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Procedural sedation and/or anesthesia is frequently used in the emergency department (ED) to provide patient anxiolysis, analgesia, and amnesia so that uncomfortable procedures may be performed without administering general anesthesia. Although pediatric sedation may be used to achieve urine catheterization or to obtain intravenous (IV) access, in adults, sedation is not typically used for such minor procedures.
For example, minimal sedation may be used in adults for a lumbar puncture or for an ankle arthrocentesis. Moderate sedation may be required for a large abscess incision and drainage or a multilayer repair of a complex laceration. Deep sedation should be used when full muscle relaxation is required for a procedure, and it is most appropriate for joint reductions and cardioversions.
As procedural sedation becomes safer with more available drug options and more advanced monitoring, its use is likely to increase in frequency in outpatient settings such as EDs.
Adapted image of a posterior shoulder dislocation courtesy of Wikimedia Commons/Hellerhoff.
Prior to using procedural sedation in a patient, healthcare providers should evaluate the patient's clinical state and determine the likelihood of complications from sedation. Important information to obtain with the patient's medical history are current medical conditions, current medications, previous reactions to anesthesia, medication/drug allergies, and time of last oral intake. Clinicians should also perform a physical examination and review pertinent laboratory findings.
The American Society of Anesthesiologists (ASA) physical status classification system is often used as a surrogate for evaluating a patient's underlying burden of disease and determining the possibility of complications arising from sedation in the ED. ASA class may be assessed following a thorough clinical evaluation.
A large body of evidence demonstrates that the likelihood of adverse events can be correlated to ASA class.[1] Patients with higher ASA classes are more likely to experience hypoxia, apnea, and need for invasive airway management. Thus, although sedation can be safe even in higher ASA classes,[2] clinicians should discuss the benefits and risks of sedation with these patients or the patients' surrogates and take extra precautions when sedating such patients.
Table courtesy of Nicole Cimino-Fiallos, MD.
Procedural sedation has allowed clinicians to manage injuries and illnesses that previously would have required treatment in the operating room. However, it may not be safe to sedate certain patients in the ED, as they may be better served under the care of an anesthesiologist in the operating room. The elderly often fall into this group.
Geriatric patients are more likely to experience hypoxic events following sedation—as well as hypotension and airway complications—than those in younger age groups, although the difference does not appear to be statistically significant.[3] Seniors also often receive reduced dosages of sedative medications and may thereby be undersedated.
Clinicians considering sedation of patients from older patients must be aware of the potential for an increased risk of complications. More research is needed to determine whether sedation of the elderly in the ED can be made more safe.
Image of a sonography-guided femoral nerve block courtesy of Wikimedia Commons/PhilippN.
Time of last oral intake is an important concern when procedural sedation is being considered. However, controversy remains regarding the safety of performing this technique following oral intake, as patients with full stomachs are at risk for emesis and aspiration.
The American College of Emergency Physicians (ACEP) supports the use of sedation for emergent procedures regardless of the time of last oral intake.[4] Delay is not recommended for emergent procedures even for an inadequate fasting time[4,5]; however, if a procedure can be delayed to increase the time between the sedation and last oral intake, a longer wait time should be considered. If clinicians feel the risk of aspiration is too high during procedural sedation, then the patient should be intubated or transferred to the operating room for management.
Drug selection for procedural sedation may alter the risk of emesis and aspiration. For example, ketamine may increase the risk of aspiration and thus may not be the ideal choice for patients with recent oral intake; however, clinicians may consider premedicating sedation with an antiemetic.
Note that patients with significant comorbidities have an increased risk of aspiration; therefore, alternatives to procedural sedation should be considered if fasting has not occurred.[5]
Spot view from a fluoroscopic examination showing aspiration in an elderly stroke patient courtesy of Gossner J, Nau R. Radiol Res Pract. 2013;2013:584793. [Open access.] PMID: 23936651, PMCID: PMC3713368.
Clinicians qualified to perform the sedation are also those who are aware how to prepare for it. Being well prepared for potential complications is crucial for a safe sedation. The important ABCDEs of sedation include airway, breathing, cardiac monitor, drugs, and end-tidal carbon dioxide (CO2) and oxygen (O2).
Procedural sedation should be performed in a room that is ready for resuscitation.[6] A defibrillator should be present for any patient with cardiovascular disease, and equipment for rapid sequence intubation (RSI) should be readily available. Place the airway cart at the patient's bedside, and set up the appropriate laryngoscope and endotracheal (ET) tubes in advance. Connect the bag-valve mask to oxygen, and position it nearby. The patient should also be connected to a cardiac monitor, and the blood pressure should be cycled every 3-5 minutes throughout the sedation.
Carefully calculate and measure medication dosages. Patient weight should be accurate and converted to kilograms. Paralytic drugs should also be ready and available in the event that RSI is required; calculate the appropriate dose of the paralytic agent prior to performing the sedation. Place end-tidal CO2 monitoring and a pulse oximeter on the patient.
Image courtesy of Dreamstime/Ruslan Kerimov.
Levels of sedation range from minimal to deep, and they continue along a spectrum.[7] Clinicians may use a modified Ramsay sedation scale to evaluate the depth of their patient's sedation and thereby prevent inadvertent general anesthesia. The modified scale ranges from 1 to 6, with 1 representing an agitated patient and 6 representing an unresponsive patient.[6,8]
Minimal sedation is often administered for anxiolysis or pain control.[7] Moderate sedation, sometimes called conscious sedation, is used to make patients sleepy but arousable with voice commands. When deep sedation is used, patients will only respond to painful stimuli.[7]
Use the least amount of sedation required to complete the procedure. Different medications will provide different levels of sedation; thus, clinicians should carefully select sedative agents for the desired effect.
Image courtesy of Nicole Cimino-Fiallos, MD.
Oxygen administration during procedural sedation has been controversial. Prior to the availability of end-tidal CO2 monitoring, clinicians used a dropping pulse oximeter reading to identify apnea, as well as provided oxygen via a nasal cannula. However, this prolonged the time to a decrease in pulse oximeter readings and was therefore discouraged.
Episodes of hypoxia are not safe for the patient; unfortunately, once desaturation occurs, the oxygen level will continue to drop precipitously. Thus, the ASA recommends oxygenation for all patients undergoing sedation procedures and strongly recommends its use for deep sedations.[9]
Use of a high-flow nasal cannula has been studied and validated as another technique to reduce the incidence of hypoxia during a procedural sedation.[10] Consequently, if patients have an episode of apnea and require intubation, they will already be preoxygenated if wearing a nasal cannula or facemask for the sedation.
Image courtesy of Wikimedia Commons/James Heilman, MD.
End-tidal CO2 monitoring during procedural sedation in the ED may soon be considered standard of care. This noninvasive technique tracks the patient's ventilatory status and detects subtle respiratory depression during procedural sedation.
Capnography monitoring helps to reduce apneic periods and prevent apnea from progressing to hypoxia by alerting clinicians that the patient is not ventilating and may soon fail to oxygenate.[11] Capnography has been shown to be more effective at identifying respiratory depression and hypoventilation than clinical examination or other standard monitoring.[11,12]
If a patient has an end-tidal CO2 change from baseline of 10 mmHg or greater,[11] clinicians should be concerned about respiratory depression and intervene with a jaw thrust maneuver, bag-valve mask ventilation, or even invasive airway management.
Image of a normal capnogram courtesy of Bhagat H, Agarwal A, Sharma MS. J Brachial Plex Peripher Nerve Inj. 2008;3:14. [Open access.] PMID: 18498657, PMCID: PMC2412847.
If a patient becomes oversedated or experiences respiratory depression, clinicians should attempt arousal maneuvers such as yelling the patient's name or performing a sternal rub. Other painful stimulation techniques include nail-bed pressure or noxious smells (eg, ammonia).
If the patient does not arouse, attempt a jaw thrust maneuver to improve respiration and also wake the patient. With the patient supine, the clinician should use both hands to position the fingers behind the angle of the mandible and pull toward the ceiling. This method improves airway positioning and also acts as a painful stimulus.
If the patient continues to hypoventilate, use a bag-valve mask for ventilation.[13] Ideally, one person holds the mask to the patient's face, creating a tight seal, and a second person squeezes the bag. End-tidal CO2 monitoring can guide the rate of ventilation.
If the patient continues to remain unresponsive and is failing to ventilate, RSI must be performed.
Image courtesy of Lim D, Bartlett S, Horrocks P, Grant-Wakefield C, Kelly J, Tippett V. BMC Med Educ. 2014;14:138. [Open access.] PMID: 25004792, PMCID: PMC4099026.
Benzodiazepines and opiates are the most common medications used for minimal sedation. Both drug classes may cause drowsiness. Respiratory depression and hypotension are also possible, but they occur more frequently at higher dosages. Benzodiazepine- and/or opiate-naïve patients are likely to be more sensitive to these medications; therefore, cautious dosing is required.
Midazolam and lorazepam are frequently used benzodiazepines. Midazolam should be dosed at 0.01-0.2 mg/kg IV at a time, with a maximum dose of 5 mg IV. Lorazepam should be dosed at 0.1 mg/kg IV at a time, up to 2 mg IV; this drug can be titrated every 5 min, as needed.
Fentanyl and morphine are commonly used opiates. Fentanyl is up to 100 times more potent than morphine but offers less hypotension and less histamine release than morphine; fentanyl also requires more frequent re-dosing.[14]
Flumazenil[15] and naloxone, respectively, are the reversal agents for benzodiazepines and opiates[16]; these agents should be available whenever these benzodiazepine and/or opiate sedative agents are used.
Image courtesy of Wikimedia Commons/DiverDave.
Moderate sedation can be achieved with a variety of medications, most popularly with benzodiazepines. The benzodiazepine class provides amnesia for procedures but does not add any analgesic properties.
Although midazolam is also commonly used for moderate sedation, it is difficult to titrate and may take several minutes (3-5 min) to become effective.[17] The patient is likely be drowsy, with recovery from the sedation possibly requiring up to 1 hour. Midazolam is frequently combined with fentanyl for sedation and analgesia; however, this combination may increase the risk of hypotension and respiratory depression.
Keep reversal agents for benzodiazepines and opiates readily available in the event the patient becomes oversedated. However, avoid reversal of benzodiazepines in patients who routinely use this class of medication, as reversal may precipitate seizures.
Occasionally, etomidate is also used for moderate sedation, because it provides good muscle relaxation and has a short duration of action (approximately 3-5 min). However, this drug can also cause masseter spasm and myoclonus. Initially, adrenal suppression was a frequently feared complication, but it appears to occur more frequently with continuous infusion in critically ill, septic patients.[18]
Image of a novel responsiveness index sedation monitor courtesy of Kaila M, Everingham K, Lapinlampi P, et al. Crit Care. 2015;19:333. [Open access.] PMID: 26370687, PMCID: PMC4570737.
Propofol is the most commonly used agent for deep sedation; its advantages include quick onset of action and fast recovery. Studies have shown that sedation with propofol as compared to midazolam and ketamine provides a shorter postprocedure recovery time and a shorter time to discharge in the ED.[6]
The initial IV dose is 1 mg/kg; repeat doses of 0.5 mg/kg may be used to titrate and/or prolong the sedation. Propofol provides amnesia but not analgesia and thus is often combined with an analgesic agent. The combination tends to relax the patient's musculature, making it ideal for joint reductions.
Adverse effects of propofol include pain at the infusion site and, potentially, apnea, hypotension, and loss of airway reflexes. However, the adverse effects are generally short-lived.
Image courtesy of Science Photo Library/Dr P Marazzi.
Ketamine, a derivative of phencyclidine (PCP), has become a popular ED sedative agent owing to its relatively short duration of action (20-30 min) and analgesic and amnestic effects, while allowing patients to maintain their airway reflexes and respiratory drive. This drug uniquely provides patients with a dissociative sedation, characterized by catalepsy, catatonia, analgesia, and amnesia, with or without loss of consciousness.[19] The recommended dose is 1-2 mg/kg IV.
Once dissociated, patients develop nystagmus. Ketamine may also cause adverse reactions such as laryngospasm, hypersalivation, and vomiting.
Emergence reactions are a frequently feared adverse event associated with ketamine in which patients may experience effects such as agitation, hallucinations, and/or unpleasant dreams as they recover from sedation.[20] These phenomena appear to be more common in adults and, anecdotally, may be prevented by encouraging the patient to think of a pleasant memory prior to sedation. Most ketamine emergence reactions may be preventively treated with small doses of midazolam.[20]
Image courtesy of Wikimedia Commons/Psychonaught.
In response to clinicians' concerns about the hypotension caused by propofol administration and the vomiting that can occur from ketamine use, some healthcare providers recommend ketofol, a combination of both drugs, for procedural sedation. This combination was initially proposed because ketamine causes hypertension and propofol acts as an antiemetic; it was thought that mixing the two agents would thus prevent the most common adverse events of these medications. Studies have borne that out: When propofol and ketamine were combined, the incidence of agitation, apnea, hypoxia, bradycardia, hypotension, and vomiting was lower than that of each medication alone.[21] However, no studies have shown improved outcomes with ketofol.
To prepare ketofol, dilute ketamine by 10-fold from 100 mg/mL to 10 mg/mL.[22] Use this dilution to make a 1:1 mixture with propofol (also at a 10 mg/mL concentration) in the same syringe. Administer a 1 mg/kg dose of the mixture to the patient. Precaution: Carefully calculate these dilutions and mixtures, as an error in dosing could cause an adverse event.
Images courtesy of Wikimedia Commons/Erich Schulz (left) and the US Drug Enforcement Agency (right).
Patients with multiple comorbidities such as significant underlying cardiopulmonary disorders or high injury severity at the time of sedation (eg, multi-trauma, head trauma) are at greater risk for complications during procedural sedation than their healthier counterparts. Complications may include laryngospasm, intubation, and aspiration. However, it appears that emergent medical intervention is not commonly required for severe adverse events, and rarely do respiratory events result in serious adverse outcomes, such as aspiration, unplanned intubation, or cardiac arrest.[21]
Most adverse events in the setting of procedural sedation start with hypoventilation/apnea or hypoxia and then progress to respiratory failure. The use of oxygen and end-tidal CO2 monitoring may alert clinicians to the precursors of these events and provide an opportunity to make adjustments to prevent further complications as well as avert the need for escalation of care. Other adverse events include cardiovascular depression, hypotension, agitation, bradycardia, and vomiting.
As noted earlier, ketamine may cause laryngeal spasm, but this usually responds to bag-valve mask ventilation. Etomidate, when used for sedation, can cause masseter spasm, which will require intubation, but such a measure is exceedingly rare.[21]
Image courtesy of Science Photo Library/Dr P Marazzi.
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