What are the side effects of nitrous oxide (N2O)?

Side Effects of Nitrous Oxide (N₂O)

Nitrous oxide can cause several significant side effects including dizziness, drowsiness, vitamin B12 deficiency leading to neurological damage, and potential asphyxiation risk, with the most common immediate side effect being dizziness affecting up to 39% of users. 1, 2, 3

Common Immediate Side Effects

• Dizziness - Affects up to 39% of users, particularly noted in studies of women in labor 1
• Drowsiness/sedation - Can lead to loss of consciousness if excessive amounts are inhaled 3
• Dissociation and disorientation - Temporary alteration in mental status 4
• Loss of balance - Increasing risk of falls and accidents 4
• Impaired memory and cognition - Temporary effect during use 4
• Headaches - Documented by the American Gastroenterological Association as a "troubling side effect" 2
• Nausea and vomiting - Particularly with prolonged use 2

Serious Side Effects

Neurological Complications

• Vitamin B12 inactivation - Heavy or sustained use inactivates vitamin B12, leading to functional deficiency 4, 5, 6
• Peripheral neuropathy - Initially presenting as numbness in fingers, can progress to more severe neurological damage 4, 7
• Combined spinal cord degeneration - Due to vitamin B12 deficiency from repeated or prolonged use 5, 7

Respiratory Risks

• Hypoxia - Particularly "diffusion hypoxia" when inadequate oxygen is administered during or after use 6
• Asphyxiation - Can cause rapid suffocation by displacing oxygen 3, 4
• Risk of death - Fatal accidents reported due to asphyxia 4

Cardiovascular Effects

• Hypertension - Temporary increase in blood pressure 2
• Arrhythmias - Cardiac rhythm disturbances 2

Other Physiological Effects

• Expansion in air-containing cavities - N₂O diffuses into air spaces faster than nitrogen diffuses out, increasing pressure/volume 6
• Potential frostbite - From direct contact with the compressed gas 3

Contraindications

Nitrous oxide should be avoided in:

• Patients with known emphysema 1
• Patients at risk of hypercapnic respiratory failure 1
• Patients with bowel obstruction, pneumothorax, middle ear and sinus disease 6
• Immunosuppressed patients 6
• Pregnant women, particularly during first two trimesters 6
• Patients requiring multiple general anesthetics 6

Safety Precautions

• Always co-administer with 30-50% oxygen to avoid hypoxia 2
• Use only in well-ventilated areas 3
• Keep away from combustible materials (oxidizer risk) 3
• Monitor with pulse oximetry when used medically 1
• Use protective equipment when handling compressed gas 3

Risk Factors for Adverse Effects

• Duration of exposure - longer exposure increases risk of side effects 2, 7
• Frequency of use - repeated use increases risk of vitamin B12 deficiency 5, 7
• Pre-existing vitamin B12 deficiency or malabsorption 7
• Lack of oxygen supplementation during medical use 1

While nitrous oxide has legitimate medical uses and a rapid onset/offset profile that makes it valuable in certain settings, the potential for serious side effects requires careful consideration, particularly with repeated or recreational use.