Preliminary report on the use of methonium compounds and general anaesthesia in ophthalmic surgery.

IN his lecture " Medicine, Yesterday and To-morrow ", Sir Henry Dale mentioned, as the most recent addition to the technique of preparing a patient for a surgical operation, synthetic substances which, by their action on the sympathetic ganglia, lower the arterial blood pressure and enable a postural adjustment of the patient to produce a practically bloodless field of operation (Dale, 1951). In routine operations on the eyeball, haemorrhage is ofno great consequence, since it may be controlled by careful pre-operative preparation, vasoconstrictor drugs, local pressure, or cautery. But in operations which involve accurate technique in small deep cavities amongst important structures, as in the orbit, severe haemorrhage may be difficult to control, and may impede the smooth progress of the operation. In Plastic Units this situation frequently occurs, since the ophthalmic surgeon is required to deal with the effects of severe trauma and cicatrization in and around the orbit. Such cases do not lend themselves to local anaesthesia as do most operations on the globe, and general anaesthesia has become routine. Enderby (1950) reported the use of pentamethonium iodide in the production of controlled hypotension during general anaesthesia, but the results were irregular and unpredictable. Since then he has replaced the drug by hexamethonium bromide and made it possible to achieve accurate temporary control of blood pressure in 85 per cent. of his cases. Rollason (1951) has also found that hexamethonium is more certain and more effective than pentamethonium iodide. The object of controlled hypotension or " postural ischaemia "t is to eliminate bleeding at the site of operation. This object is achieved by a combination of the effects of hexamethonium bromide on vessel tone with an arrangement of posture which causes re-distribution of blood to the dependent parts of the body. Enderby and Pelmore (1951) made the following claims for controlled hypotension by this method in general anaesthesia: