Surgeons are often consulted for snakebite patients, but envenomations are medical, not surgical, emergencies. For many years, an aggressive surgical approach, including wound debridement, fasciotomy, and, occasionally, amputation, was recommended. The authors of a 1976 article in the Journal of the American Medical Association claimed that “early surgical inspection of the snakebite wound is as essential as early appendectomy in appendicitis.” 56 They further argued that disability from snake envenomation was due to insufficient surgical management and a reliance on noninvasive treatment. Ironically, multiple studies have since demonstrated that surgical intervention is fraught with complications and leads to disability and disfigurement. Velmahos et al. cited a 31% complication rate following fasciotomy. 57 Long-term sequelae such as dysesthesias, swelling, and tethered scars were observed in more than 75% of surgical patients in a different study. Animal studies prove that morbidity and mortality increase following prophylactic fasciotomy when compared to antivenom. 58,59 In a review of 99 publications evaluating the efficacy of fasciotomy in animals and humans, the author could not identify any situation in which surgical intervention was beneficial. 60 An expert panel consisting of trauma surgeons and medical toxicologists also concluded that prophylactic fasciotomy was not beneficial and was possibly harmful. 30 The same authors concluded that, even in the exceptionally rare case of confirmed compartment syndrome, the initial treatment should be additional doses of antivenom, not fasciotomy. The rationale, supported by animal studies, is that elevated compartment pressure represents a severe envenomation but is not the cause of the morbidity. Rather, it Coral snake envenomations Coral snakes are in the Elapidae family, which, worldwide, includes snakes such as cobras, kraits, mambas, and taipans. Three coral snake species account for approximately 2% of bites from native venomous snakes. Micruroides euryxanthus , the Sonoran coral snake, is found in Arizona and western New Mexico. Micrurus tener , the Texas coral snake, is native to Texas, southern Arkansas, and western Louisiana. Micrurus fulvius , the Eastern coral snake, can be found in Florida, Alabama, Mississippi, eastern Louisiana, Georgia, and North and South Carolina. Figure 8. Texas Coral Snake (Micrurus Tener)
is the venom that is causing the damage, and neutralizing the venom is the definitive treatment. Delayed surgical intervention is occasionally necessary following snakebite. Fasciotomy is warranted for the rare confirmed compartment syndrome that, even more rarely, fails to respond to appropriately dosed antivenom. Surgery is also indicated when there is full-thickness necrosis requiring amputation. Premature surgery must be avoided, however, because many patients with superficial necrosis will recover fully if managed with conservative wound care. Some experts advocate the use of a colloidal silver bandage with or without debridement, while others recommend twice-daily application of a petrolatum- containing ointment. If patients have no clinical or laboratory evidence of pit viper envenomation, they may be discharged after eight hours. Patients should be monitored for at least 12–24 hours if there is any evidence of an envenomation. Patients should follow up with their primary care provider or a snakebite expert within three to five days after hospital discharge. Routine lab testing is recommended for patients who were found to have hematotoxicity and those with rattlesnake envenomations because of the potential for delayed hematologic abnormalities. Patients who are discharged after a pit viper envenomation should also be instructed to elevate the extremity when possible and avoid weight-bearing on the affected extremity for several days, or longer if signs and symptoms persist. Pain should be controlled with acetaminophen or, if necessary, opioids. NSAIDs should be avoided because of the potential hematologic effects. Coral snakes are slender with narrow round, black heads. They have round pupils and fixed front fangs. Typically, coral snakes have alternating bands of red, yellow, and black. The distinctive coloration has led to several mnemonics that are often used to distinguish coral snakes from nonvenomous mimics. “Red on yellow, kill a fellow. Red on black, venom lack” is often true of native coral snakes, but there are multiple aberrant patterns that make reliance solely on the rhyme dangerous. Additionally, some people recite the rhyme incorrectly, placing themselves and/or others at risk. There are also nonvenomous mimics that have red bands touching yellow bands, such as shovel-nosed snakes from the genus Chionactis . Finally, nonnative coral snakes have a variety of patterns and colors that render the mnemonic inaccurate. Similar to that of pit vipers, coral snake venom is complex. However, unlike crotalids, coral snake venom is primarily neurotoxic, containing a variety of phospholipases A 2 and three- finger toxins. 61 The proteases that cause tissue injury and various compounds contributing to the hematologic abnormalities observed in crotalid envenomation are conspicuously absent or found in extremely low concentrations. Not all coral snake bites lead to envenomation. It is estimated that approximately 30%–50% of coral snake bites are “dry,” which is likely due to a combination of coral snakes’ relative shyness and the fangs being smaller and less mobile than crotalid fangs. 62-64 Pain is often present immediately after an envenomation, but some clinical features may not manifest for up to 12 hours or more. 62-65 Unlike in crotalid envenomations, local findings are insignificant following a coral snake envenomation. There may be slight erythema, but ecchymosis is absent. Edema is mild and confined to the bite site; there is no progressive swelling of the affected extremity. Paresthesias are common and frequently extremely painful. 62-64 Sonoran coral snake envenomations can cause superficial muscle twitching but usually little else. In a 1967 case series of four bites, two patients had transient general weakness and another subject had weakness along with lid lag, nausea, confusion, and hand clumsiness. 66
Source: Justin Doll
Page 20
Book Code: RPTTX2024
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