Plasma aspirin esterase activity in elderly patients undergoing elective hip replacement and with fractured neck of femur.

Plasma aspirin esterase activity was measured in eight elderly patients undergoing elective hip replacement, and in 11 presenting with femoral-neck fracture. Elective hip surgery was associated with a marked and significant decline in esterase, from 330 +/- 35.9 (SE) (nmol salicylate/ml plasma/min) pre-operatively to 236 +/- 35.6 on the third post-operative day, and returning to normal (359 +/- 24.3) at recovery phase. Patients with fractured neck of femur showed a depressed esterase activity on admission (221 +/- 12.7), rising towards normal (290 +/- 15.4) on recovery. All of these changes were accompanied by a marked acute-phase response, both to injury and surgery. The data suggest that elderly patients experiencing injury or undergoing surgery may have significantly impaired drug metabolism, at least as far as this enzyme is concerned.