Reply to the Editor

Abstract

We thank Benallal for his comments on our article and appreciate his remarks. Our study was specifically designed to assess the importance of measured oxygen consumption (VO2) in the preoperative diagnostic hemodynamic evaluation during cardiac catheterization and to assess whether published formulas allow a reliable calculation of VO2. We did not intend to develop a new formula to assume VO2. Our results emphasize that both the Krovetz-Goldbloom formula,1Krovetz L.J. Goldbloom S. Normal standards for cardiovascular data. I. Examination of the validity of cardiac index.Johns Hopkins Med J. 1972; 130: 174-186PubMed Google Scholar which had been used to this point in our institution, and the more commonly used formula published by LaFarge and Miettinen2LaFarge C.G. Miettinen O.S. The estimation of oxygen consumption.Cardiovasc Res. 1970; 4: 23-30Crossref PubMed Scopus (319) Google Scholar are not feasible in all patients to assume VO2 and thereby calculate cardiac output by the Fick principle. Li and colleagues3Li J. Bush A. Schulze-Neick I. Penny D.J. Redington A.N. Shekerdemian L.S. Measured versus estimated oxygen consumption in ventilated patients with congenital heart disease the validity of predictive equations.Crit Care Med. 2003; 31: 1235-1240Crossref PubMed Scopus (58) Google Scholar presented the important conclusion that other predictive equations published by Lundell and associates,4Lundell B.P.W. Casas M.L. Wallgren C.G. Oxygen consumption in infants and children during heart catheterization.Pediatr Cardiol. 1996; 17: 207-213Crossref PubMed Scopus (42) Google Scholar Wessel and colleagues,5Wessel H.U. Rorem D. Muster A.J. Acevedo R.E. Paul M.H. Continuous determination of oxygen uptake in sedated infants and children during cardiac catheterization.Am J Cardiol. 1969; 24: 376-385Abstract Full Text PDF PubMed Scopus (29) Google Scholar and Lindahl6Lindahl S.G.E. Oxygen consumption and carbon dioxide elimination in infants and children during anaesthesia and surgery.Br J Anaesth. 1989; 62: 70-76Crossref PubMed Scopus (55) Google Scholar also do not accurately estimate VO2. All these formulas were developed to offer a suitable and reliable method to assume VO2 in order to simplify the calculation of hemodynamic parameters. However, these formulas cannot be used in all patients and settings. As Benallal pointed out, these formulas include coefficients depending on characteristics of the population investigated in these studies. The difference between measured and assumed VO2 might be due to a population difference. In addition, it is also influenced essentially by other conditions such as the mode of general anesthesia and relaxation used in different institutions. It is difficult to identify feasible coefficients to develop a formula fitting to all conditions of hemodynamic evaluation during cardiac catheterization. Moreover, we are convinced that our population of 143 patients is too small to identify and validate suitable coefficients for a new formula. LaFarge and Miettinen derived their most commonly used formulas from a multivariate analysis of covariance applied to data on a series of 879 patients. A new modeling for each populationThe Journal of Thoracic and Cardiovascular SurgeryVol. 131Issue 2PreviewI read with great interest the recently published study by Fakler and associates1 in the August 2005 issue of the Journal. They found, in their investigation, a poor agreement between the measured oxygen consumption (VO2) and the VO2 estimated using the formulas of Krovetz and Goldbloom2 and LaFarge and Miettinen.3 According to the Krovetz-Goldbloom formula, the mean difference was −53 mL/min/m2 and the limits of agreement were −95.5 and −11.1 mL/min/m2 for the lower and upper limits, respectively. Full-Text PDF