Intrathecal bupivacaine and morphine toxicity leading to transient hypotension and delayed status epilepticus

Abstract

Background: Local anesthetic systemic toxicity characteristically occurs after inadvertent intravascular injection of local anesthetics; however, it is unclear if similar symptoms arise after intrathecal adminstration. Intrathecal use of local anesthetics for chronic pain is increasing and carries a potential risk of toxicity. Experience with the presenting symptoms and appropriate treatment for intrathecal local anesthetic toxicity is limited.

Case study: A 74-year-old woman with an intrathecal bupivacaine/morphine pump developed lower extremity sensory neuropathy followed by obtundation, hypotension, and lower extremity flaccidity after an intrathecal pump refill. Her condition evolved to status epilepticus (SE) refractory to standard treatment. Intravenous fat emulsion (IFE) was administered, but was not immediately effective thus necessitating phenobarbital loading and propofol infusion. Despite significant bupivacaine neurotoxicity, no cardiotoxicity developed.

Discussion: The patient developed intrathecal local anesthetic and opioid toxicity after a malfunction of her intrathecal pump during a refill. We hypothesize that no cardiotoxicity developed secondary to sequestration of bupivacaine within the central nervous system. Likewise, poor CNS penetration of intravenous lipid emulsion may have negated or delayed any antidotal effect.

Conclusion: We present a case of intrathecal toxicity leading to prolonged spinal anesthesia, progressive encephalopathy, and SE refractory to intravenous lipid emulsion. Management of SE with benzodiazepines and barbiturates may be more effective than lipids in cases of toxicity from intrathecal administration of bupivacaine.

Keywords: Bupivacaine; Intrathecal drug delivery pump; Intravenous fat emulsion; Morphine.