Scorpion sting information part I-V

Background
Scorpion stings are a major public health problem in many underdeveloped tropical countries. For every person killed by a venomous snake, 10 are killed by a venomous scorpion. In Mexico, 1000 deaths from scorpion stings occur per year. In the United States, only 4 deaths in 11 years have occurred as a result of scorpion stings. Furthermore, scorpions can be found outside their normal range of distribution, ie, when they accidentally crawl into luggage, boxes, containers, or shoes and are unwittingly transported home via human travelers.

A scorpion has a flattened elongated body and can easily hide in cracks. It has 4 pairs of legs, a pair of claws, and a segmented tail that has a venomous spike at the end. Scorpions vary in size from 1-20 cm in length.

Out of 1500 scorpion species, 50 are dangerous to humans. Scorpion stings cause a wide range of conditions, from severe local skin reactions to neurologic, respiratory, and cardiovascular collapse.

Almost all of these lethal scorpions, except the Hemiscorpius species, belong to the scorpion family called the Buthidae. The Buthidae family is characterized by a triangular-shaped sternum, as opposed to the pentagonal-shaped sternum found in the other 5 scorpion families. In addition to the triangular-shaped sternum, venomous scorpions also tend to have weak-looking pincers, thin bodies, and thick tails, as opposed to the strong heavy pincers, thick bodies, and thin tails seen in nonlethal scorpions. The lethal members of the Buthidae family include the genera of Buthus, Parabuthus, Mesobuthus, Tityus, Leiurus, Androctonus, and Centruroides. These lethal scorpions are found generally in the given distribution:


Buthus - Mediterranean area
Parabuthus - Western and Southern Africa
Mesobuthus - Asia
Tityus - Central and South America, Caribbean
Leiurus - Northern Africa and Middle East
Androctonus - Northern Africa to Southeast Asia
Centruroides - Southwest USA, Mexico, Central America

However, these scorpions may be found outside their habitat range of distribution when inadvertently transported with luggage and cargo.

In general, scorpions are not aggressive. They do not hunt for prey; they wait for it. Scorpions are nocturnal creatures; they hunt during the night and hide in crevices and burrows during the day to avoid the light. Thus, accidental human stinging occurs when scorpions are touched while in their hiding places, with most of the stings occurring on the hands and feet.

Pathophysiology
Scorpions use their pincers to grasp their prey; then, they arch their tail over their body to drive their stinger into the prey to inject their venom, sometimes more than once. The scorpion can voluntarily regulate how much venom to inject with each sting. The striated muscles in the stinger allow regulation of the amount of venom ejected, which is usually 0.1-0.6 mg. If the entire supply of venom is used, several days must elapse before the supply is replenished. Furthermore, scorpions with large venom sacs, such as the Parabuthus species, can even squirt their venom.

The venom glands are located on the tail lateral to the tip of the stinger and are composed of 2 types of tall columnar cells. One type produces the toxins, while the other produces mucus. The potency of the venom varies with the species, with some producing only a mild flu and others producing death within an hour. Generally, the venom is distributed rapidly into the tissue if it is deposited into a venous structure. Venom deposited via the intravenous route can cause symptoms only 4-7 minutes after the injection, with a peak tissue concentration in 30 minutes and an overall toxin elimination half-life of 4.2-13.4 hours through the urine. The more rapidly the venom enters the bloodstream, the higher the venom concentration in the blood and the more rapid the onset of systemic symptoms.

Scorpion venom is a water-soluble, antigenic, heterogenous mixture, as demonstrated on electrophoresis studies. This heterogeneity accounts for the variable patient reactions to the scorpion sting. However, the closer the phylogenetic relationship between the scorpions, the more similar the immunological properties. Furthermore, the various constituents of the venom may act directly or indirectly and individually or synergistically to manifest their effects. In addition, differences in the amino acid sequence of each toxin account for their differences in the function and immunology. Thus, any modifications of the amino acid sequence result in modification of the function and immunology of the toxin.

The venom is composed of varying concentrations of neurotoxin, cardiotoxin, nephrotoxin, hemolytic toxin, phosphodiesterases, phospholipases, hyaluronidases, glycosaminoglycans, histamine, serotonin, tryptophan, and cytokine releasers. The most potent toxin is the neurotoxin, of which 2 classes exist. Both of these classes are heat-stable, have low molecular weight, and are responsible for causing cell impairment in nerves, muscles, and the heart by altering ion channel permeability.

The long-chain polypeptide neurotoxin causes stabilization of voltage-dependent sodium channels in the open position, leading to continuous, prolonged, repetitive firing of the somatic, sympathetic, and parasympathetic neurons. This repetitive firing results in autonomic and neuromuscular overexcitation symptoms, and it prevents normal nerve impulse transmissions. Furthermore, it results in release of excessive neurotransmitters such as epinephrine, norepinephrine, acetylcholine, glutamate, and aspartate. Meanwhile, the short polypeptide neurotoxin blocks the potassium channels.

The binding of these neurotoxins to the host is reversible, but different neurotoxins have different affinities. The stability of the neurotoxin is due to the 4 disulfide bridges that fold the neurotoxin into a very compact 3-dimensional structure, thus making it resistant to pH and temperature changes. However, reagents that can break the disulfide bridges can inactivate this toxin by causing it to unfold. Also, the antigenicity of this toxin is dependent on the length and number of exposed regions that are sticking out of the 3-dimensional structure.

Frequency
United States
A total of 13,000 stings have been reported, with the majority being from the nonlethal scorpions. Only 1 of 30 scorpion species found in the United States is dangerous to humans. This lethal scorpion species is the straw-colored Centruroides. Less than 1% of stings from Centruroides are lethal to adults; however, 25% of children younger than 5 years who are stung die if not treated. The epidemiological features of a patient who has been envenomed show a disposition for rural areas (73%), with most of the stings occurring in the summer months between 6:00 pm and 12:00 am (49%) and a second peak from 6:00 am to 12:00 pm (30%). Both of these peaks coincide maximum human activity with maximum scorpion activity. Furthermore, the larger the scorpion population, the larger the incidence rate. Because the offending scorpion is recovered for identification in only 30% of the cases, local knowledge of the type of scorpion populating the area is useful.

International
Scorpion stings occur in temperate and tropical regions, especially between the latitudes of 50°N and 50°S of the equator. Furthermore, stings predominantly occur during the summer and evening times. In addition, the majority of patients are stung outside their home.

A recent 5-year surveillance study in Saudi Arabia found 6465 scorpion sting cases with a mean patient age of 23 years, a male-to-female ratio of 1.9, and a higher incidence of stings in the months of May-October.1

Mortality/Morbidity
The underreporting of scorpion stings is frequent because most envenomations occur in desert and jungle areas that do not have large medical facilities. Furthermore, reporting is not required.

Most deaths occur during the first 24 hours after the sting and are secondary to respiratory or cardiovascular failure.

Children and elderly persons are at the greatest risk for morbidity and mortality. A smaller child, a lower body weight, and a larger ratio of venom to body weight lead to a more severe reaction. A mortality rate of 20% is reported in untreated babies, 10% in untreated school-aged children, and 1% in untreated adults.

Furthermore, patients in rural areas tend to fare worse than patients in urban areas because of the delay in getting medical help due to a longer travel time to medical centers. Fortunately, better public education, improved control of the scorpion population, increased supportive therapies, and more technologically advanced intensive care units have combined to produce a substantial decrease in mortality from these envenomations.


Race
No racial predilection exists. Any differences in individual reactions to the scorpion sting are a reflection of that individual's genetic composition rather than race.

Sex
Females are more susceptible than males to the same amount of scorpion venom because of their lower body weight.

Age
While adults are stung more often than children, children are more likely to develop a more rapid progression and increased severity of symptoms because of their lower body weight. Furthermore, elderly persons are more susceptible to stings because of their decreased physiologic reserves and increased debilitation.

History
For patients presenting with scorpion stings, ascertaining the following is essential:

Time of envenomation
Nature of the incident
Description of the scorpion
Local and systemic symptoms
The toxicity, variation, and duration of the symptoms depends on the following factors:

Scorpion species
Scorpion age, size, and nutritional status
Healthiness of the scorpion's stinging apparatus (telson)
Number of stings and quantity of venom injected
Depth of the sting penetration
Composition of the venom
Site of envenomation: Closer proximity of the sting to the head and torso results in quicker venom absorption into the central circulation and a quicker onset of symptoms.
Age of the victim
Health of the victim
Weight of the victim relative to amount of venom
Presence of comorbidities
Treatment effectiveness
Generally, intrathecal and intravenous routes have immediate effects, while subcutaneous and intramuscular routes take effect several minutes to hours later.
Nonlethal scorpion species tend to produce local reactions similar to a hymenopteran sting, while lethal scorpion species tend to produce systemic symptoms. The duration to progress to systemic symptoms ranges from 5 minutes to 4 hours after the sting. The symptoms generally persist for 10-48 hours.

Physical
The signs of the envenomation are determined by the scorpion species, venom composition, and the victim's physiological reaction to the venom. The signs occur within a few minutes after the sting and usually progress to a maximum severity within 5 hours. The signs last for 24-72 hours and do not have an apparent sequence. Thus, predicting the evolution of signs over time is difficult. Furthermore, a false recovery followed by a total relapse is common.

A person who has been stung by a scorpion usually has 4 signs, with the most common being mydriasis, nystagmus, hypersalivation, dysphagia, and restlessness. The mode of death is usually via respiratory failure secondary to anaphylaxis, bronchoconstriction, bronchorrhea, pharyngeal secretions, and/or diaphragmatic paralysis, even though venom-induced multiorgan failure plays a large role.

Children present with the same symptoms and signs as adults, except their symptoms are more severe and protracted. Furthermore, they may display a restlessness that is out of proportion when compared to any other disease. A child's symptoms have been described as inconsolable crying; uncontrollable jerking of the extremities; and chaotic thrashing, flailing, and writhing combined with contorted facial grimaces. The symptoms mimic a centrally mediated seizure, but the patient is awake and alert the entire time.

The grading of these scorpion envenomations depends on whether or not neurological signs predominate and is as follows:


Nonneurological predominance

Mild - Local signs
Moderate - Ascending local signs or mild systemic signs
Severe - Life-threatening systemic signs
Neurologic predominance

Grade I - Local pain or paresthesia at the sting site (83%)
Grade II - Pain or paresthesia that has traveled from the sting site (9.1%)
Grade III - Either cranial nerve or somatic neuromuscular dysfunction (4.7%)
Grade IV - Both cranial nerve and somatic neuromuscular dysfunction (3%)
Local signs

Neurotoxic local effects

Local evidence of a sting may be minimal or absent in as many as 50% of cases of neurotoxic scorpion stings. In fact, tissue necrosis is rarely found.
A sharp burning pain sensation at the sting site, followed by pruritus, erythema, local tissue swelling, and ascending hyperesthesia, may be reported. This paresthesia feels like an electric current, persists for several weeks, and is the last symptom to resolve before the victim recovers.
The tap test is administered by tapping at the sting site. A positive result is when the paresthesia worsens with the tapping because the site is hypersensitive to touch and temperature. In fact, wearing clothing over the area and sudden changes in temperature exacerbate the symptoms.
Cytotoxic local effects

A macule or papule appears initially at the sting site, occurring within the first hour of the sting.
The diameter of the lesion is dependent on the quantity of venom injected.
The lesion progresses to a purpuric plague that will necrose and ulcerate.
Lymphangitis results from the transfer of the venom through the lymphatic vessels.
Nonlethal local effects

Pain, erythema, induration, and wheal may be present.
These are secondary to venom activation of kinins and slow-releasing substances.
Neurologic signs: Most of the symptoms are due to either the release of catecholamines from the adrenal glands (sympathetic nerves) or the release of acetylcholine from postganglionic parasympathetic neurons. One study by Freire-Maia et al (1974) found that the adrenergic signs occur at a low venom dose, while cholinergic signs occur at high venom dose concentrations (ie, >40 mcg/100 g in Tityus serrulatus scorpion venom).2 Furthermore, the adrenergic phase tended to be more dependent on the venom dose than the cholinergic phase. However, dual manifestations of the adrenergic and cholinergic signs are possible because of varying organ system sensitivities to these neurotransmitters.

Central nervous system signs

Thalamus-induced systemic paresthesia occurs in all 4 limbs.
Patients experience venom-induced cerebral thrombosis strokes.
The level of consciousness is altered, especially with restlessness, confusion, or delirium.
Patients have abnormal behavior.
Ataxia is also a sign.
Autonomic nervous system signs - Predominately sympathetic signs, parasympathetic signs, or a combination of signs

Sympathetic signs

Hyperthermia
Tachypnea
Tachycardia
Hypertension
Arrhythmia
Hyperkinetic pulmonary edema
Hyperglycemia
Diaphoresis
Piloerection
Restlessness and apprehension
Hyperexcitability and convulsions
Parasympathetic signs

Bronchoconstriction
Bradycardia
Hypotension
Salivation, lacrimation, urination, diarrhea, and gastric emesis (SLUDGE)
Rhinorrhea and bronchorrhea
Goose pimple skin
Loss of bowel and bladder control
Priapism
Dysphagia
Miosis
Generalized weakness
Somatic signs

Rigid spastic muscle of the limbs and torso
Involuntary muscle spasm, twitching, clonus, and contractures
Alternating opisthotonos and opisthotonus from inactivation of sodium channels, leading to increased sodium and calcium uptake
Increased tendon reflexes, especially prolongation of the relaxation phase
Piloerection accompanied by goose pimples
Cranial nerve signs

Classic rotary eye movement may result in ptosis, nystagmus, and blurred vision.
Mydriasis is a sign.
Patients may have tongue fasciculations.
Dysphagia, dysarthria, and stridor occur secondary to pharyngeal reflex loss or muscle spasm.
Patients may present with excessive salivation and drooling.
Peripheral nervous system signs - Intense local burning pain with minimal swelling at sting site, followed by ascending numbness and tingling, then paralysis and convulsions
Nonneurologic systemic signs
Cardiovascular signs - Usually follow a pattern of a hyperdynamic phase followed by a hypodynamic phase

Hypertension is described as follows:

Secondary to catecholamine and renin stimulation
Observed as early as within 4 minutes after the sting
Lasts a few hours
High enough to produce hypertensive encephalopathy
Hypotension - Less common and occurs secondary to excess acetylcholine or catecholamine depletion
Tachycardia is greater than 130 beats per minute, although bradycardia can be observed.
Transient apical pansystolic murmur is consistent with papillary muscle damage.
Cardiovascular collapse occurs secondary to biventricular dysfunction and profuse loss of fluids from sweating, vomiting, diarrhea, and hypersalivation.

Observed in 7-38% of cardiovascular cases
Mild envenomation - Vascular effect with vasoconstriction hypertension
Moderate envenomation - Left ventricular failure hypotension with and without an elevated pulmonary artery wedge pressure, depending on fluid status of the patient
Severe envenomation - Biventricular cardiogenic shock
Cardiac dysfunctions attributed to catecholamine-induced increases in myocardial metabolism oxygen demand (leading to myocardial ischemia–induced myocardial hypoperfusion) and to the direct effects of the toxin (leading to myocarditis)
Respiratory signs

Tachypnea may be present.
Pulmonary edema with hemoptysis and a normal-sized heart is observed in 7-32% of respiratory cases. This is secondary to a direct toxin-induced increased pulmonary vessel permeability effect and is also secondary to catecholamine-induced effects of hypoxia and intracellular calcium accumulation, which leads to a decrease in left ventricular compliance with resultant ventricular dilation and diastolic dysfunction.
Respiratory failure may occur secondary to diaphragm paralysis, alveolar hypoventilation, and bronchorrhea.
Allergic signs

Patients may have urticaria.
Angioedema is reported.
Patients may present with bronchospasm.
Anaphylaxis is possible.
Gastrointestinal signs

Patients may present with excessive salivation.
Dysphagia is possible.
Nausea and vomiting are reported.
Gastric hyperdistention occurs secondary to vagal stimulation.
Increased gastric acid output may lead to gastric ulcers.
Acute pancreatitis may lead to hyperglycemia.
Liver glycogenolysis may occur from catecholamine stimulation.
Toxic Hepatitis
Genitourinary signs

Patients have decreased renal plasma flow.
Toxin-induced acute tubular necrosis renal failure may occur.
Rhabdomyolysis renal failure may result from venom-induced excessive motor activity.
Priapism may occur secondary to cholinergic stimulation. One small study by Bawaskar (1982) found a positive prognostic correlation to the development of cardiac manifestations following scorpion stings.3
Hematological signs

Platelet aggregation may occur because of catecholamine stimulation.
Disseminated intravascular coagulation with massive hemorrhage may result from venom-induced defibrination.
Metabolic signs

Hyperglycemia may occur from catecholamine-induced hepatic glycogenolysis, pancreatitis, and insulin inhibition.
Increased lactic acidosis may occur from hypoxia and venom-induced increased lactase dehydrogenase activity.
Patients may have an electrolyte imbalance and dehydration from hypersalivation, vomiting, diaphoresis, and diarrhea.
Pregnancy signs - Toxin-induced uterine contraction
Symptoms predictive of hospital admission


Priapism (odds ratio 150.59)
Vomiting (odds ratio 15.82)
Systolic blood pressure (SBP) greater than 160 (odds ratio 13.38)
Temperature greater than 38º C (odds ratio 3.66)
Heart rate greater than 100 beats per minute (odds ratio 3.35)
Symptomology of specific scorpion species

Mesobuthus, Tityus, and Leiurus - Tend to cause severe cardiovascular symptoms
Centruroides - Tend to cause neurological symptoms
Hemiscorpius - Tend to cause tissue necrosis

Causes
Scorpions are shy creatures and only sting if threatened, cornered, or disturbed (eg, being sat or stepped upon).
Curious individuals are at risk because of increased interaction with the scorpion.
The median lethal dose 50 (LD50) of various scorpion venoms in mg/kg of a subcutaneous injection into mice and the territorial distribution are listed below. Unfortunately, humans are much more sensitive than mice.

Leiurus quinquestriatus (Middle East) - 0.25 mg/kg
Androctonus crassicauda (Saudi Arabia) - 0.08-0.5 mg/kg
Centruroides noxius (Mexico) - 0.26 mg/kg
Androctonus mauritanicus (North Africa) - 0.32 mg/kg
Centruroides santa maria (Central America) - 0.39 mg/kg
Tityus serrulatus (Brazil) - 0.43 mg/kg
Buthus occitanus (North Africa) - 0.9 mg/kg
Centruroides sculpturatus (Southwest United States) - 1.12 mg/kg
Mesobuthus eupeus (Iran) - 1.45 mg/kg
Generally, most lethal scorpions have an LD50 below 1.5 mg/kg.
The average yield per scorpion via electrical excitation of the venom gland for a few species is listed below.

Tityus species - 0.39-0.62 mg
L quinquestriatus - 0.62 mg
Buthus species - 0.38-1.5 mg
Milking the venom gland produces approximately a 4-fold increase in yield amount compared to electrical excitation.



DIFFERENTIALS

Botulism
Tetanus
Toxicity, Organophosphate

Other Problems to be Considered

Myasthenia gravis
Diphtheria
Guillain-Barré syndrome
Neuroleptic overdose
Sympathomimetic overdose
Venomous jellyfish, snake, and lizard envenomation



WORKUP

Lab Studies

Obtain a CBC count for leukocytosis and hemolysis in patients with stings from the Hemiscorpius species.
Electrolyte evaluation is warranted in patients with venom-induced salivation, vomiting, and diarrhea.
Coagulation parameters should be measured for venom-induced defibrination because, at high concentrations, the venom is an anticoagulant.
Glucose levels should be measured to evaluate for hyperglycemia from liver and pancreas dysfunction.
Creatine kinase and urinalysis help evaluate for venom-induced excessive motor rhabdomyolysis.
Obtain amylase/lipase values to assess for pancreatitis from Tityus trinitatis stings.
Patients may have increased aspartate aminotransferase and alanine aminotransferase levels from venom-induced liver cell destruction.
Increased catecholamine, aldosterone, renin angiotensin, and antidiuretic hormone levels are detected a few hours after the sting. The increased levels persist for 6 hours, after which a gradual decline occurs.
Interleukin (IL)–1 levels are elevated in all envenomations.
High levels of IL-6, interferon-gamma, and granulocyte-macrophage colony-stimulating factor are present in severe envenomations.
Radiolabeled antibodies or immunoenzymatic assays help quantify the serum venom level because an association exists between the clinical signs of envenomation and this level.

Imaging Studies

Unilateral pulmonary edema may be seen on chest x-ray films because of the venom effect on pulmonary vascular permeability.
Echocardiography findings are discussed as follows:

Echocardiography is more sensitive than electrocardiography and creatine kinase assays for assessing myocardial compromise after a scorpion sting.
Findings show a diffuse global biventricular hypokinesis with a decreased left and right ventricular ejection fraction of approximately 0.14-0.38. This dysfunction can appear just a few hours after the sting and usually normalizes within 4-8 days.
Serial echocardiography findings show that the return of left ventricular function to a normal state correlates to clinical cardiorespiratory improvement.
Color-flow Doppler study findings show mitral incompetence, probably secondary to venom-induced dilated cardiomyopathy.

Other Tests

Arterial blood gas determinations show a decrease in arterial oxygenation tension and an increase in PCO2 within 15 minutes of the envenomation, findings consistent with mild metabolic acidosis.
Pulmonary artery catheterization findings may include the following:

Elevated systemic vascular resistance occurs up to 4 times the normal level, with elevated mean arterial pressure (MAP) of 203 mm Hg.
Left ventricular failure produces a MAP of 57-69 mm Hg.
Biventricular failure produces a MAP of 47 mm Hg.
Low cardiac index occurs with elevated filling pressures.
Perform serial spirometry measurements to help detect impending venom-induced diaphragmatic failure.
Electrocardiogram

ECG changes persist for 10-12 days before normalizing.
ECG changes are observed in 63% of children who have been envenomated.
Rhythm disturbances are not dose-dependent but are related to the venom composition.
Sinus tachycardia - Most common rhythm
QTc prolongation - 53%
ST changes - 39%
T-wave inversion - 39%
Ventricular repolarization abnormalities - 15%
Bundle-branch block - 12.8%
First-degree block - 10.2%
A possible sequence of ECG changes has been noted. This sequence starts with bizarre, broad-notched, biphasic, peaked T waves with a beat-to-beat variation. This bizarre T wave is followed by the appearance of tiny Q waves and then atrioventricular dissociation with an accelerated junctional rhythm.

Procedures

Cerebrospinal fluid pleocytosis is evident on spinal tap studies.

Histologic Findings
The local sting site shows mixed inflammatory cell infiltrates with eosinophils scattered among collagen bundles in an edematous dermis. Myocardial changes, which are most prominent at the papillary muscle and subendocardial region, include focal myocardial necrosis; myofibril destruction, especially at the I band; fine fatty deposits in the cardiac muscle fibers; interstitial edema; and increased cellularity, mainly lymphocytes and monocytes. Changes resemble interstitial hypoxia-induced myocarditis caused by large doses of catecholamines.

TREATMENT


Medical Care
Because the clinical manifestations and severity of the symptoms vary among patients, individualize management of scorpion stings. Furthermore, frequent patient monitoring allows earlier recognition of the life-threatening problems of scorpion envenomation. Treatment generally consists of moving the patient away from the scorpion and stabilizing the patient's airway and vital signs, followed by administration of antivenin and institution of symptomatic and local treatment.


Local treatment is discussed as follows:

A negative-pressure extraction device (ie, the extractor) may be useful, although the benefit is unproven. The extractor creates a negative pressure of 1 atm. Apply it to the sting site after incision. Oral extraction is contraindicated.
Use ice bags to reduce pain and to slow the absorption of venom via vasoconstriction. This is most effective during the first 2 hours following the sting.
Immobilize the affected part in a functional position below the level of the heart to delay venom absorption.
Calm the patient to lower the heart rate and blood pressure, thus limiting the spread of the venom.
For medical delay secondary to remoteness, consider applying a lymphatic-venous compression wrap 1 inch proximal to the sting site to reduce superficial venous and lymphatic flow of the venom but not to stop the arterial flow. Only remove this wrap when the provider is ready to administer systemic support. The drawback of this wrap is that it may intensify the local effects of the venom.
Apply a topical or local anesthetic agent to the wound to decrease paresthesia; this tends to be more effective than opiates.
Administer local wound care and topical antibiotic to the wound.
Administer tetanus prophylaxis.
Administer systemic antibiotics if signs of secondary infection occur.
Administer muscle relaxants for severe muscle spasms (ie, benzodiazepines.)
Systemic treatment is instituted by directing supportive care toward the organ specifically affected by the venom.
Establish airway, breathing, and circulation (ie, ABCs) to provide adequate airway, ventilation, and perfusion.
Monitor vital signs (eg, pulse oximetry; heart rate, blood pressure, and respiratory rate monitor).
Use invasive monitoring for patients who are unstable and hemodynamic.
Administer oxygen.
Administer intravenous fluids to help prevent hypovolemia from vomiting, diarrhea, sweating, hypersalivation, and insensible water loss from a tropical environment.
Perform intubation and institute mechanical ventilation with end-tidal carbon dioxide monitoring for patients in respiratory distress.
For hyperdynamic cardiovascular changes, administration of a combination of beta-blockers with sympathetic alpha-blockers is most effective in reversing this venom-induced effect. Avoid using beta-blockers alone because this leads to an unopposed alpha-adrenergic effect. Also, nitrates can be used for hypertension and myocardial ischemia.
For hypodynamic cardiac changes, a titrated monitored fluid infusion with afterload reduction helps reduce mortality. A diuretic may be used for pulmonary edema in the absence of hypovolemia, but an afterload reducer, such as prazosin, nifedipine, nitroprusside, hydralazine, or angiotensin-converting enzyme inhibitors, is better. Inotropic medications, such as digitalis, have little effect, while dopamine aggravates the myocardial damage through catecholaminelike actions. Dobutamine seems to be a better choice for the inotropic effect. Finally, a pressor such as norepinephrine can be used as a last resort to correct hypotension refractory to fluid therapy.
Administer atropine to counter venom-induced parasympathomimetic effects.
Insulin administration in scorpion envenomation animal experiments has helped the vital organs to use metabolic substrates more efficiently, thus preventing venom-induced multiorgan failure, especially cardiopulmonary failure. Unfortunately, no human studies have been conducted.
Administer barbiturates and/or a benzodiazepine continuous infusion for severe excessive motor activity.
The use of steroids to decrease shock and edema is of unproven benefit.
Antivenin is the treatment of choice after supportive care is established. The quantity to be used is determined by the clinical severity of patients and by their evolution over time. Unfortunately, predicting the evolution of symptoms and, thus, the amount of antivenin that is needed in the future, is difficult.

The antivenin significantly decreases the level of circulating unbound venom within an hour. The persistence of symptoms after the administration of antivenin is due to the inability of the antivenin to neutralize scorpion toxins already bound to their target receptors.
Time guidelines for the disappearance of symptoms after antivenin administration are as follows:
Centruroides antivenin: Severe neurologic symptoms reverse in 15-30 min. Mild-to-moderate neurologic symptoms reverse in 45-90 min.
Non-Centruroides antivenin: In the first hour, local pain abates. In 6-12 hours, agitation, sweating, and hyperglycemia abate. In 6-24 hours, cardiorespiratory symptoms abate.
While an anaphylaxis reaction to the antivenin is possible, the patient is at lower risk for this than with other antivenins for other envenomations because of the huge release of catecholamines induced by the scorpion venom. However, the larger the dose of antivenin, the greater the chance for serum sickness.
A vaccine preparation was tried in experimental animals but was not pursued because of the need to prepare different antigens according to different geographical areas and to different species of scorpions living in the same area.
In some cases, be aware that meperidine and morphine may potentiate the venom. Also, the concurrent use of barbiturates and narcotics may add to the respiratory depression in patients who have been envenomated.

Consultations

Consultations with personnel at local poison control centers is warranted (eg, Arizona Poison Control, phone 602-253-3334), especially for stings from C sculpturatus because the antivenin is made in Arizona.
The Antivenom Index lists locations, amounts, and types of antivenin stored at different zoos. This index is published jointly by the American Association of Poison Control Centers and the American Zoo and Aquarium Association.

Activity

Rest and immobilization of the sting site is recommended to prevent rapid absorption of the venom into the circulation.

MEDICATION

The goals of pharmacotherapy are to reduce morbidity, to prevent complications, and to neutralize the toxin.


Drug Category: Antivenins

Scorpion toxins are not good antigens because of small size and poor immunogenicity. They do not induce antibodies that cross-react against toxins of other scorpion species unless a 95% amino acid sequence homology exists between the 2 toxins. Thus, no universal antivenin is available. Instead, 22 types of scorpion antivenin exist.

Furthermore, the neurotoxin component of the scorpion venom tends to be the least immunogenic, resulting in the low efficiency for neurological complications. It usually is prepared from horses because they yield larger quantities. Sheep, goat, or bovine antivenin may be prepared if patient sensitivity to horse serum occurs.

A recent idea was to mix a batch of different scorpion antivenin together to create a universal antivenin, but this exposes the patient to unnecessary antivenin from scorpion species not from the patient's region.

Perform a skin test prior to administering the antivenin. First, dilute 0.1 mL of antivenin in a 1:10 ratio with isotonic sodium chloride solution. Second, administer 0.2 mL intradermally. A positive test result is if a wheal develops within 10 minutes. The skin test has a sensitivity of 96% and a specificity of 68%.

The best result occurs when antivenin is administered as early as possible (preferably within the first 2 h after the sting) and with adequate quantities to neutralize the venom (usually 50-100 times the LD50 amount). A decrease in curative effects occurs with longer sting-serotherapy delay and administration of insufficient amounts of antivenin.

Drug Name USA-APL Centruroides scorpion antivenin
Description Used to neutralize toxins from scorpions. Produced in Arizona (for use in Arizona only). Not approved by FDA. Use remains controversial, but many physicians recommend it in grade III and IV envenomations. Shown to produce rapid resolution of systemic symptoms but does not affect pain or paresthesias. Results in resolution of symptoms within min to 2 h after administration. Antivenin treatment is based on venom burden, not patient's size. The smaller the victim, the more important it is to administer the full dose because of the venom dose-dependent severity.
Adult Dose Grade I and II: None
Grade III and IV: 1 vial (5 mL) in 50 mL saline IV over 30 min; if severe symptoms still persist after 1 h, repeat once prn
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity; may administer in severe envenomation, despite hypersensitivity
Interactions None reported
Pregnancy C - Safety for use during pregnancy has not been established.

Precautions Due to presence of horse serum, agents for emergency treatment of anaphylaxis should be available; premedicate with antihistamines or steroids



Drug Category: Benzodiazepines

By increasing the action of GABA (inhibitory neurotransmitter), counteract scorpion-induced excessive motor activity and nervous system excitation.

Drug Name Lorazepam (Ativan)
Description Sedative hypnotic with short onset of effects and relatively long half-life.
By increasing action of GABA, which is a major inhibitory neurotransmitter in the brain, may depress all levels of CNS, including limbic and reticular formation.
Adult Dose 1-4 mg IV over 2-5 min; may repeat dose in 10-15 min prn
Pediatric Dose 0.05 mg/kg IV over 2-5 min; may repeat dose in 10-15 min prn
Contraindications Documented hypersensitivity; preexisting CNS depression, hypotension, and narrow-angle glaucoma
Interactions Toxicity in CNS increases when used concurrently with alcohol, phenothiazines, barbiturates, and MAOIs
Pregnancy D - Unsafe in pregnancy

Precautions Caution in renal or hepatic impairment, myasthenia gravis, organic brain syndrome, Parkinson disease, hypotension, and respiratory depression

Drug Name Midazolam (Versed)
Description Short-acting benzodiazepine that can be administered in continuous infusion for severe nervous system excitation.
Adult Dose 0.1 mg/kg IV bolus then 0.1 mg/kg/h; titrate dose upward q5min until symptoms controlled
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity; preexisting hypotension, narrow-angle glaucoma, and sensitivity to propylene glycol (the diluent)
Interactions Sedative effects may be antagonized by theophyllines; narcotics and erythromycin may accentuate sedative effects because of decreased clearance
Pregnancy D - Unsafe in pregnancy

Precautions Caution in congestive heart failure, pulmonary disease, renal impairment, and hepatic failure; may require intubation and pressor support




Drug Category: Barbiturates

Used to counteract scorpion-induced hyperactivity.

Drug Name Pentobarbital (Nembutal)
Description Short-acting barbiturate with sedative and anticonvulsant properties used to produce barbiturate coma for severe CNS hyperexcitation. Requires patient intubation prior to use.
Adult Dose 12 mg/kg IV bolus, then 5 mg/kg/h; titrate to symptom abatement or EEG inactivity
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity; liver failure; porphyria
Interactions Concomitant use with alcohol may produce additive CNS effects and death; chloramphenicol may inhibit metabolism; may enhance chloramphenicol metabolism; MAOIs may enhance sedative effects of barbiturates; valproic acid appears to decrease barbiturate metabolism, increasing toxicity; barbiturates can decrease effects of anticoagulants (patients may require dosage adjustments if barbiturates are added to or withdrawn from regimen); decreased contraceptive effect may occur due to induction of microsomal enzymes (alternate form of birth control is suggested); barbiturates may decrease corticosteroid and digitoxin effects through induction of hepatic microsomal enzymes that increase metabolism; barbiturates decrease theophylline levels and may decrease effects; may decrease verapamil bioavailability
Pregnancy D - Unsafe in pregnancy

Precautions Patient may become tolerant to hypnotic effects; caution in patients with hypovolemic shock, respiratory dysfunction, hypotension, renal dysfunction, congestive heart failure, previous addiction to sedative hypnotics, and congestive heart failure



Drug Category: Local anesthetics

Tend to be more effective than opiates to control paresthesia and pain at the sting site.

Drug Name Bupivacaine (Marcaine)
Description May reduce pain by slowing nerve impulse propagation and reducing action potential, which, in turn, prevents initiation and conduction of nerve impulses.
Adult Dose 1.25 mg/kg/dose intralesionally until pain subsides; not to exceed 3-4 mg/kg
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity; septicemia, spinal deformities, severe hypertension, and existing neurologic disease
Interactions May enhance effects of CNS depressants; coadministration may increase toxicity of MAOIs, TCAs, beta-blockers, vasopressors, and phenothiazines
Pregnancy C - Safety for use during pregnancy has not been established.

Precautions Test a dose and monitor for CNS toxicity, cardiovascular toxicity, and signs of unintended intrathecal administration; caution with inflammation or sepsis in region of proposed injection; monitor patient's state of consciousness after each injection; caution in hypertension, cerebral vascular insufficiency, peripheral vascular disease or heart block, hypoxia, hypovolemia, and arteriosclerotic heart disease



Drug Category: Adrenergic blocking agents and vasodilators

Used to counteract the scorpion-induced adrenergic cardiovascular effect.

Drug Name Labetalol (Normodyne, Trandate)
Description Blocks beta1-adrenergic, alpha-adrenergic, and beta2-adrenergic receptor sites, decreasing blood pressure.
Adult Dose 20 mg IV then 40 mg IV repeated q10-15min until BP controlled or until the maximum accumulative dose of 300 mg is reached
Pediatric Dose Not established
Suggested: 0.1 mg/kg IV; repeat q15-20min as last resort
Contraindications Documented hypersensitivity; cardiogenic shock, pulmonary edema, bradycardia, atrioventricular block, uncompensated congestive heart failure, reactive airway disease, and severe bradycardia
Interactions Decreases effect of diuretics and increases toxicity of methotrexate, lithium, and salicylates; may diminish reflex tachycardia resulting from nitroglycerin use without interfering with hypotensive effects; cimetidine may increase blood levels; glutethimide may decrease effects by inducing microsomal enzymes
Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions Caution in impaired hepatic function; discontinue therapy if signs of liver dysfunction occur; in elderly patients, a lower response rate and higher incidence of toxicity may be observed; caution with concomitant beta-blockers; beware of continued hypertension despite decreasing heart rate due to insufficient alpha blockade

Drug Name Prazosin (Minipress)
Description Counteracts scorpion-induced adrenergic cardiovascular effects. May improve pulmonary edema through vasodilatory effects.
Adult Dose 1 mg PO bid/tid; not to exceed 5 mg/dose
Pediatric Dose Not established
Contraindications Documented hypersensitivity
Interactions Acute postural hypotensive reaction from beta-blockers may worsen; indomethacin may decrease antihypertensive activity; verapamil may increase serum levels and may increase patient's sensitivity to prazosin-induced postural hypotension; may decrease antihypertensive effects of clonidine
Pregnancy C - Safety for use during pregnancy has not been established.

Precautions Caution in renal insufficiency and hypotension


Drug Name Hydralazine (Apresoline)
Description Decreases systemic resistance through direct vasodilation of arterioles
Adult Dose 10-20 mg IV q4-6h
Pediatric Dose Not established
Contraindications Documented hypersensitivity
Interactions MAOIs and beta-blockers may increase toxicity
Pregnancy B - Usually safe but benefits must outweigh the risks.

Precautions May cause hydralazine-induced tachycardia, SLE-type syndrome, and peripheral neuritis

Drug Category: Anticholinergics

Used to counteract scorpion-induced cholinergic symptoms.

Drug Name Atropine (Atropair)
Description Used to increase heart rate through vagolytic effects, causing an increase in cardiac output. Also treats bronchorrhea associated with scorpion envenomations.
Adult Dose 0.5 mg IV q15min until desired effect (Note: for vagolytic cardiac effects, there is a 3-mg limit)
Pediatric Dose 0.01 mg/kg IV q15min until desired effect (Note: For cardiac vagolytic effects, there is a 3-mg limit)
Contraindications Documented hypersensitivity; thyrotoxicosis, narrow-angle glaucoma, and tachycardia
Interactions Coadministration with other anticholinergics has additive effects; pharmacologic effects of atenolol and digoxin may increase; antipsychotic effects of phenothiazines may decrease; TCAs with anticholinergic activity may increase effects
Pregnancy C - Safety for use during pregnancy has not been established.

Precautions Avoid in Down syndrome and/or children with brain damage to prevent hyperreactive response; also avoid in patients with coronary heart disease, tachycardia, congestive heart failure, cardiac arrhythmias, and hypertension; caution in patients with peritonitis, ulcerative colitis, hepatic disease, and hiatal hernia with reflux esophagitis; in patients with prostatic hypertrophy, prostatism may cause dysuria and may require catheterization; monitor patients for anticholinergic effects (eg, hyperthermia, dilated pupils, dry mucous membrane, tachycardia)



Drug Category: Vasopressors/inotropics

Used to combat hypotension refractory to IV fluid therapy.

Drug Name Norepinephrine (Levophed)
Description Indicated for persistent hypotension not responsive to judicious fluid loading and sodium bicarbonate.
Adult Dose 0.05-0.15 mcg/kg/min IV infusion; titrate to effect
Pediatric Dose 0.1-1 mcg/kg/min IV infusion; titrate to effect
Contraindications Documented hypersensitivity
Interactions Chlorpromazine enhances pressor response by blocking reflex bradycardia caused by norepinephrine
Pregnancy D - Unsafe in pregnancy

Precautions Administer into a large vein because extravasation may cause severe tissue necrosis; caution in occlusive vascular disease

Drug Name Dobutamine (Dobutrex)
Description Sympathomimetic amine with stronger beta than alpha effects. Increases inotropic state with afterload reduction.
Adult Dose 5-20 mcg/kg/min IV continuous infusion, titrate to desired response; not to exceed 40 mcg/kg/min
Pediatric Dose Administer as in adults
Contraindications Documented hypersensitivity
Interactions Beta-blockers antagonize effects
Pregnancy B - Usually safe but benefits must outweigh the risks.

Precautions Higher dosages may cause increase in heart rate and exacerbate hypotension


Drug Name Milrinone (Primacor)
Description Positive inotropic agent and vasodilator with little chronotropic activity.
Adult Dose 50 mcg/kg loading dose IV over 10 min, followed by 0.375-0.75 mcg/kg/min continuous IV infusion
Pediatric Dose Administer as in adults because has been used in the pediatric ICUs, although safety and efficacy not well established
Contraindications Documented hypersensitivity
Interactions May precipitate if infused in the same IV line as furosemide
Pregnancy C - Safety for use during pregnancy has not been established.

Precautions Slow or stop infusion in patients showing excessive decreases in blood pressure





FOLLOW-UP


Further Inpatient Care

Inpatient care is dictated by the severity of the envenomation and consists of stabilizing the patient, neutralizing the venom, providing supportive therapies, and preventing complications.
Treat all patients with severe systemic symptoms in an intensive care unit (ICU) setting because of the unpredictability of the symptomology, the risks associated with antivenin administration, and the need for airway or blood pressure support.
Young children do worse than adults; thus, they may require observation in ICU more frequently.

Further Outpatient Care

Patients displaying local nonascending reactions to the venom may be discharged after 6 hours of observation, with close follow-up. If the patient was treated with a pressure bandage, the symptoms may be delayed and inpatient observation is warranted.
If an antivenin is administered, monitor the patient for serum sickness over next the few weeks.
Inform the patient about the possibility of persistent pain or paresthesia at the sting site.

Transfer

Transfer is appropriate if antivenin administration or ICU treatments are not available at the institution where the patient initially presents.

Deterrence/Prevention

Check shoes, gloves, clothing, and backpacks for scorpions prior to use.
Keep yards free of debris, which can serve as a place for scorpions to hide.
Make sure windows and doors fit tightly to prevent scorpions from entering the house.
Avoid walking barefoot, especially at night when scorpions are active.
Use a Wood lamp at night because the cuticle of the Centruroides species is fluorescent under ultraviolet light.
Methods of biological control of scorpions include introducing chickens, ducks, and owls to the area.
Methods of chemical control of scorpions include using organophosphates, pyrethrins, and chlorinated hydrocarbons.

Complications

Dilated cardiomyopathy
Ankylosis of small joints if the sting occurs at a joint
Rhabdomyolysis
Persistent paresthesia
Antivenin anaphylaxis and serum sickness
Iatrogenic, high-dose, sedative-hypnotic respiratory arrest

Prognosis

The prognosis depends on which species of scorpion stung the patient.
Symptoms generally persist for 10-48 hours. If the victim survives the first few hours without severe cardiorespiratory or neurologic symptoms, the prognosis is usually good. Furthermore, surviving the first 24 hours after a scorpion sting also carries a good prognosis.
A worse prognosis can be expected with the presence of systemic symptoms such as cardiovascular collapse, respiratory failure, seizures, and coma.

Patient Education

Educate all patients about methods to avoid scorpions (see Deterrence/Prevention).



MISCELLANEOUS

Medical/Legal Pitfalls
Failure to stabilize the airway and vital signs prior to any specific intervention against the venom
Failure to adequately treat the patient because of underestimation of the envenomation effects
Failure to admit the patient for systemic symptoms
Failure to use ICU monitoring for patients who are severely envenomated
Failure to warn the patient of potential complications and to arrange a follow-up evaluation
Failure to obtain informed consent before antivenin administration
Heavy combination use of barbiturates and narcotics for the hyperdynamic state, leading to concurrent respiratory arrest, especially in pediatric patients


Source
http://www.emedicine.com/med/TOPIC2081.HTM


Regards
Robin

Excellent information, Robin! I'll move this to the sting reports section as a sticky, if that's alright with you (if not alright, I'll un-move it).

I was thinking the same thing. But i was to busy merging the four post into one.

Hi guys!

I`m sorry for all the posts on the same subject, but the fora has some kind of maximum limit for letters per post I think?

When I think about it, this is actually the right place to post it




Regards
Robin

Dont worry I really appriciate the effort. Plus it keep us Admins and Mods on our toes.
-Eddy

really good info, man! how long did it take you to type all that?

Well i doubt it was typed out. Great job finding that info though, and that site it has all sorts of other topics to read. I bet it was still a pain formating it to fit in the forum better though.

spikexspiegel wrote:

Well i doubt it was typed out. Great job finding that info though, and that site it has all sorts of other topics to read. I bet it was still a pain formating it to fit in the forum better though.

Not really, I`m very skilled in copy/paste

This was the most interresting scorpion topics(This , togheter with the death stalker sting rapport) on the page listed as source, but you can find a lot of other good information there as well.

Regards
Robin