Inflammatory response and platelet activation after off-pump coronary artery bypass surgery

Haemotherapy with Fibrinogen for Perioperative Bleeding Prevention-A View on Arterial Thrombogenesis and Myocardial Infarction in the Rat In Vivo

Major blood loss during cardiac surgery is associated with increased morbidity and mortality. Clinical pilot studies indicated that preoperative fibrinogen supplementation reduces postoperative blood loss without increasing thrombotic complications. However, an increase in fibrinogen concentration might rather aggravate pre-existing thrombosis than increase the incidence of thrombotic events. Therefore, we investigated, in the present study, whether fibrinogen supplementation influences (1) arterial thrombus formation, (2) the extent of myocardial infarction and (3) the cardioprotective effect of ischaemic preconditioning. Arterial thrombogenesis of the femoral artery was induced by topic FeCl₃ treatment in anaesthetised Wistar rats after pretreatment with 60 mg/kg (Fib_low), 120 mg/kg (Fib_high) or vehicle (Con). Vessel blood flow was monitored, and time to vessel occlusion was analysed as a marker for arterial thrombogenesis. In addition, regional myocardial I/R injury was induced by temporary left coronary artery occlusion in rats pretreated with or without fibrinogen supplementation. In additional groups, ischaemic preconditioning (IPC) was induced by 3 cycles of 5 min of ischaemia/reperfusion. In all groups, myocardial infarct size was determined by triphenyltetrazoliumchlorid staining. Arterial thrombogenesis was not affected by fibrinogen pretreatment. No differences in time until vessel occlusion between Con, Fib_low and Fib_high groups were observed. In addition, fibrinogen supplementation in low and high concentrations had no effect on infarct size after regional myocardial ischaemia and reperfusion (Fib_low: 66 ± 10%, Fib_high: 62 ± 9%; each ns vs. Con). IPC reduced infarct size from 62 ± 14% to 34 ± 12% (p < 0.05 vs. Con). Furthermore, both fibrinogen concentrations did not affect cardioprotection by ischaemic preconditioning (Fib_low + IPC: 34 ± 11%, Fib_high + IPC: 31 ± 13%; each ns vs. IPC). Haemotherapy with fibrinogen did not affect arterial thrombogenesis, myocardial infarction and the cardioprotective effect of ischaemic preconditioning.

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.

Can plasma fibrinogen levels predict bleeding after coronary artery bypass grafting?

BACKGROUND

Fibrinogen is the main biomarker for bleeding. To prevent excessive postoperative bleeding, it would be useful to identify high-risk patients before coronary artery bypass grafting (CABG).

OBJECTIVES

In order to predicating bleeding after CABG, we sought to determine whether preoperative fibrinogen concentration was associated with the amount of bleeding following CABG.

PATIENTS AND METHODS

A total of 144 patients (mean age = 61.50 ± 9.42 years; 65.7% men), undergoing elective and isolated CABG, were included in this case-series study. The same anesthesia technique and medicines were selected for all the patients. In the ICU, the patients were assessed in terms of bleeding at 12 and 24 hours post-operation, amount of contingent blood products received, and relevant tests. Statistical tests were subsequently conducted to analyze the correlation between preoperative fibrinogen concentration and the amount of post-CABG bleeding.

RESULTS

The mean ± standard deviation of bleeding at 12 and 24 hours post-operation was 285.37 ± 280.27 and 499.31 ± 355.57 mL, respectively. The results showed that postoperative bleeding was associated with different factors whereas pre-anesthesia fibrinogen was not correlated with bleeding at 12 (P = 0.856) and 24 hours (P = 0.936) post-operation. There were correlations between the extra-corporal circulation time and bleeding at 12 hours post-operation (ρ = 0.231, P = 0.007) and bleeding at 24 hours post-operation (ρ = 0.218, P = 0.013).

CONCLUSIONS

Preoperative assessment of plasma fibrinogen levels failed to predict post-CABG bleeding.

Restoring hemostasis: fibrinogen concentrate versus cryoprecipitate

Fibrinogen plays a key role in the coagulation process, and therefore maintaining adequate quantities of fibrinogen is an essential step in achieving satisfactory hemostasis in patients with acquired hypofibrinogenemia. Potential options for treating acquired hypofibrinogenemia in patients with uncontrolled bleeding include the use of cryoprecipitate or fibrinogen replacement therapy. This review provides a brief overview of the hemostatic process and the methods for assessing coagulopathy and discusses the efficacy and safety of cryoprecipitate and fibrinogen concentrate in restoring fibrinogen levels, achieving hemostasis and reducing transfusion requirements in different patient populations requiring rapid hemostasis. Other issues relevant to the clinical use of these agents in restoring hemostasis, including variations in product composition, preparation time and cost, are also examined.

A randomized, double blind trial of prophylactic fibrinogen to reduce bleeding in cardiac surgery

BACKGROUND AND OBJECTIVES

Postoperative bleeding has a great clinical importance and can contribute to increased mortality and morbidity in patients undergoing coronary artery bypass graft surgery. In this prospective, randomized, double-blind study, we evaluated the effect of prophylactic administration of fibrinogen concentrate on post-coronary artery bypass graft surgery bleeding.

METHODS

A total of 60 patients undergoing coronary artery bypass surgery were randomly divided into two groups. Patients in the fibrinogen group received 1g of fibrinogen concentrate 30 min prior to the operation, while patients in the control group received placebo. Post-operative bleeding volumes, prothrombin time, partial thromboplastin time, INR, hemoglobin and transfused blood products in both groups were recorded. A strict red blood cell transfusion protocol was used in all patients.

RESULTS

There were no significant differences between intra-operative packed red blood cells infusion in the studied groups (1.0±1.4 in fibrinogen group, and 1.3±1.1 in control group). Less postoperative bleeding was observed in the fibrinogen group (477±143 versus 703±179, p=0.0001). Fifteen patients in the fibrinogen group and 21 in the control group required post-op packed red blood cells infusion (p=0.094). No thrombotic event was observed through 72 h after surgery.

CONCLUSION

Prophylactic fibrinogen reduces post-operative bleeding in patients undergoing coronary artery bypass graft.

Prophylactic Fibrinogen Infusion in Cardiac Surgery Patients: Effects on Biomarkers of Coagulation, Fibrinolysis, and Platelet Function

Objective: We have recently reported that prophylactic fibrinogen infusion reduces bleeding after coronary artery bypass grafting (CABG) surgery. Because fibrinogen for the first time was administered to patients without hereditary fibrinogen deficiency or ongoing bleeding, a detailed analysis of the effects of fibrinogen concentrate on biomarkers of coagulation, fibrinolysis, and platelet function was performed. Methods: Twenty CABG patients with preoperative plasma fibrinogen levels <3.8 g/L were included in a prospective study. Patients were randomized to preoperative infusion of 2 g fibrinogen concentrate (fibrinogen group) or no infusion (control group). Activated partial thromboplastin time (aPTT), prothrombin time, activated clotting time, and plasma concentrations of fibrinogen, antithrombin, thrombin-antithrombin complex, prothrombin fragment 1.2, and D-dimer, thromboelastometry, platelet count, and platelet aggregometry were analyzed before and 15 minutes after infusion, and 2 and 24 hours after surgery. Results: Fifteen minutes after infusion of fibrinogen concentrate, fibrinogen plasma levels increased by 0.6 ± 0.2 g/L (P < .001 between groups), and induced minimal changes in aPTT and plasma levels of antithrombin, while remaining variables remained unchanged. After surgery, fibrinogen levels no longer differed between groups. D-dimer was significantly higher after surgery in the fibrinogen group (P = .03), while none of the other markers were statistically different between groups. Conclusions: Infusion of 2 g fibrinogen to cardiac surgery patients, without hereditary or acquired fibrinogen deficiency or ongoing bleeding, results in no or minimal changes in biomarkers reflecting coagulation and platelet function. An increased release of fibrin degradation products was detected after surgery in fibrinogen-treated patients.

[Bedside thrombelastography. Cost reduction in cardiac surgery]

BACKGROUND

Demographic changes and aggressive medication with platelet aggregation inhibitors have resulted in a marked increase in blood and coagulation product expenditure and costs in cardiac surgery. We analyzed the bedside coagulation test (ROTEM) in order to verify clot forming quality and to find a cost-effective treatment algorithm.

PATIENTS AND METHODS

Annual treatment costs of all cardiosurgical patients were retrospectively analyzed before (729 patients) and after (693 patients) implementation of the bedside ROTEM test. Cumulative numbers and costs of platelet concentrates (PltC), fresh frozen plasma (FFP), red blood cell units (RBC), and the coagulation factors prothrombin complex concentrates (PCC), recombinant factor VIIa (rFVIIa), factor XIII (FXIII), and fibrinogen were assessed. Average monthly numbers and costs were compared. The number of rethoracotomies and early mortality were assessed and compared in both periods.

RESULTS

After ROTEM implementation cumulative RBC expenditure showed a 25% decrease and PltC a 50% decrease. FFP expenditure remained unchanged. PCC, FXIII were markedly reduced (-80%) while rFVIIa was entirely omitted. Fibrinogen, however, showed a two-fold increase. Cumulative average monthly costs of all blood products decreased from 66,000 EUR to 45,000 EUR (-32%). Coagulation factor average monthly costs decreased from 60,000 EUR to 30,000 EUR (-50%) yielding combined savings of 44%. In contrast, average monthly costs for ROTEM were 1,580 EUR. The total number of rethoracotomies decreased from 6.6% to 5.5% while early mortality (5.9%; 6.0%) remained stable.

CONCLUSIONS

Cumulative costs for treatment of perioperative coagulation disorders were reduced by bedside ROTEM analysis to achieve a selective substitution management. Saved costs for blood and coagulation products clearly outweighed the expenses of ROTEM. Adequate differential coagulation management can therefore be cost-effective.

Inflammatory response and cardioprotection during open-heart surgery: the importance of anaesthetics

Open-heart surgery triggers an inflammatory response that is largely the result of surgical trauma, cardiopulmonary bypass, and organ reperfusion injury (e.g. heart). The heart sustains injury triggered by ischaemia and reperfusion and also as a result of the effects of systemic inflammatory mediators. In addition, the heart itself is a source of inflammatory mediators and reactive oxygen species that are likely to contribute to the impairment of cardiac pump function. Formulating strategies to protect the heart during open heart surgery by attenuating reperfusion injury and systemic inflammatory response is essential to reduce morbidity. Although many anaesthetic drugs have cardioprotective actions, the diversity of the proposed mechanisms for protection (e.g. attenuating Ca(2+) overload, anti-inflammatory and antioxidant effects, pre- and post-conditioning-like protection) may have contributed to the slow adoption of anaesthetics as cardioprotective agents during open heart surgery. Clinical trials have suggested at least some cardioprotective effects of volatile anaesthetics. Whether these benefits are relevant in terms of morbidity and mortality is unclear and needs further investigation. This review describes the main mediators of myocardial injury during open heart surgery, explores available evidence of anaesthetics induced cardioprotection and addresses the efforts made to translate bench work into clinical practice.

Preoperative Fibrinogen Levels as a Predictor of Postoperative Bleeding after Open Heart Surgery

BACKGROUND

Open heart surgery still involving major bleeding continues to be a major challenge after cardiac surgery and is also a significant cause of morbidity and mortality. Most hemostatic factors are intercorrelated with postoperative bleeding, and fibrinogen seems the most fundamental hemostatic risk factor for open heart surgery.

METHODS

The study included 97 patients who underwent elective coronary artery surgery (78 men and 19 women; mean age, 60.9 +/- 10.3). Preoperative blood samples were obtained and preoprative quantitative determination of plasma fibrinogen levels were measured by the clotting method of Clauss using the fibrinogen kit. Patients were operated on by the same team and the same technique. The total amount of drainage blood from chest tubes was recorded after termination of operation.

RESULTS

There were statistical significance between the fibrinogen levels and the drainage (r = -0.897, P < .001). Chest drainage was a mean of 972 mL (range, 240-2445 mL) in the first 48 hours after sternotomy closure. Fibrinogen level and relation to age was statistically significant (P = .015). There was no statistical significance between fibrinogen levels and gender (male gender = 400.7 +/- 123.0 versus female gender = 395.6 +/- 148.1; P = .877) and between drainage and gender (male gender = 968.2 +/- 538.5 versus female gender = 990.0 +/- 554.7; P = .876). Two patients (2%) died early after the surgery. There were no significant differences between the postoperative bleeding and cardiopulmonary bypass time (P = .648) or cross-clamp time (P = .974).

CONCLUSION

The results of this study suggested that low preoperative fibrinogen level appears to be a useful diagnostic marker to assess the activity of the coagulation system, and that its preoperative level may serve as a potential risk factor for postoperative bleeding after coronary artery bypass surgery.

Is There Still a Role for Aprotinin in Cardiac Surgery?

Cardiac surgery is associated with a systemic inflammatory response and systemic coagulopathy, which can result in significant organ dysfunction and bleeding. Aprotinin, a serine protease inhibitor, can limit systemic inflammation, and has been associated with myocardial, pulmonary and cerebral protection in addition to its proven haemostatic efficacy. Data are currently conflicting regarding the haemostatic efficacy of aprotinin relative to alternative agents including tranexamic acid. Recent studies have demonstrated aprotinin usage is associated with increased rates of thrombotic and renal complications, but these findings are at odds with the majority of studies relating to aprotinin safety to date. The lack of adequately powered, randomised studies evaluating aprotinin and alternative agents limits drawing conclusions about the complete use or disuse of aprotinin presently and requires individualised patient selection based on bleeding risk and co-morbidities for its usage.