Fluoroscopy-guided Versus Traditional Placement of Epidural Catheters

Overview

This is a prospective, randomized, controlled, and single blinded study. All work performed at Dartmouth-Hitchcock Medical Center, a tertiary care and level one trauma center for the state of New Hampshire with 28 operative suites. 100 patients scheduled to undergo thoracotomies are randomized to receive an epidural placed (for postoperative pain control) using either a traditional approach by feeling the spine for landmarks or using fluoroscopic X-ray guidance. Randomization is blinded to both the anesthesia team caring for the patient in the operating room and to one member of the acute pain team who follows the patient after surgery and is responsible for evaluating post operative pain control (dermatomal distribution of sensory blockade and visual analog scale) and pulmonary function (incentive spirometer use). All patients receive a standardized epidural infusion with local anesthetic and additional pain medications as needed.

All epidurals catheters are placed by the Acute Pain Service in the preoperative period in an operating room equipped for fluoroscopy. Patients will have been previously randomized (following written informed consent) to either standard placement of epidural catheters or fluoroscopically-guided placement. Standard placement (Comparator): According to usual practice, epidurals placed using the standard technique will be placed in the sitting position using a 'loss of resistance' technique. This technique involves approximation of the T7 vertebral body through palpation of the distal aspect of the scapula and identification of midline through palpation of the spinous processes. The skin is then anesthetized with 1% Lidocaine and an 18 gauge Tuohy needle is inserted until there is engagement with the supraspinous and interspinous ligaments. A glass syringe filled with saline and air is then attached to the Tuohy needle, which is slowly advanced until the epidural space is identified with loss of resistance to injection in the glass syringe. The glass syringe is then detached from the Tuohy needle and the epidural catheter is threaded approximately 3-4 cm into the epidural space. The catheter will then be aspirated using a 3ml syringe to confirm that it has not been place in the intravascular or intrathecal space. Five ml of radiopaque dye (omnipaque) will be injected and a single image taken and stored on disc but not read by a clinician. A test dose of 3ml of 1.5% Lidocaine with epinephrine will then be injected to ensure that the catheter is not intravascular. Fluoroscopically guided epidural placement (Experimental): Patients will be placed in the prone position. Identification of an appropriate interspace (T7-T12) and midline orientation will be accomplished using fluoroscopic guidance. The skin will then be anesthetized and the epidural space identified using the loss of resistance as described above. Fluoroscopy will be used during identification of the epidural space to confirm midline orientation during advancement of the Tuohy needle. Once the epidural space is identified, the epidural catheter will be advanced to the T4 level. The catheter will then be aspirated as above. 5cc of Omnipaque will be injected into the catheter with anterior-posterior and lateral imaging to ensure expected spread of the dye as confirmation of correct placement in the epidural space. The catheter will then be bolused with 3cc of 1.5% lidocaine with epinephrine to ensure that the catheters are not placed intravascularly. Following epidural placement via either technique, patients will then be transferred to the surgical operating room where an infusion of 1/8% Bupivicaine will be started at a rate of 4ml/hr. This epidural infusion will continue throughout the case. Titration of this infusion will be guided by clinical judgment of the primary anesthesia team in the operating room between the range of 0-14 ml/hr with primary assessments including the patient's analgesic requirement and hemodynamic stability. Intraoperative period: A standardized anesthesia induction and maintenance protocol will be used. This protocol will include sedation with 2mg of midazolam and fentanyl (1-2mcg/kg) for epidural placement, 2-3 μg/kg fentanyl prior to induction, 2-2.5mg/kg propofol on induction and isoflurane for maintenance of anesthesia. Additional narcotic administration is at the discretion of the primary anesthesia team but recommended for patients up to their daily opiate dose, plus an additional 0.1mg/kg morphine at or before emergence. Ketorolac 15mg may be administered as clinically indicated unless contraindications such as age \>75, renal insufficiency (gfr \<60) or surgeon preference. In addition, 4mg dexamethasone will be administered on induction. Nitrous oxide and ketamine will not be used. Hemodynamic monitoring will be accomplished with standard monitors, an arterial line placed by the primary anesthesia team, and, if indicated, noninvasive cardiac outcome monitors. The arterial line will be placed according to the preference of the primary anesthesia team. Postoperative period: Post operative pain management will be dictated by the primary surgical service. Typical management includes patient-controlled analgesia of IV morphine, fentanyl or hydromorphone with transition to oral medications as indicated on post operative day one. Titration of the epidural between the 4cc/hr up to a maximum of 14cc/hr will be made based upon a specific protocol for inadequate pain relief. The epidural will be bolused with 4cc from the standard solution and then the rate of the infusion will be increased by 2cc/hr if and when a patient requires better analgesia. If the epidural is deemed non functioning by the supervising attending on the pain service, as evidence by a lack of sensory blockade in the distribution of the incision and patient discomfort, then it is at the discretion of the acute pain service attending to remove or replace the non-functional epidural.