The Case of the Week
Pepper Brown: Admitted 5-16-99 with a swelling of the left front foot. Pain was present and the foot had been fine about an hour earlier. Pepper had been running loose in the wood at the foot of the Blue Ridge Mountains near Table Rock State Park where she lives. There was no sign of bone displacement or trauma except at one site near the carpus. After clipping the hair the presence of paired bite marks was evident. A presumptive diagnosis of snake bite was made. In the area where Pepper lives copperheads and rattlesnakes are both fairly common. We probably see about 10 cases of snake bite a year in our practice. In general the survival is good for both types of bite but we do consider rattlesnake bite to be a little more serious. Often we do not know for sure which type of snake was the offender.
There is some significance to the size of the bite (the distance between the fang marks) which was in this case 22 mm. The size of the patient in relationship to the bite is also important. It is said that the intent of the snake (defensive posture or food gathering) is important but that is always difficult to interpret. In most cases we would expect that the snake was defending itself when the bite occurs.
Pepper's swelling was somewhat less than we sometimes see, about halfway up the foreleg. We always discuss the option of using antivenin for the treatment. The "experts" recommend that it always be given. The biggest drawback to giving antivenin is the cost (about $275 per dose). Another concern is the possibility of an adverse reaction to the antivenin which is made in the bodies of horses that have been induced to create antibodies to pit viper venom. The antivenin thus contains horse proteins. It is possible for the patient to react adversely to the horse proteins and anaphylaxis can occur. The owners were advised of the possibilities and did elect to go ahead with the administration of the antivenin. Ampicillin, Dexamethasone SP (somewhat controversial) and Diphenhydramine were also given.
Before the diphenhydramine was given a small amount of antivenin was injected into the skin to see if there was any sign of allergy to the horse serum. After 10 minutes the site of injection was inspected for signs of a raised red swelling at the injection site. My texts indicate that the administration of antivenin should still be given even if there is evidence of allergy but that it should be monitored especially closely. Since there WAS a reaction we did use additional monitoring during administration and a heavy dose of the antihistamine Diphenhydramine was given before the antivenin was given. The heart rate did drop during administration but no signs of anaphylaxis was seen. Recovery was uneventful and Pepper was discharged the next morning.
A recent article in Missouri Conservationist (May 1999) reported that in the state of Missouri no human has ever died from the bite of a copperhead. The report also indicated that most human emergency physicians do not administer antivenin to humans bitten by copperheads. They do not administer it primarily because of the risk of anaphylaxis.