Extent of anesthesia and hemodynamic effects after subarachnoid administration of bupivacaine with epinephrine

It has been suggested that the amount of local anesthetic injected into the subarachnoid space is more important than the volume or concentration that is used in determining the extent of anesthesia. However, this conclusion was based on studies using small volumes of local anesthetic (e.g., 1-4 ml). We have used larger volumes of local anesthetic (10 ml) for subarachnoid anesthesia, with good analgesia and without complications. We have now evaluated the effect of using widely disparate volumes (2.5 vs 10 ml) and concentrations (0.5% vs 0.125%) of bupivacaine while maintaining a cosntant dose (12.5 mg) on the extent of sensory anesthesia and the resultant hemodynamic changes.