Morning Report: 10/11/2012

Today’s Morning Report is courtesy of Dr. White-McCrimmon!

Here’s the Case:

Notification phone rings: “Hi this is an EMS notification … we have a 42 year old male en route to the hospital who is actively seizing after a diamondback rattlesnake bite…ETA 10 minutes”. On arrival to the ED the patient is diaphoretic, responsive to painful stimuli only. VS 88/50 P122 R 12 O2 sat 88% on RA. Ext exam reveals mild erythema at LLE with possible puncture marks at the patient’s L heel. EMS tells you that the patient has no known medical history. He received Versed 10mg in the field prior to arrival. What do you do next?

Tell your junior to provide mouth suction at the bite site
Tie a tourniquet above the bite
Place the extremity below the level of the heart
Place ice at the bite site
Run around the ED yelling for your attending
None of the above.

Rattlesnake Envenomation

Background

Rattlesnakes (RS) are pit vipers (genera Crotalus and Sistrurus) which may be identified by a heat-sensing pit anterior-inferior to the eye and by a rattle at the tip of the tail (in all but one species).
Indigenous to North and South America

Epidemiology

RS bites account for the majority of venomous snake bites in US.
M>F; young adults mostly; ethanol use; intentional interaction (pet/abuse)
10-50% bites are dry (no clinical evidence of envenomation)
US mortality 0.28% with antivenin vs. 2.6% without anti-venin

Pathophysiology

Venom is usually injected into subcutaneous tissue via hollow movable fangs located in the anterior mouth. Less commonly intramuscular or intravenous injection occurs.
RS venom is composed of several digestive enzymes and spreading factors, which result in local and systemic injury.

Clinical findings include:

(local effects) (fang marks – 1, 2 or none), pain, erythema and edema progressing to ecchymosis and bullae) ; *mark border of advancing edema Q 15-20 minutes
(hematologic effects) defibrination with/without thrombocytopenia, hematemesis, hematochezia (serious bleeding uncommon)
(myotoxicity) local – compartment syndrome; systemic – rhabdomyolysis
neurotoxicity (i.e. weakness, parasthesias) with minimal local tissue effects
(general) shock, lethargy, fasciculation, taste changes (i.e. metallic taste), chest pain, dyspnea, N/V/D, syncope/near-syncope; rarely direct cardiotoxicity or allergy to venom

Workup

Labs: serum fibrinogen (low), elevated PTT, elevated fibrin split products, platelets (low), CK/Cr (elevated),electrolyte abnormalities
Imaging: plain films for retained teeth or fangs; head CT for headache or AMS in setting of severe coagulopathy

Treatment

Supportive care; IV, O2, monitor, hydration; Tdap; Keep extremity in NEUTRAL position
Evidence does NOT support negative pressure venom extraction (AKA mouth suction),incision across fang marks, lymphatic constriction bands/tourniquets, first aid techniques (i.e. ice, alcohol, etc.)
Fasciotomy for compartment syndrome
Administer antivenom for signs of envenomation progression or acute complications
Because CroFab is safer than Antivenin Crotalidae Polyvalent it is indicated even if only minimal or mild envenomation (no systemic/coagulation abnormalities)

Crofab – starting dose 4-6 vials (each vial is reconstituted with 10 ml of sterile water and mixed by continuous swirling), once mixed further dilute in 250 cc of NS. Start infusion at 50ml/h for 10 mins, then increase to 250 ml/h if no reaction occurs. Observe for control of evenomation for up to 1 hour.

Consult

Poison Control
ICU as indicated

Dispo

Dry bites should be watched for at least 8 hours and be given close follow-up
No contact sports, elective surgery or dental work for 2 weeks after bite
All patients with envenomation should be hospitalized
Close observation and measurement of swelling Q 1-2 h for 24 hours is recommended

Thanks Rashida! Leave any comments below.