Baricity refers to the

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

of a substance compared to the density of human

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

. Baricity is used in

anesthesia Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), ...

to determine the manner in which a particular drug will spread in the

intrathecal Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anesthesia, chemotherapy, or pain man ...

space.

Description

Solutions that have a baricity approaching 1.000 are referred to as isobaric, as the density of the cerebrospinal fluid is approximately 1.003+/- 0.003. Solutions with a baricity less than 0.999 are termed hypobaric, and are usually created by mixing the local anesthetic with distilled water. Hyperbaric solutions are created by mixing dextrose 5-8% with the desired local anesthetic. Hyperbaric solutions will flow in the direction of gravity and settle in the most dependent areas of the intrathecal space. Conversely, hypobaric mixtures will rise in relation to gravitational pull. These properties allow the anesthesia provider to preferentially control the spread of the block by choice of mixture and patient positioning.

References

Anesthesia {{treatment-stub