Do we need ongoing monitoring of the intensity of anticoagulation with heparin for chronic hemodialysis?: a quality initiative of the Division of Nephrology Eastern Health

Shamseddin, Mohammad Khaled (2013) Do we need ongoing monitoring of the intensity of anticoagulation with heparin for chronic hemodialysis?: a quality initiative of the Division of Nephrology Eastern Health. Masters thesis, Memorial University of Newfoundland.

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Abstract

Background: Heparin is the standard anticoagulation used to prevent clotting in the extracorporeal circuit during hemodialysis. Its anticoagulation effect can be measured by the activated clotting time (ACT), to achieve 1.5- 2 times the baseline value to prevent clotting or bleeding during hemodialysis. However, it is unknown whether changing ACT monitoring policy in chronic hemodialysis patients, from routine monthly ACT monitoring to ACT measurement in response to clinical events, will increase the risk of clotting and bleeding events. -- Methods: To evaluate, in chronic hemodialysis patients on a stable heparin dose, whether a change in practice, from routine monthly ACT monitoring (Phase I) to one in which ACTs are only measured for initial dose assignment or in response to clinical indications (Phase II), will significantly increase the incidence of patients' bleeding or clotting events, 109 patients in our hemodialysis unit were followed and evaluated for 8 months in a quality initiative study using a before-and-after design. Clotting event was defined as visible signs of clot formation in the bottom of the dialyzer, coagulated dialyzer, or changing the circuit due to clotting. Overt bleeding documented by clinical examination or diagnostic investigations within 4 hours from hemodialysis session, doubling homeostasis time in patients with A VF; not secondary to fistula-related issues, unexplained fall in hemoglobin 2: 20 g/L within a month, or the requirement for blood transfusion due to bleeding were defined as a bleeding event. -- Results: The mean ACT in phase I was higher than phase II (P =0.003), but >50% of ACTs were below target. Although heparin doses were changed more often (Incident rate ratio (IRR) 9.11; 95% CI: 2.78-29.92, P =0.000), and more effectively achieving ACT target during phase I compared with phase II (IRR 189.5; 95% Cl: 25.36-1415.2, P=0.000), the incident rate ratio for all clotting events occurred during phase I was unexpectedly and significantly higher (IRR 1.4; 95% CI: 1.01-1 .97, P =0.041) than phase II. For unclear reasons, the risk of any clotting event occurring during phase I was higher than phase II (Odd Ratio; OR 1.87; 95% CI: 1.03-3.39, P =0.04). This could not be explained merely by the low frequency and effectiveness of heparin dose changes, which occurred in less than 10% of clotting events, and were effective achieving ACT target in only 50% of above cases. Although heparin doses were changed more often when serious clotting (type 2 or 3) occurred during phase I compared with phase II, heparin change was not statistically significant (OR 3.12; 95% CI: 0.62-15 .8, P =0.17), nor was it effective in achieving ACT target (OR 2; 95% Cl: 0.08-51 .6, P =0.68). -- Bleeding events occurred 6% less often during phase I compared with phase II. However, this was not statistically significant (P =0.84), although the risk for any bleeding event stayed the same during both phases (OR 1; 95% CI: o.53-1.9, P =1). -- Conclusions: Routine monthly ACT monitoring in adult chronic hemodialysis patients did not improve clinical outcomes reducing clotting and bleeding events compared with measuring ACTs only for the initial dose assignment or in response to clinical indications. However, as practiced locally, this could be due to the limited physician response to ACTs that were not at target. -- To more thoroughly address the question of whether routine ACT monitoring is necessary, the best approach in a future randomized trial would include strictly standardized heparin dose-adjustment protocols to be used routinely by hemodialysis nurses to reduce the potential for bias due to physician response variability.

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