Complications of Snakebite Treatment

ROBERT E. TOOMS, M.D. FRED M. SANDIFER, M.D.


Over 6,000 persons in the United States are victims of venomous snakebite each year1. While only 15 to 20 of these individuals will die of envenomiza-tion, the number who will experience major amputation and extensive soft-tissue slough is truly frightening. In Florida, where the population of venomous snakes is large, a survey of juvenile amputees under the care of the Florida Crippled Children's Commission revealed that 17 percent of the acquired amputations were due to venomous snakebite2. Few other states would have as high an incidence. Nevertheless, isolated instances could occur almost anywhere. For example, Wells and his colleagues recently reported a case of knee disarticulation following snakebite in a young child seen at the Denver, Colorado, clinic.

There are only four poisonous snakes of medical importance in the United States: the rattlesnake, the cottonmouth moccasin, the copperhead moccasin, and the coral snake. The first three are members of the Family Crotalidae or pit vipers, while the coral snake is a member of the Family Elapidae. The Elapidae possess fangs and venom very different in character from the Crotalidae and produce a different envenomization syndrome3. Venomous snakes have been identified in all of the states with the exception of Maine, Alaska, and Hawaii, but they are more heavily concentrated in the Southeast, Deep South, and Southwest sections of the country4. The number of pit vipers found in the Mid-South region is relatively small by comparison and the coral snake is not an inhabitant of this area.

Since there are comparatively few poisonous snakes in the Mid-South, venomous snakebites are not common. Approximately 80 of the 200 children on our Child Amputee Clinic roster have acquired amputations, but only one of these is the outcome of snakebite. Most physicians in this area, including the authors, are understandably not experienced in the emergency management of venomous snakebite. However, we were recently called into consultation on a child who had been bitten by a venomous serpent, and were thereby stimulated to review some of the literature relative to snakebite manifestations and its management.

Over 5,000 articles have been published regarding snakebite. Many contain contradictory material and suggest treatment measures which have proven to be of little value or even to be detrimental5. Furthermore, most of the newer information gained from animal experimentation and clinical observation in treating snakebite is published in journals seldom read by the practitioner who is most often responsible for the primary care of these injuries. It is not surprising therefore that treatment measures may be employed which are ineffective or which may actually increase tissue loss, compounding the effects of the snake venom. We would like to describe our recent case to initiate a discussion of some of the possible pitfalls in treating snakebite.

Case Report

A five-year-old Caucasian female was admitted to the Pediatric Service of Baptist Memorial Hospital. She had been bitten on the right foot by a snake four days earlier while playing near her home in rural Arkansas, not far from Memphis. The type of snake was not determined. The child was transported at once to her family physician who immediately packed the involved foot and leg in ice, and administered 10 cc. of polyvalent antivenin intramuscularly and a tetanus toxoid booster. To our knowledge, a tourniquet was not applied and no attempt was made to remove the venom locally by suction or excision. Six hours later an additional 10 cc. of polyvalent antivenin was given intramuscularly and a third intramuscular injection of antivenin was given 24 hours later The foot and leg remained packed in ice for approximately four days When the ice was removed, the entire foot and lower leg were cyanotic and the limb began to swell quite rapidly. At this point the child was transferred to the Baptist Memorial Hospital in Memphis.

Upon admission to the pediatric floor the child had a temperature of 99.8 deg. F., pulse 120 beats per minute, respirations 20 per minute, and blood pressure 122/76 mm.Hg The child was lethargic, but in obvious pain. The general physical examination was otherwise nonrevealing and pertinent findings were confined to the right lower limb. The right foot and leg were markedly swollen and the swelling extended up to mid-thigh level. The foot was pulseless, cold, and cyanotic, but there was a small area of pink skin present on the great toe. Cyanotic mottling extended up to mid-calf level and large blisters were present on the foot and ankle. Although sensation was markedly diminished in the entire foot, there was slight preservation of pain sensation to pinprick over the toes. No motor function could be detected in the foot.

Admission laboratory tests revealed a hemoglobin of 11.6 Gm. percent, hematocrit 35 vol. percent, WBC count 19,100/cu. mm. with a shift to the left noted on differential, and platelets 14 6/OIF. Urinalysis showed a pH of 6.0, specific gravity 1.031, two plus proteinuria, no glycosuria, and 2-4 RBC, 0-2 WBC, and numerous finely granular and RBC casts. Prothrombin time was 14.3 seconds with a control of 11.1 seconds. Sedimentation rate was 57 mm. per hour corrected to 36 mm per hour. A special hemorrhagic study revealed no significant abnormalities except a strongly positive protein sulfate precipitation test which was interpreted as due to an earlier intravascular clotting syndrome. Serum electrolytas were normal

The child was treated with intravenous fluids, whole blood transfusions, intravenous cephalosporin, and with analgesics and sedatives. The swelling in the right foot and leg increased and a vascular surgeon was asked to see the patient The day following admission open fasciotomies of all muscle compartments of the leg were performed. The circulation in the foot did not improve postoperatively. The child had daily temperature spikes of 102 to 103 deg. F., but did not seem toxic otherwise. Four days after admission an orthopedic consultation was requested regarding the advisability of amputation. It was felt that amputation was inevitable but, since the level of damaged tissue was not well demarcated, surgery was postponed for approximately one week at which time an open below-knee amputation was done. The child's general condition gradually improved following amputation, and six days later the open stump was secondarily closed and a rigid dressing applied. The stump was healing nicely at the time of the first dressing change one week later, and a temporary plaster prosthesis was applied and ambulation was begun. Ten days later the child was discharged from the hospital and was referred to the Arkansas Crippled Children's Service for follow-up care and definitive prosthetic fitting.

Discussion

Pit-viper venom is a complex combination of several proteins with other less significant constituents which form a neurotoxic principle, a hematoxic principle, and a spreading factor. The neurotoxic principle exerts its effect on distant tissue and causes severe local pain, but little other local reaction, while the hematoxic principle and spreading factor are responsible for most of the local necrosis and tissue slough seen at the site of snakebite 6 .

The severity of venomous snakebite will depend upon many factors including the size and species of the snake, the size of the victim, the length of time the fangs remain in the victim, the presence of multiple bites, the proximity of the bites to the trunk, and the amount and character of any clothing which might be present between the fangs and the skin. Following snakebite symptoms accordingly may vary over a wide range-from minimal (Grade I) in which there is only slight local pain and swelling and no systemic symptoms to very severe (Grade IV). This latter condition is characterized by marked local pain and swelling which rapidly spreads, and early constitutional symptoms of vascular collapse, spontaneous bleeding, convulsions, coma, and death 3 .

Treatment of venomous snakebite has been divided into the following steps by Snyder el al . 5 :

Diagnose the Antigen

Before instituting a vigorous treatment program for snakebite, it is imperative to know whether the offending serpent is poisonous or not. Visual identification of the snake is beneficial. Pit-viper bites produce immediate, excruciating, and prolonged pain followed by local edema and ecchymotic discoloration, while a nonpoisonous bite will not cause these signs and symptoms. A vigorous treatment program is not necessary for nonpoisonous bites, and may cause needless tissue destruction and pain. Treatment of venomous bites must be in accordance with the prognostic signs and symptoms of envenomization and the circumstances governing the rapidity with which a patient can be placed under medical care 3 .

Incarcerate the Antigen

Immediate treatment of snakebite in the field (first aid) should begin with immobilization of the patient by complete body rest and splinting the involved part at heart level. Excitement, exertion, and alcoholic beverages accelerate circulation time and rapidly propel the venom throughout the body. A flat tourniquet should be applied proximal to the bite just tight enough to permit introducing one finger beneath it easily. Prolonged use of a tight tourniquet can result in limb necrosis necessitating amputation.

A completely occlusive tourniquet may be justified in a severe snakebite when no medical treatment can be foreseen for hours and with the knowledge that the extremity is being sacrificed to save the patient 3 . Intermittent loosening and reapplication of the tourniquet, as recommended in some first-aid manuals, should not be done since this actually facilitates the spread of the venom. Once applied, the tourniquet should be left in place until antivenin is given.

Retrieve the Antigen

Experimental studies using I 131 tagged venom have shown that up to 53 percent of injected venom can be retrieved by incision through the injection site and the application of mechanical suction5. In the same study, excision of skin and subcutaneous tissue for one inch around the injection site enabled the investigators to retrieve an average of 79 percent of the injected venom. In these studies, incision and suction or excision of the injection site was carried out within a few minutes of venom injection. Obviously, these measures become progressively less effective the longer the time lapse between envenomization and their application. Many studies have confirmed that most of the venom is retrieved during the first 30 minutes of suction and little venom is removed thereafter. Furthermore, multiple incisions following the line of advancing edema have not yielded significant amounts of venom upon suctioning and are not indicated. Cruciate incisions over the fang marks, at one time universally advocated, have been shown to increase tissue maceration and slough and are no more effective than a single linear incision through both fang marks. Excision of the injection site, when performed by a physician as described above, is advocated in critical snakebites.

Role of Cryotherapy

Cryotherapy in the management of snakebites has been advocated for almost two decades, but has been repeatedly proven, both experimentally and clinically, to be of limited effectiveness in the ultimate prevention of venom absorption. Local refrigeration prevents perfusion of antivenin to the site of venom injection and actually enhances local tissue necrosis. In many instances the injudicious use of cryotherapy has resulted in unnecessary limb loss. Carefully controlled local cooling used for a short period of time prior to antivenin injection may be used to help relieve pain, but packing or immersing a limb in ice has no place in the treatment of snakebite unless amputation at or slightly above the level of the tourniquet is anticipated3.

Neutralize the Antigen

Polyvalent antivenin (Wyeth) has been shown to be the most effective single means of combating serious snakebite and is the keystone of treatment3. It is effective against venom produced by all of the pit vipers found on this continent, but is not effective against coral-snake venom for which a separate antivenin is available.

Since the antivenin is a horse-serum preparation, appropriate sensitivity testing should precede its administration. If sensitivity exists, appropriate de-sensitization should be carried out, or, if the situation is critical, the use of adrenal corticosteroids and/or epinephrine should accompany use of the antivenin. One vial (10 cc.) of antivenin is the usual dosage, but the clinical situation and the patient's response will determine how much to give. Multiple vials may be necessary and can be given without hesitation when indicated. Because of their small blood volume and venom concentration, children will require more antivenin than adults.

When treating snakebite in the field, the antivenin is administered intramuscularly but in a hospital setting or when administered by a physician the intravenous route has proved to be much more effective. Snyder advocates intraarterial infusion of one vial of antivenin in 100 cc. of saline to which 100 mg. of Solucortef have been added, feeling that this route allows more prompt and thorough perfusion of the injured limb. Local infiltration about the fang marks is contraindicated since this only increases local edema and ischemia and is actually less effective than the intramuscular, intravenous, or intra-arterial routes.

Alleviate Symptoms Produced by the Antigen

Pain must be relieved by analgesics, and shock treated with intravenous fluids, circulatory expanders, and blood. Blood transfusions are often indicated to combat the falling hematocrit due to the hemolytic action of the venom. Corticosteroids and ACTH have been shown to be ineffective in treating snakebite and are used only to counteract allergic manifestations of the horse-serum antivenin. Antihistamines have a synergistic effect with the venom and are contraindicated.

Prevent Complications

All victims of poisonous snakebite should be hospitalized for observation. Tetanus prophylaxis and antibiotic protection are indicated. Tracheostomy may be lifesaving in critical cases, and fasciotomy may help prevent amputation in some instances of grossly swollen limbs.

Summary

Although the annual mortality following venomous snakebite in the United States is quite low, the morbidity as expressed in severe soft-tissue slough and even amputation is quite alarming. Many of the therapeutic measures commonly used to treat venomous snakebite, especially by the laiety and by physicians practicing in areas where snakebite is uncommon, are not only ineffective but may actually be detrimental. Some of these are pointed out, and the most effective treatment methods now being advocated are discussed.

References:
1. McCollough, N. C, The juvenile amputee: Preliminary report of the problem in Florida. J. Florida Med. Assoc., 46 :302, 1959.
2. McCollough, N. C, and J. F. Gennaro, Evaluation of venomous snake bite in the Southern United States from parallel clinical and laboratory investigations. J. Florida Med. Assoc, 49 :959, 1963.
3. Oden, L H., Jr., Case history of a snake bite. Consultant, 12 :41, 1972.
4. Parrish, H. M„ J C. Goldner, and S. L. Selberg, Comparison between snake bites in children and adults. Pediat., 46 :251, 1965.
5. Snyder, C. C, R. P. Knowles, J, E. Pickens, and J. L. Emerson, Pathogenesis and treatment of poisonous snake bites. J.A.V.M.A., 151 :1635, 1967.
6. Snyder, C. C, R. Straight, and J. Glenn, The snakebitten hand Plast. & Reconstr. Surg., 49 :275, 1972.
7. Wells, G. Gray, Eugene Bigelow, and Duane G. Messner, Knee disarticulation following snakebite in a young child. Inter-Clin. Information Bull., 11 :7:1-5, April 1972.