Tuberculosis

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Pathogen: Tuberculosis (TB) is caused by Mycobacterium tuberculosis. Approximately 9 million new cases of active disease develop annually worldwide.
• The Infection Cycle: The disease process is divided into primary infection, a latent phase, and reactivation. While primary infection can be asymptomatic, the organism remains dormant within macrophages.
• Reactivation and Destruction: In periods of immune stress, the organism reactivates, causing intense granulomatous inflammation and caseating necrosis, primarily in the oxygen-rich upper lung fields.
• Dissemination: The bacilli can spread hematogenously, leading to a miliary pattern (disseminated disease) or extrapulmonary involvement, especially in severely immunocompromised patients. Multidrug-resistant strains are increasingly common, specifically among patients with HIV and immigrants from high-risk endemic areas like Southeast Asia.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Isolation (The Critical First Step): Place the patient in a separate waiting area or negative-pressure room immediately, provide them with a surgical mask, and instruct them to cover their mouth and nose when coughing. Do this before proceeding with the full evaluation.
• Managing Massive Hemoptysis: The most emergent presentation of pulmonary TB is massive hemoptysis, defined as (\ge) 600 mL of blood loss in 24 hours. The primary cause of morbidity is asphyxiation, not exsanguination.
• Airway Control: Secure the airway with a large-diameter (8.0-mm) endotracheal tube to accommodate a fiberoptic bronchoscope.
• Positioning: Position the patient with the actively bleeding lung in a dependent (down) position to prevent blood from spilling into the unaffected lung. Consider selective mainstem bronchus intubation.
• Consultation: Obtain emergency consultation for bronchoscopy.
• Pharmacotherapy (The RIPE Regimen): Active TB requires a four-drug regimen to overcome resistance: Isoniazid (INH), Rifampin (RIF), Pyrazinamide (PZA), and Ethambutol (EMB).
• ED Initiation: Routine initiation of antituberculous therapy in the ED is generally avoided to prevent loss to follow-up, but it is appropriate and necessary for life-threatening conditions, TB sepsis, miliary TB, or in critically ill HIV patients. Always initiate in consultation with infectious disease and public health specialists.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Top "Can't-Miss" Mimics:
• Bacterial Pneumonia: Classic community-acquired pneumonia can mimic the cough and fever of TB.
• Opportunistic Infections: Pneumocystis jirovecii pneumonia or fungal pneumonias (e.g., Histoplasma capsulatum) in HIV/AIDS patients.
• Malignancy: Must be considered in older patients presenting with weight loss, hemoptysis, and chronic cough.
• Prioritized Diagnostic Workup:
• Tier 1 (Microbiology): Sputum staining for acid-fast bacillus (AFB) and sputum culture are the gold standards for diagnosis.
• Tier 2 (Routine Labs): Routine ED labs are nonspecific but may reveal normochromic normocytic anemia, an elevated erythrocyte sedimentation rate (ESR), elevated C-reactive protein (CRP), hypercalcemia, and hyponatremia.
• Tier 3 (Screening): The Tuberculin skin test (Mantoux test) can identify exposure but does not differentiate active from latent infection in the acute ED setting.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Chest Radiograph (CXR): Look explicitly for upper lung field involvement, fibrocalcific changes, pleural capping, or a calcified Ghon complex.
• Miliary Pattern: On CXR or chest CT, look for a "miliary" pattern characterized by diffuse, tiny (millet-seed sized) nodular opacities distributed uniformly throughout both lungs.
• Neuroimaging (CT Head): In patients with advanced HIV presenting with altered mental status or seizures, a non-contrast head CT may demonstrate ring-enhancing tuberculomas.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• High-Risk Screening Criteria: Emergency physicians must maintain a high index of suspicion based on epidemiologic risk factors. TB should be suspected and isolated in patients presenting with fever, cough, night sweats, and weight loss who meet any of the following criteria:
• Age > 50 years with a pneumonia-like presentation or prominent respiratory complaint, especially if previous antibiotic treatment has failed.
• HIV infection or use of immunosuppressive medications (e.g., transplant recipients).
• Undomiciled (homeless) status.
• Immigrants from highly endemic areas.
• History of IV drug use or alcoholism.
• Close contact with known TB cases.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Pitfall - The Atypical HIV Presentation: Relying on a "classic" chest radiograph to rule out TB in an immunocompromised patient. In patients with advanced HIV, the CXR may not have the typical appearance of TB, and patients often present with minimal symptoms.
• Pitfall - Delayed Isolation: Waiting for radiographic confirmation before isolating a high-risk patient.
• Critical Action: Respiratory isolation must be initiated promptly at triage for any patient with suggestive symptoms or risk factors, prior to evaluation or obtaining a chest x-ray.
• Critical Action: Avoid starting empiric single-drug therapy. Active TB treatment requires a continuous, monitored combination phase (RIPE therapy) to prevent the emergence of multidrug-resistant strains.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzwords: "Night sweats," "weight loss," "hemoptysis," "apical cavitary lesions," and "Ghon complex".
• High-Yield Fact: Extrapulmonary manifestations of TB frequently tested on boards include Pott's disease (spinal TB), scrofula (cervical tuberculous lymphadenitis), and TB meningitis.
• Common Distractor: A board question asks for the diagnosis of a patient with pleuritic chest pain, and one of the options is "Hampton's hump." Differentiate: Hampton's hump is a classic radiographic sign of a pulmonary embolism, not an extrapulmonary manifestation of tuberculosis.
• Common Distractor: A question asks for the most appropriate immediate action for a coughing, homeless patient with hemoptysis. An option will suggest "Send the patient to radiology for a stat portable CXR." Differentiate: The correct, immediate first step is always to place a mask on the patient and implement respiratory isolation precautions.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Opening Salvo: "Given this patient's presentation of chronic cough, hemoptysis, and weight loss, coupled with their high-risk social history, I am highly concerned for active pulmonary tuberculosis. My immediate priority is staff and patient safety. I will place a surgical mask on the patient, move them to a negative-pressure isolation room, and ensure all staff don N95 respirators."
• Articulating the Workup: "I will perform a targeted physical examination and order a chest radiograph to evaluate for apical cavitary lesions or a miliary pattern. For definitive diagnosis, I am ordering sputum for acid-fast bacillus (AFB) staining and mycobacterial cultures."
• Managing the Hemoptysis (If crashing): "The patient is experiencing massive hemoptysis and protecting their airway is paramount. I am preparing for rapid sequence intubation using a large 8.0 endotracheal tube. I will position the patient in the lateral decubitus position with the bleeding lung down, and emergently consult pulmonology for therapeutic bronchoscopy."
• The Disposition: "The patient is hemodynamically stable but requires admission for initiation of therapy. I will contact the Department of Public Health and consult Infectious Disease to guide the initiation of the four-drug RIPE regimen, ensuring strict respiratory isolation is maintained on the inpatient ward."