Which labs and investigations should be obtained immediately after intubation?

Post-Intubation Labs and Tests

Immediately after intubation, confirm tube placement with continuous waveform capnography, obtain a chest X-ray to verify tube position in the mid-trachea, and collect arterial blood gas, complete blood count, electrolytes, renal function tests, and blood cultures if infection is suspected.

Immediate Confirmation of Tube Placement

The most critical immediate assessment is confirming correct endotracheal tube position using multiple methods:

• Continuous waveform capnography is mandatory to confirm tracheal intubation in all patients with a perfusing rhythm 1, 2
• Observe bilateral chest wall expansion with ventilation, as auscultation may be unreliable, especially when wearing PPE 2
• Pulse oximetry should be monitored, though saturation may not decline for up to 3 minutes after hyperoxygenation even without effective ventilation 1
• Chest X-ray must be obtained to verify the tube is not in a bronchus and to confirm proper position in the mid-trachea 1, 2
• Lung ultrasound may be used if there is doubt about bilateral lung ventilation 2

Clinical examination alone (misting, auscultation) has unacceptably high false positive rates and should never be relied upon as the sole confirmation method 3.

Essential Laboratory Tests

Arterial Blood Gas

• Obtain arterial blood gas to assess oxygenation, ventilation (PaCO2), and acid-base status 4, 5
• This is particularly important for patients requiring mechanical ventilation to guide ventilator settings 4
• Helps identify metabolic or respiratory acidosis and guides oxygen therapy 4

Complete Blood Count and Chemistry

• Complete blood count (CBC) to assess for leukocytosis/leukopenia suggesting infection 4, 5
• Serum electrolytes including sodium, potassium, chloride, bicarbonate 4, 5
• Renal function tests (creatinine, eGFR) - particularly important if shock or renal dysfunction is present 4, 6
• Glucose measurement, as hyperglycemia requires management 5
• Coagulation studies (INR, aPTT) if not already obtained 5
• Troponin to assess for cardiac injury 5

Blood Cultures

• Two sets of blood cultures should be obtained in patients with suspected ventilator-associated pneumonia or sepsis 4, 7
• Blood cultures help identify bacteremia and guide antibiotic therapy 4

Respiratory Samples

• Collect deep tracheal sample using closed suction for microbiological testing if infection is suspected 2, 4
• This is particularly important for COVID-19 or other respiratory pathogen testing, as upper airway samples may be false negatives 2
• Samples should be obtained before initiating or changing antibiotics 4
• Send for direct examination and culture to guide antibiotic selection 4, 7

Additional Monitoring and Tests

Cardiovascular Assessment

• Electrocardiogram (ECG) should be completed to assess for arrhythmias or cardiac ischemia 5
• Heart rate, blood pressure, and rhythm should be monitored continuously 6, 5

Chest Imaging

• Chest X-ray serves multiple purposes beyond tube position verification 4, 5:
  • Defines severity of pneumonia (multilobar involvement)
  • Identifies complications such as effusions or cavitation
  • Assesses for pulmonary edema or other pulmonary conditions
  • Should be obtained when acute heart disease or pulmonary disease is evident

Fluid Balance Monitoring

• Bladder catheterization may be required for careful monitoring of urine output and fluid balance 6
• Serum electrolytes and renal function should be checked regularly in the first 24 hours if the patient is in shock or has significant renal dysfunction 6

Post-Intubation Documentation and Procedures

• Record the depth of endotracheal tube insertion prominently once correct position is established 2
• Pass a nasogastric tube after intubation is complete and ventilation established to minimize need for later interventions 2
• Document a visual record of tracheal intubation that should be prominently visible in the patient's room 2

Common Pitfalls

If an intubated patient's condition deteriorates, remember the DOPE mnemonic 1:

• Displacement of the tube
• Obstruction of the tube
• Pneumothorax
• Equipment failure

Reconfirm tube position with clinical assessment and confirmatory devices during transport and each time the patient is moved 1.