Operational Medicine 2001
Field Medical Service School
Student Handbook

ENVENOMATION INJURIES

DRAFT

FMST 0405

01 Nov 99

TERMINAL LEARNING OBJECTIVES: 1.  Given an envenomation casualty in a combat environment (day and night) and the standard Field Medical Service Technician supplies and equipment, manage envenomation injuries per the references.  (FMST 0405)

ENABLING LEARNING OBJECTIVES:

1.      Without the aid of reference materials and given a list of treatments for snake bites, identify appropriate treatment per, the student handbook.  (FMST .04.05a)

2.      Without the aid of reference materials, and given a list of descriptions of arachnids, identify the species, per the student handbook.  (FMST .04.05b)

3.      Without the aid of reference materials and given a list of treatments for arachnid bites, match the treatment with the species, per the student handbook.  (FMST .04.05c)

4.      Without the aid of reference materials and given a list, identify the correct definition of envenomation injury, per the student handbook. (FMST .04.05d)

5.      Without the aid of reference materials and given a list of symptoms, determine the correct venom category of the snake envenomation injury, per the student handbook. (FMST .04.05e)

6.      Without the aid of references, given the Molle Medical Bag, and a simulated envenomation casualty, identify, treat, and manage the casualty, per the student handbook.  (FMST .04.05f)

OUTLINE:

I.  Envenomation Injuries

A.     Definition:  Envenomation Injuries -An injury caused by a reptile, animal, or           

insect in which venom is the prime cause of illness.

B.     Mortality Rates:  Of all the deaths per year due to bites, 40% are caused by insect          

bites, 33% are caused by snake bites, 18% are caused by spider bites.

II.                 Snake Envenomations

A.  Classification of poisonous snakes:

1.      Crotalidae (Pit Vipers)

a.  Characteristics:  retractable fangs, heat sensing pit located below the nostril,  large (in relation to width of body) triangular shaped head.

                              b.  Examples include:

                                    1.  Rattlesnake. (Western, Southern, and eastern U.S.)

                                    2.  Water Moccasins. (Southern/Eastern U.S.)

                                    3.  Copperhead. (Eastern U.S.)

                                    4.  Bushmaster.  (Central and South America)

                                    5.  Fer-de-Lance.  (Central and South America)

                                    6.  Habu.  (Okinawa)

            2.  Elapidae:

                 a.  Characteristics:  Fixed fangs, head shape is in proportion to the width of body.

                 b.  Examples include:

                        1.  Coral snakes. (Southwestern U.S.)

                        2.  Kraits. (Africa)

                        3.  Cobras. (Asia, India)

                        4.  Mambas.  (Africa)

                        5.  Asps. (Asia, Africa)

3.  Hydrophiidae:

     - Characteristics:  Fixed fangs, Brightly colored (except the Olive Sea Snake) flat tail, extremely poisonous.

Example:  The Seasnake is the only one for this category. Found in almost all tropical waters world wide.

          4.  Colubridae :

          a.  Characteristics:  Fixed fangs located in the rear part of the mouth, Large eye on a small           

              pointed head.

          b.  Example: The Backfanged Boomslang is the only one for this catagory

 B.  CLASSIFICATION OF SNAKE VENOM

They are broken into two general catergories;

a.  Hemotoxic  (Crotalidae- Pit Vipers)

1.  Actions

a)  Thrombase - Action mainly at the site of the bite, causing severe pain, local thrombosis, gangrene, and  intravascular clotting.

                             b)  Hemorrhagin – The predominant substance in venom, causing destruction       

                             of the capillary cells with resultant leakage.  This starts locally and then

                             becomes generalized.

b.  Neurotoxic: (Elapidae- Cobra, Coral Snake, Boomslang, and Sea Snake are                      primarily neurotoxic with the following substances and actions):

            1. Actions

                 a)  Neurotoxin - Has paralytic effect on the respiratory center and the 9^th

     (prevention of swallowing), 10^th (Gag reflex), 11^th (Tongue movement),   

     and 12th (Prevention of use of accessory muscles) pairs of cranial nerves.

b)  Hemolysin - Found in some varieties, causes lysis of the blood cells.  

     (Blood cells rupture and clot, preventing the carrying of oxygen)

c)  Cardiotoxin - Causes toxic cardiac arrest.

2.  Unfortunately snakes are not just hemotoxic or neurotoxic, they usually contain elements of both.

      C.  DIAGNOSIS OF SNAKEBITE:

1.  Fang Marks:  Fang marks may be present as one or more well defined punctures, or as a series of small lacerations or scratches, or there may not be any noticeable or obvious markings where the bite occurred.  The absence of fang marks does not exclude the possibility of envenomation (especially if a juvenile snake is involved).  However with rattlesnake envenomation, fang marks are invariably present and are generally seen on close examination.  Bleeding may persist from the fang wounds.  The presence of fang marks does not always indicate envenomation; rattlesnakes when striking in defense will frequently elect not to inject venom with the bite, resulting in a “dry bite.”  Manifestations of signs and sypmtoms of envenomation are necessary to confirm diagnosis of a snake venom poisoning.

2.  Signs and Symptoms of Envenomation:

  a.  Crotalidae (Pit Viper):

1.  Symptoms vary depending on the type of snake, and the amount of venom deposited, i.e. younger rattlesnakes tend to dispense all of their venom in relation to a larger, older      rattlesnake dispensing either none or a larger amount.  1/3 of bites are dry and are purely      defensive, 1/3 bites have mild symptoms, and 1/3 bites have severe and rapid onset of      symptoms:

            a)  Excruciating pain at the site of the bite.

            b)  Presence of fang marks.

c)  Tissue swelling at site of bite.  Swelling begins within 3 three minutes and may    

     continue for an hour with enough severity to burst the skin.

            d)  Severe headache and thirst.

            e)  Bleeding from major organs that may show up as hematuria.

            f)  Destruction off blood cells and other tissue cells, bleeding into surrounding tissue.

NOTE:  Death may occur within 24-48 hours if bite is serious or left untreated.  Even with proper treatment there is grave danger of loss of a portion of the extremity.

b.  Elapidae (Coral and Cobras):

c.  Colubridae (Backfanged Boomslang):

1.  Symptoms are not as marked and onset is usually slower than Crotalidae.

  a) Impairment of circulation with irregular heartbeat, drop in B/P, weakness, and exhaustion terminating into circulatory system collapse.

  b)  Severe headache, dizziness, blurred vision, hearing difficulty, confusion and unconsciousness.

      c)  Muscular incoordination and muscle twitching, excessive persiration, confusion and unconsciousness.

      d)  Respiratory difficulty leading to respiratory paralysis.

      e)  Nausea, vomiting, and diarrhea.  Chills and often rapid onset of fever.

d.  Hydrophiidae (Seasnake):

     1.  Intense pain is not obvious at the site of the bite;  30 minutes after the bite there is stiffness, muscle aches and spasm of the jaw followed by moderate to severe pain in the affected limb.  There followsprogressive CNS symptoms of blurred vision, drowsiness and finally respiratory paralysis.

NOTE:  Persistent myths about sea snakes include mistaken idea that they can’t bite very effectively.  The truth is that their short fangs (2.5-4.5mm) are adequete to penetrate skin and they can open their mouth wide enough to bite a person’s thigh.  Seasnakes can swallow fish more than twice the diameter of their neck.  Envenomation from Seasnakes is rare but does occur and without treatment death usually occurs within 12-24 hours.

D.  TREATMENT OF SNAKEBITE

1.      Keep the victim calm and reassured, allow the patient to lie flat and avoid movement.  If possible, allow the limb to rest at a neutral level in relation to the victim’s heart.

2.      Identify the bite site.

3.      If the bite is on the hand, finger, foot or toe, immediately remove any rings, bracelets, watches or any constricting items from the extremity, wrap leg/arm rapidly with 3” to 6” ACE or CREPE bandage past the knee or elbow joint immobilizing it.  Leave the fang marks open.  Wrap no tighter that one would for a sprain.

4.      Apply a proper splint

5.      Make sure pulses are present.

6.      If the tactical situatuation dictates EVACUATE, you will not have a means of definitive treatment (i.e. Anti-venin).  If the tactical situation does not allow for immediate evacuation, then monitor ABC’s and give supportive care as necessary, (maintain airway, control bleeding, treat for shock, monitor site for swelling).

COMMON DON’T’S

1.      DO NOT cut or incise the bite site.

2.      DO NOT apply ice or heat to the bite site.

3.      DO NOT apply oral (mouth) suction.

4.      DO NOT remove dressings/elastic wraps.

5.      DO NOT try to kill the snake for identification as this may lead to other people being bitten.

7.      DO NOT have the victim eat or drink anything.

NOTE: About 8,000 people in the United States receive venomous bites each year; nine to 15 people die.  Some experts say that is because victims cannot identify the snake that bit them.  The rule is: IF BITTEN BY A SNAKE SEEK MEDICAL TREATMENT!  Regardless if the snake was poisonous or not, medical attention should be sought because even “harmless” snakes can cause infection and an allergic reaction.

It is up to the Hospital Corpsman to find out and follow local protocol in the Area of Operation.

E.    PREVENTION OF SNAKE BITES:

1.    LEAVE THE SNAKE ALONE! (This is the best and number one method of prevention) 

    Many people are bitten because they try to kill the snake, catch it or play with it.

    Keep your hands and feet out of areas that you can’t see.  i.e.   holes, under rocks or logs.

III.               INSECT ENVENOMATION:

A.     Bees and Wasps (Hymeroptra):

1.      Most of this group sting their victims

2.      Toxins from this group are similar to the venom of pit viper snakes as far as being able to destroy red blood cells, but their primary effect is from the strong histamine reaction they cause.

3.      Stinging, burning sensation with swelling.  This swelling, when caused by stings around the head and neck, may be severe enough to impair the airway.

4.      The stinger should be removed immediately to prevent more venom from entering the victim.  Remove the stinger by scraping across the skin with a knifeblade or similar object.  Grasping the stinger with tweezers only injects the remaining venom into the victim.

5.      Antihistamines, ice and pain medications are helpful

6.      Apply a paste of baking soda or apply strong household ammonia to reduce discomfort. 

7.      In severe cases give Benadryl 1 mg. SQ first, then 25-50 mg I.V. push over 1 minute.

8.      If the patient is allergic to the venom, treat the anaphylactic reaction.

NOTE:  Bees only sting once and leave the stingers and venom sac embedded in the skin. Wasps can sting multiple times.                             

            B.     Centipedes, millipedes, and caterpillars.

1.      Centipedes are venomous with hollow fangs like poisonous snakes.  If bitten, the patient will have immediate severe pain followed by redness and swelling.  Sometimes necrosis with ulcer formation may occur.

2.      Millipedes secrete a toxin by glands in the body.  When the fluid touches the skin,

it produces itching and burning.

3.      Many caterpillars have hollow venom containing hairs on their bodies.  If these    

      hairs contact with the skin, they cause severe burning, pain redness, swelling, and

      necrosis of the tissue.  Scotch tape on the sting is effective in removing the broken

      off hairs from the skin.

4.  Treatment

1.  Very similar to that of a bee sting.  Antihistamines, ice, and pain mediations are helpful.  Treat anaphylactic reactions.

  C.     PREVENTION OF BEE STINGS/CENTIPEDE/MILLIPEDE ENVENOMATION

a.       LEAVE THEM ALONE! (This is the best method known to man!)

b.      Avoid nesting sites of bees and wasps

c.       Shake out all sleeping bags/clothing and check boots before putting on

D.     SPIDER BITES AND SCORPION STINGS                               

1.  Black Widow Spider.

a.  Only the female bites and has a neurotoxic venom.  Description – Glossy Black with a red

      hourglass on the underside of the abdomen.

b.  Venom is a neurotoxin

c.  Symptoms are:

1.  Initial pain is not severe, but severe local pain rapidly developes.

2.  The pain is gradually spreads over the entire body and settles in the abdomen and legs.

           3.  Weakness.

           4.  Tremors.

           5.  Sweating.

           6.  Salivation.

           7.  Nausea.

           8.  Vomiting

9.  Respiratory muscle weakness combined with pain may lead to respiratory arrest

         10.  Rash may occur.

         11.  Anaphylactic reactions can occur, but are rare.

         12.  Symptoms usually regress after several hours and are usually gone in a few days.

d.  Treatment

1.  Clean this site with soap and water

2.  Intermitten ice for 30 minutes each hour

3.  For severe cases, I.V. narcotics such as Valium.

4.  Supportive care as necessary i.e. ABC’s

5.  Antibiotics if infection occurs.

2.  Brown house Spider (recluse)

a.  Identified by dark brown violin on the back of a small light brown spider.

b.  Venom is a cytotoxin(destroys human cells)

Symptoms include:

1.  There is no pain or so little that the patient is not aware that he has been bitten.

2.  A few hours later, a painful red area with mottled cyanotic center appears. 

3.  A macular rash sometimes occurs.  Necrosis does not occur in all bites, but usually after 2-3 days there is an area of discoloration that does not blanch with finger pressure. 

4.  The area turns dark and mummified in a week or two.  The margins separate and the eschar falls off leaving an open ulcer.

5.  Secondary infection and regional lymphadenopathy usually become evident at this time. 

6.  The outstanding feature of brown recluse bites is the ulcer does not heal, but persists for weeks or months.

7.  In many cases there is systemic reaction, in addition to the ulcer, that is serious and may lead to death. 

8.  The systemic reactions occur chiefly in children and are marked by fever, chills joint pain, splenomegaly(swelling of the spleen), vomiting, and a generalized rash.  These systemic reactions can occur at any time as long as the ulcer is present.

    c.  Treatment includes:

1.  There is no antivenom for brown recluse bites.

2.  It is necesssary to excise all the indurated skin and facia before healing will start.  If the ulcer is not excised it will continue to grow until it is several  inches in diameter.

3.  Supportive care as necessary

NOTE:  Tetanus prophylaxis and antibiotics are necessary to control secondary infection.  Cortisone will arrest the systemic reaction but will not affect the ulcer.  Anaphylactic reactions may occur and must be managed.

3.  SCORPIONS

a.  General Description:

Scorpions are primitive arachnids.  They were among the first insect land dweller.  Their fossil remains have been found aged 400 million years.  These arthropods inhabit temperate climates around the world and number greater than 650 species.  Fifty species can cause serious disease in humans.

The most dangerous scorpions in the U.S. inhabit Arizona and portions of California, Texas, and New Mexico.

Although the size and shape of these arachnids can be both intimidating and frightening, envenomation, although potentially painful, very rarely produces mortality in humans.

b.  Symptoms: Symptoms are graded by the following scale:

I.                    Local pain and or parasthesis at site of sting

II.                 Pain or parasthesis remote from the site of sting in addition to local findings

III.               EITHER cranial nerve or somatic skeletal neuromuscular dysfunction:

1.      Cranial nerve dysfunction: Bluured vision, wandering eye movements, hypersalivation, trouble swallowing, tongue twitching/spasms, prbloems with upper airway, slurred speech.

2.      Somatic muscloskeletal neuromuscular dysfunction:  Jerking of extremity(ies), restlesness, severe involuntary shaking and jerking that may be mistaken for a siezure.

IV.              Both cranial nerve and somatic skeletal neromuscular dysfunction

c.  Diagnosis:

     1.  Pain

     2.  Parasthesis at site of sting

     3.  Erythema

     4.  Edema

     5.  Postitive “Tap Test”

d.   Treatment:

Grade I and II: Supportive care, ice applied to the site for 30 minutes each hour until symptoms subside, oral analgesics are also helpful.

NOTE:  Beware that Grade I and II can rapidly through Grades III and IV, which may require aggressive airway management.