Drugs- Anesthetics (kinder) Flashcards
21 year old male is schedule to undergo a laparoscopic hernia repair on an outpatient basis under general anesthesia. this is the first time he has undergone surgery and he is highly anxious in the preoperative area. which benzodiazepine may be utilized in this situation to reduce his anxiety ?
Benzocaine Fentanyl Midazolam Propofol Thiopental
Benzocaine- local anesthetic Fentanyl- opioid Midazolam- benzodiazepine and the answer Propofol- IV anesthetic Thiopental - barbituate
a 19 yo femal admitted to the ambulatroy surgery center for strabism surgery to correct misalignment of her extraocular muscles. she is other wise healthy and all labs are WNL. which IV induction agent may be used that is rapid in onset and recovery and has antiemetic actions
halothane Nitrous oxide procaine propofol sevoflurane
propofol
has anti-emetic affects too
the chemical with which blood:gas partition coefficient will reach the highest concentration in the brain the fast (assume brain:blood partition coefficients are equal)
- 42
- 47
- 69
- 4
- 8
0.42 - lower the number the faster the anesthesia b/c lower affinity for blood space
- 42- desflurane
- 47- nitrous oxide
- 69- sevoflurane
- 4- isoflurane
- 8 - enflurane
the anesthesiologist prepares to adminster several drugs to a patient as part of a normal perioperative care. which drug lacks the ability to cause generalized CNS depression, lacks the ability to reduce or impair the pt’s level of consciousness, or lacks the ability to prevent or reduce pain
Midazolam
Pancuronium
Propofol
Thiopental
pancuronium - neuromuscular blocking agent
Nitrous oxide is a common component in the technique of balanced anesthesia. it is used in conjunction with a volatile anesthetic. which phrase best summarizes why nitrous oxide cannot be used alone for general anesthesia
Almost total lack of analgesic activity, regardless of concentration
inspired concentrations greater than 10% or so tend to have profound cardiac negative inotropic effects
MAC (minimum alveolar conc) is greater than 100%
such great solubility in blood that its effects take an extraordinary long time to develop
very high frequency of bronchospasm
MAC (minimum alveolar conc) is greater than 100%
even if we gave 100% NO the mac will still be less than 1 MAC
so need to use with another anesthetic
(1) Desflurane
(2) Enflurane
(3) Halothane
(4) Isoflurane
(5) Sevoflurane
volatile inhaled anesthetics
i) Low vapor pressures, high boiling points, liquids at room temperature (20˚C).
nitrous oxide
gaseous inhaled anesthetic
i) High vapor pressure, low boiling point, gas at room temperature.
Name 7 IV anesthetics
i) Propofol (Diprivan)
ii) Fospropofol
iii) Barbiturates
(1) Thiopental and methohexital
iv) Benzodiazepines
(1) Midazolam (Versed), lorazepam (Ativan), diazepam (Valium)
v) Etomidate
vi) Ketamine
vii) Dexmedetomidine (Precedex)
i) Benzocaine
ii) Cocaine
iii) Procaine (Novocain)
iv) Tetracaine
ester
local anesthetics
i) Articaine
ii) Bupivacaine
iii) Lidocaine (Xylocaine)
iv) Mepivacaine (Marcaine)
v) Ropivacaine
amides
local anesthetics
what are 5 primary effects produced by general anesthesia
unconsciousness
amnesia
analgesia
inhibition of autonomic reflexes
skeletal muscle relaxation
b) None of currently available general anesthetics, when used alone, produce all five desired effects.
what are the mechanisms of general anesthesia
Anesthetic drugs may (A) enhance inhibitory synaptic activity or (B) diminish excitatory activity.
blood: gas ratio of nitrous oxide
MAC?
0.47
> 100 = MAC
(ii) Agents with low blood solubility (nitrous oxide, desflurane) reach high arterial pressure rapidly, which in turn results in rapid equilibrium with the brain and fast onset of action.
blood:gas ratio of desflurane
MAC?
0.42
MAC- 6-7
(ii) Agents with low blood solubility (nitrous oxide, desflurane) reach high arterial pressure rapidly, which in turn results in rapid equilibrium with the brain and fast onset of action.
blood:gas ratio of sevoflurane
MAC?
0.69
MAC 2
blood:gas ratio of isoflurane
MAC?
1.4
MAC- <2
blood:gas ratio of enflurane
MAC?
1.8
MAC 8
blood:gas ratio of halothane
MAC
2.3
MAC >40
(iii) Agents with high blood solubility (halothane) reach high arterial pressure slowly, which in turn results in slow equilibration with the brain and a slow onset of action.
what is the driving force for uptake of inhaled anesthetic
alveolar concentration
(2) The two factors that determine how quickly the alveolar concentration changes (can be controlled by anesthesiologist) are what two things?
(1) inspired concentration or partial pressure and (2) alveolar ventilation.
(3) Increases in either the inspired partial pressure or in ventilation will increase the rate of rise in the alveoli and will accelerate induction.
(4) Partial pressure in ¬¬the alveoli is expressed as a ratio of alveolar concentration (FA) over inspired concentration (FI); the faster FA/FI approaches 1 (representing inspired-to-alveolar equilibrium), the faster anesthesia will occur during an inhaled induction.
what is the blood:gas partition coefficient and how is it used clinically
useful index of solubility and defines the relative affinity of an anesthetic for blood compared to inspired gas.
(i) There is an inverse relationship between the blood:gas partition coefficient value and rate of anesthesia onset.
(ii) Agents with low blood solubility (nitrous oxide, desflurane) reach high arterial pressure rapidly, which in turn results in rapid equilibrium with the brain and fast onset of action.
(iii) Agents with high blood solubility (halothane) reach high arterial pressure slowly, which in turn results in slow equilibration with the brain and a slow onset of action.
if an agent is not very soluble, how will this relate to how fast its onset is
if the agent is not very soluble, it will have a faster onset of action
In this schematic diagram, solubility in blood is represented by the relative size of the blood compartment (the more soluble, the larger the compartment). Relative partial pressures of the agents in the compartments are indicated by the degree of filling of each compartment. For a given concentration or partial pressure of the two anesthetic gases in the inspired air, it will take much longer for the blood partial pressure of the more soluble gas (halothane) to rise to the same partial pressure as in the alveoli. Since the concentration of the anesthetic agent in the brain can rise no faster than the concentration in the blood, the onset of anesthesia will be slower with halothane than with nitrous oxide.
what is the effect of increased cardiac output on rate of induction of anesthesia
(a) Increased pulmonary blood flow (increased cardiac output), increases uptake of anesthetic, thereby decreasing rate by which FA/ FI rises, which will decrease the rate of induction of anesthesia.
(b) An increase in cardiac output and pulmonary blood flow will increase uptake of anesthetic into the blood, but the anesthetic taken up will be distributed in all tissues, not just the CNS; increased cardiac output will increase delivery of anesthetic to other tissues and not the brain (cerebral blood flow well regulated).
what are 2 parameters that can be manipulated by anesthesiologists for controlling speed of induction and recovery
1) concentration of anesthetic in inspired air, 2) alveolar ventilation
(a) Concentration in inspired air cannot be < 0, hyperventilation only way to speed recovery.
(1) Recovery from inhaled anesthetics follows some of the same principles in reverse that are important during induction.
(2) Inhaled anesthetics that are relatively insoluble in the blood and brain are eliminated at faster rates than more soluble anesthetics.
(5) Duration of exposure may have a significant impact on recovery.
(a) Accumulation in muscle, skin, and fat increases with prolonged exposure (especially in obese) and blood tension may decline slowly during recovery as anesthetics are slowly eliminated from these tissues.
in decreasing order, what are the inhaled anesthetics that are hepatically metabolized (recovery)
– halothane > enflurane > sevoflurane
what is currently used to describe anesthetic potency
described by minimum alveolar concentration (MAC) required to prevent response to surgical incision.
- 0 MAC is the partial pressure of inhaled anesthetic in alveoli at which 50% of population remained immobile at time of skin incision.
(ii) Patients may need 0.5-2 MAC for successful anesthesia (> 90% of patients will become anesthetized at 1.3 MAC). - MAC is additive: 0.5 MAC of an agent added to 0.5 MAC of another = 1 MAC.
what does a MAC value greater than 100% indicate
(iii) MAC values greater than 100% indicate that even if 100% of the inspired air at barometric pressure is the anesthetic, the MAC value would still be less than 1 and other agents must be supplemented to achieve full surgical anesthesia (e.g., nitrous oxide).
stage 1 - Analgesia
(i) Stage I Analgesia
1. Patient initially experiences analgesia without amnesia; later in Stage I, both analgesia and amnesia produced.
Stage 2 excitement
(ii) Stage II Excitement
1. Patient appears delirious, may vocalize but is completely amnesiac; respirations rapid, heart rate and blood pressure increase.
stage III surgical anesthesia
- Begin with slowing respiratory rate and heart rate; extends to complete cessation of spontaneous respiration (apnea).
- Four planes described based on changes of ocular movements, eye reflexes, and pupil sizes indicating increasing depth of anesthesia
however, a reliable indication that stage III has been achieved is loss of responsiveness to painful stimuli (e.g., trapezius muscle squeeze) and the reestablishment of regular breathing.
stage IV medullary depression
- Severe CNS depression, including vasomotor center in medulla & respiratory center in brainstem. Without circulatory or respiratory support, death would rapidly ensue.
what are the vascular effects of inhaled anesthetics on the brain and in what pt’s is this clinically significant
(c) Inhaled anesthetics decrease the metabolic activity of the brain which generally results in reduction of blood flow; however, volatile anesthetics may also cause cerebral vasodilation (undesirable in patients with increased intracranial pressure).
what are the cardiovascular effects of inhaled anesthetics
all depress normal cardiac contractility (halothane and enflurane more so than others)
(b) Tend to decrease mean arterial pressure in direct proportion to alveolar concentration.
(c) A decrease in arterial blood pressure leads to activation of autonomic nervous system reflexes which may trigger an increase in HR (significant with desflurane and isoflurane, others attenuate baroreceptor response).
