Limitation of impedance plethysmography in assessing efficacy of dihydroergotamine-heparin prophylaxis of deep vein thrombosis.

ABSTRACT

The sensitivity of impedance plethysmography (IPG) for diagnosing deep vein thrombosis was evaluated in the presence of dihydroergotamine, an agent with significant venoconstrictor activity. In a prospective, randomized, controlled clinical trial, 105 patients undergoing total hip replacement surgery were investigated to evaluate the thromboprophylactic efficacy of DHE-Heparin using IPG and 125I-Fibrinogen Leg Scanning to monitor the incidence of DVT. Retrospective analysis of the IPG data indicated that DHE-Heparin impaired the sensitivity of impedance plethysmography by decreasing venous capacitance and venous outflow. Although the patient sample size was relatively small, the results showed trends which suggested that the utility of impedance plethysmography for diagnosing DVT was limited in the presence of a vasoactive agent. Alternate noninvasive diagnostic methods may need to be considered in select patients receiving concomitant medications possessing venoconstrictor activity.