Optimizing Perioperative Blood and Coagulation Management During Cardiac Surgery

Gender is Independently Associated With Red Blood Cell and Platelet Transfusion in Patients Undergoing Coronary Artery Bypass Grafting: Data From the Netherlands Heart Registration

OBJECTIVES

The aim of this study was to evaluate the incidence of transfusions, including red blood cells (RBC), platelets, and fresh frozen plasma (FFP) during and after coronary artery bypass grafting (CABG) in the Netherlands. Furthermore, the authors aimed to identify the impact of sex on blood product transfusion.

DESIGN

A retrospective multicenter cohort study. Data were collected from January 2013 to December 2021 from the Netherlands Heart Registration (NHR) database.

SETTING

The NHR receives its data from 16 heart centers in the Netherlands.

PARTICIPANTS

Patients older than 18 years who underwent CABG in the Netherlands.

INTERVENTIONS

Coronary artery bypass grafting with extracorporeal circulation or off-pump coronary artery bypass grafting.

MEASUREMENTS AND MAIN RESULTS

The incidence of blood transfusion, defined as transfusions intraoperatively and during the length of the hospital admission after CABG. In addition, a differentiation was made according to the type of transfusion (packed RBC, platelets, and FFP). In the overall cohort (N = 42,388), the number of patients who received a transfusion of any type was 27.0% (n = 11,428). Women received more often RBC transfusions compared with men (45.4% v 15.6%, respectively, p < 0.001). There was a significant difference between the 2 sexes regarding platelet transfusion (women 10.0% v men 11.1%, p = 0.005) but not in FFP transfusion. Female sex was independently associated with RBC transfusion, using the multivariate logistic regression analysis.

CONCLUSIONS

The incidence of any blood transfusion was 27.0%, and was higher in women than in men. The female sex was independently associated with receiving RBC during and after CABG.

Development and validation of 'Patient Optimizer' (POP) algorithms for predicting surgical risk with machine learning

BACKGROUND

Pre-operative risk assessment can help clinicians prepare patients for surgery, reducing the risk of perioperative complications, length of hospital stay, readmission and mortality. Further, it can facilitate collaborative decision-making and operational planning.

OBJECTIVE

To develop effective pre-operative risk assessment algorithms (referred to as Patient Optimizer or POP) using Machine Learning (ML) that predict the development of post-operative complications and provide pilot data to inform the design of a larger prospective study.

METHODS

After institutional ethics approval, we developed a base model that encapsulates the standard manual approach of combining patient-risk and procedure-risk. In an automated process, additional variables were included and tested with 10-fold cross-validation, and the best performing features were selected. The models were evaluated and confidence intervals calculated using bootstrapping. Clinical expertise was used to restrict the cardinality of categorical variables (e.g. pathology results) by including the most clinically relevant values. The models were created with logistic regression (LR) and extreme gradient-boosted trees using XGBoost (Chen and Guestrin, 2016). We evaluated performance using the area under the receiver operating characteristic curve (AUROC) and the area under the precision-recall curve (AUPRC). Data was obtained from a metropolitan university teaching hospital from January 2015 to July 2020. Data collection was restricted to adult patients undergoing elective surgery.

RESULTS

A total of 11,475 adult admissions were included. The performance of XGBoost and LR was very similar across endpoints and metrics. For predicting the risk of any post-operative complication, kidney failure and length-of-stay (LOS), POP with XGBoost achieved an AUROC (95%CI) of 0.755 (0.744, 0.767), 0.869 (0.846, 0.891) and 0.841 (0.833, 0.847) respectively and AUPRC of 0.651 (0.632, 0.669), 0.336 (0.282, 0.390) and 0.741 (0.729, 0.753) respectively. For 30-day readmission and in-patient mortality, POP with XGBoost achieved an AUROC (95%CI) of 0.610 (0.587, 0.635) and 0.866 (0.777, 0.943) respectively and AUPRC of 0.116 (0.104, 0.132) and 0.031 (0.015, 0.072) respectively.

CONCLUSION

The POP algorithms effectively predicted any post-operative complication, kidney failure and LOS in the sample population. A larger study is justified to improve the algorithm to better predict complications and length of hospital stay. A larger dataset may also improve the prediction of additional specific complications, readmission and mortality.

Does heparin rebound lead to postoperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass?

BACKGROUND

Heparin rebound is a common observed phenomenon after cardiac surgery with CPB and is associated with increased postoperative blood loss. However, the administration of extra protamine may lead to increased blood loss as well. Therefore, we want to investigate the relation between heparin rebound and postoperative blood loss and the necessity to provide extra protamine to reverse heparin rebound.

METHODS

We searched PubMed, Cochrane, EMBASE, Google Scholar and Web of Science to review the question: "Does heparin rebound lead to postoperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass." Combination of search words were framed within four major categories: heparin rebound, blood loss, cardiac surgery and cardiopulmonary bypass. All studies that met our question were included. Quality assessment was performed using the Cochrane risk of bias (RoB2) tool for randomized controlled trials and the risk of bias in non-randomized studies of intervention (ROBINS-I) for non-randomised trials.

RESULTS

4 randomized and 17 non-randomized studies were included. The mean incidence of heparin rebound was 40%. The postoperative heparin levels, due to heparin rebound, were often below or equal to 0.2 IU/mL. We could not demonstrate an association between heparin rebound and postoperative blood loss or transfusion requirements. However the quality of evidence was poor due to a broad variety of definitions of heparin rebound, measured by various coagulation tests and studies with small sample sizes.

CONCLUSION

The influence of heparin rebound on postoperative bleeding seems to be negligible, but might get significant in conjunction with incomplete heparin reversal or other coagulopathies. For that reason, it might be useful to get a picture of the entire coagulation spectrum after cardiac surgery, as can be done by the use of a viscoelastic test in conjunction with an aggregometry test.

ClotPro Viscoelastometry Evaluation in Cardiac Surgery With Cardiopulmonary Bypass

OBJECTIVE

The aim of this study was to assess the reproducibility of the new viscoelastic analyzer ClotPro, and compare the parameters this system produces with the ROTEM delta system in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB).

DESIGN

A prospective and observational study.

SETTING

At a university hospital.

PARTICIPANTS

Forty adult patients undergoing cardiac surgery with CPB.

INTERVENTIONS

Correlations were calculated between ClotPro and ROTEM delta parameters.

MEASUREMENTS AND MAIN RESULTS

The ClotPro showed a high reproducibility in most of the parameters of each test; whereas ROTEM delta, although showing a low coefficient of variation in the parameters related to clot firmness, showed a high variability in the coagulation times. Excellent correlations were observed in most of the parameters of each test between ROTEM delta and ClotPro (≥0.93). However, a moderate correlation was obtained between the clotting time of the EXTEM and the EX-test (0.54). The concordance of amplitudes at different times within each test was almost 100% on both thromboelastometers. Regarding absolute differences in the test results, most of the measurements showed significant differences (p < 0.0001) between both devices.

CONCLUSIONS

ClotPro can be used as an alternative to ROTEM delta to evaluate coagulation function in cardiac surgery, but specific reference ranges need to be established first.

The effect of non-point-of-care haemostasis management protocol implementation in cardiac surgery: A systematic review

Objectives

This systematic review aims to outline the evidence on the implementation of a non‐point‐of‐care (non‐point‐of‐care [POC]) haemostasis management protocol compared to experience‐based practice in adult cardiac surgery.

Background

Management of coagulopathy in cardiac surgery is complex and remains highly variable among centres and physicians. Although various guidelines recommend the implementation of a transfusion protocol, the literature on this topic has never been systematically reviewed.

Methods

PubMed, Embase, Cochrane Library, and Web of Science were searched from January 2000 till May 2020.

Results

A total of seven studies (one randomised controlled trial [RCT], one prospective cohort study, and five retrospective studies) met the inclusion criteria. Among the six non‐randomised, controlled studies, the risk of bias was determined to be serious to critical, and the one RCT was determined to have a high risk of bias. Five studies showed a significant reduction in red blood cells, fresh frozen plasma, and/or platelet transfusion after the implementation of a structural non‐POC algorithm, ranging from 2% to 28%, 2% to 19.5%, and 7% to17%, respectively. One study found that fewer patients required transfusion of any blood component in the protocol group. Another study had reported a significantly increased transfusion rate of platelet concentrate in the haemostasis algorithm group.

Conclusion

Owing to the high heterogeneity and a substantial risk of bias of the included studies, no conclusion can be drawn on the additive value of the implementation of a cardiac‐surgery‐specific non‐POC transfusion and haemostasis management algorithm compared to experience‐based practice. To define the exact impact of a transfusion protocol on blood product transfusion, bleeding, and adverse events, well‐designed prospective clinical trials are required.

Optimal protamine dosing after cardiopulmonary bypass: The PRODOSE adaptive randomised controlled trial

BACKGROUND

The dose of protamine required following cardiopulmonary bypass (CPB) is often determined by the dose of heparin required pre-CPB, expressed as a fixed ratio. Dosing based on mathematical models of heparin clearance is postulated to improve protamine dosing precision and coagulation. We hypothesised that protamine dosing based on a 2-compartment model would improve thromboelastography (TEG) parameters and reduce the dose of protamine administered, relative to a fixed ratio.

METHODS AND FINDINGS

We undertook a 2-stage, adaptive randomised controlled trial, allocating 228 participants to receive protamine dosed according to a mathematical model of heparin clearance or a fixed ratio of 1 mg of protamine for every 100 IU of heparin required to establish anticoagulation pre-CPB. A planned, blinded interim analysis was undertaken after the recruitment of 50% of the study cohort. Following this, the randomisation ratio was adapted from 1:1 to 1:1.33 to increase recruitment to the superior arm while maintaining study power. At the conclusion of trial recruitment, we had randomised 121 patients to the intervention arm and 107 patients to the control arm. The primary endpoint was kaolin TEG r-time measured 3 minutes after protamine administration at the end of CPB. Secondary endpoints included ratio of kaolin TEG r-time pre-CPB to the same metric following protamine administration, requirement for allogeneic red cell transfusion, intercostal catheter drainage at 4 hours postoperatively, and the requirement for reoperation due to bleeding. The trial was listed on a clinical trial registry (ClinicalTrials.gov Identifier: NCT03532594). Participants were recruited between April 2018 and August 2019. Those in the intervention/model group had a shorter mean kaolin r-time (6.58 [SD 2.50] vs. 8.08 [SD 3.98] minutes; p = 0.0016) post-CPB. The post-protamine thromboelastogram of the model group was closer to pre-CPB parameters (median pre-CPB to post-protamine kaolin r-time ratio 0.96 [IQR 0.78-1.14] vs. 0.75 [IQR 0.57-0.99]; p < 0.001). We found no evidence of a difference in median mediastinal/pleural drainage at 4 hours postoperatively (140 [IQR 75-245] vs. 135 [IQR 94-222] mL; p = 0.85) or requirement (as a binary outcome) for packed red blood cell transfusion at 24 hours postoperatively (19 [15.8%] vs. 14 [13.1%] p = 0.69). Those in the model group had a lower median protamine dose (180 [IQR 160-210] vs. 280 [IQR 250-300] mg; p < 0.001). Important limitations of this study include an unblinded design and lack of generalisability to certain populations deliberately excluded from the study (specifically children, patients with a total body weight >120 kg, and patients requiring therapeutic hypothermia to <28°C).

CONCLUSIONS

Using a mathematical model to guide protamine dosing in patients following CPB improved TEG r-time and reduced the dose administered relative to a fixed ratio. No differences were detected in postoperative mediastinal/pleural drainage or red blood cell transfusion requirement in our cohort of low-risk patients.

TRIAL REGISTRATION

ClinicalTrials.gov Unique identifier NCT03532594.

Clinical impact of rotational thromboelastometry in cardiac surgery

Patients undergoing cardiac surgery are at high risk of postoperative bleeding, which is related to worse prognosis and survival. The use of ROTEM®, together with the implementation of a specific treatment algorithm, to reduce the risk of postoperative bleeding. An observational, comparative, cross-case study with historical controls. A total of 1772 consecutive patients admitted to intensive care unit after having undergone cardiac surgery, was divided into 3 groups: Group 1: Coagulation was only monitored by the classical coagulation test (control group). Group 2: Monitorization was done by ROTEM®, according to a protocol designed in our center. Group 3: VerifyNow® was added to ROTEM®, implementing a specific treatment algorithm. We observed a decreased of red blood cell transfusion (Group 1 55.5%, Group 2 52.7%, Group 3 46.6%, P<0.01). Postoperative results include a significant reduction in complications with a marked improvement in overall survival in the ROTEM® - guided groups. Conclusions: Monitoring of hemostasis by POCT'S (ROTEM® and VerifyNow®) in patients undergoing cardiac surgery and cardiac transplantation was associated with a decreased incidence of blood transfusion, postoperative clinical complications, and mortality.

Managing the coagulopathy associated with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) has allowed for significant surgical advancements, but accompanying risks can be significant and must be expertly managed. One of the foremost risks is coagulopathic bleeding. Increasing levels of bleeding in cardiac surgical patients at the time of separation from CPB are associated with poor outcomes and mortality. CPB-associated coagulopathy is typically multifactorial and rarely due to inadequate reversal of systemic heparin alone. The components of the bypass circuit induce systemic inflammation and multiple disturbances of the coagulation and fibrinolytic systems. Anticipating coagulopathy is the first step in managing it, and specific patient and procedural risk factors have been identified as predictors of excessive bleeding. Medication management pre-procedure is critical, as patients undergoing cardiac surgery are commonly on anticoagulants or antiplatelet agents. Important adjuncts to avoid transfusion include antifibrinolytics, and perfusion practices such as red cell salvage, sequestration, and retrograde autologous priming of the bypass circuit have varying degrees of evidence supporting their use. Understanding the patient's coagulation status helps target product replacement and avoid larger volume transfusion. There is increasing recognition of the role of point-of-care viscoelastic and functional platelet testing. Common pitfalls in the management of post-CPB coagulopathy include overdosing protamine for heparin reversal, imperfect laboratory measures of thrombin generation that result in normal or near-normal laboratory results in the presence of continued bleeding, and delayed recognition of surgical bleeding. While challenging, the effective management of CPB-associated coagulopathy can significantly improve patient outcomes.