Foot drop in the setting of VA-ECMO: A possible alternative mechanism to ischemia

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used widely as part of extracorporeal resuscitation (ECPR). Prolonged VA-ECMO may be associated with the development of foot drop, often secondary to limb ischemia. We report on three patients who developed foot drop following prolonged ECMO use, and we propose an alternative mechanism to ischemia. Three male patients, mean age 46.3 years, underwent peripheral VA-ECMO support, for an average of 22.6 days (17-25 days), two patients following ECPR and one post-cardiotomy shock. All patients underwent distal femoral artery perfusion cannula insertion within 60 min of ECMO cannulation. An intra-aortic balloon pump (IABP) was inserted on the contralateral side. During ECMO support the distal circulations in both legs were evaluated clinically, using Doppler ultrasound and measurement of blood flow in the distal cannula using a flow meter. One patient developed a foot drop on the side of the femoral cannula, one patient on the opposite side, and one patient bilaterally. Two patients needed LVAD, and one patient was successfully decannulated. All clinical parameters, Doppler flow measurements, and blood flow quantification (130-150 ml/min) were within normal limits throughout the support period. No ischemia was detected in the affected leg, nor was there evidence of compartment syndrome. Nerve conduction studies were inconclusive. We propose that the position and the immobility of the affected leg to enable groin cannula care may contribute to the development of foot drop due to compression /traction of the peroneal nerve.