Procedural Sedation and Analgesia

by Nik Rahman

Introduction

When working in the emergency room, one often finds himself in a situation where painful diagnostic or therapeutic procedures are needed to be performed. These procedures cause major pain and anxiety to the patient and using local anesthesia on its own does not suffice in some situations. Procedural sedation reduces anxiety, pain and potential unpleasant memories associated with such procedures while also facilitating the execution of the procedure. Therefore, procedural sedation and analgesia (PSA) has become a fundamental and required skill for emergency physicians to learn for day to day use. This chapter is also important for many physicians who are facing painful procedures.

Definition

Procedural sedation is defined as the use of short-acting analgesic and sedative agents in order to enable clinicians to perform procedures effectively while monitoring the patient closely for potential adverse effects.

Terminology

Anxiolysis is a state in which decreasing apprehension regardings a particular situation without affecting patient’s level of awareness.

Without the intentional alteration of mental status, relief of pain is called Analgesia. However, the 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 is characterized by profound analgesia and amnesia. In this state, protective reflexes, spontaneous respirations, and cardiopulmonary stability are preserved.

The controlled reduction of environmental awareness is called sedation.

Levels of Sedation

1. Minimal sedation (anxiolysis) refers a patient in this state responds normally to verbal commands, although cognitive functions and coordination may be impaired. Respiratory and cardiovascular functions are unaffected as this state essentially involves mild anxiolysis or pain control.
2. Moderate sedation/analgesia involves depression of consciousness while patients still respond purposefully to verbal commands or light tactile stimulation. Airway, ventilation and cardiovascular functions are all spontaneously maintained. The patient may appear somnolent but is arousable to voice or light touch. (Reflex withdrawal from the painful stimulus is not considered a purposeful response.)
3. Dissociative sedation is a cataleptic state induced by a dissociative agent (i.e., Ketamine). This state is characterized by profound analgesia and amnesia. This state is achieved while airway protective reflexes are maintained along with spontaneous respiration. Cardiopulmonary stability is also maintained.
4. Deep sedation/analgesia is a state where the patient has a depressed level of consciousness in which he/she requires painful or repeated stimulation to evoke a purposeful response. Patients may require assistance to maintain a patent airway. Spontaneous ventilation may be inefficient. Cardiovascular function is usually preserved.
5. General anesthesia refers to the drug-induced loss of consciousness which patients are not arousable to painful stimulation. In this state, the ventilatory function is often impaired, and assistance may be required to maintain the airway and respiration. Positive-pressure ventilation may be required as spontaneous ventilation is often impaired. Cardiovascular function may be impaired as well.

The different levels of sedation need to be understood as each scenario may require a certain level to be achieved to facilitate the performance of the required procedure.

Steps for PSA

Early planning and preparation are key to preventing adverse events that may occur and can be catastrophic if procedural sedation is poorly managed.

Adequate staffing needs to be ensured; this is done by having a nurse or another qualified individual present for continuous monitoring of vital signs and airway patency as well as having a separate provider performing the procedure.

Pre-procedural evaluation

The patient should be evaluated for sedation. PSA may not be suitable for every patient in the ED. This can be done objectively by using the ASA classification and difficult airway assessment (Table).

American Society of Anesthesiologists Physical Status Classification

CLASS	DESCRIPTION	EXAMPLES	SEDATION RISK
I	Normal and 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

Anesthesiology consultation may be required for a patient with an anticipated difficult airway or an ASA classification of III. It may be wise to have the anesthesiologist perform the sedation in the operating room which is a better-controlled environment.

Consent

When possible, a written consent should be obtained that discusses the risks, benefits, and potential side effects of PSA. The patient or direct family members need to sign the consent before the procedure takes place.

Equipment Preparation

1. High-flow oxygen source: ASA guidelines recommend considering oxygen for moderate sedation and strongly recommend it for deep sedation.
2. Suction should be prepared in case any secretions accumulate in the airway, which in turn need to be suctioned.
3. Airway management equipment: there may be a need for airway support during PSA. An appropriate size endotracheal tube should be prepared with an intubating blade, an oral airway and a bag valve mask (BVM).
4. Monitoring equipment includes a pulse oximeter, ECG monitor/defibrillator, transcutaneous pacing pads, Blood pressure monitor, and Capnography. Capnography measures end-tidal carbon dioxide (CO2) partial pressure. The ASA recommends the use of capnography for monitoring patients during PSA whether they are on supplemental oxygen or not. The aim is to detect if the patient’s ventilatory drive is affected during the procedure in order to perform corrective measures when needed.
5. Vascular access equipment

Medications used in PSA

ETOMIDATE

• Etomidate is a fast-acting sedative with little analgesic effect. The onset of action is usually within 1 minute with a short duration of action. It lasts between 3 to 5 minutes with standard dosing. Elimination is done rapidly by the liver; therefore, duration of action may be longer in patients with liver failure. It has few hemodynamic effects, and its neutral cardiovascular profile makes it one of the most appealing agents for use.
• The contraindication is hypersensitivity to the medication.
• Etomidate is a Pregnancy Category C medication
• Side Effects:
  • Muscle twitching is a well-known side effect that is generally well tolerated
  • Nausea and vomiting may occur after emergence
  • Respiratory depression and hypoxia are possible
• Generally, Etomidate has been shown to be safe and effective when used for procedural sedation.

KETAMINE

• Ketamine is a rapidly acting dissociative anesthetic that also produces a profound analgesic effect. Doses can be repeated and titrated to effect with no risk of cumulative adverse events. Onset, duration, and dosing vary according to the route of administration.
• Contraindications:
  • Hypersensitivity to the medication
  • Can lead to a hyper-sympathetic state, which might be deleterious especially in patients with Coronary Artery Disease
  • Avoided in patients who are predisposed to psychotic behavior
• Ketamine is a Pregnancy Category C medication
• Side Effects:
  • Ketamine is a derivative of the street drug Phencyclidine; it causes an increase in systemic and pulmonary blood pressures, heart rate, cardiac output, cardiac workload and myocardial oxygen demand. It should be avoided in elderly or patients with cardiac diseases.
  • Most common side effect seen with Ketamine is the emergence phenomenon. It occurs in approximately 15% of patients and is mild in almost all of them. Less than 1 to 2% of patients have significant emergence agitation.
  • Transient airway laryngospasm (0.4%)
  • Emesis

FENTANYL

• A rapid-acting synthetic opioid administered intravenously. Duration of action may last from 30 to 60 minutes. It is a pure analgesic with no sedative properties; therefore, it must not be used alone for PSA.
• It is a Pregnancy Category C medication
• Side Effects:
  • Respiratory depression is more likely at higher doses
  • Hypotension and bradycardia are rare but may occur with high doses

PROPOFOL

• This is an ultra-short-acting sedative-hypnotic agent that has no analgesic properties. It is quickly cleared from the body, permitting superior titration, earlier recovery, and discharge. It also possesses potent antiemetic properties and decreases intracranial pressure. Because of lack of analgesic effect, it should be preceded by an opioid when performing painful procedures.
• Contraindications: in patients with allergy to eggs or soy
• Side Effects:
  • Respiratory depression
  • Apnea
  • Hypotension
  • Pain over the injection site

MIDAZOLAM

• Midazolam is a benzodiazepine sedative, amnestic and anxiolytic agent with no analgesic properties. It is usually combined with opioids like Fentanyl to provide a good combination of sedation and analgesia during PSA. It is eliminated by hepatic metabolism and renal excretion; therefore, prolonged effects may be seen with dysfunction of any of those two organs.
• Side Effects:
  • Cardiopulmonary depression
  • It is a Pregnancy Category D medication

The following table below is a summarized list of all medications used during procedural sedation.

Agents Used in Procedural Sedation

AGENT	RECOMMENDED DOSE	ONSET OF ACTION	DURATION OF ACTION	SIDE EFFECTS AND COMMENTS
Etomidate	In adults 0.2 mg/kg over 30 to 60 seconds	< 1 minute	3 to 5 minutes	Advantages: no cardiovascular or respiratory depression Disadvantages: action is too short for some procedures
Ketamine	1 to 2 mg/kg intravenously 4 to 5 mg/kg intramuscularly	1 minute 5 minutes	10 to 20 minutes 15 to 45 minutes	Nystagmus, hypersecretions, agitation, emergence delirium, vomiting, myoclonus, laryngospasm, cardiovascular stimulation Contraindications: hypertension, ischemia, psychosis, infants younger than three months
Fentanyl	Initial dose in adults: 1 to 1.5 mcg/kg intravenously Titrate: 1 mcg/kg every 3 minutes intravenously	1 to 2 minutes	30 minutes	Cough, hiccup, itching, vomiting, respiratory depression Requires another agent for sedation, repeat dosing may be required
Midazolam	Initial dose in adults: 0.02 mg/kg Titrate: 1 mg intravenously every 3 minutes Initial dose in children (6 months - 5 years of age): 0.1 mg/kg	1 to 2 minutes	30 minutes	Respiratory depression, hypotension Requires another agent for analgesia, poor reliability, repeat dosing may be required
Propofol	1 mg/kg Intravenously, then 0.5 mg every 3 minutes if needed	15 to 30 seconds	5 to 10 min	Respiratory depression, apnea, hypotension, pain over injection site Advantages: Rapid onset, short duration, antiemetic, cerebral protective. Contraindications: allergy to eggs or soy

Reversal Agents

Fentanyl and Midazolam both have antagonists that can be used to reverse their effects.

Agents like Naloxone for opioids (i.e., Fentanyl) and Flumazenil for benzodiazepines (i.e., Midazolam) are the ones commonly used for this purpose. However, the routine use of reversal agents should be avoided as the duration of the sedation agents may exceed that of the reversal agents. If used, it should be followed by an extended observation period to ensure recovery.

Caution: when using Flumazenil, it may lead to Status Epilepticus, especially in patients with unidentified benzodiazepine use or in patients with a known seizure disorder.

Recovery and Discharge

Finally, it is important to monitor all patients until the moment of recovery. Drowsy patients should not be left unattended. Patients should be monitored until they spontaneously wake up and are able to perform their normal functions independently. Complete recovery to baseline function may not be necessary for discharge. Generally, an awake patient who is able to drink without vomiting, able to ambulate and voids normally is capable of going home ideally with family members or friends as an escort. Appropriate discharge instructions should be given.

References and Further Reading

• Clinical Policy: Procedural Sedation and Analgesia in the Emergency Department. Annals of Emergency Medicine. 2014;63(2):247-258.e18.
• Weingart S. Procedural Sedation – Part 1 [Internet]. EMCrit Podcast. 2010 [cited 25 May 2016]. Available from: http://emcrit.org/archive-podcasts/procedural-sedation-part-1/
• Weingart S. Procedural Sedation – Part 2 [Internet]. EMCrit Podcast. 2010 [cited 25 May 2016]. Available from: http://emcrit.org/podcasts/procedural-sedation-part-2/
• Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology. 2002;96(4):1004-1017.