Solutions that have a<unk>  approaching 1.000 are referred to as isobaric, as the density of the cerebrospinal fluid is approximately 1.0003+/- 0.0003. Solutions with a<unk>  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.
Baricity
Pain out of proportion
Hyperintensity
Tenderness 
Lusitropy
Acelity
Weakness
Pain asymbolia