Procedural Sedation and Analgesia

Key Concepts

- Safe, effective procedural sedation and analgesia requires high-level experience and sound protocols for patient selection and patient monitoring.
- After procedural sedation, patients should be discharged with and remain in the company of a responsible adult for 4 to 8 h after recovery.
- Propofol is the agent of choice for deep sedation in the emergency department but requires supplementation with an opioid analgesic when a painful procedure is planned.
- The absence of a preprocedure fasting period is not a contraindication to procedural sedation for an emergent or time-sensitive condition.
- Pulse oximetry is mandatory during sedation, and end-tidal CO ₂ should be monitored if moderate or deep sedation is planned. Oxygen should be administered to patients undergoing procedural sedation.

Foundations

Background and Importance

The performance of diagnostic and therapeutic procedures is common in emergency care. Many of these interventions are often associated with significant pain and anxiety. Procedural sedation and analgesia (PSA) is a fundamental and required skill for emergency clinicians and an integral part of the core training of emergency medicine residents. This chapter will focus primarily on PSA in the adult population; Chapter 157 provides specific guidance for PSA for children.

PSA improves patient care and satisfaction by relieving pain and anxiety and facilitating successful therapeutic or diagnostic procedures. ^, These include fracture or joint reduction, incision and drainage of abscesses, cardioversion, tube thoracostomy, lumbar puncture, complex wound repair, and imaging studies in uncooperative patients.

Many of the agents used for PSA have the potential to cause significant respiratory, cardiovascular, or central nervous system (CNS) depression. The Joint Commission (TJC), Centers for Medicare and Medicaid Services (CMS), American College of Emergency Physicians (ACEP), and American Society of Anesthesiologists (ASA) have produced expert consensus and evidence-based guidelines concerning the use of PSA ( Box 7.1 ). Although controversy continues about credentialing and oversight of PSA outside the operating room at some institutions, the advent of these guidelines has led to PSA becoming a common emergency department (ED) procedure. The adoption of PSA as a standard procedure in the ED has been further enhanced by the availability of shorter-acting more effective drugs, and noninvasive monitoring devices.

BOX 7.1

American College of Emergency Policy Statement on Procedural Sedation in the Emergency Department ^a

Adapted from American College of Emergency Physicians Policy Statement: Procedural sedation in the emergency department. June 2017.

The American College of Emergency Physicians recommends the following:

- Emergency physicians who have received the appropriate training and skills necessary to safely provide procedural sedation, such as board certification (ABEM/ABOEM) in emergency medicine or graduates of an ACGME accredited emergency medicine program, should be credentialed without additional requirements for procedural sedation.
- The decision to provide sedation and selection of the specific pharmacologic agents should be individualized for each patient by the emergency clinician and should not be otherwise restricted.
- Emergency physicians and staff are expected to be familiar with the pharmaceutical agents they use and be prepared to manage their potential complications.
- To minimize complications, the appropriate drugs and dosages must be chosen and administered in an appropriately monitored setting. Patient evaluation should be performed before, during, and after their use.
- Institutional and departmental guidelines related to the sedation of patients should include the selection and preparation of patients, informed consent, equipment and monitoring requirements, hospital staff training and competency verification, criteria for discharge, and continuous quality improvement.

a June 2017.

With the wide variety of patient populations and procedural needs, the ability to individualize PSA for each situation is a necessary skill. Knowledge of the characteristics of each sedative is essential but identifying patient characteristics that may increase the risk of adverse events during sedation is more critical in ensuring a safe and patient-centered sedation. This can be best achieved through detailed preprocedural patient assessment, protocols delineating the required personnel and equipment, specific drugs used (including their routes of administration, dosages, effects, interactions, and complications), considerations for special at-risk populations, and patient monitoring, recovery, and discharge criteria.

The following terms are important for understanding the concepts presented in this chapter:

Anxiolysis is a state of decreased apprehension concerning a particular situation in which the patient’s level of awareness does not change.
Analgesia refers to the relief of pain without the intentional alteration of mental status, such as occurs in sedation. An altered mental state may be a secondary effect of the medications administered for this purpose.
Dissociation is a trancelike cataleptic state induced by an agent such as ketamine and characterized by analgesia and amnesia. Protective reflexes, spontaneous respirations, and cardiopulmonary stability are retained. Sedation is a controlled reduction of environmental awareness.
Procedural sedation and analgesia is a technique of administering a sedative or dissociative agent, along with an analgesic, to induce a state that allows the patient to tolerate painful procedures while maintaining adequate spontaneous cardiorespiratory function. It is intended to result in a depressed level of consciousness that allows the patient to maintain oxygenation and airway control independently and continuously. The drugs, doses, and techniques used are not likely to produce a loss of the protective airway reflexes.

ASA currently recognizes a continuum of depth of sedation, consisting of four subgroups ( Fig. 7.1 )—minimal sedation, moderate sedation, deep sedation, and general anesthesia. A fifth category, dissociative sedation, has been adopted by ACEP ( Table 7.1 ).

Minimal sedation (anxiolysis) is a drug-induced state during which patients respond normally to verbal commands. Although cognitive functions and coordination may be impaired, ventilatory and cardiovascular functions are unaffected.
Moderate sedation and analgesia (formerly called conscious sedation ) refers to a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, auditory only or accompanied by light tactile stimulation. Reflex withdrawal from the painful stimulus is not considered a purposeful response. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is always maintained.
Dissociative sedation is a trancelike cataleptic state induced by the dissociative agent ketamine; it is characterized by analgesia and amnesia while protective airway reflexes, spontaneous respirations, and cardiopulmonary stability are maintained.
Deep sedation and analgesia describes a drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully after repeated or painful stimulation. The ability to maintain ventilatory function independently may be impaired. Patients may require assistance in maintaining a patent airway, and spontaneous ventilation may be inadequate. Cardiovascular function is usually maintained.
General anesthesia is a drug-induced loss of consciousness during which patients are not arousable, even with painful stimulation. The ability to maintain ventilatory function independently is impaired. Patients typically require assistance in maintaining a patent airway, and positive-pressure ventilation is required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired.

Fig. 7.1, Schematic Representation of the Sedation Continuum.

TABLE 7.1

Definition of Levels of Sedation and Analgesia

Parameter	Minimal Sedation (Anxiolysis)	Moderate Sedation and Analgesia (Conscious Sedation)	Deep Sedation and Analgesia	Dissociative Sedation	General Anesthesia
Responsiveness	Normal response to verbal stimulation	Purposeful response to verbal or tactile stimulation	Purposeful response to repeated or painful stimulation	Unarousable, even with painful stimulus	Unarousable, even with painful stimulus
Airway	Unaffected	No intervention required	Intervention may be required	Intervention may be required	Intervention often required
Spontaneous ventilation	Unaffected	Adequate	May be inadequate	Adequate	Frequently inadequate
Cardiovascular function	Unaffected	Usually maintained	Usually maintained	Elevated	May be impaired

The progression from minimal sedation to general anesthesia is a dynamic continuum that lacks distinct separation between stages. The transition from one level of sedation to the next is often difficult to predict and varies from patient to patient. The sedation continuum is not drug-specific, and levels from mild sedation to general anesthesia can be achieved with virtually all the PSA agents. Because of this, emergency clinicians administering PSA should be able to treat patients who are in at least one level greater than the intended level of sedation.

Anatomy, Physiology, and Pathophysiology

Pain experienced by sick and injured patients is the result of multiple pathways in the body. In general, a painful stimulus activates bodily receptors, which then initiates biochemical signals through peripheral and central neural pathways, ultimately ending in the interpretation and perception of pain in the brain. The pharmacologic treatment of this pain comes in many different forms, ranging from local or regional anesthetics directly injected into the affected area, to more systemic-acting analgesics, and finally to sedating or dissociating medications aimed at suppressing the overall central awareness of pain.

Each class of medication utilized in PSA has its own mechanisms of action to treat the perception of pain. The most well-known class of analgesics covered in this chapter is opioids. These medications act on systemic opioid receptors, inhibiting the central pain pathway, while also providing some level of sedation. More pure sedatives, like benzodiazepines, etomidate, and propofol, primarily act on central γ-aminobutyric acid (GABA) receptors, resulting in a decreased level of consciousness and a loss of awareness and of a sense of pain, instead of suppression of pain reception. Dexmedetomidine, another sedative, works on a different class of receptors known as alpha2-adrenoceptors, providing sedation and mild analgesia. Finally, ketamine, a potent analgesic and dissociative agent, produces its actions through antagonism of N-methyl-D-aspartate (NMDA) receptors. By understanding the mechanism of each medication, clinicians can develop a multimodal approach to PSA to ensure comfort and safety.

Management

Decision Making

The approach to procedural sedation requires evaluating conditions that may enhance or impede the effectiveness of procedural sedation. These factors include patient assessment, including the consideration of preprocedural fasting, appropriate personnel, supplies, and equipment, patient monitoring, and postprocedural recovery.

Patient Assessment

Although no outcome-based studies have demonstrated a clear benefit from presedation evaluation beyond vital signs, mental status, and airway and cardiopulmonary assessment, consensus guidelines have suggested that there may be an increased risk of adverse events in subsets of patients. These include patients at the extremes of age, patients with anatomic features predictive of challenging intubation or rescue bag-mask ventilation, and those with underlying significant disease states or impaired cardiopulmonary physiology. A patient’s general physical status is conventionally categorized according to the ASA’s classification system ( Table 7.2 ). Most practice guidelines require a history and focused physical examination be performed and documented before PSA. No routine diagnostic testing is needed before PSA, other than diagnostic testing driven by the patient’s current status, including comorbidities.

TABLE 7.2

American Society of Anesthesiologists Physical Status Classification

Class	Description	Examples	Sedation Risk
I	Normal, healthy patient	No past medical history	Minimal
II	Mild systemic disease without functional limitations	Mild asthma, controlled diabetes	Low
III	Severe systemic disease with functional limitations	Pneumonia, poorly controlled seizure disorder	Intermediate
IV	Severe systemic disease that is a constant threat to life	Advanced cardiac disease, renal failure, sepsis	High
V	Moribund patient who may not survive without procedure	Septic shock, severe trauma	Extremely high

The patient’s age, current illness or injury for which PSA is intended, comorbidities, previous experiences or problems with PSA or general anesthesia, drug allergies and current medications, and tobacco, drug, and alcohol use are reviewed and recorded. A directed physical examination focuses on the vital signs, heart and lungs, and evaluation of the airway to identify anatomic features of a potentially difficult airway (see Chapter 1 ).

A discussion including the risks, benefits, and potential side effects of PSA should be held with patients or their families before the procedure. Written consent is preferred unless this is not possible due to the patient’s clinical condition or access to the patient’s medical surrogate.

Not every patient is an appropriate candidate for PSA in the ED. Therefore, patient selection is essential for the safety of the sedation. Depending on the clinical circumstances, a patient with an anticipated difficult airway or ASA classification of III or IV may require additional clinical resources. These can include additional nursing support or additional providers with expertise in procedural sedation, including emergency clinicians or an anesthesiologist. At times, it may even be advisable to undertake the procedure in the operating room with anesthesia.

Preprocedural Fasting

Evidence supporting preprocedural fasting in PSA has been extrapolated from the literature on general anesthesia. To date, there have been no published outcome-based studies demonstrating an increased risk of aspiration after a liquid or solid meal and no studies showing a benefit of fasting before PSA. Additionally, while anesthesia guidelines provide more conservative fasting recommendations, procedures deemed to be urgent or emergent should not be delayed based on fasting time.

In 2014, ACEP endorsed a level B recommendation regarding preprocedural fasting. It stated that clinicians should not delay procedural sedation in adult or pediatric patients in the ED based on fasting time. The recommendation further noted that preprocedural fasting for any duration has not demonstrated a reduction in the risk of emesis or aspiration during procedural sedation and analgesia. A large 2018 pediatric study found no association between fasting time and serious adverse events, including clinically apparent aspiration.

Subsequent expert consensus statements emphasize considering the patient’s risk factors for aspiration, including severe underlying illness, obstructive sleep apnea, obesity, age less than 12 months, upper endoscopy as the procedure requiring sedation, or bowel obstruction, and incorporating this information into the choice of sedative agents and depth of sedation. ^,

Personnel

TJC and most institutional policies have suggested that PSA providers should have adequate training to administer the agents effectively and safely. This includes the skill to assess risk, dose, and administer medications appropriately, monitor the patient’s response to the medications, and manage all potential complications, in particular airway complications. This generally implies that PSA in the ED should be supervised by an emergency clinician or other appropriately trained and credentialed physician. It is also recommended that a qualified support person (e.g., nurse, respiratory therapist) able to recognize and respond to the complications of PSA be present for continuous monitoring of the patient. Although they may assist with minor interruptible tasks, they should focus on the patient’s status and not have any other responsibilities that would interfere with monitoring and documentation from the start of the procedure to completion of the recovery phase.

Devices and Techniques

Supplies and Equipment

PSA may result in an allergic reaction, oversedation, respiratory depression or, rarely, cardiopulmonary arrest. The incidence of these complications depends on patient selection, drugs used, rate and dosage of administration, and specific patient sensitivities. Consequently, appropriate equipment to monitor the patient’s condition continually, manage airway complications, allergic reactions, and drug overdoses, and treat respiratory or cardiopulmonary arrest should be readily available. Supportive equipment includes oxygen, suction, patient-monitoring devices, basic and advanced airway management equipment, a defibrillator, advanced life support medications, reversal or rescue agents, and vascular access equipment ( Box 7.2 ).

BOX 7.2

Equipment for Procedural Sedation and Analgesia

ECG, Electrocardiogram.

High-flow oxygen source
Suction
Airway management equipment
Monitoring equipment
Pulse oximeter
ECG monitor, defibrillator, transcutaneous pacemaker
Blood pressure monitor
Capnography ^a

a Capnography carries a level B recommendation by the American College of Emergency Physicians for use as an adjunct to pulse oximetry and clinical assessment to detect early hypoventilation. It is also recommended by the American Society of Anesthesiologists for monitoring the presence of exhaled carbon dioxide during moderate or deep sedation, in addition to the continual observation of qualitative clinical signs of adequate ventilation.
Vascular access equipment
Reversal agents
Resuscitation drugs
Adequate staff

With rare exceptions, PSA medications in adult patients should be administered via the intravenous (IV) route. Adults undergoing PSA in the ED should therefore have an IV line placed before the procedure. This need in children is less clear and depends on the presence of comorbid conditions and choice and route of drug to be administered. In children, if the procedure is likely to be lengthy or if multiple doses of drugs will be needed, a peripheral IV line is recommended.

While the requirement for supplemental oxygen, and its benefits during PSA, have not been well studied, emergency department data does suggest its use decreases the incidence of hypoxemic episodes during procedural sedation. ^, However, significant respiratory depression in these patients may not be detected because of their normal oxygen saturation. The routine use of capnography eliminates this issue, since ventilatory status is displayed continuously, and is recommended for any planned procedure using more than light levels of sedation or anxiolysis.

The most crucial aspect of monitoring during PSA is the visual observation and assessment of the patient, especially the response to medications and procedures. The patient’s ability to follow commands in response to varied levels of stimulation is useful in quantifying the level of consciousness. Furthermore, the patient’s ventilatory rate may be readily assessed by direct observation, although depth of respiration or tidal volume is harder to estimate clinically. Pulse oximetry is a reliable and essential monitoring modality. Other components of monitoring, which should be documented, include determination of respiratory rate, heart rate, blood pressure, oxygen saturation, cardiac rhythm, and capnography.

ASA and Joint Commission standards have historically required responsive-based assessments for documenting depth of sedation and a measure for assessing patient comfort. A 2019 ACEP practice guideline on unscheduled procedural sedation challenges this concept as an adequate metric and encourages strong consideration for the incorporation of ventilation-focused assessments as a measure of sedation adequacy. The consensus guideline recommends focusing on respiratory capacity instead of responsiveness alone as a means to enhance patient safety across sedative agents.

Although there is no outcome-based evidence that cardiac monitoring during PSA is of any benefit, it is certainly not harmful, is routinely available, and may be beneficial in some instances. It should be used routinely in older patients and patients with a history of cardiovascular disease, hypertension, or dysrhythmia. Although in young, healthy patients, continuous pulse oximetry alone may be safe (as this will also display the heart rate), we recommend that cardiac rhythm monitoring, if available, should be used in all adult cases.

Capnography (or capnometry) measures end-tidal carbon dioxide (CO ₂ ) partial pressure and has been shown to detect cases of inadequate ventilation earlier than clinical assessment or detection of hypoxemia by oximetry. While the pooled evidence for capnography has not shown a benefit in patient outcomes, studies have demonstrated that its use can significantly reduce hypoxemic events during procedures. ^, This, in addition to its lack of harm, ease of use, and increasingly low cost have resulted in most sedation oversight organizations recommending its use. In its 2018 guidelines, the ASA recommended continually monitoring ventilatory function with capnography unless precluded or invalidated by the nature of the patient, procedure, or equipment. The 2014 ACEP guidelines, further supported by more recent organizational statements, endorsed a level B recommendation that capnography may be used as an adjunct to pulse oximetry and clinical assessment to detect hypoventilation and apnea earlier than pulse oximetry or clinical assessment alone in patients undergoing procedural sedation and analgesia in the ED. ^,

We recommend that continuous capnography be used when deep sedation is planned due to the inherent risk of respiratory depression. Although optional when only light sedation or anxiolysis is planned, capnography may enhance patient safety by allowing the observer to recognize unintended oversedation and depression of respiratory rate or volume more rapidly.

The bispectral index (BIS) is monitored via a noninvasive device attached to the patient’s forehead and determines the depth of sedation level via frontal lobe electroencephalographic measurements. It has been used in the operating room as an objective measure of sedation depth. Though ED studies have revealed a correlation between BIS readings and objective patient sedation levels, no reliable advantage or beneficial role has been demonstrated to support its routine use in PSA monitoring.

When transporting patients outside the ED for diagnostic procedures requiring PSA, every attempt should be made to provide the same level of monitoring during the transport and procedure as would be used within the department.

The highest risk of serious adverse events generally occurs within 5 to 20 minutes of receiving the last dose of IV medication and at the completion of procedures, when the patient remains sedated but is no longer receiving the painful stimulus. Similarly, patients undergoing lengthy procedures in which deeper sedation is desired to reduce motion (e.g., magnetic resonance imaging [MRI]) are also at an increased risk. Patients should be monitored closely at these times, and this should continue until clinical recovery has occurred.

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