Procedural Sedation and Analgesia

DefinitionTop

Procedural sedation and analgesia are provided for the purpose of preventing or relieving discomfort, pain, and anxiety for patients who are undergoing short procedures associated with discomfort. Sedation is a drug-induced state of depressed consciousness, for most procedures (eg, endoscopies) preferably to a level at which the patient is still capable of a purposeful response to verbal or light tactile stimulation. For some procedures (elective intubation, cardioversion) short-term general anesthesia, making the patient unresponsive to pain stimulation, is usually required. The purpose of this chapter is to provide information relevant to the nonanesthesiologist who, for a variety of reasons, may provide short-term procedural sedation.

Of note, “procedural sedation and analgesia” was previously referred to as “conscious sedation” (and still may continue to be called this way). The association of these two terms may be contradictory, as effective sedation reduces consciousness.

MonitoringTop

All sedative-hypnotic agents, alone or in combination, are capable of rendering the patient apneic and hypotensive. Therefore, patients who are receiving sedative agents must be appropriately monitored, a minimum requirement being pulse oximetry and blood pressure, preferably with an automatic blood pressure cuff. In general, the person responsible for monitoring and sedation should be different from the person performing the procedure.

Continuous capnography is mandated by the American Society of Anesthesiologists and Canadian Anesthesiologists’ Society for all patients who receive moderate or deep sedation. At the level of moderate sedation, a patient maintains a purposeful response to verbal or tactile stimulation, and at the level of deep sedation, a patient has a purposeful response to repeated or painful stimulation. Capnography identifies apnea more rapidly than pulse oximetry, thereby allowing intervention before the onset of hypoxia or severe hypercarbia. A dedicated capnography facemask or capnography nasal cannula should be used where available for simultaneous delivery of supplemental oxygen and measurement of end-tidal carbon dioxide.

If flumazenil or naloxone is administered (see below), ≥2 hours of monitoring after the last dose of the reversal agent must be provided, due to the short half-life of the reversal agents compared with opioids and benzodiazepines.

PersonnelTop

In general, only an appropriately trained person should administer procedural sedation and analgesia, and training in airway management is an absolute requirement. The precise regulation differs in specific jurisdictions. An individual skilled in airway management (bag-valve-mask ventilation, endotracheal intubation) must be in attendance, along with appropriate airway management equipment and a source of oxygen and suction. The ability to manage hypotension with fluids and vasopressor medications and a “crash cart” containing advanced cardiac life support (ACLS) drugs, as well as naloxone and flumazenil, should be immediately available.

DrugsTop

General Issues

Drug requirements vary widely between patients, making it difficult to define safe dosage for any one individual. Advancing age, body habitus, critical illness, dehydration, hemodynamic instability, and level of consciousness before the procedure are some of the factors that may contribute to cardiorespiratory instability with the administration of even small doses of sedatives and opioids. Titration to effect is therefore a key principle in the safe provision of procedural sedation.

Goals for sedative and analgesic management should be established and drugs appropriate to the achievement of these goals should be administered. For example, opioid agents are excellent analgesics but have little amnestic or anxiolytic effects in small doses. Commonly used sedative agents such as the benzodiazepines and propofol are excellent anxiolytics and hypnotics but provide no analgesia. It is therefore common practice to use a combination of medications to achieve the desired effect of anxiolysis and analgesia. For example, the benzodiazepine midazolam and the opioid fentanyl are commonly used in combination for procedural sedation. It is imperative that it be understood that combining sedative agents with opioids will have at least an additive effect on level of consciousness, respiratory drive, and cardiovascular stability.

Two other agents, of a different class than the opioids and benzodiazepines are dexmedetomidine, an alpha2 agonist, and ketamine. The discussion of these agents is beyond the scope of this chapter.

Adverse effects other than cardiorespiratory depression are characteristic of all sedative and opioid agents and are not discussed here. For example, a knowledge of the propofol infusion syndrome, a potentially fatal complication of long-term high-dose propofol infusion, must be appreciated by those who prescribe this drug in such a way.

Specific Drugs and Dosages

The following dosages are guidelines only.

1. Sedatives:

1) Benzodiazepines:

a) Midazolam: 0.5 to 1 mg, repeated as necessary. Peak effect in 2 to 3 minutes.

b) Lorazepam: 0.25 to 1 mg, repeated as necessary. Peak effect in 5 to 20 minutes.

c) Diazepam: 2 mg, repeated as necessary. Peak effect in 2 to 5 minutes.

2) Propofol: 10 to 20 mg, repeated as necessary. Peak effect is rapid, in 90 to 100 seconds, or longer in older patients.

2. Opioids:

1) Fentanyl: 25 to 50 microg, repeated as necessary. Rapid onset. Half-life of 1.5 to 6 hours.

2) Morphine: 2 to 5 mg, repeated as necessary. Slower onset and longer half-life than fentanyl (3-7 hours).

3) Hydromorphone: 0.25 to 0.5 mg, repeated as necessary. Half-life of 1.5 to 3.5 hours.

3. Reversal agents:

1) Flumazenil may be used when reversal of sedating action of benzodiazepines is desired immediately. The starting dose is 0.2 mg IV over 15 seconds, which may be followed by a dose of 0.1 mg after 1 minute, repeated every minute up to a total dose of 1 mg (usually 0.3-0.6 mg is sufficient).

2) Naloxone may be used when reversal of sedation or apnea from opioids (eg, fentanyl, morphine) is desired. The starting dose is 0.1 mg, 0.2 mg, 0.4 mg IV up to a cumulative dose of ~1 mg.

Patient PreparationTop

Obtain informed consent for the procedure. Maintain the patient in a fasting state (nothing by mouth for solids and fatty liquids for 6 hours and clear fluids for 2 hours). Insert a relatively large-bore (≥1.2 mm [18 gauge]) peripheral IV catheter.

EquipmentTop

1. Equipment for insertion of a peripheral venous catheter and drug administration, equipment for airway management, equipment for mechanical ventilation and oxygen therapy (see Oxygen Therapy).

2. Cardiac monitor, pulse oximeter, waveform capnography, automated blood pressure monitor, defibrillator.

3. Drugs for the management of hypotension (IV fluids, catecholamines; see Shock), anaphylaxis (see Anaphylaxis and Anaphylactic Shock), and for cardiopulmonary resuscitation (see Cardiac Arrest).

ProcedureTop

1. Start monitoring blood pressure, heart rate, and hemoglobin oxygen saturation (SpO2) before administering any drugs and continue until complete reversal of sedation. Measure blood pressure frequently and regularly (usually every 1-5 minutes). Administer oxygen as needed (see Oxygen Therapy).

2. Titrate small incremental doses of sedative and/or opioid medications, continuously monitoring level of consciousness.

3. Maintain the airway (head tilt and chin lift; use an oropharyngeal airway if necessary), continue oxygen therapy, and ventilate with a self-inflating bag as required.

4. In case of achieving sedation beyond the targeted point (ie, deeper than planned), interrupt drug delivery, maintain the airway, and use reversal drugs as needed.