Background: Dosing subcutaneous (SC) unfractionated heparin (UFH) 3 times a day (TID) for deep venous thrombosis prophylaxis is used for patients in the United States undergoing nonorthopedic surgery. There is a lack of data on the risks of neuraxial techniques in patients receiving TID SC UFH; however, concerns have been raised about higher bleeding risks. In this prospective study, we evaluated the value of activated partial thromboplastin time (aPTT) testing at the time of removal of epidural catheters as a risk-reduction strategy for this population.
Methods: We collected data from our electronic hospital databases for all patients receiving epidural analgesia in conjunction with 5000 units TID or twice daily dosing (BID) SC UFH from December 2011 to December 2013. Our cohort received aPTT testing before removal of the catheter in all patients receiving TID SC UFH. An aPTT was ordered for patients receiving BID SC UFH only if risk factors for abnormal coagulation variables were identified. Chart reviews were performed on all patients with abnormal aPTT values to evaluate contributing risk factors.
Results: Over a 2-year period, 3523 epidurals were placed at our institution, including 714 (20.3%) for patients receiving TID SC UFH, and 1594 (45.2%) for patients receiving BID SC UFH. Of those patients receiving BID SC UFH, 186 (11.7%) had aPTT values drawn on the basis of risk factors. Ten (5.4 %, 95% CI: 2.6%-9.7%) of those patients had an aPTT value of greater than 35 seconds on the date of epidural removal. Of those patients receiving TID SC UFH, 20 (2.8%, 95% CI: 1.7%-4.3%) had an initial aPTT value of more than 35 seconds on the date of epidural removal. All patients who had abnormal aPTT values on TID heparin dosing were identified as having obvious concomitant risk factors for coagulation parameter abnormalities. There were no epidural hematomas in patients receiving either BID or TID dosing (95% CI: 0%-0.001%).
Conclusions: The routine use of aPTT testing on patients receiving TID SC UFH at the time of removal of epidural catheters as a risk-reduction strategy is not supported by our results, where only 2.8% (95% CI: 1.7%-4.3%) of these patients had abnormal aPTT values. Our study adds to the limited data currently available on the safety of epidural analgesia in patients receiving TID SC UFH. Given the rare incidence of neuraxial hematoma (95% CI: 0%-0.001%), definitive conclusions on the risks of TID SC UFH administration in patients receiving epidural analgesia cannot be drawn based on our sample size.