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Indications for MAC include:
- 1. the nature of the procedure
- 2. the patients clinical condition
- 3. and/or the potential need to convert to a general or regional anesthetic
During MAC and the perioperative period the anesthesiologist provider medically directs specific services including but not limited to:
- 1. Diagnosis and treatment of clinical problems that occur during the procedure
- 2. Administration of sedatives, analgesics, hypnotics, anesthetic agents, or other medications
- 3. Psychological support and physical comfort
- 4. Provision of other medical services as needed to complete the procedure safely
True or False: MAC is attractive because it should invoke more physiologic disturbance and a longer recovery period than general anesthesia?
FALSE: MAC should invoke less physiologic disturbance and allow a more rapid recovery than GA
Monitored Anesthesia Care implies
the potential for a deeper level of sedation than that provided by sedation/analgesia and is always administered by an anesthesiologist provider
MAC usually involves the administration of what kind of drugs:
Drugs with anxiolytic, hypnotic, analgesic, and amnestic properties, either alone or as a supplement to a local or regional technique
During MAC the continuous attention of the anesthesiologist is directed at
optimizing patient comfort and safety
T or F: If the patient loses consciousness and the ability to respond purposefully, the anesthesia is GA, whether airway instrumentation is required.
MAC services MUST include what:
- 1. Performance of a preanesthetic exam and eval
- 2. Prescription of anesthetic care
- 3. Personal participation in or medical direction of the entire plan of care
- 4. Continuous physical presence of the anesthesiologist or in the care of medical direction a resident or CRNA
- 5. Proximate presence or availability for diagnosis and tx of emergency
ASA requires that institutional regulations continue to be observed with MAC including:
- 1. usual noninvasive cardiocirculatory and resp monitoring
- 2. O2 admin
- 3. admin of medications
Preoperative evaluation for MAC includes all of the necessary assessments and additional assessments including:
- 1. the patients ability to remain motionless
- 2. the patients baseline sensorineural or cognitive deficiencies
- 3. the patients ability to communicate with the physician to assess level of sedation and cardiorespiratory function, to reassure and explain things to the patient, and to communicate with the patient when their involvement is required
Medications administered during MAC have the desired outcome of:
- 1. providing patient comfort
- 2. maintain cardiorespiratory stability
- 3. improve operating conditions
- 4. prevent recall of unpleasant peri-operative events
Side effects that should be limited include:
- 1. cardiorespiratory depression
- 2. N/V
- 3. delayed emergence
- 4. dysphoria
- 5. THERE SHOULD BE A RAPID AND COMPLETE RECOVERY WITH MAC
T or F: A level of sedation that does not allow verbal communication is optimal for patients safety and comfort during their operation.
FALSE: a level of sedation that DOES allow verbal communication is optimal, if the level of sedation is deepened where communication is lost the risks then approach those of GA with an unprotected and uncontrolled airway.
Causes of pain and agitation during MAC include but not limited to:
- 1. hypoxia
- 3. impending LA toxicity
- 4. cerebral hypoperfusion
- 5. distended bladder
- 6. hypo/hyperthermia
- 7. nausea
- 8. position
- 9. tourniquet inflation
What are fundamental concepts helpful in MAC?
- 1. Context sensitive halftime
- 2. effect site equilibration time
- 3. anesthetic/sedative drug interactions
To avoid excessive levels of sedation, how should medications be titrated?
Drugs should be titrated in small increments or by adjustable infusions rather than administered in larger doses
Why are continuous infusions superior to intermittent bolus dosing?
Intermittent bolus dosing causing significant fluctuations in drug concentrations meaning the plasma concentrations are either above or below the desired level of therapeutic range. Continuous infusions produce less fluctuations in drug concentrations, reducing the number of episodes of inadequate or excessive sedation.
What is context sensitive half time?
Context sensitive half time describes the time required for the plasma drug concentration to decline by 50% after terminating an infusion of a particular duration
Do context sensitive half times have a relationship to their elimination half times?
No, context sensitive halftimes of all drugs bear NO CONSTANT relationship to their elimination half times.
Effect site equilibration is a concept relevant to IV sedation, what is it?
Effect site equilibration explains why there is a delay from administration to clinical effect. Plasma is not usually the site of action and is merely the route taken for the drug to be delivered.
T or F: There is one single drug that provides analgesia, anxiolysis and hypnosis safely for MAC.
False: combinations of drugs enable reductions in the dose requirements of individual drugs. Combination of fentanyl and proposal by infusion has been sown to produce a more rapid recovery and better stress response abolition than the use of propofol alone.
What is CP50?
CP50 is the plasma concentration of a drug at steady state that is required to abolish purposeful movement at skin incision in 50% of patients, it is a measure of potency analogous to MAC of volatiles.
Midaz and fentanyl together produce or can produce:
- 1.hypnosis, amnesia, analgesia
- 2. Hypoxemia and apnea
- 3. cardiovascular depression
Propofol advantages in MAC:
- 1. context sensitive half time that remains short even after prolonger duration of infusion
- 2. short effect site equilibration time
- 3. easily titratable
- 4. low incidence of N/V
- 5. rapid return to clearheadedness
- 6.Produces less postoperative sedation, drowsiness, confusion and clumsiness than midaz
Benzos for MAC:
- 1. anxiolytic, amnestic, hypnotic properties
- 2. Midaz is a superior choice because it has short elimination half life
- 3. Midaz has a prolonged psychomotor impairment
- 3. BENZOS are used in combination of propofol in smaller doses to provide a balanced anesthetic
- 4. enhance patient comfort, improve operating condition, and provide amnesia
- 5. Antagonist: flumazenil 0.2mg up to 1mg
dose of Midazolam is lower in the elderly related to:
The elderly have a threefold decrease in plasma concentration 50% of patients would be expected not to respond to verbal command in an 80y.o as compared to 40y.o
Opioids for MAC:
- 1. indicated when regional or local anesthetic techniques are inappropriate or ineffective, administered immediately before invasive or painful portion
- 2. used for uncomfortable positioning, pneumatic tourniquet,
- 3. Adverse effects: respiratory depression, muscle rigidity, n/v, the coadmin of sedative agents increases the risk of resp arrest, opioids lack significant amnestic properties
Typical dose ranges for benzos, opioids, and hypnotics:
- Midaz: 1-2mg prior to propofol or remi
- Diazepam: 2-8 mg
- Alfentanil 5-20mcg/kg bolus 2min prior to stim
- Fentanyl 0.5-2mcg/kg 2-4 min prior to stim
- Remi: 0.1mcg/kg/min 5 min prior to stim (infuse)
- Propofol 250-500mcg/kg boluses
- 25-74 mcg/kg/min infusion
T or F: Intraoperative PCA during monitored anesthesia care provides and effective alternative to physician administered analgesia
Respiratory function during MAC:
- 1. Upper airway dilator muscles appear to be sesntive to sedative hypnotic administration
- 2. protective laryngeal and pharyngeal reflexes are compromised by advanced age, debilitation anesthesia, and sedation
- 3. When opioids and benzos are used together there is consistent and negative effect on respiratory responsiveness
What is the single most vital monitor in the operative room during any type of anesthesia?!
a conscientious and well trained anesthesia caregiver
What assessments are necessary during MAC:
- 1. continuous visual, tactile, and auditory assessment of physical function
- 2. rate, depth, and pattern of respiration
- 3. palpation of arterial pulse
- 3. peripheral perfusion by temperature, cap refill
- 4. diaphoresis, pallor, shivering, cyanosis and acute changes in neuro status
What does a precordial stethoscope do for a nontintubated patient?
A precordial stethoscope near the sternal notch provides information concerning upper airway latency and continuous monitor of heart sounds and ventilation.
The use of pulse oximetry is important in MAC because:
- 1. noninvasive, safe, comfortable
- 2. simple to apply and interpret
- 3. SPECIFICALLY MANDATED BY ASA
- 4. used of pulse ox and capnometry can prevent adverse cardiac events and hypoxia
Why is capnography important in a nonintubated patient:
- 1. monitor respiratory rate and detection of airway obstruction
- 2. may reduce risk associated with sedation/analgesia, identifying more respiratory complications than standard monitoring alone
- 3. Currently NOT a standard of care
What is the minimum cardiovascular monitor for MAC?
The ECG must be continually displayed and the blood pressure recorded every 5 minutes. Pulse monitored by palpation, oximetry or auscultation.
Is temperature monitoring helpful during MAC?
Yes, because there is potential for significant inadvertent hypothermia especially with neuraxial anesthesia. Both the young and old have impaired thermoregulatory mechanisms. Mild hypothermia is associated with myocardial outcomes, increased bleeding tendencies, wound infections, and delayed wound healing.Defenses against hypothermia include shivering, vasoconstriction, and behavior. In the absence of temperature monitoring, the first indication of shivering may be considerable central cooling having already taken place.
Where is the most accurate positioned temperature monitor for neuraxial anesthetics?
properly placed axillary probe
Subjective sensation of hyperthermia can also be an indicator of what adverse events?
- 1. hypoxia
- 2. hypercarbia
- 3. cerebral ischemia
- 4. LA toxicity
- 5. myocardial ischemia
T or F: whenever propofol is used for sedation/anesthesia, it should be administered only by persons trained in GA, who are not involved in the surgical procedure.
What ASA class of patients are involved in claims?
ASA status III-V ages >70
T or F: MAC and GA cases claims are similar for death and permanent brain damage?
What is the most common respiratory damaging event in MAC cases?
inadequate oxygenation and ventilation
What is the most common equipment problem in MAC cases?
Cautery fires of the head and neck
What is the most commonly reported surgical related problem in MAC?
Patient movement or inadequate anesthesia
What is the most common respiratory mechanism of injury?
Respiratory depression as a result form oversedation
Close proximetry of supplemental oxygen use is associated with what?
Burns by use of electrocautery
What is a natural agonist to respiratory depression?
What kind of titration of opioids and sedatives is important to avoid respiratory depression?
VERY SLOW and titrate to effect
T or F: Capnography monitoring is required for MAC cases.
FALSE! capnometry monitoring is required for GA not MAC!
What three things are needed for a fire in the OR, name sources:
- 1. Oxidizer: oxygen N2O
- 2. Combustible substance: paper drapes, alcohol based prep solutions, plastic masks, Hair
- 3. Ignition: electrocautery
What steps can be used to minimize the incidence of on-patient fires?
- 1. open face draping
- 2.admin of O2 at lowest acceptable flow rates only when indicated by pulse ox
- 3. use of compressed air instead of oxygen to prevent buildup of CO2, stopping oxygen flow 60 s before use of electrocautery
- 4. avoidance of alcohol based prep solutions
- 5. awareness of the causation of surgical fire
Most common sources of injury during MAC:
- 1. severe respiratory depression resulting in death or brain damage associated with drugs used for sedation
- 2. burn injuries from fires caused by electrocautery in the presence of supplemental oxygen
Apnea lasting longer than 20 s is common in patients during MAC, what can be used to detect this?
- 1. precordial or esophageal stethoscope
- 2. BIS monitoring
The use of which medications causes depression of hypoxic ventilatory drive and can result in significant hypoventilation:
- 1. benzos
- 2. opiates
- 3. propofol
- 4. blunting of ventilatory response to CO2 by opioids and benzos