Goals of Anesthesia + MAC

ANESTHESIA

  • Definition: An artificially induced, reversible/temporary depression of the nervous system, permitting the performance of surgery or other painful procedures.

  • Goals may include one or more of the following:

    • Analgesia: loss of response to pain.

    • Amnesia: loss of memory.

    • Anxiolysis/Sedation, Hypnosis: reduction of anxiety or induced sleep.

    • Skeletal Muscle Relaxation: loss of motor reflexes.

ARMAMENTARIUM

  • Multimodal pharmacology includes:

    • Benzodiazepines.

    • Opioids.

    • Intravenous (IV) anesthetics.

    • Inhalational anesthetics.

    • Local anesthetics.

    • Paralytics.

    • Nonsteroidal anti-inflammatory drugs (NSAIDs) and Acetaminophen.

    • Antiemetics.

    • Other medications as needed.

SEQUENCE OF DEPRESSION IN CNS AS A RESULT OF GENERAL ANESTHESIA

  • 1) Cerebrum: Loss of memory, impairment of judgment, obtunding of the special senses, unconsciousness.

  • 2) Cerebellum & Basal Ganglia: Loss of muscle coordination.

  • 3) Spinal Cord: Loss of the ability to convey all motor and sensory impulses.

  • 4) Medullary Centers: If allowed to continue, may lead to depression of respiration and cessation of spontaneous circulation.

TYPES OF ANESTHESIA

  • General Anesthesia (deep sedation): patients are not arousable, even by painful stimulation; this fulfills ALL four of the anesthesia goals.

    • The ability to independently maintain ventilatory function may be impaired; patients often require assistance in maintaining a patent airway.

    • There is a risk of cardiovascular function impairment.

    • Can only be achieved through: Volatile agents (sevo, des, iso), TIVA (propofol) — this is because they are paralyzed and need long-term sedation

  • Regional Anesthesia: local anesthetics are injected close to a nerve, a bundle of nerves, or the spinal cord, to block sensations of pain from an area of the body. Goal is to provide analgesia without amnesia. Typically, regional anesthesia means you do not need to do general and can allow airway reflexes to remain intact

    • Types of regional anesthesia:

      • A Bier block is provided via IV and tourniquet; the patient remains awake

      • Neuraxial blocks (into CNS)

        • Intrathecal (spinal)

        • Epidural

      • Peripheral blocks

        • Upper/Brachial plexus blocks

        • Lower/Lumbar plexus blocks

        • Abd blocks

  • Local Anesthesia: local anesthetics applied or injected near the nerve endings of peripheral nerves to induce a temporary loss of sensation in a localized region. Goal is to provide analgesia without amnesia.

  • Monitored Anesthesia Care (MAC): allows for patient responsiveness and faster recovery, depending on sedation rather than complete amnesia. More about this in a below section

LEVELS OF SEDATION

  • Minimal Sedation (Anxiolysis):

    • Drug induced state where the patient’s cognitive function may be impaired, but they can still respond verbally and ventilatory/CV function is unchanged.

  • Moderate Sedation with Analgesia (Conscious Sedation):

    • Patient responds purposefully to verbal commands either alone or with light tactile stimulation.

      • Need monitors. The proceduralist supervises sedation while performing the procedure. The focus is on the procedure and not the patient’s sedation.

  • Deep Sedation with Analgesia: Drug induced state where the patient cannot be easily aroused, but responds purposefully to painful stimuli. Ventilatory function may be impaired and the patient may require assistance in maintaining a patent airway. CV function is usually unaffected.

  • MAC: Provided by a qualified anesthesia provider who is focused exclusively on the patient, not the procedure.

    • Utilized for cases that are not invasive or stimulating enough to warrant general anesthesia and the risks incurred therein; diagnostic or therapeutic procedures, such as endoscopic procedures (EGD, colonoscopy), Radiologic procedures, Skin lesions, and Podiatry

    • MAC can mean a lot of different things in regards to the types and dosages of medications utilized as well as the level of sedation / anesthesia achieved. Once the patient loses the ability to respond purposefully and with intent, the patient is technically under general anesthesia; Most of the “MACs” provided are technically general anesthetics (like TIVA).

      • Key distinction: You CAN go all the way up to general anesthesia, but this is not supposed to be the standard/expectation. Instead, you just have the ABILITY to do this. This means MAC gas anesthetic should typically not be used; sedation, anxiolysis, analgesia, local anesthetic IS part of MAC though.

      • In order to give overall less amount of a drug, use continuous infusion INSTEAD of IV boluses

    • Rescue Capacity: MAC provider must be qualified and prepared to rescue an airway from deep sedation and convert to general anesthesia if necessary. A provider of moderate sedation is not expected to manage depths of sedation that impair airway reflexes.

    • Depth: MAC often involves the administration of drugs (e.g., Propofol, benzos, opioids, ketamine, or precedex) that induce deep sedation or transient general anesthesia, which is beyond the scope of moderate sedation.

  • Capnography is a standard of care EVEN for MAC cases. Even though there are sampling inaccuracies in non-intubated people

YOUR RESPONSIBILITIES DURING THE COURSE OF AN ANESTHETIC

  • Maintain appropriate level of consciousness (LOC) for the procedure and anesthetic technique.

  • Ensure sufficient concentration of anesthetic agent and manage adjunct and adjuvant drugs.

  • Provide pain control during the perioperative period (multimodal control, opioids, and local blocks).

  • Ensure patient remains cooperative (MAC) or does not move (general).

  • Maintain adequate depth and manage paralytics (for general anesthesia).

  • Maintain adequate oxygenation and remove carbon dioxide:

    • Oxygen supply to satisfy metabolic needs.

    • Use of FiO2, ventilation, scrubbers, and scavengers to manage waste gases.

  • Hemodynamically stable and preserve organ systems via fluid management and blood volume preservation.

  • Proper pharmaceutical management; ensuring the depth of anesthesia is appropriate.

  • Ensure temperature regulation: Use forced air warming, fluid warmers, and warm blankets; manage room temperature.

  • Preservation of patient dignity: Keep the patient covered, manage teeth/dentures, and address patient concerns with care.

  • Prevent mechanical injury: Proper positioning, management of pressure points, and eye care.

  • Reverse anesthesia at the appropriate time.