen's lysine-binding site to prevent the binding of plasminogen to fibrin. Aprotinin is associated with a reduction in bleeding and transfusion requirements following major surgery, and has a dose-response profile, compared with no dose-response effect in the one study investigating tranexamic acid in cardiac surgical patients. Following its withdrawal in 2007, which is explained in detail in this review, the regulators have now licensed aprotinin for myocardial revascularisation only, which is relatively low-risk for bleeding.

Effect of hospital culture on blood transfusion in cardiac procedures

BACKGROUND

In our effort to reduce the use of blood products in cardiac operations in a health care system, we noted variations in transfusion practices among facilities. Interestingly, surgeons practicing at the same hospital had similar transfusion rates. We sought to quantitate the contribution of hospital influence on individual surgeons' transfusion practices.

METHODS

Blood transfusion data for coronary artery bypass graft operations at 12 Providence Health & Services facilities between January 2008 and June 2011 were reviewed. Frequency of perioperative blood transfusion, amount of transfusion, components transfused, and timing of transfusions were compared. Variation among surgeons at the same institution vs between institutions was computed based on multilevel mixed-effect logistic and linear regression models. Intraclass correlation coefficients were calculated.

RESULTS

A total of 5,744 nonemergency first-time coronary artery bypass graft procedures were performed by 42 not-low volume (n>30 in 2.5 years) surgeons at 12 Providence Health & Services hospitals during the 3.5-year study period. Frequency, amount, timing, and blood component usage were different among facilities but relatively similar for surgeons within a facility. The variance of red blood cell transfusion rate among hospitals (.82) is more than two times that among surgeons practicing within the same hospital (.35). Thus, surgeons contribute 30% to the variation, and 70% of the total variation can be explained by the hospital effect.

CONCLUSIONS

In our multihospital system, the hospital that a surgeon practices at plays a larger role in determining blood utilization than the individual surgeon's preference.

Mechanical properties of cellulose: chitosan blends for potential use as a coronary artery bypass graft

The development of intimal hyperplasia is the major cause of failure of both autologous saphenous vein and synthetic coronary artery bypass grafts. This is partially due to graft-host vessel compliance mismatch. Cellulose and chitosan (CELL:CHIT) are both biocompatible, nontoxic, and naturally occurring biopolymers that have been used extensively for biomedical applications. Elastic properties of membranes made of CELL:CHIT blends with different ratios between each polymer were determined using uniaxial tests and the ratio that yielded the less stiff membrane was chosen to prepare a small diameter hollow tube. The presence of chitosan had a favorable impact on the elasticity of the membranes, where the CELL:CHIT 5:5 ratio showed the lowest Young's modulus. Small diameter tubular constructs were fabricated using this optimal CELL:CHIT ratio and the compliance was determined on samples with different wall thickness and internal diameter. The compliance of the hollow tube with inner diameter of 4 mm and wall thickness of 1.2 mm was found to be 5.91%/mmHg×10(-2), which is higher than those of Dacron, expanded polytetrafluorethylene, and saphenous vein, but very close to that of human coronary artery. Burst strength tests revealed that the tubes can withstand at least 300 mmHg. Finally, the tubes showed satisfactory cell attachment property when myofibroblast cells adhered and proliferated on the lumen of the samples.

Anticoagulation monitoring during extracorporeal circulation with the Hepcon/HMS device

Objective: The objective of our study was to compare the standard protocol of anticoagulation to the Hepcon/HMS.

Method: This study included forty-four patients who underwent coronary bypass grafting surgery (CABG), or biological aortic valve replacement (AVR). Unfractionated heparin (UH) was used for patients who underwent operations in the control group (n = 22) (300U/Kg of UH with a goal of an ACT of 400s). The heparin was antagonized dose/dose by protamine. For the patients who underwent operations in the HMS group (n = 22), the heparin and protamine doses were assessed by the Hepcon/HMS device.

Results: The sex ratio amounted to 1.93 (29 men and 15 women) and the mean age was 70 ± 11 years. The patients in the HMS group had a chest closure time that was significantly shorter than patients in the control group. The times were, respectively, 42 ± 15 minutes and 68 ± 27 minutes (p = 0.001). The protamine/heparin ratio was significantly lower in the HMS group (0.62 ± 0.13 vs. 1 ± 0.11) (p = 0.0001). The postoperative bleeding amounted to 804 ± 729 ml in the HMS group versus 1416 ± 1103 in the control group (p = 0.016). In multivariate linear regression analysis, only two independent factors were significantly associated with bleeding: the Hepcon/HMS (OR = 0.1-p = 0.03) and the preoperative hemoglobin rate (OR = 1.4 - p = 0.05). Postoperatively, within 72 hours, the red blood cell transfusion was 1.04 ± 1.5 units for the HMS group and 2.1 ± 1.87 units for the control group (p = 0.05).

Conclusion: During cardiac surgery under CPB, heparin and protamine titration with the Hepcon/HMS device could predict a lower protamine dose and lower postoperative bleeding without higher thromboembolic events, and lower perioperative red blood cell transfusion with a shorter chest closure time.

Risks and predictors of blood transfusion in pediatric patients undergoing open heart operations

BACKGROUND

Blood transfusion in adults is associated with increased mortality and morbidity after cardiac operations. The aim of this study was to identify the main predictors of blood transfusion and explore the relationship between blood transfusion and adverse outcomes in a pediatric population.

METHODS

We retrospectively analyzed a prospectively collected database (January 2002 to December 2003) of 657 consecutive pediatric patients undergoing open heart procedures in a tertiary pediatric cardiac center. Risk models were calculated for each blood product and for the total amount of blood transfused during the operation and in the first 24 hours. Postoperative adverse events were investigated after propensity score adjustment.

RESULTS

During the postoperative period, 30 patients (4.6%) died, 80 (12.2%) sustained nonvascular pulmonary complications, and 113 (17.2%) had infection. The risk model for the total amount of blood transfusion included weight, preoperative creatinine clearance, preoperative mechanical ventilation, duration of operation and cross-clamp, surgeon, delayed chest closure, inotropic dose, and nitric oxide administration. Univariate analyses demonstrated significant associations between blood transfusion and occurrence of every complication except of neurologic events. After adjustment for propensity score and disease severity, the total amount of blood transfusion was independently associated with an increased risk for infections (odds ratio, 1.01; 95% confidence interval, 1.002 to 1.02; p = 0.01). Transfusion of platelets was associated with lower incidence of nonvascular pulmonary complications (odds ratio, 0.89; 95% confidence interval, 0.79 to 0.99; p = 0.049).

CONCLUSIONS

The amount of blood transfusion is independently associated with infections but not with mortality.

Aprotinin and renal dysfunction

Aprotinin is a polypeptide serine protease inhibitor used to prevent bleeding and need for transfusions in patients having heart surgery. A recent analysis of an observational study data set suggested the use of aprotinin was associated with an increased risk of developing renal failure. The present article reviews the data from basic science studies in tissues, animals and man together with the data from observational studies and randomised controlled trials. The interpretation of the data is hampered owing to the use of different endpoints to describe mild/moderate renal impairment. Nonetheless, the evidence points to aprotinin use being associated with a transient small rise in plasma creatinine concentration in certain patients. There is no evidence for an increased risk of developing new renal failure requiring dialysis/renal replacement therapy.

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).

Retrospective cross-validation of simplified predictive index for renal replacement therapy after cardiac surgery

OBJECTIVES

Acute kidney impairment requiring renal replacement therapy is an infrequent but dangerous complication of cardiac surgery. Its development is associated with high mortality and morbidity. A recently published simple risk stratification engine has been developed and validated in the USA and Canada, but its discriminatory power has never been tested in Europe. We aimed to cross-validate the newly developed risk stratification algorithm in a group of patients operated on in a single centre in Poland.

METHODS

From electronic database we selected 1421 patients fulfilling identical inclusion and exclusion criteria as in derivation cohort in Canada. In each patient eligible for analysis we calculated simplified renal index and assessed its predictive power for the need of renal replacement therapy.

RESULTS

After surgery 33 (2.3%) patients developed acute kidney impairment and subsequently underwent renal replacement therapy. The simplified renal index predicted risk of postoperative renal replacement therapy in our group. Patients with low values of simplified renal index (0-1), medium (2-3) and high values (4 and more) were found to have increasingly higher risk for renal replacement therapy of 1.1% (95% CI: 0.5-2.1%), 3.2% (95% CI: 1.9-5%) and 12.5% (95% CI: 5.2-24.1%), respectively. The area under the ROC curve of simplified renal index as predictor of renal replacement therapy in our centre was 0.73 (95% CI: 0.62-0.81) and did not differ significantly from the values obtained in the original paper.

CONCLUSION

The new risk stratification algorithm is effective in discrimination of patients at high risk for development of acute kidney impairment with the need of renal replacement therapy.