Achieving Control
3 Areas of Pathological Impact
A single venom contains a wide array of toxins—necrotoxins, pre- and postsynaptic neurotoxins, and nephrotoxins, among others. This complexity, along with other biological factors, makes it difficult in clinical practice to predict specific effects of an individual envenomation.1,2*
However, all envenomations can exhibit some or all of the following effects1,2:
*Approximately 1 in every 4 bites is "dry," meaning no venom has been injected.
Watch Dr. Arnold discuss his experience with CroFab® and why initial control is extremely important.
| Local Effects1,2 |
| Pain and local soft tissue damage are the first symptoms of envenomation. Necrotoxins may produce clinical effects almost immediately postbite, resulting in tissue digestion and vascular permeability. |
| Edema |
- Is produced by permeable vessels, caused by venom, allowing fluid and blood to extravasate
- Is the first objective sign of envenomation and should prompt immediate attention
- Can progress to hypovolemic shock
- Decreases slowly with treatment and is therefore a poor indicator of clinical improvement
- Creates skin issues relative to the extent of the edema
- Loss of skin elasticity
- Skin stretches and fissures
- Fissures, while generally superficial, should be monitored as sources of secondary infection
|
| Ecchymosis |
- May occur with edema
- May indicate severity of envenomation by speed of progression
- Caused by bleeding into skin due to venom-induced coagulopathy
|
| Vesiculations and Bullae |
- May be filled with clear serous fluid (vesicles) or with blood (bullae)
- Develops most frequently in the bite area, but may be visible over the entire extremity
|
| Skin Necrosis |
- Can result from tissue destruction by venom proteins (snake venom metalloproteinases)
- May occur distal to bite site
|
| Potential Consequences |
- Partial or complete loss of affected limbs
- Loss of joint functionality
- Loss or impairment of tactile sensation
- Infection
- Cosmetic issues
|
| Systemic Effects1,2 |
| General systemic effects include: |
- Headache
- Diarrhea
- Nausea
- Syncope
|
- Vomiting
- Convulsions
- Abdominal Pain
- Metallic taste (likely due to metalloproteinases in the venom)
|
| Specific systemic effects include, but are not limited to: |
| Neurotoxic Paralysis |
- Caused by pre- and/or postsynaptic neurotoxins
- Presynaptic paralysis usually involves terminal axon damage. Reversal requires regeneration of axons, which takes days, weeks, or even months
- May take 1 to 12 hours to become evident
- Is progressive, often first seen in cranial nerves
- Is easily missed if not specifically sought in exam
- Is also evidenced early by ptosis, ophthalmoplegia, dysarthria, and/or dysphagia
- Can lead to respiratory failure
- Paralysis of the diaphragm may be delayed up to 24 hours post-bite
|
| Cardiac Effects |
- Hypo- or hypertension
- Bradycardia
- Tachycardia
|
| Potential Consequences |
- Death is a possibility
- Irreversible damage
- Respiratory compromise/failure
- Neurologic deficits
- Cardiovascular/pulmonary collapse due to shock
- End organ damage
|
| Hematologic Effects1-3 |
| The 3 hematologic effects of envenomation are: |
| Coagulopathy |
- Decreased fibrinogen levels
- Elevated International Normalized Ratio (INR) and Prothrombin Time (PT)
|
| Thrombocytopenia |
- Defined as less than 150,000 platelets/microliter (platelets <50,000 are considered clinically important)
- In severe pit viper envenomations, platelet counts may be undetectable
- Transfusion alone can produce transient improvement in coagulation parameters and platelet counts, but rarely has a sustained effect in the absence of adequate dosing of antivenom
|
| Bleeding |
- Oozing of blood from the bite site and ecchymosis of the surrounding tissue
- Nuisance bleeding, such as gingival bleeding or haemolacria, or more serious bleeding, such as significant epistaxis, gastrointestinal bleeding, intracranial hemorrhage
- Medically significant and spontaneous bleeding is rare
|
| Potential Consequences |
- Coagulation abnormalities (0.5%)
- Increased risk of bleeding complications
- Significant ecchymosis
- Anemia
|
Don’t let myths about envenomation treatment hinder judgment when time is crucial.
References:
1. Smith J, Bush S. Envenomations by reptiles in the United States. In: Mackessy SP, ed. Handbook of Venoms and Toxins of Reptiles. Boca Raton, FL: CRC Press; 2010:475-488. 2. Lavonas EJ, Ruha AM, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011;11:2. 3. Lavonas EJ, Khatri V, Daugherty C, Bucher-Bartelson B, King T, Dart RC. Medically significant late bleeding after treated crotaline envenomation: a systematic review. Ann Emerg Med. 2014;63(1):71-78. 4. Yip L. Rational use of crotalidae polyvalent immune Fab (ovine) in the management of crotaline bite.[comment] Ann Emerg Med. 2002;39:648–650.