Risks of dural puncture associated with thoracic epidurals

Abstract

spinal anesthesia. He had previously been treated for multiple myeloma, and three weeks prior to surgery, he developed a herpes zoster lesion at his left T 4 dermatome. Medications at the time of admission included gabapentin 800 mg tid, and a transdermal fentanyl patch (25 µg·hr -1 ). Preoperatively, the subjective pain rating related to the zoster lesion was 4/10 on a verbal ten-point scale. A spinal block was performed at the L 3 -L 4 interspace using isobaric bupivacaine 15 mg and fentanyl 15 µg. The patient was transferred thereafter from a sitting to a supine position. A propofol infusion was started at 100 µg·kgAfter verifying an absent response to skin pinching, the surgeon incised the skin overlying the left iliac crest (T 12 -L 1 dermatome). The patient immediately complained of a burning type pain which he clearly localized to the left T 4 dermatome, and quantified at 7/10. He reported having no pain at the level of the incision. The patient underwent general anesthesia with a laryngeal mask airway. Anesthetic maintenance was provided with 1% sevoflurane and 50% nitrous oxide for surgery which proceeded uneventfully and lasted 120 min.Following emergence, the patient had complete motor block of both legs, and residual sensory levels at T 9 and T 11, as evaluated by both ice and pinprick. He rated his herpetic pain at 4/10; and this decreased to 1/10 in the postanesthesia care unit where he denied any pain at the surgical site. After complete regression of the spinal block, the patient was treated with sc hydromorphone and resumed gabapentin and the fentanyl patch. There was no further exacerbation of his herpalgia during the hospital stay.This case demonstrates a clinical scenario where a surgical stimulus in an anesthetized dermatome evoked a referred sensory response in a proximal non-anesthetized dermatome. This phenomenon is in accordance with the demonstration by Zaidi et al. that an adequate surgical block does not abolish all afferent sensory pathways.2 Pain is the most common complaint of patients suffering from herpes zoster, and these patients may experience pain in response to nonnoxious stimuli, where even the slightest pressure may elicit pain. We hypothesize referred pain/ hyperalgesia from the surgical incision to the inflamed/infected neural tissue (T 4 ) was probably elicited by a reflex arc activation similar to that described in referred muscle pain resulting from algogenic conditions in viscera or other deep somatic structures. Whether or not this phenomenon could have been prevented by preoperative application of lidocaine patches, a higher spinal block, or a simple intercostal or paravertebral block at the left T 4 level, remains speculative.