Clinical Outcomes After Conversion from Low-Molecular-Weight Heparin to Unfractionated Heparin for Venous Thromboembolism Prophylaxis
We do not contend that UFH is as safe as LMWH with regard to HIT for all populatons, but rather that the increased risk is not manifest in all patient populations and settings and so the increased cost may not be justified in low-risk patients. Indeed while variability in HIT risk among patients is well documented [3,12], the guidelines for prophylaxis do not generally take this into account when recommending particular VTE prophylaxis strategies.Clinical practice guidelines do recommend different degrees of monitoring the platelet count based on risk of HIT however.
Our study had limitations, chief of which is the retrospective nature of the analysis; however, the methodology we used was similar to those of previous publications [4,5,8].We may have missed some cases of HIT if a clinician did not order the assay in all appropriate patients but there is no reason to think that likelihood was any different pre- and post-intervention. In addition, though we reviewed every case of hospital-acquired thrombosis, it is possible that the clinical reviewers may have missed cases of HITT, especially if the thrombosis occurred before a substantial drop in the platelet count, which is rare but possible. Here too the chance of missing actual cases did not change between the pre-and post-intervention. Our study examined prophylaxis with heparin use and not therapeutic uses. Finally, while noting the acquisition cost reduction achieved with conversion to UFH, we were not able to calculate any excess expense attributed to the rare case of HIT and HITT that occurred. We believe our results are generalizable to hospitals with similar patient profiles.
The idea that patients with different risk factors might do well with different prophylaxis strategies needs to be better appreciated. Such information could be used as a guide to more individualized prophylaxis strategy aided by clinical decision support embedded within the EMR. In this way the benefit of LMWH in avoiding HIT could be reserved for those patients at greatest risk of HIT while simultaneously allowing hospitals not to overspend for prophylaxis in patients who will not benefit from LMWH. Such a strategy would need to be tested prospectively before widespread adoption.
As a result of our internal analysis we have altered our EMR-based best practice alert to conform to the 2013 American Society of Hematology guidelines [15],which is more informative than our original BPA. Specifically, the old guideline only warned if the platelet count was < 100,000/mm3 in association with heparin. The revision notified if there is a > 30% fall regardless of the absolute count and informed prescribers of the 4T score to encourage more optimum use of the HIT assay, avoiding its use for low risk scores and encouraging its use for moderate to high risk scores. We are also strengthening the emphasis that moderate to high risk 4T patients receive alternative anticoagulation until results of the HIT assay are available as we found this not to be a be a universal practice. We recommend similar self-inspection to other institutions.
Corresponding author: Barry R. Meisenberg, MD, Anne Arundel Medical Center, 2001 Medical Parkway, Annapolis, MD 21401, Meisenberg@aahs.org.
Financial disclosures: None.
Author contributions: conception and design, JR, BRM; analysis and interpretation of data, KW, JR, BRM; drafting of article, JR, BRM; critical revision of the article, KW, JR, BRM; statistical expertise, KW, JR; administrative or technical support, JR; collection and assembly of data, KW, JR.
