An observational study of heparin administration and reversal during catheter ablation for atrial fibrillation (CA-AF).

Each patient serves as their own control for the purpose of observing intravenous protamine dosage. The patients are grouped according to the type of point of care ACT measuring device, and the oral anticoagulant they are taking. Each patient will be compared only to the median value of the slope of the heparin dose-response curve, as indicated below. The data has been collected during the Course of routine anaesthesia for patients, starting in 2009. Pre heparin ACT was added to the data collected in 2011. Heparin and protamine are administered intravenously as part of standard procedure. Heparin is required because the cardiologist inserts catheters into the right and left atria, and there is a significant risk of embolism and stroke in the presence of atrial fibrillation during the procedure. Each patient undergoing CA-AF is given an intravenous dose of heparin to achieve an ACT of between 300 and 400 seconds. As each patient responds to heparin in a different manner, each patient requires the dose to be individualised. Thereafter, a heparin infusion is started between 0.2 and 0.3 times the initial heparin dose per hour, and adjusted by administration or a bolus dose of heparin or altering the infusion rate to maintain the desired ACT. Between three and four hours after the start of the procedure, when the procedure is completed, a dose of protamine is administered intravenously to reverse the heparin and achieve an ACT similar to the ACT before the initial dose of heparin. For purposes of the study, the patient is observed for the duration of anaesthesia. Information recorded for the study forms part of the normal anaesthetic record and would be recorded even if the study were not to take place. The approximate dose of protamine for reversal of heparin is 1 mG for every 1 mG (100 International Units) of heparin given to achieve the desired ACT. The initial dose of heparin and the resultant ACT enables the slope the heparin dose (mg/Kg) or heparin concentration (units/mL) to be calculated. It is hoped that by calculating the median values over a large number of observations, that a mathematical model can be derived that would allow the median slope to be used to calculate a predictable dose of heparin for each individual patient to achieve the desired ACT. Once the individual heparin dose-response curve has been developed, subsequent doses of heparin can be calculated to maintain the ACT. Additionally, the pre-protamine ACT can be used in conjunction with the slope to calculate the approximate amount of active heparin, and hence the appropriate dose of protamine to reverse that heparin.