Fort Worth, Texas,
02:57 AM

After the bite: When and why antivenom is used

Cook Children’s pharmacy explains how we fight venomous snake bites

Rattlesnakes, cottonmouths and copperheads account for 99 percent of the venomous snakebites in the United States. All three of those snakes can be found in Texas.

From 2010 to present, 167 patients were treated for snake bites at Cook Children’s. Cook Children’s provided care for six patients in May and five more in June 2018.

When children are taken to Cook Children’s Emergency Department, a careful snake bite protocol begins that can result in antivenom given to the patient.

"We have advance practice providers with years of experience and expertise in caring for snakebite victims as part of the Trauma Team," said Melinda Weaver, Trauma Program Manager at Cook Children's. 

The Trauma Team uses an evidenced based clinical guideline along with a scoring system, lab results and other indicators to decide if the antivenom is needed or not. If it's determined the antivenom is needed, the Cook Children's Pharmacy team is notified.

The Cook Children’s Pharmacy carries one of the largest stocks of an antivenin, Crofab®, a snakebite antivenom treatment, in the area for rattlesnake, copperhead and water moccasin (cottonmouth) bites at all times.

Once the patient is brought to Cook Children’s, he or she is watched carefully for signs and symptoms to a venomous bite.

The initial evaluation of the patient includes the “A-B-Cs” (airway, breathing, circulation) and vital signs. The wound is then examined for swelling, discoloration and bleeding. Signs that the antivenom is needed include:

  • Respiratory distress
  • Nausea
  • Vomiting
  • Abdominal pain
  • Bleeding from nose, skin or gums
  • Tingling or prickling sensations
  • Abnormally low blood pressure
  • Faster than normal heart rate.

Ean Miller, a pharmacist and pediatric clinical specialist in the Emergency Department at Cook Children’s, said the signs that Crofab will be needed usually occurs within the first couple of hours.

“Once we know it’s a snake bite, we are immediately drawing the labs,” Miller said. “We will assess the bite wound. One of the things that we watch for is if the redness and swelling around the bite starts to expand rapidly. If it’s not a venomous snake, usually there will be a little bit of redness and swelling but it doesn’t spread."

The initial care is administered by the Emergency Department and then the Trauma team at Cook Children’s takes over for treatment. An order is given if it’s determined the child needs the antivenom. The mixing takes 15 to 20 minutes by the pharmacist to get the antivenom ready.

The most important factors to giving CroFab are evidence of coagulopathy (blood clotting factors out of normal range) and evidence of respiratory distress, low blood pressure and fast heart rate.

If the patient responds to the initial dose and no allergic reaction occurs then an additional two vials will be given every six hours for three more doses.

Miller said 90 percent of patients start to improve after that first four to six vials of Crofab. Most of remaining 10 percent show improvement after an additional four to six for an almost 100-percent rate.

On rare occasions, a patient will develop an allergic reaction to the antivenom. If that happens, the patient cannot receive any more antivenom and treatment consists of symptomatic and supportive care.

Antivenom is not effective for the other venomous snakes in this country. Coral snakes, which also are in Texas, and other exotic species make up the remaining 1 percent of venomous snake bites in this country. Crofab® antivenom is not used to treat these bites. Patients are admitted to the hospital for 24-hour observation and supportive care.

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