Baseline and Serial Microparticle Concentration Analysis in Elderly Patients with Acute Hip Fracture Treated with Heparins

Abstract

Hip fractures in the elderly may lead to the development of venous thromboembolism and inflammation. Microparticles (MP) are small vesicles that are released upon inflammatory insults and are the main source of blood‐borne tissue factor and of pro‐coagulant phospholipids. This study was designed to measure the concentration of MPs in this patient population by ELISA methods. Thirty samples from a randomized multi‐center double blind control hip fracture study (PK‐532; n = 312) were used. The samples were collected prior to surgery (baseline) and at 1, 3, 5, and 7 days post op. Plasma from 36 healthy volunteers, normal human plasma (NHP) and pathologic pooled plasma were used as quality controls. The MP concentrations between the control groups was similar. The baselines samples demonstrated a 2.5‐fold increase in MP concentration (18.6 nM, ±10.2) in comparison to the control samples (6.7 nM, ±2.5). At post op days 1, 3, 5, and 7, three trends emerged. 15 out of 30 (50%) demonstrated a steady decrease in MP concentrations from baseline to 7 days. 5 out of 30 (16.6%) had a consecutive increase on these days. Finally 10 of 30 (33.3%) had a variable MP concentrations. These results demonstrate that patients with hip fracture requiring surgical intervention showed an up‐regulation of MPs which was down regulated by treatment with heparins. The marked fluctuations in MP levels in these patients and the lack of down regulatory responses may warrant additional pharmacologic intervention to achieve optimal anticoagulation.