Confirmation of location of epidural catheters by epidural pressure waveform and computed tomography cathetergram

Objective: Epidural pressure has remained a relatively unused test of physi ological monitoring for the past 3 decades. It is our hypothesis that epidu ral pressure waveforms (EPWFs) obtained by transducing an epidural catheter (EC) can be used as a surrogate for the accurate location of the EC. The g oal of this study was to validate this new method by comparing it with a mo re objective radiographic technique such as computed tomography cathetergra m (CTC). Methods: The EPWF and CTC were studied in 13 patients receiving continuous epidural analgesia (12 patients who had postoperative pain and I patient wh o had chronic pain). Of these 13 patients, 8 patients had reported inadequa te analgesia, and 5 had reported satisfactory analgesia. First, the end of the EC was connected to a disposable pressure transducer, this was followed by a 5-mL normal saline bolus injection to ensure the patency of the EC, a nd the EPWF was recorded. Next, the patient was taken to an imaging suite a nd, after injecting contrast through the EC, the course of the catheter was imaged with computed tomography (CT). The CT images were studied by the ne uroradiologist and correlated with the EPWF. Results: The EPWF of 5 patients with clinically adequate analgesia revealed a pulsatile waveform on transducing the EC and a crescentic spread of cont rast in the epidural space on CTC. In 8 patients with inadequate epidural a nalgesia, the EPWF measurement failed to show oscillations, and contrast co llections were observed in the paraspinous muscles. The results of EPWF and CTC were compared using Fisher's exact test. Conclusions: The strong relationship between EPWF and CTC suggests that EPW F can be used reliably to confirm the correct placement of the EC in a sele cted group of patients.