Chapter 128. Pneumococcal Infections (Part 4) pot

Pneumococcal Infections Part 4 Physical Findings Patients with pneumococcal pneumonia usually appear ill and have a grayish, anxious appearance that differs from that of persons with v

Chapter 128 Pneumococcal Infections

(Part 4)

Physical Findings

Patients with pneumococcal pneumonia usually appear ill and have a grayish, anxious appearance that differs from that of persons with viral or mycoplasmal pneumonia Temperature, pulse, and respiratory rate are typically elevated Elderly patients may have only a slight temperature elevation or may be afebrile Hypothermia may be documented instead of fever and is associated with increased morbidity and mortality Pleuritic chest pain may cause diminished respiratory excursion (splinting) on the affected side Dullness to percussion is noted in about half of cases, and vocal fremitus is increased over the area of consolidation Breath sounds may be bronchial or tubular, and crackles are heard

in most cases if enough air is being moved to generate them Flatness to percussion at the lung base, absent fremitus, and lack of the expected degree of diaphragmatic motion suggest the presence of pleural fluid, which raises the possibility of empyema The finding of a heart murmur—certainly if new—raises

concern about endocarditis, a rare but serious complication Hypoxia or the generalized response to pneumonia may cause the patient to be confused, but the appearance of confusion should also raise concern about meningitis Obtundation

or neck stiffness should lead to an immediate consideration of this complication

Radiographic Findings

In patients sick enough to be hospitalized, pneumococcal pneumonia is limited to one lung segment in fourth of cases and to one lobe in another one-fourth, with multilobar disease in the remaining one-half Air-space consolidation

is the predominant finding and is detected in 80% of cases (Fig 128-1) Air bronchogram (visualization of the air-filled bronchus against a background of alveolar consolidation) is evident in fewer than half of cases and is more common

in bacteremic than in nonbacteremic disease Rarely, pneumococcal pneumonia leads to a lung abscess Although some pleural fluid may actually be present in half of cases, ≤20% of patients have a sufficient volume of fluid to allow aspiration, and in only a minority of these patients is empyema documented

Figure 128-1

A retrocardiac infiltrate in a patient with pneumococcal pneumonia

Right-lower-lobe consolidation is apparent in posterior-anterior (left) and lateral

(right) views of the chest

General Laboratory Findings

Anemia (hemoglobin level, <10 g/dL) is documented in 25% of cases The peripheral-blood white blood cell (WBC) count exceeds 12,000/µL in the great majority of patients with pneumococcal pneumonia A low WBC count (<6000/µL) is found in 5–10% of persons hospitalized for pneumococcal pneumonia and is strongly associated with fatal disease The serum bilirubin level

is modestly elevated in one-third of cases; hypoxia, inflammatory changes in the liver, and breakdown of red blood cells in the lung are all thought to contribute to this increase A serum albumin level of <2.5 g/dL in 30% of cases may indicate predisposing malnutrition or may be the result of sepsis About 20% of patients have serum sodium concentrations of ≤130 meq/L, and another 20% have serum creatinine concentrations of ≥2 mg/dL Abnormalities of pleural fluid in empyema are reviewed in Chap 251

Differential Diagnosis

S pneumoniae is the most common cause of so-called community-acquired

pneumonia, but patients who present with this syndrome may actually have infection due to a broad array of microorganisms The extensive list includes (but

is not limited to) the following: H influenzae or Moraxella catarrhalis in persons

with little to predispose them other than chronic or acute inflammation of the

airways; Staphylococcus aureus, especially in persons who take glucocorticoids,

who have influenza, or who have major anatomic disruption of the airways;

Streptococcus pyogenes; Neisseria meningitidis; anaerobic and microaerophilic bacteria in persons who may have aspirated oropharyngeal contents; Legionella; Pasteurella multocida in dog or cat owners; gram-negative bacilli, especially in

persons who have severely damaged lungs and are taking glucocorticoids; viruses, especially influenza virus (in season), adenovirus, or respiratory syncytial virus;

Mycobacterium tuberculosis; fungi, including Pneumocystis (depending on epidemiologic factors and HIV infection status); Mycoplasma; Chlamydia pneumoniae, especially in older adults; and Chlamydia psittaci in bird owners

Many older men with lung cancer present with pneumonia, as do persons who have acute-onset inflammatory pulmonary conditions of uncertain etiology or those with pulmonary embolus and infarction The breadth of this list vividly illustrates the deficiency of empirical therapy for community-acquired pneumonia (Table 128-3) Many of these diseases require evaluation, and the increasing availability of specific therapy makes a precise etiologic diagnosis desirable

Table 128-3 Causes of a Pneumonia Syndrome Leading to Hospitalization of Adults in Houston, Texasa

Streptococcus pneumoniae

Moraxella catarrhalis

Haemophilus influenzae Staphylococcus aureus

Lung cancer Pulmonary infarction

Mycobacterium

tuberculosis

Klebsiella pneumoniae

Influenza (seasonal) Respiratory syncytial virus

flora

a

Pneumonia was defined as a syndrome consisting of fever, increased cough, sputum production, and an abnormal pulmonary shadow on chest x-ray