The importance of anesthesia as a significant variable is often underestimated in the evaluation of the results of hemodynamic studies. Especially in the study of shock, innumerable experiments have been performed on anesthetized dogs without consideration of the effect of the anesthetic agent, usually pentobarbital sodium, on the results.
To a large extent, this oversight has been unavoidable. Previously, we have not had a reliable method of comparing the microcirculatory flow changes in shock in the anesthetized and nonanesthetized animal so the specific effects of anesthetic agents could be determined.
The tissue-blood radioactive potassium (42K) uptake ratio comparison technique used in this study measures relative capillary blood flow and avoids the variables introduced by operative manipulation.1 Since it can be used with or without anesthesia, it is an ideal method for determining the effects of anesthesia on changes in capillary blood flow.
Thirty immature (age 6 to