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ORIGINAL ARTICLE
Arterial pressure waveform analysis versus
thermodilution cardiac output measurement during
open abdominal aortic aneurysm repair
A prospective, observational study
Leonard J. Montenij, Wolfgang F. Buhre, Steven A. de Jong, Jeroen H. Harms,
Joost A. van Herwaarden, Cas L.J.J. Kruitwagen and Eric E.C. de Waal
BACKGROUND Arterial pressure waveform analysis
enables continuous, minimally invasive measurement of car-
diac output. Haemodynamic instability compromises the
reliability of the technique and a means of maintaining
accurate measurement in this circumstance would be useful.
OBJECTIVES To investigate the accuracy, precision and
trending ability of arterial pressure waveform cardiac output
obtained with FloTrac/Vigileo, versus pulmonary artery ther-
modilution in patients undergoing elective open abdominal
aortic aneurysm repair.
DESIGN A prospective, observational study.
SETTING Operating room in a university hospital.
PATIENTS Twenty-two patients scheduled for elective, open
abdominal aortic aneurysm repair.
MAIN OUTCOME MEASURES Bias, limits of agreement
and mean error as determined with Bland–Altman analysis
between arterial waveform and thermodilution cardiac output
assessment at four time points: after induction of anaesthesia
(t
1
); after aortic cross-clamping (t
2
); after clamp release (t
3
);
and after skin closure (t
4
). Trending ability from t
1
to t
2
, t
2
to t
3
and t
3
to t
4
, determined with four-quadrant and polar plot
methodology. Clinically acceptable boundaries were defined
in advance.
RESULTS Bland–Altman analysis revealed a bias of
0.54 l min
1
(thermodilution minus arterial waveform cardiac
output) for pooled data, and 0.51 (t
1
), 0.42 (t
2
), 0.98 (t
3
)
and 0.98 (t
4
) l min
1
at the different time points. Limits of
agreement (LOA) were [ – 3.0 to 4.0] (pooled), [2.0 to 3.0]
(t
1
), [3.1 to 2.3] (t
2
), [2.5 to 4.4] (t
3
) and [1.7 to 3.7]
(t
4
) l min
1
, resulting in mean errors of 58% (pooled), 45%
(t
1
), 53% (t
2
), 52% (t
3
) and 41% (t
4
). Four-quadrant con-
cordance was 65%. Polar plot analysis resulted in an angular
bias of 128, with radial LOA of 608 to 368.
CONCLUSION Bias between arterial waveform and thermo-
dilution cardiac output was within a predefined acceptable
range, but the mean error was above the accepted range of
30%. Trending ability was poor. Arterial waveform and ther-
modilution cardiac outputs are, therefore, not interchange-
able in patients undergoing open abdominal aortic aneurysm
repair.
Published online xx month 2014
Introduction
Arterial pressure waveform analysis (APWA) is increas-
ingly being used for measurement of cardiac output (CO)
in the operating room and the ICU.
1
Compared with
other CO monitoring techniques, APWA has the advan-
tages of being minimally invasive, continuous and easy to
use in daily practice.
1–3
In addition, it provides dynamic
preload assessment, which may help guide fluid
therapy.
3–5
APWA is potentially valuable for the haemo-
dynamic management of high-risk surgical patients.
1,3
The FloTrac/Vigileo system uses APWA to provide CO
measurement without the need for external calibration.
6
Eur J Anaesthesiol 2014; 31:1–7
From the Department of Anaesthesiology (LJM, SADJ, JHH, ECDW), Department of Vascular Surgery (JAVH), Julius Centre for Biostatistics, University Medical Centre
Utrecht, Utrecht (CLK), and Department of Anaesthesia and Pain Therapy, Maastricht University Medical Centre, Maastricht, The Netherlands (WFB)
Correspondence to Leonard J. Montenij, PhD, Department of Anaesthesiology, University Medical Centre Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The
Netherlands
Tel: +31 88 75 61157; e-mail: l.j.montenij@umcutrecht.nl
0265-0215 ß 2014 Copyright European Society of Anaesthesiology DOI:10.1097/EJA.0000000000000160