CLINICAL PEARLS ON SNAKEBITES & ANTIVENOM TREATMENT

1. Treat based on symptoms, not the snake.

Even if a patient says they were bitten by a dangerous snake (like a mamba), don’t give antivenom unless they show signs of envenomation (e.g., swelling, bleeding, or weakness). If a patient has symptoms but thinks the snake was harmless, treat them based on what you see.

2. Antivenom is the main treatment.

• Antivenoms are safe and effective and carry a low risk of allergic reactions compared to the high risk of venom damage. Many can be carried in the field at ambient tropical temperatures with no special storage required – these products are labeled as FREEZE-DRIED/UNREFRIGERATED in the antivenom product pages later in this document.

3. Use IV or IO routes only (not IM or SQ, even if the package says so). IV is best, but IO works in emergencies^.54,59

4. Antivenom dosage is not weight-based and there is no difference in dosing between adults and children.

5. Follow the dosing recommended in this CPG unless instructed otherwise by a DoD ADVISOR Toxicologist or other approved snakebite expert. DO NOT follow the package insert, as they rarely reflect clinical or evidence-based best practices.

6. Keep giving antivenom until symptoms stop getting worse (INITIAL CONTROL) – see Identifying Initial Control by Syndrome): pain will begin to improve; edema will stop progressing; all active bleeding will stop; vision, speaking, swallowing, and breathing will improve; and systemic instability will stabilize. Overdosing isn’t a concern, but watch for late allergic reactions (e.g., rash or fever) 1–3 weeks later, which can be treated with antihistamines or steroids.

7. Some snakebite patients will experience secondary recurrences (similar to polyphasic anaphylaxis) where control is lost and symptoms suddenly begin to worsen and progress again. This is usually within the first 0 - 6 hours after initial control but rarely can occur 24 – 48 hours later.

• This is why the control algorithm stacks more frequent assessments in the first hours after control is achieved: reassess q30 minutes for the first two hours after initial control is achieved

8. When control is lost and recurrence occurs, give additional doses of antivenom according to the appropriate treatment algorithm (NEURO or HEMO/CYTO).

• When control is achieved again, restart the 48-hour clock on the Control Algorithm for assessment intervals and disposition decisions. Symptoms must be controlled for 48 hours without signs of worsening progression before disposition can be achieved. When in doubt, consult a DoD toxicologist via the ADVISOR line.

9. DO NOT give test doses to check for allergies; they don’t work and waste time.^60–63 Pretreatment with IM epinephrine is the only effective means of reducing reaction risk, see Pretreatment to Prevent Reactions.

10. Track progression / evolution of symptoms over time. Write down the following:

• When the bite occurred (time/date) + time elapsed prior to arrival
• Speed and degree of progression between bite à presentation
• Time when the first dose of antivenom is given (defined as Hour 0, written as H0)
• Assessment and disposition instructions (including timing of repeated assessments) is detailed in the Control Algorithm.

11. Snakebites can change fast.

• A patient might start with only local pain or swelling (cytotoxic) but later develop systemic bleeding (hemotoxic) or progressive weakness (neurotoxic). Check for all three syndrome types at every assessment and adjust treatment as needed (see rapid assessment box in treatment/assessment algorithms). Consult a Medical Toxicologist as soon as possible.
• Within the United States, a Medical Toxicologist can be reached via a Poison Control Center by calling 800-222-1222. Within the Department of Defense, a Medical Toxicologist can be reached via the Advanced Virtual Support for Operational Forces (ADVISOR) teleconsultation service by calling 833-ADVSRLN (833-238-7756)/ DSN: 312-429-9089 and requesting a toxicology consult.

12. If a reaction occurs, see Antivenom Reactions Algorithm and Treatment of Adverse Reactions.