Efficacy and safety of aprotinin in paediatric cardiac surgery: A systematic review and meta-analysis

Fibrinolytic activity in infants undergoing cardiac surgery on cardiopulmonary bypass with routine tranexamic acid: A prospective cohort substudy within the FIBrinogen CONcentrate randomised control trial

BACKGROUND

Fibrinolytic activity contributes to bleeding after cardiopulmonary bypass (CPB).

OBJECTIVE

Our objectives were, in a group of infants undergoing cardiac surgery with CPB: to document the extent of peri-operative fibrinolysis using rotational thromboelastometry (ROTEM) and standard biomarkers; to compare the agreement between these fibrinolytic measures; to assess whether fibrinolytic activity is associated with early postoperative mediastinal bleeding and assess whether supplementation with fibrinogen concentrate affected fibrinolysis.

DESIGN

Prospective cohort, mechanistic substudy, nested within the FIBrinogen CONcentrate (FIBCON) randomised controlled trial.

SETTING

Single centre, tertiary paediatric cardiac surgery and paediatric intensive care units.

PATIENTS

Ninety infants (median age 6.3 months) undergoing cardiac surgery, who all received routine intra-operative tranexamic acid. The infants were randomised to receive either an individualised dose of fibrinogen concentrate ( n  = 60) or placebo ( n  = 30) during CPB.

MAIN OUTCOME MEASURES

We measured the ROTEM variable maximum clot lysis (ML), and fibrinolytic biomarkers including plasmin-antiplasmin (PAP) and tissue plasminogen activator antigen (tPA-Ag). Blood was sampled pre-CPB, on-CPB and post-CPB, and 4 h after PICU admission.

RESULTS

tPA-Ag, PAP and ROTEM ML increased significantly after CPB despite the use of tranexamic acid. The two fibrinolytic biomarkers t-PA and PAP, correlated ( P  = 0.001) but neither correlated with ROTEM ML. Early postoperative blood loss was inversely associated with PAP levels. Each 100 μg l -1 rise in PAP was associated with a 7.9% reduction in mean blood loss. Fibrinogen concentrate supplementation as expected did not affect tPA-Ag but was temporally associated with an increase in PAP levels and a decrease in ROTEM fibrinolytic activity.

CONCLUSION

Fibrinolysis is activated after paediatric cardiac CPB surgery as indicated by increased tPA-Ag and ROTEM ML. The substantial increase in tPA-Ag post-PICU admission is probably accompanied by a similar rise of plasminogen activator inhibitor 1 (PAI-1) as part of the acute phase response to surgery, thereby limiting clinical fibrinolysis. Supplementation of fibrinogen concentrate was associated with increased PAP activity and less clinical bleeding, consistent with the known role for fibrinogen in being a substrate for plasmin.

TRIAL REGISTRATION

ISCTRN:50553029, Eudract:2013-003532-68.

Exploiting the Molecular Properties of Fibrinogen to Control Bleeding Following Vascular Injury

The plasma protein fibrinogen is critical for haemostasis and wound healing, serving as the structural foundation of the blood clot. Through a complex interaction between coagulation factors, the soluble plasma fibrinogen is converted to insoluble fibrin networks, which form the skeleton of the blood clot, an essential step to limit blood loss after vascular trauma. This review examines the molecular mechanisms by which fibrinogen modulates bleeding, focusing on its interactions with other proteins that maintain fibrin network stability and prevent premature breakdown. Moreover, we also cover the role of fibrinogen in ensuring clot stability through the physiological interaction with platelets. We address the therapeutic applications of fibrinogen across various clinical contexts, including trauma-induced coagulopathy, postpartum haemorrhage, and cardiac surgery. Importantly, a full understanding of protein function will allow the development of new therapeutics to limit blood loss following vascular trauma, which remains a key cause of mortality worldwide. While current management strategies help with blood loss following vascular injury, they are far from perfect and future research should prioritise refining fibrinogen replacement strategies and developing novel agents to stabilise the fibrin network. Exploiting fibrinogen's molecular properties holds significant potential for improving outcomes in trauma care, surgical interventions and obstetric haemorrhage.

Platelet-sparing properties of aprotinin: A scoping review on mechanisms and clinical effects

BACKGROUND

Cardiac surgery involving cardiopulmonary bypass (CPB) is associated with the risk of acquired coagulopathy, including dysregulated fibrinolysis, which can result in life-threatening bleeding complications. Aprotinin, an antifibrinolytic agent, has been recommended for the prevention of these complications. Its effectiveness has been attributed to its ability to nonspecifically inhibit various serine proteases involved in the coagulation and fibrinolysis cascade. Additionally, aprotinin may protect platelets from CPB-induced dysfunction through a platelet-sparing effect, further enhancing its efficacy.

OBJECTIVES

The biochemical pathways underlying aprotinin's platelet-sparing effect remain unclear. Furthermore, it is uncertain to what extent this effect contributes to reducing blood loss and need for transfusion.

DESIGN

A scoping review.

DATA SOURCES

MEDLINE, Embase and Cochrane were searched from inception until 21 December 2023.

ELIGIBILITY CRITERIA

Studies in which a platelet-sparing effect of aprotinin was investigated. These included systematic reviews; experimental, and observational studies describing healthy humans, patients, or animals undergoing any type of surgery; studies in which donated blood was used for in-vitro studies.

RESULTS

Sixty-four studies were deemed eligible, the majority of which observed a platelet-sparing effect, attributing it to the inhibition of platelet aggregation (via protection of glycoprotein (GP) IIb/IIIa receptors), platelet adhesion (by protection of GP Ib receptors), both aggregation and adhesion receptors, proteolysis of protease-activated receptor 1 receptors, platelet activation (by inhibition of plasmin) and platelet activation (by inhibition of thrombin). A dose-dependency of the platelet-sparing effect was investigated in both in-vitro studies and randomised controlled trials, yielding mixed results. No studies have explored the relative contribution of aprotinin's platelet-sparing effect and its antifibrinolytic effect in reducing blood loss and need for transfusion.

CONCLUSIONS

This review elucidated current knowledge on how aprotinin influences platelets and exerts its platelet-sparing effect, while highlighting gaps in the existing literature.

Use of crushed tranexamic acid tablets in water for paediatric patients with bleeding disorders

BACKGROUND

Ε-Aminocaproic acid oral solution (EACA OS) is the only commercially available antifibrinolytic for patients who cannot swallow tablets. Insurance denials and high costs remain barriers to its use.

OBJECTIVES

To determine the safety and efficacy of crushed tranexamic acid tablets in water (cTXAw) for children with bleeding disorders.

METHODS

We retrospectively reviewed records of children (<10 years) with bleeding disorders who received cTXAw or EACA OS from 1 December 2018, through 31 July 2022, at Mayo Clinic (Rochester, Minnesota). Bleeding outcomes were defined according to ISTH criteria.

RESULTS

Thirty-two patients were included (median age, 3 years; male, n = 23). Diagnoses were VWD (n = 17), haemophilia (n = 5), FVII deficiency (n = 3), inherited platelet disorder (n = 4), ITP (n = 2), and combined FV and FVII deficiencies (n = 1). Thirty-two courses of cTXAw (monotherapy 24/32; mean duration 6 days) and fifteen courses of EACA (monotherapy 12/15; mean duration 5 days) were administered. No surgical procedures (n = 28) were complicated by bleeding. Of the 19 bleeding events, 16 had effective haemostasis, two had no reported outcome, and one had no response. cTXAw and EACA were equally effective in preventing and treating bleeding (p value > .1). No patients had adverse effects. Eight of 19 patients (42%) who were initially prescribed EACA OS did not receive it because of cost or insurance denial. The estimated average wholesale price of one treatment was $94 for cTXAw and $905 for EACA OS.

CONCLUSIONS

CTXAw appears to be an effective, safe, and low-cost alternative option to EACA OS for young children with bleeding disorders.

Efficacy and utility of antifibrinolytics in pediatric spine surgery: a systematic review and network meta-analysis

Antifibrinolytics have gained increasing attention in minimizing blood loss and mitigating the risks associated with massive transfusions, including infection and coagulopathy in pediatric patients undergoing spine surgery. Nevertheless, the selection of optimal agent is still a matter of debate. We aim to review the utility of these agents and compare the efficacy of antifibrinolytics in pediatric and adolescent spine surgeries. A comprehensive search was performed in Scopus, Web of Science, and MEDLINE databases for relevant works. Studies providing quantitative data on predefined outcomes were included. Primary outcome was perioperative bleeding between the groups. Secondary outcomes included transfusion volume, rate of complications, and operation time. Twenty-eight studies were included in the meta-analysis incorporating 2553 patients. The use of Tranexamic acid (RoM: 0.71, 95%CI: [0.62-0.81], p < 0.001, I2 = 88%), Aprotinin (RoM: 0.54, 95%CI: [0.46-0.64], p < 0.001, I2 = 0%), and Epsilon-aminocaproic acid (RoM: 0.71, 95%CI: [0.62-0.81], p < 0.001, I2 = 60%) led to a 29%, 46%, and 29% reduction in perioperative blood loss, respectively. Network meta-analysis revealed higher probability of efficacy with Tranexamic acid compared to Epsilon-aminocaproic acid (P score: 0.924 vs. 0.571). The rate of complications was not statistically different between each two antifibrinolytic agent or antifibrinolytics compared to placebo or standard of care. Our network meta-analysis suggests a superior efficacy of all antifibrinolytics compared to standard of care/placebo in reducing blood loss and transfusion rate. Further adequately-powered randomized clinical trials are recommended to reach definite conclusion on comparative performance of these agents and to also provide robust objective assessments and standardized outcome data and safety profile on antifibrinolytics in pediatric and adolescent pediatric surgeries.