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Emergency Medicine News:
doi: 10.1097/01.EEM.0000279134.85535.0c
Learning to Live with the LLSA

Articles from the 2005 LLSA Reading List: Febrile Seizures; West Nile Virus; the Ottawa Knee Rule

Mullin, Daniel K. MD

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Author Information

Author Credentials and Financial Disclosure: Daniel K. Mullin, MD, is a Clinical Instructor of Emergency Medicine at Drexel University College of Medicine in Philadelphia.

Dr. Mullin has disclosed that he has no financial interests in or relationships with any commercial companies pertaining to this educational activity.

Release Date: June 2007

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Abstract

After reading this article, the physician should be able to:

1. Describe the evaluation and management of children with febrile seizures and be able to advise parents about simple febrile seizures to relieve some of their fears.

2. Discuss the presentation, diagnosis, clinical course, neurologic complications, and treatment of patients infected with West Nile Virus.

3. Summarize the Ottawa Knee Rule and its utility in children.

Evaluation and Management of Febrile Seizures in the Out-of-Hospital and Emergency Department Settings. Warden CR, et al. Ann Emerg Med 2003;41:215

Febrile seizures are the most common seizures seen in the pediatric population. In fact two percent to four percent of children worldwide will have a febrile seizure at some point in time. A febrile seizure is defined as any seizure occurring in an infant or young child (6 months to 5 years) in conjunction with a fever (temperature >38ºC [100.4ºF]) or a history of recent fever and without evidence of a previous afebrile seizure or an underlying cause. It can be classified as either simple or complex; the importance of this classification will be discussed later.

There is a history of febrile seizures in immediate family members in 25 percent to 40 percent of cases. Offspring of a parent with a history of febrile seizures have 4.4 times the risk of the general population. Once a child has suffered a febrile seizure, he is fairly likely to have another one with subsequent febrile illnesses. The use of medicines, such as acetaminophen or ibuprofen for fevers, has not been shown to prevent febrile seizures. Risk factors for recurrent febrile seizures include children under 12 months with a first-time febrile seizure, patients with a lower temperature on presentation of their first seizure (<40ºC), patients with a shorter duration of fever before the seizure (<24 hours), and those with complex febrile seizures.

In the general population, the risk of developing epilepsy by age 7 years is approximately one percent. Children having had one simple febrile seizure have only a slightly higher risk of developing epilepsy. Children under 12 months with their first simple febrile seizure have a 2.4 percent risk of developing epilepsy. In contrast, the risk of developing epilepsy increases to 30 to 50 times that of the general population in patients with one or more complex febrile seizures.

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Viral infections are frequently associated with febrile seizures, including but not limited to human herpes viruses 6 and 7, herpes simplex virus, and influenza A and B. Post-vaccination fevers are another important cause of febrile seizures with a significantly increased risk on the day of the diphtheria/tetanus toxoid/whole-cell pertussis vaccination, and eight to 14 days after the measles/mumps/rubella vaccination.

The emergency department evaluation and management of febrile seizures should always begin with assessing the patient's airway patency, ventilation and oxygenation adequacy, and circulatory status, and then dealing with these appropriately. Because febrile seizures are usually short by their very nature (most less than five minutes), the child will rarely be seizing on arrival, and antiepileptic medication is rarely needed in the acute setting. Initial airway and ventilation maneuvers will usually involve only noninvasive techniques because it is likely that the patient's airway status will improve rapidly as the postictal state resolves or medications are given. Routine blood work is rarely necessary, with the exception of a serum glucose test.

After initial evaluation and stabilization, the physician should use the history and physical examination to identify a recognizable viral or bacterial illness that may serve as the focus of the fever. The physician also should search for signs and symptoms of a serious bacterial illness such as meningitis and other potential causes of seizure such as trauma or toxic exposure.

Fortunately for patients, parents, and emergency physicians, the rates of serious bacterial infections in patients with febrile seizures are equivalent to those in age-matched febrile control patients without seizures. Additionally, febrile seizures rarely cause any permanent neurologic sequelae. That said, one of the critical decisions that must be made in the evaluation of a child who has had a febrile seizure is whether to perform a lumbar puncture to evaluate for meningitis. There is no standard of care for who needs a lumbar puncture, although Warden et al, based on expert opinion and several studies, created a decision criteria for which children under 18 months should be “strongly considered” to undergo a lumbar puncture to rule out meningitis. They stated that children over 18 months have more reliable signs or symptoms of CNS infection (altered mental status, meningismus, or both), and lumbar punctures can be deferred if these are absent.

Possibly the most important action an emergency physician can take is to educate the parents and relieve them of some of their anxiety. A febrile seizure is a harrowing experience for any parent because they frequently assume the very worst, that their child has meningitis or brain damage, and will suffer from epilepsy for the rest of his life. After ruling out any serious causes of the febrile seizure, the emergency physician should take time prior to discharge to sit with the parents or guardians to teach and to answer any questions.

West Nile Virus. Petersen LR, et al. JAMA 2003;290(4):524

West Nile virus is a single-stranded RNA virus of the family Flaviviridae. The virus is maintained in a bird-mosquito-bird cycle. In temperate regions, the cycle begins in the spring when mosquitoes first emerge and lasts until early fall when female mosquitoes enter diapause and infrequently bite. Mosquitoes from the genus Culex are the principal maintenance and amplifying vectors.

The virus gets its name from where it was first isolated, in a resident of the West Nile district of Uganda in 1937. From 1937 to the early 1990s, human outbreaks were mild and reported mostly in Africa and Israel. From 1999 to 2001, cases of human infections with West Nile virus in the United States were reported infrequently (62 cases in 1999, 21 in 2000, and 66 in 2001), and were isolated to the East Coast. By 2002 there were more than 4,000 reported cases distributed throughout a majority of the United States.

Most individuals infected with West Nile virus remain asymptomatic, but the severity of clinical illness increases with age. When clinical illness occurs, the incubation period generally ranges from two to 14 days. West Nile fever is a mild illness, typically lasting three to six days. Symptoms are similar to many viral infections, and include malaise, anorexia, nausea, vomiting, headache, myalgia, and rash. Approximately 20 percent of infected individuals develop West Nile fever.

Fewer than one percent of individuals infected with West Nile virus develop severe neurologic disease (encephalitis, meningitis, or acute flaccid paralysis). Acute flaccid paralysis is a devastating complication of West Nile virus where weakness is asymmetrical, affects the upper and lower limbs, and can occur without overt meningoencephalitis. It is generally characterized by hyporeflexia or areflexia, acute bowel or bladder dysfunction, with an absence of pain or sensory abnormalities. The pathophysiology is different from Guillain-Barré syndrome in that acute flaccid paralysis is caused by the destruction of the anterior spinal horn cells, resulting in a poliomyelitis-like syndrome.

Case-fatality rates range from four percent to 18 percent among hospitalized patients. During the outbreak in the United States in 2002, patients with meningoencephalitis had a case-fatality rate of nine percent. The diagnosis of West Nile virus infections can usually be made by the detection of IgM antibodies in serum or CSF samples. The IgM antibody may persist for more than 500 days in the serum, so if clinicians fail to think about West Nile virus infection initially, they do have time to make the appropriate diagnosis later. If a lumbar puncture is performed, the CSF of patients with meningoencephalitis generally shows pleocytosis, usually with a predominance of lymphocytes and elevated protein levels. Computed tomography of the brain is generally read as normal.

Treatment of West Nile virus infection is supportive. Nothing has been proven or even suggested to help treat West Nile virus encephalitis or the acute flaccid paralysis. Prevention is the key through avoiding mosquito exposure and instituting community mosquito control programs.

Validation of the Ottawa Knee Rule in Children: A Multicenter Study. Bulloch B, et al. Ann Emerg Med 2003;42:48

This was a prospective, multicenter validation study of the Ottawa Knee Rule in children 2 to 16 who presented to the ED with a knee injury sustained in the preceding seven days. A positive outcome was defined as any fracture.

The original clinical decision aid, called the Ottawa Knee Rule, was described and studied by Stiell et al. (Ann Emerg Med 1995;26:405 and JAMA 1996;275:611.) The original studies were all done in adults, and the rule was found to be 100% sensitive. Additionally, a systemic review of 11 studies to determine the accuracy of the Ottawa Knee Rule to rule out knee fractures found that the pooled sensitivity was 98.5% and the pooled specificity was 48.6%. (Ann Inter Med 2004;140:121.)

This particular study was done at five urban academic pediatric emergency departments in Canada from 1999 to 2002; 750 children were enrolled. Of these, only 45 children were between 2 and 5, and 70 children were diagnosed with fractures. The Ottawa Knee Rule was found to be 100% sensitive and 42.8% specific in children, with excellent interobserver reliability in the application of the rules. By using this clinical decision aid, there would have been an absolute reduction in ordering x-rays of 31.2 percent. Because the average age of children in this study was 11.8 years and only a small number were under 5, the rule should be considered acceptable for anyone over age 5.

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Ottawa Knee Rule

A knee x-ray series is only required for knee injury patients with any of these findings.

* Age 5 or older.

* Isolated tenderness of the patella.

* Tenderness at the head of the fibula.

* Inability to flex to 90 degrees.

* Inability to bear weight both immediately and in the emergency department (four steps).

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STRONGLY CONSIDER LUMBAR PUNCTURE IF PATIENT IS UNDER 18 MONTHS AND

* Has a history of irritability, decreased feeding, or lethargy.

* Has any physical signs of meningitis, such as bulging fontanelle, Kernig or Brudzinski signs, photophobia, or severe headache.

* Has any complex features.

* Has any slow postictal clearing of mentation.

* Was pretreated with antibiotics.

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About the LLSA

As part of its continuous certification program, the American Board of Emergency Medicine has developed the Lifelong Learning and Self-Assessment (LLSA) program to promote continuous education of diplomates. Each year, beginning in 2004, 16 to 20 articles are chosen based on the Emergency Medicine Model. A list of these articles can be found on the ABEM web site, www.abem.org.

ABEM is not authorized to confer CME credit for the successful completion of the LLSA test, but it has no objection to physicians participating in such activities. EMN's CME activity, Learning to Live with the LLSA, is not affiliated with ABEM's LLSA program, and reading this article and completing the quiz does not count toward ABEM certification. Rather, participants may earn 1 CME credit from the Lippincott Continuing Medical Education Institute, Inc., for each completed EMN quiz.

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© 2007 Lippincott Williams & Wilkins, Inc.

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