Protocol Adherence When Managing Massive Bleeding Following Complex Cardiac Surgery: A Study Design Pilot

Effects of Fibrinogen Concentrate Supplementation on Postoperative Bleeding in Infants Undergoing Complex Cardiac Surgery

The use of allogeneic blood products to restore hemostasis during pediatric cardiac surgery is associated with major risks. Consequently, there has been a growing interest in new patient blood management strategies, such as those based on the use of fibrinogen concentrate (FC). Accumulating evidence has shown FC supplementation to be safe and effective. Nevertheless, no guidelines are available on using FC in the pediatric setting, and few objective evaluations have been provided in clinical practice. The endpoint of this monocenter retrospective study was the hemostatic effect of additional FC in infants undergoing complex cardiac surgery with cardiopulmonary bypass to manage persistent clinically relevant bleeding. After weaning from cardiopulmonary bypass and after protamine administration, patients were transfused with conventional allogeneic products such as packed red blood cells, fresh frozen plasma (FFP), and platelets. In the case of redo surgery, according to the institutional protocol, patients also received tranexamic acid. In case of clinically persistent relevant bleeding, according to the anesthesiologist's judgment and thromboelastography, patients received FC supplementation (group with FC) or further FFP transfusions without receiving FC supplementation (group without FC). The primary endpoint was the hemostatic effects of FC. Secondary endpoints were the functional hypofibrinogenemia threshold value (expressed as maximum amplitude fibrinogen, MA-Fib) and postoperative MA-Fib, fibrinogenemia, intraoperative transfusions, and adverse events (AEs). In total, 139 patients who underwent cardiac surgery with CPB and aged less than 2 years were enrolled: 70 patients received allogeneic blood products and FC supplementation (group FC); 69 patients received allogeneic products without FC supplementation (group without FC). Patients that received FC supplementation were characterized by a significantly longer time of extracorporeal circulation (p < 0.001) and aortic cross-clamping (p < 0.001), a significantly lower minimum temperature (p = 0.011), increased use of concentrated prothrombin complex (p = 0.016) and tranexamic acid (p = 0.010), and a significantly higher amount of packed red blood cells, platelets (p < 0.001) and fresh frozen plasma (p = 0.03). Postoperative bleeding and severe bleeding were not statistically different between patients treated with FC and those not treated with FC supplementation (p = 0.786 and p = 0.695, respectively); after adjustment, a trend toward reduced bleeding can be observed with FC (p = 0.064). Overall, 88% of patients with severe bleeding had MA-Fib < 10 mm; a moderate association between severe bleeding and MA-Fib (odds ratio 1.7, 95% CI 0.5-6.5, p = 0.425) was found. Increased MA-Fib and postoperative fibrinogen were higher in the FC group (p = 0.003 and p < 0.001, respectively) than in FFP. AEs in the FC group were comparable to those observed in less complicated surgeries. Our results suggest a potential role of FC in complex surgery in maintaining postoperative bleeding at a level comparable to less complicated surgical procedures and favoring the increase in postoperative MA-Fib and fibrinogen.

Characterization of a canine freeze-dried platelet-derived hemostatic agent: A preclinical model for surgical and traumatic hemorrhage

INTRODUCTION

A freeze-dried, platelet-derived hemostatic agent (FPH) was developed for acute hemorrhage. The canine product (cFPH) was developed for use in preclinical models supporting human product (hFPH) investigations.

MATERIALS AND METHODS

A carotid artery bypass graft (CABG) study in dogs compared 3 dosages of cFPH to canine liquid stored platelets (cLSP) and vehicle (VEH) control groups. Histopathological analysis and blood loss assessments were completed. A separate ex-vivo synthetic graft study assessed thrombogenicity via blood from human and canine donors that was combined with species-specific FPH or apheresis platelets. Characterization of cFPH and hFPH included thrombin generation, total thrombus formation, and scanning electron microscopy.

RESULTS

Blood loss was reduced in CABG dogs receiving standard of care (cLSP) or cFPH treatment compared to VEH control; a cFPH dose effect signal was observed. Further, cFPH dosing up to 5 × 109 cells/kg was not associated with increased mortality or occlusion of the anastomosis sites, and histopathologic evidence of off-target thrombosis was not detected. When passed through a synthetic graft (ex vivo), whole blood combined with species-specific FPH did not result in thrombosis beyond that of whole blood control. In vitro testing and imaging of cFPH and FPH were comparable.

CONCLUSIONS

A single dose of cFPH or cLSP reduced blood loss in a pilot surgical study and was well tolerated with no related adverse events. Further, the hemostatic activity and characteristics of cFPH are comparable to that of hFPH, suggesting that research findings from the canine product are likely to inform the development of the human product.

Design of the Randomized Controlled Trial Comparing Dimethyl Sulfoxide Cryopreserved Platelets to Liquid Stored Platelets in Patients Undergoing Cardiopulmonary Bypass Surgery

Objective

Dimethylsulfoxide-cryopreserved platelets are being evaluated for treatment of acute hemorrhage in patients with thrombocytopenia or platelet dysfunction when liquid stored platelets are unavailable. Patients undergoing cardiac surgery with cardiopulmonary bypass with risk factors for significant bleeding represent a population for which determining efficacy and safety of cryopreserved platelets is ideal in the clinical trial setting. The primary objective is to compare blood loss in cardiopulmonary bypass patients receiving cryopreserved platelets or liquid stored platelets.

Methods

In patients undergoing cardiac surgery utilizing cardiopulmonary bypass, a standardized algorithm with transfusion triggers will be used to guide the intra- and postoperative administration of study platelets, either cryopreserved platelets or liquid stored platelets, based on the clinical presentation. The primary efficacy end point was the volume of blood loss from completion of chest closure (time 0) until the time chest tubes were removed or 24 hours after chest closure, whichever is earlier.

Results

This design article describes an ongoing multicenter, randomized, blinded trial to evaluate noninferiority or superiority of cryopreserved platelets with liquid stored platelets in controlling blood loss in patients undergoing cardiopulmonary bypass surgery.

Conclusions

Frozen storage could substantially safely extend the shelf life of stored platelets. If efficacy and safety were demonstrated in this trial, current constraints on platelet use in low resource military and civilian settings would be relieved.

A Pilot Trial of Platelets Stored Cold versus at Room Temperature for Complex Cardiothoracic Surgery

BACKGROUND

This pilot trial focused on feasibility and safety to provide preliminary data to evaluate the hemostatic potential of cold-stored platelets (2° to 6°C) compared with standard room temperature-stored platelets (20° to 24°C) in adult patients undergoing complex cardiothoracic surgery. This study aimed to assess feasibility and to provide information for future pivotal trials.

METHODS

A single center two-stage exploratory pilot study was performed on adult patients undergoing elective or semiurgent complex cardiothoracic surgery. In stage I, a two-armed randomized trial, platelets stored up to 7 days in the cold were compared with those stored at room temperature. In the subsequent single-arm stage II, cold storage time was extended to 8 to 14 days. The primary outcome was clinical effect measured by chest drain output. Secondary outcomes were platelet function measured by multiple electrode impedance aggregometry, total blood usage, immediate and long-term (28 days) adverse events, length of stay in intensive care, and mortality.

RESULTS

In stage I, the median chest drain output was 720 ml (quartiles 485 to 1,170, n = 25) in patients transfused with room temperature-stored platelets and 645 ml (quartiles 460 to 800, n = 25) in patients transfused with cold-stored platelets. No significant difference was observed. The difference in medians between the room temperature- and cold-stored up to 7 days arm was 75 ml (95% CI, -220, 425). In stage II, the median chest drain output was 690 ml (500 to 1,880, n = 15). The difference in medians between the room temperature arm and the nonconcurrent cold-stored 8 to 14 days arm was 30 ml (95% CI, -1,040, 355). Platelet aggregation in vitro increased after transfusion in both the room temperature- and cold-stored platelet study arms. Total blood usage, number of adverse events, length of stay in intensive care, and mortality were comparable among patients receiving cold-stored and room temperature-stored platelets.

CONCLUSIONS

This pilot trial supports the feasibility of platelets stored cold for up to 14 days and provides critical guidance for future pivotal trials in high-risk cardiothoracic bleeding patients.

EDITOR’S PERSPECTIVE

Controversies in the Clinical Practice of Patient Blood Management

Patient blood management (PBM) has been proposed as a standard of care in modern perioperative medicine. PBM-related interventions usually are implemented as bundles, but randomized controlled trials on the implementation of PBM as a bundle are missing. This special article focuses on the current evidence and controversies in the clinical practice of PBM and on emerging data related to specific PBM-related interventions in patients undergoing cardiac surgery. Strong evidence for many PBM-related interventions is limited because of missing studies or the poor quality of published findings and study endpoints. Restrictive blood transfusion and timely interventions to maintain hemoglobin concentration and to reduce blood loss potentially might result in improved patient outcome, although the latter has yet to be proven.

Open Versus Closed Pleura Internal Mammary Artery Harvesting and Early Pulmonary Function After Coronary Artery Bypass Grafting

BACKGROUND

The internal mammary artery is the vessel of choice for myocardial revascularisation during coronary artery bypass grafting (CABG). Although it is possible to harvest the left internal mammary artery (LIMA) without opening the left pleura, pleurotomy is usually performed to provide adequate exposure and allow the placement of the LIMA medial to the upper lobe, preventing any undue tension on the mammary pedicle. However, the intact pleura technique may have a lower risk of postoperative pulmonary complications. We aimed to study the effects of both procedures on pulmonary function and the incidence of complications.

METHOD

One hundred patients with ischaemic heart disease indicated for CABG were included and divided into two groups. The closed pleural technique group included 50 patients with preservation of the pleural integrity during mammary harvesting. The open pleural procedure group included 50 patients without preservation of pleural integrity. Spirometry was done pre- and postoperatively in both groups and postoperative pulmonary complications in both groups were recorded and analysed.

RESULTS

Internal mammary harvesting with preservation of pleural integrity during CABG in patients in the closed pleural procedure group showed significant improvement in forced expiratory volume in the first second (FEV1%), forced vital capacity (FVC%), and FEV1/FVC compared with the corresponding values in patients in the open pleural procedure group, on day 5 postoperatively, at discharge, and at day 30. There were fewer complications in preservation of pleural integrity with regard to lung atelectasis and pleural effusion, which were significantly lower in patients in the open pleural procedure group.

CONCLUSIONS

Preservation of pleural integrity has beneficial effects on pulmonary function and has fewer associated pulmonary complications.

Management of refractory bleeding post-cardiopulmonary bypass in an acute heparin-induced thrombocytopenia type II renal failure patient who underwent urgent cardiac surgery with bivalirudin (Angiox®) anticoagulation

Acute heparin-induced thrombocytopenia (HIT) patients present a myriad of anticoagulation management challenges, in clinical settings where unfractionated heparin (UFH) is the traditional drug of choice. UFH use in cardiac surgery is a known entity that has been subject to rigorous research. Research has, thus, led to its unparalleled use and the development of well-established protocols for cardiac surgery. In comparison to UFH, bivalirudin use for acute HIT patients requiring urgent cardiac surgery with cardiopulmonary bypass (CPB) is still in its infancy. We describe the tailored post-CPB management of refractory bleeding in a 65-year-old infective endocarditis, acute HIT patient with renal failure who underwent urgent aortic valve replacement and mitral valve repair with bivalirudin anticoagulation. A management approach that entailed a combination of continuous venovenous haemofiltration (CVVH), 4-Factor prothrombin complex concentrate (PCC) (Beriplex), recombinant factor VIIa (rFactor VIIa) and desmopressin (DDAVP) were consecutively used post-operatively in theatre. Based on this case study experience, two modifications to institutional protocols are recommended. The first is the use of CVVH in theatre to eliminate bivalirudin in renal failure patients or in patients where bivalirudin elimination is prolonged. Secondly, a ‘rescue therapy/intervention’ algorithm for the swift identification of refractory bleeding post-CPB is also recommended. Rescue therapy agents, such as a 4-Factor PCCs and rFactor VIIa, should be incorporated into the protocol after a robust evidence-based search and agreement with the haematologist. The aim of these recommendations is to reduce the risk of bleeding associated with bivalirudin use for inexperienced institutions and experienced institutions alike, until larger randomized, controlled studies provide more in-depth knowledge to expand our clinical practice.

Performance of functional fibrinogen thromboelastography in children undergoing congenital heart surgery

BACKGROUND

Functional Fibrinogen assay of the Thromboelastography (FFTEG), a whole blood viscoelastic hemostatic assay, has been used to estimate fibrinogen levels in adult patients undergoing major surgery but its performance in pediatric patients undergoing cardiac surgery requires evaluation. In this study, we evaluate the correlation between FFTEG parameters and standard laboratory tests for fibrinogen and platelet counts before and after cardiopulmonary bypass in children undergoing repair for congenital heart disease.

METHODS

In this prospective observational study, whole blood samples were obtained from children less than 5 years of age undergoing congenital heart surgery with cardiopulmonary bypass before surgical incision and immediately after administration of protamine. Blood samples were analyzed for Thromboelastography, Functional Fibrinogen level measured by FFTEG (FLEV), complete blood counts with platelet count and plasma fibrinogen assay (LFib, Clauss). The primary outcome of this study was to assess the correlation between FFTEG parameters, LFib and platelet counts in neonates, infants, and small children less than 5 years old. Additionally, we studied if postbypass FFTEG parameters could predict critical thresholds of hypofibrinogenemia LFib ≤200 mg·dl^-1 .

RESULTS

One hundred and five children (22 neonates, 51 infants, and 32 small children) were included in the final analysis. FLEV estimated higher fibrinogen levels than LFib in all patients. Before bypass, FLEV was on average 133 mg·dl^-1 higher than LFib (95% confidence interval, CI, 116-150, P < 0.001) for all the patients; after bypass, FLEV was 48 mg·dl^-1 (95% CI: 37-59, P < 0.001) higher than LFib for all the patients. Linear correlation coefficients between FLEV and LFib in all patients were R = 0.41 (95% CI: 0.24-0.56, P < 0.001) before bypass and increased to R = 0.63 (95% CI: 0.51-0.74, P < 0.001) after bypass. Bland Altman analysis performed on postbypass values of FLEV and LFib showed a positive bias of FLEV in estimation of LFib. The magnitude and the variability of the bias for all the patients group was decreased with lower mean of the difference of FLEV and LFib when the average values of FLEV and LFib were <200 mg·dl^-1 . Low linear correlations were noticed between maximal amplitude of platelet contribution to FFTEG and platelet counts both before and after bypass. For predicting the clinical thresholds of postbypass hypofibrinogenemia at plasma fibrinogen levels ≤200 mg·dl^-1 , FLEV and maximal amplitude of the fibrinogen clot generated area under receiver operative curves at 0.90 (95% CI = 0.76-1.0) in neonates, 0.6 (95% CI- 0.42-0.78) in infants, and 0.97 (95% CI = 0.91-1.0) in small children. Based on the receiver operative curves, values of postbypass hypofibrinogenemia with LFib ≤200 g·dl^-1 corresponded to cutoffs of FLEV_POST ≤245 mg·dl^-1 and maximal amplitude of the fibrinogen clot ≤13.4 mm.

CONCLUSION

In pediatric patients undergoing cardiac surgery, FLEV derived from Functional Fibrinogen correlated linearly with plasma fibrinogen levels (Clauss) both before and after CPB. FLEV estimation of plasma fibrinogen was improved after CPB in neonates, infants, and small children. After CPB, FFTEG can be used to predict laboratory diagnosis of critical hypofibrinogenemia (≤200 mg·dl^-1 ) during pediatric cardiac surgery. Further studies are required to assess the impact of predictability of FFTEG on component transfusion during pediatric cardiac surgery.

The Case for a Conservative Approach to Blood Transfusion Management in Cardiac Surgery

Limiting blood transfusion in cardiac operations is a well-meaning goal of perioperative care. Potential benefits include decreasing morbidity and limiting procedural costs. It is difficult to identify transfusion as the cause of adverse outcomes. The need for transfusion may identify a sicker patient population at greater risk for a worse outcome that may or may not be related to the transfusion. We reviewed the indications for and adverse effects of blood transfusion in patients undergoing cardiac procedures to provide a balanced approach to management of blood resources in this population. We reviewed current literature, including systematic reviews and practice guidelines, to synthesize a practice management plan in patients having cardiac operations. Several prospective randomized studies and large population cohort studies compared a postoperative restrictive transfusion policy to a more liberal policy and found very little difference in outcomes but decreased costs with a restrictive policy. Evidence-based practice guidelines and implementation standards provide robust intervention plans that can limit harmful effects of transfusion and provide safe and effective procedure outcomes. A restrictive transfusion policy seems to be safe and effective but does not necessarily provide better outcome in most patient cohorts. The implications of these findings suggest that many discretionary transfusions could be avoided. A subset of high-risk patients could undoubtedly benefit from a more liberal transfusion policy, but the definition of high risk is ill defined.