Density of normal human cerebrospinal fluid and tetracaine solutions

Density and specific gravity (SG) were determined at two or more temperatures between 23 and 37 C for 15 samples of normal human cerebrospinal fluid (CSF) and CSF mixed with tetracaine, and for tetracaine solutions commonly used for spinal anesthesia. Density was determined from measured weight and volume, and SG was calculated using the density of water at the same temperature. With 95% confidence limits, SG of normal human CSF at 37 C ranges from 1.0063 to 1.0075, less variation than previously reported. Changes in temperature altered the densities of dextrose, tetracaine, and CSF, alone or in combination, in a parallel manner, but SG remained constant for each solution over the observed temperature range.