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 response to hypercapnia, and progressive isocapnic hypoxia in elderly patients. 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 administration of 10 mL of 2% lidocaine. Lumbar epidural anesthesia had no significant effect on resting ventilation, whereas thoracic epidural caused a significant 13% decrease in minute ventilation and a 14% decrease in tidal volume (P < 0.05). The ventilatory response to hypercapnia 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, but minute ventilation at a Spo2 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 response to hypercapnia and hypoxia, despite slight impairment in resting ventilation by thoracic epidural anesthesia, in elderly patients.