title: Performance of cardiac output measurement derived from arterial pressure waveform analysis in patients requiring high-dose vasopressor therapy.
abstract: BACKGROUND
  Arterial pressure waveform analysis of cardiac output (APCO) without external calibration (FloTrac/Vigileo™) is critically dependent upon computation of vascular tone that has necessitated several refinements of the underlying software algorithms. We hypothesized that changes in vascular tone induced by high-dose vasopressor therapy affect the accuracy of APCO measurements independently of the FloTrac software version.
  
  
  METHODS
  In this prospective observational study, we assessed the validity of uncalibrated APCO measurements compared with transpulmonary thermodilution cardiac output (TPCO) measurements in 24 patients undergoing vasopressor therapy for the treatment of cerebral vasospasm after subarachnoid haemorrhage.
  
  
  RESULTS
  Patients received vasoactive support with [mean (sd)] 0.53 (0.46) µg kg(-1) min(-1) norepinephrine resulting in mean arterial pressure of 104 (14) mm Hg and mean systemic vascular resistance of 943 (248) dyn s(-1) cm(-5). Cardiac output (CO) data pairs (158) were obtained simultaneously by APCO and TPCO measurements. TPCO ranged from 5.2 to 14.3 litre min(-1), and APCO from 4.1 to 13.7 litre min(-1). Bias and limits of agreement were 0.9 and 2.5 litre min(-1), resulting in an overall percentage error of 29.6% for 68 data pairs analysed with the second-generation FloTrac(®) software and 27.9% for 90 data pairs analysed with the third-generation software. Precision of the reference technique was 2.6%, while APCO measurements yielded a precision of 29.5% and 27.9% for the second- and the third-generation software, respectively. For both software versions, bias (TPCO-APCO) correlated inversely with systemic vascular resistance.
  
  
  CONCLUSIONS
  In neurosurgical patients requiring high-dose vasopressor support, precision of uncalibrated CO measurements depended on systemic vascular resistance. Introduction of the third software algorithm did not improve the insufficient precision (>20%) for APCO measurements observed with the second software version.
authors: Department of Anaesthesiology, University Hospital of the RWTH Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany.
authors: S
authors: S
authors: Metzelder
authors: M
authors: M
authors: Coburn
authors: M
authors: M
authors: Fries
authors: M
authors: M
authors: Reinges
authors: S
authors: S
authors: Reich
authors: R
authors: R
authors: Rossaint
authors: G
authors: G
authors: Marx
authors: S
authors: S
authors: Rex
mesh_terms: D000328:Adult; D000465:Algorithms; D002302:Cardiac Output / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D009638:Norepinephrine / Q000494:pharmacology / Q000627:therapeutic use; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D012984:Software; D013345:Subarachnoid Hemorrhage / Q000150:complications; D013815:Thermodilution; D014655:Vascular Resistance / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology* / Q000627:therapeutic use; D020301:Vasospasm, Intracranial / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D055815:Young Adult
chemical_list: D014662:Vasoconstrictor Agents; D009638:Norepinephrine