2024 FSA Podium and Poster Abstracts

P077: DELAYED ONSET OF SPINAL ANESTHESIA IN A CHRONIC OPIOID USER UNDERGOING CAESARIAN SECTION
Michael Gross, DO; Imani Thornton; HCA Florida Westside Hospital

Introduction/Background: Delayed onset of spinal anesthesia can pose challenges during caesarean section, particularly in patients with a history of chronic opioid use. We present a case of delayed onset of spinal anesthesia in a patient with chronic opioid use undergoing caesarean section, highlighting the clinical implications and management strategies.

Methods: A 37-year-old female at 39 weeks and 1-day gestation presented for elective primary caesarian section. She had a history of bipolar disorder, seizure disorder, chronic lumbar and cervical pain secondary to a previous motor vehicle accident, and a history of chronic opioid dependency. She endorsed former intravenous heroin use and was actively taking buprenorphine 8mg sublingual once daily. Anesthetic management included a spinal block with 1.7 ml of hyperbaric bupivacaine, 25mcg of fentanyl, and 0.3mg of preservative-free morphine. Slightly higher dosing for all three medications was given compared to the average institutional standard dosing.

Results: The onset of spinal anesthesia was significantly delayed, requiring a prolonged waiting period for adequate sensory and motor block, while the onset of hypotension was prompt. It took nearly 25 minutes to reach a satisfactory blockade to the T4 level after the spinal was performed. The surgery was completed without complications or patient discomfort. Postoperatively, the patient reported significant pain which was managed by the pain management service, but she otherwise had an uneventful recovery.

Discussion/Conclusion: Delayed onset of spinal anesthesia in chronic opioid users can result from neurophysiological adaptations and pharmacokinetic interactions in the central nervous system.(1) Previous studies have suggested chronic opioid users display a delayed onset and shorter duration of action of neuraxial blockade in non-obstetric patients.(2-5) In parturient patients, this may have greater implications. Delayed onset may lead to the misconception of a failed spinal and conversion to general anesthesia. In reality, additional time may be needed for the block to rise to adequate level. When providing anesthesia for chronic opioid users undergoing caesarian section, it is important to understand the possibility of delayed onset of spinal while also considering the patient’s other comorbidities, preferences, and time-sensitivity of the surgery.

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