Evaluation of the Werfen GEM Hemochron 100 activated clotting time (ACT) point of care device in the therapeutic monitoring of unfractionated heparin in patients undergoing cardiopulmonary bypass

Current guidelines for patient management on cardiopulmonary bypass do not contain any reference to patients with prolonged baseline aPTT. Whilst practice varies around the UK, the locally established method in the Lancashire Cardiac Centre is the use of the Medtronic Hepcon HMS+ protamine titration device to inform the heparin requirement of the patient. This device is becoming increasingly difficult to maintain and provision of cartridges required for the device is unreliable hence the requirement for a more robust method of monitoring these patients. Failure to provide an adequate method of monitoring heparin in this patient group increases the risk of circuit thrombosis during surgery which can be fatal. In patients who do not have LA, the Lancashire Cardiac Centre uses the Werfen GH100 Activated Clotting Time point of care device. Currently there is no data to support the use of this device in patients with a prolonged baseline aPTT. This study aims to establish if the device can be used successfully in this patient group.

Blood samples from patients with prolonged baseline aPTT undergoing cardiopulmonary bypass will be assessed for baseline activated clotting time, and activated clotting times and modified anti-Xa levels will be monitored throughout the surgical procedure. This will evaluate whether there is a difference in baseline activated clotting time results between the study group and the age and gender matched control group.

The main outcome of this study is to establish a patient pathway that can be used to manage the heparin required of patients with prolonged baseline aPTT whilst on bypass. This will be assessed by ascertaining if there is a relationship between the activated clotting time and the extended anti-Xa of a participant with a prolonged baseline aPTT on a high level of unfractionated heparin, whilst on cardiopulmonary bypass or simulated by spiking of whole blood samples with heparin.

As there are currently no guidelines for monitoring the anticoagulation of patients with prolonged baseline aPTT on cardiopulmonary bypass, the pathway developed in this study could be adopted by other cardiac centres, improving patient safety. The research may also be useful in other patient populations, including those with a prolonged baseline aPTT in the intensive care setting, who require extracorporeal membrane oxygenation.

Outputs

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