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Activated Partial Thromboplastin Time Elevation After Low-Dose Unfractionated Heparin in Critically Ill Patients FREE TO VIEW

Ramin Pirouz, MD; Peter Smith, MD; Yevgeniy Vaynkof, MD; Shashmi Balakrishna, MBBS; Raja Chand, MBBS; Sundeep Atluri, MBBS; Louis Gerolemou, DO; Michael Elias, MD; Sadaf Mir, MD; Taiyo Nishimoto, MD; Phani Surapaneni, MBBS; Elpidio Jimenez, MD; Patricia O’Neill, MD
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SUNY-Downstate @ LICH, Brooklyn, NY

Chest. 2013;144(4_MeetingAbstracts):368A. doi:10.1378/chest.1703552
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SESSION TITLE: Critical Care Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM

PURPOSE: Significant elevation of activated partial thromboplastin time (APTT) and hemorrhagic complications are not expected when low-dose unfractionated heparin (LDUH) is used for thromboprophylaxis. APTT monitoring is not advised. Our anecdotal experience and several reports in the literature suggest that in some patients LDUH may significantly raise APTT and may be associated with unexpected bleeding.

METHODS: APTTs were recorded for all ICU patients from 7/12 - 2/13 whether they received LDUH or not. 7 APTT values including pre-LDUH were recorded for each patient. Covariables assessed included sex, age, liver disease, serum creatinine, BMI and prothrombin time (PT). Statistical methods were the Kruskal-Wallis test, Exact Mantel-Haenszel chi-square test of linear association and multiple linear regression.

RESULTS: Amongst 219 patients, 79 received no LDUH (LDUH-0), 38 received LDUH 5000 units Q12h (LDUH-12), and 91 received Q8h (LDUH-8). Maximal APTT (M-APTT) and maximal increase APTT (MI-APTT) were greater in both LDUH-12 and LDUH-8 compared to LDUH-0 (p=0.002 for M-APTT, p=0.001 for MI-APTT) but did not differ significantly from each other. M-APTT analyzed by 10 second increments, showed both LDUH-12 and LDUH-8 were greater than LDUH-0 (p=0.001) but did not differ significantly from each other. However, M-APTT was ≥ 60 seconds in 13.2% of LDUH-8 patients but only 1.3% and 2.6% in LDUH-0 and LDUH-12 respectively. Controlling for covariates, LDUH was an independent predictor of APTT increase (p=0.002) as were age (p=0.023) and PT change (p=0.001). Using model-estimated geometric means, APTT change with LDUH-8 exceeded LDUH-0 (p<0.001) and approached significance compared to LDUH-12 (p=0.09). In the LDUH-8 patients with APTT ≥ 60, unexpected bleeding occurred in 2 of 12 (16.7%), and tracheostomy was delayed in a third.

CONCLUSIONS: LDUH is an independent risk factor for elevation of APTT in critically ill patients. In 13.2% receiving LDUH Q8h, APTT was ≥ 60 seconds. Unexpected bleeding may occur.

CLINICAL IMPLICATIONS: Critically ill patients on LDUH may benefit from periodic APTT monitoring especially those receiving Q8h dosing and especially before invasive procedures.

DISCLOSURE: The following authors have nothing to disclose: Ramin Pirouz, Peter Smith, Yevgeniy Vaynkof, Shashmi Balakrishna, Raja Chand, Sundeep Atluri, Louis Gerolemou, Michael Elias, Sadaf Mir, Taiyo Nishimoto, Phani Surapaneni, Elpidio Jimenez, Patricia O’Neill

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