Snake Bite FAQ

Kyoto: Hiking from Kibune to Kurama

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Twenty-five percent of all pit viper bites do not result in envenomation and another 15 percent are so trivial, they require only local cleansing and tetanusprophylaxis.

Coral snakes lack retractable fangs. Instead they rely on fixed retroverted teeth to gnaw into the flesh of their prey. They must penetrate the skin long enough for their venom to be deposited around their teeth and into the wound. This envenomation mechanism is much less efficient than that of pit vipers; consequently, 50 percent of coral snakebites are dry.

The severity of the reaction to a snakebite depends on the degree of envenomation. Downey, Omer and Moneim describe a system whereby,

"grade 0 means there is no envenomation and indicates swelling anderythema [redness] around the fang marks of <2.5 cm, grade 1 indicates swelling and erythema of 2.5 to 15 cm but no systemic signs, grade 2 indicates swelling and erythema of 15 to 40 cm with mild systemic signs, grade 3 indicates swelling and erythema of >40 cm with systemic signs, and grade 4 indicates severe systemic signs including coma and shock."

In their series of 36 patients, there were no grade 0 bites, five grade 1 bites, 27 grade 2 bites, three grade 3 bites, and no grade 4 bites. So, this study suggests that most victims of snakebite will have a moderate local reaction with mild systemic signs. Life-threatening consequences such as shock are unlikely.

Signs And Symptoms

Gold and Wingert describe the signs and symptoms associated with anenvenomated snakebite:

"Panic is the most common reaction to a snakebite. As a result, the victim may become emotionally unstable with thoughts of imminent death, or conversely, the victim may enter a state of extreme lethargy and withdrawal. Fear may cause such symptoms as nausea, vomiting, diarrhea, dizziness, fainting, tachycardia [rapid hert rate], and cold, clammy skin. It is important that autonomic [flight or fight] reactions not be mistaken for systemic symptoms and signs resulting from a bite. Such an error could lead to unwarranted treatment. The primary local symptoms and signs of most pit viper envenomations are fang punctures, pain, edema [swelling], and erythema [redness] or ecchymoses [bruising] of the bite site and adjacent tissues. There may be one or more puncture wounds, depending on the number of fangs the snake had, the accuracy of the strike, and the number of strikes inflicted. Superficial lacerations produced by fangs do not usually result in envenomation, because the discharge orifice of the fang lies slightly proximal to the tip. Teeth marks, other than fang punctures, may or may not be present. There may be moderate pain in or around the local bite site in about 90 percent of pit viper envenomations. Exceptions are the bites from the Mojave rattlesnake and the speckled rattlesnake, which cause little or no pain. ...The pain, which had been described as sharp and burning in character, usually develops within 5 minutes after inoculation [injection] of the venom. Edema and erythema or ecchymoses are characteristic of pit viper envenomation and usually occur within 30 minutes of the bite, evolving both proximally and distally as the venom spreads. If edema and erythema have not manifested within 8 hours after a snakebite, it is generally safeto assume that the patient has not been envenomated. Frequently, there are signs of lymphangitis [inflammation of the lymphatic system] with tender regional lymphadenopathy [disease of the lymph nodes]. Frequent systemic manifestations after bites by eastern, timber, and western diamondback rattlesnakes are perioral parathesias extending to the face and scalp with tingling of the fingertips and toes. According to Russell, the most frequent diagnostic findings after bites by the Pacific rattlesnake arecomplaints of a 'minty,' 'rubbery', or 'metallic' taste in the mouth and 'tingling of the lips.' ...Skeletal muscle fasciculations [tics, spasms] in the bitten area, face, neck, and back may occasionally become generalized."

Snake bites are usually associated with some pain, although it may be minor and transitory in nature. Swelling is either absent or very minor. Parathesia [abnormal sensation] is sometimes noted around the bitten area,and some weakness of the part may become evident within several hours ofthe poisoning. The patient may complain of drowsiness, apprehension, andweakness. Muscular incoordination may develop, and muscle fasciculations [tics, spasms] and tremor of the tongue may be seen. Increased salivation and difficulties in swallowing and phonation [speech pronunciation], as well as visual disturbances, respiratory distress and failure, a bulbar [brainstem] type of paralysis, convulsions, and shock may develop."