(Anesth Analg. 2018;127:171–178) A major limitation of spinal anesthesia is that the duration of the anesthetic may not be adequate in the event of a prolonged surgery. Bupivacaine without an adjuvant provides ∼120 minutes of surgical anesthesia. Epinephrine added to lidocaine or tetracaine can increase the block’s duration as much as 2-fold. However, less is known about the prolongation of spinal block when epinephrine is added to bupivacaine. In the present study, the authors evaluated whether the addition of subarachnoid epinephrine to bupivacaine and morphine would prolong the duration of surgical anesthesia for repeat cesarean delivery as measured by the time to T-10 regression or activation of the epidural for patient comfort.

Abstract. Spinal anesthesia or regional anesthesia is a potent anesthetic procedure. Additional modalities have been sought to increase the duration of block in spinal anesthesia. Ketamine is an N-methyl-D-aspartate (NMDA) receptor blocker that has an anesthetic effect when injected intrathecally and has a synergic effect with bupivacaine. Ketamine also has potent analgesic properties. The present study investigated the effect of intrathecally administered ketamine on spinal anesthesia with levobupivacaine or ropivacaine. Sprague-Dawley rats at post-natal day 21 were exposed to spinal anesthesia with 0.5% levobupivacaine or 0.5% ropivacaine. Separate groups of rats were treated with intrathecal ketamine at a 5 or 10 mg/kg bodyweight dose along with ropivacaine or levobupivacaine. The thermal and mechanical withdrawal latencies of the animals were determined using hot plate and von Frey filaments, respectively. A rotarod apparatus was employed to assess the capacity of the rats to rotate the spindle at 24 h following anesthesia. The gait of the rat pups was also assessed. Intrathecal administration of ketamine resulted in dense blocks and extended the duration of spinal blocks as evidenced by thermal latencies and responses to von Frey filaments. The latency to fall was shorter in rats exposed to ketamine along with ropivacaine or levobupivacaine spinal anesthesia. The gait parameters were also more disturbed upon ketamine administration. In conclusion, ketamine administration with ropivacaine or levobupivacaine increased the intensity and duration of spinal blockade, thereby increasing the anesthetic effects.