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Anaesthesiology
Monitored Anesthesia Care
Built from Barash Clinical Anesthesia, 9th Edition
What’s inside
11 sections · 194 slides
Overview
- What this topic covers
- Definition of monitored anesthesia care
- Focus of the anesthesiologist during MAC
Terminology and Definitions
- Monitored anesthesia care versus moderate sedation
- Who may give moderate sedation
- Standards applied to monitored anesthesia care
- Services the anesthesiologist provides during MAC
- Threshold at which care becomes a general anesthetic
- ASA requirements for the MAC service
- ASA statements, guidelines and advisories on MAC and sedation
Preoperative Assessment
- Scope of the preoperative evaluation
- Medical conditions that raise risk during MAC
- Airway assessment before MAC
- Determinants of monitored anesthesia care candidacy
- Patient conditions favouring general anesthesia
- Patient motivation and communication
- Three roles of verbal communication during MAC
- Case factors in choosing monitored anesthesia care
- Effect of long procedure duration
- Fire risk from supplemental oxygen under drapes
- Reasons for converting MAC to general anesthesia
- Inability to tolerate monitored anesthesia care
- Additional causes of conversion to general anesthesia
- Setting patient expectations before MAC
Monitoring during Monitored Anesthesia Care
- Applicability of ASA basic monitoring standards
- The provider as the primary monitor
- Value of pulse oximetry
- Mechanisms of respiratory compromise during MAC
- Closed claims evidence supporting oxygen monitoring
- Role of capnography during monitored anesthesia care
- Nasal cannula with an integrated gas sampling port
- Improvised end-tidal carbon dioxide sampling
- Evidence that capnography detects respiratory events
- Case for routine capnography in every MAC case
- Cardiovascular monitoring requirements
- Temperature monitoring during MAC
- Thermoregulatory defenses and their impairment
- Hyperthermia during monitored anesthesia care
- Methods of assessing depth of sedation
- The ASA continuum of depth of sedation
- Minimal and moderate sedation defined
- Deep sedation and general anesthesia defined
- Ramsay Sedation Scale
- Richmond Agitation Sedation Score
- Observer's Assessment of Alertness/Sedation Scale
- Modified Ramsay Sedation Scale against the ASA continuum
- Richmond Agitation-Sedation Scale against the ASA continuum
- Modified Observer’s Assessment of Alertness/Sedation Scale against the ASA continuum
- Bispectral index monitoring during sedation
- Limitations of the bispectral index
- Drummond's criteria for a useful depth monitor
Supplemental Oxygen and Airway Fires
- Hypoxia from alveolar hypoventilation
- Worked example of the alveolar gas equation in hypoventilation
- Effect of raising inspired oxygen to 28%
- Two lessons from the oxygen worked example
- Evidence on routine supplemental oxygen during sedation
- Leading cause of death and severe injury during MAC
- Ingredients of a head and neck surgical fire
- Measured effective inspired oxygen concentrations
- Delivering sub-100% oxygen mixtures
- Recommendations to prevent burn injuries during MAC
Techniques and Pharmacologic Basis
- Goals of drug administration during MAC
- Verbal communication as a safety threshold
- Targeted treatment of pain, anxiety and agitation
- Life-threatening causes of patient agitation
- Pharmacokinetic and pharmacodynamic variability
- Principle of titration in small increments
- Continuous infusion versus intermittent boluses
- Drug concentration during different administration techniques
- Distribution after intravenous administration
- Accumulation in poorly perfused tissues
- Limitations of elimination half-life
- Definition of context-sensitive half-time
- Context-sensitive half-time as a function of infusion duration
- Rise in context-sensitive half-time with infusion duration
- Fentanyl and sufentanil compared
- Propofol and thiopental compared
- Factors determining time to recovery
- Effect-site concentration and awakening
- Effect-site equilibration time
- Comparative equilibration times of intravenous drugs
- Bolus spacing to avoid inadvertent overdose
- Rationale for combining drugs during MAC
- Nature of anesthetic drug interactions
- Cpss50 as a measure of intravenous drug potency
- Clinical implications of the steep dose-response curve
- Synergism between opioids and benzodiazepines
- Respiratory consequences of midazolam with fentanyl
Specific Drugs Used for MAC
- Propofol as a sedative-hypnotic for MAC
- Propofol compared with benzodiazepines
- Propofol sedation as an adjunct to spinal anesthesia
- Propofol versus midazolam as a spinal adjunct
- Pain on injection of propofol
- Most effective strategies against propofol injection pain
- Published strategies for reducing pain on intravenous injection of propofol
- Role of benzodiazepines during MAC
- Midazolam in a modified balanced technique
- Effect of age on benzodiazepine requirements
- Recovery profile after benzodiazepine sedation
- Reversibility as a safety margin
- Recommended regimen for intravenous flumazenil to antagonize benzodiazepine effects
- Remimazolam pharmacology
- Remimazolam compared with midazolam
- Remimazolam dosing and current evidence
- Indications for opioids during monitored anesthesia care
- Choosing and titrating an opioid
- Time to peak effect after opioid bolus
- Remifentanil pharmacology
- Remifentanil kinetics compared with other opioids
- Therapeutic end point for remifentanil
- Midazolam co-administration with remifentanil
- Practical remifentanil infusion regimen
- Typical adult intravenous dose ranges of sedative, hypnotic and analgesic drugs
- Typical adult intravenous dose ranges of sedative, hypnotic and analgesic drugs (continued)
- Ketamine during monitored anesthesia care
- Cautions with ketamine
- Rationale for the ketamine-propofol combination
- Evidence on respiratory events with ketofol
- Ketofol ratios and dosing
- Dexmedetomidine pharmacology
- Dexmedetomidine sedation quality and dosing
- Respiratory effects of dexmedetomidine
- Clinical uses of dexmedetomidine during MAC
- Dexmedetomidine for difficult airway instrumentation
- Dexmedetomidine compared with propofol
- Comparison of important properties of propofol and dexmedetomidine
Complications during Monitored Anesthesia Care
- Overall complication rate of monitored anesthesia care
- Respiratory depression as the leading MAC complication
- Collapsing tendency of the upper airway
- Coordination of dilator and diaphragmatic activity
- Sensitivity of dilator muscle control to sedation
- Why the compensatory response fails
- Patients most vulnerable to sedation-induced airway compromise
- Effects of specific drug classes on ventilatory response
- Impairment of protective airway reflexes
- Recovery time of the swallowing reflex
- Managing patients at high aspiration risk
- Propofol and upper airway protective reflexes
- Mechanism of laryngospasm
- Motor response producing glottic closure
- Persistence and consequences of true laryngeal spasm
- Incidence and risk factors for laryngospasm
- Limits of positive pressure ventilation in laryngospasm
- Larson's maneuver
- Definitive treatment of laryngospasm
- Causes of hemodynamic instability during MAC
- Managing cardiovascular risk during MAC
- Preparedness for local anesthetic systemic toxicity
- Mechanism and progression of local anesthetic toxicity
- Effects of hypercarbia on local anesthetic toxicity
- Masking of local anesthetic toxicity by sedation
Closed Claims and Nonanesthesiologist Sedation
- Trend in closed claims associated with MAC
- Non-operating room anesthesia claims
- Reasons nonanesthesiologists provide sedation
- Indirect involvement of anesthesiologists
- Core elements of the nonanesthesiologist sedation guidelines
- Dedicated observer requirements
- Education and training requirements
- High-risk groups needing preprocedure consultation
- Privileging for moderate and deep sedation
- Qualifications required for deep sedation
- CMS classification of anesthesia versus analgesia services
- ASA statement on the safe use of propofol
- Restriction on propofol, ketamine and etomidate
Future Directions
- Economic pressure on anesthesia-provided sedation
- Patient-controlled sedation and analgesia
- Target-controlled infusions
- Closed loop anesthesia delivery systems
- Limitations of closed loop systems
- Machine learning and artificial intelligence in sedation
Conclusion and Key Points
- Growing demand for monitored anesthesia care
- Key points on the nature of monitored anesthesia care
- Key points on safety during monitored anesthesia care
- References
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- References (continued)
- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition