EVALUATION OF CONTINUOUS THERMODILUTION METHOD FOR CARDIAC OUTPUT MEASUREMENT
Abstract
Background. Continuous monitoring of haemodynamic variables is often necessary for detection of rapid changes in critically ill patients. In our patients recently introduced continuous thermodilution technique (CTD) for cardiac output measurement was compared to bolus thermodilution technique (BTD) which is a »golden standard« method for cardiac output (CO) measurement in intensive care medicine.
Methods. Ten critically ill patients were included in a retrospective observational study. Using CTD method cardiac output was measured continuously. BTD measurements using the same equipment were performed intermittently. The data obtained by BTD were compared to those obtained by CTD just before the BTD (CTD-before) and 2–3 minutes after the BTD (CTD-after). The CO values were divided into three groups: all CO values, CO > 4.5 L/min, CO < 4.5 L/min. The bias (mean difference between values obtained by two methods), standard deviation, 95% confidence limits and relative error were calculated and the linear regression analysis was performed. t-test for pared data was used to compare the biases for CTD-before and CTD-after for an individual group. The p value of less than 0.05 was considered statistically significant.
Results. A total of 60 data triplets were obtained. CTD-before ranged from 1.9 L/min to 12.6 L/min, CTD-after from 2.0 to 13.2 L/min and BTD from 1.9 to 12.0 L/min. For all CO values the bias for CTD-before was 0.13 ± 0.52 L/min (95% confidence limits 1.17–0.91 L/min), relative error was 3.52 ± 15.20%, linear regression equation was CTD-before = 0.96 × BTD + 0.01 and Pearson’s correlation coefficient was 0.95. The values for CTD-after were 0.08 ± 0.46 L/min (1.0–0.84 L/min), 2.22 ± 9.05%, CTD-after = 0.98 × BTD + 0.01 and 0.98 respectively. For all CO values there was no statistically significant difference between biases for CTD-before and CTD-after (p = 0,51). There was no statistically significant difference between biases for CTD-before and CTD-after for CO > 4.5 L/min and CO < 4.5 L/min (p = 0.90 and p = 0.24 respectively).
Conclusions. The continuous thermodilution cardiac output measurement shows clinically acceptable agreement with the bolus thermodilution technique in a wide range of CO values. There was no statistically significant difference between biases for CTD values before and after internal recalibration. CTD offers a reliable method of cardiac output monitoring in critically ill patients
Downloads
References
Forrester JS, Ganz W, Diamond G et al. Thermodilution cardiac output determination with a single flow-directed catheter. Am Heart J 1972; 83: 306–11.
Nelson LD. The new pulmonary arterial catheters. Critical Care Clinics 1996; 12: 795–818.
Boldt J, Menges T, Wollbrueck M et al. Is continuous cardiac output measurement using thermodilution reliable in the critically ill patient? Crit Care Med 1994; 12: 1913–8.
Yelderman ML. Continuous measurement of cardiac output with the use of stohastic system identification techniques. J Clin Monit 1990; 6: 322–32.
Yelderman ML, Quinn MD, McKown RC et al. Continuous thermodilution cardiac output measurement in sheep. J Thorac Cardiovasc Surg 1992; 104: 315–20.
Mihaljević T, Von Segesser LK, Toenz M et al. Continuous versus bolus thermodilution cardiac output measurements – A comparative study. Crit Care Med 1995; 23: 944–9.
Yelderman ML, Quinn MD, McKown RC et al. Continuous thermodilution cardiac output measurement in intensive care unit patients. J Cardiothorac Vasc Anesth 1992; 6: 270–4.
Boettiger BW, Soder M, Rauch H. Semi-continuous versus injectate cardiac output measurement in intensive care patients after cardiac surgery. Intensive Care Med 1996; 22: 312–18.
Haller M, Zoellner C, Briegel J, Forst H. Evaluation of a new continuous thermodilution cardiac output monitor in critically ill patients: A prospective criterion standard study. Crit Care Med 1995; 5: 860–6.
Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1: 307–10.
Elkayam U, Berkley R, Stanley et al. Cardiac output by thermodilution technique: Effects of injectate volumen and temperature on the accuracy and reproducibility in the critically ill patients. Chest 1983; 34: 418–22.
Renner RE, Morton MJ, Sakuma GJ. Indicator, amount, temperature, and intrinsic output affect thermodilution cardiac output accuracy and reproducibility. Crit Care Med 1993; 21: 586–97.
Daper A, Parqui JN, Preis JC. Timing of cardiac output measurements during mechanical ventilation. Acute Care 1986; 12: 113–6.
Snyder JV, Powner DJ. Effects of mechanical ventilation on the measurement of cardiac output by thermodilution. Crit Care Med 1982; 10: 677–82.
Jansen JR, Vesprille A. Improvement of cardiac output estimation by thermodilution method during mechanical ventilation. Intensive Care Med 1986; 12: 71–9.
Sasse SA, Chen PA, Berry RB et al. Variability of cardiac output over time in medical intensive care unit. Crit Care Med 1994; 22: 225–32.
Dobb GJ, Donavan KD. Non-invasive methods of measuring cardiac output. Intensive Care Med 1987; 13: 304–9.
The Author transfers to the Publisher (Zdravniški vestnik/Slovenian Medical Journal) all economic copyrights following form Article 22 of the Slovene Copyright and Related Rights Act (ZASP), including the right of reproduction, the right of distribution, the rental right, the right of public performance, the right of public transmission, the right of public communication by means of phonograms and videograms, the right of public presentation, the right of broadcasting, the right of rebroadcasting, the right of secondary broadcasting, the right of communication to the public, the right of transformation, the right of audiovisual adaptation and all other rights of the author according to ZASP.
The aforementioned rights are transferred non-exclusively, for an unlimited number of editions, for the term of the statutory
The Author can make use of his work himself or transfer subjective rights to others only after 3 months from date of first publishing in the journal Zdravniški vestnik/Slovenian Medical Journal.
The Publisher (Zdravniški vestnik/Slovenian Medical Journal) has the right to transfer the rights, acquired parties without explicit consent of the Author.
The Author consents that the Article be published under the Creative Commons BY-NC 4.0 (attribution-non-commercial) or comparable licence.