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Efficacy and safety of fibrinogen concentrate in surgical patients: a meta-analysis of randomized controlled trials
Fominskiy E, Nepomniashchikh VA, Lomivorotov VV, Monaco F, Vitiello C, Zangrillo A, Landoni G
Journal of Cardiothoracic and Vascular Anesthesia. 2016;30((5):):1196-204.
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Abstract
OBJECTIVES To investigate the efficacy and safety of fibrinogen concentrate (FC) in surgical patients. DESIGN Meta-analysis of randomized controlled studies (RCTs). SETTING Perioperative. PARTICIPANTS Adult and pediatric surgical patients. INTERVENTIONS A search of PubMed/Medline, Embase, Cochrane Central Register of Controlled Trials, Transfusion Evidence Library, Google Scholar, and the proceedings from major international anesthesiology meetings up to February 1, 2016 for RCTs that compared FC with placebo or other comparators. MEASUREMENTS AND MAIN RESULTS The primary outcome was all-cause mortality. Pooled risk ratios and mean differences (MDs) were computed with either fixed-effects or random-effects models. The study included 14 RCTs comprising 1,035 patients; the majority of patients underwent cardiac surgery. All-cause mortality was lower in the fibrinogen group (4/432 [0.9%] v 15/430 [3.5%]; risk ratio 0.26; 95% confidence interval [CI] 0.09-0.78; p = 0.02; heterogeneity statistic (l2) = 0%). The use of FC was associated with reduced bleeding (MD -127 mL; 95% CI -207 to -47; p = 0.002; I2= 54%) and a lower number of red blood cells units transfused versus comparator (MD -0.9; 95% CI -1.3 to -0.5; p<0.001; I2 = 42%). There were no differences in the rates of thrombotic events and myocardial infarction. CONCLUSIONS In surgical patients, FC was associated with reduced bleeding and a lower number of red blood cell units transfused, and it also might reduce mortality. However, none of the analyzed trials was powered for estimation of survival and adverse events with FC use. Half of the included studies were of high or moderate risk of bias. The evidence primarily came from cardiac surgery settings.
Clinical Commentary
Dr. MJR Desborough, Haematology/Transfusion Medicine, NHS Blood and Transplant, Oxford, UK.
What is known?
Bleeding is an important and potentially preventable adverse event associated with surgery. Prevention, or treatment, of bleeding must be balanced against the risk of arterial or venous thrombotic events. Fibrin, which is formed from fibrinogen, is a key part of blood clot formation. In situations where a patient’s fibrinogen concentration is low, fibrinogen concentrate (or another source of fibrinogen such as cryoprecipitate) is often administered. However it is less clear whether fibrinogen concentrate is effective and safe for patients with a normal baseline fibrinogen level.
An alternate, or adjuvant approach, is the use of anti-fibrinolytic agents (which prevent fibrin from being broken down) such as tranexamic acid and epsilon aminocaproic acid. These drugs are increasingly used to prevent peri-operative blood loss and do not appear to be associated with significant adverse events.
A systematic review and meta-analysis published in 2013 on fibrinogen concentrate in surgical patients found no difference in mortality but found a significant reduction in the incidence of red cell transfusion (Wikkelsø et al. Cochrane Database Syst Rev 2013;8:CD008864).
What did this paper set out to examine?
The authors set out to compare efficacy and safety of fibrinogen concentrate in surgical patients in a systematic review and meta-analysis. Randomised controlled trials including adult or paediatric surgery were included. Trials were included if they compared fibrinogen concentrate to placebo or another haemostatic therapy (fresh frozen plasma, platelets, cryoprecipitate or coagulation factor concentrates). The only exclusion was congenital (inherited) fibrinogen deficiency.
The primary outcome was all-cause mortality. Secondary outcomes were blood loss; proportion of patients who received a red cell transfusion; number of red cell units used; surgical revisions for bleeding; and thrombotic complications.
What did they show?
The authors identified 14 randomised controlled trials with 1035 patients. The majority of trials were in the setting of cardiac surgery. There was a high level of variation in the comparators that were used, the trigger for infusion of fibrinogen concentrate; prophylactic or therapeutic use; the timing of administration; and the dose of fibrinogen concentrate. The authors reported that half of the included studies were at high or moderate risk of bias.
The risk of all-cause mortality was significantly lower in the group treated with fibrinogen concentrate. The event rate for mortality was very low with the majority of trials having no deaths in either arm. The meta-analysis included an unpublished paper and exclusion of this paper form the meta-analysis resulted in a non-significant difference in mortality (Mengoli et al. J Cardiothorac Vasc Anesth 2017;31:e33-5).
Blood loss; number of red cell units transfused; and proportion of patients who received a red cell transfusion were significantly lower for those treated with fibrinogen concentrate. No difference was found in the risk of surgical revisions for bleeding or thrombotic complications.
What are the implications for practice and for future work?
This meta-analysis suggests that fibrinogen concentrate may reduce peri-operative mortality, bleeding and transfusion requirements. However the considerable variation in triggers, comparators and settings suggests that further randomised controlled trial data will be necessary to demonstrate efficacy in this setting. It is unclear whether anti-fibrinolytic drugs such as tranexamic acid or epsilon aminocaproic acid were used in the trials included in this meta-analysis. Now that these agents have been widely adopted into clinical guidelines, the efficacy and risk profile of fibrinogen concentrate may differ and this should be taken into account in future randomised controlled trials.
References
Fibrinogen/*therapeutic use Humans Perioperative Care/*methods Randomized Controlled Trials as Topic *Surgical Procedures, Operative Treatment Outcome efficacy fibrinogen hemorrhage safety surgery
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Pre-emptive treatment with fibrinogen concentrate for postpartum haemorrhage: randomized controlled trial
Wikkelso AJ, Edwards HM, Afshari A, Stensballe J, Langhoff-Roos J, Albrechtsen C, Ekelund K, Hanke G, Secher EL, Sharif HF, et al
British Journal of Anaesthesia. 2015;114((4):):623-33.
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BACKGROUND In early postpartum haemorrhage (PPH), a low concentration of fibrinogen is associated with excessive subsequent bleeding and blood transfusion. We hypothesized that pre-emptive treatment with fibrinogen concentrate reduces the need for red blood cell (RBC) transfusion in patients with PPH. METHODS In this investigator-initiated, multicentre, double-blinded, parallel randomized controlled trial, we assigned subjects with severe PPH to a single dose of fibrinogen concentrate or placebo (saline). A dose of 2 g or equivalent was given to all subjects independent of body weight and the fibrinogen concentration at inclusion. The primary outcome was RBC transfusion up to 6 weeks postpartum. Secondary outcomes were total blood loss, total amount of blood transfused, occurrence of rebleeding, haemoglobin <58 g litre(-1), RBC transfusion within 4 h, 24 h, and 7 days, and as a composite outcome of 'severe PPH', defined as a decrease in haemoglobin of >40 g litre(-1), transfusion of at least 4 units of RBCs, haemostatic intervention (angiographic embolization, surgical arterial ligation, or hysterectomy), or maternal death. RESULTS Of the 249 randomized subjects, 123 of 124 in the fibrinogen group and 121 of 125 in the placebo group were included in the intention-to-treat analysis. At inclusion the subjects had severe PPH, with a mean blood loss of 1459 (sd 476) ml and a mean fibrinogen concentration of 4.5 (sd 1.2) g litre(-1). The intervention group received a mean dose of 26 mg kg(-1) fibrinogen concentrate, thereby significantly increasing fibrinogen concentration compared with placebo by 0.40 g litre(-1) (95% confidence interval, 0.15-0.65; P=0.002). Postpartum blood transfusion occurred in 25 (20%) of the fibrinogen group and 26 (22%) of the placebo group (relative risk, 0.95; 95% confidence interval, 0.58-1.54; P=0.88). We found no difference in any predefined secondary outcomes, per-protocol analyses, or adjusted analyses. No thromboembolic events were detected. CONCLUSIONS We found no evidence for the use of 2 g fibrinogen concentrate as pre-emptive treatment for severe PPH in patients with normofibrinogenaemia. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov: http://clinicaltrials.gov/show/NCT01359878. Published protocol: http://www.trialsjournal.com/content/pdf/1745-6215-13-110.pdf.Copyri ght The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Clinical Commentary
Dr Akshay Shah, Adult Intensive Care Unit, John Radcliffe Hospital, Oxford
What is known?
Post-partum haemorrhage (PPH) is a leading cause of maternal morbidity and mortality worldwide. Fibrinogen is an essential component of haemostasis and fibrinogen levels of <2 g.L-1, in patients with PPH, have been shown to predict further severe bleeding and requirement for blood and blood products. Current guidelines recommend using fibrinogen concentrate to correct acquired hypofibrinogenaemia although high quality evidence for this is lacking. A recent Cochrane review demonstrated weak evidence for fibrinogen concentrate in reducing transfusion requirements in bleeding patients undergoing elective cardiac surgery.
What did this paper set out to examine?
This was a multicentre randomised placebo-controlled study aimed to assess the efficacy of pre-emptive treatment with fibrinogen concentrate early in PPH without any laboratory evidence of hypofibrinogenaemia. This is different to previous studies that have examined the use of fibrinogen concentrate once coagulopathy and a fibrinogen deficit have been established. Patients aged >18 years with a PPH, defined as bleeding from the uterus and/or birth canal with 24 hours of delivery were randomised to receive a fixed dose of 2g of fibrinogen concentrate or placebo (isotonic saline). The primary outcome was red blood cell (RBC) transfusion during a 6-week follow-up period postpartum.
What did they show?
Data from 244 patients were available for final analysis; 123 in the fibrinogen group and 121 in the placebo group. There was no difference in the primary outcome RBC transfusion was given to 25 patient (20.3%) in the fibrinogen group and 26 patients (21.5%) in the placebo group. There was also no difference in clinically important secondary outcomes such as estimated blood loss, adverse effects and progression to severe PPH between both groups. An important limitation of this study is that patients who may stand to benefit the most from fibrinogen therapy were either under-represented or not included only 2.2% of patients had a critical fibrinogen level of <2 g.L-1 and 46 patients 15% of the bleeding population in this study, could not be randomised because they were bleeding too heavily and therefore informed consent could not be obtained. Furthermore, the difference in fibrinogen concentrate between the treated and placebo group was only 0.4 g.L-1 which suggests that a larger dose may be required.
What are the implications for practice and for future work?
This study highlights the lack of benefit of fibrinogen concentrate in patients with early PPH and a normal fibrinogen level, which may help, limits it use. Future research should be directed towards developing fast and accurate tests for measuring fibrinogen levels and developing 'goal-directed’ therapy towards patients who may benefit the most such as those with severe PPH and/or acquired hypofibrinogenaemia.
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Hemostatic effects of fibrinogen concentrate compared with cryoprecipitate in children after cardiac surgery: A randomized pilot trial
Galas FR, de Almeida JP, Fukushima JT, Vincent JL, Osawa EA, Zeferino S, Camara L, Guimaraes VA, Jatene MB, Hajjar LA
Journal of Thoracic & Cardiovascular Surgery. 2014;148((4):):1647-55.
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OBJECTIVES Acute acquired hypofibrinogenemia in children undergoing cardiac surgery is a major concern because it often results in perioperative bleeding and high rates of allogeneic blood transfusion. Fibrinogen concentrate has been proposed as an alternative to cryoprecipitate (the gold standard therapy), with minimal infectious and immunologic risks. Our objective was to investigate the efficacy and safety of fibrinogen concentrate in children undergoing cardiac surgery. METHODS In this randomized pilot study, patients were allocated to receive fibrinogen concentrate (60 mg/kg) or cryoprecipitate (10 mL/kg) if bleeding was associated with fibrinogen levels <1 g/dL after cardiopulmonary bypass weaning. The primary outcome was postoperative blood losses during the 48 hours after surgery. RESULTS A total of 63 patients were included in the study, 30 in the fibrinogen concentrate group and 33 in the cryoprecipitate group. The median 48-hour blood loss was not significantly different between the 2 groups (320 mL [interquartile range, 157-750] vs 410 mL [interquartile range, 215-510], respectively; P = .672). After treatment, plasma fibrinogen concentration increased similarly following administration of both products. There were no differences in allogeneic blood transfusion after intervention treatment. CONCLUSIONS A large trial comparing fibrinogen concentrate and cryoprecipitate in the management of children with acute acquired hypofibrinogenemia during heart surgery is feasible. The preliminary results of our study showed that the use of fibrinogen concentrate was as efficient and safe as cryoprecipitate in the management of bleeding children undergoing cardiac surgery. Copyright 2014 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.
Clinical Commentary
Dr Simon Stanworth - NHS Blood & Transplant, Oxford, UK
What is known?
There are several different sources of fibrinogen for use in patients with major bleeding such as trauma or postpartum or surgery. The two main concentrated sources are fibrinogen concentrate or cryoprecipitate. Cryoprecipitate is the standard method of fibrinogen supplementation in UK. The evidence relating to the clinical effectiveness of cryoprecipitate is very limited; with very few randomised controlled trials (RCTs) completed to date. Fibrinogen concentrate (FgC) is increasingly available and a recent Cochrane review evaluating the effectiveness of FgC for patients with bleeding found limited data (six small trials, none in trauma) but reported no effect on overall mortality but did find a reduction in allogeneic transfusion.
What did this paper set out to examine?
Pilot trials are needed to inform the design of larger definitive trials which can answer fundamental questions about effectiveness of fibrinogen supplementation in patients with major bleeding. This study describes a pilot study of fibrinogen concentrate or cryoprecipitate to reduce bleeding in children undergoing cardiac surgery. Patients younger than 7 years and admitted for elective cardiac surgery and cardio-pulmonary bypass were screened and eligible for randomisation to receive fibrinogen concentrate (60mg/kg) or cryoprecipitate (10ml/kg) if they developed diffuse bleeding at wound surfaces and a fibrinogen concentration < 1g/L/.
What did they show?
A total of 63 patients were included in the pilot, 30 received fibrinogen concentrate and 33 cryoprecipitate. There were no differences in post-operative blood losses (primary outcome), and the median 48 hour blood loss was not significantly different between the two groups. Rises in plasma fibrinogen concentration were similar between the two groups, and there were no significant differences between the groups for adverse events and a range of other clinical outcomes.
What are the implications for practice and for future work?
In addition to documenting feasibility of recruitment, the pilot study supports the need for larger trials, not just to understand how different sources of fibrinogen should be used, but also to evaluate comparative differences between products. Cryoprecipitate is a pooled blood component) that has a variable, but high Fg concentration (15-20 g/L), but also contains other plasma proteins (FVIII, FXIII, von Willebrand’s factor and fibronectin) which may confer additional haemostatic benefits.
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Fibrinogen concentrate for bleeding - a systematic review
Lunde J, Stensballe J, Wikkelso A, Johansen M, Afshari A
Acta Anaesthesiologica Scandinavica. 2014;58((9):):1061-74.
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Fibrinogen concentrate as part of treatment protocols increasingly draws attention. Fibrinogen substitution in cases of hypofibrinogenaemia has the potential to reduce bleeding, transfusion requirement and subsequently reduce morbidity and mortality. A systematic search for randomised controlled trials (RCTs) and non-randomised studies investigating fibrinogen concentrate in bleeding patients was conducted up to November 2013. We included 30 studies of 3480 identified (7 RCTs and 23 non-randomised). Seven RCTs included a total of 268 patients (165 adults and 103 paediatric), and all were determined to be of high risk of bias and none reported a significant effect on mortality. Two RCTs found a significant reduction in bleeding and five RCTs found a significant reduction in transfusion requirements. The 23 non-randomised studies included a total of 2825 patients, but only 11 of 23 studies included a control group. Three out of 11 found a reduction in transfusion requirements while mortality was reduced in two and bleeding in one. In the available RCTs, which all have substantial shortcomings, we found a significant reduction in bleeding and transfusions requirements. However, data on mortality were lacking. Weak evidence from RCTs supports the use of fibrinogen concentrate in bleeding patients, primarily in elective cardiac surgery, but a general use of fibrinogen across all settings is only supported by non-randomised studies with serious methodological shortcomings. It seems pre-mature to conclude whether fibrinogen concentrate has a routine role in the management of bleeding and coagulopathic patients. More RCTs are urgently warranted. 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
Clinical Commentary
What is known?
Fibrinogen is a coagulation protein that is vital for the formation of a stable clot. Fibrinogen levels have been reported to be one of the first to fall during major haemorrhage, often before many of the other haemostatic factors. Knowing this, it has been hypothesised that fibrinogen replacement (i.e. fibrinogen concentrate, cryoprecipitate or FFP) may be beneficial as a treatment for major haemorrhage. Proposed benefits include: reversal/attenuation of the acquired coagulopathy which commonly accompanies major haemorrhage (of which hypofibrinogenaemia is a significant part), reduction of blood loss, reduction in the overall need for allogeneic transfusion and possibly reduction in mortality. For these reasons the treatment of major bleeding using fibrinogen replacement has become a focus for research, particularly in the settings of trauma, surgery and obstetrics.
What did this paper set out to examine?
This systematic review set out to evaluate the published evidence around the use of fibrinogen concentrate (FgC) for the treatment of bleeding, with the specific aims of examining whether FgC was efficacious (as defined by: reduction in blood loss or reduction in transfusion need) and if there were any clear benefits (e.g. mortality reduction) or harmful effects (e.g. thromboembolic disease). The authors reviewed RCTs, as well as large non-randomised prospective and retrospective studies. Studies were limited to humans and included all studies that used FgC for treatment of bleeding. Exclusions included: inherited fibrinogen disorders and case reports.
What did they show?
This paper included 7 RCTs and 23 observational studies. 12 on-going RCTs were identified. Many of the observational studies did not have a control arm (n = 12). Four clinical settings were evaluated: surgery (cardiac surgery and non-cardiac surgery), trauma and obstetrics. The FgC dose ranged from 2-8g across the studies. All 7 RCTs were in the elective surgery setting (5 cardiac). All had a high risk of bias and all were small (63 or fewer participants) and 1 was in abstract form only. Overall these studies showed no mortality benefit of FgC, however 6 out of the 7 reported either a significant reduction in transfusion use or a significant reduction in blood loss. Meta-analysis quantified the reduction of allogeneic transfusion into a relative risk of: 0.53 (0.32, 0.89) in participants given FgC. ICU stay was also significantly shorter in FgC treated participants (by 10.9 h (-21.38, -0.38)). (It should be noted that there was marked study heterogeneity (I2 = 79%)). 6 of the 7 studies were partly or fully funded by industry partners. No RCT reported thromboembolic event data. Of the 23 observational studies, 3 found a reduction in transfusion use (1 surgery study, 2 trauma studies); 2 found a reduction in mortality (both retrospective trauma studies) and 1 found a significant reduction in bleeding (surgery study). Only one retrospective study reported thromboembolic data (obstetric) and found no increase in thrombotic events. The paper described the effect of FgC on blood fibrinogen levels and similar results were seen in both RCT and observational study settings. On average 1 g FgC infused to RCT participants raised the blood level by 0.24 g/L and in the observational setting raised the blood level by 0.28 g/L. The authors commented that there was marked heterogeneity between studies, in many areas, including: (1) whether FgC was administered alone or with other pro-haemostatic agents (i.e. PCC, FFP); (2) how decisions were made to give the FgC in some studies viscoelastic testing was used to guide FgC doses and in others set doses were administered; (3) the timing of FgC administration pre or post operatively; (4) the use of different controls ranging from none to placebo controlled. This limited the pooling of data and the ability to make firm conclusions. The authors did conclude that even though there continues to be increasing use of FgC in clinical settings of major haemorrhage, the evidence to support this practice is weak.
What are the implications for practice and for future work?
This systematic review highlights the limited evidence that is available to support the use of FgC in the treatment of bleeding. The RCT data showed that FgC reduced bleeding and transfusion need in one setting only - elective surgery i.e. within a controlled clinical environment. It is unclear how applicable these data are for other clinical settings, such as trauma, where up to 30% of patients with haemorrhage have an accompanying coagulopathy and where fibrinolysis is an important part of the bleeding phenotype. FgC or fibrinogen replacement needs to be evaluated in each clinical setting, since although no study has directly compared the coagulation profiles of different patient groups with major bleeding, it is probable that different groups will have differing needs. For example, normally mothers at full term have a fibrinogen level of between 4-7 g/L, a level that would be deemed abnormally high in non-pregnant populations. Future work needs to address the differences between patients in order to move towards a more individualised treatment approach. Study heterogeneity limited the ability of the authors to pool data. Consensus about how best to collect outcomes and report data in major bleeding trials would go a long way towards reducing this variation.