In this episode, I’ll discuss the continuum of depth of sedation.
The American Society of Anesthesiologists describes sedation as a continuum from minimal sedation to moderate sedation, deep sedation, and general anesthesia.
The depth of sedation can be determined by evaluating the patient’s responsiveness.
In a state of minimal sedation, (also called anxiolysis) a patient will have a normal response to verbal stimulation.
In a state of moderate sedation, (formerly called conscious sedation) a patient will have a purposeful response to verbal or tactile stimulation.
In a state of deep sedation, a patient will have a purposeful response only following repeated or painful stimulation.
In a state of general anesthesia, a patient will be un-arousable even with a painful stimulus.
The depth of sedation also indicates the risk of failure to the patient’s ability to maintain a patent airway, spontaneous ventilation, and normal cardiovascular function.
In a state of minimal sedation, these 3 systems of the airway, spontaneous ventilation, and cardiovascular function are unaffected. An example of this would be to give an anxious patient a benzodiazepine prior to an MRI scan.
In a state of moderate sedation, no airway intervention should be required, spontaneous ventilation is adequate, and cardiovascular function is usually maintained. An example of this would be to use incremental doses of midazolam and fentanyl to sedate a patient for endoscopy.
In a state of deep sedation, intervention to maintain a patent airway may be required, spontaneous ventilation may be inadequate, and cardiovascular function is usually maintained. An example of this would be to use etomidate 0.2 mg/kg or propofol 1mg/kg to reduce a dislocated hip or shoulder.
In a state of general anesthesia, intervention to maintain a patent airway is usually required, spontaneous ventilation is frequently inadequate, and cardiovascular function may be impaired. An example of this would be to use etomidate 0.3 mg/kg or propofol 2mg/kg as induction agents for rapid sequence intubation.
The intended depth of sedation can be determined by the dose of medication used and by the side effects of the medication that can be reasonably predicted. For example, etomidate or propofol can be used for deep sedation or general anesthesia, and the dose given helps to determine the intended depth of sedation. However, because respiratory failure is a known and predictable side effect of etomidate and propofol, neither drug could ever be intended for minimal or moderate sedation. Similarly, midazolam may be used in lower doses for minimal sedation as an anxiolytic but when given at higher doses such as 0.35mg/kg midazolam is considered an induction agent to achieve general anesthesia.
A basic principle of safety regarding sedation is that you should always have the proper staff and equipment to detect and rescue a patient from a level of sedation 1 higher than is being intended. This is usually a concern with deep sedation procedures. During a deep sedation procedure, the provider performing the procedure should be different than the provider responsible for monitoring and rescuing the patient from respiratory or cardiovascular distress. The provider responsible for rescuing the patient’s airway must be able to perform endotracheal intubation. This may mean two providers, or a provider and a respiratory therapist should be present for a deep sedation procedure.
A pharmacist present for a sedation procedure can help ensure that the medications and doses used are appropriate for the intended depth of sedation. Pharmacists can also help by ensuring that appropriate additional medications to support cardiovascular systems such as vasopressors are readily available when their need can be reasonably predicted.
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