Propranolol in thyrotoxicosis. Cardiovascular changes during thyroidectomy in patients pre-treated with propranolol.

The cardiovascular changes during anaesthesia and thyroidectomy have been studied in seven thyrotoxic patients prepared with propranolol. The heart rate and cardiac rhythm remained very stable throughout surgery. A 20% increase in mean arterial pressure occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgery, reaching a maximum of 21% during ligation of the thyroid vessels and returning to pre-operative values by the end of surgery. The fall in cardiac output was accompanied by raised central venous pressure and raised total peripheral resistance.