TIME-COURSE OF THE EFFECTS OF CERVICAL EPIDURAL-ANESTHESIA ON PULMONARY-FUNCTION

Background and Objectives. During cervical epidural anesthesia the C4, C5, and sometimes C3 nerve roots are anesthetized. One might therefor e expect pulmonary compromise due to the block of the phrenic nerve if anesthesia extends to C3. This study was conducted to measure the eff ects of cervical epidural anesthesia using 2% lidocaine on pulmonary f unction, with specific attention given to the time course of pulmonary changes in relation to spread of analgesia. Methods. Fifteen adult pa tients without preexisting lung disease undergoing carotid endarterect omy, breast surgery, or cervical epidural steroid injection were enrol led. Cervical epidural anesthesia was performed at the C7-T1 interspac e using 300 mg lidocaine with epinephrine. Pulmonary function, includi ng forced expiratory volume in one second (FEV1), forced vital capacit y (FVC), maximum inspiratory pressure (MIP), and SpO(2) while breathin g room air were measured prior to and 5, 10, 20, and 40 minutes after lidocaine injection. Results. Analgesia to pinprick reached median der matomes of C3 to T8 (range: C2-T12) by 20 minutes after lidocaine inje ction. FEV1 and FVC decreased approximately 12-16% between 20 and 40 m inutes after injection. Maximum inspiratory pressure and SpO(2) did no t significantly change. Conclusions. Cervical epidural anesthesia usin g 300 mg lidocaine results in measurable reduction in bedside pulmonar y functions concomitant with the spread of analgesia to the C3 dermato me. These changes were complete 20 minutes after lidocaine injection. In patients without preexisting lung disease, these changes were not c linically significant, except in one patient. We conclude that motor b lock of the phrenic nerve is incomplete under the conditions of this s tudy.