title: Non-invasive blood haemoglobin and plethysmographic variability index during brachial plexus block.
abstract: BACKGROUND
  Plethysmographic measurement of haemoglobin concentration ([Formula: see text]), pleth variability index (PVI), and perfusion index (PI) with the Radical-7 apparatus is growing in popularity. Previous studies have indicated that [Formula: see text] has poor precision, particularly when PI is low. We wanted to study the effects of a sympathetic block on these measurements.
  
  
  METHODS
  Twenty patients underwent hand surgery under brachial plexus block with one Radical-7 applied to each arm. Measurements were taken up to 20 min after the block had been initiated. Venous blood samples were also drawn from the non-blocked arm.
  
  
  RESULTS
  During the last 10 min of the study, [Formula: see text] had increased by 8.6%. The PVI decreased by 54%, and PI increased by 188% in the blocked arm (median values). All these changes were statistically significant. In the non-blocked arm, these parameters did not change significantly.
  
  
  CONCLUSIONS
  Brachial plexus block significantly altered [Formula: see text], PVI, and PI, which indicates that regional nervous control of the arm greatly affects plethysmographic measurements obtained by the Radical-7. After the brachial plexus block, [Formula: see text] increased and PVI decreased.
authors.affiliation: Department of Anaesthesia, Faculty of Health Sciences, Linköping University, Linköping 585 85, Sweden christian.bergek@lio.se.
authors.forename: C
authors.initials: C
authors.lastname: Bergek
authors.affiliation: Department of Anaesthesia, Faculty of Health Sciences, Linköping University, Linköping 585 85, Sweden.
authors.forename: J H
authors.initials: JH
authors.lastname: Zdolsek
authors.affiliation: Department of Anaesthesia, Faculty of Health Sciences, Linköping University, Linköping 585 85, Sweden Research Unit, Södertälje Hospital, Södertälje, Sweden.
authors.forename: R G
authors.initials: RG
authors.lastname: Hahn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000779:Anesthetics, Local / Q000008:administration & dosage; D065527:Brachial Plexus Block / Q000379:methods*; D005260:Female; D006225:Hand / Q000098:blood supply; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage; D008875:Middle Aged; D010092:Oximetry / Q000379:methods / Q000706:statistics & numerical data; D010991:Plethysmography / Q000379:methods / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local; D006454:Hemoglobins; D008619:Mepivacaine
keywords: haemoglobinometry; nerve blockade; perfusion; photoplethysmography; vasodilation