Succinylcholine and acetazolamide (Diamox) in anaesthesia for ocular surgery

Abstract

SUCCINYLCrIOLINE IS the muscle rel~xant of choice for tracheal mtubatlon, and tracheal mtubahon is a reqmslte for a satisfactory general anaesthesm m mtraocular surgery However, succmylchohne is known to increase mtraoeular tension In 1955 and 1957 there were reports m the hterature of loss of vitreous occurring during surgery of the open eye when succmylchohne was used m anaesthesia, x,~ with a resultmg loss of vision Succmylchohne also represented a serious hazard to patients wah glaucoma s-7A study was undertaken m the l~epartment of Anaesthesm of the Wmmpeg General Hospital to determine whether prewous admmrstratlon of acetazolamlde ( Dlamox ) would prevent the dangerous rise m mtraocular pressure accompanying the use of succmylcholme in anaesthesia If the results proved successful, then this valuable muscle relaxant could be safely employed in cataract extractions and corneal transplants, and m patients suffering from glaucomaThe most important factor determining the internal pressure of the eye iS the aqueous humour, the hydrostatic pressure of the blood accounting for only one-quarter of the total mtraocular tension Formed in the clhary processes behind the ms by a combination of diffusion and actwe transport, m which the enzyme carbomc anhydrase plays an important chamber and leaves the eye by the canal of Rapid mcreases m mtraocular pressure flow of the aqueous m most cases. The role, the aqueous fills the posterior Schlemm (Fig 1) s-ll are due to interference with the outnormal eye has a great capacity for compensating any increase m mtraocular pressure, smaply by increasing the rate of outflow of the aqueous The osmotic pressure of the aqueous humour is higher than the osmotic pressure of the blood If we compare the composition of the aqueous with that of blood, we o~serve that while the amount of protein of the aqueous is as low as 0 02 gin/100 ml, and the glucose, urea, and bicarbonate concentrations are lower than m blood, those of the chlorides, sodmm, and lactate are higher The aqueous is the only means of nutntxon of the lens and cornea, smce they are devoxd of blood supply 12-14The normal mtraocular pressure has an accepted physxologlcal range of 10 to 22 mm Hg above atmospheric pressure. There is a variation of 2 to 3 mm. Hg dady for each mdlvadual, the higher readings being obtained m the early hours of the morning, and the lower ones early in the evening Position also accounts for a difference of 2 to 3 mm Hg, the reading being higher during recumbency than m a standing position 15

Normocapnic anaesthesia for intraocular surgery.

“…It has been shown that acetazolamide increases choroidal blood flow by up to three times. This drug has previously been claimed to prevent suxamethoniuminduced rise of intraocular pressure, though the mechanism is obscure (Carballo, 1965). It seems likely that acetazolamide may in fact produce an increase in TOP itself, after which the effect of suxamethonium is attenuated (Holloway, 1977).…”

Suxamethonium-A Review: Part III—Pharmacological Actions of Suxamethonium Apart from Its Neuromuscular Blocking Effect

“…The most important factor determining the internal pressure of the eye is the aqueous humour, the hydrostatic pressure of the blood accounting for only one-quarter of the total resting intraocular tension (Carballo 1965). The aqueous, which is formed by the ciliary process under the influence of carbonic anhydrase passes into the posterior chamber, through the pupil into the anterior chamber, and leaves the eye by way of the canal of Schlemm (Figure 2).…”

“…The cannula is usually attached to a transducerpen-recorder system. This method gives a direct, continuous recording but because of the invasive nature of the monitoring it has only been used in animal experiments, and is considered unsuitable for use in man (Lincoff , Dillon et al 1957b, Wretland and Wahlin 1958, Carballo 1965, Adams and Barnett 1966. Tonometry must be considered an inferior form of measurement to manometry.…”

“…It was originally thought that contraction of the extraocular muscles was responsible for the raised pressure (Hofmann and Holzer 1953, Lincoff et al 1955, Dillon et al 1957a, 1957b, Schwartz and de Roetth 1958. These muscles are highly specialized and are unlike striated muscles found elsewhere in the body (Lincoff et al 1955, Carballo 1965, Eakins and Katz 1966, Katz, Eakins and Lord 1968. They contain two separate neuromuscular systems.…”

Pharmacological aspects of anaesthesia for implantation of the artificial lens

“…Thus administration of an opiate as premedicant can, according to CarbaUo (1965), depress IOP by as much as 10%. There is doubt as to whether fentanyl has any effect although in high doses fentanyl can lead to a rise in lOP (Henschel, 1975).…”