CNS 4 Flashcards
- ___ (wood alcohol), a constituent of windshield cleaners and “canned heat,” is sometimes ingested intentionally.
- Intoxication causes visual dysfunction, gastrointestinal distress, shortness of breath, loss of consciousness, and coma.
- is metabolized to formaldehyde and formic acid, which causes severe acidosis, retinal damage, and blindness.
Methanol
The formation of formaldehyde is reduced by prompt intravenous administration of ____, an inhibitor of alcohol dehydrogenase, or ____, which competitively inhibits alcohol dehydrogenase oxidation of methanol.
- fomepizole
- ethanol
A 45-year-old moderately obese man has been drinking heavily for 72 h. This level of drinking is much higher than his regular habit of drinking 1 alcoholic drink per day. His only significant medical problem is mild hypertension, which is adequately controlled by metoprolol. With this history, this man is at significant risk for
Arrhythmia
A 42-year-old man with a history of alcoholism is brought to the emergency department in a confused and delirious state. He has truncal ataxia and ophthalmoplegia. The most appropriate immediate course of action is to administer diazepam plus
Thiamine
A freshman student (weight 70 kg) attends a college party where he rapidly consumes a quantity of an alcoholic beverage that results in a blood level of 500 mg/dL. Assuming that this young man has not had an opportunity to develop tolerance to ethanol, his present condition is best characterized as
(A) Able to walk, but not in a straight line
(B) Alert and competent to drive a car
(C) Comatose and near death
(D) Sedated with increased reaction times
(E) Slightly inebriated
Comatose and near death
A state of unconsciousness, analgesia, and amnesia, with skeletal muscle relaxation and loss of reflexes
General anesthesia
Drugs used as general anesthetics are ___ with actions that can be induced and terminated more rapidly than those of conventional sedative-hypnotics.
CNS depressants
STAGES OF ANESTHESIA
• The patient has decreased awareness of pain
• Sometimes with amnesia
• Consciousness may be impaired but is not lost.
Stage 1: Analgesia
STAGES OF ANESTHESIA • The patient appears to be delirious and excited. • Amnesia occurs • Reflexes are enhanced • Respiration is typically irregular • Retching and incontinence may occur
Stage 2: Disinhibition
STAGES OF ANESTHESIA • The patient is unconscious • Has no pain reflexes • Respiration is very regular • Blood pressure is maintained
Stage 3: Surgical Anesthesia
STAGES OF ANESTHESIA
• The patient develops severe respiratory and cardiovascular depression that requires mechanical and pharmacologic support.
Stage 4: Medullary Depression
Anesthesia protocols commonly include ____ drugs to induce the anesthetic state, ___ anesthetics (with or without intravenous agents) to maintain an anesthetic state, and ____ agents to effect muscle relaxation.
- intravenous
- inhaled
- neuromuscular blocking
As CNS depressants, these drugs usually ____ the threshold for firing of CNS neurons. The potency of inhaled anesthetics is roughly proportional to
their lipid solubility.
increase
Drugs that facilitate γ-aminobutyric acid (GABA)-mediated inhibition at GABAA receptors.
- Inhaled anesthetics,
- barbiturates,
- benzodiazepines,
- etomidate,
- propofol
antagonizes the action of the excitatory neurotransmitter glutamic acid on the N-methyl-Daspartate (NMDA) receptor.
Ketamine
The agents currently used in inhalation anesthesia are ____ (a gas) and several easily vaporized liquid halogenated hydrocarbons, including halothane, desflurane, enflurane, isoflurane, sevoflurane, and methoxyflurane.
nitrous oxide
Anesthesia is terminated by ____ of the drug from the brain to the blood and elimination of the drug through the lungs.
redistribution
Metabolism of these drugs has only a minor influence on the speed of recovery from their anesthetic effect but does play a role in potential toxicity of these anesthetics.
halothane and methoxyflurane
Defined as the alveolar concentration required to eliminate the response to a standardized painful stimulus in 50% of patients. And the potency of inhaled anesthetics is best measured by the
minimum alveolar anesthetic concentration (MAC),
Are myocardial depressants that decrease cardiac output
Enflurane and halothane
causes peripheral vasodilation.
isoflurane, desflurane, and sevoflurane
is less likely to lower blood pressure than are other inhaled anesthetics and has the smallest effect on respiration
Nitrous oxide
may sensitize the myocardium to the arrhythmogenic effects of catecholamines.
Halothane, and isoflurane
is a pulmonary irritant and may cause bronchospasm.
desflurane
The pungency of ___ causing breath-holding limits its use in anesthesia induction.
enflurane
Fluoride released by metabolism of ____ (and possibly both enflurane and sevoflurane) may cause renal insufficiency after prolonged anesthesia.
methoxyflurane
Prolonged exposure to nitrous oxide decreases methionine synthase
activity and may lead to _____.
megaloblastic anemia
Susceptible patients may develop ____ when anesthetics are used together with neuromuscular blockers (especially succinylcholine).
malignant hyperthermia
Is indicated for the treatment of this life-threatening condition, with supportive management.
Dantrolene
Have high lipid solubility, which promotes rapid entry into the brain and results in surgical anesthesia in one circulation time (<1 min). These drugs are used for induction of anesthesia and for short surgical procedures.
Thiopental and methohexital
The anesthetic effects of this drug are terminated by redistribution from the brain to other highly perfused tissues , but hepatic metabolism is required for elimination from the body.
thiopental
Are respiratory and circulatory depressants; because they depress cerebral blood flow, they can also decrease intracranial pressure.
Barbiturates
Is widely used adjunctively with inhaled anesthetics and intravenous opioids. The onset of its CNS effects is slower than that of thiopental, and it has a longer duration of action. Cases of severe postoperative respiratory depression have occurred.
Midazolam
The benzodiazepine receptor antagonist that accelerates recovery from midazolam and other benzodiazepines.
flumazenil
This drug produces a state of “dissociative anesthesia” in which the patient remains conscious but has marked catatonia, analgesia, and amnesia.
• is a chemical congener of the psychotomimetic agent, phencyclidine (PCP).
• The drug is a cardiovascular stimulant, and this action may lead to an increase in intracranial pressure.
• Emergence reactions, including disorientation, excitation, and hallucinations, which occur during recovery from ketamine anesthesia, can be reduced by the preoperative use of benzodiazepines.
Ketamine
Are used with other CNS depressants (nitrous oxide, benzodiazepines) in anesthesia regimens and are especially valuable in high- risk patients who might not survive a full general anesthetic.
Morphine and fentanyl
Respiratory depression with opioids drugs may be reversed postoperatively with
naloxone
Is a state of analgesia and amnesia is produced when fentanyl is used with droperidol and nitrous oxide.
Neuroleptanesthesia
- It produces anesthesia as rapidly as the intravenous barbiturates, and recovery is more rapid.
- It has antiemetic actions, and recovery is not delayed after prolonged infusion.
- The drug is commonly used as a component of balanced anesthesia and as an anesthetic in outpatient surgery.
- It is also effective in producing prolonged
sedation in patients in critical care settings. - may cause marked hypotension during induction of anesthesia, primarily through decreased peripheral resistance.
- Total body clearance of propofol is greater than hepatic blood flow, suggesting that its elimination includes other mechanisms in addition to metabolism by liver enzymes.
Propofol
A water-soluble prodrug form, is broken down in the body by alkaline phosphatase to form propofol. However, onset and recovery are both slower than with propofol. While it appears to cause less pain at injection sites than the standard form of the drug, many patients experience paresthesias.
Fospropofol
- This imidazole derivative affords rapid induction with minimal change in cardiac function or respiratory rate and has a short duration of action.
- The drug is not analgesic, and its primary advantage is in anesthesia for patients with limited cardiac or respiratory reserve.
- Etomidate may cause pain and myoclonus on injection and nausea postoperatively.
- Prolonged administration may cause adrenal suppression.
Etomidate
- This centrally acting α2-adrenergic agonist has analgesic and hypnotic actions when used intravenously.
- It is used mainly for short-term sedation in an ICU setting.
- When used in general anesthesia, the drug decreases dose requirements for both inhaled and intravenous anesthetics.
Dexmedetomidine
A 23-year-old man has a pheochromocytoma, blood pressure of 190/120 mm Hg, and hematocrit of 50%. Pulmonary function and renal function are normal. His catecholamines are elevated, and he has a well-defined abdominal tumor on MRI. He has been scheduled for surgery. Which agents should be avoided in the anesthesia protocol?
Isoflurane (& halothane)
Which statement concerning nitrous oxide is accurate?
(A) A useful component of anesthesia protocols because it lacks cardiovascular depression
(B) Anemia is a common adverse effect in patients exposed to nitrous oxide for periods longer than 2 h
(C) It is the most potent of the inhaled anesthetics
(D) There is a direct association between the use of nitrous oxide and malignant hyperthermia
(E) Up to 50% of nitrous oxide is eliminated via hepatic metabolism
A useful component of anesthesia protocols because it lacks cardiovascular depression
Which statement concerning nitrous oxide is accurate?
(A) A useful component of anesthesia protocols because it lacks cardiovascular depression
(B) Anemia is a common adverse effect in patients exposed to nitrous oxide for periods longer than 2 h
(C) It is the most potent of the inhaled anesthetics
(D) There is a direct association between the use of nitrous oxide and malignant hyperthermia
(E) Up to 50% of nitrous oxide is eliminated via hepatic metabolism
A useful component of anesthesia protocols because it lacks cardiovascular depression
Total intravenous anesthesia with fentanyl has been selected for a frail elderly woman
about to undergo cardiac surgery. Which statement about this anesthesia protocol is
accurate?
(A) Intravenous fentanyl will provide useful cardiostimulatory effects
(B) Marked relaxation of skeletal muscles is anticipated
(C) Opioids such as fentanyl control the hypertensive response to surgical stimulation
(D) Patient awareness may occur during surgery, with recall after recovery
(E) The patient is likely to experience pain during surgery
Patient awareness may occur during surgery, with recall after recovery
is the condition that results when sensory transmission from a local area of the body to the CNS is blocked. They block the sodium channels of excitable membranes.
Local anesthesia
Is an important exception of local anethetics because it has intrinsic sympathomimetic action due to its inhibition of norepinephrine reuptake into nerve terminals.
Cocaine
Are the longest-acting amide local anesthetics with half-lives of 3.5 and 4.2 h, respectively.
Bupivacaine and ropivacaine
High concentrations of extracellular K+ may ____ local anesthetic activity, whereas elevated extracellular Ca2+ may ___ it.
enhance; antagonize
The local anesthetics are commonly used for minor surgical procedures
often in combination with vasoconstrictors such as
epinephrine
A racemic mixture of two isomers may produce severe cardiovascular
toxicity, including arrhythmias and hypotension.
Bupivacaine
The (S)isomer, ____, is less cardiotoxic.
levobupivicaine
Cardiotoxicity has also been reported for ____ when used for peripheral nerve block.
ropivicaine
Characteristic properties of local anesthetics include all of the following EXCEPT
(A) An increase in membrane refractory period
(B) Blockade of voltage-dependent sodium channels
(C) Effects on vascular tone
(D) Preferential binding to resting channels
(E) Slowing of axonal impulse conduction
Preferential binding to resting channels
Which statement about the speed of onset of nerve blockade with local anesthetics is
correct?
(A) Faster in hypocalcemia (B) Faster in myelinated fibers (C) Faster in tissues that are infected (D) Slower in hyperkalemia (E) Slower in the periphery of a nerve bundle than in the center of a bundle
Faster in myelinated fibers
Which statement about the toxicity of local anesthetics is correct?
(A) Cyanosis may occur after injection of large doses of lidocaine,especially in patients with pulmonary disease
(B) In overdosage, hyperventilation (with oxygen) is helpfulto correct acidosis and lower extracellular potassium
(C) Intravenous injection of local anesthetics may stimulateectopic cardiac pacemaker activity
(D) Most local anesthetics cause vasoconstriction
(E) Serious cardiovascular reactions are more likely to occur with tetracaine than with bupivacaine
In overdosage, hyperventilation (with oxygen) is helpfulto correct acidosis and lower extracellular potassium
A vasoconstrictor added to a solution of lidocaine for a peripheral nerve block will
(A) Decrease the risk of a seizure
(B) Increase the duration of anesthetic action of the local anesthetic
(C) Both A and B
(D) Neither A nor B
A & C
