To the Editor:
I agree with Riley et al.'s results  regarding better efficacy of 6% hetastarch in comparison to lactated Ringer's solution for preventing hypotension after spinal anesthesia. However, they have failed to mention the time period during which they gave these two solutions to patients preoperatively. The intravascular half-life of crystalloids is shorter than that of colloids. Slow administration of lactated Ringer's solution may result in its rapid diffusion into extravascular space before spinal anesthesia is produced. The 6% hetastarch, with a longer intravascular half-life, may not be affected as much by slower administration. It is not only the type of solution administered that matters but also the duration of the administration as well as the time elapsed between fluid administration and onset of spinal anesthesia.
G. D. Puri, MD, PhD
Department of Anaesthesiology and Intensive Care
Postgraduate Institute of Medical Education and Research
Chandigarh 160012, India
1. Riley ET, Cohen SE, Rubenstein AJ, Flanagan B. Prevention of hypotension after spinal anesthesia for cesarean section: six percent hetastarch versus lactated Ringer's solution.