CO2 narcosis

Background

• Increased CO2 in the blood leading to depressed mental status
• Most commonly seen in acute exacerbations of obstructive pulmonary diseases (e.g. COPD, asthma)
• Can also be seen in SCUBA divers

Clinical Features

• Headache
• Confusion
• Lethargy
• Propensity for arrhythmias
• Seizure
• Coma/death

Differential Diagnosis

Altered mental status

Diffuse brain dysfunction

• Hypoxic encephalopathy
• Acute toxic-metabolic encephalopathy (Delirium)
  • Hypoglycemia
  • Hyperosmolar state (e.g., hyperglycemia)
  • Electrolyte Abnormalities (hypernatremia or hyponatremia, hypercalcemia)
  • Organ system failure
  • Hepatic Encephalopathy
  • Uremia/Renal Failure
  • Endocrine (Addison's disease, Cushing syndrome, hypothyroidism, myxedema coma, thyroid storm)
  • Hypoxia
  • CO2 narcosis
• Hypertensive Encephalopathy
• Toxins
• TTP / Thrombotic thrombocytopenic purpura
• Alcohol withdrawal
• Drug reactions (NMS, Serotonin Syndrome)
• Environmental causes
  • Hypothermia
  • Hyperthermia
• Deficiency state
  • Wernicke encephalopathy
  • Subacute Combined Degeneration of Spinal Cord (B12 deficiency)
  • Vitamin D Deficiency
  • Zinc Deficiency
• Sepsis
• Osmotic demyelination syndrome (central pontine myelinolysis)
• Limbic encephalitis

Primary CNS disease or trauma

• Direct CNS trauma
  • Diffuse axonal injury
  • Subdural/epidural hematoma
• Vascular disease
  • Intraparenchymal hemorrhage
• SAH
• Stroke
  • Hemispheric, brainstem
• CNS infections
  • Encephalitis
  • Anti-NMDA receptor encephalitis
  • Meningitis
• Neoplasms
  • Paraneoplastic Limbic encephalitis
  • Malignant Meningitis
  • Pancreatic Insulinoma
• Seizures
  • Nonconvulsive status epilepticus
  • Postictal state
• Dementia
  • Alzheimer's
  • Lewy Body Dementia
  • Frontotemporal Dementia

Psychiatric

• Acute psychosis
• Excited delirium
• Malingering

Evaluation

• VBG (ABG not required to make this diagnosis)

Management

• Hyperventilation with either NIPPV or intubation/mechanical ventilation depending on severity and patient's mental status

Disposition

• Admission to a monitored setting

See Also

• Altered mental status

Authors:

Claire, Neil Young, Nicole Zadzilka, Daniel Ostermayer, Ross Donaldson