A mesenteric traction syndrome affects near-infrared spectroscopy evaluated cerebral oxygenation because skin blood flow increases

During abdominal surgery manipulation of internal organs may induce a "mesenteric traction syndrome" (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for about 30 min. We evaluated whether MTS affects near-infrared spectroscopy (NIRS) assessed frontal lobe oxygenation (ScO2) by an increase in forehead skin blood flow (SkBF). The study intended to include 10 patients who developed MTS during pancreaticoduodenectomy and 22 patients were enrolled (age 61 +/- 8 years; mean +/- SD). NIRS determined ScO2, laser Doppler flowmetry determined SkBF, cardiac output (CO) was evaluated by pulse-contour analysis (Modelflow), and transcranial Doppler assessed middle cerebral artery mean flow velocity (MCA V-mean). MTS was identified by flushing within 60 min after start of surgery. MTS developed 20 min (12-24; median with range) after the start of surgery and heart rate (78 +/- 16 vs. 68 +/- 17 bpm; P = 0.0032), CO (6.2 +/- 1.4 vs. 5.3 +/- 1.1 L min(-1); P = 0.0086), SkBF (98 +/- 35 vs. 80 +/- 23 PU; P = 0.0271), and ScO2 (71 +/- 6 vs. 67 +/- 8%; P < 0.0001), but not MCA V-mean (32 +/- 8 vs. 32 +/- 7; P = 0.1881) were largest in the patients who developed MTS. In some patients undergoing abdominal surgery NIRS-determined ScO2 is at least temporarily affected by an increase in extra-cranial perfusion independent of cerebral blood flow as indicated by MCA V-mean. Thus, NIRS evaluation of ScO2 may overestimate cerebral oxygenation if patients flush during surgery.