Respiratory syncytial infection

Risk factors for severe disease

The development of life-threatening conditions during Orthopneumovirus infection is often related to the patient's specific immune response. The key factors contributing to the worsening of the infectious process are:

• Lack of specific immunity against the currently circulating epidemic strains of the pathogen. This is especially relevant for travelers experiencing a change in climate zone.
• Decreased general resistance of the body, which naturally occurs during the reacclimatization process.

Diagnosis of acute respiratory failure

To accurately assess the severity of ARF, a comprehensive examination is required. It includes chest radiography, acid-base balance (ABB) analysis, blood gas analysis ($PaO_2$, $PaCO_2$, $SpO_2$), as well as monitoring of electrolytes and hemostatic parameters.

In hypoxemic-type ARF, the laboratory picture demonstrates characteristic dynamics:

1. Initially, a decrease in $PaO_2$ and $PaCO_2$ levels is recorded.
2. Subsequently, there is a steady increase in hypoxemia combined with hypercapnia.
3. Progression of metabolic acidosis is documented.

Radiographs are expected to reveal specific signs: multiple fluffy shadows («snowstorm» sign), symmetric confluent opacities in the lung tissue, and pleural effusion.

Intensive care in the ICU

Patients with severe forms of the disease are admitted to the intensive care unit (ICU). Treatment strategy is based on six main areas:

1. Combating hypoxemia. Includes lowering body temperature (<37.5°C), sedation, oxygen inhalation (or mechanical ventilation if ineffective), and nebulizer therapy, which is preferably combined with non-invasive ventilation. The nebulizer uses warm saline, acetylcysteine, surfactant-BL, glucocorticosteroids (budesonide 0.5–1.0 mg), and sympathomimetics (salbutamol 2.5–5 mg). This improves mucociliary clearance and prevents alveolar collapse.
2. Hemostasis correction. Performed strictly according to indications using heparin, antiplatelet agents, and fresh frozen plasma.
3. Hormone therapy. Parenteral administration of prednisolone at a dosage of up to 500 mg/day is used to suppress lipid peroxidation and block the release of inflammatory mediators.
4. Restoration of water-electrolyte balance.
5. Immunomodulation. Administration of hyperimmune plasma and donor hyperimmune gamma-globulin.
6. Prevention of bacterial complications. Consists of intravenous administration of broad-spectrum antibiotics. Empirical therapy targets Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae.

Antibiotic therapy for secondary pneumonia

In the event of bacterial pneumonia developing against the background of a viral infection, drugs of choice are 3rd or 4th generation cephalosporins, carbapenems, and 4th generation fluoroquinolones.

If the clinical picture indicates a high probability of staphylococcal colonization, reserve drugs are included in the treatment regimen. In such situations, vancomycin (Vancomycin) or linezolid (Linezolid) become the drugs of choice.

Differential diagnosis of acute infections

Upon admission of patients with fever and respiratory symptoms, it is important to rule out other severe infections. In practice, the following clinical scenarios are encountered:

• Acute zoonoses: may present with high fever (up to 39.9°C), severe calf muscle pain, facial puffiness, scleral injection, hepatosplenomegaly, and signs of renal failure (oliguria, dark urine). A history of swimming in rural water bodies is often present.
• Adenovirus infection / Infectious mononucleosis: characterized by a gradual onset, low-grade fever, nasal congestion, pharyngitis (enlarged lacunae, granularity of the posterior pharyngeal wall), conjunctivitis, lymphadenopathy, and hepatosplenomegaly.
• Meningococcal infection: distinguished by an acute onset, rapid escalation of headache, vomiting, the appearance of petechial rash on the limbs, and meningeal signs (nuchal rigidity, hyperesthesia, hyperacusis). Blood tests reveal pronounced leukocytosis with a sharp shift to the left.

Class and exam questions

What else to study on this topic

• Features of empirical antibiotic therapy for pneumonia
• Differential diagnosis of meningeal syndrome in acute respiratory infections
• Pathogenesis of metabolic acidosis in acute respiratory failure
• Clinical presentation and diagnosis of staphylococcal pneumonia

Other topics in the "Respiratory Infections" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.