title: Early postoperative subcutaneous tissue oxygen predicts surgical site infection.
abstract: BACKGROUND
  Subcutaneous oxygen partial pressure is one of several determinants of surgical site infections (SSIs). However, tissue partial pressure is difficult to measure and requires invasive techniques. We tested the hypothesis that early postoperative tissue oxygen saturation (Sto(2)) measured with near-infrared spectroscopy predicts SSI.
  
  
  METHODS
  We evaluated Sto(2) in 116 patients undergoing elective colon resection. Saturation was measured near the surgical incision, at the upper arm, and at the thenar muscle with an InSpectra™ tissue spectrometer model 650 (Hutchinson Technology Inc., Hutchinson, MN) 75 minutes after the end of surgery and on the first postoperative day. An investigator blinded to Sto(2) assessed patients daily for wound infection. Receiver operating characteristic curves were used to analyze the performance of Sto(2) measurements as a predictor of SSI.
  
  
  RESULTS
  In 23 patients (≈ 20%), SSI was diagnosed 9 ± 5 days (mean ± SD) after surgery. Patients who did and did not develop an SSI had similar age (48 ± 14 vs 48 ± 15 years, respectively; P = 0.97) and gender (female:male, 15:8 vs 46:47, respectively), but patients who developed SSI weighed more (body mass index 32 ± 7 vs 27 ± 6 kg/m(2); P < 0.01). Sto(2) at the upper arm was lower in patients who developed SSI than in those who did not develop SSI (52 ± 22 vs 66 ± 21; P = 0.033), and these measurements had a sensitivity of 71% and specificity of 60% for predicting SSI, using Sto(2) of 66% as the cutoff point.
  
  
  CONCLUSIONS
  Sto(2) measured at the upper arm only 75 minutes after colorectal surgery predicted development of postoperative SSI, although the infections were typically diagnosed more than a week later. Although further testing is required, Sto(2) measurements may be able to predict SSI and thus allow earlier preventive measures to be implemented.
authors.affiliation: Department of Anesthesiology and Perioperative Medicine, University of Louisville Hospital, Louisville, KY 40202, USA.
authors.forename: Raghavendra
authors.initials: R
authors.lastname: Govinda
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kasuya
authors.forename: Endrit
authors.initials: E
authors.lastname: Bala
authors.forename: Ramatia
authors.initials: R
authors.lastname: Mahboobi
authors.forename: Jagan
authors.initials: J
authors.lastname: Devarajan
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
authors.forename: Ozan
authors.initials: O
authors.lastname: Akça
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003107:Colorectal Surgery / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011183:Postoperative Complications / Q000175:diagnosis / Q000378:metabolism* / Q000517:prevention & control; D011237:Predictive Value of Tests; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods; D040521:Subcutaneous Tissue / Q000378:metabolism*; D013530:Surgical Wound Infection / Q000175:diagnosis / Q000378:metabolism* / Q000517:prevention & control; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen