Success of ultrasound guided popliteal sciatic nerve catheters is not influenced by nerve stimulation

There is debate as to whether nerve stimulation (NS) is required to place peripheral nerve catheters when using ultrasound (US) guidance. There is conflicting evidence for whether stimulating catheters improve postoperative analgesia compared to non-stimulating catheters. The use of US in combination with NS has been shown to be superior to NS alone in terms of popliteal nerve blockade. Given the previously published reports, we hypothesized that there is improvement in sensory and motor blockade for stimulating popliteal perineural catheters placed under US guidance when NS is used.

Following IRB approval, 21 patients undergoing elective foot and ankle surgery were randomly assigned to either a US or US+NS-guided continuous popliteal sciatic nerve block using a lateral approach. The primary end-point of the study was successful nerve blockade at 20 minutes. Secondary end-points included: block performance time, minimum stimulating current, pain scores on postoperative day 1 and day 2, and patient satisfaction.

There was no significant difference in successful nerve blockade at 20 minutes in the US versus US+NS groups (73% vs. 80%, p = 1). Procedure time was significantly shorter in the US only group (median 62 seconds vs. 130.5 seconds, p < 0.01). Postoperative pain scores and overall patient satisfaction were not significantly different between the two groups.

We have found that the addition of NS provides no benefit over US alone. US alone was associated with a significantly shorter block performance time. US+NS showed no significant difference in pain control, patient satisfaction, or block success.