///2009 Abstract Details
2009 Abstract Details2019-08-03T15:55:31-06:00

Unintentional Cannulation of the Subdural Space in a Laboring Parturient

Abstract Number: 110
Abstract Type: Case Report/Case Series

Jaffer M Odeh M.D.1 ; Sabri Barsoum M.D.2

Introduction: The spinal subdural space is a potential space between the dura and the arachnoid containing small amounts of serous fluid. Intentional cannulation of the subdural space is generally impossible; however, it is infrequently cannulated unintentionally in an attempt to cannulate the epidural space. If not using contrast imaging, it is difficult, if not impossible, to know that a catheter intended for the epidural space is in the subdural space until after administration of local anesthetic.

Case Report: A 19 year-old female, gravida 1 para 0, was admitted to labor and delivery for induction of labor. The patients pregnancy was complicated by pregnancy induced hypertension and intrauterine growth retardation. An epidural was attempted using a 17g Touhy needle in the L4-5 interspace. There was loss of resistance to saline and an epidural catheter was threaded. After negative aspiration, a test dose of 3mL 1.5% lidocaine with epinephrine 1:200,000 was administered, which was uneventful. The catheter was then bolused with 12mL 0.125% bupivicaine with fentanyl 2 mcg/mL. Approximately 20-30 seconds after the bolus, the patient began complaining of numbness in the hands and arms, followed by dyspnea, apnea, and then unconsciousness. Systolic blood pressure dropped from the 120s before the bolus to the 90s. A size 5 laryngeal mask airway was inserted and the patients ventilations were assisted. Ephedrine was given to treat hypotension. The patients oxygen saturation did not drop below 98%. Additionally, there was no fetal bradycardia or any other signs of fetal distress. The patients ventilations were assisted for 45 minutes before return of spontaneous ventilation and return of consciousness. The subdural catheter was then connected to a constant infusion of bupivicaine 0.0625% with fentanyl 2 mcg/mL, which provided adequate labor analgesia. The catheter was removed after delivery. The patient developed a post dural puncture headache the following day, which required treatment with an epidural blood patch. Recovery was otherwise uneventful.

Discussion: Unintentional cannulation of the subdural space is an uncommon but possible complication of epidural placement. Infusion of epidural doses of local anesthetic into the subdural space can result in a clinical picture similar to that of a high spinal, although onset may be delayed for 15-30 seconds. It is important for the anesthesiologist to quickly recognize the situation and provide supportive treatment such as assisting a patients ventilations, administering vasopressors to treat hypotension, and administering anticholinergic agents to treat bradycardia. Intubation and mechanical ventilation may also be necessary. When recognized quickly, a subdural injection of local anesthetic can be treated quickly and effectively without deleterious effects to either mother or fetus.


Morgan, G.E., et al., Clinical Anesthesiology, 2006: 318-319.

SOAP 2009