Assessment by continuous cardiac monitoring of minimum duration of preoperative propranolol treatment in thyrotoxic patients.

The effect of the beta-blocker, propranolol (40 mg 6-hourly orally) has been studied on the tachycardia of six patients with untreated thyrotoxicosis. Heart rate was monitored continuously using a light portable ECG recorder which allowed the patients to undertake normal activities during the recording periods. The most marked reduction in heart rate was evident at 24 h after starting propranolol treatment. In three of the patients there was only a minor further fall in heart rate despite continued propranolol administration, but in the remaining patients the reduction in heart rate with each successive day of treatment was more marked. These results suggest that if propranolol were to be used alone in the preparation of patients before partial thyroidectomy for thyrotoxicosis, a dose of 40 mg 6-hourly for 3-4 days might be sufficient.