Most snakebites that occur are due to nonvenomous snakes.

However, about 7000–8000 individuals in the United States are bitten by venomous snakes each year, and of these, 5 will die (www.cdc.gov).

In the developing countries with temperate and tropical climates, snakebites are a more serious problem because access to healthcare resources may be quite sparse, and it is estimated at 20,000–94,000 individuals die worldwide from snakebites yearly.

Venomous snakes belong to the families Viperidae (pit vipers including rattlesnakes, copperheads, and cottonmouth water moccasins), Elapidae (including cobras and coral snakes), Lamprophiidae (asps), and Colubridae, which are largely nonvenomous but have a few toxic species. Most snakes have venom glands situated below and behind the eyes that are connected by ducts to hollow maxillary fangs. The fangs are retractable in most pit vipers and brought into an upright position for striking. It is notable when evaluating a snake bite to know that about 20% of pit viper bites and higher percentages of other snakebites bites contain no venom.

Significant envenomation occurs in only about 50% of all snakebites. Snake venoms are complex mixtures of enzymes, glycoproteins, and low-molecular-weight polypeptides, among other constituents, that lead to tissue hemorrhage, vascular leak, and proteolysis with tissue necrolysis. Some snake venoms have myocardial depressant factors and neurotoxins as well. The time from the bite to symptom onset is variable and depends on the species of snake, amount of envenomation, and site of the bite. Progressive local pain, swelling, and ecchymosis are common with development of hemorrhagic or serum-filled bullae. Systemic findings are quite variable and may include tachycardia or bradycardia, hypotension, weakness, coagulopathy, renal dysfunction, and neurologic dysfunction. If a patient has suffered a venomous snakebite, the most important aspect of prehospital care is supportive care with rapid transport to a medical facility where antivenom therapy is available. It is notable that most of the first-aid measures recommended in the past are of little benefit and may actually worsen local tissue damage.

Supportive Care

For supportive care, a splint may be applied to decrease pain and lessen bleeding. If possible, the injured limb should be elevated to the level of the heart. Attempting to capture the offending snake alive or dead is not recommended and could only lead to more injury in others.

Digital photographs taken from a safe distance away will suffice to allow identification of the snake. There is no role for incising or applying suction to the wound. This will not allow the venom to be removed and may introduce additional bacterial contamination. Applying a tight tourniquet also does not limit spread of venom and may endanger the affected limb by limiting blood flow. The only role for pressure-immobilization is in Elapid venoms (cobra), which are neurotoxic. This technique requires specific training to effectively apply to an entire limb and to a precise pressure. After application, the victim must be carried from the field and remain immobile in order to prevent spread of the neurotoxin. Upon arrival at the hospital, victims of snakebite should be carefully monitored for signs of significant envenomation that would require antivenom therapy. The patient should be monitored on telemetry with frequent vital signs. The area of snakebite should be cleaned and clearly marked. Limb circumference should be measured every 15 minutes. The extremity should remain at the level of the heart. Volume resuscitation should ensue, and large-bore IV access should be maintained. Indications for the use of antivenom therapy include significant local progression including soft tissue swelling that crosses a joint or involves more than half of the bitten limb. In addition, any evidence of systemic involvement should prompt the use of antivenom therapy.

Signs of systemic involvement could include hypotension, altered mental status, coagulopathy, renal dysfunction, rhabdomyolysis, hepatic dysfunction, or neurologic dysfunction. It is important to know the type of snake when administering antivenom therapy because it is specific to the type of snake. Prompt and serious allergy reaction can occur including anaphylaxis. Use of IV antihistamines is typical as a pretreatment. Posttreatment serum sickness reactions may occur.

 

 

 

 

 

 

 

 

 

 

 

Most people with pyelonephritis do not have complications if appropriately treated with bacteria-fighting medications called antibiotics.

In rare cases, pyelonephritis may cause permanent kidney scars, which can lead to chronic kidney disease, high blood pressure, and kidney failure. These problems usually occur in people with a structural problem in the urinary tract, kidney disease from other causes, or repeated episodes of pyelonephritis.

Infection in the kidneys may spread to the bloodstream—a serious condition called sepsis—though this is also uncommon.

 

 

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A 38-year-old man was hiking in a national forest near Tallahassee, Florida, when he was bitten on his lower right leg by a snake that his hiking companion identified as a rattlesnake. The man was wearing shorts and hiking boots. There are two clear puncture wounds that are oozing blood just above the sock line of his right boot, and the man is beginning to complain of increasing pain in the right leg. The man and his companion are about 15 minutes away from the trailhead and do not have a cell phone. What should be done immediately in the care of this patient?

A
Apply a splint if available to support the limb and decrease pain and seek immediate medical care

B
Apply a tourniquet superior to the bite to limit circulation of the venom

C
Incise or apply suction to the site of the bite immediately to attempt to remove injected venom

D
When possible, elevate the limb to heart level

E
A and D only

F
All of the above

 

Answer

Next Question
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The correct answer is E. You answered A.

Explanation:
The answer is E. (Chap. 474) Most snakebites that occur are due to nonvenomous snakes. However, about 7000–8000 individuals in the United States are bitten by venomous snakes each year, and of these, 5 will die (www.cdc.gov). In the developing countries with temperate and tropical climates, snakebites are a more serious problem because access to healthcare resources may be quite sparse, and it is estimated at 20,000–94,000 individuals die worldwide from snakebites yearly. Venomous snakes belong to the families Viperidae (pit vipers including rattlesnakes, copperheads, and cottonmouth water moccasins), Elapidae (including cobras and coral snakes), Lamprophiidae (asps), and Colubridae, which are largely nonvenomous but have a few toxic species. Most snakes have venom glands situated below and behind the eyes that are connected by ducts to hollow maxillary fangs. The fangs are retractable in most pit vipers and brought into an upright position for striking. It is notable when evaluating a snake bite to know that about 20% of pit viper bites and higher percentages of other snakebites bites contain no venom. Significant envenomation occurs in only about 50% of all snakebites. Snake venoms are complex mixtures of enzymes, glycoproteins, and low-molecular-weight polypeptides, among other constituents, that lead to tissue hemorrhage, vascular leak, and proteolysis with tissue necrolysis. Some snake venoms have myocardial depressant factors and neurotoxins as well. The time from the bite to symptom onset is variable and depends on the species of snake, amount of envenomation, and site of the bite. Progressive local pain, swelling, and ecchymosis are common with development of hemorrhagic or serum-filled bullae. Systemic findings are quite variable and may include tachycardia or bradycardia, hypotension, weakness, coagulopathy, renal dysfunction, and neurologic dysfunction. If a patient has suffered a venomous snakebite, the most important aspect of prehospital care is supportive care with rapid transport to a medical facility where antivenom therapy is available. It is notable that most of the first-aid measures recommended in the past are of little benefit and may actually worsen local tissue damage. For supportive care, a splint may be applied to decrease pain and lessen bleeding. If possible, the injured limb should be elevated to the level of the heart. Attempting to capture the offending snake alive or dead is not recommended and could only lead to more injury in others. Digital photographs taken from a safe distance away will suffice to allow identification of the snake. There is no role for incising or applying suction to the wound. This will not allow the venom to be removed and may introduce additional bacterial contamination. Applying a tight tourniquet also does not limit spread of venom and may endanger the affected limb by limiting blood flow. The only role for pressure-immobilization is in Elapid venoms (cobra), which are neurotoxic. This technique requires specific training to effectively apply to an entire limb and to a precise pressure. After application, the victim must be carried from the field and remain immobile in order to prevent spread of the neurotoxin. Upon arrival at the hospital, victims of snakebite should be carefully monitored for signs of significant envenomation that would require antivenom therapy. The patient should be monitored on telemetry with frequent vital signs. The area of snakebite should be cleaned and clearly marked. Limb circumference should be measured every 15 minutes. The extremity should remain at the level of the heart. Volume resuscitation should ensue, and large-bore IV access should be maintained. Indications for the use of antivenom therapy include significant local progression including soft tissue swelling that crosses a joint or involves more than half of the bitten limb. In addition, any evidence of systemic involvement should prompt the use of antivenom therapy. Signs of systemic involvement could include hypotension, altered mental status, coagulopathy, renal dysfunction, rhabdomyolysis, hepatic dysfunction, or neurologic dysfunction. It is important to know the type of snake when administering antivenom therapy because it is specific to the type of snake. Prompt and serious allergy reaction can occur including anaphylaxis. Use of IV antihistamines is typical as a pretreatment. Posttreatment serum sickness reactions may occur.

A 75-year-old triathlete complains of gradually worsening vision over the past year. It seems to be involving near and far vision. The patient has never required corrective lenses and has no significant medical history other than diet-controlled hypertension. He takes no regular medications. Physical examination is normal except for bilateral visual acuity of 20/100. There are no focal visual field defects and no redness of the eyes or eyelids. Which of the following is the most likely diagnosis?

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The correct answer is A. You answered A.

Age-related macular degeneration is a major cause of painless, gradual bilateral central visual loss. It occurs as nonexudative (dry) or exudative (wet) forms. Recent genetic data have shown an association with the alternative complement pathway gene for complement factor H. The mechanism link for that association is unknown. The nonexudative form is associated with retinal drusen that leads to retinal atrophy. Treatment with vitamin C, vitamin E, beta-carotene, and zinc may retard the visual loss. Exudative macular degeneration, which is less common, is caused by neovascular proliferation and leakage of choroidal blood vessels. Acute visual loss may occur because of bleeding. Exudative macular degeneration may be treated with intraocular injection of a vascular endothelial growth factor antagonist (bevacizumab or ranibizumab). Blepharitis is inflammation of the eyelids usually related to acne rosacea, seborrheic dermatitis, or staphylococcal infection. Diabetic retinopathy, now a leading cause of blindness in the United States, causes gradual bilateral visual loss in patients with long-standing diabetes. Retinal detachment is usually unilateral and causes visual loss and an afferent pupillary defect.

 

Mr. Jenson is a 40-year-old man with a congenital bicuspid aortic valve who you have been seeing for more than a decade. You obtain an echocardiogram every other year to follow the progression of his disease knowing that bicuspid valves often develop stenosis or regurgitation requiring replacement in middle age. Given his specific congenital abnormality, what other anatomic structure is important to follow on his biannual echocardiograms?

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The correct answer is A. You answered A.

The answer is A. (Chap. 282) Bicuspid aortic valve is among the most common of congenital heart cardiac abnormalities. Valvular function is often normal in early life and thus may escape detection. Due to abnormal flow dynamics through the bicuspid aortic valve, the valve leaflets can become rigid and fibrosed, leading to either stenosis or regurgitation. However, pathology in patients with bicuspid aortic valve is not limited to the valve alone. The ascending aorta is often dilated, misnamed “poststenotic” dilatation; this is due to histologic abnormalities of the aortic media and may result in aortic dissection. It is important to screen specifically for aortopathy because dissection is a common cause of sudden death in these patients.

 


 

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