Cerebrospinal Fluid Density Influences Extent of Plain Bupivacaine Spinal Anesthesia
"The relation between a high CSF density and a high upper sensory block level allows a better understanding of the unpredictability of extent of plain bupivacaine spinal anesthesia. However, this finding is not very useful clinically because, in everyday practice, we cannot measure CSF density in all patients.
Another finding of the current study that could be clinically relevant is the fact that upper sensory block extent varied by 13 segments (T1 –L1), as reported in table 4, with unnecessary high median values (T5) for lower limb surgery. Figures 2 and 3 indicate that higher sensory block levels are associated with shorter duration of sensory block and greater hemodynamic consequences.
Because the spread of plain bupivacaine spinal anesthesia remains difficult to predict, we feel that for lower limb surgery in supine position, plain local anesthetic solutions should be avoided in favor of hyperbaric ones associated with a 30° elevated-torso position of patients during surgery. Indeed, we previously demonstrated that, during hyperbaric bupivacaine spinal anesthesia, maximal sensory level is lower, duration of sensory block is longer, and hemodynamics much better preserved in patients maintained in a 30° torso-elevated position compared with those maintained in a horizontal position. 2