Clinical heterogeneity in patients, interventions and outcomes in perioperative goal-directed therapy trials is too large to perform meta-analysis on all trials. Future trials and meta-analyses highly depend on universally agreed definitions on aspects beyond type of surgery of the complex intervention and its evaluation.
Minimally and noninvasive monitoring devices may not be sufficiently accurate to replace (trans)pulmonary thermodilution in estimating cardiac output. The current paradigm shift to explore trending ability rather than investigating agreement of absolute values alone is to be applauded. Future research should focus on the effectiveness of these devices in the context of (functional) haemodynamic monitoring before adoption into clinical practice can be recommended.
Background
Cardiac output measurements may inform diagnosis and provide guidance of therapeutic interventions in patients with hemodynamic instability. The FloTrac™ algorithm uses uncalibrated arterial pressure waveform analysis to estimate cardiac output. Recently, a new version of the algorithm has been developed. The aim was to assess the agreement between FloTrac™ and routinely performed cardiac output measurements obtained by critical care ultrasonography in patients with circulatory shock.
Methods
A prospective observational study was performed in a tertiary hospital from June 2016 to January 2017. Adult critically ill patients with circulatory shock were eligible for inclusion. Cardiac output was measured simultaneously using FloTrac™ with a fourth-generation algorithm (CO
AP
) and critical care ultrasonography (CO
CCUS
). The strength of linear correlation of both methods was determined by the Pearson coefficient. Bland-Altman plot and four-quadrant plot were used to track agreement and trending ability.
Result
Eighty-nine paired cardiac output measurements were performed in 17 patients during their first 24 h of admittance. CO
AP
and CO
CCUS
had strong positive linear correlation (
r
2
= 0.60,
p
< 0.001). Bias of CO
AP
and CO
CCUS
was 0.2 L min
−1
(95% CI − 0.2 to 0.6) with limits of agreement of − 3.6 L min
−1
(95% CI − 4.3 to − 2.9) to 4.0 L min
−1
(95% CI 3.3 to 4.7). The percentage error was 65.6% (95% CI 53.2 to 77.3). Concordance rate was 64.4%.
Conclusions
In critically ill patients with circulatory shock, there was disagreement and clinically unacceptable trending ability between values of cardiac output obtained by uncalibrated arterial pressure waveform analysis and critical care ultrasonography.
Trial registration
Clinicaltrials.gov,
NCT02912624
, registered on September 23, 2016
Electronic supplementary material
The online version of this article (10.1186/s40560-019-0373-5) contains supplementary material, which is available to authorized users.
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