Respiratory changes during continuous epidural blockade.

Abstract

In 23 otherwise healthy patients a study of respiratory function was carried out during 2 days with continuous epidural blockade in connection with cholecystectomy. Thirteen of the patients received blockade of thoracic extent (T2‐T12) and ten of thoraco‐lumbar extent (T4‐L4). Preoperatwely, noteworthy changes were found in the thoracic group, where respiratory muscle force was slightly, and dynamic tests of ventilatory capacity were significantly decreased. Postoperatiwely, a significant but relatively moderate decrease in Pao2 (from 86 to 77 mm Hg) was seen in both groups. One hour after surgery Paco2 was slightly increased (42 mm Hg) in the thoracic group, but was thereafter in both groups slighly decreased. A significant but moderate metabolic acidosis was present (pH 7.35). On the day after surgery the alveolo‐arterial oxygen difference was in the thoracic group significantly increased (from 12 to 25 mm Hg), and so was physiological shunting (from 6 to 12 per cent) with a more pronounced increase at high values of cardiac output. In both groups, the ventilation‐perfusion ratio remained fairly unchanged.Dynamic tests of ventilatory capacity decreased significantly by about 50 per cent. Thoracic inspiratory force decreased more in the thoracic than in the lumbar group. In general, respiration seemed to be more affected under conditions with epidural blockade of thoracic than of thoraco‐lumbar extent.