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 therefore expect pulmonary compromise due to the block of the phrenic nerve if anesthesia extends to C3. This study was conducted to measure the effects of cervical epidural anesthesia using 2% lidocaine on pulmonary function, with specific attention given to the time course of pulmonary changes in relation to spread of analgesia. Methods. Fifteen adult patients without preexisting lung disease undergoing carotid endarterectomy, breast surgery, or cervical epidural steroid injection were enrolled. Cervical epidural anesthesia was performed at the C7-T1 interspace using 300 mg lidocaine with epinephrine. Pulmonary function, including forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), maximum inspiratory pressure (MIP), and SpO₂ while breathing room air were measured prior to and 5, 10, 20, and 40 minutes after lidocaine injection. Results. Analgesia to pinprick reached median dermatomes of C3 to T8 (range: C2-T12) by 20 minutes after lidocaine injection. FEV₁ and FVC decreased approximately 12-16%, between 20 and 40 minutes after injection. Maximum inspiratory pressure and SpO₂ did not significantly change. Conclusions. Cervical epidural anesthesia using 300 mg lidocaine results in measurable reduction in bedside pulmonary functions concomitant with the spread of analgesia to the C3 dermatome. These changes were complete 20 minutes after lidocaine injection. In patients without preexisting lung disease, these changes were not clinically significant, except in one patient. We conclude that motor block of the phrenic nerve is incomplete under the conditions of this study.