Median time from introducer insertion to intrathecal injection of drugs was no different in the single-shot spinal group vs the spinal-epidural group. (Image source: Thinkstock)

Median time from introducer insertion to intrathecal injection of drugs was no different in the single-shot spinal group vs the spinal-epidural group. (Image source: Thinkstock)

The management of morbidly obese patients is a recurring research theme.  From 2002 to 2012, the number of articles on morbid obesity increased almost 300%.  When managing a morbidly obese pregnant patient who is to undergo cesarean section, is a combined spinal-epidural technique any better than a single-shot spinal?  Certainly the epidural needle is larger and more rigid than a spinal needle, so the epidural needle is less likely to deviate.  However, there’s no evidence that onset of anesthesia is faster with either technique.

Dr. Peter H. Pan, Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, NC and colleagues randomized 44 parturients who were to undergo elective cesarean section to determine if onset time differed depending on which technique was utilized.  Their findings appeared in the article “A Randomized Controlled Comparison Between Combined Spinal-Epidural and Single-Shot Spinal Techniques in Morbidly Obese Parturients Undergoing Cesarean Delivery: Time for Initiation of Anesthesia” published in this month’s edition of Anesthesia & Analgesia.

The median time from insertion of the introducer to intrathecal injection of drugs was 210 seconds in the single-shot spinal group and 180 seconds in the spinal-epidural group, a trivial difference.  The total number of attempts for successful completion of the procedure averaged 5 in the single-shot spinal group and 3 in the spinal-epidural group, a significant difference.  The percent of patients whose procedure was completed within 10 minutes and patient self-rating of pain was no different between study groups.

The study was small. Based on a post-hoc analysis, over 1000 patients would need to be studied to detect a 30 second difference.  Though not specifically tested, use of an epidural with a spinal might help if a case lasted longer than expected or if a subarachnoid block was inadequate.  Future studies might focus on success within 10 minutes or the number of attempts needed to perform a successful block. Larger studies might examine how often the anesthesiologist converted to general anesthesia for unusually prolonged cases.