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105 Cards in this Set

  • Front
  • Back
What is the difference between sedation versus a general anesthetic?
Sedation does not include a loss of conciousness.
What is MAC?
Monitored anesthesia care. It's not as deep of sedation as GA. It's less physiological disturbing and has a more rapid recovery.

MAC implies the potential for a deeper level of sedation than that provided by just sedation/analgesia.


GA> MAC > Sedation/ analgesia
Why is MAC attractive over GA?
Should evoke less physilogical disturbance and promote more rapid recovery.
What is the context-sensitive half time?
The time it takes for the plasma content of a drug to decrease by 50% after an infusion of a particular duration ENDS.
What is one of the goals of MAC?
A patient that can cooperate, yet tolerate pain and have an amnesia.
Is it important to review what MAC is with a patient prior to the anesthetic?
Yes - the patient needst o be able to emotionally tolerate the level of wakefulness, what they can expect.
Will the patient have total pain relief during a MAC case?
Probably not - but it will be tolerable.
Does context sensitive half time describe well how long it will take a patient to recover from MAC?
Not directly...only time for plasma concentration to decrease by 50%.
T/F - No one inhaled or IV drug provides all the components of MAC (analgesia, anxiolysis, hypnosis) with an acceptable margin of safety or ease of titratability.
True
What is CPss50?
plasma concentration of a drug at steady state that is required to abolish purposeful movement at skin incision in 50% of patients.
A fentanyl conc. of 1.7 mg/ml reduces a MAC of Iso by __%.
A fentanyl conc. of 1.7 mg/ml reduces a MAC of Iso by 50%.

But once the fentanyl concentration is > 3 mg/ml, MAC reduction of ISO is minimal, with a max reduction of 80%.
When analgesic concentratins of fentanyl are used with propofol, the propoful requirement is reduced by _____ %.
Reduced by 50%

But there is no further decrease in propofol need when the fentanyl concentration is >3 mg/ml.
T/F: Significant changes in depth of sedation anesthesia can occur with modest increments in opioid or hypnotic/sedative changes.
True
T/F: During MAC anesthesia, the maximum benefit of opiod supplementation, in terms of potentiation of other administered sedatives, accrues when the opiod is used in the analgesic dose range.
True
Just observing a patient's responsiveness how can you tell if they are minimally, moderately, deeply or generally sedated?
Minimal sedation: Normal response to verbal stimulation
Moderate Sedation: Purpose response to verbal or tactile stimulation
Deep Sedation: Purposeful response to following repeated or painful stimulation
General Sedation- Unarousable, even with a painful stimulus.

(Taken from the continnum of depth of sedation scale)
At which level of sedation may airway intervention be required? Why?
Deep sedation; because at this level is when spontaneous ventilations may also be inadequate.
At which level of sedation may cardiovascular function be impaired?
General sedation
What classes of drugs are typically used for sedation, hypnosis and analgesia during MAC Cases? What are the typical doses?
BENZOS
Versed -1-2 mg prior to propofol or remifentanil infusion
Diazepam 2-8 mg a major component (2.5-10mg)

OPIOID ANALGESICS
Alfentanil 5-20 mcg/kg bolus 2 min prior to stimulus
Fentanyl 0.5-2.0 mcg/kg bolus 2-4 min prior to stimulus
Remifentanil: Start infusion at 0.1mcg/kg 5 min prior to stimulus
Wean to 0.05 mcg/kg as tolerated
Titrate up/down in 0.025 mcg/kg increments.
Reduce dose with given with versed or propofol.
Avoid boluses of remifentanil during infusion if at all possible due to respiratory depression risk.

HYPNOTICS
Propofol: 250-500 mcg/kg boluses; 25-75 mcg/kg/min infusions
Dexmedetomoidine/Precidex: Loading infusion 0.5-1.0 mcg/kg over 10-20 minutes and maintenance of 0.2-0.7-1 mcg/kg/hour
Why are opiods not effective solo agents for MAC?
High recall rate - lack adequate amnestic properties.
T/F: the greatest reduction in MAC of an inhalational agent with fentanyl usage is when fentanyl is given in its analgesic concentration range (1-2 mg/ml)
True
Are opiods and benzos synergistic?
YES - administration of an opiod and benzo drops requirements of each med to 25% OF EFFECTIVE DOSE to achieve hypnosis in 50% of patients
Do synergistic effects apply to only the sedative, hypnotic and analgesic effects of meds used in MAC?
No - they apply to the negative Side Effect as well..up to and including life threatening Side Effects.
What is the major SE associated with negative outcomes when midazolam is used?
Respiratory difficulties.
A combination of fentanyl and versed places a patient at increased risk of what?
hypoxemia and apnea
T/F: The respiratory depressant effects of versed and fentanyl together are independent of pt comorbidities.
False - they are amplified in patients with preexisting respiratory debility, CNS disease or extremes of age.
What are advantages and disadvantages of Propofol?
ADVANTAGES:
Short context-sensitive half time even with long duration infusion. Ideal sedative-hypnotic properties. Easily titratable with good recovery profile.
Does not have the prolonged psycohomotor and sedation of versed on recovery.
Propofol produces less PONV, sedation, drowsiness, confusion and clumsiness than versed.

DISADVANTAGES
little analgesic properties. Pain on injection. HOTN, Respiratory Suppression
What is an ideal method of analgesia when using propofol?
Local or regional anesthesia
Are benzos used commonly during MAC? Why/why not?
Yes - b/c of of their anxiolytic, amnestic and hypnotic properties

Versed is the most commonly used for conscious sedation.
Does the short elimination half time eliminate the post-op effects of versed?
Not really - patients still show a signifcant and prolonged psychomotor impairment follwing sedation using versed as a significant component.
T/F: versed is probably better used as part of a balanced technique.
True: Propofol probably best b/c it is titratable and can get hypnotic effect better matched to stimulus.
The analgesic portion could be provided by regional/local tech. or opioids.
Lower doses of benzos should be used in ______ populations.
elderly
Benzos have what effect on patients?
Enhance pt comfort, improve operating conditions, provide amnesia.

Long time to recover. Higher risk of post op recovery dysfunctions.
Why is benzo sedation not preferred?
Solo benzo use results in longer recovery times as well as psychomotor and cognitive fx.
T/F: Flumazenil can improve benzo recovery times but entails significant SE.
FALSE: Flumazenil (romazicon) provides potential to improve benzo recovery with active termination of sedative and amnestic effect WITHOUT adverse side effects.
What is one caution the anesthesia provider should take when reversing benzos with romazicon?
Assessment of resedation - which can occur up to 90 minutes post reversal.

This is a bigger issue in patients undergoing ambulatory surgery.

PLUS: Use of romazicon is costly - much more costly than propofol sedation or balanced technique.
What is the recommended initial dose of Romazicon?
0.2 mg

Repeat in 45s if needed.

May repeat 0.2 mg doses every 60s (max dose 1 mg) prn

Be aware of resedation
What role do opioids play in the balanced technique of MAC?
Analgesia - obviously

Should not be used for sedation.
During a retrobulbar block patient must be_______ & _________.
Cooperative and Motionless
Why is alfentanil a better choice for retrobulbar block placement than methohexital?
Intense onset and offset of analgesia and enough wakefulness to remain cooperative.

Methohexital produced more drowsiness and many patients are prone to movement.
Why is alfentanil a good choice for discrete painful stimuli?
B/C of its short effect-site equilibration time meaning the drug gets to the brain quick and can be easily titrated.

Sufentanil better for prolonged procedure b/c of its shorter context sensitive halftime.
What are some SE of opioids that can be problematic in MAC?
respiratory depression, muscle rigidity and weakness.
What are some advantages to Remi-fentanyl?
-Similar pharmacodynamics to other potent mu-opioid receptor agonists (fentanyl, alfentanil)
-Metabolism by nonspecific esterases produces rapid clearance and offset of effect.
-Context sensitive half-time is consistently short: 3-5 minutes.
-Short effect site equilibration: 1-1.5 minutes.
-Can titrate to effect with minimal respiratory effects
-Adverse respiratory effects are generally resolved in a few minutes when infusion is stopped.

Therefore, it gets on and off fast and it is easy to titrate to effect. This makes it good for ambulatory MAC cases.
How does Remifentanyl + versed effect dosage?
Reduces remifentanil dosage by 50%


This allows a lesser amt of respiratory suppression.
Should you ever give normal IV push Remi-fentanyl?
Not recommended - can cause respiratory depression.

Boluses should be given over 60-90 seconds or avoided altogether (give with infusion).
When would a Remi bolus be warranted?
Right before a brief but very painful stimulus...like placing retrobulbar block (1mcg/kg over 30s)
Does 2mg versed impact remi dose?
yes - significantly decreases them by about half.
What is the most logical method of remi administration?
Titratable infusion preceded by small bolus of versed.

-Start infusion at 0.1mcg/kg/min 5 min before painful stim. Wean to 0.05 mcg/kg/min for patient comfort and maintenance. Titrate in 0.025 mcg/kg/min increments to effect.
What is a potential danger with remifentanil infusion preparation?
It comes as a powder that has to be reconstituted. Be careful that the solution is not too strong or patient overdose can occur. That is a dosing error.
T/F: Ketamine produces intense analgesic effects and is useful in peds populations.
True
What is an well documented advantage of ketamine?
It has minimal respiratory and CV depression.

However it can cause CV overstimulation and increase HR, BP, and ICP.
What sort of anesthesia does ketamine produce?
Disassociative - eyes open with nystagmus. patient may have spontaneous limb movements.
What drugs are often combine with ketamine?
Glycopyrolate/atropine - to dry up increased oral secretions/decrease risk of laryngospasm.

Versed - to decrease hallucinations.
Given IV, how do you give Ketamine?
In small (0.25 - 1.0 mg/kg) doses.
What class of med is dexmedetomidine?
selective alpha-2 agonist: depresses CNS fx to produce sedation and analgesia.

-Potentiates opioid induced analgesia, benzo-induced hypnosis, and is potently MAC-sparing with inhalants.
Advantages of Dex?
-Produces sedation AND analgesia
-Minor effects on resp fx
-Preserved hypercapneic response
-patient comfort and cooperativeness during fiberoptic intubation
-Tends to decrease cerebral blood flow AND cerebral met rate.
Major SE of Dex?
Hypotension and bradycardia s/t to increased cardiac vagal activity.

It can case periph vasoconstr. that leads to HTN.
Uses of Dex?
MAC during awake portions of craniotomy.
Sedative supplement to regional anesthesia during carotid endartectomy.
Doses for Dex
0.5-1.0 mcg/kg over 10-20 minutes loading dose
0.2-0.7mcg/kg/hours infusion
What are limiting factors of DEX?
May not be good for brief procedures b/c of time needed to load the med, occasinal need to rebolus, hypotension, bradycardia, and rel. long recovery time may not make it a good choice for brief procedures.
Compare the amnestic effects of propofol and Dex.
Propofol has significant amnestic effects at subhypnotic doses.

Dex is unlikely to have amnestic properties at subhypnotic doses. To achieve that with Dex, the dose given would render the patient unconscious and then you have a GA and unsecured airway.
Compare the analgesic properties of propofol and Dex.
Propofol has little/no analgesic effects at subhypnotic doses.

Dex has significant analgesic effect at subhypnotic doses.
The big SE of Dex?
Bradycardia and Hypotension
What should the anesthesia provider be looking for if patient becomes agitated?
FIRST: Hypoxia

THEN,
-Hypercarbia
-Impending local anesthetic toxicity (know your agents window of toxicity to anticipate impending cardiac toxicity)
-Cerebral hypoperfusion
-Distended bladder (uncomfortable)
-Hypo-/hyperthermia
-Nausea
-Claustrophobia - happens a lot in MAC with draping of the head.
What are the max doses of xilocaine?
4 mg/kg without epi
2 mg/kg with epi
What regional anesthesia med has a high risk of rapid onset cardiac toxicity?
Marcaine (Sanofi, Bupivacaine HCl): don't exceed 2.5-3.0 mg/kg with or without epi.
What is better for maintaining desired levels of anesthesia during MAC - boluses or continual infusions.
Continual infusions

It avoids the peaks and troughs associated with excessive sedation and inadequate sedation with bolus-ing.
Protective airway reflexes are compromised by what?
Anesthesia & sedation, debilitation and advanced age.
How long is the swallowing reflex impaired, after return to consciousness, for diprivan/versed/diazepam?
Diprivan - 15 minutes
Versed - 2 hours
Diazepam - 4 hours
T/F: When opioids and benzos are used in combination, there is a consistent and marked negative effect on respiratory responsiveness.
True
Why should you always check the oxygen saturation of the patient before taking them to the recovery/discharge area without O2?
B/C even with minimal supplemental oxygen in the OR suite, alveolar hypoventilation can be masked. This can cause problems if the patient is taken off O2 in recovery area.
Patients who are risk of aspiration of gastric contents should be maintained at the _________ level of sedation possible.
Patients who are risk of aspiration of gastric contents should be maintained at the lightest level of sedation possible.
What is the trade name for methohexital?
Brevital
T/F: per Tab, brevital is a good choice with remifentanil or alfentanil.
True
In addition to the normal ASA standard of monitoring that apply to all cases, what type of monitoring concerns are associated with MAC cases?
COMMUNICATION & OBSERVATION: continually eval pt response to verbal stim to titrate level of sedation/allow earlier detection of neurologic or cardiorespiratory dysfunction. Observe rate, depth and quality of respirations.
Palpate arterial pulses and periphery to assess perfusion via cap refill and temp. Monitor for acute changes in neuro status.

AUSCULTATION: Precordial stethoscope at sternal notch. Can get some wireless FM transceivers if not able to have access to patient.

PULSE OX - very important b/c of compromised resp fx r/t the effects of sedatives and opioids on resp drive/upper airway patency/protective reflexes. Respiratory events constitute the largest single source of adverse outcomes in MAC. Pulse oximetery can help prevent these in most cases.

CAPNOGRAPHY: good info on patient respirations, but UNRELIABLE ETCO2 VALUE. If no CO2 cannula, can shorten an IV catheter, attach to sampling line and put in regular NC.

CV: Continuous EKG, min q5 min BP checks during MAC, pulse by oximeter/palpation/auscultation

TEMP:
---> shivering and vasoconstriction are impaired during major conduction anesthesia
---> hypothermia is associated with regional/neuraxial anesthesia (LE vasodilation diverts blood from core to periphery producing cooling, afferent input to hypothalamus from warm periphery works against input from cooling core to delay warming responses);
---> MAC w/ regional in extremes of age can cause hypothermia (Elderly have less thermoreg, less mass for heat production).
--> Use forced heated air (Bair hugger), warm blankets and warm fluids. Keep OR temp reasonable.
---> Hypothermia of as little as 1-2 degC is assoc w/adverse myocardial outcomes, increased bleeding and transfusions, increased wound infections, delayed wound healing and hospital discharge. --->Hyperthermia is rare: esp MH, but some patients can experience this from thyroid storm or malignant neuroleptic syndrome.

BIS: may allow for more accurate titration of drugs. BIS value of <80 associated with absence of recall.
Why is preparedness to treat local anesthetic toxicity so critical?
Everyone is at risk, but often this is provided to patients who are elderly, have co-morbidities that preclude GA or both - placing them at greatest risk of the effects of LA toxicity

Atropine, Fluids
When does LA toxicity occur?
When the rate of absorption from the tissues into circ exceeds its clearance from the circulation.
Describe the progression of LA sx.
At low concentrations: circumoral tingling and numbness, metallic taste in mouth.

As concentration rises: restlessness,,vertigo, tinnitus, difficulty focusing.

At high concentrations: slurred speech and skel muscle twitching --> tonic/clonic siezures are not far behind.
How does MAC anesthesia place patient at risk of LA toxicity?
*MAC anesthesia may slow CO which decreases both hepatic and renal perfusion which prolongs LA clearance from the circulation.

*Sedation of patient can increase hypercarbia. This vasodilates the cerebral vasculature. Amt of LA going to brain increases along with increased cerebral perfusion due to hypercarbia.

*Hypercarbia also decreases cerebral neuronal pH - this acidity increases the active ionized form of the local LA in the brain.

*Therefore, Hypercarbia, acidosis and hypoxia markedly potentiate the CV toxicity of LAs.

* Sedative hypnotics interfere with pt ability to communicate s/s of neurotoxicity. (BUT anticonvulsant properties of benzos and barbs may attenuate siezures of LA neurotox.)

*It is possible that MAC may mask the NEUROLOGICAL S/S of LA toxicity, therefore S/S cardiotoxicity can be the first to appear...esp when bupivicaine (Marcaine) is being used.
What are the 4 levels and parameters of the continnum of Depth of Sedation scale
4 levels: Minimal, Moderate, Deep, General

4 parameters: Responsiveness, Airway, Spontaneous Ventilation, CV function.
If you find your patient in deep sedation, what is a major concern?
You are on the verge of needing an adjunct airway and you may need to consider moving to a GA.
What can the anesthesia provider do to minimize adverse outcomes of MAC?
It is all about vigilance:
Minimize distractions
Pay close attention to the patient's response
Routinely administer supplemental oxygen.
Have at least one person trained in ACLS available.
Ensure that appropriate emergency equipment is readily available...esp for establishing and maintaining an airway with pos press vent and O2.
Maintain a reliable IV until patient is no longer at risk for cardio resp depression.
Why is verbal comm with patient important?
-Monitor level of sedation & cardiorespiratory fx
-Explain and reassure patient
-Communication when patient is required to cooperate.
If a patient has a condition like a cough that prevents them from remaining still, will MAC sedation fix that?
Likely not...the level of sedation required to abolish a cough would make it dangerous to have an unsecured airway and would cross into GA territory.
Would MAC be a good choice for people with orthopnea or CV compromise?
No - b/c they could not lay still or flat due to the dyspnea it would produce.
What are the relative context sensitive half-times of the commonly used MAC meds greatest to least?
Fentanyl
Thiopental
Midazolam
Alfentanil
Su-fentanil
Propofol
The effects of the initial dose of most drugs used in anesthesia practice is determined by what?
Redistribution - which depends on blood flow to to redistribution sites.

Low CO can lead to delayed initial onset for IV drugs, but not for inhaled drugs

The dangerous adverse effects of these meds are likely to be delayed AND prolonged with IV drugs, faster for inhaled drugs. .

START LOW AND GO SLOW: Careful small well-spaced boluses should be given with extra time for meds to take effect in order to get appropriate level of sedation.
How does rate of return and metabolism affect context sensitive half time?
When infusion is stopped, drugs vary in their rate of return from lipophilic tissues and also in their metabolism once back into the central circulation.
How do plasma levels at time of infusion cessation impact recovery?
If the patient has been maintained in the "ideal therapeutic range", they have a relatively rapid time to awakening.

If patient has been oversedated, even with same rate of return from tissues and metabolism once in central circulation, time to awakening can be greatly increased.
Are effect site concentrations the same in all compartments?
No - the brain, cardiac, renal and pulmonary and hepatic tissue all have different effect site concentrations.
Is polypharmacy neccessary in MAC?
Yes.
What are the advantages and disadvantages of synergy in MAC?
Adv - enhanced effect for each drug allows less of each to be used to the same end-effect.

Disadv - increases variability in patient response and risk for undesirable interactions (these are dose dependent)
T/F: Deep sedation never occurs with fentanyl+versed administration.
FALSE - administration of fentanyl and versed increase likelihood of deep sedation.
What is the primary concern when coadministering opioids and benzos?
Cardiorespiratory depression
Is valium (diazepam) used much anymore?
No - it lasts too long.
Does versed alone produce adverse respiratory effects in healthy patients?
Per Tab's lecture, midazolam alone has no significant respiratory depressant effects.
What patients are more susceptible to the adverse synergistic effects of opioid + benzo combo tx?
Patients with sleep apnea are much more sensitive.
What is a positive SE of propofol?
Antiemitic properties (with as little as a 10 mg dose)
What is the most commonly used benzo for MAC (or in general anesthesia)?
versed/midazolam
How is versed commonly given?
1-2 mg preop
0.5 MG incremental boluses for healthy patients.
What is a good combo as anesthesia for a local injection?
Fentanyl + propofol

Also helps with pain associated with positioning, tourniquets, propofol inj pain.
Is there a good propofol + ketamine combination?
1 mg ketamine per ml propofol

Richard calls this "white lightning".

Requires smaller doses of each. You get the amnesia of the propofol. The ketamine is a good respirogenic and it has good cardiac safety.
What is a practical downsides to Remifentanil and Dex?
They are not yet generic - so they are costly.
Why is airway maintenance such a high priority in MAC?
B/C you have a centrally mediated respiratory depression.

The patient's ventilatory response to both CO2/O2 is blunted.

The dilator muscle of the upper airway is impaired.

Many patients getting MAC have extreme age or debility (why they cannot get GA).
If your patient is hypoxic, should you put 100% O2 on them immediately during a MAC case?
Not necc - often a modest increase in FiO2 is sufficient (2L NC).
What are the s/sx of hypercapnea?
1) Increased ETCO2: Mild to moderate: 45-60 mmHg ETCO2
2) Tachycardia, Tachypnea: when ETCO2 >60: cardiac and resp symptoms appear
3) Enhanced sedation