THE EFFECT OF SUPPLEMENTAL OXYGEN ON THE INCIDENCE OF HYPOXEMIA AFTERPREMEDICATION IN PATIENTS UNDERGOING CARDIAC-SURGERY

Opiate premedication may cause significant respiratory depression, par ticularly when other sedative agents such as scopolamine or benzodiaze pines are added, This can cause hypoxaemia with potential for worsenin g myocardial ischaemia in cardiac surgery patients. The aim of this st udy was to investigate the incidence of hypoxaemia (SpO(2) <90%) in el ective patients undergoing cardiac surgery and to assess the efficacy of supplemental oxygen in preventing it. One hundred elective patients without significant respiratory disease or cardiac failure, who recei ved both an opiate and a sedative premedication, were prospectively ra ndomized to receive either oxygen via a facemask at 4 l/min or no oxyg en. Continuous arterial oxygen saturation was recorded using a pulse o ximeter from the time of premedication until the patient arrived in th eatre. An SpO(2) <90% was recorded as a significant event and oxygen w as administered to the patients. Six patients were excluded because of equipment failure or protocol violations, The patient groups were com parable with respect to patient demographics, premedication type and d ose or the duration of monitoring, In patients receiving oxygen (n=48) there were no episodes of hypoxaemia (0%), In patients not receiving oxygen (n=46) there were 14 episodes of hypoxaemia (30%, P<0,0001). We conclude that there is a significantly high incidence of hypoxaemia i n cardiac surgery patients following combined opiate and sedative prem edication and that it can be reduced by the routine administration of supplemental oxygen.