Acute respiratory distress syndrome (ARDS)

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.

Septic shock is the subset of sepsis with hypotension requiring vasopressors to maintain a mean arterial pressure above 65 mm Hg plus a serum lactate above 2 mmol/L despite adequate fluid resuscitation, carrying in-hospital mortality of 40% or higher. Management is a timed sequence: 30 mL/kg crystalloid bolus, blood cultures and broad-spectrum antibiotics within 1 hour, norepinephrine titrated to MAP >=65, and escalation to a second vasopressor and stress-dose hydrocortisone when hypotension persists.

Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.

Pulmonary embolism is thrombus, usually from a lower-extremity deep vein thrombosis, obstructing the pulmonary arterial circulation and causing V/Q mismatch, right ventricular strain, and hypoxemia. Diagnosis follows Wells criteria (with PERC in low-risk patients) to sequence D-dimer, CT pulmonary angiography, and V/Q scanning, and management is risk-stratified anticoagulation escalating to thrombolysis or embolectomy for hemodynamic instability.

Idiopathic pulmonary fibrosis is a chronic, progressive fibrosing lung disease of unknown cause defined by a usual interstitial pneumonia (UIP) pattern, presenting with progressive dyspnea, dry cough, bibasilar Velcro crackles, and clubbing in older smokers. A definite UIP pattern on high-resolution CT confirms the diagnosis without biopsy; management centers on antifibrotic therapy (pirfenidone or nintedanib), oxygen, and early lung transplant referral, since corticosteroids are not indicated and median survival is 3 to 5 years.

Ventilator-associated pneumonia is a new pulmonary infiltrate with clinical signs of infection developing more than 48 hours after endotracheal intubation, driven by gram-negative bacilli and Staphylococcus aureus; empiric antipseudomonal therapy is started immediately from a semiquantitative respiratory culture and paired with ventilator-bundle prevention.

Acute pancreatitis is acinar-cell autodigestion and inflammation of the pancreas, most often from gallstones or alcohol, diagnosed by the revised Atlanta criteria and graded mild, moderately severe, or severe by organ failure. Management centers on early goal-directed lactated Ringer's resuscitation, analgesia, early enteral feeding, and timed ERCP for gallstone pancreatitis with cholangitis, reserving antibiotics for confirmed infected necrosis.

Fat embolism syndrome is a clinical triad of hypoxemia, neurologic dysfunction, and petechial rash occurring 24 to 72 hours after long-bone or pelvic fracture, treated with supportive oxygen/ventilation and prevented above all by early fracture fixation within 24 hours.