Moderate Sedation and Monitored Anesthesia Care: What's the Difference?

Two patients undergoing medical procedures might be given the exact same sedatives and/or analgesics, but when the claims for the sedation are billed, two different codes will be used. So what’s the difference?

In one case, the physician performing the surgical procedure also administered the sedative, and when she submitted the claim, she included codes 99151 and 99153 for moderate sedation, in addition to the codes for the surgical procedure. In the other case, one physician, a surgeon, billed for the surgical procedure, and another physician, an anesthesiologist, billed an anesthesia code with the modifier QS indicating monitored anesthesia, based on an assessment of the patient’s condition and the procedure being performed.

So what exactly is the difference between moderate sedation and monitored anesthesia care? And when does monitored anesthesia care become general anesthesia?

Moderate Sedation

According to the American Society of Anesthesiologists, moderate sedation, or what is also known as conscious sedation, is

“a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.”

Moderate sedation, which the ASA says can “allay patient anxiety and limit pain,” is recognized as a billable physician service. Beginning in 2017, the American Medical Association unbundled the service from hundreds of procedures and assigned six codes to be used for physician billing. Often during moderate sedation, a single physician assumes the dual role of administering the sedative and performing the surgical procedure. As such, anesthesiologists rarely bill for moderate sedation, except in cases like chronic pain management procedures, where the anesthesiologist himself serves in the dual role. However, CPT codes do exist for moderate sedation performed by a physician other than the one performing the surgical procedure.

Moderate sedation also is a term used to indicate one of several levels of sedation along a continuum, from anxiolysis (or minimal sedation) to moderate sedation to deep sedation to general anesthesia. According to the ASA, physicians providing moderate sedation should be able to recognize when a patient has progressed down the continuum to “deep” sedation and adjust the level of sedation back to “moderate.”

“The continual appraisal of the effects of sedative or analgesic medications on the level of consciousness and on cardiac and respiratory function is an integral element of this service,” the ASA explains in its article, “Distinguishing Monitored Anesthesia Care (ʺMACʺ) from Moderate Sedation/Analgesia (Conscious Sedation).”

Monitored Anesthesia Care

As for monitored anesthesia care (MAC), the ASA defines this service as

“a specific anesthesia service performed by a qualified anesthesia provider for a diagnostic or therapeutic procedure. Indications for monitored anesthesia care include, but are not limited to, the nature of the procedure, the patient’s clinical condition and/or the need for deeper levels of analgesia and sedation than can be provided by moderate sedation (including potential conversion to a general or regional anesthetic).”

Though a MAC patient may remain at moderate sedation throughout the surgical procedure, a qualified anesthesia provider is present the entire time, “focused exclusively and continuously on the patient for any attendant airway, hemodynamic and physiologic derangements.” In fact, the periprocedural attention and assessment by the anesthesiologist is a key component of MAC, along with the preparation and qualifications to do the following:

Convert to general anesthesia at any time during the procedure if necessary.
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.
Rescue a patient’s airway from any sedation-induced compromise.
Intervene and resuscitate patients for whom even small doses of sedation or analgesic cause adverse physiologic responses.

In addition, MAC includes several post-procedure responsibilities that would not be expected during moderate sedation, like “assuring a return to baseline consciousness, relief of pain, management of adverse physiological responses or side effects from medications administered during the procedure, as well as the diagnosis and treatment of co-existing medical problems,” according to the ASA.

General Anesthesia

With today’s options for sedation, the same drugs used to achieve conscious sedation may also move a patient into general anesthesia, which the ASA defines as

“A drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. Patients often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function. Cardiovascular function may be impaired.”

General anesthesia is often the first choice for surgical procedures, but even when MAC, rather than general anesthesia, is chosen, this deepest level of sedation is always an option, whether intentionally induced or not. For this reason, the ASA advises that “practitioners intending to produce a given level of sedation should be able to rescue patients whose level of sedation becomes deeper than initially intended.”

Billing Guidelines

Moderate sedation is billed using a specific set of codes outlined in the CPT code set.

Code	Provider Performing Sedation *and* Primary Service	Code	Provider Performing Sedation **but notPrimary Service**
99151	“initial 15 minutes of intraservice time, patient younger than 5 years of age”	99155	“initial 15 minutes of intraservice time, patient younger than 5 years of age”
99152	“initial 15 minutes of intraservice time, patient age 5 years or older”	99156	“initial 15 minutes of intraservice time, patient age 5 years or older”
99153	“each additional 15 minutes intraservice time (list separately in addition to code for primary service)”	99157	“each additional 15 minutes intraservice time (list separately in addition to code for primary service)”

Because the codes are based on time spent, physicians can bill sedation if they spend 10 or more minutes in intraservice time. Additionally, at least seven minutes must pass to report an additional unit.

For example, a physician who spends 21 minutes sedating a 4-year-old patient could bill only 99151 for minutes 1-15. Minutes 16-21 would not be billable because they didn’t add up to at least seven minutes. However, if that same physician spent 27 minutes sedating a 4-year-old patient, she could bill 99151 for minutes 1-15 and 99153 for minutes 16-27 since she spent at least seven minutes after the initial intraservice range.

MAC is billed using anesthesia procedure codes that correlate with the specified surgical procedure, along with the appropriate pricing modifier, the actual anesthesia time, plus the QS modifier indicating this is a monitored anesthesia care service.

MAC procedures that are converted to general anesthesia are billed as if the whole procedure was general anesthesia, using the anesthesia procedure code that correlates with the specified surgical procedure, the actual anesthesia time, and the appropriate pricing modifier. In this case, providers would NOT use the QS modifier.