Mg. Richardson et Rn. Wissler, DENSITIES OF DEXTROSE-FREE INTRATHECAL LOCAL-ANESTHETICS, OPIOIDS, AND COMBINATIONS MEASURED AT 37-DEGREES-C, Anesthesia and analgesia, 84(1), 1997, pp. 95-99
Dextrose-free anesthetic medications are commonly used to provide suba
rachnoid anesthesia and analgesia. Hypobaricity has been proposed as a
mechanism to explain postural effects on the extent of sensory block
produced by these drugs. Densities of dextrose-free solutions of local
anesthetics and opioids, and commonly used anesthetic/opioid mixtures
were determined at 37.00 degrees C for comparison with the density of
human cerebrospinal fluid (CSF). Measurements accurate to 0.00001 g/m
L were performed using a mechanical oscillation resonance frequency de
nsity meter. All undiluted solutions tested are hypobaric relative to
human lumbar CSF with the exception of lidocaine 1.5% and 2.0% with ep
inephrine 1:200,000. All mixtures of local anesthetics and opioids tes
ted are hypobaric. We observed good agreement between measured densiti
es and calculated weighted average densities of anesthetic mixtures. W
hile the influence of baricity on the clinical effects of dextrose-fre
e intrathecal anesthetics remains controversial, attempts to attribute
postural effects to the baricity of these drugs requires establishmen
t of accurate density values. These density data may facilitate elucid
ation of the mechanisms underlying the behavior of dextrose-free intra
thecal anesthetics.