Robert P. Burns

Toxic effects of local anesthetics.

LOCAL anesthetics are among the most widely used drugs in medical and dental practice; systemic toxic reactions thus may be expected on occasion. As these drugs have found some new applications of late, their toxic effects warrant review—all the more because improved methods of preventing and treating unwanted side effects have become available. This communication describes why a locally injected drug can produce reactions in distant organ systems and what the common symptoms are; it shows ways to minimize the incidence of side effects and, finally, suggests how to treat reactions. Until recent years, local anesthetics were used primarily to numb circumscribed parts of the body by injecting the drug close to spinal roots or peripheral nerve, or by infiltrating it near cutaneous nerve endings. Though some of the drug reaches its intended neural target (there to block impulse conduction), much of the perineurally injected anesthetic falls short of the

Acute reversible lens opacity: Caused by drugs, cold, anoxia, asphyxia, stress, death and dehydration

Acute experimental lens opacities reported to be caused by narcotics, phenothiazines, epinephrine, anoxia, and certain types of lens opacities induced by death, asphyxia, cold or stress are prevented by closure of the animals eyelids. An unawareness of the importance of eyelid position has led to confusion concerning the pathogenesis of many of these lens changes. Most of these experimental cataracts can be classified into a single group with common characteristics, for which we propose the term “acute reversible lens opacity”. The opacity is a reversible loss of transparency of the superficial anterior lens cortex which is prevented by closure of the eyelids. This type of cataract may be produced by mechanical methods or agents which interfere with lid closure or depress the blink reflex. The lens opacity may regress even though the initiating stimulus is maintained. Although dehydration of the aqueous humor and lens is the most important factor in development of the lens transparency change, there are other factors which also play a role.

Excess dietary tyrosine and corneal lesions

Rats fed an abnormally high concentration of L-tyrosine developed a reproducible corneal disease. By biomicroscopy the corneal lesion was seen to progress through definite stages: overall diffuse epithelial haze; discrete, stellate-shaped epithelial opacities; stromal thickening; vascular ingrowth; and finally regression of the opacity. Tyrosine levels were determined spectrofluorometrically at all stages of the disease. Initially, tyrosine in both serum and aqueous humor rose rapidly. The concentration of this amino acid in the aqueous humor exceeded that in serum. While remaining higher than normal, the absolute concentration of tyrosine in serum varied little with time. The content of tyrosine in the aqueous humor decreased slowly. Only the dietary dose of tyrosine was correlated with the elevation in the serum and aqueous humor tyrosine concentrations (P < 0·001). Other factors tested, including sex, presence or absence of pigmentation, and type of ambient light, did not modify the corneal disease.

Hereditary cataracts in deer mice (Peromyscus maniculatus).

A new type of hereditary cataract was predicted in the deer mouse (Peromyscus maniculatus) by the presence of syndactyly of the hind feet. Early morphologic changes were found in the equatorial cells that differentiated into new lens fibers. Later swelling at the anterior and posterior poles of these cells produced lens opacities. Anterior and posterior subcapsular cataracts progressed to a hypermature shrunken lens.

Epidemic Keratoconjunctivitis due to Adenovirus Type 19

A new type of epidemic keratoconjunctivitis, caused by adenovirus type 19, occurred in Oregon in 1974. Although it can be spread by tonometry, in this epidemic finger-to-eye contact appeared to be the cause.

Modification of hypothermic lens opacity in hamsters by closure of eyelids

Lens opacitities developing during hypothermia and cardiac arrest in the Syrian Golden hamster are lesser in degree if the eyelids are kept shut during hypothermia, and much denser if the eyelids are kept open, even though the closed eye is colder than the open eye. The lenses become clear upon reanimation of the animal.

STAPHYLOCOCCAL CENTRAL CORNEAL ULCER

A review of staphylococcal central corneal ulcers has shown that the staphylococcus is the commonest bacterium isolated at the University of Oregon Health Sciences Center. One-third of central corneal ulcers cultured Staphylococci; one-third of these were Staphylococcus aureus. These ulcers occurred in immunodepressed or otherwise previously diseased patients, but not as a primary disease entity. Penicillin resistance was a common characteristic of the isolated Staphylococci. Prognosis for retention of the eye was good.