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UNLABELLED We examined the success of inserting epidural catheters via the caudal route in infants by using electrocardiographic guidance. A case series of 20 patients with thoracic epidural analgesia was studied. After the induction of general anesthesia, an 18-gauge IV catheter was inserted into the caudal space to allow threading of a 20-gauge epidural catheter. The electrocardiogram (ECG) tracings via the epidural catheter, as well as the surface ECG at the target spine level, were recorded simultaneously with a modified two-channel five-lead ECG system. The epidural catheter was advanced from the caudal space until the tip reached the target level as demonstrated by a match in the configuration of the epidural ECG tracing to that of the surface ECG tracing at the target level. The catheter tip location was verified by postoperative radiographs. All catheter tips were located within two vertebrae of the target level, and satisfactory intraoperative epidural anesthesia was achieved in all subjects. IMPLICATIONS Epidural electrocardiography may be used to guide the positioning of the thoracic epidural catheter tip via the caudal approach to the appropriate dermatome for optimum analgesia.

We designed this study to determine the threshold current for nerve stimulation of an insulated needle in the epidural space. The intended dermatome was identified using the bony landmarks of the spine. An 18-gauge insulated Tuohy needle was inserted perpendicularly to the skin and advanced until "loss of resistance" was felt. A nerve stimulator was then connected to the insulated needle. Twenty patients were studied using an insulated Tuohy needle and one patient was studied using a noninsulated Tuohy needle. Muscle twitch was elicited with a current of 11.1 +/- 3.1 mA (mean +/- sd) in all patients in which an insulated needle was used. Muscle twitches were within 2 myotomes of the intended level (based on bony landmarks). Muscle twitch was not elicited with a noninsulated needle. After catheter threading, positive stimulation tests were elicited via epidural catheters in all patients (4.9 +/- 2.3 mA). Postoperative radiograph confirmed all catheter placements within 2 myotomes of the muscle twitches. Electrical stimulation may be a useful adjuvant tool to loss of resistance for confirming proper thoracic epidural needle placement. The threshold current criteria for an insulated needle (6-17 mA) would be higher than the original Tsui test criteria described for an epidural catheter (1-10 mA) in the epidural space.