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Acute Pneumonia: Classification, Etiology, and Diagnostic Criteria

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1. Modern Classification of Acute Pneumonia

A. By Setting of Acquisition

Per Critical Issues in the Management of Adult Patients Presenting to the ED with CAP, the HCAP category has been officially retired in favor of HAP and CAP with specific MDR risk factor assessment.

B. By Morphological Pattern

• Lobar (croupous) pneumonia — consolidation of an entire lobe; classic S. pneumoniae
• Bronchopneumonia (lobular) — patchy, multifocal; Staphylococcus, gram-negatives
• Interstitial pneumonia — predominantly interstitial infiltrates; atypical/viral organisms

C. By Etiological Agent

• Bacterial (typical and atypical)
• Viral
• Fungal
• Parasitic
• Mixed

D. By Clinical Severity

• Mild — outpatient treatment
• Moderate — hospitalization required
• Severe — ICU admission (using PSI/PORT, CURB-65, or ATS/IDSA major/minor criteria)

E. By Host Immune Status

• Immunocompetent
• Immunocompromised (HIV/AIDS, transplant, chemotherapy, steroids)

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2. Etiological Factors Determining Course Characteristics

Typical Bacterial Pathogens (CAP)

Atypical Pathogens

Viral Agents

• Influenza A/B, SARS-CoV-2, RSV, CMV (immunocompromised), adenovirus
• Interstitial pattern, bilateral ground-glass opacities, rapid progression possible

Fungal Agents

• Candida (rarely true pneumonia), Aspergillus (immunocompromised), Pneumocystis jirovecii (PCP — HIV/AIDS), Histoplasma, Cryptococcus

Host Factors Influencing Course

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3. Diagnostic Criteria for Community-Acquired Pneumonia (CAP)

Clinical Criteria

1. Acute onset of fever (>38°C) or hypothermia (<36°C)
2. Cough (new or worsening), with or without purulent sputum/change in sputum character
3. Signs of pulmonary consolidation on physical exam (dullness, bronchial breathing, increased vocal fremitus, crepitations)
4. Dyspnea, tachypnea (RR >20/min)
5. Leukocytosis (>10×10⁹/L) or leukopenia (<4×10⁹/L), or bandemia (>10%)

Radiological Criteria

• Chest X-ray: new lobar/segmental consolidation, or diffuse bilateral infiltrates
• CT chest (more sensitive): ground-glass opacities, consolidation, tree-in-bud

Microbiological Workup (for hospitalized patients)

• Sputum Gram stain and culture (before antibiotics)
• Blood cultures ×2 (before antibiotics)
• Urinary antigen: S. pneumoniae and Legionella
• Nasopharyngeal swab for respiratory viruses (PCR)
• Procalcitonin and CRP (support bacterial etiology)

Severity Scoring

• 0–1: outpatient; 2: hospitalize; 3–5: ICU consideration

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4. Diagnostic Criteria for Hospital-Acquired Pneumonia (HAP)

Definition

Clinical Criteria (≥2 of the following, plus new infiltrate):

1. New or progressive radiological infiltrate
2. Fever >38.3°C or hypothermia
3. Purulent tracheal/bronchial secretions (new or worsening)
4. Leukocytosis (>12×10⁹/L) or leukopenia (<4×10⁹/L)
5. Deterioration in oxygenation (↓PaO₂/FiO₂ or ↑O₂ requirement)

Clinical Pulmonary Infection Score (CPIS) for VAP

Key Pathogens (MDR organisms predominate)

MDR Risk Factors (guide antibiotic choice)

• Prior IV antibiotics within 90 days
• Septic shock at time of VAP
• ARDS preceding VAP
• ≥5 days hospitalization before pneumonia
• Acute renal replacement therapy

From Harrison's Principles of Internal Medicine (21st ed., p. 4248): Risk factors include events that increase colonization by potential pathogens (prior antimicrobial therapy, decreased gastric acidity), factors that facilitate aspiration (intubation, decreased consciousness, nasogastric tube), and factors that reduce pulmonary defenses (COPD, upper abdominal surgery).

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5. Diagnostic Criteria for Atypical Pneumonia

General Features Suggesting Atypical Etiology

Pathogen-Specific Criteria

• Age 5–35 years most common
• Cold agglutinins positive (>1:64) — non-specific but supportive
• Extrapulmonary: hemolytic anemia, Stevens-Johnson syndrome, meningoencephalitis, myocarditis
• PCR of nasopharyngeal swab or sputum (gold standard)
• Serology: IgM/IgG (4-fold rise in paired samples)

• Preceding pharyngitis, laryngitis, hoarseness
• Mild course, prolonged cough
• Serology: microimmunofluorescence (MIF) — IgM ≥1:16 or 4-fold IgG rise
• PCR of respiratory secretions

• Exposure to water aerosols (cooling towers, spa pools)
• High fever (>39°C), rigors, relative bradycardia
• GI: diarrhea, nausea, abdominal pain
• CNS: confusion, encephalopathy
• Labs: hyponatremia, elevated LFTs, elevated CPK, hematuria, elevated ferritin
• Urinary Legionella antigen (rapid, serogroup 1 only, gold standard for diagnosis)
• Culture on BCYE agar; DFA; PCR

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6. Diagnostic Criteria for Viral Pneumonia

Suggestive Clinical Features

• Preceding upper respiratory illness (rhinorrhea, sore throat, myalgia)
• Dry cough, progressive dyspnea
• High fever, bilateral symptoms
• Absence of dominant bacterial signs (no rusty sputum, no lobar consolidation early)
• History of influenza season, close contacts, travel

Radiological Features

• Bilateral interstitial or ground-glass opacities (GGO)
• Peribronchovascular distribution (influenza, COVID-19)
• "Crazy paving" pattern on CT (COVID-19, PCP)
• Rapid radiological progression

Laboratory Features

• Normal or mildly elevated WBC; lymphopenia common (influenza, SARS-CoV-2)
• Normal or mildly elevated CRP/PCT (PCT usually <0.5 ng/mL in pure viral)
• Elevated LDH (correlates with severity)

Specific Diagnostic Criteria by Virus

Confirmation

• Multiplex respiratory virus PCR panel (NP swab or BAL) — most comprehensive
• Serology (retrospective, 4-fold rise in paired titers)
• Bronchoalveolar lavage (BAL) + PCR — gold standard for lower respiratory tract

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7. Diagnostic Criteria for Fungal Pneumonia

Overview

Major Fungal Pathogens and Diagnostic Criteria

Pneumocystis jirovecii Pneumonia (PCP)

Invasive Pulmonary Aspergillosis (IPA)

• Proven: histopathological/cytopathological evidence of invasion
• Probable: host factor + clinical criterion + mycological criterion (GM/culture)
• Possible: host factor + clinical criterion only

Pulmonary Cryptococcosis

• Setting: AIDS (CD4 <100), transplant
• Symptoms: cough, fever, pleuritis; may disseminate to CNS
• Diagnosis: Serum/BAL cryptococcal antigen (CrAg lateral flow assay — highly sensitive/specific); India ink on BAL; fungal culture

Endemic Mycoses (Histoplasma, Coccidioides, Blastomyces)

• Geographic exposure history critical
• Serology (complement fixation, immunodiffusion)
• Urinary antigen (Histoplasma — highly sensitive in disseminated disease)
• BAL/biopsy culture and histology

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8. Features of Pneumonia in Individuals with Immunodeficiencies

General Principles

Key Features by Type of Immunodeficiency

Clinical Presentation Peculiarities

1. Blunted inflammatory response — fever may be absent or low-grade; cough minimal; classic consolidation absent
2. Radiological dissociation — CT findings may be extensive while clinical signs are subtle
3. Rapid deterioration — progression to respiratory failure can occur within hours
4. Multiple simultaneous pathogens — co-infections are common (e.g., bacterial + CMV + PCP)
5. Unusual pathogens — organisms rare in immunocompetent hosts become common
6. Atypical CXR — interstitial, bilateral, miliary, or even normal in early PCP

Diagnostic Approach in Immunocompromised

• Broad multiplex PCR (respiratory viruses, bacteria, fungi) from BAL
• BAL is essential — more sensitive than sputum; bronchoscopy with BAL within 24–48 h if no rapid improvement
• Serum biomarkers: β-D-glucan, galactomannan, CrAg, CMV PCR, LDH
• CT chest preferred over plain X-ray — more sensitive for early IPA (halo sign), PCP (GGO)
• Open lung biopsy or transbronchial biopsy if BAL non-diagnostic and patient deteriorating
• Blood cultures (bacterial + fungal)

Management Principles

• Empiric coverage must be broader — cover typical bacteria + opportunistic fungi/viruses based on CD4/neutrophil count and type of immunosuppression
• Prophylaxis (TMP-SMX for PCP, fluconazole/voriconazole for fungi, acyclovir/valganciclovir for viral reactivation) prevents pneumonia in highest-risk groups
• Reversal of immunosuppression where possible (reduce steroids, G-CSF for neutropenia, ART for HIV) is critical adjunct
• ICU threshold lower — early intubation consideration given rapid deterioration risk

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Pneumonia: Special Populations, Treatment, Complications, and Management

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9. Peculiarities of the Course of Pneumonia in Elderly People

Epidemiological Context

Pathophysiological Basis of Atypical Presentation

Clinical Features in the Elderly

Harrison's Principles of Internal Medicine, 21st ed. (p. 4398): "Among the elderly, the presenting clinical symptoms may be less specific, with confusion or malaise but without fever or cough. In such cases, a high index of suspicion is required because failure to treat pneumococcal pneumonia promptly in an elderly patient is likely to result in rapid evolution of the infection, with increased severity, morbidity, and risk of death."

• Fever: absent in up to 30–40% of elderly patients — or low-grade only
• Cough: often minimal due to reduced cough reflex
• Pleuritic pain: frequently absent
• Leukocytosis: may be normal or even leukopenic despite serious infection

1. Acute confusion / delirium — often the dominant or sole presenting feature
2. Falls — unexplained falls may be the first sign
3. Functional decline — sudden inability to perform ADLs
4. Anorexia, malaise, weakness
5. Tachypnea — often the most reliable sign; RR >25 is an important clue
6. Decompensation of chronic disease (worsening heart failure, worsening COPD)
7. Hypothermia (poor prognostic sign)

Radiological Considerations

• CXR may underestimate extent due to dehydration (infiltrate "appears" after fluid resuscitation)
• Higher prevalence of atelectasis and pleural effusion
• CT chest more sensitive and often necessary

Pathogens in the Elderly

Prognosis and Severity

• PSI (PORT) scores naturally higher due to age factor
• CURB-65 may underestimate severity — clinical judgment essential
• Higher rates of: respiratory failure, septic shock, multi-organ failure, prolonged hospitalization
• 30-day mortality: up to 20–30% for hospitalized elderly vs. ~5% for younger adults

Management Principles in the Elderly

• Lower threshold for hospitalization and ICU
• Early antibiotic administration is critical
• Careful fluid resuscitation (risk of fluid overload with cardiac comorbidity)
• Swallowing assessment and dysphagia management
• Delirium prevention and management
• Vaccination: pneumococcal (PCV15/PCV20 + PPSV23) and annual influenza vaccine

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10. Features of the Course of Aspiration Pneumonia

Definition and Pathogenesis

Harrison's Principles of Internal Medicine, 21st ed. (p. 5086): "Bacterial aspiration pneumonia develops over a period of several days or weeks rather than hours. The pathogenesis includes some combination of an increased bacterial burden, increased virulence of the organisms aspirated, and potential airway damage related to aspiration of gastric fluid."

Predisposing Risk Factors

Clinical Features

Harrison's (p. 5086): "Patients generally report fever, malaise, and sputum production. In some patients, weight loss and anemia reflect a more chronic process. Usually the history reveals factors predisposing to aspiration...Sputum characteristically is not malodorous unless the process has been ongoing for at least a week."

• Subacute onset — develops over days to weeks (unlike bacterial lobar pneumonia)
• Fever, productive cough, malaise
• Putrid/foul-smelling sputum — hallmark of anaerobic infection (appears after ≥1 week)
• Weight loss, anemia — suggest chronic/necrotizing process
• No response to standard beta-lactams — anaerobes not covered

Radiological Localization (Dependent Segment Rule)

Complications

• Lung abscess — cavitation within consolidation; air-fluid level on CXR
• Empyema — pleural infection requiring drainage
• Necrotizing pneumonia — multiple small cavities within consolidated segment
• Bronchopleural fistula

Bacteriology

• Anaerobes dominate: Peptostreptococcus, Bacteroides, Fusobacterium, Prevotella
• Mixed aerobic-anaerobic: Streptococcus spp., S. aureus, gram-negative bacilli
• Community-acquired: predominantly anaerobes + oral streptococci
• Hospital-acquired: add gram-negative enteric organisms and S. aureus (including MRSA)

Treatment

• Postural drainage, physiotherapy
• Treat underlying dysphagia; speech therapy assessment
• Dental hygiene optimization

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11. Principles of Antibacterial Therapy of Pneumonia

Core Principles

• Mild-moderate CAP: 5 days (if clinically stable by day 3–5)
• Severe CAP / bacteremia: 7–10 days
• Legionella, Pseudomonas: 14 days minimum
• HAP/VAP: 7–8 days (unless MDR, then 14 days)
• Lung abscess / aspiration: 4–6 weeks

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Empiric Antibiotic Regimens

Community-Acquired Pneumonia (CAP)

Hospital-Acquired Pneumonia (HAP)

Atypical Pneumonia

• Macrolides (azithromycin, clarithromycin) — first-line for Mycoplasma, Chlamydophila
• Fluoroquinolones (levofloxacin, moxifloxacin) — Legionella and atypical organisms
• Doxycycline — alternative for Mycoplasma, Chlamydophila

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Antibiotic Stewardship Principles

• Use procalcitonin to guide initiation and cessation (PCT <0.25 ng/mL — withhold/stop; >0.5 ng/mL — start/continue)
• De-escalate from broad-spectrum to narrow-spectrum once pathogen identified
• Avoid unnecessary prolonged courses
• Reassess at 48–72 h ("antibiotic time-out")

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12. Approaches to Pathogenetic Therapy of Acute Pneumonia

1. Anti-Inflammatory Therapy

• Corticosteroids: Adjunct in severe CAP — methylprednisolone 0.5 mg/kg/day for 5 days reduces time to clinical stability, length of stay, and risk of treatment failure (evidence strongest for CRP >150 mg/L)
  • Caution: May increase risk of superinfection; avoid in influenza pneumonia
  • Also indicated in severe PCP (prednisone 40mg BD for 5 days → taper) — reduces mortality in HIV/PCP when PaO₂ <70 mmHg

2. Lung Microbiome and Mucosal Defense Support

• Mucolytics (N-acetylcysteine, ambroxol, bromhexine): Reduce sputum viscosity, improve mucociliary clearance, facilitate expectoration; N-acetylcysteine also has antioxidant properties
• Bronchodilators (salbutamol, ipratropium): Especially in patients with COPD or bronchospasm; improve ventilation of affected areas

3. Immune Modulation

• IVIG (intravenous immunoglobulin): Used in select immunodeficient patients (hypogammaglobulinemia); evidence limited for routine use
• G-CSF (filgrastim): For neutropenia-associated pneumonia — stimulates neutrophil recovery

4. Restoration of Surfactant Function

• Severe pneumonia destroys alveolar type II pneumocytes → surfactant deficiency → alveolar collapse
• Exogenous surfactant therapy: Evidence limited in adults; used in some centers for ARDS complicating pneumonia

5. Antioxidant Therapy

• N-acetylcysteine (NAC): Replenishes glutathione, reduces oxidative lung injury
• Vitamin C and E: Antioxidant support, limited clinical evidence

6. Management of Alveolar-Capillary Permeability / ARDS

• When pneumonia progresses to ARDS:
  • Lung-protective ventilation: Tidal volume 6 mL/kg IBW, plateau pressure <30 cmH₂O
  • Prone positioning: For PaO₂/FiO₂ <150 mmHg — reduces mortality
  • Neuromuscular blockade (cisatracurium): For severe ARDS in first 48 h

7. Restoration of Microcirculation and Hemostasis

• Heparins (low molecular weight): Prevent microvascular thrombosis and DVT; especially important in severe CAP and immobile patients
• Pentoxifylline: Improves microvascular flow (limited evidence)

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13. Principles of Symptomatic Therapy and Oxygen Therapy for Pneumonia

Symptomatic Therapy

Fever Management

• Antipyretics: Paracetamol (acetaminophen) 500–1000 mg q6h PRN — use only for fever >38.5°C causing discomfort or hemodynamic stress
• Avoid aggressive fever suppression — fever is part of immune response
• NSAIDs (ibuprofen): Alternative; caution in renal impairment and GI disease

Cough Management

• Productive cough: Do NOT suppress — facilitate with mucolytics (ambroxol 30mg TID, bromhexine, carbocisteine), physiotherapy, adequate hydration
• Dry, distressing cough: Short-course codeine-based suppressants or butamirate; used cautiously (risk of sputum retention)

Pain (Pleuritic Chest Pain)

• Paracetamol ± NSAIDs (ibuprofen, diclofenac)
• Short-course opioids for severe pleuritic pain (morphine small doses) — balance with respiratory depression risk

Hydration

• Oral hydration preferred for mild cases
• IV crystalloids (normal saline or Ringer's lactate) for febrile/dehydrated patients or those unable to take oral fluids
• Target urine output >0.5 mL/kg/h
• Careful in elderly and those with cardiac disease — risk of fluid overload

Nutrition

• Early enteral nutrition in mechanically ventilated patients
• High-protein diet; nutritional supplementation in malnourished patients

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Oxygen Therapy

Indications

• SpO₂ <94% in general patients
• SpO₂ <88% in COPD patients (target 88–92% to avoid hypercapnic respiratory failure)
• All patients with severe CAP (CURB-65 ≥3, PSI class IV–V)
• Any signs of respiratory distress (RR >30, accessory muscle use, cyanosis)

Oxygen Delivery Devices

Targets

• SpO₂ 94–98% for most patients (BTS guideline)
• SpO₂ 88–92% for COPD/chronic hypercapnic patients
• Avoid excessive hyperoxia — associated with increased mortality in some studies

Escalation Pathway

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14. Pulmonary Complications of Acute Pneumonia

1. Parapneumonic Pleural Effusion and Empyema Thoracis

• Simple parapneumonic effusion: Exudate, sterile; resolves with antibiotics
• Complicated parapneumonic effusion: Low pH (<7.2), low glucose (<2.2 mmol/L), positive Gram stain/culture → requires drainage
• Empyema: Frank pus in pleural space → chest tube drainage mandatory; surgical decortication if loculated
• Management: Thoracentesis for diagnosis; chest tube (ICD); intrapleural fibrinolytics (tPA + DNase) for loculations; VATS if fails

2. Lung Abscess

• Cavitation with central necrosis within consolidated parenchyma
• Air-fluid level on CXR/CT
• Predominantly anaerobic or mixed organisms; also S. aureus, Klebsiella
• Treatment: Prolonged antibiotics (4–6 weeks); percutaneous drainage or surgery if refractory

3. Necrotizing Pneumonia

• Multiple small cavities within consolidated lobe
• S. aureus (especially PVL-positive MRSA), Klebsiella, Streptococcus group A
• High mortality; aggressive antibiotic therapy; linezolid preferred for PVL-MRSA (suppresses toxin production)

4. Respiratory Failure (Type I and II)

• Type I (hypoxemic): Ventilation-perfusion mismatch and shunting within consolidated areas
• Type II (hypercapnic): Exhaustion, severe COPD superimposed, or mechanical ventilatory failure
• Management: HFNC, NIV, or invasive ventilation (lung-protective strategy)

5. Acute Respiratory Distress Syndrome (ARDS)

• Pneumonia is the most common cause of ARDS
• Berlin criteria: bilateral opacities, PaO₂/FiO₂ <300, not fully explained by cardiac failure, onset within 1 week
• Mortality 30–45% in severe ARDS (PaO₂/FiO₂ <100)

6. Pneumothorax

• Rare complication; more common with S. aureus pneumonia (pneumatocele rupture), necrotizing pneumonia
• Bronchopleural fistula may develop

7. Acute Exacerbation of Underlying Lung Disease

• Triggers acute exacerbation of COPD, bronchiectasis, or pulmonary fibrosis with rapid deterioration

8. Pulmonary Fibrosis (Post-pneumonia)

• Organizing pneumonia (cryptogenic organizing pneumonia pattern) — responds to steroids
• Fibrotic sequelae after severe viral pneumonia (COVID-19, influenza)

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15. Extrapulmonary Complications of Acute Pneumonia

1. Sepsis and Septic Shock

• The most dangerous extrapulmonary complication; pneumonia is the leading cause of sepsis
• Criteria: suspected infection + SOFA ≥2 (sepsis); MAP <65 mmHg + vasopressor requirement + lactate >2 mmol/L despite resuscitation (septic shock)
• Management: Sepsis-3 bundle — early antibiotics, IV fluids, vasopressors (norepinephrine first-line)

2. Bacteremia / Bloodstream Infection

• Occurs in 10–30% of hospitalized CAP patients
• S. pneumoniae most common; S. aureus, gram-negatives in HAP
• Increases mortality 2–3×; requires blood cultures before antibiotics

3. Infective Endocarditis

• Rare; most relevant with S. pneumoniae or S. aureus bacteremia complicating pneumonia
• Austria syndrome: S. pneumoniae triad — meningitis + pneumonia + endocarditis

4. Meningitis / CNS Complications

• Hematogenous spread of S. pneumoniae — pneumococcal meningitis
• Toxic encephalopathy: confusion/delirium secondary to systemic inflammation and hypoxia
• Septic emboli (rare)

5. Pericarditis and Myocarditis

• Viral myocarditis (influenza, SARS-CoV-2, enteroviruses) complicating viral pneumonia
• Direct extension of bacterial infection to pericardium (S. pneumoniae, S. aureus)
• Troponin elevation in severe pneumonia — associated with higher mortality

6. Cardiac Arrhythmias and Acute Coronary Syndrome

• Hypoxia, systemic inflammation, and sepsis increase risk of atrial fibrillation, ventricular arrhythmias
• Pneumonia increases short-term (90-day) MI risk — systemic inflammation promotes plaque instability

7. Acute Kidney Injury (AKI)

• Sepsis-associated (renal hypoperfusion, inflammatory mediators)
• Nephrotoxic antibiotics (aminoglycosides, vancomycin) add risk
• Monitor creatinine, urine output; dose-adjust antibiotics; avoid nephrotoxins

8. Hepatic Dysfunction

• Sepsis-associated cholestasis, elevated LFTs
• Particularly prominent in Legionella pneumonia (hepatitis pattern)

9. DIC (Disseminated Intravascular Coagulation)

• In severe sepsis/septic shock complicating pneumonia
• Thrombocytopenia, prolonged PT/APTT, elevated D-dimer, low fibrinogen
• Treatment: underlying cause; FFP, cryoprecipitate, platelet transfusion as needed

10. Ileus and Stress Ulcers

• Systemic illness, hypoxia, and immobility — paralytic ileus common in ICU patients
• Stress ulcer prophylaxis (PPI or H₂ blocker) for mechanically ventilated patients

11. Thromboembolic Complications (DVT/PE)

• Immobility, hypercoagulability of systemic inflammation
• LMWH prophylaxis mandatory for all hospitalized pneumonia patients without contraindication

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16. Combating Complications and Intoxication in Pneumonia

Detoxification Therapy (Combating Intoxication)

1. Adequate Fluid Therapy

• Crystalloids (normal saline, Ringer's lactate, Plasmalyte): 30 mL/kg bolus in first 3 hours for sepsis (Surviving Sepsis Campaign)
• Reassess with dynamic fluid responsiveness tests (passive leg raise, pulse pressure variation)
• Colloids (albumin 4%): For persistent shock despite crystalloids; consider in hypoalbuminemia
• Monitor: urine output, HR, MAP, CVP, lactate clearance
• Avoid fluid overload — target zero to slightly negative fluid balance after initial resuscitation

2. Vasopressor Therapy

• Norepinephrine: First-line vasopressor for septic shock (target MAP ≥65 mmHg)
• Vasopressin (0.03 U/min): Add-on to norepinephrine — reduces norepinephrine requirements
• Epinephrine: Third-line; caution — increases lactate, tachycardia
• Dopamine: No longer preferred (higher arrhythmia risk)

3. Extracorporeal Detoxification Methods

• Continuous Renal Replacement Therapy (CRRT): Removes inflammatory cytokines, eliminates nephrotoxic waste products; indicated for AKI + fluid overload + sepsis
• Plasmapheresis: Removes circulating toxins, inflammatory mediators, antibodies (used in some severe viral pneumonias and Legionella); evidence limited
• Hemoperfusion (polymyxin-B column): Binds endotoxin in gram-negative sepsis; evidence mixed but used in some centers

4. Corticosteroids for Intoxication/Septic Shock

• Hydrocortisone 200 mg/day (continuous infusion or 50 mg q6h): For refractory septic shock (persistent vasopressor dependence despite adequate fluids)
• Reduces vasopressor duration and ICU stay; no clear mortality benefit but improves hemodynamics
• Taper as vasopressors are weaned

5. Combating Specific Complications

6. Immunotherapy and Biological Agents

• Anti-IL-6 (tocilizumab): Reduces mortality in severe COVID-19 pneumonia + systemic hyperinflammation (CRP >75 mg/L, ICU admission, rapid deterioration)
• Corticosteroids (dexamethasone 6 mg/day × 10 days): Reduces mortality in COVID-19 requiring oxygen/ventilation
• IVIG: Adjunct in streptococcal/staphylococcal toxic shock syndrome

7. Nutritional Support

• Early enteral nutrition within 24–48 h for ICU patients — maintains gut mucosal integrity, reduces bacterial translocation
• High-protein supplementation (1.2–2.0 g/kg/day)
• Parenteral nutrition if enteral route not feasible for >3 days

8. Prevention of Secondary Complications

• Stress ulcer prophylaxis: PPI (pantoprazole 40 mg IV) or H₂ blocker for all ventilated patients
• DVT prophylaxis: LMWH + mechanical compression stockings
• Glycemic control: Target glucose 7.8–10 mmol/L (140–180 mg/dL) — avoid hypoglycemia
• Early mobilization: Reduces delirium, ICU-acquired weakness, thromboembolic risk
• Oral decontamination (chlorhexidine 0.12%): Reduces VAP incidence in mechanically ventilated patients

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