ICU Pearls: Ventilation, Shock, and Code Management
Intensive care medicine demands rapid decision-making, understanding of complex pathophysiology, and familiarity with invasive procedures. This section provides essential frameworks for managing the critically ill.
Mechanical Ventilation Essentials
Mechanical ventilation provides respiratory support when natural breathing cannot sustain adequate oxygenation and ventilation. Understanding indications, modes, and management prevents complications.
Indications for Mechanical Ventilation
When to Intubate and Ventilate
- Respiratory failure: PaO2 <60 mmHg on supplemental oxygen; PaCO2 >50 mmHg with acidemia
- Airway protection: Inability to protect airway (altered mental status, absent gag reflex, aspiration risk)
- Anticipated clinical deterioration: Impending respiratory failure; cannot safely monitor airway
- Shock states: Severe sepsis/shock requiring sedation and airway security
- Procedure-related: Elective intubation for anticipated airway compromise
Ventilator Modes
| Mode | Patient Control | Mechanism | Use Case |
|---|---|---|---|
| AC/VC (Assist Control, Volume Control) | Partially controlled | Clinician sets rate and tidal volume; patient can trigger additional breaths | Most common initial mode; ensures minimum minute ventilation |
| AC/PC (Assist Control, Pressure Control) | Partially controlled | Clinician sets rate and inspiratory pressure; volume varies with compliance | Better for stiff lungs (ARDS); prevents excessive tidal volumes |
| SIMV (Synchronized Intermittent Mandatory Ventilation) | Shared control | Set rate delivered; patient can breathe spontaneously between mandatory breaths | Transition mode during weaning |
| PSV (Pressure Support Ventilation) | Patient-controlled | Patient triggers all breaths; each augmented to preset pressure | Spontaneous breathing trial; used during weaning |
| CPAP (Continuous Positive Airway Pressure) | Patient-controlled | Continuous positive pressure throughout respiratory cycle; patient breathes spontaneously | Non-invasive respiratory support |
| Bilevel (BiPAP) | Patient-controlled | Two pressure levels cycle; patient breathes spontaneously | Non-invasive support for hypoxemia/hypercapnia |
Initial Ventilator Settings
ARDSNet Protocol (Most Restrictive/Protective)
- Tidal Volume: 6 mL/kg of ideal body weight (not actual weight)
- Respiratory Rate: 14-18 breaths/min
- FiO2: Start 100%, titrate to maintain oxygen saturation 88-95%
- PEEP: 5-8 cm H₂O initially; titrate based on oxygenation
- Plateau Pressure: Target <30 cm H₂O (check by inspiratory hold at end-inspiration)
- pH Target: Permit permissive hypercapnia (pH 7.15-7.25) to maintain low tidal volumes
Ventilator Alarms and Troubleshooting
| Alarm | Causes | Management |
|---|---|---|
| High Pressure Alarm | Tube obstruction/kinking, patient biting tube, bronchospasm, secretions, pneumothorax, patient-ventilator dyssynchrony | Auscultate; suction; assess tube position (CXR); manual bagging; check breath sounds |
| Low Pressure Alarm | Circuit disconnect, cuff leak, inadequate PEEP | Check all connections; inspect cuff; verify PEEP setting; auscultate |
| Apnea Alarm | Patient not triggering breaths (apnea or oversedation), trigger sensitivity too high | Assess level of consciousness; check trigger setting; manually ventilate if concerned |
Sedation Management
Sedation Goals in Critical Illness
- Target RASS (Richmond Agitation-Sedation Scale): -2 to 0 (light sedation, arousable)
- Daily interruption: Spontaneous awakening trial daily if no contraindications
- Common agents:
- Propofol: Rapid onset/offset; causes hypotension; useful for rapid sequence intubation recovery
- Dexmedetomidine: Maintains cognition; less respiratory depression; preserves airway reflexes
- Benzodiazepines: Lorazepam for intermediate sedation; midazolam for rapid sedation
Mechanical Ventilation Weaning
Weaning begins when the underlying cause of respiratory failure has improved. Systematic assessment prevents premature extubation and unnecessary prolonged ventilation.
Spontaneous Breathing Trial (SBT) Protocol
- Readiness Criteria:
- Oxygenation: FiO2 ≤0.5; PEEP ≤5 cm H₂O; PaO2 ≥60 mmHg
- Ventilation: No fever; acceptable minute ventilation
- Strength: Spontaneous respiratory effort; negative inspiratory force more negative than -20 cm H₂O
- Trial Method: Switch to PSV of 5 cm H₂O or T-piece for 30-120 minutes
- Success Criteria:
- RR <35 breaths/min; no accessory muscle use
- No hypoxemia (SpO2 ≥90-92%)
- No significant tachycardia; minimal anxiety
- RSBI (Rapid Shallow Breathing Index): RR/TV (in liters). RSBI <105 predicts successful extubation
- Extubation: If trial tolerated well; confirm cuff leak (remove tape, suction above cuff, listen for air leak)
ARDS Definition and Management
Acute Respiratory Distress Syndrome (ARDS) represents severe hypoxemic respiratory failure with bilateral opacities not fully explained by cardiac causes.
Berlin Definition of ARDS
- Timing: Acute onset (within 1 week of known clinical insult)
- Bilateral Opacities: Bilateral infiltrates on imaging not fully explained by effusion, atelectasis, or nodules
- Not Cardiogenic: Respiratory failure not fully explained by cardiac failure or fluid overload
- PaO2/FiO2 Ratio (calculated at minimum PEEP 5):
- Mild: 200-300
- Moderate: 100-200
- Severe: <100
- Management: Low tidal volume ventilation (6 mL/kg), plateau pressure <30, permissive hypercapnia, lung recruitment as needed
Shock and Vasopressor Management
Shock represents inadequate tissue perfusion despite adequate circulating volume. Classification guides therapeutics.
Types of Shock: Hemodynamic Profile
| Type | CVP | PCWP | Cardiac Output | SVR | Primary Problem | Examples |
|---|---|---|---|---|---|---|
| Hypovolemic | ↓Low | ↓Low | ↓Low | ↑High | Inadequate intravascular volume | Hemorrhage, burns, dehydration |
| Cardiogenic | ↑High | ↑High | ↓Low | ↑High | Decreased cardiac contractility | MI, acute HF, cardiomyopathy |
| Distributive (Septic) | ↓Low | ↓Low | ↑High (initially) | ↓Low | Peripheral vasodilation, maldistribution | Sepsis, anaphylaxis, neurogenic |
| Obstructive | ↑High | Variable | ↓Low | ↑High | Mechanical obstruction to flow | PE, tension PTX, tamponade |
Vasopressors and Inotropes
| Agent | Dose | Mechanism | Primary Use | Key Consideration |
|---|---|---|---|---|
| Norepinephrine (Levophed) | 0.1-2 mcg/kg/min IV | α1 > β1 activity | 1st line septic shock; maintains BP while increasing CO | Increased tachycardia and ischemic risk at high doses |
| Vasopressin | 0.04 U/min fixed dose IV | V1 receptor activation | Adjunctive agent in septic shock (combined with NE) | Non-titratable; increases gut vasoconstriction |
| Epinephrine | 0.01-0.5 mcg/kg/min IV | α1 + β1 + β2 activity | Anaphylaxis, cardiac arrest, refractory shock | Metabolic side effects (hyperglycemia, lactate); use as add-on to NE |
| Phenylephrine (Neosynephrine) | 0.5-9 mcg/kg/min IV | Pure α1 activity | Neurogenic shock, acute severe hypertension | Pure vasoconstriction; no inotropic support; may reflex bradycardia |
| Dopamine | 2-20 mcg/kg/min IV | Dose-dependent: low=dopaminergic (renal), mid=β1, high=α1 | Historically common; now less favored in sepsis | Increased arrhythmia risk vs NE; avoid if possible |
| Dobutamine | 2-20 mcg/kg/min IV | β1 > β2 activity; inotrope + mild vasodilator | Cardiogenic shock, acute decompensated HF | Causes systemic vasodilation; monitor BP; use with vasopressor |
| Milrinone | 0.125-0.75 mcg/kg/min IV | PDE3 inhibitor; inodilator | Cardiogenic shock/acute HF with elevated SVR | Hypotension common; no catecholamine effect |
Septic Shock Management Algorithm
- Aggressive IV fluid resuscitation (30 mL/kg crystalloid)
- Source control (antibiotics, drainage, removal of source)
- Norepinephrine if hypotension persists (goal MAP ≥65 mmHg)
- Add vasopressin if additional blood pressure support needed
- Low-dose hydrocortisone if refractory shock
Central Line Placement
Central venous catheters provide access for vasopressor infusion, hemodynamic monitoring, and challenging peripheral access.
Indications
- Vasopressor infusion (mandatory for NE, Epi, Dopa)
- Hemodynamic monitoring (CVP measurement, advanced monitoring)
- Total parenteral nutrition (TPN)
- Difficult peripheral access
- Hemodialysis
- Pulmonary artery catheter placement
Common Sites
| Site | Approach | Advantages | Disadvantages |
|---|---|---|---|
| Internal Jugular (IJ) | Percutaneous puncture; anterior or posterior approach | Reliable landmarks; high success; easy to stabilize | Ipsilateral IJ occlusion risk; positioning challenges |
| Subclavian | Percutaneous puncture below clavicle | Best for long-term use; mobility; low infection | Pneumothorax risk; mechanical complications; positional changes |
| Femoral | Percutaneous puncture below inguinal ligament | Easy access; no respiratory complications | Mobility limitations; DVT/infection risk; backup approach |
Complications
Central Line Complications
- Mechanical: Pneumothorax, hemothorax, arterial puncture (especially femoral)
- Infectious: Catheter-related bloodstream infection (CLABSI); follow bundle approach for prevention
- Thrombotic: Vein thrombosis; phlebitis
- Cardiac: Arrhythmia, right atrial perforation (rare with proper placement)
- Air Embolism: Rare; catastrophic if occurs
- Prevention: Sterile technique, ultrasound guidance, CXR confirmation, prompt removal when no longer needed
Placement Confirmation
Always obtain chest X-ray after central line placement. Confirm catheter tip at junction of superior vena cava and right atrium (not in right ventricle or pulmonary artery). Rule out pneumothorax and hemothorax.
Intubation Essentials
Rapid sequence intubation (RSI) provides safe airway management in emergency/critical settings.
Pre-oxygenation
Pre-oxygenate all patients before intubation attempt to maximize oxygen stores and extend apneic period. Use non-rebreather mask, nasal cannula, or bag-mask ventilation for 3 minutes or 8 vital capacity breaths.
RSI Drugs
| Drug | Dose | Mechanism | Advantage | Disadvantage |
|---|---|---|---|---|
| Etomidate | 0.3 mg/kg IV | GABA agonist; sedative hypnotic | Minimal hemodynamic effect; maintains airway reflexes | Single dose suppresses cortisol; adrenal insufficiency concern |
| Ketamine | 1-2 mg/kg IV | NMDA antagonist | Maintains BP, respiration, airway reflexes; analgesia | Tachycardia, increased ICP; emergence reactions |
| Propofol | 1-2.5 mg/kg IV | GABA agonist | Rapid onset/offset; anticonvulsant | Significant hypotension; bradycardia |
| Rocuronium (Paralytic) | 1 mg/kg IV | Non-depolarizing agent | Fast onset (60-90 seconds); intermediate duration | Rapid sequence gives 6-10 minutes paralysis |
| Succinylcholine (Paralytic) | 1-1.5 mg/kg IV | Depolarizing agent | Extremely rapid onset (30-40 seconds); brief duration | Hyperkalemia risk; malignant hyperthermia; rhabdomyolysis |
Intubation Confirmation
After intubation, confirm tube placement through multiple methods: - Primary: End-tidal CO₂ detection (waveform capnography, colorimetric) - Secondary: Bilateral breath sounds; epigastrium auscultation (no air); CXR
Intubation Complications
- Esophageal intubation: False placement; identified by absent ETCO₂, absent breath sounds
- Right mainstem intubation: Common; confirmed by CXR; withdraw tube slightly (19-21 cm at teeth)
- Dental/lip trauma: Poor technique; can require maxillofacial surgery
- Aspiration: Improper positioning; NPO status; RSI with cricoid pressure
Code Management and ACLS
Cardiac arrest demands rapid, coordinated response. Advanced Cardiac Life Support (ACLS) algorithms guide management.
ACLS Algorithms
VF/Pulseless VT
Ventricular Fibrillation / Pulseless Ventricular Tachycardia Algorithm
- Immediate: Start CPR; attach monitor/defibrillator
- Defibrillate: Deliver one shock (360 J biphasic or equivalent)
- Drug Administration (after first shock):
- Epinephrine 1 mg IV/IO push; repeat q3-5min during cardiac arrest
- Alternative: Vasopressin 40 U IV (single dose, not repeated)
- Rhythm Check: After 2 minutes of CPR, recheck rhythm
- Antiarrhythmics (if VF/pVT persists after 3-5 min):
- Amiodarone 300 mg IV, then 150 mg after 3-5 min; or
- Lidocaine 1-1.5 mg/kg IV, then 0.5-0.75 mg/kg q5-10min (max 3 mg/kg)
- Reversible Causes: Identify and treat H's and T's
- Continue CPR with rhythm checks q2min until ROSC or decision to terminate
Pulseless Electrical Activity (PEA) / Asystole
PEA/Asystole Algorithm
- Immediate: Start CPR immediately
- Epinephrine 1 mg IV/IO; repeat q3-5min
- Consider reversible causes: Treat H's and T's aggressively
- No defibrillation: Neither rhythm responds to shock
- Continue CPR until ROSC achieved or termination decision
Reversible Causes of Cardiac Arrest: H's and T's
| H's (Hypoxia, Hypovolemia, Hydrogen ion, Hypo/Hyperkalemia, Hypothermia) | T's (Tension PTX, Tamponade, Toxins, Thrombosis, Trauma) |
|---|---|
| Hypoxia: Verify airway patency; oxygenate/ventilate; consider intubation | Tension pneumothorax: Needle decompression; tube thoracostomy |
| Hypovolemia: IV fluids; massive transfusion protocol if hemorrhagic | Tamponade: Pericardiocentesis; surgical drainage |
| Hydrogen ion (Acidosis): Effective CPR generates CO₂; avoid sodium bicarb unless specific toxins | Toxins: Identify substance; specific antidotes (naloxone for opioids, cyanide kit, etc.) |
| Hypokalemia/Hyperkalemia: Check serum K+; treat arrhythmias (calcium for K+>7) | Thrombosis (PE): Consider thrombolytics or extracorporeal CPR |
| Hypothermia: Slow, controlled rewarming; extracorporeal techniques for severe cases | Trauma: Ongoing hemorrhage control; consider REBOA, resuscitative hysterotomy |
Post-ROSC Management
After return of spontaneous circulation (ROSC):
Post-Resuscitation Care
- Targeted Temperature Management: Induce therapeutic hypothermia (32-36°C) or at minimum avoid fever
- Coronary Angiography: Obtain 12-lead EKG immediately; cardiac catheterization for STEMI
- Oxygenation/Ventilation: Avoid hyperoxia; target SpO₂ 90-99%; avoid hypocapnia
- Hemodynamics: Vasopressor support, inotropes as needed; maintain MAP ≥65 mmHg
- Prognostication: Neurologic assessment at 72 hours; consider EEG; avoid early withdrawal of care
- Rehabilitation: ICU management; ICU delirium management; early mobility when feasible
Procedure Essentials
Thoracentesis
Fluid drainage from pleural space relieves dyspnea and allows diagnostic analysis. Contraindications include uncontrolled bleeding, small volume (<2 cm), and patient refusal.
Technique: Ultrasound guidance preferred. Insert needle at top of rib (avoid neurovascular bundle running below rib); aspirate fluid for analysis and drain therapeutically.
Paracentesis
Removes ascitic fluid diagnostically or therapeutically. Risk of spontaneous bacterial peritonitis; prophylactic antibiotics if albumin <1.5 or bilirubin >3 in cirrhosis.
Technique: Ultrasound guidance. Local anesthesia. Insert below level of umbilicus to avoid bladder; withdraw fluid slowly.
Lumbar Puncture
Diagnostic testing for meningitis, encephalitis, subarachnoid hemorrhage. Contraindicated in papilledema (risk of herniation). Obtain CT before LP if any mass effect concern.
Technique: Lateral decubitus position; palpate iliac crests (L4 interspace); sterile technique; withdraw CSF and measure opening pressure.
Complications of Procedures
- Thoracentesis: Pneumothorax, hemothorax, organ perforation, infection
- Paracentesis: Peritonitis, bowel perforation, hemorrhage, hepatic/renal failure
- Lumbar Puncture: Post-LP headache (positional), meningitis, spinal cord injury