Cardiac Arrest Management

Diagnostic Approaches

Arterial Blood Gas (ABG) results alone may be misleading during cardiac arrest, and should be interpreted with caution 1, 2
Normal arterial blood gas values are:
Component Normal Range
pH 7.35-7.45
PaCO2 35-45 mmHg (4.7-6.0 kPa)
PaO2 80-100 mmHg (10.6-13.3 kPa)
HCO3- 22-26 mEq/L
Oxygen Saturation 95-100%
Blood gas analyzers in ICUs should perform to acceptable international standards (±6-10% accuracy), as recommended by the Critical Care society 6

Arterial blood is the preferred sample type for critically ill patients with indwelling arterial catheters, as recommended by the Critical Care society 6
Venous blood is an acceptable alternative when arterial sampling is not available, according to the Critical Care society 6
Capillary samples are only suitable for patients who do not require invasive vascular monitoring and should be avoided in patients on vasopressor therapy, with shock/hypotension, severe peripheral edema, or poor peripheral perfusion, as recommended by the Critical Care society 6 and the Critical Care Medicine society 7
Closed sampling systems are preferred for arterial lines to minimize contamination and blood wastage, as recommended by the Anaesthesia society 8
Open sampling systems require discarding at least 3-5 times the dead space volume before sampling, according to the Anaesthesia society 8
Sodium chloride 0.9% (with or without heparin) should be used for arterial line infusion and flushing, as recommended by the Anaesthesia society 8
Glucose-containing solutions should not be used as arterial line flush fluids to avoid sample contamination, as warned by the Anaesthesia society 8

Arterial blood gas (ABG) analysis is the gold standard for oxygenation assessment, particularly in patients with severe hypoxemia (SpO2 <90%) or those requiring ventilatory support, as recommended by the American College of Critical Care Medicine and the European Heart Association 7, 9, 10
Titrate oxygen therapy based on target saturation, with a target SpO₂ of 94-98% for most patients, and 88-92% for COPD patients or those at risk of hypercapnia, as recommended by the American Thoracic Society 3
Evaluate oxygenation by assessing PaO₂ levels, with significant hypoxemia defined as PaO₂ < 60 mmHg, and calculate A-a gradient if needed, as recommended by the American Thoracic Society 11

Evaluate pH to determine acidemia (pH < 7.35) or alkalemia (pH > 7.45), and assess primary disorder, such as respiratory acidosis (pH ↓, PaCO₂ ↑) or metabolic acidosis (pH ↓, HCO₃⁻ ↓), as recommended by the American Heart Association 12
Respiratory acidosis is characterized by a PaCO2 > 45 mmHg, while respiratory alkalosis is characterized by a PaCO2 < 35 mmHg, and metabolic acidosis is characterized by an HCO3- < 22 mEq/L, while metabolic alkalosis is characterized by an HCO3- > 26 mEq/L 12
Maintaining normal acid-base balance is crucial to prevent increased ICP, characterized by pH < 7.35 and PaCO2 > 45 mmHg, in patients with neurological conditions, according to the American Heart Association 13

ICP monitoring is recommended in patients with severe neurological injury and acidosis, and recognizing early signs of increased ICP is crucial, as suggested by the American Heart Association 14, 15, 16
Hyperventilation (reducing PaCO2) is recommended as a temporary measure to lower ICP in emergency situations, but cautioning that prolonged hyperventilation (>6 hours) can cause rebound ICP elevation, as recommended by the American Academy of Neurology 13, 14

The American Society of Anesthesiologists recommends that sodium bicarbonate should be limited to severe acidosis (pH < 7.1, base deficit < -10) or special circumstances like hyperkalemia or tricyclic antidepressant overdose 1
In cardiac arrest, ABG may not reflect tissue acidosis accurately; judicious use of buffers is recommended only for severe acidosis (pH < 7.1, base excess < -10) 2
Venous gasometry is indicated for monitoring metabolic disorders, such as diabetic ketoacidosis or metabolic acidosis due to renal failure, and for following patients with known acid-base disturbances, as suggested by the American Thoracic Society and the Thorax journal 3