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Ann Thorac Surg 2005;80:467-470
© 2005 The Society of Thoracic Surgeons

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Original article: General thoracic

Oximetry-Derived Perfusion Index for Intraoperative Identification of Successful Thoracic Sympathectomy

Department of Surgery and Anesthesiology, University of Florida, Gainesville, Florida

Accepted for publication February 23, 2005.

^_* Address reprint requests to Dr Klodell, Thoracic and Cardiovascular Surgery, PO Box 100286, Gainesville, FL 32610 (Email: klodell{at}surgery.ufl.edu).

Presented at the Poster Session of the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.

	Abstract

Top Abstract Introduction Material and Methods Results Comment References

 
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 1 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.

	Introduction

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Endoscopic thoracic sympathectomy is commonly performed in patients with upper limb or thoracic hyperhidrosis. Although the surgery is generally considered effective, a small proportion of patients have incomplete resolution of their symptoms. Intraoperative real-time assessment of the degree of sympathectomy may provide feedback that is of significant benefit for surgeons early in their experience with endoscopic thoracic sympathectomy, or in cases of unclear anatomy.

Pulse oximetry is considered a standard of monitoring in every patient undergoing a surgical procedure to provide assessment of arterial oxygenation. In addition, pulse oximetry provides information regarding quantitative changes in heart rate and arterial flow, as the built-in software automatically calculates the perfusion index (PI) [1, 2].

PI = (_max – _min)/_maxmean

where _max is peak velocity and _min is lowest velocity.

Successful thoracic sympathectomy is invariably associated with an immediate decrease in upper limb arterial resistance and increased arterial blood flow. These changes are manifested clinically by an increase in the skin temperature and the PI. Our standard of anesthetic practice is to place a pulse-oximetry sensor on the ipsilateral extremity to the surgical site. To our knowledge there are no data in the literature addressing intraoperative monitoring during hyperhidrosis surgery using the PI. This study evaluated the usefulness of intraoperative pulse oximetry as a monitor for successful thoracic sympathectomy through the assessment of changes in PI.

	Material and Methods

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After institutional review board approval and signed informed consent, 10 adult subjects were studied. The duration of preoperative symptoms ranged from 1 to 23 years, and all patients had used at least one noninvasive treatment for hyperhidrosis. No patient had previously undergone surgical treatment for hyperhidrosis, and all suffered from bilateral symptoms. All patients underwent surgical thoracic sympathectomy for upper limb hyperhidrosis under general anesthesia.

Anesthetic Technique
All patients had a standardized general anesthetic with mechanical ventilation. All patients were intubated with a left-sided double-lumen tube (Mallinckrodt Inc, Hazelwood, MO). Monitors included electrocardiography, capnography, temperature, and noninvasive ankle blood pressure measurements. A pulse-oximeter sensor (NELLCOR OxiMax, Tyco Healthcare, Mansfield, MA) connected to a monitor with the PI displayed for each sensor was placed on the middle finger of each hand. A reference pulse-oximetry sensor was placed on the ipsilateral earlobe. No pharmacologic agents were administered, or changes in the concentration of isoflurane made, within 5 minutes of each period of data collection.

Surgical Technique
All subjects were placed in the semi-Fowler position. Video thoracoscopy was performed, using two ports in all patients, to visualize the thoracic sympathetic chain and perform the sympathectomy. In 7 patients this was accomplished through 5-mm ports, and in 3 patients 3-mm ports were used. Carbon dioxide was insufflated into the operative hemithorax to a pressure of 8 to 10 mm Hg to enhance surgical exposure. All patients underwent division of the thoracic chain at the third (T3) and fourth (T4) thoracic levels under direct vision. Patients also suffering from facial hyperhidrosis underwent additional sympathectomy at the second thoracic level (T2).

Division of the thoracic chain was accomplished with electrocautery with a laparoscopic hook in all cases. In addition, the cautery was extended along the third rib laterally 4 to 5 cm in all cases to identify and divide any accessory nerve of Kuntz [3, 4]. After hemostasis was verified, the carbon dioxide was evacuated from the thorax, the lung was inflated, and the incisions were sealed without use of chest tubes. The procedure was repeated on the contralateral side in similar fashion. In all patients the right sympathectomy was performed first, followed immediately by operation on the left side. All patients were interviewed before discharge from the postanesthesia care unit and on return to the clinic approximately 2 weeks postoperatively, and by telephone interview at 3 months. The degree of resolution of symptoms and overall satisfaction were noted. A standard questionnaire was applied to all patients on return to the clinic, or by mail for those who were unable to return because of travel distance.

Data Collection
Intraoperative data collected included end-tidal concentration of isoflurane, expired carbon dioxide, inspired fraction of oxygen, blood pressure, heart rate and rhythm, peripheral oxygen saturation, and esophageal temperature. Oximetry-derived pulse wave amplitude and PI were measured on the upper extremities and earlobes. Data points were recorded before the division of the sympathetic trunk and then every minute for 5 consecutive minutes. Subsequent data were collected every 5 minutes until the procedure was concluded.

An increase in pulse wave amplitude and PI by at least 50% was arbitrarily considered intraoperative evidence of a successful sympathectomy. The operating surgeon was blinded to the PI data until conclusion of the procedure.

Statistical Analysis
This study was designed with a power of 80% and level of 0.05, to detect a 50% difference before and after the procedure. On the basis of these criteria, 10 patients were required. Descriptive statistics were used for demographic data. Serial changes in hemodynamics and oximetry variables were analyzed with repeated-measures analysis of variance and Bonferroni test for post-hoc comparison. A paired Student’s t test was used to compare values between the finger and reference probes at the same sampling points. All data were analyzed using commercial software (Sigma Stat, Culverton, CA).

	Results

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There were 5 men and 5 women with an average age of 22.4 years (range, 10 to 38 years). Average height for the men was 179 cm (range, 170 to 196 cm), whereas for the women it was 164 cm (range, 150 to 170 cm). Average weight for the male group was 85.3 kg (range, 72.1 to 104 kg), whereas for the female group it was 55.8 kg (range, 41.7 to 65.3 kg). No patient had diabetes, any history of upper extremity trauma, hypertension, Raynaud symptoms, vascular disease, or oral vasodilator use. Oximetric waveforms in both the finger and earlobe probes were adequate in all subjects. All patients underwent the procedure without surgical complications, and were able to return home the day of surgery.

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; Table 1). This dramatic increase occurred as early as 1 minute after transection of the sympathetic chain, and within 2 minutes in all cases. The increased PI rapidly approached its peak value, where it remained throughout the remainder of the procedure. This was consistent in both right and left sides (Fig 1). The pulse wave amplitude was seen to increase in proportion to the PI. The reference PI earlobe probe as well as the hemodynamics remained constant. When questioned in the postanesthesia care unit, and again at the 2-week clinic visit, and at 3 months’ follow-up telephone interview, all patients responded that their symptoms were either completely resolved, or mostly resolved. Additionally, all responded that they were either completely or mostly satisfied with the procedure. All 10 patients reported that, in retrospect, they would still choose to undergo the procedure.

View larger version (10K): [in this window] [in a new window]   Fig 1. Ipsilateral limb and reference probe response to sympathectomy. Values are mean ± standard error of the mean. (Left) Comparison of pulsatility index between finger () and ear () is shown for the right side. *p < 0.001 compared with other sampling times; t p < 0.05 compared with reference probe (earlobe). (Right) Comparison of pulsatility index between finger () and ear () is shown for the left side. *p < 0.029 compared with other sampling times; t p< 0.05 compared with reference probe (earlobe).

	Comment

Top Abstract Introduction Material and Methods Results Comment References

It is well known that sympathetic blockade of the high thoracic chain is associated with arterial vasodilation of the upper extremity [11, 12]. The local vascular resistance decreases with a concomitant increase in arterial flow. Indices that measure changes in perfusion flow are dependent on vascular tone. An increased PI is an indicator of vasodilation resulting from sympathetic blockade [13, 14]. Some authors [15, 16] have advocated intraoperative monitoring with laser Doppler blood flow measurement as a means of identifying complete sympathectomy. Others have advocated direct temperature measurement of the palmar area, with an increase by more than 1°C being predictive of a good outcome [17–21]. Although these methods also indirectly detect an increase in blood flow to the ipsilateral extremity, they require additional monitoring equipment and expense. Additionally, a temperature change of greater than 1°C takes longer to manifest than a change in the PI.

Pulse oximetry is a standard monitor for every patient undergoing general anesthesia. Pulse oximetry evaluates the degree of pulsatile flow by automatically deriving the pulse wave amplitude. The built-in software will also automatically display the PI of the sampled bed. Changes in pulse wave amplitude and PI as determined by intraoperative pulse oximetry represent a rapid and attractive alternative to more conventional methods to assess changes in upper extremity blood flow after sympathectomy. The pulse oximeter is ubiquitous in most operating rooms, relatively inexpensive, and requires no additional steps for interpretation of the data. Our results indicate that an effective thoracic sympathectomy results in significant changes in blood flow to the ipsilateral extremity. These are reliably detected by a rapid and sustained increase in PI in all subjects. This change is readily discernible as early as 1 minute after transection of the sympathetic chain. Although limited by the lack of treatment failures in our series, we would suggest that the PI might serve as a useful intraoperative marker of successful sympathectomy during endoscopic thoracic sympathectomy procedures.

	References

Top Abstract Introduction Material and Methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Charles T. Klodell Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Klodell, C. T. Articles by Gravenstein, N. Search for Related Content PubMed PubMed Citation Articles by Klodell, C. T. Articles by Gravenstein, N. Related Collections Mediastinum