Barash Chap 31
|If the level of sedation is deepened to the extent that ____ ____ is lost, most of the advantages of MAC are lost & the risks of the technique approach those of ____ ____ with an _____ & _____.|| verbal communication |
unprotected & uncontrolled airway.
|What should be done to avoid excessive levels of sedation?|| Drugs should be titrated in small increments or by adjustable infusions rather than administered in larger doses|
according to predetermined notions of efficacy.
|The context-sensitive half-time|| The time required for the plasma drug|
concentration to decline by 50% after terminating an infusion of a particular duration.
| During monitored anesthesia care, the maximum benefit of opioid supplementation, in terms|
of potentiation of other administered sedatives, will accrue when the opioid is used in the ____ ____ ___. Within this dose range there is great potential for adverse ______ interaction.
| analgesic dose range|
|The important mechanisms whereby respiratory function may be compromised during MAC include the effects of sedatives & opioids on ____ ____, ____ ___ ____. & ___ ___ _____.||respiratory drive, upper airway patency, & protective airway reflexes.|
|What does MAC usually involve?|| The administration of drugs w/ anxiolytic,|
hypnotic, analgesic, & amnestic properties, either alone or as a supplement to a local or regional technique.
|What does MAC imply?||The potential for a deeper level of sedation than that provided by sedation/analgesia & is always administered by an anesthesiologist provider. The standards for preop eval, intraop monitoring, & the continuous presence of a member of the anesthesia care team, & so forth, are no different from those for general or regional anesthesia|
|What is important to evaluate in the preop assessment for a MAC case?||The patient's ability to remain motionless &, if necessary, actively cooperate throughout the procedure.|
|During the preop assessment for MAC, it is also important to elicit the presence of ______ _______ or _____ _____.||coexisting sensorineural or cognitive deficits.|
|A variety of medications are commonly administered during monitored anesthesia care with the desired end points, what are they?||Providing patient comfort, maintaining cardiorespiratory stability, improving operating conditions, & preventing recall of unpleasant perioperative events.|
|Clinical experience suggests that a level of sedation that allows is _____ ______ optimal for the patient's comfort and safety.||verbal communication|
|Why are continuous infusions superior to intermittent bolus dosing?|| Because they produce less fluctuation in drug concentration -> reduced number of episodes of inadequate or excessive sedation|
Reduces the total amount of drug administered & facilitates a more prompt recovery.
|Following the administration of IV anesthetic drugs, the immediate distribution phase causes a brisk decrease in plasma levels as the drug is transported to the rapidly equilibrating _____-____ ____ of ____. There is a simultaneously occurring distribution of drug to the ____ ____-____ ____ such as ___ & ____.|| vessel-rich group of tissues.|
less well-perfused tissues
muscle & skin
|What occurs over time after the administration of IV anesthetic drugs?||The drug is also distributed to the poorly perfused tissues such as bone & fat.|
| Bone & fat are poorly perfused, & may _____ significant amounts of ______ drugs during _____|
This peripheral depot may contribute to a ___ ____ when the drug is eventually released back into the ____ _____ after its administration is discontinued.
| accumulate |
| What factors are important|
determinants of drug effect and influence the plasma concentration of a drug in a time-dependent fashion?
|In a single-compartment model, ____ is the only process that can alter drug concentration.||elimination|
|What does the context-sensitive half-time reflect?||The combined effects of distribution & metabolism on drug disposition.|
|As the ____ ____ increases, the _____-_____ _____-_____ of all the drugs increases.|| infusion duration|
| The context-sensitive half-time is not the sole determinant of the|
time it takes for the patient to awaken. The time to
awakening is determined in addition by the difference in concentration at the _____ of the _____ and the concentration below which _____ will occur.
| end of the procedure|
|The t1/2ke0 for fentanyl is ____ minutes compared with a t1/2ke0 of ____ minutes for alfentanil.|| 6.4|
|t1/2ke0 of midazolam||0.97 to 5.6 minutes|
|A low ____ ___ will markedly delay drug arrival at the site of action.||cardiac output|
|The effects of initial doses of most drugs in anesthetic practice are terminated by _____, which depends on ____ ____ to redistribution sites.|| redistribution|
|At the present time, no one inhaled or IV drug can provide all the components of monitored anesthesia care (i.e., _____, _____, & _____) with an acceptable margin of safety or ease of titratability. Therefore, patient comfort is usually maintained with a ____ of ____.|| analgesia, anxiolysis, & hypnosis|
combination of drugs.
|By acting ______, combinations of drugs enable reductions in the dose requirements of individual drugs.||synergistically|
|Disadvantages of synergistic interactions?|| May also extend to the undesirable|
interactions of the drugs such as cardiorespiratory depression.
|Cpss50|| The plasma concentration of a drug at steady state that is required to abolish purposeful movement at skin incision in 50% of patients|
A measure of potency that is analogous to the familiar parameter of MAC of the volatile inhaled anesthetics.
| During general anesthesia, opioid|
requirements to suppress the responses to noxious stimuli are ___ ___ when used as the sole agent
compared w/ when they are used in conjunction w/ a N20/potent inhaled vapor technique.
|What drug combination displays marked synergism in producing hypnosis?||Opioids & benzos|
| The combination of _____ & ____|
places patients at high risk for developing hypoxemia and apnea.
|midazolam & fentanyl|
|Propofol has many of the ideal properties of a sedative-hypnotic for use in MAC, what are they?||A context-sensitive half-time that remains short even after infusions of prolonged duration & a short effect-site equilibration time makes it an easily titratable drug w/ an excellent recovery profile. Low incidence of N&V.|
|Compare advantages of propofol over benzos|| Propofol is noted for the rapid return to clear-headedness, faster recovery & return of psychomotor function|
Midazolam is associated w/ prolonged postop sedation & psychomotor impairment
|Sedation||Sleep w/ preservation of the eyelash reflex & purposeful reaction to verbal or mild physical stimulation|
| Subhypnotic doses of propofol (a single 10-mg dose in|
an adult) possess direct _____ properties.
|Benzodiazepines are commonly used during monitored anesthesia care for their ____, ____, & ____ properties.||anxiolytic, amnestic, & hypnotic|
|Why do the doses of benzos need to be reduced in the elderly?|| There is a threefold decrease in plasma|
concentration of midazolam in an 80-year-old patient compared w/ a 40-year-old patient
|Cp50||The concentration at which 50% of subjects will fail to respond to a verbal command|
| The effects of midazolam may recur up to ____ ____ following the|
administration of flumazenil.
|Compare the important properties of midazolam & diazepam||Midazolam: H20 soluble, nonvenoirritant, thrombophlebitis rare, short elimination 1/2 life (1-4h), clearance unaffected by H2 blockers, inactive metabolites, resedation unlikely|
Diazepam: lipid soluble, venoirritant, thrombophlebitis, long elimiation 1/2 life (>20 h), clearance reduced by H2 blockers, active metabolites, poss resedation.
|What are the active metabolites of diazepam?||Desmethyldiazepam & oxazepam|
| Recommended Regimen for the Use of Flumazenil To Antagonize|
| Initial recommended dose of 0.2 mg|
If desired LOC isn't achieved in 45 s, repeat 0.2-mg dose
0.2-mg doses may need to be repeated every 60 s until a max of 1 mg is administered
Be aware of the potential for resedation
|Indications of opioids||Used when regional or LA techniques are inappropriate or ineffective. |
Play an important role during the initial injection of LA solution or during other periods of intense patient discomfort.
Pain relief for factors other than the procedure itself, such as uncomfortable
positioning, propofol injection, pneumatic tourniquet pain, or other pain not relieved by the LA technique.
|Describe the advantages of alfentanil over sufentanil||It has a pharmacokinetic advantage for the treatment of discrete stimuli because of its short effect-site equilibration time, which allows rapid access of the drug to the brain & facilitates titration.|
|Describe the advantages of sufentanil over alfentanil||It has a more favorable recovery profile when used over a longer period because of its shorter context-sensitive half-time.|
|Describe the pharmacodynamic properties of remifentanil|| Predominantly metabolized by nonspecific esterases generating an extremely rapid clearance & offset of effect.|
Context-sensitive half-time of 3-5 min
Short effect-site equilibration time (t1/2ke0) of 1.0-1.5 min.
|Advantages of coadministration of small doses of midazolam w/ opioids||Increased patient satisfaction, increased amnesia, decreased N/V, & decreased anxiety.|
|Disadvantages of coadministration of small doses of midazolam w/ opioids|| Tendency toward increased respiratory depression, apnea, & excessive|
|Remifentanyl infusion rates||Start at 0.1 μg/kg/min ~5 min prior to the 1st painful stimulus. This initial "loading" infusion is then weaned to ~0.05 μg/kg/min to maintain patient comfort.|
|Ketamine|| A phencyclidine derivative |
An intense analgesic
Frequently used as a component of
pediatric sedation techniques.
| When used in small doses (0.25 to 0.5 mg/kg) its use is associated w/|
minimal ____ & ___ ____.
|respiratory & cardiovascular depression.|
|What does ketamine produce?|| A dissociative state in which the eyes|
remain open w/ a nystagmic gaze.
|What is the cause of increased risk of laryngospasm w/ ketamine?||Increased oral secretions|
|What is commonly given w/ ketamine d/t the fear of laryngospasm?||Atropine or glycopyrrolate|
|What is given along w/ ketamine to reduce the incidence of hallucinations?||Benzos|
|When is ketamine avoided in or contraindicated in?|| In procedures requiring a completely|
C/I in patients w increased intracranial pressure & w/ glaucoma or open-globe injuries (can elevate ICP & IOP)
|Dose, onset, & duration of oral ketamine|| Dose: 4-6 mg/kg|
OOA = 20-30 min
DOA = 60-90 min
|Dose, onset, & duration of IV ketamine|| Dose: 0.25-1.0 mg/kg increments|
OOA = 1-2 min
DOA = 20-60 min
|Dexmedetomidine||A selective α2 receptor agonist.|
|MOA of dexmedetomidine|| Stimulation of α2 receptor depresses central sympathetic|
function and produces sedation and analgesia.
|Unlike during opioid-induced sedation, the ____ ____ ____, a feature of natural sleep, appears to be preserved during dexmedetomidine sedation.||hypercapnic arousal response|
|What may occur during dexmedetomidine administration & why|| Hypotension & bradycardia|
Administration of α2 agonist is
associated w/ a reduction of sympathetic outflow & an increase in cardiac vagal activity
|What are the advantages of dexmedetomidine over propofol?||Results in greater sedation, lower BP, & improved analgesia in the recovery room|
|In contrast to propofol & benzos, what does dexmedetomidine lack?||Amnestic properties at subhypnotic doses|
|The pharmacokinetic profile of alfentanil is ideal for the treatment of ____, ____ ____ of ____.||short, discrete episodes of pain.|
|Effects of MAC on respiratory function|| Adverse effects on respiratory drive, directly as a result of sedative-|
hypnotic or opioid administration or indirectly as a consequence of brain stem hypoperfusion d/t hypotension (w/ spinals or epidurals).
Marked increases in the WOB d/t increased upper airway resistance.
|The upper airway is located outside the thorax. During normal inspiration, the pressure within the upper airway is _____; thus, there is a tendency for the upper airway to ____ under the influence of the surrounding ____ _____.|| subatmospheric|
|Complete recovery of the swallowing reflex occurs approximately ____ ____ after the return of consciousness following propofol anesthesia.||15 minutes|
|IV administration of 15 mg of diazepam has been shown to depress the swallowing reflex for up to ___ ____.||4 hours|
| The swallowing reflex is|
significantly depressed for up to ___ ____ following the administration of midazolam despite the return to a normal state of consciousness.
|In otherwise healthy adult male volunteers the inhalation of ___% nitrous oxide was associated with marked depression of the swallowing reflex.||50%|
|A patient who is receiving minimal supplemental oxygen and has an acceptable oxygen saturation may have significant ____ ___ ____.||undetected alveolar hypoventilation|
|What is the single most vital monitor in the operating room?||A conscientious and well-trained anesthesia caregiver|
|What does the pulse ox allow?||Continuous real-time monitoring of arterial oxygenation|
|Risk factors for arterial desaturation|| Obesity, pre-existing upper airway|
obstruction & respiratory disease, the extremes of age, & the lithotomy position.
|What frequently heralds the onset of cardiac arrest?||Cyanosis|
|At a minimum, the ___ must be continually displayed and the ___ ____ & ____ at least every ____ ____ during monitored anesthesia care.|| ECG|
BP measured & recorded
| Effects of mild perioperative hypothermia (i.e., 1 to 2°C) accompanying general|
| Adverse myocardial outcomes, increased bleeding tendency & transfusion|
requirements, wound infections, & delayed
wound healing & hospital discharge.
| What are the major thermoregulatory|
defenses against hypothermia?
|Vasoconstriction, shivering, and behavior.|
|What is impaired during major conduction anesthesia?||Vasoconstriction & shivering|
|How does regional anesthesia affect thermoregulation?||Lower extremity vasodilatation causes|
central cooling via a redistribution of heat from the core to the periphery. Afferent input to the hypothalamus from
the warm peripheral compartment counteracts conflicting input from the cooling central compartment, which delays the initiation of compensatory thermoregulation.
|During monitored anesthesia care, hyperthermia is still possible as a result of ___ ___ or ___ ___ ____.||thyroid storm or malignant neuroleptic syndrome|
|Absence of recall was associated with BIS values below ___.||80|
| The clinically recognizable effects of local anesthetics on the central nervous system are|
concentration-dependent. What symptoms occur at low concentrations?
|Sedation & numbness of the tongue & circumoral tissues & a metallic taste are prominent features.|
| The clinically recognizable effects of local anesthetics on the central nervous system are|
concentration-dependent. What symptoms occur as concentrations increase?
|Restlessness, vertigo, tinnitus, & difficulty focusing|
|What do higher concentrations of LAs result in?||Slurred speech & skeletal muscle twitching, which often herald the onset of tonic-clonic seizures|
|How does hypercarbia affect the margin of safety for LAs?|| By increasing CBF, hypercarbia will increase the amount of LA that is delivered to the brain -> increases the potential for neurotoxicity. |
By reducing neuronal axoplasmic pH,
hypercarbia increases the intracellular concentration of the charged, active form of LA ->toxicity.
|What factors markedly potentiate the cardiovascular toxicity of local anesthetics?||Hypercarbia, acidosis, and hypoxia|
|What drugs may attenuate the seizures associated with neurotoxicity?||Benzos & barbs|