Adult Respiratory Distress Syndrome - Trauma

Introduction

Acute Respiratory Distress Syndrome (ARDS) results from acute lung injury that leads to
- non-cardiogenic pulmonary edema
- respiratory distress
- refractory hypoxemia
- decreased lung compliance
Etiology
- acute endothelial damage resulting from
  - aspiration
  - infection
  - pancreatitis
  - multiple blood transfusions
  - lung injury
  - sepsis or shock
  - major trauma
  - large surface area burns
  - fat emboli
  - thromboembolism
  - multi-system organ failure
Prognosis
- high mortality rate (50% overall) is associated with ARDS even in setting of ICU

Classification

ARDS is represented by three phases

Exudative phase	initially	hyaline membrane comprised of fibrin form
Proliferative phase	3 days	alveolar exudate resolves or organizes
Fibrotic phase	3-4 weeks	alveolar ducts and spaces undergo fibrosis

Presentation

Symptoms
- acute onset (12-48 hours) of
  - dyspnea
  - fever
  - mottled or cyanotic skin
Physical exam
- resistant hypoxia
- intercostal retractions
- rales/crackles and ronchi
- tachypnea

Evaluation
Hypoxemia is refractory to O2 3 different categories of ARDS based on degree of hypoxemia PaO2 / FIO2 ratio < 300 mm Hg= mild PaO2 / FIO2 ratio < 200 mm Hg= moderate PaO2 / FIO2 ratio < 100 mm Hg= severe Chest xray shows patchy pulmonary edema (air space disease) diffuse bilateral pulmonary infiltrates normal sized heart makes CHF less likely Respiratory compliance (<40 mL/cm H20) Positive end-expiratory pressure (>10cm H20) Corrected expired volume per minute (>10L/min)

Differential
Cardiogenic pulmonary edema (i.e. CHF or MI), bilateral pneumonia, SARS

Treatment
Nonoperative PEEP ventilation and steroids treat the underlying pathology/disease Operative early stabilization of long bone fractures (femur) Prevention closely monitor PEEP in patients at-risk of ARDS serial X-rays in concerning patients can assist in early identification and intervention
Complications
Pneumothorax secondary to ventilator with high PEEP