title: Noninvasive Hemodynamic Measurements During Neurosurgical Procedures in Sitting Position.
abstract: BACKGROUND
  Neurosurgical procedures in sitting position need advanced cardiovascular monitoring. Transesophageal echocardiography (TEE) to measure cardiac output (CO)/cardiac index (CI) and stroke volume (SV), and invasive arterial blood pressure measurements for systolic (ABPsys), diastolic (ABPdiast) and mean arterial pressure (MAP) are established monitoring technologies for these kind of procedures. A noninvasive device for continuous monitoring of blood pressure and CO based on a modified Penaz technique (volume-clamp method) was introduced recently. In the present study the noninvasive blood pressure measurements were compared with invasive arterial blood pressure monitoring, and the noninvasive CO monitoring to TEE measurements.
  
  
  METHODS
  Measurements of blood pressure and CO were performed in 35 patients before/after giving a fluid bolus and a change from supine to sitting position, start of surgery, and repositioning from sitting to supine at the end of surgery. Data pairs from the noninvasive device (Nexfin HD) versus arterial line measurements (ABPsys, ABPdiast, MAP) and versus TEE (CO, CI, SV) were compared using Bland-Altman analysis and percentage error.
  
  
  RESULTS
  All parameters compared (CO, CI, SV, ABPsys, ABPdiast, MAP) showed a large bias and wide limits of agreement. Percentage error was above 30% for all parameters except ABPsys.
  
  
  CONCLUSIONS
  The noninvasive device based on a modified Penaz technique cannot replace arterial blood pressure monitoring or TEE in anesthetized patients undergoing neurosurgery in sitting position.
authors.affiliation: *Department of Anesthesiology ‡Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center, Johannes Gutenberg University Mainz, Mainz †Department of Anesthesiology, Christophorus Hospital, Coesfeld, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Schramm
authors.forename: Irene
authors.initials: I
authors.lastname: Tzanova
authors.forename: Tilman
authors.initials: T
authors.lastname: Gööck
authors.forename: Frank
authors.initials: F
authors.lastname: Hagen
authors.forename: Irene
authors.initials: I
authors.lastname: Schmidtmann
authors.forename: Kristin
authors.initials: K
authors.lastname: Engelhard
authors.forename: Gunther
authors.initials: G
authors.lastname: Pestel
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D062186:Arterial Pressure; D001794:Blood Pressure; D001795:Blood Pressure Determination; D002302:Cardiac Output; D017548:Echocardiography, Transesophageal; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D019635:Neurosurgical Procedures / Q000379:methods*; D056888:Patient Positioning; D011187:Posture / Q000502:physiology; D015203:Reproducibility of Results; D013318:Stroke Volume; D016683:Supine Position