title: The efficacy of skin temperature for block assessment after infraclavicular brachial plexus block.
abstract: BACKGROUND
  Although it has been reported that an increase in skin temperature indicates block success with higher specificity and sensibility than skin sensitivity to pinprick and cold, the methodology previously used computer-assisted infrared thermography, a technique that is expensive and requires substantial personnel training. In this prospective observational study, we evaluated whether a simple infrared thermometer can reliably predict block effectiveness after infraclavicular brachial plexus blockade.
  
  
  METHODS
  Thirty consecutive patients undergoing upper limb surgery under infraclavicular block were enrolled. From the end of the local anesthetic injection, skin temperature was measured in all four major nerve distribution areas, and the sensory block onset (using cold and pinprick with 0 = no sensation to 2 = normal) were evaluated every 5 min for 30 min. A successful block was defined as the absence of sensation to cold (swab soaked with alcohol) and pinprick (needle) with a score of "0" within 30 min after the injection in the 4 major nerve distribution areas (radial, ulnar, median and musculocutaneous). Skin temperature measurements were performed using a noncontact temperature probe.
  
  
  RESULTS
  One-hundred-twenty nerves (30 patients, 4 nerves per patient) were anesthetized. Twenty-five patients had a successful block. Four patients required supplementation for block failure. General anesthesia was performed in one patient. Skin temperature variation was not different among different nerves. There was a statistically significant increase in cutaneous temperature after nerve block compared to the same skin area before the procedure (P < 0.0001 from T5 to T30). Average temperature variations in blocked versus unblocked nerves at the same time were significantly different (P < 0.05 at T5 then P < 0.0001 from T10 to T30). When temperature in a specific sensory territory increased 1 degree C or more, at 5 and 10 min, the specific nerve was blocked (the score was "0"). Thus, when temperature changes in all 4 nerves were noted at 5 and 10 min, the block was successful at 30 min. No change in temperature in the contralateral arm or in the core temperature was observed.
  
  
  CONCLUSIONS
  Skin temperature assessment with an infrared thermometer is a reliable, simple and early indicator of a successful nerve block.
authors.affiliation: Department of Anesthesiology and Intensive Care, University Hospital of Toulouse, Rangueil Hospital-Orthopedic section, University Paul Sabatier, Toulouse, France. vincentminville@yahoo.fr
authors.forename: Vincent
authors.initials: V
authors.lastname: Minville
authors.forename: Agnés
authors.initials: A
authors.lastname: Gendre
authors.forename: Jan
authors.initials: J
authors.lastname: Hirsch
authors.forename: Stein
authors.initials: S
authors.lastname: Silva
authors.forename: Benoît
authors.initials: B
authors.lastname: Bourdet
authors.forename: Carole
authors.initials: C
authors.lastname: Barbero
authors.forename: Olivier
authors.initials: O
authors.lastname: Fourcade
authors.forename: Kamran
authors.initials: K
authors.lastname: Samii
authors.forename: Hervé
authors.initials: H
authors.lastname: Bouaziz
mesh_terms: D000368:Aged; D001917:Brachial Plexus; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009407:Nerve Block; D018401:Sample Size; D012881:Skin Temperature / Q000187:drug effects*; D013821:Thermometers; D034941:Upper Extremity / Q000601:surgery