 The topic that we will be looking into today is inhalation sedation also known as conscious sedation or moderate sedation. This will be the contents we will be covering it under. Now as we all know sedation is one of the most commonly used pharmacological behavior management techniques which comes under extremely handy for dental procedures, extremely handy especially for pediatric behavior management. Now on the screen what you can see is the spectrum of pain and anxiety control because all the agents that we use for sedation do not produce the same level of pain and anxiety control. Different agents produce different depths of sedation. Now as you can see in an increasing order on this side of the spectrum comes the conscious sedation agents that is Ayurvedic sedation, hypnosis, local anesthesia, oral or rectal sedation, nitrous oxide etc. Whereas methods such as general anesthesia, tracheal intubation etc. They come under the unconscious side of the spectrum. Now the AAPD has defined certain goals of sedation in the pediatric patient for diagnostic and therapeutic procedures. So any form of sedation used should ensure that you are used to guard the patient's safety and welfare, to minimize physical discomfort and pain, to control anxiety, minimize psychological trauma and maximize the potential for amnesia, amnesia in the sense that the memory of the procedure that is any memory that the child retains during the procedure is not significant and the child is able to forget it to prevent the trauma from it. Control behavior and or movement to allow the safe completion of the procedure, return the patient to a state in which safe discharge from medical supervision as determined by recognized criteria can be done once the procedure is completed. Now moderate sedation or conscious sedation is a drug-induced depression of consciousness during which patients respond purposefully to verbal commands or light tactile stimulation. Now nitrous oxide is one of the most commonly used agents for inhalation sedation to produce conscious sedation. Let's have a look into the history of nitrous oxide. This was, nitrous oxide was first synthesized in as early as 1722 by John Priestley who described it as deflogisticated nitrous air. In 1794 what was hired by Beddow's to invent a machine which was capable of producing this nitrous oxide and they called it fictitious airs. In 1790 Humphrey Davy was the first one to refer to nitrous oxide as laughing gas. So owing to the effect of euphoria that nitrous oxide gas tended to produce, during the 1820s laughing gas was majorly used as a source of entertainment during parties or celebratory gatherings. In one such party Dr. Horace Wells saw that a man who was under the influence of nitrous oxide though he hurt a store did not feel any pain and this got him interested in the effect of nitrous oxide that it may lead to pain control and this effect can be used in dental procedures as well and hence Dr. Horace Wells used it, tested the effect of nitrous oxide in a procedure of molar extraction. Similar to nitrous oxide other agents, anesthetic agents have been considered for the conscious sedation which include either and a volatile agent named chloroform however in 1864 the American Dental Association officially recognized Dr. Wells as the discoverer of nitrous oxide and they confirmed that nitrous oxide can be used as an analgesic or anesthetic. So what are the ideal requirements of an inhalation agent? The agent should be rapid and have a rapid and pleasant induction and also the emergence from anesthesia should be very quick. It should have rapid and easily identified changes in the depth of anesthesia so that the safety margin can be maintained. It should lead to adequate relaxation of skeletal muscles, there should be a wide margin of safety, there should be absence of toxic or any other adverse effects at normal doses, high degree of specificity of action should be there. It should be easy to administer and it should be useful for all age groups. Objectives include as we saw under the gold sedation earlier to reduce or eliminate anxiety, to reduce untoward movement and reaction to dental treatment, to enhance communication and patient cooperation, to raise the pain reaction threshold, to increase tolerance for longer appointments, to aid in treatment of the mentally or physically disabled or medically compromised patient, to reduce any possible gag reflexes and to potentiate the effects of sedatives. Now in what kind of patients is inhalation sedation or conscious sedation indicated? It is indicated in fearful and anxious patients. In certain patients with special healthcare needs where you cannot carry on a procedure normally because of any untoward movement that can cause disruption of the procedure and can lead to injuries in the child. It can also be used even if the child is cooperative but however the procedure is going to be extremely lengthy where the child can turn potentially uncooperative. It can be used if a patient tends to have a lot of gag reflex which can interfere with dental treatment. Can be used in a patient for whom profound local anesthesia cannot be obtained. There are some relative contraindications for the use of nitrous oxide sedation. It is contraindicated if there are some chronic obstructive pulmonary diseases. Severe emotional disturbances or drug related dependencies if you see any such potential trends in the patient then of drug dependency or emotional disturbances then it is such sedation inducing agents are best avoided. It is also best avoided during the first trimester of pregnancy or also in methylene tetrahydrofolate reductase deficiency. This is because of the pharmacodynamics of nitrous oxide then or if the patient has had any recent illnesses such as cold or congestion that may compromise the airway it is best to postpone the procedure till the airway is completely clear. Now this is how nitrous oxide is synthesized this is the reaction when ammonium nitrate is heated at the temperature of 240 degree Celsius it disintegrates to nitrous oxide. So some of the common impurities that can be found in the agent is nitrogen, nitric oxide, ammonia, water and carbon monoxide. So nitrous oxide is compressed in stages so that the less liquefied gases are separated and then it is compressed and stored in metal cylinders. So once it is stored in the cylinder 30% of the nitrous oxide in the cylinder is present in a liquefied form. The physical properties of nitrous oxide include that it is non-irritating and sweet smelling colorless gas it gets converted to a clear colorless liquid at 28 degrees. It is stable under pressure and it is marketed in cylinders as liquid under pressure. It is relatively insoluble. Now this is a comparison of nitrous oxide that is inhalation sedation. As you can see here compared to other agents. You can see that the onset of action is much lower, the peak action sets in much earlier when compared to other agents such as oral rectal IM or IV. Duration of action is fixed in all the other agents the duration of action is fixed whereas the advantage of inhalation sedation is that the duration is variable and it can be controlled depending on the amount of sedation that the dentist is using. The recovery time is also extremely low so the effect of the sedative can be reversed almost as soon as the procedure is completed. And one of the main advantages of inhalation sedation is that titration is possible. Titration is possible in the sense that we can control the amount of the agent that we are introducing into the body of the patient. This cannot be done in oral rectal or IM form sedation. Other advantages include that the patient can be discharged from office following procedure with no prohibition on any activities. They will be completely normal once the effects are reversed. There is no injection required because it is given through a nasal hood through inhalational means. There are no adverse effects of drugs on liver, kidneys, brain or CVS. There are no effects. It is completely reversible. Nitrous oxide can produce analgesia when given in sedative concentrations and nitrous oxide is eliminated from the body within 5 to 10 minutes after discontinuation of use. This summarizes the advantages and advantages of nitrous oxide. Rapid onset of action, titration is possible, depth of sedation can be altered, duration of sedation can be altered, rapid recovery rate once the procedure is done, no injection required. It is extremely safe and has very few, if any, side effects and it can be used instead of local anesthesia though it is not completely recommended. However, the disadvantages include weak potency. The angiolices and analgesia produced by nitrous oxide is definitely not comparable to some other agents like IVIM or general anesthesia for that matter. Significant dependence on psychological reassurance, interference of the nasal hood with injection to anterior maxillary region because the nitrous oxide will be supplied using a nasal hood which will be sitting on the nose. If there are any procedures that have to be done in the maxillary anterior teeth, it may make it a little tricky. Patient must be able to breathe through the nose and cooperation is required. Nitrous oxide pollution and potential occupational exposure, health hazards are possible and initial cost of equipment is high and the equipment which we will be looking at also occupies considerable space. Nitrous oxide is said to have analgesic properties, angiolytic properties and also amnestic properties. Now these are some of the properties of characteristic features of nitrous oxide. First is the concentration effect. This occurs when high concentration of a gas is administered, higher the concentration of the gas inhaled, more rapidly the arterial tension of the gas increases that is known as the concentration effect or the and next is the second gas effect. This refers to the rapid uptake of the second inhalation agent administered following nitrous oxide so if at all nitrous oxide is used for induction of sedation, the second gas effect should be kept in mind because this influences the rapid uptake of the second inhalation agent that is introduced after this. Now one of the most important features this is called as diffusion hypoxia very important. So on the termination of procedure what happens is the nitrous oxide that has entered the lungs once the procedure is terminated and you switch off the supply turn off the supply of nitrous oxide it diffuses out of the blood very rapidly and gets eliminated. So nitrous oxide now escapes in alveoli which from the alveoli in such rapidity that oxygen becomes very diluted and oxygen carbon dioxide exchange is disrupted creating hypoxia. Because of this rapid elimination there is a disruption in the normal oxygen carbon dioxide exchange that takes place during the within the alveoli and this leads to lower levels of oxygen causing diffusion hypoxia. So what do we do to avoid this usually once the procedure is done the patient should be flushed with 100% oxygen for the first few minutes following discontinuation and this can lead to avoiding diffusion hypoxia. Now coming to the pharmacodynamics of nitrous oxide, nitrous oxide is very less potent anesthetic. So the drug potency is usually determined by minimum alveolar concentration. So minimum alveolar concentration is defined as the alveolar concentration of an anesthetic at which 50% of patients fail to respond to a standard surgical stimulus. Now the MAC for nitrous oxide is 104 to 105%. This shows that the potency is very less and hence the safety margin for the use of this drug as an anesthetic is extremely high. However, nitrous oxide alone is not able to produce very profound anesthesia. Now what are the effects of nitrous oxide on different organ systems? On the central nervous system it increases cerebral blood flow, cerebral metabolism and intracranial pressure. When administered in conjunction with physiological levels of oxygen, nitrous oxide produces very mild depression of CNS. On the CVS, nitrous oxide causes direct myocardial depression but increases central sympathetic outflow but no significant changes in heart rate or cardiac output are seen. Respiratory system, nitrous oxide causes a decrease in the tidal volume and an increase in the respiratory rate. Now coming to the preparation and setup for sedation procedures. Now any sedation procedure for that matter and we are here talking about the inhalation sedation procedure. These are the main important things that you need to remember. So this can be remembered using the acronym SOAPME, S stands for Suction, O stands for Oxygen, A stands for Airway, P stands for Pharmacy, M stands for Monitors and E stands for Equipment. So one needs to make sure that this checklist is thoroughly ensured before beginning any sedation procedure. Now coming to the armamentarian, the two kinds of units are available for the supply of nitrous oxide for sedation. One is the continuous flow unit and another is the intermittent flow unit. The continuous flow unit delivers continuous flow of the gas regardless of the respiratory pattern of the patient and the intermittent flow unit does not deliver gas continuously but varies the rate and volume according to the patient's respiratory demands. So if the patient's respiratory rate is changing, the intermittent flow unit varies the supply in accordance whereas continuous flow unit constantly supplies the same amount. There is a larger margin of errors in the intermittent flow unit when compared to the continuous flow unit. These are the portable unit and portable unit which can be moved across the clinical area and the central storage unit. Now coming to the compressed gas cylinders, gases are dispensed at a pressure greater than 25 pounds per square inch at 25 degree Celsius. It is very important to keep grease and oil away from the cylinder and the cylinders can be manufactured in various variety of sizes and then the one important thing to remember is the color coding of the compressed gases. So this color coding is international and it is standardized so that there is no mistake in the gas that is supplied. For example, oxygen, the color coding for oxygen is, the international color coding of oxygen is white, it is green only in the US. Nitrous oxide is light blue, nitrogen, gray bottom or in shoulder, carbon dioxide is gray whereas helium is brown. So this color coding ensures the, is one of the safety measures. Then coming to regulators or reducing valves, this is located in between the compressed gas cylinder and the flow meter. So this regulator helps us in regulating the pressure of the gas that is coming out of the cylinder before it is supplied to the patient. So it reduces the high pressure of gas coming out of the cylinder to one that is safe for the patient and the sedation unit. Then comes a yoke assembly. This yoke assembly holds the compressed gas cylinders tightly in contact with the portable sedation units. The metal pins located on the yoke assembly constitutes the pin index system. We will be looking at this a little later. Now coming to flow meters, this permits the administrator to deliver a precise volume of gas to the patient. The calibration of the gas, of the nitrous oxide and oxygen gas that is supplied can be seen on the calibrated flow meters. It is either digital or analog. So you can control the concentrations that can be used. Now this is the reservoir bag. This is made of rubber or silicone and the capacity of the reservoir bag that is commonly used in dentistry is a 3-liter bag. Its function is that it acts as a reservoir from which additional gas can be drawn. And if at all the patient's respiratory demand exceeds the delivered gas flow, there is a buffer of gas that is maintained within the bag. It monitors the device for respiration, means of providing oxygen during assisted ventilation. Then the conducting tubes. These are the conducting tubes. So it connects the reservoir bag to the nasal hood, a variable in length. It can either have a large diameter or it can be corrugated. That is the inner tube can be corrugated which prevents the occlusion of the lumen. It is attached through non corrugated tubes to the nasal hood. Now this is the nasal hood through which the gases introduced to the patient's respiratory system. It is designed to fit comfortably and securely over the nose. There are two types, the scavenging hood or the traditional hood. Scavenging hood has a smaller inner mask and a larger outer mask. The outer mask is connected to the suction device. This minimizes nitrous oxide contamination. This is a schematic diagram that shows the structure of the nasal hoods. Now this whole unit, this whole sedation unit, nitrous oxide sedation unit has certain safety features that ensure that there is no margin of error that can lead to any disruptions. These are the safety features that are important to remember. One, it is the pin index safety system. This consists of a series of pin configuration for each gas on the yoke and matching series of holes on the gas cylinders. So now for example if you attach a different cylinder for a different cause that would be extremely dangerous. To ensure that this interchange of cylinder does not happen, each particular yoke assembly has an index system that is unique to that particular gas alone. And so only that gas cylinder can be attached to this pin. For example, the pinhole system in oxygen will be completely unique to oxygen alone when compared to nitrous oxide. So you cannot by mistake attach a nitrous oxide cylinder in place of a oxygen cylinder. This is how the pin index safety system is designed. Next comes the diameter index safety system. This is with respect to the diameter. That is the diameter of the coupling differs. Nitrous oxide coupling is larger than the oxygen one. Hence again the interchanging of cylinders is not possible. Minimum oxygen liter flow. In most units a preset minimum liter flow of oxygen through the flow meter. 2.5 or 3 liter per minute is ensured. So nitrous oxide flow cannot start until a flow of oxygen has been established. Without oxygen, without a minimum amount of oxygen being introduced, nitrous oxide sedation cannot start. So this is a minimum oxygen liter flow safety feature. Then again is the minimum oxygen percentage. So minimum oxygen percentage that is required to be delivered along with nitrous oxide is 30%. So 70% is the highest amount of nitrous oxide that can be supplied because without 30% the oxygen level cannot go below 30%. And the insurance of this it allows for error in calibration of flow meters. Then the oxygen fail safe. This is if it prevents administration of 100% nitrous oxide. So if the oxygen cylinder becomes empty by any chance, this oxygen fail safe mechanism ensures that the nitrous oxide supply is immediately terminated. It does not continue. If the oxygen is empty. Then comes the emergency air inlet. It is located above the reservoir bag. If flow of gas ceases or when oxygen fail safe is activated, this inlet opens allowing the patient to breathe comfortably. Next is the alarm. It is attached to the oxygen fail safe system. If any disturbance is there in the gas flow, this alarm goes off and alerts the operator that the gas flow is disturbed. Next is the oxygen flush button. Permits delivery of high flow of oxygen delivery to the patient. It is very advantageous during emergency situation. It automatically stops the nitrous oxide delivery and delivers 100% oxygen flush. Then the reservoir bag as we saw before reservoir bag acts as a buffer and it also ensures that the respiratory rate of the patient is fine. Colour coating. This also we saw before different gases have different colour coded cylinders. Quick connect delivers positive pressure of oxygen and the lock. This is included on protective caps of cylinders. So this lock cannot be opened in any simple ways. This prevents the misuse of nitrous oxide. Coming to the pretreatment instructions. Introduce the patient to inhalation sedation by giving proper instructions to instructions and explanations to the patient and parents. Discuss benefits gained by the patient and operator. Familiarize the patient with the procedure to relieve any fear and anxiety. Use open-ended statements. Pre-operative antibiotics and anti-anxiety drugs can be used if necessary. Heavy meals should be avoided before the procedure. Technique of administration. Position the patient in a comfortable recline position. Sedation unit should be positioned behind the patient out of the line of sight of the patient. Select and place the appropriate sized nasal hood over the nose. It shouldn't be too big or too small. It shouldn't be uncomfortable. And also very important to remind the patient to breathe through his nose. Secure the nasal hood by adjusting the slip ring behind the headrest. Determine the flow rate for the individual by asking the patient if he is able to breathe comfortably. Then observe the reservoir bag to observe the respiratory rate of the patient. Then begin titration of nitrous oxide. To begin with, administer 20% nitrous oxide for 60 to 90 seconds and look for signs and symptoms of the sedation. Observe the patient. If initial concentration of nitrous oxide is inadequate, increase the nitrous oxide levels in 10% increments only. You administer 20% first, then you test the signs and symptoms of the patient whether any appropriate level of sedation is achieved. If not, increase it in 10% increments only. Then what are the signs and symptoms that you test for in the patient? Ask for signs and symptoms like lightheadedness, a tingling sensation, warmth or heaviness. Sensations of warmth or heaviness indicate that the patient is approaching the desired level of sedation. Now this table summarizes some of the symptoms and signs that you see depending on the level of sedation that is achieved by nitrous oxide. In early to ideal sedation, you see lightheadedness, tingling, wave of warmth, feeling of vibrations throughout body, numbness of hands and feet, numbness of soft tissues, euphoria, lightness, etc. Heavier sedation, it can cause hearing, especially if distant sound becomes more acute. You get a very acute sense of hearing, sleepiness, sweating increases, laughing or crying, dreaming or nausea. And over sedation causes nausea or loss of consciousness. In the beginning of dental treatment, patient appears relaxed, continued titration till optimal sedation is achieved, continue to observe the patient and inhalation unit during the procedure. After completion of treatment, nitrous oxide flow should be terminated and oxygen should be returned to flow rate determined. And 100% oxygen is flushed for three to five minutes to avoid diffusion hypoxia. Then coming to the discharge of the patient, vital signs are recorded, patients' response to verbal commands are observed, modify neurological tests such as the trigger test for motor coordination. I use, the child can be given this and asked to connect the dots on the figure outlined immediately. This will help us in understanding if the child has achieved the desired level of motor coordination. Then once the discharge is done, cleanse the equipment, sterilize it appropriately. Now, coming to safety of pediatric patients, not advised to let child fall asleep under sedation. Make sure that the child is awake. Silent regurgitation is most engaging concern in this situation. So any form of regurgitation should be avoided. Maintaining conversation with child ensures protective laryngeal and pharyngeal reflexes are intact. It should be ensured that the protective reflexes in the child is intact. Parents are generally dismissed before procedure starts if child is three years or older. Some of the possible complications of this include inadequate or incomplete sedation, poor patient experience, equipment performance can be hampered. This can be prevented by routine inspection of the equipment. And in some cases, approximately 0.5% of cases it can cause nausea and vomiting, which is commonly due to over sedation or hypoxia or presence of food in stomach if the patient has had a very heavy meal just before the procedure. In some cases, nitrous oxide can displace air from the sinus. And this can cause tooth pain associated with sinus procedure. It can also be called vertigo because of prolonged exposure of the vestibular cochlear complex to differential air pressure. And in some cases can also cause Burwell discomfort. One main disadvantage of nitrous oxide is the potential occupational hazards that can be caused. There is a higher incidence of hepatic renal and urological disorders among the exposed personnel. Increased spontaneous abortions in chair side assistance and congenital abnormalities in their children have been reported. And inactivation of the methionine synthase enzyme, which is linked to vitamin B12 metabolism, has also been reported on prolonged and continuous exposure to extremely high levels of nitrous oxide. This summarizes the American Academy of Pediatric Dentistry guidelines that is specifically given for inhalation sedation or analgesia equipment that delivers nitrous oxide must have the capacity of delivering 100% and never less than 25% oxygen concentration. Equipment that delivers variable ratios of nitrous oxide to oxygen and that has a delivery system that covers the mouth and nose must be used in conjunction with a calibrated and functional oxygen analyzer. All nitrous oxide to oxygen inhalation divisor should be calibrated in accordance with appropriate state and local requirements. Concentration should be given to the National Institute of Occupational Safety and Health Hazards for the scavenging of waste gases. And newly constructed or reconstructed treatment facilities, especially those with piped in nitrous oxide and oxygen, must have appropriate state or local inspections for proper certification. Nitrous oxide in oxygen with varying concentration has been successfully used for many years to provide analgesia. The use of nitrous oxide for minimal sedation is defined as administration of nitrous oxide with the balance as oxygen without any other sedative, narcotic, or other depressive drug, or concurrent with the nitrous oxide to an otherwise healthy patient, that is, in ASA class 1 or 2. And the patient should be able to maintain verbal communication throughout the procedure. If nitrous oxide in oxygen is combined with other sedative medications, such as chloral hydrate, merazolam, or an opioid, or if nitrous oxide is used in concentrations more than 50% percent, the likelihood for moderate or deep sedation increases. In this situation, the clinician must be prepared to institute the guidelines for moderate or deep sedation, as indicated by the patient's response. The recommended discharge criteria are as follows. CVS function and airway patency are satisfactory and stable. The patient should be easily arousable and protective reflections should be intact. The patient should be able to talk. The patient can sit up unaided. For a very young or handicapped patient, a child incapable of usually expected responses, the pre-sedation level of responsiveness should be achieved. The state of hydration should be adequate. Some of the other agents that can be used for sedation are halothane, sevofluorine, and desferine. So inhalation sedation utilizing nitrous oxide oxygen has been a primary technique in the management of dental fears and anxieties for more than 150 years and remains so today. I minister properly with well-maintained equipment. The technique has an extremely high success rate coupled with a very low rate of adverse effects and complication. Its main advantage is it is tight-ribble. You can control the concentration of nitrous oxide that you are supplying. It is easily reversible and the patient can be discharged almost immediately with no complications. Thank you.