Oximetry-derived perfusion index for intraoperative identification of successful thoracic sympathectomy

Background. Endoscopic thoracic sympathectomy treats patients with hyperhidrosis. Laser Doppler flow and changes in palmar temperature have been advocated for intraoperative monitoring. The pulse oximetry-derived perfusion index (PI) is used to quantify pulsatile blood flow at the pulse oximeter. Upper limb sympathectomy is associated with increased flow to the ipsilateral extremity; thus we postulate that it will increase PI. We evaluated changes in intraoperative PI as a monitor of successful thoracic sympathectomy. Methods. After institutional review board approval and informed consent, 10 adult patients undergoing bilateral endoscopic thoracic sympathectomy under general anesthesia were studied. Finger pulse-oximetry probes were placed on each hand, and reference probes on each earlobe. Hemodynamic variables and PI were continuously monitored. Data were collected immediately before and every minute after sympathectomy for 5 minutes. Anesthetic management remained constant throughout. A successful sympathectomy was defined by a twofold increase in PI on the ipsilateral arm. Data were analyzed with analysis of variance and Student's t tests; a p < 0.05 was considered significant. Results. Baseline oximetric waveforms were adequate in all subjects. Right sympathectomy was associated with a 372% increase in PI (P < 0.0001), and left sympathectomy with a 316% increase in PI (p < 0.029). This occurred as early as I minute after transection of the sympathetic chain. The PI in the reference probes as well as the hemodynamics remained constant. All patients had postoperative resolution of their hyperhidrosis symptoms. Conclusions. In patients with hyperhidrosis of the upper extremity, the intraoperative PI derived from pulse oximetry is an additional indicator of successful thoracic sympathectomy.