Abstract
Introduction: High thoracic or cervical epidural analgesia (HTCEA) causes motor paralysis of the diaphragm and intercostal muscles, and impairs ventilatory parameters. Despite many reports about pulmonary dysfunction under HTCEA, little information is available on estimating the time course and degree of ventilatory impairment when different concentrations of lidocaine are administered. We performed this study to clarify how different concentrations of lidocaine used in upper-thoracic epidural anesthesia affect patients' ventilatory impairment.
Patients and methods: Ten patients scheduled for epidural catheterization to treat their pain were enrolled. Epidural catheterization was established between the C7 and T3 intervertebral spaces. Using a cross-over design, each subject was randomly assigned to one of two groups. A single shot of 10 ml of lidocaine was injected through each patient's catheter on three consecutive days: day 1, the day after the catheter had been inserted; day 2, the day following day 1; and day 3, the day following day 2. Five patients were given 0.5% lidocaine on day 1, 1% on day 2, and 2% on day 3. The remaining five subjects were given the solutions in reverse order: 2% lidocaine on day 1, 1% on day 2, and 0.5% on day 3. With patients in the supine position, a portable spirometer was used to evaluate their pulmonary function before epidural injection and at intervals of 10 min for 60 min after the injection. Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were calculated. After epidural injection, cephalad and caudad sensory blockade was assessed by pinprick at 5-min intervals.
Results: Neither FVC, nor FEV1 changed, except 10 min after 0.5% lidocaine had been injected. After measuring patients' pre-injection FVC and FEV1 values and after administration of 1% lidocaine, patients' FVC and FEV1 values decreased about 10% at 20 min after injection. With 2% lidocaine, the values decreased by 18% at 20 min after injection. FVC and FEV1 started to return to their pre-injection values 30 min after injection, even with 2% lidocaine.
Conclusions: The degree of impaired pulmonary function depends on the concentration. Patients' FVC and FEV1 values started returning to their pre-injection levels 30 min after injection. The results suggest that patients should be monitored for at least 30 min after high thoracic epidural injection of lidocaine.