Sedation Levels & Definitions

Sedation and analgesia include a continuum of states of consciousness ranging from minimal sedation (anxiolysis) to general anesthesia.  Shown below are the definitions of levels of sedation as defined and adopted by the American Society of Anesthesiologists (ASA).

ASA Definitions of General Anesthesia and Levels of Sedation/Analgesia (1)        
  Minimal Sedation
(Anxiolysis)
Moderate
Sedation/Analgesia
(Conscious Sedation)
Deep Sedation/Analgesia  General Anesthesia
Responsiveness Normal Response to Verbal Stimulation  Purposeful* resonse to verbal or tactile stimulation  Puposeful response after repeated or painful stimulation  Unarousable, even w/painful stimulus
Airway Unaffected  No intervention required  Intervention may be required  Intervention often required
Spontaneous Ventilation Unaffected  Adequate  May be inadequate  Frequently inadequate
Cardiovascular Function Unaffected  Usually maintained  Usually maintained  May be impaired

Minimal sedation:  Also known as anxiolysis.  A drug-induced state during which the patient responds normally to verbal commands.  Cognitive function and coordination may be impaired.  Ventilatory and cardiovascular functions are unaffected.

Moderate sedation/analgesia (conscious sedation):  A drug-induced depression of consciousness during which the patient responds purposefully to verbal command, either alone or accompanied by light tactile stimulation.  No interventions are necessary to maintain a patent airway.  Spontaneous ventilation is adequate.  Cardiovascular function is usually maintained.

Deep sedation/analgesia:  A drug-induced depression of consciousness during which the patient cannot be easily aroused, but responds purposefully* following repeated or painful stimulation.  Independent ventilatory function may be impaired. The patient may require assistance to maintain a patent airway.  Spontaneous ventilation may be inadequate.  Cardiovascular function is usually maintained.

General anesthesia:  A drug-induced loss of consciousness during which the patient is not arousable, even to painful stimuli.  The ability to maintain independent ventilatory function is often impaired.  Assistance is often required in maintaining a patent airway.  Positive pressure ventilation may be required due to depressed spontaneous ventilation or drug-induced depression of neuromuscular function.  Cardiovascular function may be impaired.

* Reflex withdrawal from a painful stimulus is NOT considered a purposeful response.

Monitored Anesthesia Care (MAC)

Following is the ASA position on monitored anesthesia care (approved by the House of Delegates October 21, 1986, and last amended October 25, 2005; 2).
  Monitored anesthesia care is a specific anesthesia service for a diagnostic or therapeutic procedure. Indications for monitored anesthesia care include the nature of the procedure, the patient’s clinical condition and/or the potential need to convert to a general or regional anesthetic.

Monitored anesthesia care includes all aspects of anesthesia care – a preprocedure visit, intraprocedure care, and postprocedure anesthesia management. During monitored anesthesia care, the anesthesiologist provides or medically directs a number of specific services, including but not limited to:
  • Diagnosis and treatment of clinical problems that occur during the procedure
  • Support of vital functions
  • Administration of sedatives, analgesics, hypnotics, anesthetic agents or other medications as necessary for patient safety
  • Psychological support and physical comfort
  • Provision of other medical services as needed to complete the procedure safely.

Monitored anesthesia care may include varying levels of sedation, analgesia, and anxiolysis as necessary. The provider of monitored anesthesia care must be prepared and qualified to convert to general anesthesia when necessary. If the patient loses consciousness and the ability to respond purposefully, the anesthesia care is a general anesthetic, irrespective of whether airway instrumentation is required (2).


ASA Guidelines for sedation and analgesia by non-anesthesiologists recommend monitoring of patient’s oxygenation, ventilation and circulation. Electrocardiograph monitoring should be used during moderate sedation in patients with significant cardiovascular disease or for patients undergoing procedures where dysrhythmias are anticipated.  Electrocardiograph monitoring is also recommended for all patients undergoing deep sedation. For all patients receiving deep sedation and those whose ventilation cannot be observed directly during moderate sedation, exhaled carbon dioxide capnography should be monitored. Other monitors recommended for both moderate and deep sedation include continuous pulse oximetry, observation and/or auscultation of ventilation at regular intervals, and blood pressure measurements every 5 minutes.  Level of consciousness should be assessed at regular intervals throughout the sedation process.  Verbal stimuli should be used for moderate sedation, with more profound stimuli used for deep sedation.
 
Moderate sedation/analgesia is the most common target level of sedation used in the outpatient/ambulatory setting.  Pain: Clinical Manual states that optimal moderate sedation is achieved when the patient:

  • Maintains consciousness
  • Independently maintains airway
  • Retains protective reflexes (swallow and gag)
  • Responds to verbal and physical commands
  • Is not anxious or afraid
  • Experiences acceptable pain control
  • Has a minimal change in vital signs
  • Remains cooperative during the procedure
  • Has mild amnesia for the procedure
  • Recovers to baseline (pre-procedure) status safely and promptly.

Several sedation scales and scoring systems have been developed to describe the level of consciousness. The Modified Observer’s Assessment of Alertness and Sedation, and to a lesser degree, the Ramsey Scale, are currently used most often in clinical research. However, these are not interchangeable with the ASA Definitions of Levels of Sedation, as they do not take into account cardiorespiratory status and there is some subjectivity as to what MOAA/S levels constitute moderate or deep sedation. It is important that there is a uniform assessment and subsequent assignment of a sedation scale score.

Modified Observer’s Assessment of Alertness/Sedation Scale (2)  
Responsiveness Score
 Agitated 6
Responds readily to name spoken in normal tone (alert) 5
Lethargic response to name spoken in normal tone 4
 Responds only after name is called loudly and/or repeatedly 3
Responds only after mild prodding or shaking 2
Does not respond to mild prodding or shaking 1
Does not respond to deep stimulus 0             

 
Ramsey Sedation Scale (4)  
Score Responsiveness
1 Patient is anxious and agitated or restless, or both
2 Patient is cooperative, oriented and tranquil
3 Patient responds to commands only
4 Patient exhibits brisk response to light glabellar tap or loud auditory stimulus
5 Patient exhibits a sluggish response to light glabellar tap or loud auditory stimulus
6 Patient exhibits no response

 


 

Sources

American Society of Anesthesiologists. ASA Standards, Guidelines and Statements, October 2007. http://www2.asahq.org/publications/p-106-asa-standards-guidelines-and-statements.aspx.

Cohen LB, DeLegge MH, Aisenberg J, et al. AGA Institute Review of Endoscopic Sedation. Gastroenterology 2007; 133:675-701.

McCaffery M, Pasero C, Pain: Clinical Manual, 1999, pp. 382-385, Mosby, Inc.

Ramsay MA, Savege TM, Simpson BR, Goodwin R. Controlled sedation with alphaxalone-alphadolone. Br Med J 1974; 2:656–659.

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