Parte I. Tesis Doctoral
4. RESULTADOS
4.3 Experimento 3
environment, treat reptile and arthropod envenomation, in accordance with the
references. (FMST.07.38)
ENABLING LEARNING OBJECTIVES:
1) Without the aid of references, select from a given list the first aid measures used for pit viper envenomation, in accordance with the references. (FMST.07.38a)
2) Without the aid of references, select from a given list the first aid measures used for coral snake envenomation, in accordance with the references. (FMST.07.38b) 3) Without the aid of references, select from a given list the first aid measures used for
widow spiders (lactordectus species) bites, in accordance with the references.
(FMST.07.38c)
4) Without the aid of references, select from a given list the first aid measures used for brown recluse spider (loxosceles species) bites, in accordance with the references.
(FMST.07.38d)
5) Without the aid of references, select from a given list choose the first aid measures used for bee, wasp, and hornet stings, in accordance with the references. (FMST.07.38e)
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OUTLINE.
1. PIT VIPERS. Crotalidae have a triangular head, cat-like vertical pupils, hinged fangs and a heat-sensitive "pit" on each side of the head between the tip of the nose and the eye.
Rattlesnakes have a variable number of rattles depending upon age and number of molts. They sometimes strike without rattling. About 60% of this country's venomous bites are attributed to rattlesnakes. Cottonmouths (water moccasins) and copperheads are the other two commonly encountered North American pit vipers. Copperhead and cottonmouth venom are quite similar but weaker than most rattlesnake venom.
a. Anatomy of Pit Vipers.
(1) Venom apparatus: Venom gland; Compressor glandular muscle; Primary duct;
Accessory gland; Secondary duct; Fang sheath; and fangs.
(2) Facial pit organs: Highly sensitive paired receptors of infrared radiation that can detect temperature changes of less than 0.2C; used to detect warm-blooded prey/predators and aim strike; also pit organs may have a role in determining volume of venom injected.
(3) Rattles or buttons: Interlocking keratin rings at tip of tail in rattlesnakes; a new rattle is added with each molting cycle (every 50-400 days); some are lost due to trauma.
(4) The strike: Aimed primarily by facial pits; rarely strike farther than 1/2 their body length; speed - approximately 8 feet/second.
(a) Rattlesnakes generally inject 25-75% of their venom when they bite humans.
(b) Can bite without injecting any venom ("dry bite").
1. 20% - no envenomation.
2. 20-30% - mild envenomation.
3. 30-50% - moderate to severe envenomation.
b. Signs and Symptoms of Snake Venom Poisoning:
(1) Pit Vipers:
(a) Local:
1. Puncture wounds/scratches:
A. Pattern can be misleading (venomous vs. nonvenomous).
B. Must differentiate from other animal/insect bites or plant puncture wounds- usually venomous snakebite wounds are larger, with more bleeding.
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C. May be one or many fang marks present; range from a few mm to 4cm apart.
2. Pain, edema, erythema:
A. Usually presents within 30 minutes if envenomation.
B. More severe envenomation generally yields more rapid progression and more severe pain.
C. Pain is usually characterized as burning and immediate in onset.
D. Pain usually confined to bite site.
E. Edema limited to subcutaneous tissues (with no increase in intra-compartmental pressures).
F. Usually starts within 5 minutes (if none in 10 minutes, probably no significant envenomation unless dealing with Mojave rattlesnake).
G. Gradually spreads up extremity for 36 hours.
H. Danger of airway obstruction in bites to head and/or neck.
3. Ecchymosis:
A. Ecchymosis starts within several hours.
B. May involve entire extremity.
4. Lymphangitis:
A. Venom absorbed rapidly through lymphatic system results in lymphatic inflammation.
5. Petechiae, vesicles, hemorrhagic bullae:
A. Will occur in untreated rattlesnake envenomation.
B. Rarely seen when treated early with adequate antivenin.
C. Usually occurs 6-36 hr after bite.
6. Necrosis, tissue destruction:
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A. Due to direct venom effects.
B, Can be prevented if adequate antivenin is given within 2 hours of bite.
(b) Systemic:
1. Nausea, vomiting:
A. Common (early onset may indicate severe envenomation).
2. Weakness, diaphoresis, chills, dizziness/vertigo.
A. Syncope is common with all pit viper bites.
B. Frequency is proportional to severity of bite.
3. Change in taste:
A. May complain within minutes of rubbery or metallic taste.
4. Increased salivation.
5. Fever.
6. Tingling, numbness in scalp/face/fingers/toes:
A. Can occur within 10 minutes and indicates moderate to severe envenomation.
7. Fasciculations in face/neck/back/ or other involved extremity:
A. Can occur early and indicates severe envenomation.
8. Visual disturbances:
A. Blurred vision, yellowing of vision and blindness.
9. Tachycardia, bradycardia.
10. Hemorrhage, hemolysis, thrombosis and DIC:
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A. Bleeding from wounds, gingival bleeding, epistaxis, Hematuria, hematemesis, Melena, lower GI bleeding, hemoptysis, peritoneal hemorrhage and cerebral hemorrhage.
B. Can occur as early as 6 hours; more common 12-72 hours after bite.
C. Systemic bleeding only occurs in moderate to severe envenomation.
D. Most coagulopathic effects secondary to proteases acting at various sites in the coagulation cascade.
11. Hypotension, shock:
A. Can occur rapidly in severe envenomation.
B. Early, due to pooling of blood.
C. Late may be due to loss of volume.
D. Generally little effect from decreased cardiac contractility.
12. Pulmonary edema:
A. Common in severe envenomation.
B. Secondary to toxin and inflammatory injury of pulmonary capillary membranes and pooling of blood in major vessels and capillary beds of the lung.
C. Compounded by direct cardiodepressant factor in some venoms.
13. Oliguria, anuria:
A. Hypotension with resultant decreased GFR. (#1).
B. Hemoglobinuria and myoglobinuria with renal tubular obstruction.
C. Direct toxic effect of venom on kidneys.
D. Acute tubular necrosis from rhabdomyolysis.
14. Paresis, Paralysis:
A. Seen with Eastern Diamondback and Mojave rattlesnakes.
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B. Uncommon with other rattlesnakes.
15. Respiratory failure:
A. Uncommon with pit viper bites (except Mojave).
B. Complicated by cardiovascular failure.
16. Seizures:
A. Probably due to hypertension and hypoxia.
17. Coma:
A. Usually sensorium is clear.
B. When coma occurs, it is secondary to cerebral anoxia.
18. Death:
A. Generally occurs in 6 to 48 hours in untreated severe envenomation.
B. Can occur sooner with IV envenomation.
c. First Aid Measures for Pit Viper Envenomation.
(FMST.07.38a)
(1) Do not try to kill the snake and bring it in for identification.
(a) Only vital to identify the snake when Mojave rattlesnake or coral snake bites are a possibility, as management is altered.
(b) Risk of a second bite to the victim or rescuer.
(c) Should never delay transportation of the victim.
(2) Remove any jewelry, which could become a tourniquet with progression of edema.
(3) Calm and reassure patient to decrease heart rate and circulation of venom.
(4) Constriction band.
(a) Most widely accepted first aid measure in the literature.
(b) Should be more than 1/2 inch wide.
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(c) Apply to proximal end of extremity affected and wrap to approximately 5 cm above swelling (site of envenomation). Then wrap back towards proximal end of extremity from where the wrap started.
(d) Apply only tight enough to occlude lymphatic and superficial venous return.
(e) Probably no benefit when applied 30 min or more after bite.
(f) Maintain until antivenin is started.
(5) Incision and suction.
(a) Very controversial; should only be used by experienced medical personnel.
(b) Do not incise wound.
(c) Suction best applied by mechanical means (Sawyer extractor).
(d) Do not use mouth (unknown oral lesions may expose rescuer to risk).
(e) Should be started within 30 minutes of envenomation.
(f) Continue suction for 30 to 60 min.
(6) Rest and immobilization.
(a) Put victim at rest and splint extremity in position of function, at or just below heart level.
(b) Allow room for swelling in splint.
(7) Ice.
(a) Avoid any method of cooling.
(8) Watch for adverse reactions.
(a) Rare documented cases of anaphylaxis caused by snake venom in patients previously bitten or otherwise exposed to snake venom.
(b) Some evidence that venom can activate the alternate-complement system directly and cause a similar reaction.
(9) Rapid transport to a medical facility.
(a) The most important measure in first aid.
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(b) No measures should delay this; antivenin is the only proven definitive therapy.
2. CORAL SNAKES. The elapidae species of coral snakes are brightly colored, with black noses and alternating red-yellow-red-black bands around their bodies (remember "red on yellow, kill a fellow"). They have relatively small mouths with fixed fangs. From southern Mexico through tropical South America, the rules for distinguishing coral snakes are highly unreliable. Unless you are a knowledgeable herpetologist, it is best not to pick up colorful snakes in the tropics.
a. Signs and Symptoms of Coral Snake Envenomation:
(1) Fang marks may be hard to see.
(2) Frequent delay in onset of symptoms, followed by extremely rapid progression.
(3) Little or no pain at bite site.
(4) No local necrosis.
(5) Earliest evidence may be drowsiness or euphoria.
(6) N/V, increased salivation, paraesthesias at bite site.
(7) Bulbar paralysis progressing to peripheral paralysis.
(8) Paraesthesias, and fasciculation.
(9) Occasional seizures.
(10) Mild Hypotension.
(11) Death is due to respiratory and cardiovascular failure.
b. First Aid Measures For Coral Snake Envenomation. (FMST.07.38b)
(1) None of proven benefit except rest, reassurance and rapid transportation to medical facility for antivenom administration.
3. GILA MONSTERS. No direct injection mechanism for their venom, but have powerful jaws that allow them to chew and tear at their victims. Drooling venom produces a substantial
amount of pain and possible complications resembling pit viper envenomation. Follow the recommendations for pit viper envenomation. Fatal Gila monster encounters are extremely rare.
4. VENOMOUS ARTHROPODS. Arthropods represent the largest phylum in the animal kingdom. It contains spiders, scorpions, insects, ticks, kissing bugs, water
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bugs, caterpillars, moths, butterflies, grasshoppers, centipedes, and millipedes, among others. Some arthropods sting (bees, ants, scorpions, etc.), others bite (spiders, centipedes, kissing bugs, etc.), while still others discharge a secretion that is toxic (millipedes, caterpillars, etc.). Although the number of arthropods that are sufficiently venomous to endanger humans is not known, these animals are
implicated in far more bites and stings than all other phyla combined. Almost all of the 20,000 species of spiders are venomous, but luckily for, man, only relatively small numbers have fangs long and strong enough to penetrate the human skin.
There are some 500 species of scorpions and all are venomous, although only a small number pose a significant danger to humans.
a. The number of deaths from arthropod stings and bites is not known, nor do most countries keep records of the incidence of such injuries. In Mexico, parts of Central and South America, and in North Africa, deaths from scorpion stings may exceed several thousand per year. Spider bites probably account for no more than 200 deaths per year, worldwide. The number of deaths from arthropod bites or stings in the temperate countries is far greater than the
number of deaths from snakebite. Almost all of these deaths, however, are from anaphylactic reactions.
5. SPIDERS. -There are at least 200 species of spiders that have been implicated in significant bites to humans (Russell, 1988a). Spiders got the misplaced blame for the bites seen in one large series of case studies. Of some 600 suspected spider bites, 80% were found to be caused by other arthropods. The arthropods most frequently involved in these mis-diagnoses were ticks (including their embedded mouth parts), kissing bugs, mites, bedbugs, fleas, flies, beetles, water bugs and various other stinging arthropods.
a. Lactordectus species (Widow spiders): It is most commonly referred to as the Black Widow, Brown Widow or Frog-legged spider depending on the species. There are many other
commons names such as: hourglass, poison lady, deadly spider, red-bottom spider, T-spider, Gray Lady spider, or shoe-button spider. Although both male and female widow spiders are venomous, only the latter have fangs large and strong enough to penetrate the human skin.
Mature females range in body length from 10 to 18mm, whereas males are from 3 to 5mm.
(1) Signs and Symptoms of spider envenomation.
(a) Sharp, pinprick-like bite, but in some cases the incident is so minor that it goes unnoticed.
(b) Initial bite-pain is often followed by dull-numbing pain in the affected extremity, and cramps in one of the large muscle masses.
(c) Muscle fasciculations can be seen within 30 minutes of the bite.
(d) Sweating is common.
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(e) Complaints of weakness and pain in the regional lymph nodes.
(f) Pain in the lower back, thighs, or abdomen is common and rigidity of the abdominal muscles is seen in severe envenomations.
(g) Severe paroxysmal muscle cramps may occur accompanied by arthralgias.
(h) Tissue reaction around the bite may vary, depending on the species involved. In most cases in the United States, there is no reaction at the bite site and the puncture wounds may be impossible to find. There may be an immediate 2 to 4 mm blanched area around the puncture wounds, surrounded by a slightly erythematous area, which in time becomes pallid. This may persist for 20 to 30 minutes.
(i) Hypertension is a characteristic finding in moderate to severe poisonings. It usually appears 2 to 3 hours post envenomation.
(j) Elevation of body temperature.
(k) Increased salivation.
(1) Anorexia.
(2) Treatment for Widow Spider envenomation.
(FMST.07.38c)
(a) First aid measures are supportive in nature. If the pain is intense, ice can be placed over the wound until the patient arrives at a medical facility.
(b) Antivenin is given in severe cases at medical facilities.
b. Loxosceles species (Violin spiders): Are known in the United States as fiddle-back, or brown recluse spiders. There are over 100 species of Loxosceles. The abdomen of these spiders varies in color from gray to orange or reddish-brown to dark brown. The violin on the cephalothorax is brown to blackish and distinct from the pale yellow to reddish-brown background of the cephalothorax. This spider has three pairs of eyes, forming a curved row.
Females average 8 to 15 mm in body length whereas males average 6 to 10 mm. Both are venomous.
(1) Signs and Symptoms of Violin spider envenomation.
(a) Pain; about the same degree of a bee sting but patients may be completely unaware of the bite.
(b) Localized burning sensation around the site of injury.
(c) Pruritus is often present and the area begins to appear red, with a small-blanched area around the immediate bite site.
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-(d) The reddened area enlarges during the subsequent 1- 8 hours. It often becomes irregular in shape and, as time passes, hemorrhages may develop throughout the area.
(e) A small bleb or vesicle forms at the bite site and increases in size.
(f) Vesicle subsequently ruptures and a pustule forms.
(g) The whole area becomes swollen and painful.
(h) Lymphadenopathy may develop.
(i) Necrosis can develop from superficial to deep layers.
(j) Rare systemic signs and symptoms include:
1. Malaise.
2. Stomach cramps.
3. Nausea and vomiting.
4. Jaundice.
5. Spleen enlargement.
6. Hemolysis.
7. Hematuria.
8. Thrombocytopenia.
(2) Treatment for Loxosceles spider envenomation: (FMST.07.38d)
(a) There are no first-aid measures of value. In fact, all first-aid measures should be avoided, because the natural appearance of the lesion is most important in determining the
diagnosis.
(b) An ice pack may be placed over the wound if the pain is severe.
(c) Excision of the bite site is no longer recommended as this has been demonstrated to cause worsening of necrosis and tissue damage. Definitive therapy includes use of dapsone, antibiotics, tetanus prophylaxis and possible steroid use.
c. There are many other species of spiders that include Steatoda species (cobweb spiders), Phidippus species (jumping spiders), Chiracanthium species (running spiders), Lycosa
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-species (wolf spiders), and the newest member to the United States is the Hobo spider. There have been several reported deaths in the Northwestern United States. Originally a European species of brown spider, the Hobo spider was introduced into the U.S. in 1936, and little research has been done on it to date.
6. SCORPIONS. Approximately 75 of the 650 species of scorpions can be considered of sufficient importance to warrant medical attention. In the United States, members of the genera Hadrurus and Vejovis are capable of inflicting a painful and erythematous, but non-lethal lesion. However, species of the genus Centruroides are sufficiently dangerous to warrant definitive medical care. Most stings are inflicted by the Vejovis species.
a. Centruroides species. There are approximately 30 species of this genus confined to the New World. Of these, eight are of considerable medical importance, and most of these species are found in Mexico. In the United States, they are commonly referred to as "bark
scorpions", because of the preference for hiding under the loose bark of trees, in dead trees, or in logs. Their general color is straw to yellowish-brown or reddish-brown, and they are often easily distinguishable from other scorpions in the same habitat by their long thin tail with its "telson" on the end, the pedipalps, or pincer-like claws. They can reach lengths up to 55 mm.
(1) Signs and symptoms of envenomation.
(a) Initial pain, rarely severe.
(b) Area becomes sensitive to touch (tap test).
(c) Tachycardia may ensue after one hour.
(d) Respiratory rate increases.
(e) Fasciculations may be seen over the face or large muscle masses.
(f) Complaints of generalized muscle weakness.
(g) Respiratory distress may progress to paralysis.
(h) Slurring of speech may be present.
(i) Convulsions have been reported.
(2) Treatment for scorpion envenomation.
(a) There is no first-aid measure of value for scorpion stings.
(b) Ice may be placed over the wound to reduce pain.
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-(c) In severe cases, antivenin may be recommended.
b. Vejovis species is closely related to the Urectonus. Both genera are ground scorpions.
Whereas Urectonus usually inhabits mountain habitats from southern California to Oregon, Bejovis has a wide distribution from the southern portions of Canada, south through Wyoming and Colorado to Texas and west to California. Some species measure up to 85mm, but most are from 30 to 35mm. Vejovis spinigerus, a common western U.S.
species, is often called the striped-tail scorpion.
c. Hadrurus species is native to North America. These are the longest and most stout-bodied of our scorpions, generally referred to as the giant hairy scorpions because of their size and the conspicuous bristles on their legs, pedipalps and caudal segments. Adults may can measure up to 135 mm. These are burrowing species and may be found as deep as 2 feet in sandy soil. They are native to Arizona, California and parts of Utah, Nevada and Idaho, as well as Mexico.
7. BEES, WASPS, HORNETS AND ANTS. While it may take over 100 bees to inflict a lethal dose of venom in most adults, one sting can cause a fatal anaphylactic reaction in a hypersensitive person. There are 3 to 4 times more deaths in the United States from bees than from snakebites. In the few fatalities that have resulted from multiple bee stings, death has been attributed to acute cardiovascular collapse.
a. Treatment for bee stings: (FMST.07.38e)
(1) The stingers of many bees may remain in the skin and should be removed by teasing or scraping rather than pulling, to avoid even more venom being injected into the patient.
(2) Ice may be applied to the sting site.
(3) Persons with known hypersensitivity to stings should carry a Bee-Sting Kit, containing an antihistamine and epinephrine when in endemic areas.
(4) Desensitization can be carried out using whole-body antigens or, preferably, whole-venom antigens.
8. TICKS AND MITES. Carry many diseases. In North America, some species of Dermacentor and Amblyomma cause tick paralysis.
a. Signs and symptoms of Tick Paralysis.
(1) Restlessness and irritability.
(2) Lethargy and anorexia.
(3) Generalized muscle weakness.
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-(4) Incoordination and ataxia.
(5) Nystagmus.
(6) Ascending flaccid paralysis with loss of deep tendon reflexes.
(7) Bulbar or respiratory paralysis may develop.
b. Treatment for Tick Paralysis:
(1) Remove the tick.
(2) Treat symptomatically (ventilator support may be necessary).
(3) Lesions should be cleaned.
(4) Antivenin and/or corticosteroids are used in severe cases.
9. LEPIDOPTERA (CATERPILLARS). Caterpillars commonly cause envenomation in humans. There are at least ten families of caterpillars that are venomous.
a. MEGALOPYGE OPERCULARIS (Puss Caterpillar or Woolly Slug) The most commonly seen venomous caterpillar in the United States.
(1) Description: Hairy, flat, ovoid shaped: 30-35 millimeters in length.
(2) Location: Texas north to Maryland and Missouri.
(3) Stinging apparatus: Consists of spines intermingled with the hairs of the body:
b. SIGNS AND SYMPTOMS.
(1) Needling pain (Can be intense).
(2) Redness.
(3) Swelling.
(4) Nausea.
(5) Headache.
(6) Fever.
(7) Vomiting.
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-(8) Lymphadenopathy.
(9) Hypotension.
(10) Shock.
(11) Bleeding of the mucus membranes.
a. Treatment
(1) Apply contact tape to affected area, and remove tape. This will effectively remove spines from affected area.
(2) Group I corticosteroid cream and ointment.
(3) Codeine or Demerol may be required for pain.
(4) Antiemitics may be needed to control vomiting.
(4) Antiemitics may be needed to control vomiting.