Patients admitted with acute myocardial infarction to general medical wards fared less well than those admitted over the same period to the coronary care unit. The median age of the 119 patients admitted to the general wards was 75 years, compared to 64 years for those on the coronary care unit. Although 13 of the 119 fulfilled the local guidelines for thrombolysis, none received it, only 64% were given aspirin and 49% nitrates. The death rate for these patients was 29% compared to 12% of those given thrombolysis on the coronary care unit and 26% of those who were ineligible for thrombolysis but had been admitted to the coronary care unit. Of the survivors on the general wards, 80% were given aspirin as secondary prevention, and 37% were given a beta-adrenergic blocker. None was referred to the hospital cardiac rehabilitation programme.

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Hypoxaemia and supplemental oxygen therapy in the first 24 hours after myocardial infarction: the role of pulse oximetry.

OBJECTIVE: To assess the incidence and degree of hypoxaemia in patients with acute myocardial infarction and evaluate the nation-wide perception and usage of oxygen therapy. DESIGN: Postal survey of all coronary care units (CCU) in England of their use of prescribed oxygen and pulse oximetry. Prospective randomised study of 50 patients presenting within 24 hours of onset of myocardial infarction, half of whom received oxygen therapy. Oxygen saturation (SpO2) as continuously measured by pulse oximetry, and arrhythmias and ST segment changes were recorded on simultaneous 24-hour ambulatory Holter monitors. RESULTS: In 53% of UK coronary care units oxygen is not routinely prescribed but in only 3% is a pulse oximeter used to aid management. In patients presenting with acute myocardial infarction the incidence of hypoxaemia (SpO2 < 90%) was 70% and severe hypoxaemia 35% in those not given oxygen, compared with only 27% and 4% in patients given oxygen therapy. The only patient to receive oxygen on clinical grounds had an oxygen saturation of 71%. Severe hypoxaemia (SpO2 < 80%) occurred significantly less often (1 and 7 patients, p < 0.05) in patients given oxygen. There were no differences in arrhythmias or ST segment changes between groups. CONCLUSION: Hypoxaemia occurs frequently in patients in the first 24 hours after acute myocardial infarction. It is effectively and easily treated with supplemental oxygen which can be guided by pulse oximetry. This is rarely done. Measurements of oxygen saturation are therefore justified in all patients to guide oxygen therapy unless there is a decision to give all patients supplemental oxygen: this we believe to be unnecessary.

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