Arterial Carbon Dioxide and Oxygen Tensions During Spinal Block

Subarachnoid or peridural anesthesia (spinal block) was administered to 32 patients undergoing major surgery. Cutaneous sensory levels ranged from the tenth thoracic to the fifth cervical dermatomes. Supplemental sedation was given to 19 patients during surgery. The arterial Pco2and Po2prior to induction of block, but after premedication, were compared with values obtained during spinal block. There was no significant change in the arterial Pco2and Po2before and after spinal block. Thus, normal ventilation appeared to be unaffected by block of the intercostal nerves. Although the mean arterial Po2remained unchanged, the administration of supplemental oxygen to patients with cardiopulmonary disease might be a wise precaution. A disposable plastic face mask performed this function satisfactorily, raising the Po2above 100 mm Hg.