Inadvertent postdialysis anticoagulation due to heparin line locks.

Large-bore dual lumen in-dwelling venous catheters are used in hemodialysis. These catheters are usually locked with heparin after the treatment. This study addressed the underappreciated postdialysis coagulopathy that can result. Thirty-six patients were included: 7 dialyzed through arterio-venous fistulae, 29 through in-dwelling venous catheters. The latter group was further subdivided according to whether they received heparin or heparin-free dialysis. To assess the heparin lock, a full-dose heparin lock as well as a much weaker heparin lock and a citrate lock were used. To assess the coagulopathy, blood was taken 1 hr after dialysis. The activated partial thromboplastin time (APTT) and anti-Xa level was measured. Additionally, 6 venous catheters were removed and the amount of fluid expelled upon locking with saline was measured. Clotting from the patient group with arterio-venous fistulae was normal following dialysis. The patients with in-dwelling venous catheters and heparin locks had significantly deranged clotting; 6 out of 10 patients had abnormal APTT results. All patients with catheters, heparin-free dialysis, and heparin locks had deranged clotting (7 out of 7). The rate decreased significantly when heparinized saline was used as a lock. A subset of patients had a citrate lock rather than a heparin lock; the clotting results normalized in all but one patient. An in vitro study demonstrated immediate leakage of fluid from the end of the ports upon locking. Significant postdialysis anticoagulation can occur after dialysis, which can be attributed to the heparin line locks. This risk is considerably reduced when a citrate lock is used instead.