Background: Failure of neuraxial blocks following placement are generally attributed to technical difficulties, poor local anesthetic spread, or under dosing. We report the case of a patient that achieved a surgical block with intrathecal local anesthetic(LA) prior to cesarean delivery but required frequent re-dosing of LA through an insitu epidural catheter. We hypothesize this was due to LA resistance.
Case: A 17 year-old G1P0 at 40 weeks and 2 days with no significant PMH presented to L&D for induction of labor for postdates. An epidural was placed at L3/4, with good pain relief. The epidural was bloused for low pelvic pain/pressure when the patient was 10cm dilated, again with good relief. The patient was diagnosed with Stage 2 arrest after 2 hours of pushing and a cesarean section was scheduled. 15ml of 2% lidocaine with 1:200,000 epinephrine was administered in divided doses to achieve surgical anesthesia. After 10 minutes, the patient had a T8 block, with sparing over T12 dermatome and the decision was made to replace with a CSE.
An intrathecal dose of 6mg hyperbaric bupivacaine, 15mcg fentanyl and 150mcg morphine was administered and epidural placed at L3/4. A surgical block to the T-2 dermatome was achieved. The patient tolerated the low transverse cesarean section incision and uterine incision. However, 30 minutes after the spinal dose, at the initiation of hysterotomy repair, the patient experienced severe lower abdomen pain at the pfannenstiel incision described as “tearing”. The epidural was bolused with 10ml 2% lidocaine with epi in divided doses with good relief of pain.
On arrival to the PACU, 1 hour after initial spinal dose and 30 minutes after lidocaine bolus through epidural, the patient reported no pain but was noted to have 5/5 strength and intact sensation in bilateral lower extremities. Upon further questioning, she reported a history of repeated failure of local anesthetic injections at the dentist.
Discussion: There is little research into LA resistance or rapid metabolism. Individuals with Ehrlers Danlos have been known to have resistance to LA (1). A recent genetic variant in voltage gated NA channels was identified in a family experiencing resistance and rapid metabolism of LA (2). This patient experienced good relief with intrathecal and epidural dosing, but had ultrafast offset of anesthesia, possibly indicating a genetic variant in the NA channel or other etiology of LA resistance. Patients should be asked prior to administration of epidural or spinal anesthesia if they have experienced symptoms of resistance in the past. If so, placement of an epidural catheter may be advised for cesarean in case re-dosing is required.
References:
1. Arendt-Nielsen, L et al. Insufficient effect of local analgesics in Ehlers Danlos type III patients. Acta Anaesthesiol Scand. 1990;34(5):358-61
2. Clendenen, N et al. Whole-exome sequencing of a family with local anesthetic resistance. Minerva Anestesiologica. 2016;82(10):1089-97
