Heparin anticoagulation in patients undergoing off-pump and on-pump coronary bypass surgery

Optimum heparin dose in off-pump coronary artery bypass grafting: A systematic review and meta-analysis

INTRODUCTION

Off-pump coronary artery bypass grafting (OPCABG) was introduced many years ago aiming to reduce the known complications of conventional on-pump coronary surgeries. Heparin is required during the procedures, but the available protocols have diverse dosage regimens. The primary objective of this systematic review is to examine the effect of different heparin doses on the outcomes of OPCABG.

EVIDENCE ACQUISITION

MEDLINE and EMBASE were searched. Four reviewers identified eligible clinical trials. Two reviewers extracted data and independently assessed the risk of bias using Cochrane tool. The primary outcome was the activated clotting time (ACT) at three minutes. The secondary outcomes were proportion of patients requiring blood products and the length of hospital stay. An aggregate data approach was used.

EVIDENCE SYNTHESIS

Three single-center randomized studies recruiting 256 patients were included. The studies compared low-dose (1.5-2 mg/kg) and high-dose (3 mg/kg) heparin boluses. The overall mean difference for ACT after three minutes between low- and high-dose heparin is - 126.16 (95% CI: - 142.19, - 110.14). The proportion of patients requiring blood products after surgery [odd ratio 1.27 (95% CI: 0.69, 2.32)] or the overall length of stay [mean difference -0.15 (95% CI: -0.84, 0.53)] did not differ between the heparin doses.

CONCLUSIONS

In OPCABG, high-dose compared with low-dose heparin did not affect the utilization of more blood products or increased the overall length of stay. Unsurprisingly, ACT values were higher in the high-dose heparin group. Larger and adequately powered randomized clinical trials are indicated to resolve the uncertainty.

Comparison of two doses of heparin on outcome in off-pump coronary artery bypass surgery patients: A prospective randomized control study

Introduction:

While off pump coronary artery bypass surgery is practiced with an intention to reduce the morbidity associated with cardiopulmonary bypass, the resultant ‘hypercoagulability’ needs to be addressed. Complications such as cavitary thrombus possibly due to the hyper coagulability after off pump coronary artery bypass surgery have been described. Many clinicians use higher doses of heparin - up to 5 mg/kg in order to thwart this fear. Overall, there appears to be no consensus on the dose of heparin in off pump coronary artery bypass surgeries.

Aim of the Study:

The aim of the study was understand the differences in outcome of such as transfusion requirement, myocardial ischemia, and morbidity when two different doses were used for systemic heparinization.

Methods:

Elective patients scheduled for off pump coronary artery bypass surgery were included. Ongoing anti platelet medication was not an exclusion criteria, however, anti platelet medications were ceased about a week prior to surgery when possible. Thoracic epidural anesthesia was administered as an adjunct in patients who qualified for it. By computer generated randomization chart, patients were chosen to receive either 2 or 3 mg/kg of intravenous unfractioned heparin to achieve systemic heparinization with activated clotting time targeted at >240 secs. Intraoperative blood loss, postoperative blood loss, myocardial ischemic episodes, requirement of intraaortic balloon counter pulsation and transfusion requirement were analyzed.

Results:

Sixty two patients participated in the study. There was one conversion to cardiopulmonary bypass. The groups had comparable ACT at baseline (138.8 vs. 146.64 seconds, P = 0.12); 3 mg/kg group had significantly higher values after heparin, as expected. But after reversal with protamine, ACT and need for additional protamine was similar among the groups. Intraoperative (685.56 ± 241.42 ml vs. 675.15 ± 251.86 ml, P = 0.82) and postoperative blood loss (1906.29 ± 611.87 ml vs 1793.65 ± 663.54 ml, p value 0.49) were similar among the groups [Table 4]. The incidence of ECG changes of ischemia, arrhythmias, conversion to CPB, or need for intra-aortic balloon counter pulsation were not different.

Conclusions:

Use of either 2 or 3 mg/kg heparin for systemic heparinization in patients undergoing OPCAB did not affect the outcome.

A comparison of red blood cell transfusion utilization between anti-activated factor X and activated partial thromboplastin monitoring in patients receiving unfractionated heparin

Essentials Anti-activated factor X (Anti-Xa) monitoring is more precise than activated partial thromboplastin (aPTT). 20 804 hospitalized cardiovascular patients monitored with Anti-Xa or aPTT were analyzed. Adjusted transfusion rates were significantly lower for patients monitored with Anti-Xa. Adoption of Anti-Xa protocols could reduce transfusions among cardiovascular patients in the US.

SUMMARY

Background Anticoagulant activated factor X protein (Anti-Xa) has been shown to be a more precise monitoring tool than activated partial thromboplastin time (aPTT) for patients receiving unfractionated heparin (UFH) anticoagulation therapy. Objectives To compare red blood cell (RBC) transfusions between patients receiving UFH who are monitored with Anti-Xa and those monitored with aPTT. Patients/Methods A retrospective cohort study was conducted on patients diagnosed with acute coronary syndrome (ACS) (N = 14 822), diagnosed with ischemic stroke (STK) (N = 1568) or with a principal diagnosis of venous thromboembolism (VTE) (N = 4414) in the MedAssets data from January 2009 to December 2013. Anti-Xa and aPTT groups were identified from hospital billing details, with both brand and generic name as search criteria. Propensity score techniques were used to match Anti-Xa cases to aPTT controls. RBC transfusions were identified from hospital billing data. Multivariable logistic regression was used to identify significant drivers of transfusions. Results Anti-Xa patients had fewer RBC transfusions than aPTT patients in the ACS population (difference 17.5%; 95% confidence interval [CI] 16.4-18.7%), the STK population (difference 8.2%; 95% CI 4.4-11.9%), and the VTE population (difference 4.7%; 95% CI 3.3-6.1%). After controlling for patient age and gender, diagnostic risks (e.g. anemia, renal insufficiency, and trauma), and invasive procedures (e.g. cardiac catheterization, hemodialysis, and coronary artery bypass graft), Anti-Xa patients were less likely to have a transfusion while hospitalized for ACS (odds ratio [OR] 0.16, 95% CI 0.14-0.18), STK (OR 0.41, 95% CI 0.29-0.57), and VTE (OR 0.35, 95% CI 0.26-0.48). Conclusion Anti-Xa monitoring was associated with a significant reduction in RBC transfusions as compared with aPTT monitoring alone.

Early extubation and fast-track management of off-pump cardiac patients in the intensive care unit

Off-pump surgery was the original approach to treating patients with cardiac disease in the era before cardiopulmonary bypass. With the advent and refinement of cardiopulmonary bypass, the use of this technique fell out of favor and was quickly surpassed by on-pump techniques. However, the limitations of bypass surgery, especially for coronary artery bypass procedures, was still significant, leading to renewed interest in this technique. Postoperative care for off-pump coronary artery bypass (OPCAB) surgery presents both a challenge and opportunity to the intensivist. OPCAB patients can be treated in a fast-track manner allowing rapid recovery and early extubation and discharge from the intensive care unit. This is supported through the use of protocols that help standardize care and set expectations for the post-cardiac care team. Importantly, complications that may delay recovery including hypothermia, hypotension, and bleeding must be recognized early and treated aggressively to prevent unwanted complications and intensive care delays. Finally, care of these patients has shifted to the post-anesthesia recovery room, making knowledge of the care of these patients in the early postoperative period essential for cardiac anesthesiologists. This article will discuss the care of OPCAB patients following surgery and include approaches to managing patients who return both intubated and extubated.

Heparin and Protamine Titration Does Not Improve Haemostasis after Cardiac Surgery: A Prospective Randomized Study

Background

Bleeding complications are common in cardiac surgery. Perioperative handling of heparin and protamine may influence the haemostasis. We hypothesized that heparin and protamine dosing based on individual titration curves would improve haemostasis in comparison to standard dosing.

Subjects and Methods

Sixty patients scheduled for first time elective coronary artery bypass grafting or valve surgery were included in a prospective randomized study. The patients were randomized to heparin and protamine dosing with Hepcon HMS Plus device or to standard weight and activated clotting time (ACT) based dosing. Blood samples were collected before and 10 minutes, 2 hours and 4 hours after cardiopulmonary bypass. Primary endpoint was endogenous thrombin potential in plasma 2 hours after surgery as assessed by calibrated automated thrombography. Secondary endpoints included total heparin and protamine doses, whole blood clot formation (thromboelastometry) and post-operative bleeding volume and transfusions. Heparin effect was assessed by measuring anti-Xa activity.

Results

Endogenous thrombin potential and clot formation deteriorated in both groups after surgery without statistically significant intergroup difference. There were no significant differences between the groups in total heparin and protamine doses, heparin effect, or postoperative bleeding and transfusions at any time point. Significant inverse correlations between anti-Xa activity and endogenous thrombin potential were observed 10 min (r = -0.43, p = 0.001), 2 hours (r = -0.66, p<0.001) and 4 hours after surgery (r = -0.58, p<0.001).

Conclusion

In conclusion, the results suggest that perioperative heparin and protamine dosing based on individual titration curves does not improve haemostasis after cardiac surgery. Postoperative thrombin generation capacity correlates to residual heparin effect.

Trial Registration

www.isrctn.comISRCTN14201041.

Off-pump versus on-pump coronary artery bypass grafting for ischaemic heart disease

BACKGROUND

Coronary artery bypass grafting (CABG) is performed both without and with cardiopulmonary bypass, referred to as off-pump and on-pump CABG respectively. However, the preferable technique is unclear.

OBJECTIVES

To assess the benefits and harms of off-pump versus on-pump CABG in patients with ischaemic heart disease.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1, 2011), MEDLINE (OVID, 1950 to February 2011), EMBASE (OVID, 1980 to February 2011), Science Citation Index Expanded on ISI Web of Science (1970 to February 2011) and CINAHL (EBSCOhost, 1981 to February 2011) on 2 February 2011. No language restrictions were applied.

SELECTION CRITERIA

Randomised clinical trials of off-pump versus on-pump CABG irrespective of language, publication status and blinding were selected for inclusion.

DATA COLLECTION AND ANALYSIS

For statistical analysis of dichotomous data risk ratio (RR) and for continuous data mean difference (MD) with 95% confidence intervals (CI) were used. Trial sequential analysis (TSA) was used for analysis to assess the risk of random error due to sparse data and to multiple updating of accumulating data.

MAIN RESULTS

Eighty-six trials (10,716 participants) were included. Ten trials (4,950 participants) were considered to be low risk of bias. Pooled analysis of all trials showed that off-pump CABG increased all-cause mortality compared with on-pump CABG (189/5,180 (3.7%) versus 160/5144 (3.1%); RR 1.24, 95% CI 1.01 to 1.53; P =.04). In the trials at low risk of bias the effect was more pronounced (154/2,485 (6.2%) versus 113/2,465 (4.6%), RR 1.35,95% CI 1.07 to 1.70; P =.01). TSA showed that the risk of random error on the result was unlikely. Off-pump CABG resulted in fewer distal anastomoses (MD -0.28; 95% CI -0.40 to -0.16, P <.00001). No significant differences in myocardial infarction, stroke, renal insufficiency, or coronary re-intervention were observed. Off-pump CABG reduced post-operative atrial fibrillation compared with on-pump CABG, however, in trials at low risk of bias, the estimated effect was not significantly different.

AUTHORS' CONCLUSIONS

Our systematic review did not demonstrate any significant benefit of off-pump compared with on-pump CABG regarding mortality, stroke, or myocardial infarction. In contrast, we observed better long-term survival in the group of patients undergoing on-pump CABG with the use of cardiopulmonary bypass and cardioplegic arrest. Based on the current evidence, on-pump CABG should continue to be the standard surgical treatment. However, off-pump CABG may be acceptable when there are contraindications for cannulation of the aorta and cardiopulmonary bypass. Further randomised clinical trials should address the optimal treatment in such patients.

Optimal intraoperative anticoagulation strategy in patients undergoing off-pump coronary artery bypass

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was what the optimal intraoperative anticoagulation strategy should be in patients undergoing off-pump coronary artery bypass graft (CABG) surgery. A total of 157 papers were identified using the reported search, of which 8 were judged to represent the best evidence. The authors, journal, date, country of publication, study type, patient group studied, relevant outcomes and results were tabulated. The quality of clinical trials was assessed. Off-pump CABG is currently considered as a safe and effective alternative to CABG with the use of cardiopulmonary bypass, especially in the presence of off-pump expertise and certain pathologies. Although most technical steps in off-pump revascularization are standardized, it appears that there is inconsistency in intraoperative anticoagulation practice. Surveys conducted in the USA and Europe confirm the lack of uniform policy, with heparin dose ranging between 70 and 500 U/kg and from full-dose protamine to no reversal of anticoagulation. Although the quality of evidence is low, there is a trend for utilization of heparin at 150 U/kg, followed by half-dose protamine reversal, which appears to provide adequate anticoagulation for the safe conduct of anastomoses and thromboprophylaxis without significantly increasing the risk of postoperative bleeding. However, more research is necessary before firm recommendations can be made.

Heparin responsiveness during off-pump coronary artery bypass graft surgery: predictors and clinical implications

AIM

To evaluate the clinical impact of reduced heparin responsiveness (HR(reduced)) on the incidence of myocardial infarction (MI) following off-pump coronary artery bypass graft surgery (OPCAB), and to identify the predictors of HR(reduced).

METHODS

A total of 199 patients scheduled for elective OPCAB were prospectively enrolled. During anastomosis, 150 U/kg of heparin was injected to achieve an activated clotting time (ACT) of ≥ 300 s, and the heparin sensitivity index (HSI) was calculated. HSIs below 1.0 were considered reduced (HR(reduced)). The relationships between the HSI and postoperative MI, cardiac enzyme levels and preoperative risk factors of HR(reduced) were investigated.

RESULTS

There was no significant relationship between the HSI and cardiac enzyme levels after OPCAB. The incidence of MI after OPCAB was not higher in HR(reduced) patients. HR(reduced) occurred more frequently in patients with low plasma albumin concentrations and high platelet counts.

CONCLUSION

HR(reduced) was not associated with adverse ischemic outcomes during the perioperative period in OPCAB patients, which seemed to be attributable to a tight prospective protocol for obtaining a target ACT regardless of the presence of HR(reduced).

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.