[Density, specific gravity and baricity of various spinal anesthetics and those of normal human cerebrospinal fluid in Japanese].

We measured the density and specific gravity at room (20 degrees C) and body (37 degrees C) temperatures of spinal anesthetic solutions, which have been commercially prepared in Japan. Solutions investigated were; (1) 0.4 % and 0.5 % tetracaine (T) in water, 0.5 % T in normal saline, 5 % glucose and 10 % glucose, (2) 0.3 % dibucaine in 5 % sodium chloride: (P), (3) 0.24 % dibucaine with 0.12 % tetracaine in 9.5 % glucose: (N); (4) 3 % lidocaine in 8.5 % glucose: (X); and (5) 0.5 % bupivacaine in water containing preservatives: (M). We also determined the density and specific gravity of normal human cerebrospinal fluid (CSF) in Japanese (n = 10) at 37 degrees C. Each local anesthetic solution was classified into hyperbaric, isobaric or hypobaric solution. Thirty seven centigrade 0.5 % T in normal saline and 37 degrees C 0.5 % M in water had the density comparable to 37 degrees C human CSF and were considered to be relatively isobaric solutions. Our data demonstrated that human CSF had various densities. Therefore, it is possible that these isobaric solutions would vary their pharmacodynamic profiles in intrathecal use according to individual CSF characteristics and temperature of the solution.