Blood conservation in cardiac surgery: Guidelines and controversies

Methodologic Quality and Pharmacotherapy Recommendations for Patient Blood Management Guidelines for Cardiac Surgery on Cardiopulmonary Bypass

Patient blood management (PBM) guidelines for patients undergoing cardiac surgery under cardiopulmonary bypass (CPB) have increased during the past decade, and pharmacotherapy plays an important role in PBM. In the face of the undefined consistency in the methodologic quality and pharmacotherapy recommendations across multiple guidelines, this study exclusively evaluated methodologies of the related guideline development process, and compiled medication recommendations of PBM for cardiac surgery patients. PBM guidelines for cardiac surgery under CPB were searched through some mainstream literature and guideline databases from database establishment to May 15, 2023. Nine guidelines meeting inclusion criteria were included in this study. The quality of the guidelines was evaluated using the Appraisal of Guidelines for Research and Evaluation II (AGREE II) tool. "Stakeholder involvement" received the lowest mean score of 49.38% in the AGREE II scoring among the guidelines. PBM for cardiac surgery patients spans the perioperative phase. Drug therapy strategies of PBM for cardiac surgery patients involve anemia therapy, perioperative administration of antithrombotic drugs, intraoperative anticoagulation, and the use of hemostatic drugs. Unlike for adults, there is less evidence about the management of antithrombotic drugs and hemostatic drugs for pediatric cardiac surgery patients. Recombinant activated factor VII (rFVIIa) and desmopressin (DDAVP) are not recommended after pediatric cardiac surgery, whereas prothrombin complex concentrate could be considered in clinical trials. As for the controversies regarding the administration of rFVIIa and DDAVP after adult cardiac surgery by different societies, clinicians should exercise their clinical judgment based on individual patient features.

A Narrative Review of Clinical Decision Support Systems for Perioperative Bleeding Management in Cardiac Surgery

Bleeding complications in patients undergoing cardiac surgery are common. The clinician must assimilate multiple sources of monitoring information, make rational decisions on the etiology of the bleeding, and then formulate a treatment strategy. Clinical decision support systems that acquire this information and present the data in an easily usable format may be useful tools to guide the physician in optimizing treatment strategies through adherence to evidence-based best practice guidelines. The authors present a narrative review of the literature and discuss how clinical decision support systems may be useful to the clinician.

Measurement of total hemoglobin reduces red cell transfusion in hospitalized patients undergoing cardiac surgery: a retrospective database analysis

Introduction:

Historically, perioperative hemoglobin monitoring has relied on calculated saturation, using blood gas devices that measure plasma hematocrit (Hct). Co-oximetry, which measures total hemoglobin (tHb), yields a more comprehensive assessment of hemodilution. The purpose of this study was to examine the association of tHb measurement by co-oximetry and Hct, using conductivity with red blood cell (RBC) transfusion, length of stay (LOS) and inpatient costs in patients having major cardiac surgery.

Methods:

A retrospective study was conducted on patients who underwent coronary artery bypass graft (CABG) and/or valve replacement (VR) procedures from January 2014 to June 2016, using MedAssets discharge data. The patient population was sub-divided by the measurement modality (tHb and Hct), using detailed billing records and Current Procedural Terminology coding. Cost was calculated using hospital-specific cost-to-charge ratios. Multivariable logistic regression was performed to identify significant drivers of RBC transfusion and resource utilization.

Results:

The study population included 18,169 cardiovascular surgery patients. Hct-monitored patients accounted for 66% of the population and were more likely to have dual CABG and VR procedures (10.4% vs 8.9%, p=0.0069). After controlling for patient and hospital characteristics, as well as patient comorbidities, Hct-monitored patients had significantly higher RBC transfusion risk (OR=1.26, CI 1.15-1.38, p<0.0001), longer LOS (IRR=1.08, p<0.0001) and higher costs (IRR=1.15, p<0.0001) than tHb-monitored patients. RBC transfusions were a significant driver of LOS (IRR=1.25, p<0.0001) and cost (IRR=1.22, p<0.0001).

Conclusions:

tHb monitoring during cardiovascular surgery could offer a significant reduction in RBC transfusion, length of stay and hospital cost compared to Hct monitoring.

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.

Development of a diagnostic sensor for measuring blood cell concentrations during haemoconcentration

Background:

HemoSep^® is a commercial ultrafiltration and haemoconcentration device for the concentration of residual bypass blood following surgery. This technology is capable of reducing blood loss in cardiac and other types of “clean site” procedures, including paediatric surgery. Clinical feedback suggested that the device would be enhanced by including a sensor technology capable of discerning the concentration level of the processed blood product. We sought to develop a novel sensor that can, using light absorption, give an accurate estimate of packed cell volume (PCV).

Materials and methods:

A sensor-housing unit was 3D printed and the factors influencing the sensor’s effectiveness – supply voltage, sensitivity and emitter intensity - were optimised. We developed a smart system, using comparator circuitry capable of visually informing the user when adequate PCV levels (⩾35%) are attained by HemoSep^® blood processing, which ultimately indicates that the blood is ready for autotransfusion.

Results:

Our data demonstrated that the device was capable of identifying blood concentration at and beyond the 35% PCV level. The device was found to be 100% accurate at identifying concentration levels of 35% from a starting level of 20%.

Discussion:

The sensory capability was integrated into HemoSep’s^® current device and is designed to enhance the user’s clinical experience and to optimise the benefits of HemoSep^® therapy. The present study focused on laboratory studies using bovine blood. Further studies are now planned in the clinical setting to confirm the efficacy of the device.

Endocarditis is not an Independent Predictor of Blood Transfusion in Aortic Valve Replacement Patients With Severe Aortic Regurgitation

OBJECTIVE

This study sought to evaluate if the presence of endocarditis was independently associated with increased perioperative blood transfusion in patients undergoing aortic valve replacements (AVR) with aortic regurgitation.

DESIGN

This was a retrospective study.

SETTING

Large Canadian tertiary care hospital.

PARTICIPANTS

Six hundred sixty-two consecutive patients with aortic regurgitation score of 3 or higher undergoing AVR from 1995 to 2012.

INTERVENTIONS

No interventions were performed in this retrospective study.

MEASUREMENTS AND MAIN RESULTS

After REB approval, data were obtained from a center-specific database. Univariate analysis was performed to identify variables that may be associated with transfusion of any allogeneic blood product perioperatively. A multivariate logistic regression was generated to identify independent predictors of perioperative transfusion. Unadjusted transfusion rates in patients with no endocarditis and with endocarditis were 32% and 70% (p<0.001), respectively. Independent predictors of any transfusion were moderate-to-severe preoperative anemia, preoperative renal failure, non-isolated AVR, age>70, urgent/emergent surgery, BMI<25, and female sex. Endocarditis was not an independent predictor of transfusion (OR = 0.748; 95% CI = 0.35-1.601).

CONCLUSIONS

In patients undergoing AVR, unadjusted perioperative transfusion rates were higher when endocarditis was present. However, after adjustment, aortic valve endocarditis was not independently associated with blood transfusion. The authors' observation could be explained by the higher prevalence of many independent predictors of transfusion, such as comorbidities or more complex surgery, within the endocarditis group. Thus, AV endocarditis, in the absence of other risk factors, was not associated with increased perioperative transfusion risk.