VOLUME 30, ISSUE 2

The scarcity of hyperbaric bupivacaine has forced many of us to change the way we approach how we care for our cesarean section patients. Most of our Texas Society of Anesthesiologists (TSA) members feel perfectly comfortable using hyperbaric bupivacaine for elective, urgent, and even emergent cesarean sections. The advantages of hyperbaric bupivacaine are numerous: it is approved by the Food and Drug Administration (FDA) for use in the intrathecal space, its hyperbaric baricity theoretically allows the physician anesthesiologist to adjust the level of the block with patient positioning, and physician anesthesiologists are familiar with its dosing.

My residents are always surprised to see the ominous “not for spinal anesthesia” warning on isobaric bupivacaine vials. They immediately think that the reason for this label is due to a preservative of some sort that does not make intrathecal injection safe. In reality, the reason for this label is that the Food and Drug Administration has not approved these particular drugs for use in the intrathecal space. Physician anesthesiologists have been openly questioning why these drugs have such limited FDA approved applications as far back as the 1990’s.¹ As licensed physicians, we are able to use these drugs in the intrathecal space as an off-label use.

The Society for Obstetric Anesthesia and Perinatology (SOAP) has issued guidelines on how to cope with the shortage of hyperbaric bupivacaine². In summary, they advocate conserving hyperbaric bupivacaine for high risk patients and/or emergent cesarean sections. For elective cesarean sections, SOAP recommends using 2.5 ml of isobaric bupivacaine 0.5% when opioids such as fentanyl and preservative free morphine are added to the spinal dose. When opioids are not added to the spinal mixture, SOAP recommends using 3.0 ml of isobaric bupivacaine 0.5%. Additionally, SOAP suggests asking the hospital pharmacy if they are able to separate the large volumes of isobaric bupivacaine vials into smaller aliquots to conserve supply.

Alternatively, one could take into account height and weight when deciding upon a dose of isobaric bupivacaine 0.5% for cesarean section. Harten and colleagues performed a prospective study in 2005 where patients received either a fixed dose (2.4 ml) of hyperbaric bupivacaine 0.5% with diamorphine 0.4 mg or a dose of hyperbaric bupivacaine 0.5% based on height and weight along with diamorphine 0.4 mg.³ Harten found that the analgesic outcomes were the same between the two groups with less hypotension in the group that had the dose based on height and weight.

A Cochrane systematic review examined the use of hyperbaric bupivacaine versus isobaric bupivacaine for elective cesarean sections⁴. There was no discernable difference in conversion to general anesthesia, need for supplemental analgesia, use of ephedrine, or incidence of nausea and vomiting for the two formulations. The time to surgical block was statistically faster in subjects receiving hyperbaric bupivacaine but only by about one minute. Unfortunately, most of the data was low quality and no definitive conclusions can be made.

In our practice at Scott & White Medical Center-Temple, we have restricted the use of hyperbaric bupivacaine to high risk patients and emergent cesarean sections where the obstetricians believe there is enough time for an experienced provider to attempt a regional technique. Additionally, we use a variation of the chart published by Harten to tailor our dose of isobaric bupivacaine 0.5% to the patient’s height and weight. We also use a combined spinal epidural technique so that we have the option to dose an epidural catheter with lidocaine 2% if the spinal dose of isobaric bupivacaine 0.5% fails; this is a new development and is in response to our experience of higher failure rates with spinal anesthetics when using the isobaric bupivacaine 0.5% formulation. We will continue this practice until the shortage of hyperbaric bupivacaine is resolved, which will likely be sometime in September. ²