title: Pulse transit time as a quick predictor of a successful axillary brachial plexus block.
abstract: BACKGROUND
  It can take up to 30 min to determine whether or not axillary block has been successful. Pulse transit time (PTT) is the time between the R-wave on electrocardiography (ECG) and the arrival of the resulting pressure pulse wave in the fingertip measured with photoplethysmography. It provides information about arterial resistance. Axillary block affects vasomotor tone causing loss of sympathetic vasoconstriction resulting in an increased PTT. Early objective assessment of a block can improve efficacy of operating room time and minimize patient's fear of possible conversion to general anesthesia. This study explores whether PTT can objectively, reliably and quickly predict a successful axillary block.
  
  
  METHODS
  Forty patients undergoing hand surgery under axillary block were included. A three-lead ECG and photoplethysmographic sensors were placed on both index fingers. Measurements were made from 2 min before until 30 min after induction of the block or less if the patient was transferred for operation. Afterwards, PTT was calculated as the time between the R-wave on ECG and a reference point on the photoplethysmogram. To assess the change in PTT caused by the block, the PTT difference between the control and blocked arm was calculated. Sensitivity and specificity of PTT difference were calculated using receiver operating characteristic analysis.
  
  
  RESULTS
  In a successful block, the mean PTT difference significantly increased after 3 min by 12 (standard error of the mean 3.9) ms, sensitivity 87% and specificity 71% (area under the curve 0.87, P = 0.004).
  
  
  CONCLUSIONS
  PTT is a reliable, quick and objective method to assess whether axillary block is going to be successful or not.
authors: Department of Anesthesiology, Erasmus University Medical Center, Rotterdam, The Netherlands. m.kortekaas@erasmusmc.nl
authors: M C
authors: MC
authors: Kortekaas
authors: S P
authors: SP
authors: Niehof
authors: M H N
authors: MH
authors: van Velzen
authors: E M
authors: EM
authors: Galvin
authors: F J P M
authors: FJ
authors: Huygen
authors: R J
authors: RJ
authors: Stolker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001917:Brachial Plexus; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009407:Nerve Block / Q000379:methods*; D011237:Predictive Value of Tests; D063177:Pulse Wave Analysis; D012372:ROC Curve; D015203:Reproducibility of Results; D034941:Upper Extremity / Q000601:surgery; D055815:Young Adult