Obesity does not affect VTE risk after knee surgery

By Sarah Guy, medwireNews Reporter

Being morbidly obese does not increase the risk for developing venous thromboembolism (VTE) after total knee arthroplasty (TKA) surgery, report US researchers.

"Although it is logical to think that heavier patients require a larger dose of LMWH [low-molecular-weight heparin] or fondaparinux, the findings of this study suggest that current FDA [US Food and Drugs Administration]-approved doses of these drugs are adequate," say Banafsheh Sadeghi (University of California Davis, Sacramento) and co-workers in the Journal of Hospital Medicine.

Indeed, they found that being ambulatory 2 days after the procedure and receiving FDA-approved pharmacologic prophylaxis - rather than mechanical prophylaxis alone - reduced the risk for VTE in TKA patients.

Conversely, undergoing bilateral as opposed to unilateral TKA, and not walking until 3 days after surgery were both significant risk factors for VTE in this patient population.

The team reviewed data for 593 TKA patients treated at 15 US hospitals between 2008 and 2010, hypothesizing that obese patients with a body mass index (BMI) of more than 35 given standard-dose LMWH/fondaparinux doses would be at risk for VTE.

All patients in the cohort received at least one type of prophylaxis (pharmacologic or mechanical) in the first 24 hours after surgery; however, 130 patients developed VTE.

Multivariate analysis, adjusted for factors including age, gender, BMI, receipt of FDA-approved prophylaxis, and type of TKA, showed that neither age, gender, nor obesity (BMI >30) significantly predicted VTE.

By contrast, patients who underwent bilateral TKA (n=64) were 4.2 times more likely to develop VTE than their peers who underwent unilateral TKA (n=525).

Walking on or before the second postoperative day reduced VTE risk by 70% compared with later ambulation, report the authors, and receiving FDA-approved prophylaxis reduced VTE risk by half, compared with any other type. This latter association became nonsignificant in patients who were severely or morbidly obese (BMI >30 or >40), however.

"Our findings suggest that there may be opportunities to prevent postoperative VTE, even among high-risk patients," conclude Sadeghi et al, highlighting that the institutions involved in this study were teaching hospitals.

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