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 makes it difficult in clinical practice to assess specific effects of an individual envenomation.*

However, all envenomations have effects in 3 critical—and potentially life- or limb-threatening—areas in common: Steps_CroFab-1.png

*Approximately 1 in every 4 bites is "dry," meaning no venom has been injected.
Local Effects
Pain and local soft tissue damage are the first symptoms of envenomation. Necrotoxins may commence clinical effects almost immediately postbite, resulting in tissue digestion and vascular permeability.
Edema
  • Is produced by the permeable vessels, caused by venom, allowing fluid and blood to extravasate
  • Is the first objective sign of envenomation and should trigger full attention
  • Can progress to become profound enough to cause hypovolemic shock
  • Decreases slowly with treatment, which makes it a poor indicator of clinical improvement
  • Creates skin problems relative to the extent of the edema – Skin loses elasticity, stretches, and fissures. Generally superficial, fissures can be sources of secondary infection
Ecchymosis
  • May occur with edema
  • May indicate, by speed of its progression, the severity of envenomation
  • Caused by bleeding into skin due to coagulopathy induced by envenomation
Vesiculations and Bullae
  • May be filled with clear serous fluid (vesicles) or with blood (bullae)
  • Usually develop in the bite area but may be seen over the entire extremity
Systemic Effects
General systemic effects include:
  • Headache
  • Diarrhea
  • Nausia
  • Syncope
  • Vomiting
  • Convulsions
  • Abdominal Pain
  • Metallic or Minty Taste*
Specific systemic effects include, but 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 – Paralyzes the diaphragm last - up to 24 hours postbite
Cardiac Effrects
  • Hypo- or hypertension
  • Bradycardia
  • Tachycardia
*Likely due to the metalloproteinases in the venom.
Hemostatic Effects
Coagulopathy is generally seen in moderate to severe envenomations. Despite the many varied hemostatic toxins, 3 basic syndromes are seen:
Incoagulable blood with bleeding tendency
  • Coagulopathy is insidious, beginning with persistent bleeding from the bite wound
  • Hemorrhage is evidenced by bleeding gums, hematemesis, melena, or hematuria
  • Punctures by line insertions or surgery may result in prolonged and significant bleeding
Incoagulable or poorly coagulable blood without clinically apparent bleeding  
Thrombotic tendency (unusual)