Just Say No to Ratio!
One of the treatments for priapism (prolonged painful erection that occurs without sexual stimulation) is to inject an alpha-agonist — phenylephrine or epinephrine, for example — into the penis (intracavernous injection). This causes vessels to narrow and reduces blood flow. The procedure typically calls for a 1:1,000,000 solution of epinephrine prepared by adding 1 mg (1:1,000) in 1 liter of normal saline. The corpora cavernosa is then irrigated with 10 to 20 mL of the 1:1,000,000 epinephrine solution. This may be repeated 3 to 4 times if needed. But as we’ve often pointed out, people confuse these ratio designations, sometimes with tragic results!
Recently a 16-year-old male was brought to an emergency department with priapism. A urologist ordered epinephrine, but unfortunately, he thought that the 1:1,000 ratio on the epinephrine 1 mg/mL label meant that the epinephrine was already “prediluted” with 1,000 mL of fluid. The patient received 4 mL (4 mg) of undiluted solution injected into his penis. As the epinephrine reached systemic circulation, the patient arrested and could not be resuscitated.
To reduce the risk of errors, do not stock the larger 30 mL vials of epinephrine 1:1,000. If this concentration is necessary, stock just the 1 mL ampuls so that the need for multiple ampuls can serve as a red alert to the healthcare provider. Review our October 16, 2002, newsletter article, “It doesn’t pay to play the percentages,” for additional advice on addressing this problem.