Interaction between baricity (glucose concentration) and other factors influencing intrathecal drug spread

The effects of intrathecal injection of 0.5% bupivacaine in solutions containing various concentrations of glucose have been studied in four groups of 20 patients. When solutions containing 0.8% glucose were injected at the L3-4 interspace the median maximum extent of block was higher, and the range of blocks wider, with the 8% solutions. All patients receiving 0.8% glucose had blocks between the T5 and T10 dermatomes, confirming previous work on the benefits of this concentration of glucose. In the two other groups 0.5% bupivacaine containing 0 or 0.8% glucose was injected at the L2-3 interspace. In both groups of patients a wider range of blocks, with a median maximum extent that was higher, was produced. These results demonstrate how glucose concentration may be used to influence the spread of intrathecal solutions and how other factors can obscure the effect of glucose concentration.