Low Preoperative Fibrinogen Plasma Concentration Is Associated With Excessive Bleeding After Cardiac Operations

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.

Comparison of functional fibrinogen (FF/CFF) and FIBTEM in surgical patients – a retrospective study

Fibrinogen-based clot firmness is reported as the maximum amplitude (MA) when using the citrated functional fibrinogen (CFF) assay in thrombelastography (TEG), and as the maximum clot firmness (MCF) together with several clot amplitude parameters when using the FIBTEM assay in thromboelastometry (ROTEM). Concern is currently being raised that these two tests have different platelet inhibiting performance and consequently provide different values. This is relevant for the clinical setting of fibrinogen replacement. We aim herein to compare the parameters of these two fibrinogen-based clot quality tests and their correlation with the plasma fibrinogen level as determined by the Clauss method.

In total 261 whole blood samples taken from 163 clinical routine surgical patients were analyzed with TEG 5000 and ROTEM tests, and correlation with Clauss fibrinogen level was assessed.

: Using TEG, the overall fibrin-based clot firmness measured in the CFF assay was significantly higher than the MCF measured by FIBTEM assay. Both assays showed significantly positive correlations with the fibrinogen levels measured using the Clauss method. However, individual values of Clauss fibrinogen concentration corresponded with different values for the two viscoelastometric tests; e.g. within the range of 1.9–2.1 g/L Clauss fibrinogen the median of CFF MA was 16.3 mm whereas FIBTEM MCF was 12.0 mm.

: We showed herein by measurements of citrated whole blood samples from surgical patients that CFF MA values were different from FIBTEM MCF values measured in the same sample. Awareness that these whole blood assays provide different clot amplitude results is mandatory, particularly if they are being considered as tools for guiding fibrinogen supplementation. Thromboembolic side effects caused by a potentially too high fibrinogen substitution must also kept in mind in this context.

Prediction of Post-Weaning Fibrinogen Status during Cardiopulmonary Bypass: An Observational Study in 110 Patients

Background

After cardiac surgery with cardiopulmonary bypass (CPB), acquired coagulopathy often leads to post-CPB bleeding. Though multifactorial in origin, this coagulopathy is often aggravated by deficient fibrinogen levels.

Objective

To assess whether laboratory and thrombelastometric testing on CPB can predict plasma fibrinogen immediately after CPB weaning.

Patients / Methods

This prospective study in 110 patients undergoing major cardiovascular surgery at risk of post-CPB bleeding compares fibrinogen level (Clauss method) and function (fibrin-specific thrombelastometry) in order to study the predictability of their course early after termination of CPB. Linear regression analysis and receiver operating characteristics were used to determine correlations and predictive accuracy.

Results

Quantitative estimation of post-CPB Clauss fibrinogen from on-CPB fibrinogen was feasible with small bias (+0.19 g/l), but with poor precision and a percentage of error >30%. A clinically useful alternative approach was developed by using on-CPB A10 to predict a Clauss fibrinogen range of interest instead of a discrete level. An on-CPB A10 ≤10 mm identified patients with a post-CPB Clauss fibrinogen of ≤1.5 g/l with a sensitivity of 0.99 and a positive predictive value of 0.60; it also identified those without a post-CPB Clauss fibrinogen <2.0 g/l with a specificity of 0.83.

Conclusions

When measured on CPB prior to weaning, a FIBTEM A10 ≤10 mm is an early alert for post-CPB fibrinogen levels below or within the substitution range (1.5–2.0 g/l) recommended in case of post-CPB coagulopathic bleeding. This helps to minimize the delay to data-based hemostatic management after weaning from CPB.

Pre-operative fibrinogen supplementation in cardiac surgery patients: an evaluation of different trigger values

BACKGROUND

Pre-operative fibrinogen levels are negatively associated with postoperative bleeding in cardiac surgery patients. The guidelines of the European Society of Anaesthesiology consider the possibility of a prophylactic pre-operative supplementation in patients with fibrinogen levels<`3.8 g/l. The present study is a reanalysis of published data aimed to define the diagnostic accuracy of different values of pre-operative fibrinogen levels in predicting severe post-operative bleeding.

METHODS

Data were retrieved for 2154 patients in four different studies. Severe bleeding (SB) was defined as a post-operative chest drain output>1 l/12 h. Diagnostic accuracy for prediction of SB was tested at three cutoff values of pre-operative fibrinogen (2.5 g/l, 3.0 g/l, and 3.8 g/l).

RESULTS

At all the three cutoff values, pre-operative fibrinogen levels had an excellent negative predictive value, ranging from 86% to 100%. Conversely, the positive predictive value was poor at all the cutoff levels: 12% (3.8 g/l), 14% (3.0 g/l), and 19% (2.5 g/l). Overall, the accuracy of pre-operative fibrinogen levels for the prediction of SB was poor. A strategy based on pre-operative fibrinogen supplementation would lead to inappropriate treatment in > 80% of the treated patients. Overall, a trigger value of 3.8 g/l would result in an inappropriate treatment in 52% of the patients, of 3.0 g/l in 20% of the patients, and of 2.5 g/l in 4% of the patients.

CONCLUSION

Correction of pre-operative fibrinogen levels below 3.8 g/l would lead to an excessive rate of inappropriate interventions. Values below 2.5 g/l could be considered.