Award-Winning Study Redefines Dosage of Anti-Coagulant Drug for Burn Patients

Award-Winning Study Redefines Dosage of Anti-Coagulant Drug for Burn Patients

Feb 23, 2011 1:59 PM

(SALT LAKE CITY)—Health care providers treating acute burn patients no longer should assume that the standard dosage of a commonly used anti-coagulant will be effective for all individuals. Research from University of Utah Hospital Burn Trauma Center shows that previously overlooked factors, burn-size injury and weight, should be considered when determining the amount given.

Patients with acute burns who were anticipated to be nonambulatory for greater than 48 hours were included in the study. Their prolonged hospital stays, relative immobility and multiple operative procedures placed them at risk for developing blood clots. The injuries also cause vascular damage and increase the likelihood that the patient’s blood will coagulate, putting them at higher risk for a deep vein thrombosis or a pulmonary embolism.
To date, there has been no research into the appropriate enoxaparin dose, a low-weight molecular heparin used to prevent blood clots, in burn patients. However, in the January/February 2011 issue of the Journal of Burn Care & Research, a U of U Burn Trauma research team demonstrated that administering the traditional dose of enoxaparin – 30 mg every 12 hours –might leave patients vulnerable to coagulation problems.
“Burn patients are unique ICU patients,” Hsin Lin, Pharm. D, and lead researcher in the study said.

They become hyperdynamic within 48 hours of injury, experiencing increased cardiac output and resulting in enhanced hepatic and renal clearance of drugs. Enoxaparin is metabolized primarily through the liver and cleared through kidneys. The pathophysiologic changes after burn could explain the apparent reduction in effectiveness of standard enoxaparin dosing.
Lin received the 2010 Clinical Research Award from the American Burn Association for producing high quality clinical research that will encourage the development of improved practice guidelines. Based on the study results, an equation was identified using a patient’s weight and percentage of skin burned, that clinicians can use to determine the appropriate enoxaparin dose.
A major step in determining the equation for the proper enoxaparin dosage was to measure the level of antifactor Xa (10-A) in the patient’s blood. Antifactor Xa indicates how thick a patient’s blood is, and therefore, how likely it is to clot. According to Lin, no previous research or guidelines exist about the proper enoxaparin dosage in burn patients. Research in the general surgical population has identified the optimal antifactor Xa level to be 0.2 U/mL to 0.4 U/mL. Lin found that patients with lower levels needed higher enoxaparin doses to protect against clot formation.
“Several years ago, no one would even think to check antifactor Xa levels in burn patients,” Lin said. “We usually monitor these levels closely for obese surgical patients and those with kidney failure. But we need to consider these levels for burn patients, as well. We are, perhaps, treating them with incorrect anticoagulant doses based on their unique characteristics. This finding is something that should be taken into practice and applied to patients individually.”

To determine the best method for prescribing and administering enoxaparin, Lin and her colleagues conducted a retrospective study of 38 patients admitted to the U Hospital Burn Trauma Center from June until October 2009. Clinicians anticipated patients would be confined to the bed for at least 48 hours. The median total burned body surface area was 14 percent. Individuals included in the study were free of intracranial bleeding or hemorrhagic stroke, and they had no adverse reactions to enoxaparin.

Antifactor Xa levels were drawn after the third enoxaparin dose. Thirty-five patients received 30 mg doses, and three obese patients received higher initial doses. One received 40 mg, and two received 50 mg based on their weight. Initial antifactor Xa levels showed that blood in 30 out of 38 patients was still too thick, prompting providers to increase the enoxaparin dosage.

According to Lin’s analysis, patients required a median enoxaparin dose of 50 mg every 12 hours to sufficiently elevate their antifactor Xa levels and prevent the formation of blood clots during treatment and recovery. Eight patients, however, never reached the antifactor Xa level goal before their enoxaparin treatments ended.

Patient weight and the severity of injury contribute to how the anti-coagulant is metabolized, she said. In addition, a patient’s increased metabolism speeds up how quickly the kidneys process and dispose of the drug.

“The bigger you are and how much of your body is burned plays into how much of an initial dose of enoxaparin you will receive,” she said. “It also plays into what your correct and acceptable dose would be.”
Lin and her colleagues recommend clinicians use the dosage equation to determine the proper amount of enoxaparin needed for individual patients rather than starting acute burn patients on the standard 30 mg dose.

Along with Lin, the study’s co-authors are Iris Faraklas, RN, research nurse in the Burn Trauma Intensive Care Unit, Amalia Cochran, M.D., FACS, assistant professor of surgery and a critical care surgeon in the Burn Trauma Center, and Jeffrey Saffle, M.D., FACS, professor of surgery and Burn Trauma Center director.

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