To the Editor:--Goertz et al. described the effects of hypertonic saline/6% hetastarch on left ventricular contractility. A number of years ago, we performed a study examining the hemodynamic response to 25% mannitol (a hypertonic solution) in patients before and during cardiac bypass. We found a 23+/-6% (SE) decrease in systemic arterial pressure with a 38+/-7% (SE) reduction in systemic vascular resistance in prebypass patients. During cardiopulmonary bypass, patients experienced a 30+/-5% to a 40+/-3% (SE) decrease in mean systemic pressure depending on dose and rate of mannitol administration. We also found that the patients not on bypass were able to compensate for the decrease in peripheral resistance by increasing cardiac output by approximately 0.8 l/min. These changes, however, were short-lived, and all hemodynamic parameters returned to baseline within a matter of several minutes.
We also performed radiolabeled microsphere studies and dose-response studies in rabbits, examining hypertonic glucose and hypertonic mannitol. We found that rate and dose were important factors influencing change in systemic vascular resistance and in systemic arterial pressure, i.e., the faster the rate of administration and the greater the osmotic load, the greater the hemodynamic effect. The vascular bed primarily responsive to this hypertonic load was in muscle tissue. One wonders how long the hypotension lasted in the patients studied by Goertz et al., whether this was an effect that was sustained for more than a transient period (as we observed with 25% mannitol), and whether the phenomena might have been caused by vasodilation of the vascular supply to muscle tissue, resulting in a reflex rather than a direct cardiac effect.
Charles J. Cote, M.D., Professor of Anesthesia and Pediatrics, Northwestern University Medical School, Vice Chairman, Director of Research, Department of Pediatric Anesthesia, Children's Memorial Hospital, 2300 Childrens Plaza, Chicago, Illinois 60614.