Method:
A retrospective cohort study was conducted including seven hundred and
two patients who underwent elective or urgent CABG in our unit between
April 2014 and January 2017. Those who underwent emergent CABG were
excluded from the study due to their intricate higher bleeding risk from
other factors.
All patients included within the study were managed using our unit’s
standard operating protocols. Preoperatively aspirin was held 5 days
pre-operatively except in those with high-risk coronary anatomy
(significant left main-stem (LMS) disease or LMS equivalent).
Clopidogrel was held for 5 days and ticagrelor for 3. With regards to
other anticoagulants warfarin was held for 5 days with a preoperative
INR check performed 1 day prior to surgery. Direct oral anticoagulants
were held for 3 days and low molecular weight heparin was held the night
before surgery. For those patients requiring a preoperative heparin
infusion this was held a minimum of 6 hours pre-operatively.
Intraoperatively a baseline activated clotting time (ACT) was taken
prior to heparin administration. 300 mg/kg (measured body weight) of
heparin was administered in all patients. Cardiopulmonary bypass was
established with a minimum ACT of 480 seconds, between aortic and
dual-stage right atrial cannula used for commencing cardiopulmonary
bypass. After weaning from cardiopulmonary bypass protamine was
administered via a standardised protocol based on the previous ACT
measurement with a final ACT taken after administration to ensure return
to baseline.
Postoperatively all patients were transferred to our intensive care
unit. Colloid and packed red cells were infused as per protocol with a
transfusion threshold of haemoglobin under 80 grams/litre used.
Mediastinal and pleural drainage were monitored hourly and any deviation
from standard prompted the running of thromboelastogram (TEG) testing
and targeted fresh-frozen plasma, platelet and cryoprecipitate
transfusion. In those not receiving a protamine infusion an extra bolus
of protamine (25-50mg) was given in those with significant pre- and
post-heparinase values.
Mixed practice exists between surgeons within our unit with some
preferring the routine use of a postoperative protamine infusion in
intensive care and some not. Our postoperative protamine infusion has
been standardised for those who did receive it, consisting of 100mg
protamine mixed in 100ml 0.9% saline given over 4 hours intravenously.
This was started on arrival in the intensive care unit.
Demographics along with outcome data were collected from our CVIS
database. Outcome measures assessed were; post-operative mediastinal and
pleural drainage for the first 24 hours (this was indexed against body
weight), post-operative transfusion of blood products including packed
red blood cells, fresh frozen plasma and platelets, postoperative
hospital stay, and re-exploration for bleeding, tamponade or other
cardiac complication rate. Patients with high body mass index (BMI)
defined as BMI ≥ 30 kg/m² are subdivided into two groups depending of
having post-operative Protamine. Blood loss and blood products
transfusion were analysed to study the effect of Protamine infusion in
this group of patients.
Results were statistically analysed using the chi-squared test for
categorical data and the 2-sample t-test for continuous data.
P<0.05 was considered statistically significant.