THE EFFECTS OF EPIDURAL-ANESTHESIA ON VENTILATORY RESPONSE TO HYPERCAPNIA AND HYPOXIA IN ELDERLY PATIENTS

Epidural anesthesia may impair pulmonary ventilation in elderly people . We examined the effects of lumbar or thoracic epidural anesthesia on resting ventilation, arterial blood gas tensions, the ventilatory res ponse to hypercapnia, and progressive isocapnic hypoxia in elderly pat ients. Two groups of eight unpremedicated elderly patients, aged 65 yr or older, undergoing lower or upper abdominal surgery, respectively, were studied twice before and 20 min after the lumbar or thoracic admi nistration of 10 mL of 2% lidocaine. Lumbar epidural anesthesia had no significant effect on resting ventilation, whereas thoracic epidural caused a significant 13% decease in minute ventilation and a 14% decre ase in tidal volume (P < 0.05). The ventilatory response to hypercapni a was significantly increased after lumbar epidural anesthesia, but no change was observed after thoracic epidural anesthesia. The slope of the hypoxic response curve did not show any change in either group, bu t minute ventilation at a Spo(2) of 90% significantly increased after lumbar epidural anesthesia (P < 0.05). We conclude that neither lumbar nor thoracic epidural anesthesia per se impairs the ventilatory respo nse to hypercapnia and hypoxia, despite slight impairment in resting v entilation by thoracic epidural anesthesia, in elderly patients.