PHOENIX – Trauma patients probably need an elevated dose of enoxaparin – perhaps 40 mg twice daily – to prevent venous thromboembolisms, according to a prospective study of 85 trauma patients at the Palmetto Health Richland hospital in Columbia, S.C.
Also, antifactor 10a – a blood test often used in research to gauge how well enoxaparin (Lovenox) is thinning the blood – doesn’t work very well as an empiric measure of anticoagulation; thromboelastography (TEG) may be better, lead investigator Janise Phillips, Pharm.D., said at the Critical Care Congress, sponsored by the Society of Critical Care Medicine.
Dr. Janise Phillips
Her team tracked trauma patients who had at least three consecutive doses of enoxaparin prophylaxis for venous thromboembolism (VTE) and at least one peak antifactor 10a level drawn; enoxaparin doses were adjusted as needed to hit a weekly antifactor 10a level of 0.20-0.40 IU/mL, which is thought to be the therapeutic range for enoxaparin. Patients were in the ICU for a median of about 10 days, and in the hospital for about 2-3 weeks.
The types of trauma were not reported in the study, but the investigation confirms prior findings that critically ill trauma patients – and perhaps burn patients – need higher anticoagulant doses.
Overall, 65% (13) of patients on an initial enoxaparin regimen of 30 mg subcutaneously twice daily were below anti-factor 10a levels of 0.20-0.40 IU/mL after their first dose; 22% (8) were subtherapeutic after an initial dose of 40 mg once daily; and 21% (6) were subtherapeutic after an initial dose of 40 mg twice daily.
Antifactor 10a levels didn’t match well with clinical benefit. VTEs were diagnosed in 15% (4) of patients with an initial subtherapeutic antifactor 10a level, but 15% (4) bled on their subtherapeutic dose; 8.5% (4) of patients with an initial therapeutic level had a VTE, vs. none who were supratherapeutic after their initial dose. However, 9% (1) of supratherapeutic patients had an enoxaparin bleed.
“These were trauma patients in and out of surgery. A lot of the time, we had to stop the dose and hold it, which may” explain why subtherapeutic patients had the highest VTE risk, said Dr. Phillips, now a critical care pharmacist at the Cleveland Clinic hospital in Abu Dhabi, United Arab Emirates.
More than half of the patients were men, and being male was the only factor that seemed to increase the risk of subtherapeutic enoxaparin levels (P = .04). There was a trend for subtherapeutic levels in heavier patients – which might help explain the higher risk in men – and those with diminished kidney function. Even so, the fact that both VTEs and bleeding were most likely in underdosed patients could mean that antifactor 10a “is really not the best marker for VTE risk. At $80 a pop, it isn’t cost-effective, and [even] patients with therapeutic levels ended up with clots. TEG gives you a real time view of the coagulation status of the patient,” and may be the way to go, Dr. Phillips said.