II. Indications
-
Procedural Sedation (esp. pediatrics)
- Low intensity procedures (e.g. Lumbar Puncture, Laceration Repair, minor Fracture reduction)
- Moderate analgesia
- Best used in combination with Local Anesthesia (e.g. local infiltration, Hematoma Block)
III. Contraindications (related to gas expansion risks)
- Pneumothorax
- Pulmonary Blebs
- Bowel Obstruction
- Air Embolism
- Pneumocephalus
- Recent eye surgery
IV. History
- First used for Anesthesia in U.S. in 1845
- Used in a majority of pediatric dental offices
V. Mechanism
- Nitrous Oxide is a colorless, tasteless gas
- Effects Opioid spinal modulators, GABA Receptors, NMDA receptors
- Also releases endorphins
VI. Pharmacokinetics
- Rapidly absorbed in lung and cleared from lung
- Excreted unchanged (not metabolized) primarily from lung within one minute of inhalation
- Poorly soluble in blood
- Onset: 2-3 minutes
- Duration: 3-5 minutes
- Rapidly off-loads with oxygen (often given for 5 minutes after procedure)
- Effects
- Mild anxiolysis: <50% Nitrous Oxide
- Analgesia: 50-70% Nitrous Oxide
- Amnesia
- Minimum Alveolar Concentration (MAC): 105.0%
- Nitrous Oxide MAC is much higher than other inhalation Anesthetics (e.g. Isoflurane)
- With a high MAC, Nitrous Oxide is a poor general Anesthetics alone, but offers good lower level sedation
VII. Adverse Effects
- Light Headedness
- Somnolence
- Confusion
- Paresthesias
- Nausea or Vomiting (1-2% of cases)
- Inadequate sedation (1.2% of cases)
- Airway obstruction or Hypoxia (0.25% of cases)
- More common with concurrent Opioids or Benzodiazepines
VIII. Safety
- Among the safest sedation agents with proper use and monitoring (ACEP, 1984)
- Airway obstruction or Hypoxia is rare (0.25% of cases)
- Has not been associated with apnea
- Hemodynamically stable without effects on Heart Rate or Blood Pressure
- Very rare mortality (case reports)
- No Allergic Reactions reported
- No pregnancy data, and not recommended in first or second trimester
- Considered likely safe in third trimester
- No delay in Lactation
- Not considered Procedural Sedation unless combined with other agents (e.g. Fentanyl, Midazolam)
- Does not require cardiac monitoring, End-Tidal CO2 or Intravenous Access
- Pulse Oximetry is typically adequate monitoring for Nitrous Oxide
IX. Preparation
-
General equipment
- Oxygen supply
- Wall suction
- Airway equipment
- Educate patient on use of mask
- Patient instructed to take deeper breaths if feels more pain
- Nitrous Oxide delivery device
- Full Face Mask or Nasal mask (may be scented)
- Delivery mix: 50:50 to 70:30 mix of Nitrous Oxide and oxygen
- Preferred mix appears to be 70:30
- Typically portable unit with Nitrous Oxide tanks, and attached to wall oxygen
- Device should have audible alarms, flow control and scavenger functionality (suction)
- Scavenger functionality prevents bystander exposure to Nitrous Oxide
- Does not require a medical gas vacuum system
X. Dosing
- Goal Nitrous Oxide effects (expect onset within 2-3 min of starting Nitrous Oxide)
- Apathy
- Somnolence
- Still responds to verbal stimuli
- Start with total liter flow estimation
- Child: 4-5 L/min
- Adult: 6-7 L/min
- Watch reservoir bag while on oxygen only, and goal inflation is 2/3 full (not collapsed and not full)
- Initiate Nitrous Oxide
- Start 10-15% Nitrous Oxide and increase every couple of minutes to effect (see above)
- Patient asked to breath normally through their nose and to relax
- Prepare patient that they may have arms and legs
- Titrate Nitrous Oxide
- Self-titration method
- Patient holds mask to their own face
- As sedation increases, the mask drops away
- When they awaken again, they replace the mask to once again increase sedation
XI. References
- Acker, Koval and Leeper (2017) Crit Dec Emerg Med 31(4): 3-13
- Cordle (2016) Nitrous Oxide Lecture, ACEP PEM Conference, attended 3/9/2016
- Lapietra and Swaminathan in Swadron (2022) EM:Rap 22(3): 6-8
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Definition (NCI) | A naturally occurring gas that is colorless and non flammable. It can be manufactured and used for a variety of things such as a pharmacologic agent to produce anesthesia, a food additive as a propellant, and an additive to fuels to increase available oxygen in combustion. |
Definition (CSP) | "laughing gas"; N2O. |
Definition (MSH) | Nitrogen oxide (N2O). A colorless, odorless gas that is used as an anesthetic and analgesic. High concentrations cause a narcotic effect and may replace oxygen, causing death by asphyxia. It is also used as a food aerosol in the preparation of whipping cream. |
Concepts | Biologically Active Substance (T123) , Pharmacologic Substance (T121) , Inorganic Chemical (T197) |
MSH | D009609 |
SnomedCT | 388185005, 273959001, 111132001 |
LNC | LP100617-2, MTHU035878 |
English | Oxide, Nitrous, Laughing Gas, Gas, Laughing, nitrous oxide, Nitrogen oxide (N2O), nitrous oxide (medication), NITROUS OXIDE GAS, NITROUS OXIDE @ @ GAS, Dinitrogen Monoxide, Nitrogen Protoxide, Nitrous Oxide [Chemical/Ingredient], NITROUS OXIDE, nitrous oxide gas, laughing gas, Nitrous oxide, Nitrous oxide gas, Dinitrogen monoxide, Laughing gas, N2O - Nitrous oxide, Nitrous oxide (product), Nitrous oxide (substance), Nitrous Oxide |
French | N2O, Oxyde nitreux, Monoxyde de diazote, Gaz hilarant, Protoxyde d'azote |
Swedish | Lustgas |
Czech | oxid dusný |
Finnish | Typpioksiduuli |
Russian | AZOTA III OKSID, AZOTISTYI ANGIDRID, VESELIASHCHII GAZ, AZOTA ZAKIS', ZAKIS' AZOTA, АЗОТА III ОКСИД, АЗОТА ЗАКИСЬ, АЗОТИСТЫЙ АНГИДРИД, ВЕСЕЛЯЩИЙ ГАЗ, ЗАКИСЬ АЗОТА |
Italian | Gas esilarante, Ossido nitroso |
Polish | Podtlenek azotu |
Japanese | 笑気, 亜酸化窒素, 一酸化二窒素, 酸化二窒素 |
Norwegian | Lystgass, Dinitrogenoksid, Lattergass |
Spanish | óxido nitroso (producto), óxido nitroso (sustancia), óxido nitroso, Óxido Nitroso |
German | Distickstoffoxid |
Portuguese | Óxido Nitroso |