Conscious sedation is used for many different medical and surgical procedures. These procedures can be direct medical or surgical interventions or merely diagnostic procedures such as gastroscopy or colonoscopy. It is also used regularly in dentistry to limit the pain and anxiety that accompanies dental treatment. The commonest form of conscious sedation uses various sedative drugs such as midazolam, propofol, diazepam and nitrous oxide/oxygen. All of these drugs are used at low concentrations to produce conscious sedation. Unfortunately at higher concentrations all may produce anaesthesia, which is a much deeper form of sedation. In contrast to conscious sedation where verbal communication between doctor and patient is possible (and even essential) this does not apply to anaesthesia. When a patient is anesthetised they are unconscious and dependent on the doctor and staff to ensure they remain alive. Modern anaesthesia requires monitoring with sophisticated external monitoring systems that measure the electric currents from the beating heart (via an electrocardiograph), the oxygen saturation of arterial blood (via an oximeter) as well as electrical brain wave patterns (through an electroencephalograph). This applies to all the drugs mentioned above except nitrous oxide/oxygen. Nitrous oxide/oxygen conscious sedation is so safe that none of these external monitors are needed. For this reason, when drugs other than nitrous oxide/oxygen sedation conscious sedation is used for medical and dental procedures it is safest that the actual sedation is supervised by another doctor, dentist or anaesthetist. When nitrous oxide is used for conscious sedation in dentistry the dentist who administers the nitrous oxide/oxygen can supervise the patient easily without these extra monitoring devices and is able to do the dental treatment at the same time. This is usually not the case with the other drugs commonly used for conscious sedation in dentistry. There is one requirement that is absolutely essential when conscious sedation with nitrous oxide/oxygen is given by the sedationist who provides simultaneous treatment. They must use the correct standardised equipment incorporating a fail-safe device, which ensures that the patient receives a minimum of 20% of oxygen in the gas mixture. This prevents the patient receiving a mixture that could cause brain damage. If the oxygen level falls below 20% the nitrous oxide administration is halted by the fail-safe device which is part of the standardised equipment.
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