S. Metzelder

Performance of cardiac output measurement derived from arterial pressure waveform analysis in patients requiring high-dose vasopressor therapy

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.

The influence of chest opening and closure on left ventricular stroke volume variation (SVV) and pulse pressure variation (PPV): O-19

dynamic variables between two groups during all study period. Discussion: RVEF significantly decreased during distal anastomosis of RCA performed without intra-coronary shunt in patients with severe proximal RCA stenosis but not in patients with moderate RCA stenosis. Although there was no significant difference in preoperative RVEF between the two groups, already depressed intrinsic RV function due to severe RCA coronary stenosis is likely to affect the result of this study. References: 1 Schirmer U, Calzia E, Lindner KH, et al. Right ventricular function after coronary artery bypass grafting in patients with and without revascularization of right coronary artery. J Cardiothorac Vasc Anesth 1995; 9: 659–664. 2 Niimi Y, Hiki M, Ishiguro Y, et al. Determination of right ventricular function by transesophageal echocardiography: impact of proximal right coronary artery stenosis. J Clinical Anesth 2004; 16: 104–110.