Infectious Diseases

Chapter 64 Infectious Diseases



William V. Raszka



INFECTIOUS DISEASE EMERGENCIES



ETIOLOGY



What Is an Infectious Disease Emergency?


An infectious disease emergency can cause rapid loss of organ function or life unless intervention is immediate. Overwhelming sepsis is the prototype infectious disease emergency. In particular, meningococcemia places a patient at high risk for organ dysfunction and death. Occasionally, even mild disease such as viral laryngotracheobronchitis or croup may lead to an emergency if the airway becomes obstructed. In many parts of the world, severe watery diarrhea causes significant morbidity and mortality. Hence, every single patient must be examined with the idea that he or she might have an infectious disease emergency. Chapter 31 describes a general approach to emergencies in children, and Chapter 59 discusses specific emergent presentations.



EVALUATION



When Should I Suspect an Infectious Disease Emergency?


Lethargy, marked irritability, and difficulty breathing are indications that a child is severely ill or “toxic.” An elevated body temperature in itself is rarely a threat to long-term health. Fever is merely a sign that should be interpreted along with the heart rate, respiratory rate, and blood pressure. Lethargy or irritability implies altered central nervous system perfusion. Stridor, tachypnea, and increased work of breathing suggest serious airway problems.



TREATMENT



How Should I Treat Infectious Emergencies?


Treatment begins with the identification of the emergency situation (see Chapter 31). Hence, a high index of suspicion and a careful assessment of children whose clinical presentation suggests the possibility of an infectious emergency are mandatory if successful treatment is to be started. Treatment depends entirely on the specific infection diagnosed.



SPECIFIC INFECTIOUS DISEASE EMERGENCIES



SEPSIS



ETIOLOGY



What Is Sepsis?


Sepsis is the systemic reaction to bacteria (or other organisms). The terminology of sepsis has changed in the last decade and now reflects a progression of disease severity. The initial insult is a localized or systemic infection that provokes a systemic inflammatory response syndrome (SIRS), characterized by hyperthermia or hypothermia, tachycardia, tachypnea, and changes in the circulating white blood cell count. Once the inflammatory response is activated, the process can proceed independently of the infection. SIRS with hypotension is called sepsis. Severe sepsis is defined as sepsis with organ dysfunction, whereas septic shock is defined as sepsis with persistent hypotension despite adequate fluid resuscitation.



What Causes Sepsis?


Almost any bacterial infection can lead to sepsis, but Streptococcus pneumoniae and Neisseria meningitidis are the most common inciting organisms outside the newborn period. Both are encapsulated organisms, making them more difficult for the immune system to clear. The mortality rate of sepsis may be as high as 50% but is highly variable and dependent on the underlying condition of the patient and the initial site of infection.



EVALUATION



How Does Sepsis Present at Different Ages?


Infants and young children often present with fever, poor feeding, tachypnea, and irritability or lethargy. Adolescents may present with fever, shaking chills, confusion, and tachypnea. Additional findings in both groups include tachycardia, delayed capillary refill, hypotension or widened pulse pressure, and petechiae and purpura. The younger the infant, the more nonspecific may be the findings. Hence, particularly in children younger than 3 months, almost any child with fever and irritability is evaluated for possible sepsis (see Chapter 33).



What Laboratory Tests Help in the Diagnosis of Sepsis?


Laboratory findings include elevated prothrombin and partial thromboplastin times, reduced fibrinogen levels, neutropenia or neutrophilia, and toxic granulation of the neutrophils. Culture of blood, cerebrospinal fluid (CSF), urine, and any specific lesions often identify the infecting organism.



TREATMENT



How Is Sepsis Managed?


Management of septic patients requires immediate, aggressive fluid resuscitation, intensive care support, and prompt empirical antimicrobial therapy with a third-generation cephalosporin such as ceftriaxone with or without vancomycin. Specific antimicrobial therapy is dependent on identification of the offending agent.



Can Sepsis Be Prevented?


National immunization campaigns have made Haemophilus influenzae type b, once a common cause of childhood sepsis, exceedingly rare. The current 7-valent conjugate-pneumococcal vaccine given to infants has reduced the incidence of invasive S. pneumoniae disease in all populations. The conjugate-meningococcal vaccine, which has been highly effective in preventing meningococcal disease in English children, was approved in 2005 for universal administration to American preteens and adolescents. Close contacts of patients with meningococcal disease should be offered prophylactic treatment with rifampin, ciprofloxacin, or ceftriaxone to minimize their risk of invasive disease.



MENINGITIS



ETIOLOGY



What Causes Meningitis?


Meningitis is inflammation of the fluid and the membranes that surround the central nervous system and is caused by many different organisms. Bacterial infections are less common than viral, but can lead to serious acute and chronic complications. The most common organisms that cause bacterial meningitis outside the newborn period are S. pneumoniae and N. meningitidis. Enteroviruses are the most common viruses that cause meningitis, most often in late summer and early fall epidemics. Although children can appear quite ill, they recover very quickly and generally suffer no permanent sequelae.



EVALUATION



How Does Meningitis Present?


Younger patients with meningitis may present with fever, irritability or lethargy, poor feeding, vomiting, and a bulging fontanelle. Signs of meningismus, such as nuchal rigidity and a positive Kernig’s or Brudzinski’s sign, may be absent in children younger than 18 months. Older children may present with fever, decreased level of consciousness, headache, vomiting, nuchal rigidity, and positive tests for meningismus. Seizures may occur in 20% to 30% of patients.



What Tests Help with the Diagnosis?


The diagnosis of meningitis is confirmed by analysis of CSF obtained by lumbar puncture. More than 95% of patients with meningitis will have an elevated number of leukocytes in the CSF at the time of presentation. Distinguishing viral from bacterial meningitis may be difficult because of a considerable overlap in initial CSF findings. Generally, patients with bacterial disease have a low glucose and high protein level in the CSF and more than 50% of the leukocytes are polymorphonucleocytes. Blood and CSF cultures will confirm the etiology of the meningitis. Untreated patients who have signs and symptoms of meningitis and CSF pleocytosis but grow no microorganisms from CSF culture most often have viral meningitis. Some institutions will use polymerase chain reaction (PCR) technology on CSF specimens to rapidly confirm the diagnosis of enteroviral meningitis. Viral culture can also confirm the diagnosis.



TREATMENT



How Is Meningitis Treated?


Initial, empirical antimicrobial therapy is directed at the usual causative organisms, including penicillin-resistant S. pneumoniae. Empirical treatment of suspected pyogenic meningitis includes ceftriaxone (or cefotaxime) and vancomycin in children older than 28 days unless meningococcal disease is confirmed. Both antibiotics are continued until the microbiology laboratory verifies that the pneumococcal isolate is susceptible to penicillin or ceftriaxone, at which time vancomycin can be discontinued. Concomitant use of corticosteroids is controversial. Corticosteroid administration before systemic antibiotics may decrease the likelihood of sensorineural hearing loss. Serum sodium and intravascular volume status need to be monitored: patients with pyogenic meningitis are at risk for developing the syndrome of inappropriate antidiuretic hormone secretion, and they may also be volume depleted because of poor feeding or emesis.



What Is the Prognosis for a Patient with Meningitis?


Prognosis is dependent on the age of the child, the infecting organism, the duration of illness before initiation of appropriate care, and the sophistication of the medical support team. Pyogenic meningitis results in the death of 1% to 8% of patients. Neurologic complications such as developmental delay, seizures, and hearing loss may occur in up to one-third of patients. Of these, hearing loss is the most common complication and occurs in approximately 30% of patients with S. pneumoniae meningitis and in 5% to 10% of patients following N. meningitidis meningitis.



ENCEPHALITIS



ETIOLOGY



What Causes Encephalitis?


Encephalitis is inflammation of the cerebellar or cerebral tissue rather than just the membranes or fluid surrounding them, as occurs with meningitis. The agents that cause encephalitis are usually viral. The most important of these is herpes simplex virus (HSV). Many viruses may cause mild to moderate meningoencephalitis, but HSV is associated with severe disease that can potentially be treated.



EVALUATION



What Findings Should Make Me Suspect Encephalitis?


Patients with encephalitis commonly present with altered mental status. Patients of all ages may have fever, irritability, lethargy, myalgias, nausea, vomiting, and seizures. Some neonates may have typical HSV cutaneous vesicular eruptions. In older children, headache and depressed levels of consciousness are common symptoms.



What Are the Laboratory Tests to Order?


The diagnosis of encephalitis is usually confirmed by analysis of CSF obtained by lumbar puncture. Most patients will demonstrate a lymphocytic CSF pleocytosis and mild elevations of CSF protein. In HSV encephalitis, RBCs may become more prominent in the CSF as the disease progresses. PCR identifies the virus in the CSF of more than 90% of patients with HSV encephalitis. Viral cultures, on the other hand, identify HSV in about 50% of neonates but only 5% of older children. In HSV encephalitis, specific temporal lobe findings may be seen on computed tomography (CT) scan, magnetic resonance imaging (MRI), and electroencephalogram (EEG).



TREATMENT



Can Encephalitis Be Treated?


HSV is the only cause of encephalitis that has a specific treatment: High-dose intravenous acyclovir plus supportive care such as airway management, seizure control, and circulatory support. Although acyclovir has dramatically decreased the mortality associated with HSV encephalitis, even with therapy, many patients suffer significant neurologic sequelae.



NONEMERGENT INFECTIOUS DISEASES



SINUSITIS



ETIOLOGY



What Causes Sinusitis?


The pathophysiology, bacteriology, and treatment of acute bacterial sinusitis are similar to those of acute otitis media. Obstruction of the ostiomeatal complex or impairment of sinus mucociliary function predisposes to sinusitis. Viral illness, allergies, and exposure to smoke are frequent precipitating events. The natural history of sinusitis is not well known. Viral rhinosinusitis always accompanies viral rhinitis, and some patients develop acute bacterial infection. Some may go on to develop chronic bacterial sinusitis. The most common organisms isolated from patients with acute bacterial sinusitis include S. pneumoniae, nontypable H. influenzae, and Moraxella catarrhalis. In suspected chronic sinusitis, Staphylococcus aureus and anaerobes may play a role.



EVALUATION



How Do I Determine If a Child Has Sinusitis?


Distinguishing children with viral rhinosinusitis from those with acute bacterial sinusitis is difficult. “Classic” features of acute bacterial sinusitis, such as high fever, facial pain and tenderness, and facial edema, particularly eye swelling, are found in adults and may occur in adolescents, but they are infrequently identified in younger children. Sinusitis is usually suspected in young children because of persistent (> 10 days) upper respiratory tract symptoms such as rhinorrhea and cough. The cough is present both night and day but is often worse in the evening while the patient is supine. The diagnosis is largely clinical. Sinus x-rays and CT scans do not reliably distinguish between viral and bacterial disease.



TREATMENT



Should Sinusitis Be Treated with Antibiotics?


The treatment of sinusitis is controversial. The few randomized trials of antibiotic treatment in pediatric patients have produced conflicting results. All agree that patients with fever, facial pain and tenderness, or eye swelling should be treated with antibiotics. Patients with persistent nasal discharge and cough may also benefit from antimicrobial therapy. Antibiotic treatment should be directed at the most common organisms, including penicillin-resistant S. pneumoniae. Other measures that may help include nasal irrigation with normal saline, warm mist, and, in severe cases, nasal sympathomimetics. Nasal sympathomimetics such as oxymetazoline must be used very judiciously because use for more than 3 days is associated with significant complications.



EYE INFECTIONS



ETIOLOGY



What Causes Red Eyes?


Conjunctivitis is inflammation of the membrane that covers the eye and the tarsal lid surface. Allergies, foreign bodies, anatomic obstruction, systemic reactions, viruses, and bacteria all can cause conjunctivitis. Many viruses can cause conjunctivitis, including enteroviruses and adenovirus. Pharyngoconjunctival fever is an especially contagious form of adenoviral infection. The most common causes of bacterial conjunctivitis outside of the neonatal age groups are gram-positive cocci such as S. aureus, streptococci, and nontypable H. influenzae. Infants younger than 2 months may develop Chlamydia trachomatis conjunctivitis acquired from passage through an infected maternal cervix. Scleral injection without infection is a characteristic finding in Kawasaki disease. Distinguishing among the many causes of conjunctivitis is difficult. Eye discharge without conjunctival erythema is common in infants who have lacrimal duct obstruction and does not necessarily indicate the presence of conjunctivitis.



EVALUATION



How Do I Identify the Cause of Conjunctivitis?


Conjunctivitis should be diagnosed only when there is inflammation of the conjunctival tissues. An eye discharge without inflammation is not conjunctivitis. Eye inflammation exists on a spectrum ranging from mild redness with prominent conjunctival vessels, usually termed injection, to severe, prominent, confluent erythema, usually labeled with the term inflammation. Children with allergic conjunctivitis usually complain of pruritus. Examination of the tarsal conjunctivae may reveal cobblestoning. Children with a foreign body in the eye usually note the sudden onset of local irritation. Patients with systemic reactions or a systemic disease such as measles or Kawasaki disease have other symptoms and signs, including fever.

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Jun 19, 2016 | Posted by in PEDIATRICS | Comments Off on Infectious Diseases

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