Comparison of calibrated and uncalibrated arterial pressure-based cardiac output monitors
during orthotopic liver transplantation
Vladimir Krejci, Andrea Vannucci, Alhan Abbas, William Chapman, Ivan M. Kangrga
Liver Transplantation 2010 16(6):773-782.
Purpose/Hypothesis
To compare the performance of two currently available arterial pulse waveform analysis based cardiac
output (CO) monitors with thermodilution (TD) cardiac output during liver transplantation and to
determine if these monitors would be an acceptable substitute for TDCO during liver transplantation.
The two monitors compared were the LiDCO plus monitor which uses pulse waveform analysis after a
lithium dilution calibration and the FloTrac-Vigileo which does not require calibration.
Approach/Methods/ Analysis (Study Design)
Simultaneous CO measurements were made at 6 predetermined times (surgical events) by all 3
methods in 20 adult patients undergoing liver transplantation. TDCO was conventionally measured by
intermittent bolus injection using a pulmonary artery catheter, LiDCO and FloTrac-Vigielo
measurements were made using simultaneous data from a single radial arterial cannula. LiDCO
calibration was performed prior to induction. Pulse waveform CO was compared to TDCO by BlandAltman analyses (bias, limits of agreement and percentage error), concordance and relative changes.
.
Findings
Both pulse waveform techniques were determined to be unacceptable substitutes for TDCO. Both
tended to underestimate CO, had large limits of agreement, unacceptable error percentages (overall
75% for LiDCO and 68% for FloTrac-Vigielo, accepted limit 30%) and showed a worsening of bias with
time. Both also demonstrated a second order inverse relationship between bias and SVR. Correlation
with changes in consecutive CO measurements was poor for both methods. Concordance with “true”
changes in TDCO (>20%) was around 70% for both methods and predictive value for true changes
was poor for an increase in TDCO and fair for a decrease for both methods.
Shortcomings
On the whole this is a well conducted comparison of the pulse waveform analysis methods to the “gold
standard” TDCO. A radial artery catheter was used for the pulse waveform source, a more central
arterial line (eg femoral) may have performed better. In regards to LiDCO the calibration was
performed pre-induction, a post-induction calibration could have been performed and, given that the
mean surgical time was in excess of 8 hours recalibration, as has been suggested for ICU patients,
could have been considered.
Conclusion/Lessons
Neither of the pulse waveform analysis methods of CO measurement studies (LiDCO and FlotracVigileo) are currently a satisfactory substitute for TDCO during liver transplantation. Clinicians wishing
to measure CO should continue to place pulmonary artery catheters.
For those seeking alternatives the role of transesophageal echocardiography in monitoring cardiac
performance during liver transplantation merits consideration and further formal investigation.
James Y. Findlay, MB, ChB.