There is continuing debate as to whether the use of electrical stimulation that aids in localizing nerves is also beneficial for optimizing placement of nerve catheters and will lead to improved clinical outcomes such as reductions in pain scores and opioid consumption.
We undertook a retrospective, non-randomized comparison of stimulating and non-stimulating nerve catheters in 419 patients undergoing total knee replacement between December 2002 and July 2004. Pre-operatively, patients received sciatic and femoral nerve blocks, with a catheter for the femoral nerve. In 159 patients, a stimulating (Stimucath, Arrow International, Reading, PA) and, in 260 patients, a non-stimulating (Contiplex, BBraun, Melsungen, Germany) catheter system was used. Postoperatively, pain scores and morphine consumption were recorded at 4-hour intervals until the first postoperative morning. In a subset of 85 patients, the postoperative evaluation period was lengthened to three days.
Post-operative visual analogue scores (VAS) for pain were similar in the two groups during the first 24 hours (P = 0.305). In patients followed for three days, VAS scores did not differ on any of the days (P = 0.427). Total morphine consumption did not differ on the first post-operative day (Stimulating: 12.4 [10.1-14.7] vs. non-stimulating: 10.4 [8.9-11.8]; mean [95% CI]; P=0.140) or on subsequent days.
The practical advantages of the stimulating catheter, as by reported by previous investigators, were not obvious in this clinical situation. In terms of outcome measures such as pain scores and morphine consumption, we found no significant differences between stimulating and non-stimulating catheters.