title: Is the change of percutaneous oxygen pressure available to judge the effects of brachial plexus block?
abstract: BACKGROUND
  To know the objective methods of the effects of the brachial plexus block, we studied the changes in percutaneous oxygen pressure (tcPO₂) with the hypothesis that tcPO₂ increases significantly on the blocked arm in comparison with the non-blocked arm, a phenomenon which is connected with vasodilation following the brachial plexus block.
  
  
  METHODS
  Fifteen patients scheduled for upper extremity surgery, aged 20 to 70 years, with ASA physical status I or II were included. Before anaesthesia, the electrodes used to measure tcPO₂ were put on the radial side of the forearm and upper arm of both the right and left sides (a total of 4 electrodes). Oxygen at 6 L min⁻¹ was administered by a facial mask. Once midazolam 1-2 mg and fentanyl 50 μg had been administered intravenously, a propofol infusion was started at a dose of 2 mg kg⁻¹ h⁻¹. The interscalene block was performed by means of a nerve stimulator, using 20 mL of 1% lidocaine solution combined with 20 mL of 0.75% ropivacaine solution. TcPO₂ was measured just before the block and 30 minutes after the block.
  
  
  RESULTS
  TcPO₂ in both forearm and upper arm significantly increased after the block in both sides namely, blocked and non-blocked. No difference was observed in tcPO₂ between the blocked side and non-blocked side.
  
  
  CONCLUSIONS
  Changes of tcPO₂ are not useful in order to assess the effects of the interscalene block under oxygen administration.
authors.affiliation: Department of Anaesthesiology, Harada Hospital, Toyooka, Iruma, Saitama, Japan. nishit-tky@umin.ac.jp.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nishiyama
mesh_terms: D000328:Adult; D000368:Aged; D000577:Amides / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D065527:Brachial Plexus Block / Q000379:methods*; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008874:Midazolam / Q000008:administration & dosage; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage* / Q000378:metabolism; D011312:Pressure; D015742:Propofol / Q000008:administration & dosage; D000077212:Ropivacaine; D034941:Upper Extremity / Q000601:surgery; D014664:Vasodilation / Q000187:drug effects; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine; D008012:Lidocaine; D008874:Midazolam; D010100:Oxygen; D005283:Fentanyl; D015742:Propofol
keywords: brachial plexus block; brachial plexus blockade; efficacy; interscalene block; percutaneous oxygen pressure