Spread of epidural anesthesia and the lateral position.

The effects of the lateral position on onset, spread after 15 minutes, maximum spread, and duration of epidural anesthesia were measured in two groups of patients when different volumes in lidocaine 2% and epinephrine (20 and 15 ml) were injected using a standardizing technique; the patient was kept in the lateral position for 30 to 35 minutes after the injection. Anesthesia on the dependent side appeared 1.60 and 1.35 minutes earlier than in the nondependent side, spread 2.5 and 1.8 dermatomes higher 15 minutes after injection, and had maximum levels 2 and 1.8 spinal segments higher with 20 ml and 15 ml, respectively. Anesthesia lasted 20 minutes longer on the dependent side with both volumes of lidocaine. The results indicate that although the lateral position is associated with statistically significant differences in onset, spread, and duration of anesthesia on the dependent side compared to the upper side, these differences are of only minor clinical significance.