title: Association between temporal mean arterial pressure and brachial noninvasive blood pressure during shoulder surgery in the beach chair position during general anesthesia.
abstract: BACKGROUND
  Estimation of cerebral perfusion pressure during elective shoulder surgery in the beach chair position is regularly performed by noninvasive brachial blood pressure (NIBP) measurements. The relationship between brachial mean arterial pressure and estimated temporal mean arterial pressure (eTMAP) is not well established and may vary with patient positioning. Establishing a ratio between eTMAP and NIBP at varying positions may provide a more accurate estimation of cerebral perfusion using noninvasive measurements.
  
  
  METHODS
  This prospective study included 57 patients undergoing elective shoulder surgery in the beach chair position. All patients received an interscalene block and general anesthesia. After the induction of general anesthesia, values for eTMAP and NIBP were recorded at 0°, 30°, and 70° of incline.
  
  
  RESULTS
  A statistically significant, strong, and direct correlation between NIBP and eTMAP was found at 0° (r = 0.909, P ≤ .001), 30° (r = 0.874, P < .001), and 70° (r = 0.819, P < .001) of incline. The mean ratios of eTMAP to NIBP at 0°, 30°, and 70° of incline were 0.939 (95% confidence interval [CI], 0.915-0.964), 0.738 (95% CI, 0.704-0.771), and 0.629 (95% CI, 0.584-0.673), respectively. There was a statistically significant decrease in the eTMAP/NIBP ratio as patient incline increased from 0° to 30° (P < .001) and from 30° to 70° (P < .001).
  
  
  CONCLUSIONS
  The eTMAP-to-NIBP ratio decreases as an anesthetized patient is placed into the beach chair position. Awareness of this phenomenon is important to ensure adequate cerebral perfusion and prevent hypoxic-related injuries.
authors.affiliation: Nova Southeastern University, College of Osteopathic Medicine, Fort Lauderdale, FL, USA. Electronic address: jacob.john.triplet@gmail.com.
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Triplet
authors.affiliation: Holy Cross Orthopedic Institute, Fort Lauderdale, FL, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Lonetta
authors.affiliation: Holy Cross Orthopedic Institute, Fort Lauderdale, FL, USA.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Everding
authors.affiliation: Holy Cross Orthopedic Institute, Fort Lauderdale, FL, USA.
authors.forename: Molly A
authors.initials: MA
authors.lastname: Moor
authors.affiliation: Holy Cross Orthopedic Institute, Fort Lauderdale, FL, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Levy
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General; D062186:Arterial Pressure / Q000502:physiology*; D001795:Blood Pressure Determination; D002560:Cerebrovascular Circulation / Q000502:physiology*; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block; D056888:Patient Positioning; D011446:Prospective Studies; D012785:Shoulder Joint / Q000601:surgery*
keywords: Mean arterial pressure; beach chair position; cerebral hypoxic injury; cerebral perfusion pressure; noninvasive blood pressure; shoulder surgery