Acetylcholine sweat test: an effective way to select patients for lumbar sympathectomy.

Although lumbar sympathectomy can benefit patients with critical limb ischaemia, many derive no benefit from the procedure. The poor prediction of outcome may be related to pre-existing damage to the sympathetic fibres. We assessed sympathetic nerve function with the acetylcholine sweatspot test before and after lumbar sympathectomy in 31 patients with critical limb ischaemia. Of 9 patients with normal sympathetic function or minor denervation preoperatively (sweatspot score > or = 8), 8 showed improvement in pain and/or healing of ischaemic lesions after sympathectomy. The procedure did not achieve denervation in the patient without improvement, as shown by persisting sympathetic activity postoperatively. By contrast, among the 22 patients with lower sweatspot scores, indicating severe or complete sympathetic denervation, only 1 showed improvement (partial) after lumbar sympathectomy. 9 patients underwent oximetry before and after the operation; in this subgroup there was a positive correlation between preoperative sweatspot score and the change in tissue partial pressure of oxygen (r2 = 0.35). Preoperative assessment of sympathetic nerve function by means of a sensitive, quantitative test of autonomic integrity can predict the outcome of the procedure with high sensitivity and specificity. A postoperative test allows verification of sympathetic denervation. We recommend use of this simple test in selecting patients for lumbar sympathectomy.