title: Lower Extremity Near-infrared Spectroscopy After Popliteal Block For Orthopaedic Foot Surgery.
abstract: BACKGROUND
  Noninvasive measurement of cutaneous tissue oxygenation using near-infrared spectroscopy (NIRS) has become common in peri-operative care. Following institution of peripheral nerve blocks, neurovascular alterations in the blocked region have been described.
  
  
  OBJECTIVE
  The primary aim of this study encompassed the assessment of the influence of a popliteal block on changes in regional oxygen saturation (SrO2), and the location of most prominent changes.
  
  
  METHODS
  We conducted a prospective randomised controlled trial. Hundred twenty patients who received a popliteal block for foot surgery were included. Popliteal block was performed under echographic guidance. The patients were randomized in 3 groups according to the location of the SrO2 electrodes on the legs. Bilateral SrO2 measurements were performed simultaneously. SrO2 in the operated leg and in the control leg was measured at baseline and 1, 5, 10, 15, and 30 minutes after the perineural injection. We quantified the evolution in SrO2 by calculating over time the differences in SrO2 values between the operated and control leg (=ΔSrO2).
  
  
  RESULTS
  At 30 minutes, ΔSrO2 increased significantly (p<0.05) at the plantar side of the foot (11.3% ± 2.9%), above the ankle (4.9% ± 1.3%) and the popliteal fossa (3.6% ± 1.2%).
  
  
  CONCLUSIONS
  At 30 minutes after institution of the popliteal block, ΔSrO2 was most prominent at the plantar side of the foot as compared with measurement performed above the ankle or under the knee.
authors: Department of Anesthesia and Critical Care Medicine, Maria Middelares Hospital, Ghent, Belgium.
authors: Stijn
authors: S
authors: Van de Velde
authors: Department of Anesthesia and Critical Care Medicine, Maria Middelares Hospital, Ghent, Belgium.
authors: Alain F
authors: AF
authors: Kalmar
authors: Department of Anesthesia and Critical Care Medicine, Maria Middelares Hospital, Ghent, Belgium.
authors: Matthias
authors: M
authors: Raes
authors: Department of Anesthesiology and Perioperative Medicine, Acute and Chronic Pain Therapy, University Hospital, Brussels, Belgium.
authors: Jan
authors: J
authors: Poelaert
authors: Department of Orthopaedic Surgery and Traumatology, Maria Middelares hospital, Ghent, Belgium.
authors: Tom
authors: T
authors: Lootens
authors: Department of Anesthesia and Critical Care Medicine, Maria Middelares Hospital, Ghent, Belgium.
authors: Henk
authors: H
authors: Vanoverschelde
keywords: INVOS; Locoregional anaesthesia; NIRS; Neurovascular effects; Popliteal block; Tissue oxygen saturation