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🏥 ICU Essentials for Medical Students

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1. Who Goes to the ICU?

• Continuous hemodynamic monitoring (arterial lines, CVP, PA catheters)
• Mechanical ventilation or high-flow respiratory support
• Vasopressor/inotrope infusions
• Multi-organ failure or risk of rapid deterioration
• Post-operative high-risk surgery monitoring

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2. Types of Shock - The Core ICU Framework

1. Compensated (pre-shock): Body compensates - mild lactate rise, no overt organ failure
2. Decompensated shock: Compensatory mechanisms overwhelmed - organ dysfunction apparent
3. Irreversible shock: Permanent organ failure - high mortality

1. Recognize early
2. Classify the type
3. Initiate therapy simultaneously with evaluation
4. Aim to restore oxygen delivery (DO2)

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3. Sepsis and Septic Shock - The #1 ICU Killer

Definitions (Sepsis-3, 2016):

• Sepsis = life-threatening organ dysfunction from a dysregulated host response to infection, defined as an acute SOFA score increase ≥ 2 points
• Septic shock = sepsis + vasopressor requirement to maintain MAP ≥ 65 mmHg + serum lactate > 2 mmol/L despite adequate resuscitation
• qSOFA screen (bedside): RR ≥ 22/min + altered mentation + SBP < 100 mmHg (2 of 3 = suspect sepsis)

The Surviving Sepsis Bundle (management principles):

• Culture blood (and other sites) before antibiotics
• Give empiric broad-spectrum antibiotics within 1 hour
• Draw serum lactate
• Initiate fluid resuscitation

• Crystalloids (balanced) as first-line fluid; consider albumin for large volumes
• Target: 30 mL/kg IV crystalloid in first 3 hours, then reassess with hemodynamic markers
• Serial lactate measurements to guide adequacy of resuscitation
• Target MAP ≥ 65 mmHg

1. Norepinephrine - first-line vasopressor
2. Vasopressin (add when norepinephrine dose reaches 0.25-0.5 mcg/kg/min; do NOT use alone)
3. Epinephrine - add if hypotension persists despite NE + vasopressin
4. Dopamine - only in highly selected patients (generally avoid)
5. Dobutamine - add to NE for persistent low cardiac output states
6. IV corticosteroids (hydrocortisone) - if vasopressor-refractory shock persists

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4. Mechanical Ventilation

Goals:

• Adequate oxygenation and ventilation
• Reduce patient's work of breathing
• Minimize ventilator-induced lung injury (VILI)

Three Oxygenation Strategies (Current Surgical Therapy 14e):

1. Increase FiO2 - but >50% risks oxygen toxicity and absorptive atelectasis
2. Increase mean airway pressure - via PEEP or adjusting I:E ratio
3. Recruitment maneuvers (RM) - transient pressure increases to open collapsed alveoli; maintain with higher PEEP afterward

Key Ventilator Parameters:

VILI Mechanisms to Know:

• Barotrauma - excess pressure
• Volutrauma - excess volume causing overdistension
• Atelectrauma - repeated collapse and reopening of alveoli
• Biotrauma - local mediator release from injured lung

Ventilation Modes:

• Assist Control (AC/CMV): Clinician controls all variables. Each patient effort triggers a full machine-delivered breath at set Vt. Good for sedated/unstable patients. Monitor plateau pressure (can rise in stiff lungs).
• SIMV: Set mandatory rate + patient can take spontaneous breaths between. Used in weaning.
• Pressure Support (PS): Patient-triggered; support augments each breath. Used in weaning and spontaneous breathing trials.
• CPAP/BiPAP (NIPPV): Non-invasive via mask. Preferred in COPD exacerbation (reduces intubation rate and mortality) and mild-moderate hypoxemia.

When to Intubate:

• Worsening acidosis (pH < 7.25) despite NIPPV
• Declining mental status
• Worsening oxygenation
• Inability to protect airway

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5. ARDS - The Classic ICU Respiratory Failure

Berlin Definition:

• Onset: Within 1 week of known insult or new/worsening symptoms
• Chest imaging: Bilateral opacities not fully explained by effusions, collapse, or nodules
• Origin: Not fully explained by cardiac failure or fluid overload
• Oxygenation (on PEEP ≥ 5 cmH2O):
  • Mild: P/F ratio 200-300
  • Moderate: P/F ratio 100-200
  • Severe: P/F ratio < 100

ARDS Management Pearls:

• Lung-protective ventilation: Vt 4-6 mL/kg IBW, plateau pressure ≤ 30 cmH2O (most important intervention)
• Prone positioning ≥ 12 hours/day for moderate-severe ARDS
• Neuromuscular blockade to facilitate proning
• VV-ECMO if failing mechanical ventilation (experienced center)
• Avoid routine PA catheter use
• Keep head of bed at 30-45 degrees (reduces VAP risk)

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6. ICU Monitoring

Bedside Monitoring:

Advanced Monitoring:

• Pulmonary artery catheter (Swan-Ganz): Measures PCWP, CO, SVR - now used selectively (NOT routinely in ARDS)
• Cardiac output (CO) monitoring: Thermodilution, esophageal Doppler, PiCCO
• Lactate: Key marker of tissue hypoperfusion - serial measurements guide resuscitation
• ScvO2 (central venous O2 saturation): < 70% suggests inadequate oxygen delivery

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7. Sedation, Analgesia, and Delirium (SAD)

1. Acute onset/fluctuating mental status
2. Inattention
3. Altered level of consciousness
4. Disorganized thinking Positive if: Features 1+2 AND (3 or 4)

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8. Key ICU Scoring Systems

SOFA Score (Sequential Organ Failure Assessment)

Other Scores to Know:

• APACHE II/III: Predicts ICU mortality (uses age, GCS, vitals, labs, chronic health)
• SAPS II: Simplified Acute Physiology Score
• RIFLE/KDIGO: For AKI staging in ICU

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9. Common ICU Procedures

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10. Daily ICU Checklist (Common in Rounds)

• F - Feeding (enteral preferred; start early)
• A - Analgesia
• S - Sedation (light; daily wake-up trials)
• T - Thromboembolic prophylaxis (LMWH or UFH + compression stockings)
• H - Head of bed elevated 30-45° (VAP prevention)
• U - Ulcer prophylaxis (PPI/H2 blocker in mechanically ventilated patients)
• G - Glucose control (target 140-180 mg/dL)
• S - Spontaneous breathing trial daily
• B - Bowel care
• I - Indwelling catheter removal when no longer needed (prevent CAUTI)
• D - De-escalation of antibiotics (review cultures, narrow therapy)

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11. Common ICU Labs and Targets

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12. VAP (Ventilator-Associated Pneumonia) Prevention

• Head of bed 30-45°
• Daily sedation interruption + SBT
• Oral care with chlorhexidine
• Sub-glottic secretion drainage (where available)
• Minimize sedation/duration of intubation

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Quick Reference Summary Card

SHOCK:  Distributive (↑CO, ↓SVR) → NE first
        Cardiogenic (↓CO, ↑SVR) → fix cause + dobutamine
        Hypovolemic (↓CO, ↑SVR) → fluids/blood
        Obstructive (↓CO, ↑SVR) → fix obstruction (needle, pericardiocentesis)

SEPSIS: Culture → Abx within 1hr → 30mL/kg fluid → NE if MAP <65
        SOFA ≥2 = sepsis | + vasopressor + lactate >2 = septic shock

ARDS:   Vt 4-6 mL/kg IBW | Plateau ≤30 cmH2O | PEEP titrated
        Prone ≥12h/day for moderate-severe

VENT MODES: AC = full control | SIMV = partial | PS = weaning

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1. Who goes to ICU - admission criteria
2. Shock classification - the 4 types with hemodynamic profiles (the most tested concept)
3. Sepsis/Septic Shock - Sepsis-3 definitions, qSOFA, surviving sepsis bundle with vasopressor hierarchy
4. Mechanical Ventilation - modes, parameters, VILI mechanisms
5. ARDS - Berlin definition + lung-protective strategy
6. ICU Monitoring - what each line/monitor measures
7. Sedation & Delirium - ABCDEF bundle, CAM-ICU, RASS
8. Scoring Systems - SOFA, APACHE, qSOFA
9. Common Procedures - indications and key points
10. Daily Rounds Checklist - FAST HUGS BID mnemonic
11. Lab targets - normal vs ICU targets
12. VAP prevention - the bundle