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Procedural sedation and analgesia (PSA) is most commonly used in the emergency room (ER), and it involves making patient pain free and minimizing awareness without completely anaesthetizing patient. It utilizes various drugs alone or in combination, and is given not necessarily by an Anesthesiologist but by trained personnel in emergency medicine. Main goals of PSA are analgesia, amnesia and anxiolysis. Procedural sedation is used for patient belonging to American Society of Anesthesiology (ASA) physical status classification I, II and III, ASA IV and higher being an absolute contraindication. Midazolam, ketamine, propofol, etomidate and fentanyl are few of the drugs most commonly used for PSA. Naloxone and flumazenil are the two reversal agents which should be readily available although less commonly used. Several clinical scoring systems have been developed for monitoring the level of sedation, bispectral analysis (BIS) is one of the more promising one.
Procedural sedation and analgesia, Analgesia, Anxiolysis, Amnesia, Ketamine, Midazolam, Bispectral analysis.
The emergency room (ER) is an environment where a variety of patients are encountered on a routine basis, of different nature and severity, many of which are associated with varying degree of pain and anxiety. Hence management of sedation and analgesia is an important component of medical care for patients and is one of the primary concerns of an ER physician. Concerns of over sedation most often leads to inadequate analgesia, inappropriate physical findings, or inappropriate patient needs1, 2. Conscious sedation is an obsolete term which is no longer in use. It had been replaced by moderate sedation. Conscious sedation was first introduced by American Dental Association and referred to as "a minimally depressed level of consciousness that retains the patient's ability to maintain a patent airway independently and continuously, and respond appropriately to physical stimulation and verbal command"3. Definitions of recently launched terminology "procedural sedation" vary widely. Procedural sedation and analgesia (PSA) is a more accurate and appropriate description. The term procedural sedation has emerged from the American College of Emergency Physician (ACEP) 4.
The concept behind PSA is to produce a state of sedation and analgesia with a minimal depression of consciousness. Airway assistance ideally should not be required and the patient should be capable of responding to physical and verbal stimulus. PSA is also helpful for managing uncooperative patients in almost all the allied disciplines of healthcare including dentistry.
Definition and prerequisites:
Procedural sedation induces a state that allows the patients to tolerate unpleasant procedures while maintaining cardiorespiratory functions by administering sedatives or dissociative agents with or without analgesics4. PSA produces a suppressed level of consciousness that is adequate to allow the administration of painful or unpleasant diagnostic or therapeutic maneuvers in a way that minimizes patient awareness, discomfort, and memory, while attempting to preserve spontaneous respiration and airway-protective reflexes. ASA revised and updated its guidelines to include the definition of "Sedation and analgesia", which includes a sequence of states ranging from minimal sedation (anxiolysis) through general anesthesia, wherein patient can easily pass into a level of sedation deeper than intended (Table 1). An anesthesiologist should provide care when deep sedation or general anesthesia is being provided; however PSA may be provided by an individual who is competent enough to use such a technique and is also capable of managing complications associated with it. In the ER, to perform painful or difficult procedures, it is a routine practice for emergency physicians (EP) to provide PSA. The Joint Commission on Accreditation of Health care Organization (JCAHO) recognizing the risks involved with sedation and analgesia for procedures mandates that sedation practices throughout an institution should be monitored and evaluated7. The ASA has published guidelines for EPs or non-anesthesiologists who provide PSA 5. Expertise in airway management is mandatory, and the provider must be able to identify signs of airway complications both early and late in the procedure. The provider should be capable of maintaining the airway during spontaneous ventilation and intermittent positive pressure ventilation with a mask and self inflating resuscitation bag.
Administration of PSA in any scenario requires a thorough understanding of depth of sedation which is briefly mentioned below. It is the minimal and moderate sedation that are used for procedural sedation and analgesia.
Various patients requiring PSA in emergency room would be better served if the objectives and goals of PSA are kept in mind8
Minimizing pain, anxiety and physical discomfort.
Minimize negative psychological impact to treatment by providing analgesia and anxiolysis along with maximal potential for amnesia.
Minimizing patient movements during the procedure.
Maximizing the chances of success of procedure and returning the patient to presedated state where safe discharge is possible.
Patients should be triaged to the appropriate Physical Status Classification (Table 2) before procedural sedation is performed 9.
Procedural sedation is appropriate for patients in Classes I, II and III. Patients with class IV and higher should be sedated by an anesthesiologist.
Degree of pain and associated anxiety level of patients usually determines the indication of PSA8 as mentioned in Table3.
There are no absolute contraindications but the physician should consider co-morbid illness or injury, the ability to manage the patient's airway, and previous problems with PSA. Patients with significant co-morbidity, cardiorespiratory compromise and anticipated difficult airway should be cautiously approached.
1. Recent (<2 hr) ingestion of large food or fluid volumes (relative contraindication). For emergency procedures, the risk of aspiration versus the benefits of sedation must be kept in mind by the practitioner10. There is however insufficient data to determine whether fasting improves outcomes.
ASA pre-procedural fasting guidelines are as follows-
Ingested Material Minimal fasting period (Hours)
Clear liquid 2
Breast milk 4
Infant formula feed 6
Non Human milk 6
Light meal 6
2. Physical class IV or greater -absolute contraindication.
3. Lack of support staff or monitoring equipment.
4. Lack of experience/credentialing on part of clinician.
Ketamine - Due to its safety profile and reliable effect it has gained wide acceptance among pediatric population. It has profound analgesic and amnestic action, without affecting pharyngo-laryngeal reflexes and hence maintains an intact airway and spontaneous respiration. Onset, duration and total dosage needed varies according to the route of administration. It is usually accompanied by excessive salivation and frequently needs to be combined with an anticholinergic. Ketamine is safe for use in adults, but careful patient selection is mandatory after ruling out usual contraindications22,23. Ketamine has an overall excellent safety profile for both adult and pediatric population22,24.
Propofol - Propofol is a potent, ultra-short-acting sedative agent, which has gained popularity for emergency department procedural sedation. It is a phenolic compound and is thought to mediate GABA activity. Propofol has no analgesic properties. Many characteristics of propofol made it attractive for emergency department procedural sedation, including rapid induction of sedation and an extremely short half-life, leaving the patient with no residual sedation soon after the procedure is over25. Although the use of propofol during PSA is increasing, some institutions across the world have restricted its use secondary to safety concerns. There have been concerns over the safety profile of propofol for PSA in ER due to the possibility of achieving a deeper than anticipated state of sedation and therefore encountering more serious complications, however recent literature have described increasing use of propofol for PSA in ER27-29. Weaver CS26 found in a study that ER PSA with propofol is safe. Similarly a systematic review conducted by Hohl CM30 et al found no significant difference in the safety profile and proportion of successful procedural sedation between midazolam and propofol, and also found propofol to be slightly more cost effective then midazolam because of its early recovery profile. Zed PJ31 et al in a prospective study found that when propofol is administered as a standardized protocol it is a safe and effective agent for PSA in ER, and is also associated with high patient and physician satisfaction. In a recently conducted randomized controlled trial, Miner JR32 et al concluded that ketamine and propofol are both safe and effective agents for procedural sedation in the ED, and the patients who received ketamine had higher rates of subclinical respiratory depression, higher rates of recovery agitation, and longer times to regain baseline mental status than patients who received propofol.
Etomidate - Etomidate is an ultrashort acting non-barbiturate imidazole derivative, which possesses little analgesic effect. Onset of action is usually within one minute when administered intravenously. The duration of effect is brief, lasting three to five minutes at standard dosages. Etomidate is metabolized rapidly by the liver, and the duration of effect may be longer in patients with liver failure33. The only contraindication to etomidate is hypersensitivity to the medication, but caution should be taken during pregnancy (etomidate is a pregnancy category C drug), and the general precautions regarding procedural sedation and patient selection also should be considered. Side effects are usually rare, and there is no histamine release and hence minimal cardiovascular effect. The medication has few to no hemodynamic effects, and its neutral cardiovascular profile is one of the most appealing aspects of this agent. Adrenocortical suppression has been reported after the use of a single bolus of etomidate34, but the significance of this effect is believed to be inconsequential 35 and whether the adrenocortical suppression is clinically significant remains controversial.
Muscle twitching generally is well tolerated, and emergence nausea and vomiting have been reported. Respiratory depression and hypoxia are possible. The incidence appears to be 3 to 15 percent 36-39. Patients have responded well to supplemental oxygen; in rare instances, patients have required bag-valve-mask-assisted ventilation36-38. Etomidate has been shown to be safe and effective for PSA, and is an excellent choice of agent 36-39.
Dexmedetomidine: Dexmedetomidine is an alpha2 agonist 4,5 and pharmacologically related to clonidine. Dexmedetomidine has an affinity for alpha2 receptors eight times greater than that of clonidine.6 It exerts its effects by binding to alpha2 receptors presynaptically and post synaptically in the locus ceruleus and in the spinal cord. It decreases the release of norepinephrine and suppresses sympathetic activity7 , which results in decreased heart rate and blood pressure. The sedation and anxiolytic properties are exerted when dexmedetomidine binds to alpha2 receptors in the locus ceruleus (a nerve cluster that lies near the brain's fourth ventricle) and analgesia produced by binding of the drug to adrenoreceptors in the spinal cord.7 Dexmedetomidine has been shown to be safe and effective as a sedating agent. It is comparable with propofol without the concerns raised with propofol use.9 Although dexmedetomidine preserves respiration, at higher doses it will decrease HR, cardiac output, stroke volume, and mean arterial pressures.16
Several drugs are also given as combinations for procedural sedation, which offers the combined advantages, helps to circumvent the possible side effects and may also lead to the reduction of total doses required:
1. Ketamine, atropine (or glycopyrrolate), and midazolam (benzodiazepine).
2.Â Midazolam and fentanyl
3.Â Systemic agents (propofol or etomidate) and analgesic
The combination of ketamine and atropine is used since, a common side effect of ketamine is to increase salivation and secretions; atropine counteracts it by decreasing the secretions.
The clinical effects of titration of oral medication for the purposes of sedation are unpredictable. Repeated dosing of orally administered sedative agents may result in an alteration of the state of consciousness deeper than the intent of the practitioner. Therefore, during PSA there must be one person available whose only responsibility is to monitor the patient and institute bag-mask ventilation and cardiopulmonary resuscitation if necessary10. Except in unusual circumstances; the maximum recommended dose of an oral medication should not be exceeded.
REVERSAL OF SEDATION: Rarely should reversal of agents be used in procedural sedation if the drugs are used appropriately. The commonly used agents are:
Naloxone- It is administered to antagonize opioid induced respiratory depression and sedation. It should be carefully titrated specially in patients who are opioid dependent since it may precipitate sudden severe pain as it also antagonizes the analgesic effect of opioid. It has a very fast onset of action with peak effect in 1-2 minutes and effect of total dose of 0.4 to 0.8 mg lasting for 1 to 4 hours. Incremental dose of 20 to 40 Âµg may be given every few minutes till the ventilation of the patient improves. Infusion rate between 3-10 Âµg/hr may be started if prolonged ventilatory depression is anticipated.40
Flumazenil- It's a pure benzodiapine antagonist, and can be used for reversal of benzodiapine sedation, with onset of action less than 1 minute and it promptly reverses the hypnotic effect of the benzodiazepines. The usual total dose is 0.6 to 1.0 mg which is usually given as a gradual titrated dose of 0.2 mg / minute until the desired level of reversal is achieved. It may also be given as an IV infusion if over dosage with a long standing benzodiazepine is suspected.41