The above question was submitted to four authorities and the following replies were received:

Transcription

1 Journal ofwilderness Medicine,S, (1994) VIEWPOINTS A rock climber receives a deep rattlesnake bite on th~ iiorsum of the hand. What is your opinion regarding the following methods of management? (1) Make incisions across each fang bite. (2) Apply mouth suction. (3) Use a commercially available suction venom extractor. (4) Apply a venous-constricting tourniquet above the wrist. (5) Pack the arm in snow. (6) Immobilize the arm in a splint. (7) Hold the hand above the head during transport to a hospital. (8) Inject antivenom intravenously. (9) Kill the snake for identification. The above question was submitted to four authorities and the following replies were received: Most authorities on the treatment of snake bite eventually come to the conclusion that the less first aid performed in the field, the better for the victim. Although the use of incisions across each fang bite has in the past been advocated, if it appears that it will take longer than 1.5 h to reach an emergency department, the potential for increased morbidity and the technique's questionable effectiveness make it best to discourage this method. This would be particularly true for a bite on the dorsum of the hand. Mouth suction raises several concerns beyond failing to follow OSHA standards on managing bloodborne pathogens [1]. The probable lack of effectiveness of low-vacuum techniques and the potential of wound contamination come to mind. The low-vacuum rubber suction cup systems sold in nearly every outdoor store similarly have no apparent value. The only studied commercially available suction venom extractor which has any proven value is The Extractor (Sawyer Products), which appears to be able to remove 30% of the venom if applied within 3 min after the bite [2]. This device is being investigated for possible increased effectiveness if it were to be applied more rapidly. Venous constricting bands applied only tightly enough to prevent superficial venous flow have been advocated by many authorities, but the use of an arterial or deep venous tourniquet has been associated with increased tissue damage. Snow packing appears to increase tissue damage. I am not aware of studies showing the effectiveness of splint immobilization or elevation of an extremity, but I doubt these techniques would be harmful. The current consensus is that the extremity should be kept below heart level. I would doubt that the use of antivenom in the field would be advocated due to its potential for inducing anaphylaxis, the large volume generally required, and its high cost relative to a first aid kit. Antivenom injected intravenously in the Emergency Department may be the drug of choice if the exposure has been to a very virulent snake (such as the Mojave rattler) or there are indications of actual envenomation, decreased response to a two-point discrimination test, decreased joint mobility, evidence of a compartment syn Chapman & Hall

2 Viewpoints 217 drome, or coagulopathy. Killing the snake is probably not practical and generally not necessary when adequate Emergency Department follow-up is sought. 1. Occupational Safety and Health Administration, U.S. Department of Labor. Occupational exposure to bloodborne pathogens; final rule. 29 CFR Federal Register, 1991; 56, Bornstein, AC., Russell, F.E. and Sullivan, J.B. Negative pressure suction in field treatment of rattlesnake bit. Vet Hum Toxieol, 1985; 25, 297. WILLIAM FORGEY, MD Merrillville, Indiana, USA Concerning the issue of incision and suction, as I am sure you are aware, this is still extremely controversial. Some basic research has indicated a benefit when the technique is begun immediately by a trained (in anatomy and surgical techniques) rescuer with appropriate equipment. This is, however, almost never the situation in the field, and, therefore, the risks involved in incision and suction outweigh any possible benefit. I think the issue of a commercially available suction device, such as The Extractor, is less bothersome. There is some preliminary work that would indicate this device is capable of removing an unknown quantity of venom from a pit viper bite site when it is applied immediately. At the least, it probably does no harm. In the course of frequent lectures on this topic, I recommend that people venturing into wilderness environments carry The Extractor. In regions of the country where extremely large pit vipers may be encountered (in the range of the eastern and western diamondback rattlesnakes) I recommend that they carry two Extractors, since the largest suction cup is only 1 in. in diameter; if more than one bite is received or the fang marks are greater than 1 in. apart, one device would be insufficient. The next issue was the use of a venous-constricting tourniquet. I prefer to refrain from using the term "tourniquet," and refer to this device as a constricting band. The band probably does no harm when applied appropriately (just tight enough to limit return of superficial venous and lymphatic fluids). The only danger in my mind is that this could become a true tourniquet (obstructing arterial flow) if applied improperly. Again, there are some recent laboratory data that support this method's ability to limit systemic spread of pit viper venom. The next issue was whether or not the arm should be packed in snow. I believe that a snake envenomation is the one form of envenomation in which ice therapy is relatively contraindicated. There is preliminary evidence that local cold therapy may drive certain deleterious components of snake venoms deeper into the tissues. The American Red Cross has come out with a formal policy statement that no local cooling measures should be used. Without a doubt, limiting the movement of the extremity with any available splint is advisable. The extremity should then be kept at heart level as much as possible. Elevating the extremity may speed central circulation ofvenom. Alternatively, keeping the extremity below heart level may worsen extremity swelling. Maintaining the extremity at heart level is a reasonable compromise. The use of antivenin is controversial in many respects. With the current antivenins available, there is little doubt that its use should be limited to a setting in which resources

3 218 Viewpoints are readily available for resuscitation in the event of an anaphylactic or anaphylactoid reaction. It is extremely rare that such a setting is available in the wilderness. This would require having the equipment to intubate patients, administer various catecholamines and antihistamines, and monitor the patient's cardiac function. If an expedition was truly entering a wilderness environment in which they would be many hours or days away from any form of medical care and properly trained personnel, it might be reasonable to use antivenin in a prehospital environment if all of the necessary resuscitative equipment was carried as well. The issue ofthe need to kill the snake for identification is often debated. In my mind, we should treat the snakebite, not the snake. As you are aware, the same polyvalent antivenin is used for all indigenous North American pit viper envenomations. The need to identify the offending reptile is, therefore, less important. There are instances (such as with the Mojave rattlesnake) where it would be nice to know the exact species involved, but, again, this is not absolutely mandatory. I think attempting to kill the snake has two significant disadvantages: It places the victim or the rescuer at risk for another bite (it should be remembered that even a decapitated snake head has a bite reflex for approximately 1 h) and it wastes valuable time that could be used to get the victim to definitive care. ROBERT L. NORRIS, MD Stanford, California, USA Recommended first aid for snake bite has changed through the years, but has generally been directed toward removing the venom and preventing systemic spread. The primary tenets of field management include removing the victim from the snake's striking range, reassurance, and rest. Alcohol and drugs should be withheld and the wound cleansed. The affected part should be immobilized in a functional position (in case of the arm, just below the heart), and the individual should be rapidly transported to the nearest medical facility for definitive care. Tourniquets have long been promoted to prevent the proximal spread ofvenom but are no longer recommended. Tourniquets occlude venous and arterial flow, leading to lymphedema, ischemia, necrosis, and gangrene. Further, the release of a tourniquet can lead to rapid dispersal of venom and tissue debris, causing hypotension and shock. A constriction bank to occlude only lymphatic flow may be useful. The band should be cm wide and placed 2-4 in. proximal to the bite, allowing enough room to slip one finger underneath. Distal pulses should remain palpable and capillary refill should be brisk. Although advocated in the past, incision and suction (oral-mechanical) are no longer recommended. Several problems have been noted with this form offirst aid. No controlled experiments have been done on humans, survival of experimental animals has not been affected, there is difficulty in locating the venom pool, and great damage can occur to underlying arteries, veins, tendons, and nerves. In addition, this unsterile technique can result in secondary infection. The Extractor delivers approximately 1 atmo of negative pressure. The pump should be applied within 3 min and left on for mins if possible. Cryotherapy, including ice or snow packing and cold sprays, is not recommended. Although ice may be effective at retaining venom at the inoculation site, rapid venom dispersal follows removal. Exposure to cold produces vasoconstriction in already compro-

4 Viewpoints 219 mised tissues. Prolonged exposure may result in gangrene, so that the victim ultimately requires amputation. Use of antivenin in the field is not recommended. Its use is confined to medical facilities where proper skin testing can be performed and an adequate assessment for the need for antivenin can be completed. Antivenin is administered in a diluted form intravenously at a amount necessary to control local and systemic systems. Although an attempt to identify the snake is warranted, history, physical, and laboratory examinations should be able to confirm a significant rattlesnake envenomation. There should be no time delay attempting to find and kill the offending snake, and a live rattlesnake should not be brought to the hospital. 1. Blackman, J.R. and Dillon, S. Venomous snakebite: past, present, and future treatment options. JAFP 1992; 5; Davidson, T.M., Schafer, S.F. and Jones, J. North American pit vipers. J Wilderness Med 1992; 3, Russell, F.E. Snake Venom Poisoning. Great Neck, NY: Scholium International, Russell, F.E. First-aid for snake venom poising. Toxicon 1967; 4, Sullivan, J.B. and Wingert, W.A. Reptile Bites. Management for Wilderness and Environmental Emergencies. St. Louis: CV Mosby, 1989; Wingert, W.A. First aid for pit viper bites. Wilderness Med Lett 1991; 8(3), Wingert, W.A. Editorial. Treatment for crotalid envenomation: conservative vs anticipatory. J Wilderness Med 1992; 3, JAMES BLACKMAN, MD Boise, Idaho, USA Rattlesnake bites rarely afflict careful wilderness travelers [1]. However, when a rock climber receives a rattlesnake bite on the dorsum of the hand, guidelines may be recommended. First, do no harm! First aid measures are not proven to decrease morbidity and mortality from rattlesnake envenomation. A case series of 227 rattlesnake bite victims found no difference in clinical course between patients who did and those who did not receive first aid [2]. However, this study had limitations of a retrospective design and lack of power analysis (I-beta) to determine the probability of avoiding a type II error [2]. Despite these limitations, the classical clinical dictum primum non nocere, "first do no harm," seems prudent advice when treating rattlesnake bites in wilderness settings. Several first aid measures, although not proven efficacious in man, are reasonable to use based on animal studies and clinical experience. These include immediately applying a suction venom extractor (e.g., The Extractor from Sawyer Products), placing the affected arm in a sling to decrease mobility, and rapidly evacuating the patient to the nearest hospital capable of administering antivenin and treating life-threatening anaphylaxis [2-6]. These methods lack limb-threatening complications that are possible with constriction bands and splints attached with circumferential bandages. Although some animal studies support using constriction bands and splints, their use in humans is prohibited due to lack of proven safety and efficacy [3,4,7]. An animal study showed systemic absorption of crotalid venom was decreased with constriction band therapy using a sphygmomanometer cuff. Cuff pressures were maintained at 45 mm Hg, with repeated cuff adjustments to avoid increasing constriction as the animals' legs swelled [7]. Continual cuff adjustments to avoid limb-threatening constriction would be difficult, if

5 220 Viewpoints not impossible, in wilderness settings. Another animal study found that pressure wrapping at 55 mm Hg and splinting decreased systemic absorption of Australian elapid venom [3]. However, elapid venom causes minimal tissue edema, in contradistinction to most crotalid venoms, which cause profound edema [3]. Also, this study showed that splinting alone or pressure wrapping alone did not limit systemic venom absorption [3]. Both techniques must be used simultaneously to limit venom absorption [3]. A later animal study using similar pressure wrapping and splinting showed decreased systemic absorption of eastern diamondback rattlesnake venom [4]. However, the high wrapping pressures would cause pain and could be limb-threatening if used in healthy adult rock climbers who could otherwise tolerate systemic absorption of crotalid venom with little risk of death. In fact, only one patient died in the case series of 227 rattlesnake bite victims [2]. That fatality occurred in an 80-year-old man who died of myocardial infarction 30 min after arriving at the hospital, and prior to receiving antivenom [2]. In addition to constriction bands and splinting, other field treatments are also not recommended. Fang marks should not be incised, because tendons and other deep structures could be lacerated. Mouth suction should not be used because human oral flora could cause a wound infection. The extremity should not be packed in snow or ice because cold injury could damage already compromised tissues. The hand should not be held above the head because this may facilitate proximal spread of venom. Antivenin should not be administered in the field due to the danger of life-threatening anaphylaxis that would be difficult to treat without intensive care drugs and equipment. The rattlesnake should not be killed for identification. Attempts to kill the snake could result in more bites to the patient or bites that would turn potential rescuers into patients; also, use of commercial crotalid antivenin does not require rattlesnake species identification. 1. Iserson, K.Y. Incidence of rattlesnake bite in wilderness rescue (letter). lama 1988; 260, Wingert, W.A and Chan, L. Rattlesnake bites in Southern California and rationale for recommended treatment. West 1 Med 1988; 148, Sutherland, S.K., Coulter, AR. and Harris, R.D. Rationalisation of first-aid measures for elapid snakebite. Lancet 1979; 1, Sutherland, S.K. and Coulter, AR. Early management of bites by the eastern diamondback rattlesnake (Crotalus adamanteus): Studies in monkeys (Macaca fascicularis). Am 1 Trop Med Hyg 1981; 30, Bronstein, AC., Russell, F.E., Sullivan, J.B. et al. Negative pressure suction in field treatment of rattlesnake bite (abstract). Vet Hum Toxicol1985; 28, Russell, F.E. Snake Venom Poisoning, 2nd ed. Great Neck, NY: Scholium International Inc., 1983; Burgess, J.L., Dart, R.C., Egen, N.B. and Mayersohn, M. Effects of constriction bands on rattlesnake venom absorption: A pharmacokinetic study. Ann Emerg Med 1992; 21, FRANK G. WALTER, MD, FACEP Tucson, Arizona, USA Editorial comment Four highly qualified experts form an impressive nearly unanimous consensus which can be summarized as follows: (1) Incision across fang bite. No. (2) Mouth suction. No.

6 Viewpoints (3) Venom extraction. Mild difference of opinion. (4) Venous constricting band. Not routine, but possibly useful. (5) Pack hand in snow. No. (6) Splint. OK. (7) Hand over head. No-at heart level. (8) Antivenin. Only in the hospital. (9) Kill the snake. No. The rarity offatalities and the evidence that the above measures appear to be of no value is a clear message. What about snake breeders and handlers? Is this a dangerous profession? A noted authority on poisonous snakes was bitten on the hand by a particularly venomous species and died within minutes. A fang had entered a vein, so an intravenous envenomation had occurred. 221 HERBERTN.HULTGREN,MD Stanford, California, USA