What Are Conscious Sedation, MAC Sedation, and Twilight Sleep?
Not all surgeries have to be done with general anesthesia; i.e., the type that renders the patient unconscious. Sometimes, sedation (usually used to supplement local numbing injections) is enough to keep the patient comfortable. Possible options for sedation are light, moderate, or deep—depending on the situation.
You may hear various terms used to describe sedation protocols. Perhaps, you've been told you will be in "twilight sleep" or have "conscious sedation." Sometimes, you will hear surgeons, nurses, and anesthesiologists talk about "moderate sedation" or "MAC anesthesia."
Some of these terms mean the same thing or have overlapping connotations. Sometimes, the phrases are used interchangeably, but are technically a little different. And some of these descriptors for sedation techniques are actually quite specific. Confused yet? Don't be. All of these things mean you will have a level of sedation that will keep you comfortable and relaxed throughout your procedure.
The continuum of consciousness, as relates to anesthesia, proceeds as follows:
- awake (no sedation)
- lightly sedated
- moderately sedated
- deeply sedated
- unconscious (under general anesthesia)
It is not always possible to predict the level of sedation that will be needed by a specific patient for a specific procedure. The sedation can be adjusted to make sure you are comfortable, but not so sleepy that it isn't safe. So sedation can be made more deep or lighter, depending on needs at the time.
Sedation of any level should only be administered by qualified health practitioners. It definitely should not be administered in the bedroom of someone's home—even if that person is famous and rich—and even if the medication is administered by a licensed physician.
So, what exactly do each of these terms mean?
The phrase, "twilight sleep", is often used when speaking to patients because it seems to describe a state of semi-consciousness. It is less frequently used now and has been replaced by the more descriptive "conscious sedation." While this terminology does seem to indicate that you will be both conscious and sedated (true), it again does not indicate whether light, moderate, or deep sedation will be needed or used.
To confuse the issue more, most practitioners actually mean moderate sedation (see below) when they say "conscious sedation." The phrase "twilight sleep" is a more general term that does not indicate the level of sedation to be used.
So, to recap: both of the above phrases can mean any level of sedation. The term "conscious sedation" can, therefore, mean any level of sedation, but often refers to moderate sedation.
Light Sedation or Minimal Sedation
Minor surgeries and procedures may be done with light sedation. Light sedation implies that you will have your anxiety suppressed and will be a bit relaxed with medication. However, you will remain fully interactive with your surroundings.
- You can hold a conversation and are able to answer questions.
- You will not require support of cardiac or respiratory function.
- Minimal or no supplemental oxygen will be used.
- It is normal to remember most of your experience.
- You will need minimal recovery time.
- Side effects and complications are very, very rare.
Moderate sedation is used when some discomfort (that's doctor-speak for pain) is expected. Emergency room doctors often use moderates sedation to help them with procedures such as fracture reduction or correction of a dislocated joint.
To make the whole subject more confusing, most practitioners understand the phrase "conscious sedation" to mean moderate sedation.
- You will respond to speech prompts or light touch.
- You are able to support your own airway and ventilation without support.
- Blood pressure and heart rate remain within normal limits.
Deep sedation can be thought of as being on "just this side of consciousness." Most people will sleep through a procedure with deep sedation and require quite a bit of stimulation to respond.
- Breathing is usually adequate, although respiratory rate and depth of breathing may be decreased.
- Oxygen will be given with a cannula in the nose or mask over the nose and mouth.
- Deeper or more noxious stimulation is needed to get you to awaken or respond.
- Heart rate and blood pressure may minimally decrease.
Medications Used in Sedation Analgesia
Anxiety reduction (anxiolysis), relaxation, amnesia
Fentanyl or Morphine
Narcotic Opioid Pain Medicine
Anxiolysis, depress consciousness
Depress consciousness, pain suppression, amnesia
Insider's Note: If we refer to a "Big MAC," this implies that we think heavy sedation will be needed.
Monitored Anesthesia Care (MAC)
The acronym "MAC" stands for monitored anesthesia care. MAC means that an anesthesiologist (or nurse anesthetist, anesthesia resident, anesthesiology assistant) is present and responsible for the sedation, care, and monitoring of the patient during the procedure.
Any level of sedation can be a MAC anesthetic, but it usually implies a deeper level of sedation. Alternatively, anesthesiologists may be requested to administer sedation to very sick or high-risk patients.
For a MAC anesthetic, the anesthesiologist will assess the patient preop, monitor and medicate intraop, and direct the recovery postoperatively.
According to the American Society of Anesthesiologists (ASA), MAC may progress to general anesthesia and back again. Their statement includes the following:
"Due to the strong likelihood that 'deep' sedation may, with or without intention, transition to general anesthesia, the skills of an anesthesia provider are necessary to manage the effects of general anesthesia on the patient as well as to return the patient quickly to a state of 'deep' or lesser sedation." (Source: Paper entitled "Distinguishing Monitored Anesthesia Care ("MAC") From Moderate Sedation/Analgesia (Conscious Sedation)." Approved 2004, amended 2009, by ASA.)
The decision of whether or not to do a procedure under sedation vs. other types of analgesia/anesthesia is complex. Your surgeon and anesthesiologist will be able to let you know of your choices or options for your particular situation and may have a recommendation based on their experience.