In the event of an actual or probable bite from a Gaboon Viper, execute the following first aid measures without delay.

Snake:

1. Make sure that the responsible snake or snakes have been appropriately and safely contained, and are out of danger of inflicting any additional bites.

Transportation:

1. Immediately call for transportation.

   Telephone

Victim:

1. Keep the victim calm and reassured. Allow him or her to lie flat and avoid as much movement as possible. If possible, allow the bitten limb to rest at a level lower than the victim's heart.

2. Immediately wrap a large crepe bandage snugly around the bitten limb starting at the site of the bite and working proximally up the limb (the full length if possible). The bandage should be as tight as one might bind a sprained ankle.

3. Secure the splint to the bandaged limb to keep the limb as rigid and unmoving as possible. Avoid bending or moving the limb excessively while applying the splint.

4. DO NOT remove the splint or bandages until the victim has reached the hospital and is receiving Antivenom.

5. Have the SAIMR (South African Institute for Medical Research) polyvalent antivenom ready for the Lifeflight crew to take with the victim to the hospital. Give them the following:
   1. the available antivenom (at least 10 vials)
      
   2. the accompanying instruction (Protocol) packet
      
   3. the victim's medical packet

DO NOT cut or incise the bite site
DO NOT apply ice to the bite site

The bite of the Gaboon Viper with subsequent envenomation is a medical emergency and can be fatal if the patient is not treated appropriately. Please read the attached Medical Management Protocol and respond appropriately.

1. First Aid:
   1. Bandage and immobilize the bitten limb with crepe

      bandages and splint as described in the Immediate First Aid section. Rest this extremity below the level of the patient's heart (if practical).

   2. Transport to U.C.S.D. Medical Center Trauma Service.

2. Medical Management:
   1. Call your local Poison Control Center, or the San Diego Regional Poison Control Center (800 876-4766). They should locate a consultant to help you treat this patient.

   2. Observe for Signs and Symptoms of Envenomation.

   3. If significant systemic signs or symptoms are present, perform the following:
      1. Administer Lactated Ringers Solution at 200 to 250 mls per hour.

      2. Draw samples and collect initial laboratory data.

      3. Dilute the contents of 5 vials of SAIMR Polyvalent Antivenom in Lactated Ringers Solution to a total volume of 300ml. Administer the antivenom I.V. piggyback over 75 minutes at a rate of 240ml/hour (i.e. one vial per 15 minutes). The combined rate of diluted antivenom and Lactated Ringers Solution is now approximately 500ml/hour. The rate of Lactated Ringers Solution may be adjusted accordingly to avoid fluid overload, however a brisk urine output should be a treatment goal.

      4. When one complete vial has been infused (i.e. 15 minutes, 60 cc), remove the splints and crepe bandage slowly over a period 10 minutes. If symptoms progress rapidly, reapply the bandage, wait 10 minutes, and then again release the bandage slowly over 10 minutes while antivenom administration is continuing.

      5. Allergic or untoward reactions to the antivenom should be treated with Benadryl, Epinephrine, and/or Corticosteroids. A patient with known sensitivity to horse serum may be pretreated with 1 gm of Solumedrol, administered I.V. push.

      6. Monitor Signs, Symptoms, and Laboratory data, and administer additional antivenom in 1 vial increments at a rate of one vial every 15 minutes as necessary to control the progression of symptoms.

      7. The required amount of antivenom will vary with the severity of envenomation. One should anticipate using (including the initial dose):
         5 vials for a minor bite with envenomation

         10 vials may be necessary for moderate or severe bites.

This person has received a bite and probable envenomation from a Gaboon Viper (Bitis gabonica). This is a very venomous and dangerous snake native to high rainfall areas of West, Central, and East Africa. Although there are no documented deaths from the bite of the Gaboon Viper, many of the complications from envenomation are life threatening.

Please read and execute the following procedures without delay.

1. A crepe bandage and splint have been applied as immediate first aid adjuncts to retard the absorption of the venom. DO NOT remove until the patient has arrived at the hospital and is receiving the antivenom.

2. Make sure 10 vials of SAIMR Polyvalent Antivenom are present with the patient. This antivenom is specific and is only available directly from the San Diego Zoo Reptile Department. Refrigerate the antivenom upon arrival to the hospital.

3. If the patient has been envenomated, the treatment is at least 5 vials of intravenous antivenom. Envenomation is diagnosed by the presence of characteristic signs and symptoms. Necessary information follows and is organized into the following sections:
   Signs and Symptoms of Envenomation
   
   Medical Management
   
   General Considerations
   
   Special Considerations
   
   Consultants
   
   References

Signs and Symptoms of Envenomation:

1. Local Affects:
   Pain and swelling: onset almost immediately after bite
   
   Blistering, bleb formation
   
   Hemorrhagic edema
   
   Tissue necrosis: onset usually days after bite
   
   Ecchymosis

2. Cardiovascular:
   Severe Hypotension: onset immediately
   
   Cardiac arrythmias:
   
   Tachycardia
   
   Prolonged QT intervals
   
   Supraventricular tachycardia
   
   Inverted T waves
   
   Cardiac arrest

3. Hematological:
   Coagulation defects
   
   Spontaneous bleeding:
   
   Mucosal bleeding
   
   Hematemesis
   
   Epistasis
   
   Ecchymoses/petechiae
   
   Gastrointestinal bleeding
   
   Internal hemorrhage
   
   Hemolysis

4. Pulmonary
   Pulmonary edema
   
   Tachypnea
   
   Dyspnea

5. Renal/Urinary
   Hematuria
   
   Hemoglobinuria
   
   Myoglobinuria
   
   Renal failure

6. General:
   Nausea/Emesis
   
   Fever
   
   Abdominal pain
   
   Regional Lymphadenopathy

7. Fang Marks: The presence of fang marks does not always imply envenomation as the Gaboon Viper is known to bite without injecting venom into the victim. However, the absence of fang marks does not necessarily preclude the possibility of a bite, nor does it give any indication of the severity of the bite. Fang marks may be present as one or more well defined punctures, as a series of small lacerations or scratches, or there may not be any noticeable or obvious markings where the bite occurred. Finally, multiple bites inflicted by a single snake are possible and should be noted if present.

   Those signs and symtoms which give strong evidence for systemic envenomation include hypotension, dyspnea, cardiac arrythmias, spontaneous bleeding, and local swelling of more than half the affected limb. Antivenom should be administered without delay in such cases.

Medical Management:

1. Admit patient to the Trauma Service and call consultants listed on the last page. Terence M. Davidson, M.D. is the local consultant for snake bites, and should be notified immediately.

2. Begin a peripheral intravenous infusion (16 gauge catheter) of Lactated Ringers Solution at a rate of 250 cc/hour.

3. Draw blood from the contralateral arm, and collect urine for the following laboratory tests. Mark STAT.
   1. Type and Cross Match TWO units of Whole blood.

   2. CBC with differential and quantitive platelet count.

   3. Coagulation Parameters:
      1. Prothrombin Time (PT)
         
      2. Partial Thromboplastin Time (PTT)
         
      3. Fibrinogen Levels
         
      4. Fibrin Degradation Products

   4. Serum Electrolytes, BUN/Creatinine, Calcium, Phosphorus.

   5. Lactate Dehydrogenase (with Isoenzyme analysis). Isoenzyme analysis may indicate multiple targets of the venom components which may dictate further management.

   6. Urinalysis (Macroscopic and Microscopic Analysis).

      Must include analysis for:

      1. Free Protein
         
      2. Hemoglobin
         
      3. Myoglobin

   7. Electrocardiogram (Sinus Tachycardia would be expected).

   8. Continuous Urine Output Monitoring (In-dwelling Foley Catheter if unconscious). Watch for possible oliguria or anuria.

   9. Additional tests as needed or indicated by the patient's hospital course.
      1. The patient's vital signs should be monitored frequently over the first 48 hours after the bite for evidence of circulatory shock.

      2. It may be necessary or practical to repeat some of the above serum and urine tests over the hospital course to monitor the effects of antivenom therapy or to detect late changes in laboratory values.

4. OBSERVE PATIENT CLOSELY for signs and symptoms of envenomation which usually manifest between 15 minutes and two hours after the bite occurred.
   1. If NONE of the signs or symptoms have been noted after TWO hours, there is the possibility that the patient received a dry bite (no venom injected).
      1. VERY SLOWLY begin to remove the bandages and splint watching carefully for any changes in the patient's status. If any changes occur, assume the patient has been envenomated and prepare to give antivenom immediately (as directed below).

   2. If signs and symptoms still fail to manifest, continue CLOSE observation of the patient for an additional 12 to 24 hours.

5. IF SIGNIFICANT SYSTEMIC SIGNS OR SYMPTOMS become apparent, begin antivenom therapy as follows:
   1. Dilute the contents of 5 vials of SAIMR Polyvalent Antivenom in Lactated Ringers Solution to a total volume of 300ml. Administer the antivenom I.V. piggyback over 75 minutes at a rate of 240ml/hour (i.e. one vial per 15 minutes). The combined rate of diluted antivenom and Lactated Ringers Solution is now approximately 500ml/hour. The rate of Lactated Ringers Solution may be adjusted accordingly to avoid fluid overload, however a brisk urine output should be a treatment goal.

   2. Should any signs of ALLERGY/ANAPHYLAXIS (e.g., coughing, dyspnea, urticaria, itching, increased oral secretions, etc.) develop, immediately discontinue the administration of antivenom, and treat symptoms with Corticosteroids, Epinephrine, Benadryl, Atarax and/or Antihistamines. As soon as the patient is stabilized, continue the antivenom infusion at a slower rate. (i.e. 120ml/hour).

   3. After 15 minutes of antivenom administration, the splint and the bandages may be removed. This should be done VERY SLOWLY over a period of 10 minutes to prevent a bolus release of venom. If the patient's condition worsens, reapply the crepe bandage, wait 10 minutes and release the bandage again slowly over 10 minutes while antivenom administration is continuing.

6. Antivenom Therapy is the mainstay of treatment for Gaboon Viper snake envenomation. Many of the symptoms are ameliorated or entirely eliminated by the antivenom alone. Other symptoms will require additional therapeutic modalities in order to be corrected.
   1. Cardiovascular status: Gaboon Viper venom is known to be cardiotoxic and causes arrythmias as well as decreases in stroke volume and cardiac output. In addition the venom results in a lowering of peripheral vascular resistance and thus gives rise to hypotension. The administration of antivenom alone will dramatically improve hypotension and signs of circulatory shock provided the patient is not volume depleted. Intravenous administration of Lactated Ringers Solution is warranted if the patient is hypovolemic but is only efficacious if antivenom has been administered. Cardiac arrythmias, specifically prolonged QT intervals, inverted T waves, and supraventricular tachycardia may persist for days after the initial envenomation. Severe arrythmias may require the use of a temporary pacemaker to ensure adequate cardiac output and to prevent cardiac arrest.

   2. Hematological signs and symptoms: Gabbon Viper venom has a thrombin-like enzyme which quickly depletes serum fibrin levels thus rendering the blood incoagulable. In addition the venom has hemorrhagic activity as it causes widespread damage to the microvasculature. Of note, the lungs and gastrointestinal tract are extremely sensitive to this hemorrhagic activity. Finally, disseminated intravascular coagulopathy and anemia may also occur. The patient should be monitored closely and blood products including whole blood, packed RBC's platelets, cryoprecipitate, and fresh frozen plasma should be given when indicated.

   3. Pulmonary: The hemorrhagic activity of the venom results in pulmonary edema, tachypnea, and dyspnea.

   4. Renal: The hemorrhagic activity of Gaboon Viper venom may result in hematuria. In addition, hemoglobinuria and myoglobinuria may likewise affect renal function, and if severe, (Acute Renal Failure), may necessitate peritoneal dialysis.

   5. Laboratory: Gaboon Viper venom has been noted to cause transient increases in serum SGOT, SGPT, and LDH levels suggesting damage to liver and kidney tissue.

   6. Neurological symptoms are uncommon with Gaboon Viper bites. Respiratory distress is nearly always secondary to pulmonary edema rather than muscle paralysis.

7. It is important to keep venom neutralization current and continuous. The best method to accomplish this is to monitor the patient's status. If the present condition does not improve, or should it worsen for any reason, additional antivenom should be administered. Give all additional antivenom in one vial increments. Dilute the antivenom in Lactated Ringers as before and administer the antivenom I.V. piggyback over approximately 15 minutes.

   BITES WITH ENVENOMATION REQUIRE AT LEAST 5 VIALS BUT SEVERE ENVENOMATIONS MAY REQUIRE UP TO 10 VIALS OF ANTIVENOM.

8. It is advisable to perform periodic serum and urine analyses during therapy (as outlined above).

9. It is always best to keep the patient in an Intensive Care setting until free of major symptoms for 24 hours. The patient should be observed in the hospital for at least 24 hours after all symptoms abate.

General Considerations:

1. It is important that the patient remain resting and warm. Avoid unnecessary movement.

2. Symptom variability: As noted already there is marked symptom variability in response to a Gaboon Viper bite. It is important to note the progression of symptoms throughout the course of therapy and give additional antivenom as necessary to titrate these symptoms.

3. Respiratory Failure: Pulmonary edema and subsequent dyspnea may necessitate the use of supplemental oxygen. If severe, the use of a ventilator may be indicated.

4. Cardiac Arrest: The cardiotoxic nature of Gaboon Viper venom necessitates careful monitoring of the patient's cardiac status the first 24-48 hours after envenomation.

5. Fluid Management: The patient should be well hydrated, and a brisk urine output should be maintained. Blood products should not be given until circulating venom has been neutralized with antivenom.

6. Compartment Syndrome: It should be noted that fascial compartment syndromes in Gaboon Viper bites are uncommon. Limbs may swell significantly, but rarely involve specific fascially bound compartments. If however the logistics of the bite raise a high index of suspicion for a compartment syndrome, monitoring with a Wick Catheter or appropriate pressure device may be necessary. Fasciotomy is rarely, if ever, recommended in these patients.

7. Tetanus Prophylaxis should be current.

8. Antibiotics are not recommended prophylactically.

9. Antivenom is the best treatment for all signs and symptoms of Gaboon Viper bites and should be utilized prior to other treatment modalities.

Special Considerations:

1. Multiple Bites:

   1. It is possible for a Gaboon Viper to deliver more than one bite in a single attack. If there is evidence that such an attack occurred (i.e., history or multiple bite sites), give the initial dose of 5 vials but be prepared to give a total of 10 vials to adequately treat the bite. Titrate antivenom administration to signs and symptoms as discussed previously.

2. Testing for Equine Protein Sensitivity:
   1. It is NOT ADVISABLE to utilize subcutaneous or intradermal testing for sensitivity to equine products in that such testing may be unreliable, and may unnecessarily delay antivenom therapy which must be used if any signs of Gaboon Viper envenomation are present.

   2. If there is reason to believe that the patient may be sensitive to equine protein products:
      1. Premedicate the patient with 1 gm Solumedrol, administered I.V. push. Assuming the patient's condition is stable, wait 15-30 minutes before administering the antivenom.

      2. Administer the diluted antivenom at a rate as tolerated by the patient beginning at a rate of 120ml/hour (as opposed to the normal 240ml/hour rate). If the patient tolerates this, increase the rate up to 240ml/hour.

      3. Monitor Pulse and Blood Pressure carefully. Be prepared to treat for Anaphylaxis.

3. Clinical Experience with the Gaboon Viper:
   1. There are very few documented cases of Gaboon Viper bite envenomation in the literature. As such, other complications of envenomation may occur which have previously not been described.

   2. The Gaboon Viper (Bitis gabonica) is considered to produce more venom than any other venomous snake. A single adult animal may have enough venom to inject lethal doses into 30 individual men. Despite these statistics, the Gaboon Viper is noted for its docile nature and this may account for the very few reported bites in the literature. Although no documented deaths have been attributed to Gaboon Viper bites, the snake should not be considered less dangerous as many of the complications of envenomation are life threatening.

   3. Prompt recognition of clinical envenomation and adequate amounts of antivenom delivered early in the treatment course will facilitate a good recovery. The use of at least 5 vials of antivenom reduces the incidence of serious complications.

References:

The following references are recommended for further reading. This material includes case histories, guidelines and recent findings in treatment of Gaboon Viper bites. These should be read only after treatment has begun, and the patient is stable.
1. Marsh, N.A., Whaler, B.C., The Gaboon Viper (Bitis gabonica): its biology, venom components and toxinology, Toxicon 22, 669-694, 1984.