Objectives: Nitrous oxide sedation in pediatrics Review the history and evolution Discuss the physical, chemical, and pharmacokinetic/pharmacodynamic properties Explain the regulation/storage Identify appropriate use of equipment Review the clinical indications and contraindications Discuss patient assessment, administration/titration and recovery Identify potential biohazards for health personnel
History of Nitrous oxide In 1844, Dr. Gardner Colton hosted an exhibition to demonstrate the exhilarating effects of inhaling N 2 O. A volunteer from the audience began feeling the effects of the gas and was euphorically jumping around the stage. He struck his leg on a bench causing a deep, bloody laceration, but he was unaware of the extent of the injury and denied feeling any pain.
History of Nitrous oxide Horace Wells, a dentist in the audience, was intrigued by the non-responsiveness to pain. He asked if a tooth could be removed under the influence of N 2 O. The next day, he breathed the gas himself and had a colleague extract one of his teeth. He described it as “the greatest discovery ever made” and “a new era in tooth pulling”. He continued, with great success, using N 2 O on several of his patients who required tooth extractions and also as anesthesia for surgeons in the area.
History of Nitrous oxide N 2 O use temporarily diminished with the popularity of local anesthesia and the discovery of other anesthetic gases, some more potent. N 2 O remained useful in providing rapid induction of the more potent agents. N 2 O has been most popular in the field of dentistry but has also been used in emergency medicine, podiatry, labor and delivery, radiology, and as a sedation treatment for procedures not requiring general anesthesia. It has remained in continuous use longer than any other drug and has an impeccable safety record.
N 2 O/O 2 sedation It is necessary to use oxygen with nitrous oxide so that the blood remains appropriately oxygenated. A mixture of 20% nitrous oxide and 80% oxygen has the same analgesic equipotence as 15 mg of morphine.
General Information-N 2 O/O 2 sedation Analgesia -pain control Anxiolysis -sedative effects Amnesic – diminishes recall of severity of pain or duration of procedure Onset of action – clinical effects begin within 30 seconds, peak effects within 5 minutes Titration – very easily allows for the exact amount of the drug necessary to be delivered to each individual patient Recovery – rapid and complete. The effects dissipate right away when the patient stops breathing the gas. Elimination – 99% eliminated from the body within 5-10 minutes after discontinuation Nitrous oxide is the weakest of all inhalation general anesthetics
Physical/Chemical Properties Physical and chemical properties of N 2 O Nitrous oxide is a sweet smelling, colorless gas At room temperature, N 2 O is a gas. When compressed into a cylinder, it becomes a liquid. The substance itself is not flammable, but will support combustion. Exposure to a combustible substance or flame will cause the gas to decompose. If the discomposure occurs at a high temperature or pressure, an explosion will occur. N 2 O is an oxidizing gas. Therefore, the use of hydrocarbon compounds, such as lubricants, grease or oil, should be avoided on any N 2 O storage, dispensing or distribution equipment to prevent the risk of fire or explosion.
Physical/Chemical Properties Physical and chemical properties of Oxygen O 2 is odorless, colorless, and tasteless. O 2 is a gas when compressed in cylinders. O 2 is highly reactive and combines with most elements. O 2, like N 2 O, is not itself flammable but supports combustion when it contacts a combustible material such as oils, grease, or flammable materials. The oxygen molecule does not separate from the nitrogen molecule in N 2 O. Therefore, it cannot be considered a source of oxygen.
Pharmacokinetics of Nitrous Oxide (uptake, distribution, metabolism, and elimination) N 2 O acts on the body by moving across partial pressure gradients from a higher to a lower pressure gradient. N 2 O crosses the alveolar membrane easily. It is relatively insoluble, meaning it remains unchanged in the blood and does not combine with any blood elements. This limits uptake in the body and causes equilibrium to be achieved quickly. Clinical effects are seen within 3-5 minutes. Because of the inability of tissues to hold N 2 O, it is not stored in the body to any extent. Elimination is rapid and not impeded.
Cardiovascular system No negative effects No change in blood flow to major organs Positive effect on myocardial ischemia by providing supplemental O 2 Decrease in blood pressure due to relaxation. N 2 O does not directly effect the myocardium or voluntary skeletal muscle. Decrease in heart rate as anxiety is lowered. N 2 O has minimal effect on heart rate. Pharmacodynamics-Nitrous oxide interactions with the body
N 2 O Interactions with the body Respiratory System Expansive nature of N 2 O/O 2 increases the size of bullae in CF patients, and the size of a pneumothorax. Any condition that compromises air exchange through the nose (URI, congestion, common colds) may cause insufficient amounts of N 2 O/O 2 to enter the respiratory system causing incomplete air exchange at the alveolar level and inadequate sedation. The drying effect of N 2 O/O 2 may create mucous plugs in patients with mild URI; thus, preventing adequate passage of N 2 O/O 2 and inadequate sedation. Patients may feel increased sinus pressure as N 2 O/O 2 expands and fills those air spaces. Patients susceptible to hypoxia due to airway resistance, impaired function, or movement (emphysema, chronic bronchitis) have an increased risk for respiratory depression and should receive medical consultation before undergoing any type of sedation. Regurgitation and aspiration are a risk if pharyngeal-laryngeal reflexes are lost. This can be avoided by using the appropriate titration technique so as to avoid over-sedation and an unconscious state.
N 2 O Interactions with the body Central Nervous System (CNS) Depresses the CNS N 2 O affects the frequency and voltage changes on electroencephalograms (EEGs). Increases intracranial pressure in cases of pneumoencephalography. Do not use N 2 O/O 2 for 3 weeks following this procedure. Numbness and weakness of extremities and ataxic gait suggest injury to the nervous system due to chronic exposure to N 2 O.
N 2 O Interactions with the body Hematopoietic system Megaloblastic bone marrow changes in patients exposed to high concentrations for extended periods of time N 2 O is implicated in the interference of the vitamin B 12 dependent enzyme methionine synthase – necessary for DNA synthesis and erythrocyte production. No negative effects when used for patients with conditions of red blood cell deficiency, impairment, and/or destruction as long as the approved technique is followed which calls for delivery of supplemental oxygen.
N 2 O Interactions with the body Endocrine system No negative effects Hepatic system Not metabolized in the liver No negative effects Gastrointestinal system N 2 O diffuses into the air spaces of the peritoneum and intestines causing increased expansion, pressure, and discomfort.
N 2 O Interactions with the body Genitourinary system No negative effects Reproductive system N 2 O crosses the placental barrier Although research confirms the safety of N 2 O/O 2 use with pregnant women, treatment considerations are important during the first trimester (when organogenesis occurs) and the last trimester (when low O2 tension levels are possible). Avoid administration during the first trimester. Neuromuscular system Indirectly relaxes skeletal muscle Muscle rigidity (secondary to anxiety) with high concentrations
N 2 O Interactions with the body Cancer N 2 O does not combine with any formed blood elements Does not affect metastatic cells Increases incidence of pulmonary fibrosis and other pulmonary diseases in patients receiving bleomycin sulfate (used typically for treatment of lymphomas, testicular tumors, and squamous cell carcinomas). Allergies No reported allergies in more than 160 years Use latex free products (rubber nasal hoods have caused contact dermatitis in latex sensitive patients). Malignant hyperthermia Not considered a trigger for susceptible patients (can be administered safely).
N 2 O Interactions with the body Nutritional disorders No effects on any nutritional conditions Mind-altering conditions N 2 O produces euphoria. Patients/families should be able to understand the procedure and its effects so the associated signs and symptoms are not perceived negatively. Increased CNS depression with concomitant use of drugs, alcohol, barbiturates, or sleep aids. Be alert for synergistic effects with psychotropic or antidepressant medications. May trigger or exacerbate unwanted episodes from addictions or mental illness. Physical agitation and acts of aggression in severely phobic individuals.
Regulation and control of Nitrous Oxide The N 2 O industry is regulated by The Food and Drug Administration (FDA). They set forth and monitor compliance to both good manufacturing practices and quality system requirements. N2O is considered a hazardous material because of the pressurization. Its packaging and transport is overseen by The U.S. Department of Transportation (DOT). Sales and security of N2O is regulated by the Compressed Gas Association (CGA) and the Gases and Welding Distributors Association (GAWDA).
Regulation and control of Nitrous Oxide Nitrous oxide Cylinders A full N 2 O cylinder contains approximately 95% liquid and 5% vapor –Liquid N 2 O in the tank is vaporized by the ambient room air temperature outside the tank as the gas is used –The tank becomes cool to touch and frost may be seen on the tank surface during prolonged and continuous use. Pressure gauge on the cylinder is not proportional to the actual amount of gas in the cylinder. The gauge will show a pressure decrease when the tank contains approximately 20% N 2 O. Oxygen cylinders A full O 2 cylinder contains 100% gas (vapor) The pressure gauge will accurately reflect the amount of gas present in the cylinder at all times until it is empty. The N 2 O/O 2 sedation machine is driven by O 2 flow. If the O2 tank empties, the N 2 O flow stops and the sedation is interrupted. It is important to have extra O 2 cylinders available during sedations to prevent interruption.
Storage of equipment Nitrous oxide equipment must be stored in a secure, locked space which may vary depending on the unit or department. Regulation of use occurs through the medication pyxis.
Nitrous Oxide equipment Equipment should be current, accurate and include a scavenging system. This ensures minimal occupational exposure for staff. Vacuum and ventilation exhaust must be vented to the outside. Inspect pressure connections for absence of leaks. Inspect the conducting tubing and reservoir bag to the unit if not already in place. Connect the conducting tubing and reservoir bag to the unit if not already in place. Make sure to have replacement equipment and cylinders on hand. Disinfect re-usable equipment after each patient use. Any part of the tubing that is not corrugated can be sterilized but is not necessary. Surface disinfection is adequate.
Clinical indications of N 2 O/O 2 sedation Examples of procedures N2O/O2 sedation could potentially be used for here at Dayton Children’s: Burn / wound care Closed reductions Abcess drainage CVL / PICC placements G-tube changes Injections – IM / IV / Port access Lumbar punctures Minor surgical procedures NG tube / pH probe placements Pelvic / perineal exams Splinting Sutures Urethral catheterizations Venipuncture Note: N 2 0/O 2 sedation is not recommended for procedures longer than one hour.
Contraindications for use of N2O/O2 sedation N 2 O rapidly replaces N 2 in air filled spaces in the body causing expansion of those spaces; therefore, N 2 O/O 2 should not be used in patients with: –Pneumothorax –Middle ear occlusion/surgery –Recent (within 3 weeks) craniotomy/pneumoencephalography –Increased intracranial pressure –Intraocular injury/surgery (injected gas may last up to 10 weeks) –Maxillofacial injuries –Intestinal obstruction –Cystic fibrosis Current upper respiratory tract infection Chronic obstructive pulmonary diseases Vitamin B 12 deficiency Psychological impairment Phobic individuals Bleomycin therapy Current psychotropic drug use Current or recovering drug use/addiction First trimester of pregnancy Any facial injury which would prevent use of the mask Note: Asthma is not a contraindication
Preparation for Nitrous oxide administration --Staff qualifications Persons administering N 2 O/O 2 sedation must complete the Nitrous oxide competency course according to the Nitrous oxide policy. --Emergency equipment Emergency equipment must be readily available to include: –Oxygen –Positive pressure ventilation system –Suction –Advanced airway equipment –Resuscitation medications –Automated external defibrillator
Patient Assessment Patient history Abnormalities of the major organ systems Previous adverse experience with sedation or analgesia Drug allergies Current medications and potential drug interactions Time and nature of last oral intake History of tobacco, alcohol, or substance abuse Pain and anxiety Assessment of patient risk Classify the patient’s physical status using the ASA Physical Status Classification System
Patient assessment Pre-procedure evaluation Vital signs –Blood pressure, pulse, respiration, oxygen saturation, and pain score Auscultation of the heart and lungs Evaluation of the airway –Previous problems with anesthesia or sedation? –Sleep problems? –Chromosomal abnormalities? –Determination of size and limitations of the head, neck, and mouth –Variations in occlusion and teeth
Patient Assessment Patient preparation It is not necessary to fast prior to the administration of nitrous oxide/oxygen sedation. When conditions warrant, it is recommended that patients do not eat fried, fatty, or greasy food just prior to sedation. A light meal that includes carbohydrates is appropriate if eaten an hour or so prior to the procedure. Patient monitoring Level of consciousness – patient response to verbal stimulation Ventilatory function – auscultate and/or observe the frequency and depth of respirations Oxygenation – pulse oximetry can uncover early hypoxemia
Administration of N 2 O/O 2 Titration is an important skill in administering nitrous oxide. Titration is a method of administering a drug in incremental amounts until a desired endpoint is reached. If done properly, the patient does not receive more of the drug than is necessary. For pediatric patients, titration in 10% intervals is recommended.
Administration of N 2 O/O 2 Advantages of N 2 O titration Only the amount of drug required by the patient is given. Allows for individual biovariability Uncovers idiosyncratic reactions early Minimizes negative experiences with over sedation
Administration of N 2 O/O 2 Adjusting levels appropriately A common mistake is to deliver a preset percentage of N 2 O to a patient. This can result in either under or over sedation. Most of the negative patient experiences occur because of over-sedation due to operator error. Because of individual biovariability, patients will require different levels of N 2 O on different days and for different procedures. the percentage of N 2 O a patient received at a previous visit is not relevant to the current appointment. N 2 O can be increased or decreased, depending on the intensity of the procedure. Begin with 100% O 2, then titrate to the desired percentage of N 2 O. This should generally be between 20-50%. Levels between 50-70% are considered moderate sedation, and monitoring parameters must be followed accordingly. Patients should be closely monitored. The onset of clinical effects is rapid, and signs and symptoms of sedation could be missed. Once signs and symptoms of sedation appear, monitor patient responses and allow time for doses to reach their peak effect. As the procedure nears completion, N 2 O should be discontinued gradually, and replaced with 100% O 2. A minimum of 5 minutes of post oxygenation is required.
Administration of N2O/O2 Fundamental principles for appropriate administration Be enthusiastic and confident that the experience will be positive. This attitude will transfer to the patient. Be knowledgeable about what N 2 O can and cannot accomplish. Informed consent must be obtained prior to administration. Physician does not have to be present when administering nitrous oxide. Do not adopt a fixed dose philosophy. The amount of N 2 O required by a patient on any given day or time varies. The procedure begins and ends with 100% pure oxygen. Do not leave the patient alone. Constant monitoring must be done by a professional trained in N 2 O/O 2 sedation. Document accurately. Maintain patient in a comfortable position. Maintain open communication with the patient. The use of guided imagery is an essential component.
Successful nitrous sedation Appropriate minimal sedation Patient is comfortable and relaxed. (Look for shoulders to drop, legs uncrossing, arms laying looser, deeper respirations) Patient acknowledges reduced fear and anxiety. The patient’s mood may be categorized as happy, pleasant, ambivalent Patient is aware of surroundings. Patient responds to directions and conversation. Eyes become less active and glazed look appears. Patient may experience: –Tingling in extremities and/or near mouth –Heaviness in leg and arms –Body warmth –Light feeling –Vasodilatation in face and neck –Circumoral numbness
Potential side effects of nitrous oxide Detachment / disassociation from environment Dreaming, hallucinating, or sexual fantasizing Out-of-body experiences Floating and/or flying Physical body movements may become restless, combative, sluggish Inability to move, communicate, or keep mouth open –Words may be slurred or repeated; incoherent sentences Humming or vibrating sounds that progressively worsen Fits of uncontrolled laughter Patient may experience: –Drowsiness –Dizziness / Light headedness / spinning sensations –Diaphoresis –Nausea / vomiting –Fixed eyes –Uncomfortable body warmth –Unconsciousness
Sedation Recovery Immediately post procedure, slowly decrease the nitrous, and begin administration of 100% O2 for a minimum of 5 minutes. This oxygenation period can be extended until both the patient and caregiver are satisfied that adequate recovery has been achieved. Just as Nitrous oxide provides a rapid onset of sedation, a correlated rapid emergence from sedation will occur as well. Keep in mind that each individual is different and recovery times may vary. Mental and psychomotor impairment does occur with N 2 O. The clinician has the ultimate responsibility to determine if a patient is completely recovered before their discharge.
Sedation Recovery Assessing recovery The assessment begins after the initial 5 minute post procedure oxygenation period and before removing the oxygen and nasal hood. Obtain vital signs Question the patient about how they feel. –Any lethargy, headache, dizziness, confusion, nausea? If any symptoms are present, continue O2 Discharge only when assured patient is fully recovered. –Patient should be alert and oriented with a pleasant demeanor –Vital signs should be stable and within baseline limits –Patient responses, eye appearance, and body movement should be within baseline limits
Documentation Documentation of the procedure should include the following: ASA classification Indications for N2O/O2 Pre and post Aldrete score Pre and post procedure vital signs (including SpO2) Concentration of nitrous oxide and duration of administration Length of time post procedure oxygen was administered Patient recovery Adverse reactions / comments
Potential biohazards of N 2 O for health professionals No direct evidence suggests any causal relationship between chronic low-level exposure to N2O and potential biologic effects. The following preventive measures to reduce or eliminate trace gas contamination are encouraged: –Operate a delivery system with scavenging capabilities, accurate flow meter, adequate vacuum, and a variety of mask sizes. –Maintain a ventilation system to include vent exhaust to outside and fresh air exchange when possible. –Maintain an adequate suction system – ensure vacuum of at least 45L/min, use appropriate size mask, discourage patient talking. –Inspect cylinder attachments, lines, hosing, and reservoir bag for leaks. –Calibrate flow meters every 2 years.
Conclusion N 2 O/O 2 sedation can reduce the stressful and painful experiences of our pediatric patients who require minimal sedation. It may be used in children 2 years and over. Please refer to the hospital policy ‘Nitrous Oxide Sedation’ for specific information about the use of N 2 O/O 2 at Dayton Children’s. Clinicians who will be administering N 2 O/O 2 sedation will receive additional education and complete a competency on the N 2 O/O 2 equipment to be used at Dayton Children’s.
References Clark, M. & Brunick, A. (2007). Nitrous oxide and oxygen sedation (3 rd ed.). UK: Elsevier. Farrell, M., Drake, G., Rucker, D., Finkelstein, M. & Zier, J. (2008). Creation of a registered nurse-administered nitrous oxide program for radiology and beyond. Pediatric Nursing, 34(1), Retrieved September 23, 2008, from CINAHL Nursing database.