Canadian Journal of Anesthesia, Vol 19, 639-646, Copyright © 1972 by Canadian Anesthesiologists' Society

The Influence of Premedication with Narcotics and Belladonna on Oxygenation in Cardiac Surgery Patients

¹ (Pulmonary Disease), St. Paul's Hospital, British Columbia
² Unversity of British Columbia and St. Pauls's Hospital

The influence on oxygenation of premedication with mixtures of narcotic and belladonna drugs was assessed in 15 cardiac surgery patients. With the subjects breathing room air and then 100 per cent oxgen, comparisons were made of preoperative measurements of arterial oxygen tension, carbon dioxide tension and pH. The same parameters were measured one hour after premedication using morphine 0.15 mg/kg or meperidine 1.5 mg/kg in combinations with atropine 0.6 mg or scopolamine 0.4 or 0.6 mg. End-tidal carbon dioxide and oxgen tensions were measured in all cases to evalute alveolar-arterial oxygen (A-aDO₂) and carbon dioxide gradients (a-ADCO²). The results show a significant increase in PaO₂ after premedication, with a slight decrease in pH and no significant change in arterial oxygen saturation. A-aDO₂ gradients did not increase significantly with premedication suggesting that increased right to left shunting did not occur. Changes in a-ADCO₂ ratios indicated slight but significant ventilation-perfusion changes but they were not large enough to decrease arterial oxygenation. Dead space tidal volume ratios (V_D/V_T) did not change after premedicaion but did alter markedly with increased oxygen. All subjects exhibited large tidal volumes and this may have been a factor in prevention of shunting by prevention of atelectasis. The ages and ambulatory status of this group were key factors.

This study shows that narcotic-belladonna premedication does not compromise oxygenation of the ambulatory cardiac surgery patient when used in judicious doses.

Note:

Presented at Cansdian Anaesthetists' Soiety Annual Meeting, Halifax. June, 1972.