EFFECT OF LUMBAR EPIDURAL-ANESTHESIA ON VENTILATORY RESPONSE TO HYPERCAPNIA IN YOUNG AND ELDERLY PATIENTS

Study Objective: To examine the influence of age on resting ventilatio n, arterial blood gas tensions, and the ventilatory response to hyperc apnia in lumbar epidural anesthesia. Design: Clinical study using grou ps of young and elderly patients. Setting: Surgical operation center o f a university hospital. Patients: Seven young (average age 39 years) and seven elderly (average age, 69 years) unpremedicated patients unde rgoing lower abdominal surgery. Interventions: Patients were administe red lumbar epidural anesthesia with 10 ml of 2% lidocaine. Measurement s and Main Results: Resting ventilation, arterial blood gas tensions, and ventilatory response to hypercapnia were measured before and 20 mi nutes after the block. Regarding the ventilatory response to hypercapn ia, the mean slope of the hypercapnic response curve [change in minute ventilation (VE) divided by change in end-tidal partial pressure of c arbon dioxide (PETCO2)] increased significantly following the epidural block, by 16% in the young patients and by 23% in the elderly patient s, and the mean VE at a PETCO2 of 55 mmHg (VE55) also increased signif icantly, by 16% in the young subjects and by 26% in the older subjects . These changes in DELTAVE/DELTAPETCO2 and VE55 were statistically equ ivalent between the two age-groups. Conclusions: The effects of lumbar epidural anesthesia on resting ventilation, arterial blood gas tensio ns, and ventilatory response to hypercapnia were not affected by age.