All symptomatic patients from elapid envenomation require ICU admission for anticipated respiratory failure. Asymptomatic patients receiving elapid antivenin will need

DISPOSITION

..... Admission

All symptomatic patients from elapid envenomation

require ICU admission for anticipated respiratory failure.

Asymptomatic patients receiving elapid antivenin will need

to be observed for neurologic symptoms. Asymptomatic

patients not receiving antivenin should also be observed

for 24 hours, because risk stratification in these patients

has been found to be so difficult.

..... Discharge

For crotaline snakebites, patients with an apparent "dry

bite" or those without bite marks can be observed in the

ED for 8 hours and discharged without focused therapy.

Patients with minor envenomations, characterized by only

mild local findings on skin examination with the absence

of hematologic or systemic abnormalities, should be

observed for 12-24 hours with repeat blood testing and

may be discharged home without antivenom administra ­

tion if their symptoms remain mild. Patients requiring

antivenom administration should be observed for 18-24 hours

after control of symptoms was obtained. These patients

will also need close outpatient follow-up for repeat

laboratory work to evaluate for any worsening hematologic

abnormalities and must be given very strict discharge

instructions.

SUGGESTED READING

Dart RC, Daly FFS. Reptile bites. In: Tintinalli JE, Stapczynski JS,

Cline DM, Ma OJ, Cydulka RK, Meckler GD. Tintinalli's

Emergency Medicine: A Comprehensive Study Guide.

7th Ed. New York, NY: McGraw-Hill, 20 1 1, pp. 1354-1358.

Hahn IH. Arthropods. In: Nelson LS, Lewin NA, Howland MA,

Hoffman RS, Goldfrank LR, Flomenbaum NE. Goldfrank's

Toxicology Emergencies. 9th ed. New York, NY: McGrawHill Medical, 20 11, pp. 1561-158 1.

Isbister GK, Fan HW. Spider bite. Lancet. 20 11;378: 2039.

Lavonas EJ, Ruha AM, Banner W, at al. Unified treatment algorithm for the management of crotaline snakebite in the

United States: results of an evidence-informed consensus

workshop. BMC Emerg Med. 201 1;11:2.

Riley BD, Pizon AF, Ruha AM. Snakes and other reptiles. In:

Nelson LS, Lewin NA, Howland MA, Hoffman RS, Goldfrank

LR, Flomenbaum NE. Goldfrank's Toxicology Emergencies.

9th ed. New York, NY: McGraw-Hill Medical, 20 1 1,

pp. 1 60 1-1610.

Diabetic Emergencies

Sarah E. Ronan- Bentle, MD

Key Points

• Hyperg lycemia causes an osmotic diuresis that may

result in dehydration.

• Patients with diabetic ketoacidosis (DKA) and

hyperglycemic hyperosmolar state (HHS) are treated

with intravenous fluids and insulin. Potassium

supplementation should begin as soon as the potassium

level is in the normal range.

INTRODUCTION

Diabetes mellitus is a common disorder and is present in

6% of the population in the United States. Diabetes

mellitus is defined as fasting blood glucose > 126 mg/dL on

2 separate occasions or a random glucose >200 mg/dL plus

the classic symptoms of hyperglycemia (ie, polyuria,

polydipsia). Derangement of glucose homeostasis is a

continuum that ranges from hypoglycemia on one extreme

to diabetic ketoacidosis (DKA) on the other end of the

spectrum.

Hyperglycemia, even in the absence of DKA or

hyperglycemic hyperosmolar state (HHS), has many

deleterious effects. An osmotic diuresis occurs when an

elevated glucose level overwhelms the kidneys and begins

to pull electrolytes and water into the urine. In the healthy

individual, serum glucose of 240 mg!dL is required before

glucose is found in the urine. Additionally, hyperglycemia

impairs leukocyte function and wound healing, making

patients prone to infection. Chronic hyperglycemia causes

renal failure, blindness, neuropathy, and atherosclerosis.

Diabetic ketosis is an intermediate metabolic state

between hyperglycemia and ketoacidosis. Patients have an

inadequate amount of insulin to provide the necessary

energy substrates to the cell. As a result, lipolysis is

• Both DKA and HHS are often preci pitated by another

ill ness, frequently infection. An attempt should be

made to search for and treat any precipitating illness.

• When treating patients with HHS, it is important to

follow sodium and serum osmolal ity measurements to

document return to normal values.

stimulated to provide ketone bodies that can be used as

substrates by the brain and other tissues. The ketone

bodiesincludeacetoacetate,acetone,andP-hydroxybutyrate.

DKA is defined as blood glucose >250 mg!dL, serum

bicarbonate < 15 mEq/L, ketonemia, and an arterial pH <7.3.

DKA is present in 5-10% of hospitalized patients. It is the

presenting illness of diabetes mellitus in 1 5-25% of patients.

When making the diagnosis of DKA, the physician should

attempt to determine what has precipitated the illness. The

most common causes of DKA are the "3 I's": insulin lack,

ischemia (cardiac), and infection. The mortality rate of

patients with DKA is approximately 5% and most often is

attributable to concomitant illness.

In DKA, reduced circulatory insulin levels do not allow

glucose to reach the intracellular space. In response, the

cell stimulates lipolysis, which provides the body with

glycerol (substrate for gluconeogenesis) and free fatty

acids. Free fatty acids are a precursor to the ketoacids,

acetoacetate, acetone, and P-hydroxybutyrate. The ketone

bodies can be used as an energy source, but when they are

present in excess, metabolic acidosis results.

HHS occurs when a hyperglycemic osmotic diuresis

causes extreme dehydration. Defining features include

a serum glucose >600 mg/dL, plasma osmolality

>320 mOsm/L, and the absence of ketoacidosis. HHS is

280

DIABETIC EMERGENCIES

most common in elderly individuals. It results in <1 o/o of

diabetes-related hospital admissions, but has a reported

mortality rate of 20-60%. HHS occurs when a prolonged

osmotic diuresis from hyperglycemia results in severe dehydration and an elevated serum osmolality. Concurrent

medical illness is very common and is often a precipitating

cause of HHS.

CLINICAL PRESENTATION

� History

Patients with hyperglycemia report polydipsia and

polyuria. They may also present with blurry vision owing

to changes in the shape of the lens induced by osmotic

movements of water. Recovery is spontaneous, but may

take up to 1 month.

 

...,._ Spiders

North American black widow spiders tend to be nonag ­

gressive and only attack when their web is encroached on.

These areas tend to be in dark places, such as garden equipment, shoes, socks, and other clothing. Recluse spiders in

North America tend to cause envenomation in domestic

environments, where they hide in furniture, clothing, and

sheets, particularly if they have not been used or disturbed

for a while. Most recluse bites therefore happen at night or

in the early morning and occur on the thigh, trunk, or

proximal arm.

PHYSICAL EXAMINATION

Focused physical examination includes inspection of the

possible bite area as well as screening for any associated

traumatic injury. Palpation of the bite area and marking of

CHAPTER 65

History & physical exam

Identify snake/spider

Determine clinical effects

Ca ll poison contro l center

Figure 65-5. Envenomation diagnostic algorithm.

any wound margins will assist in deciding whether there is

progression of local tissue injury from envenomation.

However, as was discussed previously, local inspection of

elapid snakebites can be deceptively reassuring. Instead, in

these patients, physical examination may focus on a more

detailed neurologic examination.

DIAGNOSTIC STUDIES

For crotaline envenomations, obtain a complete blood

count (CBC; specifically for hemoglobin and platelet

counts), coagulation studies, and fibrinogen level. If concern

for retained foreign body at a bite site exists, an x-ray may be

obtained.

If there is concern for systemic loxoscelism, a CBC and

coagulation studies are recommended as well as chemistry

panel to assess for renal dysfunction.

MEDICAL DECISION MAKING

If available, a picture of the snake/spider will aid in

identification and further management. A thorough

history and physical examination to determine any clinical

effects, which can be local, hematologic, or systemic, is

performed. Examination of the skin for bite marks to

determine whether significant envenomation has occurred

is unreliable, especially in cases of a coral snake bite.

Contact the poison control center for assistance in

identification and management (Figure 65-5).

TREATMENT

� Snakes

Many field treatments exist particularly for crotaline

snakebites. However, few of them have been found to be

particularly helpful, and many may be quite harmful to the

patient. Such dangerous techniques include but are not

limited to cutting the bite site, attempting to extract venom

from the site (either orally or via commercially available

devices), applying tourniquets to the bitten extremity, or

applying electrical shocks to the victim. Instead, field

management should consist solely of immobilization of

the bitten extremity, limiting the victim's exertion, and

rapidly obtaining medical evacuation and attention.

In the ED, further stabilization measures for crotaline

snakebites include extremity immobilization and elevation,

pain treatment, management of systemic symptoms, and

assessment of tetanus vaccination status. Treatment and

disposition management decisions should always involve

the assistance of a poison control center ( 1-800-222-1222)

or a local toxicologist.

ENVENOMATION

Moderate to severe North American crotaline

envenomations should be treated with Crotalidae polyvalent immune fab ( ovine) snake antivenom ( CroFab). These

envenomations will be characterized by the presence of a

bite site with more than minimal swelling, redness, or

ecchymosis, or one with progression of any of these

findings. Additionally, systemic findings and any

hematologic abnormalities should prompt initiation of

antivenom. Antivenom is given by intravenous infusion of

4-6 vials of antivenom in 250 mL of normal saline given

over 1 hour. lf initial control has been achieved with this

initial dose, the patient should be admitted to an intensive

care unit (ICU) for observation and consideration of

maintenance dosing. lf control was not achieved by the

initial dose, that dose can be repeated.

Prophylactic antibiotics are not recommended for

routine use in crotaline envenomations. Additionally,

unless the patient develops an allergic reaction of some

sort, routine use of steroids is not recommended. Because

of theoretical hematologic effects of nonsteroidal antiinflammatory drugs (NSAIDs), some experts prefer pain

control with opioids.

Because of the deceptively benign appearance of

potentially significant elapid snakebites, the treatment

course is more reflexively conservative than that described

for crotaline envenomations. It was previously recommended

that any patient with bite marks or evidence of skin penetration receive elapid (equine) antivenin. However, the makers

of the product have discontinued manufacture, so there is

currently only very limited supply in endemic areas. In the

event of a suspected elapid snakebite, the poison control

center should be contacted immediately to determine need

for and possible location of any available antivenin.

..... Spiders

Although multiple therapeutic options have been investigated

for black widow spider bites, aggressive supportive symp ­

tomatic care is currently recommended. Studies on the use

of intravenous calcium and Latrodectus antivenoms have

been contradictory and largely unimpressive for appreciable

difference from placebo. It is therefore recommended that

pain associated with black widow spider bites be managed as

other painful conditions would be, with attempts at treating

with NSAIDs, opioids, and/or benzodiazepines as deemed

appropriate.

Multiple specific therapies have also been studied for

loxoscelism. The most dangerous and ill-advised of these

therapies have included shock therapy, liberal use of

prophylactic surgical excision, and dapsone. These thera ­

pies, while ineffective in treating recluse envenomation,

also are thought to cause worsening wound healing

(for shock and surgical excision) or undesirable medication effects (such as methemoglobinemia with dapsone).

Antivenoms are currently investigational and are not

available in the United States. What is instead recommended

is excellent wound care, symptomatic management, and

appropriate focused treatment of potential adverse effects

of systemic loxoscelism.

 

Latrodectus moctons/ with the characteristic

ventral red hourglass. Reproduced with

permission from Knoop KJ, Stack LB, Storrow

AB, et al. The Atlas of Emergency Medicine.

3 rd ed. New York: McGraw-Hill Medical,

2009:505. Photo contributor: Lawrence B.

Stack, MD.

characteristics of the envenomed patient. In 20-25% of

crotaline bites, no significant amount of venom is delivered, resulting in a "dry bite." Multiple grading systems

for crotaline envenomation severity have been developed,

although most of these systems have limited utility in

clinical practice. Instead, the clinical effects of these

envenomations can be divided into 3 major categories:

local/tissue, hematologic, and systemic effects. Local t issue damage from crotaline envenomation can range from

minimal swelling and pain to severe edema, blistering,

ecchymosis, and necrosis. Hematologic effects can be

extreme after moderate to severe envenomations and

include thrombocytopenia, elevated coagulation studies

(prothrombin time and partial thromboplastin t ime), as

well as degradation of fibrinogen. Even with laboratory

evidence of severe coagulopathies, however, most patients

do not develop clinically significant hemorrhage.

Systemic effects are nonspecific; include abdominal pain,

vomiting, diaphoresis, tachycardia, and hypotension; and

may also be related to concomitant fear, anxiety, pain, or

intoxication.

In contrast with crotaline envenomations, patients

with significant elapid envenomations may initially

present with minimal symptoms. The neurologic

systemic symptoms that characterize North American

elapid envenomations are classically delayed for hours,

with reports of patients being asymptomatic up to 13

hours before developing ventilator-requiring r espiratory

failure. It is difficult to determine who with an elapid

exposure will develop symptoms of envenomation, as it

has been estimated that approximately 60% of those

bitten by a coral snake did not have an envenomation.

Alternatively, 15% of those with coral snake envenom ­

ations have no fang marks, and only 40% have any local

swelling.

ENVENOMATION

Figure 65-4. Brown recluse spider, Loxosceles recluso, with the characteristic dorsal violinshaped marking. Photos contributed by R. jason Thu rman, MD. Repri nted from Zafren K,

Thurman Rj, jones 10. Chapter 1 6. Environmental conditions. In: Knoop Kj, Stack LB, Storrow AB,

Thurman Rj, eds. The Atlas of Emergency Medicine. 3rd ed. New York: McGraw-Hill, 201 0 .

...,._ Spiders

The clinical presentation of black widow spider bites is

also referred to as latrodectism. The key feature of this

syndrome is pain, which can be localized, radiating, or

referred. This pain is gradual, beginning upward of an

hour after the time of the bite, and is typically described

as being severe muscle cramping pain in the bitten

extremity, but especially with the North American black

widow spider can involve the abdominal muscles,

mimicking a surgical abdomen. Additional findings in

latrodectism include localized areas of diaphoresis, nau ­

sea, vomiting, restlessness, fasciculations, fear of death

(pavor mortis), and rarely priapism. The constellation of

symptoms called "facies latrodectismica" is also specific to

black widow spider envenomation and is a painful facial

grimace with associated conjunctivitis, blepharitis,

diaphoresis, and trismus.

"Loxoscelism" is the term used to describe envenomation from recluse spiders and can be divided into

cutaneous and viscerocutaneous or systemic forms. Of

significant recluse spider envenomations, the cutaneous

form is the most commonly seen in North America. These

patients will initially have little to no pain at the bite site,

only to develop a more remarkable hemorrhagic or ulcerative painful lesion 2-8 hours after the bite. This progresses

to ulceration and necrosis with surrounding erythema and

induration up to 7 days after the initial bite when an eschar

generally forms. This wound then slowly heals over weeks

to months. Systemic loxoscelism occurs 1-3 days after the

recluse spider bite and is primarily characterized by hemolytic anemia. Clinically, the patient may develop nonspe ­

cific systemic symptoms such as fever, rash, weakness,

arthralgia, nausea, and vomiting. This autoimmune

hemolytic anemia can be accompanied by tluombocytope ­

nia and rhabdomyolysis and rarely progresses to renal

failure and death.

HISTORY

...,._ Snakes

North American snakes rarely attack unprovoked, although

this provocation may be unintentional by the envenomed

patient. Most bites occur during warm months, as snakes

hibernate in the winter. They also more commonly occur

on extremities-the areas of the body most likely to disturb a venomous snake. Young men are at particularly high

risk of being bitten by a venomous snake, and it has been

recognized that snakebites are frequently associated with

alcohol intoxication.

 

elapids will remain attached and "chew'' on their victim to

inject the venom. Although this makes it more difficult fur

these snakes to deliver a clinically significant amount of

venom, it also makes it more difficult to clinically assess a

patient with a potential bite, as there may not be bite or fang

marks in a patient who has had a potentially life-threatening

envenomation.

..... Spiders

Like snakes, there are 2 major groups of spiders that cause

medically significant envenomations in North America: the

black widow (genus Latrodectus) and the brown recluse

(genus Loxosceles). It is difficult to estimate the true incidence of spider bites, because the history of a bite is often ­

times unreliable, with many patients and physicians

reasoning that a rash, abscess, or cellulitis originated from a

spider bite when no spider was seen. Additionally, with the

CHAPTER 65

Figure 65-2. North American cora l snake.

Reproduced with permission from Knoop K}/

Stock LB/ Storrow AB/ et of. The Atlas of

Emergency Medicine. 3rd ed. New York:

McGraw-Hill Medical/ 2009. Figure 1 6.30.

Photo contributor: Steven Holt MD.

possible exception of the female black widow spider, the

general public has difficulty distinguishing medically rele ­

vant spiders from those that are generally benign. That

being said, bites from brown recluse and black widow

spiders can be deadly in extreme circumstances and can

unquestionably cause substantial morbidity and pain.

There are 5 species of black widow spiders found in

the United States. These spiders are medium-sized, typically black colored, and have species-specific ventral

markings. The female Latrodectus mactans has the characteristic red hourglass ventral marking and has a larger

body and fangs than her male counterpart, making the

female more likely to cause envenomation (Figure 65-3 ).

The clinical effects of a black widow spider envenomation

in humans are thought to be caused by the neurotoxin

a-latrotoxin.

There are 2 major species of recluse spiders found in

the United States: the Loxosceles reclusa (brown recluse)

and Loxosceles deserta (desert recluse). The brown recluse

is found primarily in the southern and midwestern United

States, and the desert recluse's range is in the southwestern

portion of the country. North American recluse spiders

are brown to gray-colored with dark dorsal markings

that have a violin pattern, giving it its other names, fiddle ­

back or violin spider (Figure 65-4) . The toxin in recluse

spider bites is complex, but is thought to contain

proinflammatory and necrosis-inducing substances

similar to phospholipase D and hyaluronidase.

CLINICAL PRESENTATION

� Snakes

The severity of a crotaline envenomation depends on

multiple factors, including the amount of venom delivered, the potency of the venom, and the location of the

venom (anatomically and by depth), as well as clinical

Figure 65-3. Black widow spider,

 

Asymptomatic

- CXR, consider labs

(electrolytes, blood count)

- Evaluate primary vs secondary

drowning

- Evaluate for traumatic injury

mit to monitored bed Discharge home

Figure 64-2. Drown ing incidents diag nostic algorithm. CXR, chest x-ray; ICU, intensive care unit.

DISPOSITION

Patient condition will largely determine disposition. Poor

prognostic factors include:

• Submersion for > 10 minutes

• > 10 minutes before initiation of basic life support

measures in an apneic/pulseless patient

• >25 minutes of pulselessness

• Initial temperature <33°C (92°F)

• Initial Glasgow score <5

• Need for cardiopulmonary resuscitation in the ED

• Submersion in water colder than l 0°C (50°F)

• Initial arterial blood gas pH <7.1

� Admission

Admission is indicated for any symptomatic patient. Those

who are intubated, have persistently altered mental status,

are hypothermic, or require high-flow oxygen should be

admitted to an intensive care unit. Cardiac monitoring is

indicated for any patient with oxygen requirements or

changes on chest radiograph.

� Discharge

Patients who present asymptomatic and remain asymp ­

tomatic for at least 6 hours may be safely discharged home.

Discharged patients should be instructed to return for

development of difficulty breathing, fever, or mental status

changes.

DROWNING INCIDENTS

SUGGESTED READING

Causey, AL, Nichter, MA. Drowning. In: Tintinalli JE, Stapczynski

JS, Ma OJ, Cline DM, Cydulka RK, Meckler GD. Tintinalli's

Emergency Medicine: A Comprehensive Study Guide. 7th ed.

New York, NY: McGraw-Hill, 201 1, pp. 137 1-1374.

Causey AL, Tilelli JA, Swanson ME. Predicting discharge in

uncomplicated near-drowning. Am J Emerg Med. 2000;1 8:9.

Layon AJ, Modell JH. Drowning: Update 2009. Anesthesiology.

2009;1 10:1390.

Papa L, Hoelle R, Idris A. Systematic review of definitions for

drowning incidents. Resuscitation. 2005;65:255.

Salomez F, Vincent JL. Drowning: A review of epidemiology,

pathophysiology, treatment and prevention. Resuscitation.

2004;63:26 1.

van Beeck EF, Branche CM, Szpilman D, Modell JH, Bierens JJ.

A new definition of drowning: Towards documentation and

prevention of a global public health problem. Bull World

Health Organ. 2005;83:853.

Envenomation

Patrick M. La n k, MD

Key Points

• In addition to any focused or antidotal therapy available, aggressive symptom-based supportive care is

important for all envenomations.

• Knowledge of local venomous species may be helpful,

although be aware that patients may have contact with

non local or exotic venomous animals.

INTRODUCTION

In 2010, there were more than 60,000 calls made to United

States Poison Centers related to bites and envenomations.

Although there are many venomous animal species in

North America, a majority of these calls involved insects

(including bees, wasps, hornets, and ants), arachnids

(including spiders and scorpions), and snakes. From information provided in the 20 10 Annual Report of the

American Association of Poison Control Centers' National

Poison Data System, there were a total of 5 fatalities related

to all bites or envenomations and approximately 2,500

instances of antivenin being given.

The clinical presentations of the various forms of

venom exposure vary greatly and are dependent on multiple factors including the species of the animal, the

amount of venom delivered, and potential baseline medi ­

cal problems in the envenomed patient. Patients presenting with an animal envenomation may therefore display a

variety of symptoms ranging from local reaction to a bite

or sting to generalized yet nonspecific effects (eg, vomiting, headache, hypertension) or toxin-specific findings

(eg, paralysis or coagulopathy) . This chapter focuses on

the presentation, evaluation, and treatment of 2 of the

most clinically relevant North American envenomations:

snakes and spiders.

• North American venomous bites are rarely unprovoked.

• Contact your local poison control center (1-800-222-1 222)

for assistance with diagnosing and managing all envenomations.

� Snakes

Venomous snakes found in North America are most easily

divided into their 2 families: Elapidae and Viperidae (subfamily Crotalinae). The majority of venomous snakebites

occurring yearly in North America are caused by snakes in

the Crotalinae subfamily, which includes rattlesnakes

(genus Crotalus), copperheads, and cottonmouths (genus

Agkistrodon). Less than 5o/o of venomous snakebites are

from the Elapidae family, which includes the coral snake.

Fewer still may be from bites by exotic, nonnative snakes

usually being kept as pets.

Venomous snakes found natively in North America are

generally nonpredatory to humans. Bites, therefore, take place

on provocation of the snake-either intentional or accidental.

These bites are typically located on extremities, but particu ­

larly troublesome cases have been reported in which venomous bites have involved the face, neck, or tongue. The vast

majority of venomous snakebites occur in young men, with

an appreciable association with alcohol intoxication. Children

are also at a higher risk for being bitten by a venomous snake.

There are a few characteristics that can help identify a

North American snake as being part of the Crotalinae subfamily. These snakes have vertical slit-like pupils, long

fangs, and a triangular head. This subfamily is also referred

to as "pit vipers" because they have heat-sensing pits

274

ENVENOMATION

Poisonous (pit vipers) Harmless

Nostri l

Figure 65-1. Differences between venomous pit vipers and nonvenomous

North American snakes.

located on their heads j ust behind the nostrils and in front

of the eyes (Figure 65- 1). Crotaline venom contains a combination of chemicals that cause primarily local tissue

damage and hematologic effects.

Elapidae native to North America are the coral snakes.

These snakes, found mostly in the Southeast United States

(particularly Florida and Texas), have a characteristic color

pattern that distinguishes them from the similar-appearing but

nonvenomous scarlet king or milk snake. People often remember this pattern difference by reciting the rhyme, "Red on yellow kills a fellow. Red on black, friend of Jack'' (Figure 65-2).

Elapid venom has a curare-like neurotoxic effect and is said to

be one of the most potent North American venoms. However,

multiple characteristics of the snake make clinically significant

bites from these snakes rare. They tend to reside in remote

unpopulated areas and even if confronted will attempt to flee

before biting. Unlike the crotalids, the elapids' fangs are short

and unlikely to penetrate thick clothing or shoes. After biting,