Circulatory responses to airway stimulation and cervical epidural blockade

In order to investigate the effects of acute cardiac sympathectomy, the circulatory responses due to tracheal intubation and broncho-carinal stimulation were compared in lightly anesthetized, paralyzed patients who had either cervical (n = 18) or lumbar epidural blockade (n = 18), or neither (n = 12). The mean analgesic levels obtained using 2% mepivacaine with epinephrine were C4-T8 in the cervical group, and T7-S1 in the lumbar group. Increases in arterial blood pressure (AP) and heart rate (HR) due to laryngoscopy were significant (P less than 0.01) but similar in the three groups of patients. Broncho-carinal stimulation by a suction catheter did not produce noticeable changes in AP and HR in the cervical group; significant increases were observed in the other two groups (P less than 0.01). It was concluded from this study that acute sympathectomy induced in part by cervical or lumbar epidural block does not attentuate circulatory responses due to laryngoscopy and tracheal intubation. The cervical blockade, however, can prevent such responses due to broncho-carinal stimulation without predominant vagotonic reflexes; this may be attributed to the interruption of sympathetic afferents to the spinal cord at the epidural level.