Sedation during diagnostic or therapeutic procedures must be safe and comfortable for patients. To achieve this, Non-anesthesiologists performing sedation should be fully trained in the physiology of sedation, the pharmacology of sedatives and analgesics, the monitoring of patients, and in airway support, ventilatory care, and cardiopulmonary resuscitation. Good sedation practice involves presedation assessment and optimal selection of patients, careful monitoring and support from dedicated staff, and adherence to recovery and discharge criteria.
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Modern medicine often involves minimally invasive interventions for diagnostic or therapeutic purposes. Apart from producing pain and discomfort, such procedures can invoke fear and anxiety reactions. Increased sympathetic activity with tachycardia and hypertension has the potential to precipitate myocardial ischemia or infarction in susceptible patients. Patients undergoing these interventions often require sedation to enhance procedural safety, comfort, and success. The recent proliferation of these procedures increases the demand for sedation. Sedation carries significant risks to patients, especially when inappropriate techniques are used by inexperienced or untrained personnel. As non-anesthesiologists are increasingly involved in sedation, it is vital for them to understand safety issues and receive proper training. This article reviews various factors affecting the safety of procedural sedation, including the performance of sedation, monitoring guidelines, and training issues.
Patient-controlled sedation (Technique and Drugs available)
Patient-controlled sedation (PCS) allows the patient to control his/her own level of sedation by triggering an infusion pump to deliver a programmed bolus of sedative when needed. 
Propofol and midazolam are commonly used for PCS
A loading dose may be given by the anesthesiologist initially to achieve the desired sedation, followed by patient-activated boluses to maintain sedation. A background infusion may also be used, especially for longer procedures, as patients often become restless or fatigued. The ability to control one’s own sedation may be anxiolytic and it has been found that many patients actually prefer ‘light’ sedation. Even in phobic patients, PCS has been shown to use 30% less propofol than the clinician-controlled technique. 
Patient satisfaction, qualities of sedation and operative conditions during PCS are comparable with TCI. When sedatives with a rapid onset of action are used together with a ‘lock-out’ interval, the patient-controlled approach should be safe, as deeply sedated patients usually cease to press the control button. However, it has been reported that an individual patient who deliberately tries to achieve unconsciousness will have an 11% chance of success. 
A variation of PCS with background infusion is to incorporate a patient-controlled element into TCI. A lower initial target concentration is set and the patient is allowed to increase the target propofol concentration in small increments by controlling the handset. Safety measures include a ‘lock-out’ interval, a maximum permissible target concentration, and a programmed decrement in target concentration after fixed intervals with no demands. One study has shown that 22% of patients developed de-saturation requiring supplementary oxygen therapy with such patient-controlled TCI. 
Remifentanil is a new, potent, fast-onset, and very short acting intravenous opioid. It is largely non-cumulative, with a context-sensitive half-life independent of the duration of infusion. Most investigators are in agreement on the short discharge times and stable haemo-dynamics achieved with remifentanil use. 
However, Litman has drawn attention to the high incidence of life-threatening respiratory depression associated with remifentanil use and others have cautioned that careful monitoring of ventilation must be instituted. As a result of its potency and high potential for respiratory depression, remifentanil is not recommended for non-anesthesiologist use or for office-based sedation where there are no facilities available for respiratory support. 
Sedative sparing effects of music
Conjunctive use of favorable music via a headset has been shown to decrease PCS’ use in awake patients undergoing procedures performed under regional anesthesia. The intra-operative music chosen by the patient may assist by providing a familiar auditory environment, distracting the patient from upsetting issues during the procedure.
The use of headsets also has the advantage of screening out the background noise of the operating theatre. 
Noise can increase anxiety levels and this is an issue in the operating theatre or MRI suite.
Office-based sedation 
Sedation is sometimes required for short and minimally painful procedures conducted in the office-based or non-hospital setting. The concerns are essentially the same as those for hospital-care sedation. The sedative and analgesic agents chosen should have a rapid onset and offset of Safety and comfort during procedural sedation action to allow early recovery with minimal haemodynamic disturbance or respiratory depression. Patients selected should not have significant co-existing cardiovascular, respiratory, endocrine, or neurological conditions.
Risks of sedation 
Sedation results in depression of the central nervous system. Loss of consciousness due to sedation shares the same risks as the use of general anesthesia.
Risks associated with sedation include:
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- Over-sedation, leading to unintentional loss of consciousness;
- Depression of protective reflexes, predisposing the patient to pulmonary aspiration;
- Depression of respiration, leading to hypoxemia, myocardial ischemia, and arrhythmia;
- Depression of the cardiovascular system;
- Use of a wide variety of drugs, and combinations of drugs with the potential for drug interactions.
- An adverse outcome is more likely when more than two drugs are administered, or when nitrous oxide is combined with other types of drugs potential for excess dosing to compensate for inadequate analgesia. 
- Individual variations in response to the drugs used, particularly in children, the elderly, and those with pre-existing medical disease. Children aged between 1 and 5 years are at greatest risk, although most have no severe underlying disease 
- Risks relating to inadequate skills or experience of the person administering sedation, such as drug errors, inadequate evaluation, inadequate monitoring, or premature discharge. 
It is important to note that all sedatives and narcotics can cause problems even when used in recommended doses. All clinical areas employing sedation techniques have reported adverse events.
Ways to ensure safety during sedation
Medical practitioners involved with sedation should have a good knowledge of the physiology/pharmacology of sedation, and be competent in patient monitoring and resuscitation. The anesthesiologist is the ideal person to sedate and monitor the patient. 
Guidelines and training
In most circumstances, sedation is conducted by non-anesthesiologists. To prevent or manage complications during sedation, the practitioner has to follow certain safe practice guidelines. Various professional bodies and organizations, such as the Hong Kong College of Anesthesiologists and the Australian and New Zealand College of Anesthetists, have promulgated guidelines to assist the practitioner in performing sedation safely.
These guidelines outline the general principles of safe practice without providing specific details. Individual departments need to build their own practice guidelines based on these principles to cater for variations in patients, procedures, practitioner skills, and physical setting. Doctors and nurses involved with sedation should undergo regular recertification of cardiopulmonary resuscitation skills. Protocols for resuscitation such as the Advanced Cardiac Life Support protocol, and for managing complications such as de-saturation, should be adopted in areas where sedation is conducted. The staff involved should also receive training in the use of sedative drugs and in appropriate monitoring of patients.   
Monitoring during sedation is the key to safe practice. The following procedures are recommended.
- Maintain a constant dialogue with the patient during the procedure. This ensures that the patient has not progressed into unintended deep sedation or loss of consciousness.
- Complete simple clinical assessments such as patient color, temperature, blood pressure, and pulse are a basic requirement. 
- Use non-invasive blood pressure monitors and pulse oximeters to enhance safety during sedation. Early detection and treatment of hypoxaemia is crucial. The use of electronic monitoring equipment should not be considered a substitute for continuous clinical assessment. 
- Routine supplemental oxygen is recommended to decrease the incidence of de-saturation. 
Equipment and facilities
The area where sedation is conducted should be supplied with appropriate equipment and drugs required for cardiopulmonary resuscitation, and airway, ventilatory, and circulatory support. In addition to monitoring equipment, oxygen, adequate suctioning facilities, airway control devices such as endo-tracheal tubes and laryngoscopes, manual resuscitators, defibrillators, antagonists for benzodiazepines, and opioids should be available. The trolley for performing the procedure must be tiltable.  
A key to minimizing complications in procedural sedation is slow and careful titration of drugs to the desired effect. Adequate time must be allowed for drugs to exert full effect before giving additional doses. 
The medical practitioner responsible for sedating the patient should assess the patient before the procedure. The patient’s American Society of Anesthesiologists (ASA) status should be determined for risk stratification. The patient’s known medical history allows the practitioner to plan appropriate sedation and monitor strategies. Anesthesiologists should be involved in sedation of high-risk patients. 
Vital signs should be monitored until the patient is awake and alert. The patient should be observed until discharge criteria related to conscious state, airway patency, ventilation, and circulation status are met. 
Medico legal aspects
Sedation is an intervention carrying significant risks to the patient. It is necessary to explain all significant risks to the patient and to obtain consent for sedation. It is also important to have another person present during the sedation process to circumvent any potential claims with legal ramifications made by the patient. This is especially important when propofol is used, as sexual delusions can occur in patients during and after propofol administration. The patient may consequently believe he/she was sexually assaulted while under sedation. 
Patient safety and comfort constitute the prime priorities in patient management. The provision of sedation carries the risk of potentially life-threatening complications. Adherence to recommended sedation guidelines is therefore mandatory. Choice of agents, techniques, and medical personnel responsible for the proper care of patients should be based on patients’ specific needs rather than cost and efficiency alone. To ensure the safety of all patients undergoing sedation, training of staff and provision of support facilities for maximal patient care are also critical.
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