LETTERS TO THE EDITOR: Letters & Announcements
We would like to thank Chamorro et al. for their important contribution. The pulmonary vascular resistance (PVR), not expressed in our work, is now presented in Table 1. We observed no significant change in PVR. In addition, there is not a significant difference between survivors and nonsurvivors nor is there one between patients in septic and patients in postcardiotomy shock.
From a physiological standpoint, the observed decrease in cardiac index (CI) of approximately 1 L · min−1 · m2 should not significantly contribute to the observed reduction in mean pulmonary arterial pressure (MPAP). In humans the pulmonary arterial system is very compliant and blood flow through the lungs may vary substantially before MPAP changes. Even in critically ill patients, small changes in cardiac output similar to that observed during this study usually do not affect MPAP. Nevertheless, a significant reduction in mean pulmonary arterial pressure should be accompanied by a decrease in right ventricular afterload.
The true mechanism of the observed decrease in MPAP in our patients remains to be resolved. However, we speculate that the significant reduction in norepinephrine requirements during vasopressin administration plays a major role.
W. R. Hasibeder, MD
M. W. Dünser, MD
A. J. Mayr, MD