Increased<unk>  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
CO2 narcosis
Hypoxic encephalopathy
Nitrogen narcosis
Acute toxic-metabolic encephalopathy 
Malignant hyperthermia
Hypoglycemia
Carbon monoxide toxicity
Hyperosmolar state 