Complication classification
Depending on the mechanism of development, all adverse consequences of influenza infection are divided into two groups.
Pathogenetically determined (specific) complications include early conditions caused by the direct toxic and damaging effects of the virus:
- Infectious-toxic shock (ITS);
- Respiratory distress syndrome;
- Brain edema;
- Acute cardiovascular failure;
- Serous meningitis and meningoencephalitis.
The second group includes bacterial complications associated with the activation of resident flora or the introduction of exogenous flora against the background of reduced immune defense. These include pneumonia, various ENT pathologies (otitis media, sinusitis, frontal sinusitis), renal involvement (glomerulonephritis), purulent inflammation of the meninges, and severe septic conditions (including bacterial endocarditis and cryptogenic sepsis).
Respiratory distress syndrome
This is a severe complication that frequently affects patients from risk groups at the peak of clinical manifestations (within the first 12–36 hours).
It is characterized by the rapid progression of acute respiratory failure. The patient becomes restless (soon replaced by apathy or loss of consciousness), and the skin acquires a diffuse cyanotic tint. Pronounced tachycardia and a drop in blood pressure below 90 mm Hg are noted.
Key respiratory signs:
- Acute dyspnea (respiratory rate exceeds 30 breaths per minute).
- Noisy breathing.
- Specific cough: scanty sputum with blood admixture. Laboratory analysis reveals mononuclearocytosis in it.
Auscultatory findings change rapidly. Initially, only dry wheezes are heard over the lungs. Then crepitation and fine moist rales join them, after which breath sounds become sharply weakened.
Nervous system involvement
Neurological complications of influenza include serous meningitis and meningoencephalitis. It is important to understand that in serous involvement, the virus itself does not cause true inflammation of the meninges. Symptoms arise due to profound microcirculatory disturbances and diapedetic hemorrhages.
Symptoms of meningeal syndrome:
- Severe bursting and pressing headache, insomnia.
- Repeated vomiting that brings no relief.
- Moderate meningeal signs, hyperesthesia, delirium.
- Upon lumbar puncture, the cerebrospinal fluid emerges under high pressure; moderate mononuclear pleocytosis (pleocytosis) up to 20–30 cells and an elevated protein level are characteristic.
When the brain tissue is involved (meningoencephalitis), seizures, impaired consciousness, vestibular disorders (ataxia, nystagmus), and transient focal symptoms such as facial nerve palsy join in. Hemorrhagic encephalitis is the most dangerous form, rapidly leading to coma and death.
Shock and cerebral edema
These early complications often develop in parallel, exacerbating each other's course in the terminal stage of the disease.
Infectious-toxic shock (ITS) is characterized by a paradoxical clinical picture: against the background of a sharp drop in body temperature and blood pressure, the patient develops progressive tachycardia. Consciousness is depressed to stupor. Due to gross microcirculatory failures, the skin becomes pale, cyanotic, and a petechial rash may appear. The patient dies from multiorgan and cardiovascular failure.
Cerebral edema is triggered by systemic hypoxemia and microcirculatory stasis. Unbearable headache, vomiting, and dizziness serve as the first "warning signs". Seizure syndrome, focal symptoms, and loss of consciousness rapidly join in.
Briefly: answers to topical questions
Which pathogens most frequently cause secondary bacterial pneumonia following influenza?
The most frequent pathogens of secondary bacterial pneumonia following influenza are representatives of gram-positive flora. Haemophilus influenzae is also considered a likely pathogen.
- Pneumococcus is a gram-positive microorganism ranking first in significance.
- Staphylococcus is also a frequent cause of post-influenza pneumonia.
- Streptococcus is among the significant gram-positive pathogens.
- Haemophilus influenzae is a probable pathogen in pneumonia complicating influenza.
In addition, pneumonia can be caused by gram-negative and anaerobic flora: Enterobacter, Serratia, Klebsiella, and Bacteroides.
What changes are detected on chest X-ray in influenza-associated respiratory distress syndrome?
In influenza-associated respiratory distress syndrome, chest X-ray reveals bilateral infiltrative changes:
- bilateral multiple infiltrates;
- bilateral confluent infiltrative opacities radiating from the lung roots;
- such radiological findings can simulate cardiogenic pulmonary edema.
How does the character of sputum in specific ARDS differ from that in bacterial pneumonia in influenza patients?
The character of sputum in specific respiratory distress syndrome differs from that in viral-bacterial/bacterial pneumonia in influenza patients.
| Sign | Specific ARDS | Viral-bacterial/bacterial pneumonia |
|---|---|---|
| Volume and appearance | Scanty, bloody sputum | Purulent or mucopurulent/bloody sputum |
| Cellular composition | Mononuclearocytosis detected in sputum | Polymorphonuclear leukocytes detected in sputum/exudate |
| Microbiological feature | Not specified in sources for ARDS | Bacteria detected in sputum/exudate |
For quick memorization of early specific complications, use the acronym SHOMOR: Shock (toxic-infectious), Brain edema, Acute cardiovascular failure, Respiratory distress syndrome.
Class and exam questions
Why is there no pus in serous meningitis of influenza etiology?
The influenza virus does not cause classical purulent inflammation of the meninges. The pathogenesis is based on severe microcirculatory disorders, vascular permeability, and diapedetic hemorrhages into the brain tissue.
How to differentiate TSS based on hemodynamic and temperature parameters?
Infectious-toxic shock is characterized by a so-called "scissors-like" divergence: body temperature and blood pressure drop rapidly, while heart rate (tachycardia) increases sharply.
What sputum changes are typical for influenza-induced distress syndrome?
During the development of ARDS, coughing is accompanied by the production of very scanty sputum with blood streaks. Cytological examination reveals a predominance of mononuclear cells.
What else to study on this topic
- Criteria for severity grades of uncomplicated influenza
- Clinical presentation of intoxication syndrome
- Features of tracheobronchial tree involvement in respiratory syndrome
- ICD-10 coding for influenza (difference between categories J10 and J11)
- Characteristics of hemorrhagic syndrome and its mucosal manifestations
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