Algorithm-based management of bleeding in patients with extracorporeal membrane oxygenation

Venovenous Extracorporeal Membrane Oxygenation to Facilitate Removal of Endobronchial Tumors

Short-term extracorporeal membrane oxygenation is a useful adjunct to thoracic procedures. We report the cases of 2 middle-aged men who were supported with venovenous extracorporeal membrane oxygenation to facilitate tumor debulking and recanalization of the carina and mainstem bronchi. Neither patient had major complications or adverse events. These cases suggest that short-term extracorporeal membrane oxygenation is safe in patients undergoing complex resection or debulking of endobronchial lesions.

Coagulopathy Characterized by Rotational Thromboelastometry in a Porcine Pediatric ECMO Model

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is used to support patients with reversible cardiopulmonary insufficiency. Although it is a lifesaving technology, bleeding, inflammation, and thrombosis are well-described complications of ECMO. Adult porcine models of ECMO have been used to recapitulate the physiology and hemostatic consequences of ECMO cannulation in adults. However, these models lack the unique physiology and persistence of fetal forms of coagulation factors and fibrinogen as in human infants. We aimed to describe physiologic and coagulation parameters of piglets cannulated and supported with VA-ECMO. Four healthy piglets (5.7-6.4 kg) were cannulated via jugular vein and carotid artery by cutdown and supported for a maximum of 20 hours. Heparin was used with a goal activated clotting time of 180-220 seconds. Arterial blood gas (ABG) was performed hourly, and blood was transfused from an adult donor to maintain hematocrit (Hct) > 24%. Rotational thromboelastometry (ROTEM) was performed at seven time points. All animals achieved adequate flow with a patent circuit throughout the run (pre- and post-oxygenator pressure gradient <10 mmHg). There was slow but significant hemorrhage at cannulation, arterial line, and bladder catheter sites. All animals required the maximum blood transfusion volume available. All animals became anemic after exhaustion of blood for transfusion. ABG showed progressively declining Hct and adequate oxygenation. ROTEM demonstrated decreasing fibrin-only ROTEM (FIBTEM) clot firmness. Histology was overall unremarkable. Pediatric swine are an important model for the study of pediatric ECMO. We have demonstrated the feasibility of such a model while providing descriptions of physiologic, hematologic, and coagulation parameters throughout. Weak whole-blood clot firmness by ROTEM suggested defects in fibrinogen, and there was a clinical bleeding tendency in all animals studied. This model serves as an important means to study the complex derangements in hemostasis during ECMO.

Intracranial hemorrhage on extracorporeal membrane oxygenation: an international survey

INTRODUCTION

Intracranial hemorrhage is one of the most dreaded complications associated with extracorporeal membrane oxygenation. However, robust data to guide clinical practice are lacking. We aimed to describe the current perceptions and practices surrounding the risk, prevention, diagnosis, management, and prognosis of intracranial hemorrhage in patients on extracorporeal membrane oxygenation.

METHODS

We conducted an international, cross-sectional survey of adult extracorporeal membrane oxygenation centers using a self-administered electronic questionnaire sent to medical directors and program coordinators of all 290 adult centers member of the Extracorporeal Life Support Organization.

RESULTS

There were 143 respondents (49%). The median proportion of patients having neuroimaging performed was only 1-25% in venovenous-extracorporeal membrane oxygenation patients and 26-50% in venoarterial-extracorporeal membrane oxygenation and extracorporeal cardiopulmonary resuscitation. The majority of participants (58%) tolerated a PaO₂ < 60 mm Hg on venovenous-extracorporeal membrane oxygenation. Lower PaO₂ targets were inversely correlated with the reported incidence of intracranial hemorrhage (r =-0.247; p = 0.024). In patients with intracranial hemorrhage, most participants reported stopping anticoagulation, and median targets for blood product administration were 70,000-99,000 platelets/µL, 1.5-1.9 of international normalized ratio, and 1.6-2.0 g/L of fibrinogen.

CONCLUSION

We found significant heterogeneity in the perceptions and practices. This underlines the need for more research to appropriately guide patient management. Importantly, neuroimaging was performed only in a minority of patients. Considering the important management implications reported by most centers when intracranial hemorrhage is diagnosed, perhaps clinicians should consider widening their indications for early neuroimaging.

Intracranial hemorrhage in adults on ECMO

RATIONALE

Extracorporeal membrane oxygenation (ECMO) use has exploded over the last decade. However, it remains invasive and associated with significant complications, including tamponade, infection, thrombosis, gas embolism and bleeding. The most dreaded complication is intracranial hemorrhage (ICH). In this article, we review the literature on the incidence, diagnosis, risk factors, pathophysiology, prognosis, prevention and management of ICH in adults on ECMO.

MAIN FINDINGS

We found a high incidence of ICH in the literature with a poor prognosis. Important risk factors included pre-ECMO cardiac arrest, sepsis, influenza, renal failure, renal replacement therapy, hemolysis and thrombocytopenia. The optimal anticoagulation strategy is still uncertain. As platelet dysfunction and depletion appear to play an important role in the pathogenesis of ICH in patients on ECMO, a liberal platelet transfusion strategy may be advised. Prompt computed tomography (CT) diagnosis is of great importance as interventions to limit hematoma expansion and secondary neurological injury are most effective if instituted early. Transporting patients to the radiology department can be performed safely while on ECMO. A strategy combining screening CT on admission with a heparin-free period of extracorporeal support was demonstrated to be safe in VV-ECMO patients and resulted in a better prognosis compared to similar cohorts in the literature.

CONCLUSION

Despite major technological improvements and all the experience gained in adults, ECMO remains associated with a high incidence of ICH. There are still wide gaps in our understanding of the disease. Optimal management strategies that minimize the risk of ICH and improve prognosis need to be further studied.

Evidence of altered haemostasis in an ovine model of venovenous extracorporeal membrane oxygenation support

Background

Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used in the management of cardiopulmonary failure that is refractory to conventional medical and surgical therapies. The major problems clinicians face are bleeding and clotting, which can occur simultaneously. To discern the impact of pulmonary injury and ECMO on the host’s haemostatic response, we developed an ovine model of smoke-induced acute lung injury (S-ALI) and ECMO. The aims of this study were to determine if the ECMO circuit itself altered haemostasis and if this was augmented in a host with pulmonary injury.

Methods

Twenty-seven South African meat merino/Border Leicester Cross ewes underwent instrumentation. Animals received either sham injury (n = 12) or S-ALI (n = 15). Control animal groups consisted of healthy controls (ventilation only for 24 h) (n = 4), ECMO controls (ECMO only for 24 h) (n = 8) and S-ALI controls (S-ALI but no ECMO for 24 h) (n = 7). The test group comprised S-ALI sheep placed on ECMO (S-ALI + ECMO for 24 h) (n = 8). Serial blood samples were taken for rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests. Animals were continuously monitored for haemodynamic, fluid and electrolyte balances and temperature. Pressure-controlled intermittent mandatory ventilation was used, and mean arterial pressure was augmented by protocolised use of pressors, inotropes and balanced fluid resuscitation to maintain mean arterial pressure >65 mmHg.

Results

Rotational thromboelastometry, platelet aggregometry and routine coagulation laboratory tests demonstrated that S-ALI and ECMO independently induced changes to platelet function, delayed clot formation and reduced clot firmness. This effect was augmented with the combination of S-ALI and ECMO, with evidence of increased collagen-induced platelet aggregation as well as changes in factor VIII (FVIII), factor XII and fibrinogen levels.

Conclusions

The introduction of an ECMO circuit itself increases collagen-induced platelet aggregation, decreases FVIII and von Willebrand factor, and induces a transient decrease in fibrinogen levels and function in the first 24 h. These changes to haemostasis are amplified when a host with a pre-existing pulmonary injury is placed on ECMO. Because patients are often on ECMO for extended periods, longer-duration studies are required to characterise ECMO-induced haemostatic changes over the long term. The utility of point-of-care tests for guiding haemostatic management during ECMO also warrants further exploration.

Effect of two doses of tranexamic acid on fibrinolysis evaluated by thromboelastography during cardiac surgery: a randomised, controlled study

BACKGROUND

Tranexamic acid is used to decrease bleeding and transfusions during cardiac surgery. However, dosing based on pharmacokinetic data to optimally inhibit fibrinolysis is unknown. With increasing concerns regarding seizures associated with higher doses, lower dosing schemes may be important.

OBJECTIVE

To determine the effect of two dosing schemes compared with placebo on fibrinolysis and clinical outcomes.

DESIGN

A double-blind, randomised, controlled, pilot trial.

SETTING

Single tertiary centre.

PATIENTS

Cardiac surgery patients requiring cardiopulmonary bypass.

INTERVENTION

Patients were randomised to receive a 30 mg  kg(-1) bolus and continuous infusion of 16  mg  kg (-1) h(-1) (Group HIGH), a 5 mg  kg(-1) bolus followed by 5 mg  kg(-1)  h(-1) (Group LOW) or Sodium chloride (Placebo).

MAIN OUTCOME MEASURE

Fibrinolysis was evaluated by thromboelastography and D-dimers. Secondary endpoints were blood loss, transfusion requirement and side effects.

RESULTS

Thirty-three patients were included. Significant fibrinolysis was defined by LY30 more than 7.5% based on thromboelastography and was not observed after cardiopulmonary bypass in any groups. After protamine administration, LY30 differences between groups were 0.7 [95% confidence interval (95% CI) -0.04 to 1.4] between Groups HIGH and Placebo, -0.08 (95% CI -0.82 to 0.66) between Groups HIGH and LOW, and 0.78 (95% CI 0.02 to 1.5) between Groups LOW and Placebo. A significant increase in D-dimers was observed in the Group Placebo compared with the two treatment groups. There were no differences in bleeding or transfusion requirement.

CONCLUSION

In this dose-finding study, there were no differences in fibrinolysis or clinical outcomes among the two tranexamic acid schemes and placebo. Any difference in fibrinolytic inhibition requires a larger adequately powered study.

TRIAL REGISTRATION

EudraCT number: 2010-024104-99.