MODE OF ACTION OF SUCCINYLCHOLINE ON INTRAOCULAR PRESSURE

¹ Department of Anesthesiology and Ophthalmology Research, Columbia University, College of Physicians and Surgeons, New York, New York

The i.v. injection of 1 to 400 µg/kg of succinylcholine in the cat produced a dose-dependent increase in nictitating membrane tension, superior rectus muscle tension and intraocular pressure. Atropine (1-2 mg/kg), phentolamine (1-2 mg/kg) and propranolol (1 mg/kg) had little or no effect on these responses to succinylcholine. d-Tubocurarine (0.5 mg/kg) markedly depressed or abolished the succinylcholin -induced increase in nictitating membrane tension, superior rectus muscle tension and intraocular pressure. Contrary to the results reported in previous studies, severing the six extraocular muscles from their insertions did not prevent succinylcholine from increasing intraocular pressure, although the magnitude of increase was diminished. d-Tubocurarine blocked the succinylcholine-induced increase in intraocular pressure in both the control and operated eye. It was concluded that the increase in intraocular pressure produced by succinylcholine was not solely attributable to an increase in extraocular muscle tension; another factor was the contraction of orbital smooth muscle. With doses of succinyicholine of 100µg/kg or greater, the rise in arterial pressure could also contribute to the increase in intraocular pressure.