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Monitored Anesthesia Care - Procedures and Complications.

Published on Dec 29, 2022   -  4 min read


Monitored anesthesia care (MAC) is specialized anesthesia for diagnostic or curative purposes carried out under local anesthesia with sedation and analgesia.


Monitored anesthesia care (MAC) involves an anesthesia clinician continuously monitoring and supporting the patient's vital functions, diagnosing and treating any clinical issues, providing sedative, anxiolytic, or analgesic medications as necessary, and shifting to general anesthesia if necessary. A significant portion of anesthetic treatments provided nationwide is MAC alone or in combination with a local anesthetic.

The MAC constitutes the following elements and purposes safe conscious sedation, measures to allay the patient’s anxiety, and adequate pain control. A MAC practitioner must be highly qualified and knowledgeable to convert to general anesthesia or to rescue an airway if needed. Hence, MAC is a service provided by anesthesiologists depending on the degree of sedation and analgesia available based on the nature of the surgery and the patient's condition. Sedation during MAC may be safer than general anesthesia because fewer drugs are administered.

Adjust the dosage of sedatives and analgesics to prevent central respiratory depression and airway blockage since the patient's airway is not protected during MAC. During MAC, systemic sedation and analgesia are provided by an anesthesiologist, and local anesthesia, including local infiltration or field block, is mainly performed by a surgeon. Like general or regional anesthesia, preoperative assessment, perioperative management, monitoring, and postoperative recovery care are provided similarly to MAC.

What Is Preoperative Evaluation of MAC?

The preoperative evaluation of MAC is very similar to that of general and regional anesthesia, where all the patients undergoing anesthesia through MAC should be assessed in detail. Patients undergoing MAC should be able to respond to the commands given by the anesthetist to decide whether they are prepared for the treatment. If the patient is not able to respond, general anesthesia is preferred.

Verbal assurance and sedation level monitoring can improve cooperation and communication between the patient and the anesthetist care team. There are no particular exclusion criteria for MAC, which can be performed safely in elderly and high-risk patients, such as patients with cardiovascular and respiratory instability. Still, continuous coughing or moving during microscopic procedures may hinder the usage of this type of anesthesia.

Preoperative evaluation helps determine the right candidate for MAC and improves the patient-anesthetist relationship, thereby improving cooperation. The patient's physical condition, particularly their ability to breathe and heartbeat, may influence or decide their sensitivity to sedatives and analgesics. The preoperative appointment must evaluate co-morbidity, previous history, medication responses, and postoperative anesthesia problems.

What Is Intraoperative Monitoring During Monitored Anesthesia Care?

It is essential for intraoperative monitoring to be efficient, practical, noninvasive, and affordable. An experienced anesthesiologist must continually monitor patient oxygenation, breathing, circulation, and temperature. Continuous respiratory monitoring is crucial for the prevention of respiratory distress during the administration of sedatives and analgesics. Precordial or esophageal stethoscopes can be utilized for continuous ventilation and inspired oxygen. In addition, real-time identification of hypoxemia by capnography is necessary.

Monitoring the Level of Consciousness During MAC?

  • In addition to routine monitoring, assessing the amount of sedation during MAC is crucial for determining the safety and efficacy of the sedatives.

  • Electroencephalographic (EEG) methods like the bispectral index (BIS) have been used for continuous real-time monitoring of sedation levels.

  • BIS is a device used to assess EEG variations to different levels of sedation and analgesics, mainly the frequency and amplitude of EEG waves, which are then analyzed and correlated with the BIS numerical index.

  • Several sedation measures related to the amount of MAC sedation have been employed in clinical evaluation to lower the subjectivity of the anesthesiologist's judgment.

  • The observer assessment of alertness or sedation scale (OAA/S scale) and Ramsay sedation scale (RSS) are well-established instruments for evaluating the level of consciousness.

  • RSS uses a loud auditory signal, a light glabellar tap, and behavior observation to evaluate a patient's awareness level, agitation, and anxiety.

What Is a Patient Satisfaction Score?

The Iowa satisfaction with anesthesia scale (ISAS) is a device for assessing patient satisfaction levels and experience during anesthesia, including MAC. The ISAS is a written questionnaire to which the patient responds.

What Are Systemic Sedatives and Analgesics for Monitored Anesthesia Care?

Local anesthesia is combined with sedatives and analgesics to comfort the patient during procedures performed with MAC. Continuous infusion of fast-eliminating drugs helps the anesthesiologist achieve selected drug concentration at the affected site and maintain safety. MAC is a popular alternative for reducing the physiological stress of older patients, and geriatric anesthesia is rising.

Sedatives relieve amnesia and anxiety during the procedure because patients often suffer pain and anxiety. Appropriate doses of sedatives are required because heavy sedation causes airway obstruction, and light sedation causes anxiety in the patient. Monitor the degree and dose of the sedation through continuous patient communication and hemodynamic changes. Sedatives should have quick onset and recovery, simple titration, and minimum respiratory and cardiovascular depression during MAC.

Benzodiazepines (Midazolam) provide comfort to the patient and also amnesia during the procedure. Midazolam is frequently co-injected with Propofol (starting dose: 0.03 mg/kg, infusion rate: 0.6-6.0 mg/kg/h). Propofol is the cornerstone drug of MAC because of its pharmacodynamic and pharmacokinetic action. Compared to Midazolam, cognitive function recovery is quicker, and postoperative nausea and vomiting (PONV), dizziness, forgetfulness, and drowsiness are less severe than Propofol sedation.

Analgesics are used to relieve discomfort and pain associated with the procedure. Fentanyl and, Alfentanil, Remifentanil are used for managing pain during surgery. However, Remifentanil causes respiratory depression, so the anesthetist should be cautious during the infusion of Remifentanil. The ketamine-Dexmedetomidine combination is a well-known sedative and analgesic for children during magnetic resonance imaging.

What Are the Procedures Performed Under Monitored Anesthesia Care?

  • Eye surgeries.

  • Cardiovascular procedures.

  • Otolaryngologic surgery (a medical-surgical subspecialty concerned with the surgical and medical management of head and neck conditions).

  • Inguinal herniorrhaphy (an inguinal hernia occurs when tissue, such as a section of the intestine, protrudes through a weak spot in the abdominal muscles. The resulting bulge can be painful, particularly when coughing, bending over, or lifting a heavy object).

  • Painful procedures.

  • Gastro endoscopic procedures.

  • Neurosurgery.

  • Flexible bronchoscopy.

What Are the Complications of Monitored Anesthesia Care?

The complications during MAC include drowsiness, nausea, vomiting, trouble waking from sedation, airway obstruction, aspiration, hypoxia, cardiovascular collapse, stroke, and allergic reactions to sedatives and analgesics.


MAC is used for diagnosis and to carry out the treatment in and outside the operating room without the use of general or regional anesthesia due to fast recovery and affordability by the patient. The anesthesia care team should be able to decide the choice of sedative and analgesia depending on the procedure. A well-trained anesthesiologist must be present, along with an oxygen supply, monitoring technology, and emergency equipment.

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Last reviewed at:
29 Dec 2022  -  4 min read




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