Plain English Summary
Background and study aims
Vascular surgery is a type of surgery that treats diseases of the arteries and veins. During vascular surgery the drug heparin is commonly used to stop the blood from clotting (heparin anticoagulation). If too much heparin is given the patient is at risk of excess bleeding, and if too little heparin is given the patient is at risk of blood clots during the operation. It is increasingly being seen as best practice to use methods that keep blood loss to a minimum and reduce the requirement for blood transfusion. There is a debate about the best method of monitoring heparin anticoagulation. The most commonly used test to guide heparin dosing during surgery is activated clotting time (ACT), which measures how long it takes your blood to clot. However, there are concerns about variations in response between patients, and how ACT levels relate to laboratory tests of heparin activity. The aims of this study are to compare ACT levels and laboratory tests in patients undergoing major vascular surgery, record the variation in responses to heparin in these patients, and relate heparin activity to patient outcomes such as bleeding and clotting.
Who can participate?
Adult patients undergoing elective major complex vascular surgery with heparin anticoagulation and monitoring.
What does this study involve?
All patients undergoing this type of major vascular surgery are fitted with an arterial line - a thin catheter inserted into an artery from which blood is routinely sampled at intervals throughout the surgery without having to pierce the skin repeatedly. During the study the doctor takes an extra sample of blood (equivalent to half a teaspoonful) each time blood is monitored for heparin anticoagulation. This additional blood is sent to the laboratory to undergo different tests that also monitor heparin activity. Apart from the additional blood sampling during their surgery their care is exactly the same as if they were not in the study. The patients are also followed up to assess whether they have any bleeding or blood clotting, which is part of their routine care.
What are the possible benefits and risks of participating?
There is no direct benefit from taking part in the study, but the results of this study may help future patients and contribute to improved treatment during surgery. The disadvantages to taking part in the study are that the participant will have extra blood tests during surgery. There is no other change in the participant's treatment.
Where is the study run from?
Royal Free London NHS Foundation Trust (UK).
When is the study starting and how long is it expected to run for?
October 2015 to April 2017.
Who is funding the study?
Vascular Anaesthesia Society of Great Britain and Ireland (VASGBI).
Who is the main contact?
Dr Nick Schofield
Trial website
Contact information
Type
Scientific
Primary contact
Dr Nick Schofield
ORCID ID
http://orcid.org/0000-0003-3098-455X
Contact details
Royal Free London NHS Foundation Trust
Pond Street
London
NW3 2QG
United Kingdom
Additional identifiers
EudraCT number
ClinicalTrials.gov number
Protocol/serial number
NHS REC 15/LO/1750
Study information
Scientific title
Monitoring heparin anticoagulation in major vascular surgery: an observational cohort study
Acronym
Study hypothesis
Aim to correlate activated clotting time (ACT), anti-Xa levels and antithrombin levels during major vascular surgery.
Ethics approval
Research & Development Department Royal Free Hospital, 27/10/2015, REC Ref: 15/NI/0219
Study design
Observational cohort study
Primary study design
Observational
Secondary study design
Cohort study
Trial setting
Hospitals
Trial type
Diagnostic
Patient information sheet
Condition
Haematology and vascular surgery
Intervention
Enrolled patients will have additional blood tests during their surgery - withdrawal of additional 2.7 ml of blood with each monitoring episode. Up to an additional 16 ml of blood may be sampled during the course of surgery. This is equivalent to roughly 1 tablespoon and should not convey any additional risks or adverse consequences. Sampling episodes will be kept to a minimum and minimum volumes of blood withdrawn to reduce any avoidable wastage of blood. Blood will be taken from established invasive lines (arterial line), at the same time point as routine samples and therefore additional needling of the skin will not be necessary. Blood samples will be used to measure the activated clotting time (ACT), thrombin generation and anti-Xa levels.
Intervention type
Other
Phase
Drug names
Primary outcome measure
Correlate ACT and anti-Xa levels during aortic surgery - measured at baseline and up to six time points during surgery
Secondary outcome measures
1. Blood loss and bleeding will be measured during theatre
2. Clotting complications will be monitored during theatre and first week postoperatively
Overall trial start date
05/10/2015
Overall trial end date
05/04/2017
Reason abandoned (if study stopped)
Eligibility
Participant inclusion criteria
All adult patients able to give informed consent and undergoing elective major complex vascular surgery in which heparin anticoagulation and monitoring is indicated
Participant type
Patient
Age group
Adult
Gender
Both
Target number of participants
40
Participant exclusion criteria
1. <18 years old
2. Unable to consent
3. History of heparin allergy
4. Already taking part in research study
Recruitment start date
05/11/2015
Recruitment end date
05/11/2016
Locations
Countries of recruitment
United Kingdom
Trial participating centre
Royal Free London NHS Foundation Trust
Pond Street
Hampstead
London
NW3 2QG
United Kingdom
Funders
Funder type
Other
Funder name
Vascular Anaesthesia Society of Great Britain and Ireland (VASGBI) Departmental Project Grant DG01-2015
Alternative name(s)
Funding Body Type
Funding Body Subtype
Location
Results and Publications
Publication and dissemination plan
To be confirmed at later date
Intention to publish date
Participant level data
Available on request
Basic results (scientific)
Publication list