Adult Critical Care

Master ARDS, sepsis, shock management, and multisystem critical illness for the NBRC exam.

advanced100 min estimated3 lessons

ARDS: Diagnosis and Berlin Criteria

Acute Respiratory Distress Syndrome (ARDS) is a life-threatening form of acute hypoxemic respiratory failure characterized by diffuse alveolar damage, bilateral infiltrates, and refractory hypoxemia.

Berlin Definition (2012): 1. Timing: within 1 week of known insult 2. Imaging: bilateral opacities not explained by effusions, lobar/lung collapse, or nodules 3. Origin: not explained by cardiac failure or fluid overload (PCWP ≤18) 4. Oxygenation (on PEEP ≥5 cmH2O): - Mild: P/F 200–300 - Moderate: P/F 100–200 - Severe: P/F <100

Common causes (ARDS 'triggers'): sepsis (#1 cause), aspiration pneumonia, trauma, blood transfusions (TRALI), pancreatitis, inhalation injury.

Berlin criteria: bilateral infiltrates + P/F <300 on PEEP ≥5 + non-cardiogenic + acute onset
P/F <300 = ARDS (mild); <200 = moderate; <100 = severe
Sepsis is the #1 cause of ARDS
PCWP ≤18 mmHg differentiates ARDS from cardiogenic pulmonary edema
ARDS mortality: mild 27%, moderate 32%, severe 45%

Clinical tip

Always check PCWP or clinical evidence of left heart failure before diagnosing ARDS — cardiogenic pulmonary edema must be excluded.

Lung-Protective Ventilation in ARDS

The ARDSNet protocol (ARMA trial) demonstrated that low-volume, low-pressure ventilation reduces mortality in ARDS.

ARDSNet protocol: - Vt: 6 mL/kg IBW (can decrease to 4 if Pplat >30) - Pplat: <30 cmH2O - Driving pressure: <15 cmH2O - PEEP: per ARDSNet lower or higher PEEP tables (FiO2-paired) - Target SpO2 88–95%, PaO2 55–80 mmHg - Permissive hypercapnia acceptable (pH ≥7.20)

Prone positioning for 16+ hours/day reduces mortality in moderate-severe ARDS (P/F <150). Neuromuscular blockade (NMBA) for 48 hours may improve outcomes in early severe ARDS.

ARDSNet: 6 mL/kg IBW, Pplat <30, driving pressure <15
Prone positioning: ≥16 hr/day, P/F <150 — reduces mortality
Target PaO2 55–80 mmHg and SpO2 88–95% (avoid hyperoxia)
Permissive hypercapnia: pH ≥7.20 acceptable to limit pressures
NMBA (cisatracurium) for 48 hours may improve early severe ARDS

Clinical tip

Proning improves oxygenation by redistributing perfusion to better-ventilated dorsal lung regions. Turn patients within 1–2 hours of severe ARDS diagnosis.

Sepsis and Septic Shock: Recognition and Management

Sepsis is life-threatening organ dysfunction caused by dysregulated host response to infection. Septic shock = sepsis + vasopressor requirement + lactate >2 mmol/L despite adequate resuscitation.

qSOFA (quick SOFA) screening: RR ≥22, altered mentation, SBP ≤100. ≥2 criteria suggests high risk.

Surviving Sepsis Campaign 1-hour bundle: 1. Measure lactate 2. Blood cultures before antibiotics 3. Broad-spectrum antibiotics 4. 30 mL/kg crystalloid for hypotension or lactate ≥4 5. Vasopressors if MAP <65 despite fluids

Norepinephrine is first-line vasopressor. Add vasopressin for refractory shock. Dobutamine for cardiogenic component.

Septic shock: sepsis + vasopressors + lactate >2 despite resuscitation
1-hour bundle: lactate, cultures, antibiotics, fluids, vasopressors
Norepinephrine: first-line vasopressor for septic shock
30 mL/kg crystalloid initial resuscitation for sepsis-induced hypoperfusion
Antibiotics within 1 hour — every hour delay increases mortality

Clinical tip

In septic shock, the initial high cardiac output (hyperdynamic phase) can fool you — don't mistake high CO and warm extremities for adequate perfusion. Check lactate.

Clinical cases

New-Onset ARDS Management

A 52-year-old with severe pneumonia is intubated. Vent settings: AC/VC, Vt 600 mL (actual wt 80 kg, ht 5'10"), RR 18, FiO2 0.80, PEEP 8. ABG: pH 7.38, PaCO2 42, PaO2 68. Bilateral infiltrates on CXR.

Is this patient on appropriate ARDS ventilation? What changes should be made?

No. IBW for 5'10" male = 50 + 2.3 × 10 = 73 kg. Target Vt = 6 × 73 = 438 mL. Reduce from 600 to 438 mL and optimize PEEP per ARDSNet table.

Using actual weight (80 kg) over-ventilates compared to IBW (73 kg). The excess Vt causes volutrauma. Reduce to 438 mL (6 mL/kg IBW), check Pplat (should be <30), and use ARDSNet PEEP/FiO2 table to optimize oxygenation while reducing FiO2.

NBRC pearls

NBRC tests ARDS Berlin criteria — know P/F cutoffs cold
Prone positioning indication: P/F <150 (some say <150 on ARDSNet settings)
Permissive hypercapnia: pH ≥7.20 acceptable to limit ventilator pressures
Norepinephrine > dopamine for septic shock (lower arrhythmia risk)

Memory tricks

ARDS: 'Bilateral, Bad gas exchange, Below 300, Begins within a week'
Sepsis bundle: 'LBAFV' — Lactate, Blood cultures, Antibiotics, Fluids, Vasopressors

Common mistakes

Using peak pressure instead of plateau pressure for ARDS ventilator management
Delaying prone positioning in severe ARDS patients
Not obtaining blood cultures before starting antibiotics (but don't delay ABX >45 min for cultures)
Over-resuscitating with fluids after initial 30 mL/kg — use dynamic fluid responsiveness testing

Adult Critical Care

ARDS: Diagnosis and Berlin Criteria

Lung-Protective Ventilation in ARDS

Sepsis and Septic Shock: Recognition and Management

Clinical cases

NBRC pearls

Memory tricks

Common mistakes

Related topics

Adult Critical Care

ARDS: Diagnosis and Berlin Criteria

Lung-Protective Ventilation in ARDS

Sepsis and Septic Shock: Recognition and Management

Clinical cases

NBRC pearls

Memory tricks

Common mistakes

Related topics

Lessons

ARDS: Diagnosis and Berlin Criteria

Lung-Protective Ventilation in ARDS

Sepsis and Septic Shock: Recognition and Management

Clinical cases

NBRC pearls

Memory tricks

Common mistakes

Related topics

Lessons

ARDS: Diagnosis and Berlin Criteria

Lung-Protective Ventilation in ARDS

Sepsis and Septic Shock: Recognition and Management

Clinical cases

NBRC pearls

Memory tricks

Common mistakes

Related topics