Systemic Analgesia and Sedation for Procedures

Terminology

The progression from minimal sedation to general anesthesia is a nonlinear continuum that does not lend itself to division into arbitrary stages. Low doses of opioids or benzodiazepines induce mild analgesia or sedation, respectively, with little danger of adverse events. If, however, clinicians continue administering additional medication beyond this initial level, progressively altered consciousness ensues with a proportionately increased risk for respiratory and airway complications. If further medications are administered, the patient will advance along this continuum until protective airway reflexes are lost and general anesthesia is ultimately reached. This continuum of sedation is not drug specific in that varying states from mild sedation to general anesthesia can be achieved with virtually all nondissociative PSA agents (e.g., opioids, benzodiazepines, barbiturates, etomidate, propofol).

In 1985, the American Academy of Pediatrics (AAP) and the National Institutes of Health issued guidelines for the management and monitoring of children receiving sedation for diagnostic and therapeutic procedures in response to the growing use of opioids and sedative-hypnotic agents in the outpatient setting and a number of sedation-related deaths. In these documents, three levels of sedation were defined (conscious sedation, deep sedation, and general anesthesia) to create a common language for describing drug-induced alterations in consciousness ( Box 33.1 ). A key development in the field of PSA has been revision of the original terminology and adoption of clearer descriptions of varying types and degrees of sedation (see Box 33.1 ). Though historically popular, the widely misinterpreted and misused term “conscious sedation” has fallen into disfavor ; it has been labeled as “confusing,” “imprecise,” and an “oxymoron” and has been replaced with the term “moderate sedation.”

Despite improvements in PSA terminology, the system is imperfect and there is still no objective way to assess the depth of sedation. Levels of responsiveness remain at best crude surrogate markers of respiratory drive and retention of protective airway reflexes. This is especially true for all levels of sedation in young children (infants and toddlers) who do not understand or are unreliable in following verbal commands. Although respiratory depression and respiratory arrest can be detected quickly with standard interactive and mechanical monitoring, there is no safe and practical way to assess the status of protective airway reflexes. Data are currently insufficient to determine whether deep sedation is associated with impairment of protective reflexes or whether such danger is encountered only when “pushing” deep sedation to the point at which it approaches or reaches general anesthesia.

PSA Guidelines

Before the promulgation of PSA guidelines by specialty societies and governmental agencies, clinicians simply administered sedatives in varied clinical settings and used individual judgment to determine the need for specific monitoring devices and supporting personnel. Since 1985, at least 27 sets of PSA guidelines have been published, each crafted for the unique and differing settings in which PSA is practiced. Naturally, not all are in agreement. The intent of each of these guidelines is to better standardize the manner in which PSA is performed to enhance patient safety. Those most pertinent to emergency clinicians are from the American College of Emergency Physicians (ACEP), the AAP, and the American Society of Anesthesiologists (ASA).

In the early 1990s, the Joint Commission on Accreditation of Healthcare Organizations, an independent, not-for-profit organization that evaluates and accredits hospitals in the United States, took a special interest in PSA, with the central theme being that the standard of sedation care provided should be comparable throughout a given hospital. Thus, patients sedated in the emergency department (ED) should not receive a significantly different level of attention or monitoring than those sedated for a similar-level procedure in the operating room or in the endoscopy suite. To ensure this, the Joint Commission requires specific PSA protocols to be applied consistently throughout each institution. These hospital-wide sedation policies will vary from site to site based on the specific needs and expertise available within each institution. In 2001, the Joint Commission released new standards for pain management, sedation, and anesthesia care.

At each hospital accreditation survey the Joint Commission determines whether practitioners practice PSA consistent with their hospital-wide sedation policy and whether they provide sufficient documentation of such compliance. Clinicians must be familiar with their hospital's sedation policies and should work with their medical staff to ensure that such policies are suitably detailed, yet reasonable and realistic. Unduly restrictive policies do a disservice to patients by discouraging appropriate levels of analgesia and sedation. Most hospitals pattern their sedation policies after the Joint Commission standards and definitions. It is important to note that the unique ketamine dissociative state does not fit into the existing Joint Commission definitions of sedation and anesthesia. A ready solution is to assign a distinct definition for “dissociative sedation” (see Box 33.1 ).

The Joint Commission requires that PSA practitioners who are permitted to administer deep sedation be qualified to rescue patients from general anesthesia. Emergency clinicians typically perform all levels of sedation except general anesthesia. Moderate sedation suffices for the majority of procedures in adults and cooperative children, although it will not be adequate for extremely painful procedures (e.g., hip reduction, cardioversion). Deep sedation can facilitate such procedures, but with greater risk for cardiorespiratory depression than is the case with moderate sedation. Moderate sedation is frequently insufficient for effective anxiolysis and immobilization in younger, frightened children, and deep or dissociative sedation is an appropriate alternative.

The Centers for Medicare & Medicaid Services (CMS) has published similar requirements for hospital anesthesia services that also includes the provision of PSA throughout a given institution. Health care institutions wishing to bill Medicare must adhere to these guidelines and provide supporting documentation when requested. In 2011, CMS issued revised guidelines to help clarify various provisions of their anesthesia services requirements. The new CMS guidelines emphasize that hospital policies governing the provision of anesthesia services (including PSA) must be based on nationally recognized guidelines; the source of these guidelines may include a number of specialty organizations, including ACEP. CMS also notes that “The ED is a unique environment where patients present on an unscheduled basis with often very complex problems that may require several emergent or urgent interventions to proceed simultaneously to prevent further morbidity or mortality,” and that, “…emergency medicine-trained physicians have very specific skill sets to manage airways and provide the ventilation necessary for patient rescue. Therefore these practitioners are uniquely qualified to provide all levels of analgesia/sedation and anesthesia (moderate to deep to general).”

Evaluation Before PSA

The practice of PSA has three essential components performed in sequence: the initial presedation evaluation, sedation during the procedure, and postprocedure recovery and discharge from the ED. In all but the most emergency situations, perform a directed history and physical examination before PSA. If this evaluation suggests additional risk, reconsider the advisability of sedation. High-risk cases may be better managed in the more controlled environment of the operating room.

Presedation assessment is a Joint Commission requirement, and most hospitals have developed specific forms to facilitate consistent documentation of the required items. In general, however, all the appropriate parameters are already documented in the general ED record or are obvious by simply evaluating the patient's complaint. Except in emergency situations, discuss the risks, benefits, and limitations of any PSA with the patient or parent or guardian in advance and obtain verbal agreement. Formal written informed consent is not required as a standard of care (but may be an institutional requirement), although documentation, as discussed earlier, is essential.

Gastrointestinal

Assess the time and nature of the last oral intake because pulmonary aspiration of gastric contents may occur if the patient vomits when protective airway reflexes are impaired. Fig. 33.1 shows a four-step assessment tool to stratify the risk for aspiration before sedation and to identify prudent limits of targeted sedation, although this tool has not yet been validated.

More conservative guidelines from the ASA for elective surgery or procedures in healthy patients specify an age-stratified fasting requirement of 2 to 3 hours for clear liquids and 4 to 8 hours for solids and nonclear liquids. Nonetheless, they acknowledge that, regarding PSA, “the literature provides insufficient data to test the hypothesis that preprocedure fasting results in a decreased incidence of adverse outcomes.” Since these guidelines were published, multiple ED studies comparing fasting times in both pediatric and adult patients undergoing PSA failed to demonstrate a significant difference in the rates of emesis or aspiration and no other serious adverse events resulting from emesis or aspiration were identified.

The concept of preprocedure fasting is logistically difficult or impossible for emergency clinicians, who have no control over patients' oral intake before arrival at the ED. In actual practice, emergency clinicians routinely perform PSA safely on patients who are noncompliant with the ASA elective-procedure fasting guidelines. Procedures can sometimes be delayed for several hours; however, this must be balanced against prolongation of pain and anxiety in the patient, inconvenience for the patient and family, and expenditure of room space and other finite ED resources. In addition, many ED procedures require urgent if not immediate attention (e.g., débridement and repair of animal bite wounds, acute burn management, arthrocentesis for suspected septic arthritis, reduction of joint dislocations, lumbar puncture in an uncooperative septic patient, hernia reduction, eye irrigation for ocular trauma or chemical burns, cardioversion in a hemodynamically unstable patient). Though uncommon, there may be occasions in which nonfasting patients require urgent procedures with a substantial depth of sedation that may be more safely managed in the operating room with endotracheal intubation to protect the airway.

Selecting agents that are less likely to produce vomiting, such as fentanyl instead of morphine or meperidine, may decrease the potential for aspiration. Concomitant antiemetic administration is an unproven adjunct but a common consideration. In summary, common sense should apply and clinical judgment should prevail, but it is standard for PSA to be performed in the ED on patients in the nonfasting state.

Personnel and Interactive Monitoring

The most important element of PSA monitoring is close and continuous observation of the patient by an individual capable of recognizing complications of sedation ( Fig. 33.2 ). This person must be able to continuously observe the patient's face, mouth, and chest wall motion. Equipment or sterile drapes must not interfere with such visualization. Such careful observation allows prompt detection of adverse events such as respiratory depression, apnea, partial airway obstruction, emesis, and hypersalivation.

PSA personnel should understand the pharmacology of analgesic and sedative agents and their respective reversal agents. They must be proficient in maintaining airway patency and assisting ventilation if needed. PSA requires a minimum of two experienced individuals, most frequently one clinician and one nurse or respiratory therapist. The clinician typically oversees drug administration and performs the procedure, whereas the nurse or respiratory therapist continuously monitors the patient for potential complications. The nurse or respiratory therapist should also document the medications administered and the response to sedation and measure vital signs periodically. The nurse or respiratory therapist may assist in minor, interruptible tasks but must remain focused on the patient's cardiopulmonary status, and this responsibility must not be impaired. An individual with advanced life support skills should also be immediately available, which is a requisite easy to fulfill in the ED setting.

During deep sedation, the individual dedicated to patient monitoring should have experience with this depth of sedation and no other responsibilities that would interfere with the advanced level of monitoring and documentation appropriate for this degree of sedation. Individual hospital-wide sedation policies may have additional requirements regarding how and when deep sedation is administered based on the patient's specific needs and the clinician's expertise.

It is not mandatory to have intravenous (IV) access in situations in which sedation is administered by the intramuscular (IM), oral, nasal, inhalational, or rectal routes, but it may be preferable based on the anticipated depth of sedation, comorbid conditions, or additional drug titration. When sedation is performed without IV access, an individual skilled in initiating such access should be immediately available.

Equipment and Mechanical Monitoring

The routine use of mechanical monitoring has greatly enhanced the safety of PSA. With current technology, oxygenation (via pulse oximetry), ventilation (via capnography), and hemodynamics (via blood pressure and electrocardiogram [ECG]) can all be monitored noninvasively in nonintubated, spontaneously breathing patients.

Supplemental Oxygen

Substantial variation in practice exists with regard to the use of supplemental oxygen during PSA. The premise is a logical one: increasing systemic oxygen reserves should naturally delay, or perhaps avert, hypoxemia should an airway or respiratory adverse event occur. However, the price paid for this well-intentioned safeguard is the loss of pulse oximetry as an early warning device. Hyperoxygenated patients will desaturate only after the apnea is prolonged. Indeed, the time required for preoxygenated, apneic, healthy adults and adolescents to desaturate to 90% averages more than 6 minutes.

Deitch and colleagues have shown in a series of randomized controlled trials that high-flow supplemental oxygen decreases the incidence of hypoxia during propofol sedation (number needed to benefit of 4), whereas lesser amounts of oxygen (3 L/min) do so only marginally with propofol and not at all with lighter levels of sedation. Thus, high-flow oxygen is strongly recommended with propofol or other deep sedation, assuming that interactive monitoring includes capnography to promptly identify respiratory depression. For lighter levels of sedation, supplemental oxygen has no established benefit and may impair detection of respiratory depression when using pulse oximetry without capnography.

Discharge Criteria

Monitor all patients receiving PSA until they are no longer at risk for cardiorespiratory depression ( Table 33.2 ). Before discharge be sure that patients are alert and oriented (or have returned to an age-appropriate baseline) with stable vital signs. Many hospitals have chosen to use standardized recovery scoring systems similar to those used in their surgical postanesthesia recovery areas ( Table 33.3 ). Although no generally accepted minimum durations for safe discharge have been established, one large ED study found that, in children with uneventful sedation, no serious adverse effects occurred more than 25 minutes after final medication administration. This suggests that in most cases, prolonged observation beyond an hour is unlikely to be necessary.

Make sure that all patients leave the hospital with a reliable adult who will observe them after discharge for postprocedural complications. Document the name of the individual in the hospital record. Give written instructions regarding appropriate diet, medications, and level of activity ( Boxes 33.2 and 33.3 ). Even though patients may appear awake and able to comprehend instructions, they may not remember details once they leave the ED.

To be eligible for safe discharge, children are not required to walk unaided or demonstrate that they can tolerate an oral challenge because most PSA agents are emetogenic. Forcing fluids after sedation can lead to emesis before or after discharge. The AAP guidelines require only that “the patient can talk (if age-appropriate)” and “the patient can sit up unaided (if age-appropriate).” When infants and young children are discharged after their evening bedtime, caution parents to position the child's head in the car seat carefully. Significant forward flexion might cause airway obstruction if the child falls asleep on the way home.

General Principles

Therapeutic mistakes that result in inadequate analgesia and sedation include using the wrong agent, the wrong dose, the wrong route or frequency of administration, and poor use of adjunctive agents. With proper training and technique, adequate PSA can be provided in almost any circumstance. Understanding titration principles is critical to providing safe and effective PSA. Clinicians must have a thorough knowledge of the pharmacokinetics, dosing, administration, and potential complications of the PSA agents that they use. Time of onset from injection to the initial observed effect must be appreciated, especially when using drugs in combination, to avoid stacking of drug doses and oversedation.

The correct agent (or combination of agents) and the route and timing of administration depend on the following factors: How long will the procedure last? Will it be seconds (e.g., simple relocation of a dislocated joint, incision and drainage of a small abscess, cardioversion), minutes (e.g., complex manipulation of a fracture for reduction, breaking up loculations in a large abscess and then packing it), or prolonged (e.g., complex facial laceration repair)? How likely is it that the procedure will need to be repeated (e.g., fracture reduction)? Can topical, local, or regional anesthesia be used as an adjunct? Does the patient require sedation only for a noninvasive diagnostic imaging study?

Before drug administration, every effort should be made to minimize a patient's anxiety and distress, particularly in children. The emotional state of a patient on induction strongly correlates with the degree of distress on emergence and in the days immediately after the procedure. Avoid being pressured by consultants to cut corners or rush PSA. Incorporating into the presedation preparation a discussion with the consultant about the sedation plan and the length of time required to safely prepare and sedate the patient can avoid the risks associated with hurried sedation.

For pediatric PSA, the clinician should appreciate the adult dose of the sedative being administered and consider this the maximum threshold. Understand that the initial dose of midazolam for PSA in a 100-kg patient on a milligram-per-kilogram basis is far less than the 0.1 mg/kg used in a child to avoid unexpected mishaps in drug dosing.

Routes of Administration

For nondissociative agents, titrate IV medications to the patient's response for the best method of achieving rapid and safe analgesia and sedation. Wait the appropriate time for the medications to produce the intended effect before adding more doses. When using opioids, administer doses in 2- to 3-minute increments and observe for side effects such as miosis, somnolence, decreased responsiveness to verbal stimuli, impaired speech, and diminished pain on questioning as appropriate initial end points. For sedative-hypnotics, use similar incremental dosing and end points such as ptosis (rather than miosis), somnolence, slurred speech, and alterations in gaze. Repeated doses may be given in a titrated fashion based on the patient's response during the procedure.

The oral, transmucosal (i.e., nasal, rectal), and IM routes are more convenient means of administration when IV access is not necessary, but they are much less reliable for timely dose titration to a desired response. New drug delivery systems, however, are expanding the effectiveness and ease of use of these routes of administration. The refinement of intranasal drug delivery has significantly increased the efficacy of this route of administration. Before the development of metered-dose atomizers, the degree of absorption and effectiveness of intranasal drug administration were operator dependent. Furthermore, new drug formulations with concentrations appropriate for intranasal administration are becoming available for study.

The main advantage of these other routes is for pediatric patients in whom IV access may be problematic or for procedures that may require only minimal sedation in conjunction with the use of local anesthetics. These routes are also advantageous for simple sedation during diagnostic imaging.

With the exception of ketamine, agents administered intramuscularly have erratic absorption and a variable onset of action. Accordingly, prolonged preprocedural and postprocedural observation may be necessary. When required, the IM route offers little advantage over oral or transmucosal administration.

Another PSA route is via inhalation of nitrous oxide. This gas can either be delivered by a demand-flow system using a handheld mask or be delivered to young children using a nose mask in a continuous-flow system under close clinician supervision.

Because individual needs may vary widely, the application of arbitrary ceiling doses of analgesic and sedative regimens is unwarranted. The true ceiling dose of an agent is the level that provides adequate pain relief or sedation without major cardiopulmonary side effects such as respiratory depression, apnea, bradycardia, hypotension, or allergic reactions.

There are two absolute contraindications to PSA: severe clinical instability requiring immediate attention and refusal by a competent patient. Relative contraindications include hemodynamic or respiratory compromise, altered sensorium, or an inability to monitor for adverse events (e.g., magnetic resonance imaging [MRI] without remote monitoring). However, even in many of these circumstances, appropriate agents can be given to provide analgesia and sedation while minimizing the chance for further deterioration. Although safely sedating patients at the extremes of age is challenging and requires additional care, as well as reductions in drug dosing (because of decreased drug metabolism and excretion), age is not a contraindication to PSA.

Drug Selection Strategies

The majority of nonpainful or minimally painful ED procedures in older children and adults can be performed without systemic sedation and analgesia. Skilled practitioners can frequently combine a calm, reassuring bedside manner with distraction techniques, careful local or regional anesthesia, or both. Many procedures, however, cannot be technically or humanely performed without PSA. These situations can be divided into three categories.