Frequently Asked Questions
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D. INHALATION SEDATION
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1. Is inhalation sedation suitable for a patient with severe asthma and underdeveloped lungs? I have a 30-year-old lady with 50% lung capacity who is classified as having severe asthma but claims it is well-controlled. She is very nervous and has two difficult extractions planned.
Intravenous sedation is contraindicated in this case.
Inhalation sedation is not a suitable alternative, as the continuous oxygen delivered may obtund the hypoxaemic respiratory drive that she is likely dependent on.
Consider a referral to secondary or tertiary care.
2. Please advise on concerns regarding the number of inhalation sedation patients that one of our clinicians is treating in a day. The team are not experiencing any side effects. We have good ventilation in the surgeries and a scavenging unit for the MDM machine. 8 patients a day are treated with IHS, with regular breaks, is there anything else we can do?
Is this acceptable from an exposure standpoint? Should a nitrous oxide monitor be considered?
The occupational exposure to nitrous oxide should not exceed 100ppm over an 8-hour period. An article published by N Girdler in 1998 quantified this as maximum of 2½ hours a day in the sedation environment to remain within the occupational exposure limit.
Most patients are receiving nitrous oxide for about 30-45 minutes of their appointment time. So, a limit of 4 - 5 patients a day would be reasonable to stay within the occupational exposure limits as long as your surgery has adequate active scavenging and is well ventilated.
Close attention to technique (e.g. minimising mouth breathing) and the use of rubber dam to help reduce the surgery concentration of nitrous oxide to a minimum would be useful.
The regulations we are guided by are below for further advice from the health and safety executive.
EH40/2005 Workplace exposure limits, EH40 (Second edition, published 2011).
If there are any concerns regarding pregnancy and inhalation sedation, there is no definitive guidance. In the past when scavenging was passive rather than active, some research was carried out into the incidence of spontaneous abortion seen in pregnant dental nurses assisting for procedures under nitrous oxide inhalation sedation. High concentrations of nitrous oxide were found to be in the environment and it was concluded that there may be a link. However, the results of this research have since been questioned.
As we now use active scavenging, well-ventilated surgeries and pay attention to the technique (e.g. minimising mouth breathing) in addition to using rubber dam where at all possible, the chances of nitrous oxide having an effect on fertility or being the cause of spontaneous abortion in a pregnant member of staff in modern surgeries is highly unlikely.
However, this is a very emotive issue and for any pregnant staff or those trying to conceive, it can be an anxiety-provoking one also. In some services, for the reassurance of the staff concerned, pregnant nurses are not placed with dentists providing inhalation sedation, and pregnant dentists are not required to treat patients under inhalation sedation. This may not be possible for all services.
3. I am a dental therapist that trained with SAAD about 10 years ago.
I have a question about titration. I was taught to titrate the nitrous (of course ) to a level that was appropriate. I was also told that if you are treating the same patient several times over that after the initial oxygen only that you could safely go to the level of nitrous of previous sessions, safely, without the need to titrate. Is this still correct?
It is important to titrate to clinical need each time a patient is seen. For the same patient, the level of nitrous oxide required to facilitate treatment will vary from appointment to appointment. Aside from the actual procedure and thus the pain and needs of the patient and dentist changing between each visit, the level of sedation achieved with any given nitrous oxide: oxygen ratio will change. This is because the depth of the anxiolysis and analgesia is not purely drug dose related - the technique uses semi hypnotic suggestion and perception of pain and anxiety is multifactorial.
For example, anxiolysis will vary according to the patient's baseline anxiety and how stressed / calm they are before they enter the surgery, often the time of day can have an effect, as can the quality of sleep a patient has had, if they have eaten, the degree to which the specific procedure to be undertaken provokes anxiety and discomfort and the interplay between the sedative effect and the sedationist's semi hypnotic suggestion. As a patient gets to know and trust the sedation provider and dental team and feels more comfortable, the end titration dose needed to complete treatment is also likely to reduce.