Page 49 - JSOM Summer 2020

18. Serum sickness is characterized by flu-like symptoms ± rash using a new glass tube to confirm the result prior to antivenom
that typically develops between 1 and 3 weeks after anti- administration. 78,111,113,114,121
venom administration. It is rare with highly purified modern 2. H2, H4, H6, H12, H24: A previously normal coagulation test
antivenoms but may occur more frequently with some of the that changes to abnormal in the presence of any new symptoms
second and third line antivenoms listed in this CPG. 94–97 meets criteria to administer an additional dose of antivenom.
a. Serum sickness may be uncomfortable but is not danger- This also applies to a WBCT that was abnormal, normalized
ous. Management is either symptomatic or with a course several hours after antivenom, but then changes to abnormal
of oral steroids. 94,95,97–99 again later (recurrent envenomation). 78
3. Coagulopathy remains abnormal at H24: If WBCT or other
tests of coagulation remain abnormal at H24, administer an
Specific Criteria for Initial Antivenom Treatment additional dose of antivenom and repeat every 24 hours until
and Repeat Doses resolution of coagulopathy has occurred.
Cytotoxicity: The presence of significant local pain OR progressive Sudden collapse syndrome: In rare cases, a patient may rapidly
edema OR signs of tissue destruction (bruising, blistering, necrosis) deteriorate in the first 5–30 minutes after the bite and present with
is an indication for initial administration of antivenom. 1,47,48,79,100–105 profound hypotension, tachycardia, angioedema, altered level of
If any of these criteria (or other systemic signs and symptoms) are consciousness, etc.. 1,122–130 These patients should be aggressively
present, treat immediately and do not wait for irreversible dam- treated for severe anaphylaxis and severe envenomation simulta-
age to occur before deciding to give antivenom. Note that the neously. Treat anaphylaxis aggressively according to anaphylaxis
progression of edema at any treatment interval is an indication to protocols. Treat the envenomation with an initial high dose (at
administer additional antivenom; however, edema may not begin least 6 vials) of antivenom by rapid IV push, and support the pa-
to noticeably decrease for several days and severe edema may take tient with airway management, fluids, and other interventions as
1–2 weeks or longer to completely resolve. WORSENING edema appropriate. 122,123,125,131,132 Most patients presenting with hypoten-
is therefore a treatment criteria, persistence of edema without any sion or angioedema are responsive to epinephrine, but may re-
progression IS NOT a treatment criteria. Worsening pain that in- quire IV epinephrine infusions to achieve this effect if they are
creases significantly in severity or moves proximally up the limb is unresponsive to IM epinephrine. 122
another indicator for antivenom treatment.
Neurotoxicity: The onset, persistence, or resumption of systemic
neurotoxic signs of envenomation (dyspnea, neck flexor muscle Sudden Collapse Syndrome Treatment Protocol
weakness, bulbar muscle weakness, reduced level of consciousness, 1. Patient presents within 30 minutes of the bite with rapid onset
↓ respiratory muscle function, etc.) at any of the antivenom treat- shock ± angioedema, altered mental status, systemic bleeding,
ment intervals is always an indication to administer or re-adminis- and diarrhea 1,122–130
ter antivenom. 1,49,106–108 Monitor respiratory function using negative a. Stabilize with IM or IV epinephrine and fluids as per ana-
inspiratory force (NIF) or forced vital capacity (FVC), single breath phylaxis protocols
count test (SBC), capnography, spirometry, peak flow meters, i. Intubate for airway edema not rapidly responsive to
etc. 1,54,72 In patients who have not reached the late stages of respira- epinephrine
tory distress/arrest, the first indications that paralysis is improving b. Follow epinephrine immediately with a high dose of the ap-
may be apparent within 30–60 minutes once the right dose of an- propriate regional antivenom given by rapid IV or IO push
tivenom has been achieved. In patients who are already intubated, during the resuscitation
it may take hours for reversal to occur after antivenom. This typ- c. Maintain blood pressure with IV or IO fluids and epi-
ically occurs within 1–3 hours but may take 6–12 hours or longer nephrine until antivenom has taken effect to reverse the
in some patients. There are numerous documented cases of patients hypotension
who did not receive antivenom and required prolonged mechanical
ventilation ranging from several days up to 13 weeks before re-
covery. Antivenom typically either reverses the syndrome before it Pretreatment With Epinephrineto Prevent
progresses or dramatically shortens the duration of paralysis. Early Adverse Reactions
Epinephrine is the only prophylactic treatment (pretreatment) that
Bleeding: The onset, persistence, or resumption of any active local has been shown to effectively reduce the incidence of early ad-
or systemic bleeding at any of the standard assessment intervals verse reactions (EARs) such as anaphylaxis. 60,98,133–136 DO NOT
(0, 2, 4, 6, 12, 24 hours) is always an indication to administer pretreat with steroids or antihistamines. DO NOT administer test
or readminister antivenom regardless of the WBCT result at the doses of antivenom to check for hypersensitivity. 60–63
time. 1,70,78,106,109–111 All external and internal bleeding will cease
when the appropriate dose of antivenom has been given and ac- Pretreatment Guidelines for Preventing Early
tively circulating venom has been neutralized. Adverse Reactions (EARs) to Antivenom
Relative contraindications to epinephrine pretreatment include
Whole blood clotting test (WBCT) and other tests of coagulation:
Tests of coagulation usually normalize within 2–6 hours after the age > 70, hypertension, ischemic heart disease, history of stroke,
suspected or confirmed intracranial hemorrhage. No absolute
effective dose of antivenom has been achieved but in some cases it
may take longer for these labs to fully normalize after antivenom contraindications.
1. Pretreatment with epinephrine prior to antivenom administra-
therapy. 78,112–120 WBCT procedure and interpretation is covered
in Appendix A: Whole Blood Clotting Test (WBCT) for Venom- tion is not indicated by default for all antivenoms, and is rec-
ommended only under the following circumstances:
Induced Consumptive Coagulopathies (VICC). There are three sit-
uations where an abnormal WBCT or other abnormal laboratory a. Unstable snakebite patients with signs of shock.
b. Known history of atopy (asthma, eczema, etc.), equine hy-
tests of coagulation (e.g. fibrinogen, PT/PTT/INR, etc) should be
persensitivity, or severe reactions to antivenom in the past.
treated with antivenom: c. Use of certain second or third line antivenom due to the
1. Initial assessment at H0: Coagulopathy after a snakebite is an
indication to give antivenom. If the coagulation test is abnor- high rate of serious EARs associated with these products.
Refer to Appendix B for specific recommendations for each
mal but the patient is otherwise asymptomatic, repeat the test
product.
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