Spinal Anesthesia: Volume or Concentration—What Matters?

Abstract

A constant 70-mg dose of subarachnoid lidocaine produced the same pinprick level of analgesia, degree of motor block, and duration of spinal anesthesia in spite of being injected over an extremely broad range of concentrations and volumes. Despite the fact that all patients received the same dose of lidocaine, the CSF concentrations at 5, 10, and 15 minutes were different and directly related to the concentration of the solution injected. at 20 minutes, the CSF concentrations were similar in all groups. These results indicate a relatively uniform distribution of lidocaine in the CSF for all solutions tested.