Lippincott Chapter 13: Anaesthetics Flashcards
13.1 Which of the following is a potent analgesic but a weak
anesthetic?
A. Etomidate.
B. Halothane.
C. Midazolam.
D. Nitrous oxide.
E. Thiopental.
Correct answer = D. Etomidate is a hypnotic agent but lacks
analgesic activity. Midazolam is a common sedative/amnes-
tic. Halothane and thiopental are potent anesthetics with
weak analgesic properties. Nitrous oxide provides good
analgesia but is a weak anesthetic that must be combined
with other agents to provide complete anesthesia.
13.2 The potency of inhaled anesthetics is defined
quantitatively as:
A. Blood/gas partition coefficient.
B. Cerebrovascular resistance.
C. Minimum alveolar concentration.
D. Diffusion hypoxia.
Correct answer = C. Potency of inhaled anesthetics is
defined by MAC, equivalent to the median effective dose
(ED50) of the anesthetic. Blood/gas partition coefficient
determines solubility of the gas in blood. Cerebrovascular
resistance is decreased by inhalation anesthetics. Diffusion
hypoxia is associated with nitrous oxide.
13.3 Which of the following determines the speed of recovery
from intravenous anesthetics used for induction?
A. Liver metabolism of the drug.
B. Protein binding of the drug.
C. Ionization of the drug.
D. Redistribution of the drug from sites in the CNS.
E. Plasma clearance of the drug.
Correct answer = D. Following initial flooding of the CNS
with nonionized molecules, the drug diffuses into other tis-
sues. With secondary tissue uptake, the plasma concentra-
tion falls, allowing the drug to diffuse out of the CNS. This
initial redistribution of drug into other tissues leads to the
rapid recovery seen after a single dose of an IV induction
drug. Protein binding, ionization, and lipid solubility affect
the rate of transfer.
13.4 Which one of the following is a potent intravenous
anesthetic but a weak analgesic?
A. Propofol.
B. Benzodiazepines.
C. Ketamine.
D. Fentanyl.
E. Isoflurane
Correct answer = A. Propofol is a potent anesthetic but a
weak analgesic. It is the most widely used intravenously
administered general anesthetic. It has a high lipid solubil-
ity. The other choices do not fit this profile.
13.5 Which of the following is correct regarding local
anesthetics?
A. They affect only small, unmyelinated nerve fibers.
B. They have either a lipophilic or a hydrophilic group.
C. They have either an amide or an ester linkage.
D. They are unaffected by pH of the tissue and pKa of
the drug.
E. In their ionized form, they interact with the protein
receptor of calcium channels.
Correct answer = C. The small, unmyelinated nerve fibers
that conduct impulses for pain, temperature, and autonomic
activity are most sensitive to the action of local anesthet-
ics, but other nerve fibers are affected also. Local anes-
thetics have a lipophilic group, joined by either an amide
or ester linkage to a carbon chain that, in turn, is joined to
a hydrophilic group. Onset and duration of action of local
anesthetics are influenced by both pH of the tissue and pKa
of the drug. Local anesthetics work by blocking sodium ion
channels.
13.6 Which of the following is correct regarding malignant
hyperthermia?
A. It is triggered by dantrolene.
B. It is triggered by local anesthetics.
C. It is generally mild and clinically insignificant.
D. It has no familial component.
E. It involves increased skeletal muscle oxidative
metabolism.
Correct answer = E. Malignant hyperthermia involves
increased skeletal muscle oxidative metabolism and is a
life-threatening condition. Dantrolene is the specific phar-
macologic treatment. Local anesthetics have been shown
to be safe. Triggering agents include succinylcholine and
halogenated hydrocarbon volatile anesthetic agents in sus-
ceptible individuals. Susceptibility to malignant hyperther-
mia is inherited in an autosomal dominant fashion.
13.7 A patient with heart failure and significantly reduced
cardiac output requires surgical anesthesia. Which of
the following would you expect to see in this patient?
A. Slower induction time with IV anesthetics.
B. Need for increased dosage of IV anesthetics.
C. Slower induction time with inhaled anesthetics.
D. Enhanced removal of inhaled anesthetics to
peripheral tissues.
Correct answer = A. When cardiac output is reduced, the
body compensates by diverting more cardiac output to the
cerebral circulation. A greater proportion of the IV anes-
thetic enters the cerebral circulation under these circum-
stances. Therefore, the dose of the IV drug must be reduced
(not increased). Also, with reduced cardiac output, it takes
a longer time for an IV induction drug to reach the brain,
resulting in a slower induction time. For inhaled anesthetics,
lower cardiac output removes anesthetic from the alveoli to
the peripheral tissues more slowly and thus enhances the
rate of rise in alveolar concentration of gas. Therefore, the
gas reaches equilibrium between the alveoli and the site of
action in the brain more quickly.
13.8 An 80-year-old patient with asthma and low blood
pressure requires anesthesia for an emergency surgical
procedure. Which of the following agents would be most
appropriate for inducing anesthesia in this patient?
A. Desflurane.
B. Ketamine.
C. Propofol.
D. Thiopenta
Correct answer = B. Ketamine may be beneficial since it is a
potent bronchodilator and may not lower blood pressure like
other agents. Desflurane is an inhaled anesthetic that may
stimulate respiratory reflexes. It is used for maintenance,
not induction, and may lower blood pressure. Propofol may
also decrease blood pressure. Thiopental is a short-acting
barbiturate that can cause bronchospasm.
13.9 A 52-year-old woman will be undergoing sedation with
propofol for a brief diagnostic procedure. Which of the
following is an advantage of propofol for this patient?
A. Rapid analgesia.
B. Sustained duration.
C. Decreased incidence of nausea and vomiting.
D. Less pain at the injection site.
Correct answer = C. Propofol has some antiemetic effect,
so it does not cause postoperative nausea and vomiting. It
has a short duration of action (which makes it good for brief
procedures), but does not produce analgesia. Pain at the
injection site is common.
13.10 A 32-year-old woman requests an epidural to ease
labor pains. She reports that she had an allergic
reaction to Novocain (procaine) at the dentist’s office.
Which of the following local anesthetics would be
appropriate for use in an epidural for this patient?
A. Chloroprocaine.
B. Mepivacaine.
C. Ropivacaine.
D. Tetracaine.
Correct answer = C. Procaine is an ester local anesthetic.
Since this patient has an allergy to procaine, other ester
anesthetics (chloroprocaine, tetracaine) should not be
used. Mepivacaine, an amide local anesthetic, should not
be used due to the potential for increased toxicity to the
neonate. Ropivacaine is an amide anesthetic.
