Anesthesia Flashcards
(150 cards)
1
Q
Define anesthesia.
A
A reversible state of CNS depression where the patient is in an amnestic state resulting in the loss of response to external stimuli and pain.
2
Q
What are the five benefits of anesthesia?
A
- Sedation and reduction of anxiety.
- Lack of awareness and amnesia.
- Skeletal muscle relaxation.
- Suppression of undesirable reflexes.
- Analgesia.
None of the currently available anesthetic agents when used alone can achieve all of these desired effects well.
3
Q
What are the factors that we should consider when selecting anesthetic agents?
A
- Status of the patient’s organ systems.
- Concomitant use of drugs.
4
Q
What are the considerations for the cardiovascular system in the selection of anesthetic agents?
A
Anesthetic agents can suppress cardiovascular function to varying degrees, necessitating treatment with vasoactive substances.
This is especially important in patients with coronary artery disease (CAD), heart failure (HF), dysrhythmias, valvular disease, and other cardiovascular diseases (CVD).
5
Q
How do inhaled anesthetics affect the respiratory system?
A
Inhaled anesthetics depress the respiratory system by reducing the ventilatory response to increased levels of CO2 in the blood.
They also act as bronchodilators and are classified based on whether they are pungent (airway irritants) or non-pungent anesthetics.
6
Q
What is the impact of anesthetics on the liver and kidneys?
A
Some anesthetics are hepatotoxic and nephrotoxic, with the release of fluoride, bromide, and other metabolites of halogenated hydrocarbons potentially affecting these organs.
7
Q
Which patients should be cautious with anesthesia due to nervous system concerns?
A
Patients with epilepsy, myasthenia gravis, neuromuscular disease, and compromised cerebral circulation should avoid anesthesia or require careful selection of the anesthetic agent.
8
Q
What are the risks of administering anesthesia during pregnancy?
A
Certain anesthetics can harm the pregnant individual and the fetus.
For example, nitrous oxide may cause aplastic anemia, and benzodiazepines have been associated with oral clefts and floppy baby syndrome (temporary hypotonia).
9
Q
What is the role of muscle relaxants in anesthesia?
A
Muscle relaxants, such as NMJ blockers and curares, are used to facilitate intubation during anesthesia.
10
Q
How do H2 blockers contribute to the anesthetic process?
A
H2 blockers like famotidine and ranitidine are used to reduce gastric acidity, which is important during anesthesia.
11
Q
What is the purpose of benzodiazepines (BZs) in anesthesia?
A
Benzodiazepines, such as midazolam and diazepam, are used for their anxiolytic effects and to facilitate amnesia.
12
Q
How do barbiturates assist in anesthesia?
A
Barbiturates aid in sedation and facilitate smooth induction of anesthesia. When administered concurrently, they also lower the dose of anesthetic required to maintain the desired level of surgical anesthesia.
13
Q
What is the role of non-opioids and opioids in anesthesia?
A
Non-opioids like acetaminophen and celecoxib or opioids like fentanyl, are administered for their analgesic properties.
14
Q
Why are antihistamines used in the context of anesthesia?
A
Antihistamines are used to prevent allergic reactions during the administration of anesthesia.
15
Q
How does a serotonin antagonist like ondansetron serve in anesthesia?
A
Ondansetron is a serotonin antagonist used to prevent postoperative nausea and vomiting.
16
Q
What is the role of anticholinergic drugs in anesthesia?
A
Anticholinergic drugs, such as glycopyrrolate, are used to prevent bradycardia and the secretion of fluids into the respiratory tract during anesthesia.
17
Q
What is a potential downside of coadministering multiple drugs with anesthesia?
A
Coadministration can enhance undesirable anesthetic effects such as hypoventilation.
18
Q
What is the induction stage of anesthesia?
A
Induction is the period from the onset of administration of the potent anesthetic until the development of effective surgical anesthesia.
19
Q
What is the induction stage of anesthesia?
A
Induction is the period from the onset of administration of the potent anesthetic until the development of effective surgical anesthesia.
20
Q
What is the purpose of the maintenance stage in anesthesia?
A
Maintenance is the phase that provides sustained surgical anesthesia during the procedure.
21
Q
What happens during the recovery stage of anesthesia?
A
Recovery is the period after the discontinuation of anesthesia until consciousness and protective physiologic reflexes are regained.
22
Q
How is anesthesia induction usually initiated in adults, and what is its onset time?
A
Anesthesia induction is normally initiated with an IV anesthetic like propofol, which produces unconsciousness within 30-40 seconds after injection.
23
Q
Why are IV anesthetics often used for induction?
A
IV anesthetics are preferred for their rapid onset and the ability to control the depth of anesthesia quickly.
24
Q
How is anesthesia induction performed in children without IV access?
A
Inhalation induction is used with non-pungent agents such as halothane or sevoflurane to induce general anesthesia in children without IV access.
25
How is anesthesia commonly maintained, and why?
Anesthesia is commonly maintained with the administration of volatile anesthetics, which offer good control over the depth of anesthesia.
26
Why are IV anesthetics used during induction not typically used for maintaining anesthesia?
IV anesthetics used during induction usually have a short duration of action and cannot maintain the anesthetic activity for a long time.
27
What underlines the recovery process from anesthesia?
Redistribution from the site of action, rather than metabolism of the anesthetic, plays a major role in the recovery process.
28
What characterizes Stage I of anesthesia?
Stage I is known as the analgesia stage, where pain sensation is diminished.
29
What is stage II of anesthesia, and how can it be managed?
Stage II is known as the excitement stage. To shorten this stage, a rapid-acting agent like propofol is given intravenously before inhalation anesthesia is administered.
30
What is crucial about managing stage III of anesthesia?
Stage III is known as surgical anesthesia. Continuous careful monitoring is required to prevent progression to stage IV.
31
What is stage IV in anesthesia and why is it critical to avoid?
Stage IV is characterized by medullary paralysis, severe depression of the respiratory and vasocenters, which can lead to coma and death, hence it must be avoided.
32
What factors determine the rate of transfer of anesthetic agent from alveoli to arterial blood and from arterial blood to the brain?
The rate of anesthesia is positively affected by the anesthetic concentration in inspired air and negatively affected by the anesthetic solubility in blood. Pulmonary blood flow has a complex effect; it has a negative impact on the induction speed for soluble agents due to uptake by the blood, but positive for insoluble agents. Pulmonary ventilation positively influences the rate of anesthesia.
33
How does the concentration of anesthetic in the inspired air affect the induction of anesthesia?
Increasing the concentration of anesthetic in the inspired air leads to a higher alveolar anesthetic concentration, which increases the rate of transfer into the blood, and consequently, speeds up the rate of induction of anesthesia.
34
What is the blood:gas solubility coefficient and how does it affect anesthesia induction and recovery?
The blood:gas solubility coefficient defines the relative affinity of an anesthetic for blood compared to air. Agents with low blood solubility have a low blood:gas solubility coefficient, leading to rapid alveolar concentration increase, quick equilibration with the blood and brain, rapid induction, and recovery. Agents with higher solubility have slower induction and recovery.
35
How is solubility in blood ranked according to the blood:gas solubility coefficient for common anesthetics?
The ranking from highest to lowest solubility coefficient is:
halothane > enflurane > isoflurane > sevoflurane > desflurane > nitrous oxide.
36
How does an increase in cardiac output affect the induction of anesthesia in terms of pulmonary blood flow?
An increase in cardiac output leads to increase pulmonary blood flow, which removes more anesthetic agent from the alveoli. This reduces the rate of increase in arterial tension of the anesthetic, thereby slowing down the induction process.
37
How do changes in minute ventilation affect the induction of anesthesia with insoluble and soluble agents?
For insoluble agents in the blood, changes in minute ventilation have little influence on induction since the alveolar concentration is always high. However, for soluble agents, increased minute ventilation significantly raises alveolar tension, thereby affecting induction.
38
What is the primary use of inhalation anesthetics?
Inhalation anesthetics are mainly used for the maintenance of anesthesia after induction with an IV agent.
39
What types of inhalation agents are commonly used?
Common inhalation agents include gas anesthetics like nitrous oxide, and liquid volatile anesthetics such as halothane, sevoflurane, desflurane, and isoflurane.
40
How can the depth of anesthesia be adjusted during maintenance?
The depth of anesthesia can be rapidly altered by changing the inhaled concentration of the drug. Increasing anesthetic concentration increases the transfer of the drug to the blood.
41
What should be considered due to the therapeutic index of inhalation anesthetics?
Inhalation anesthetics have a very narrow therapeutic index, generally from 2 to 4, which means they should be monitored carefully.
42
Are there antagonists for inhalation anesthetics?
No antagonists exist for inhalation anesthetics.
43
What are the general safety features of inhalation anesthetics?
Inhalation anesthetics are generally nonflammable and nonexplosive, with the exception of ether.
44
How do inhalation anesthetics affect cerebrovascular resistance?
Inhalation anesthetics decrease cerebrovascular resistance, which leads to increased perfusion of the brain.
45
What effect do inhalation anesthetics have on bronchial smooth muscle and how is this beneficial?
Inhalation anesthetics can cause bronchodilation, which can be particularly useful for patients with wheezing and status epilepticus.
46
How is the potency of inhaled anesthetics defined?
The potency of inhaled anesthetics is defined as the minimum alveolar concentration (MAC).
47
How is MAC expressed, and what does it indicate?
MAC is usually expressed as the percentage of gas in a mixture required to achieve anesthetic immobility. It indicates the concentration needed to prevent movement in response to surgical incision in 50% of subjects.
48
What is the relationship between MAC and the potency of anesthetics?
A smaller MAC value indicates a more potent anesthetic (such as sevoflurane, isoflurane, and halothane), while a larger MAC indicates a less potent agent (such as nitrous oxide).
49
How does lipid solubility affect the potency of an anesthetic?
The more lipid-soluble an anesthetic is, the higher the fat:gas partition coefficient and the lower the MAC value, which corresponds to higher potency.
50
What factors can increase MAC, making the patient less sensitive to anesthetics?
Factors that increase MAC include hyperthermia and increased CNS catecholamines (due to drugs like ephedrine and amphetamine). Chronic ethanol abuse can also increase MAC.
51
What factors can decrease MAC, making the patient more sensitive to anesthetics?
Factors that decrease MAC include increased age, hypothermia, pregnancy, sepsis, acute ethanol intoxication, concurrent administration of IV anesthetics, and α-2 adrenergic receptor agonists like clonidine and dexmedetomidine.
52
What is the primary effect of intravenous anesthetics on the induction of anesthesia?
Intravenous anesthetics cause the rapid induction of anesthesia.
53
Is there a specific receptor identified for the action of general anesthetics?
No specific receptor has been identified as the locus of general anesthetic action.
54
What are the main targets for inhalation anesthetic action?
The main targets for inhalation anesthetics are 1) increasing the sensitivity of GABA receptors to GABA, 2) increasing the activity of glycine receptors in the spinal motor neurons, and 3) blocking the excitatory postsynaptic currents of the nicotinic and glutamate receptors.
55
What are the key characteristics of Halothane as an anesthetic?
Halothane is a prototype anesthetic that is non-explosive and allows for rapid induction and quick recovery compared to previous anesthetics, despite having a high blood:gas partition coefficient which generally leads to slower induction and recovery than the newest anesthetics.
56
What are the therapeutic uses of Halothane?
Halothane is used as a potent anesthetic often coadministered with nitrous oxide, opioids, or local anesthetics due to its relatively weak analgesic properties. It causes uterine and skeletal muscle relaxation (useful in obstetric when uterine relaxation is indicated) and is a bronchodilator and non-pungent, making it suitable for patients with airway problems.
57
Why is Halothane considered suitable for children?
Halothane is considered suitable for children due to its low hepatotoxicity in the pediatric population and its pleasant odor which makes administration easier.
58
What are the pharmacokinetics and potential hepatotoxic effects of Halothane?
Halothane is metabolized to tissue-toxic hydrocarbons like trifluoroethanol and bromide ions, which can cause hepatic necrosis. Symptoms of this include anorexia, nausea, vomiting, and possible signs of hepatitis. Therefore, Halothane anesthesia should not be repeated at intervals of less than 2-3 weeks to avoid such effects.
59
What are the cardiac effects associated with Halothane use?
Halothane can cause myocardial depression, leading to reduced cardiac output and hypotension. It also has vagomimetic effects that can cause atropine-sensitive bradycardia and may sensitize the heart to arrhythmias.
60
What is malignant hyperthermia and how is it related to Halothane?
Malignant hyperthermia is a life-threatening condition characterized by severe muscle contraction, increased skeletal muscle oxidative metabolism, and an overwhelming increase in body temperature, which can lead to death if not treated immediately. It can be triggered by Halothane.
61
How does Halothane compare to similar anesthetics in terms of renal or hepatic damage?
Halothane is more likely to induce renal or hepatic damage than similar general anesthetics. However, changes in renal function induced by Halothane are fully reversible.
62
What are the induction and recovery characteristics of Isoflurane?
Isoflurane allows for rapid induction and recovery due to its low blood solubility.
63
Why does Isoflurane have a low MAC value and why is it not used for inhalation induction?
Isoflurane has a low MAC value due to its high lipid solubility, making it a potent anesthetic. It's not typically used for inhalation induction because it can cause a severe cough reflex and has a pungent smell.
64
How does Isoflurane affect the cardiovascular system?
Isoflurane has a good cardiovascular profile as it does not induce cardiac arrhythmias, preserves cardiac output, does not sensitize the heart to catecholamines (making it a better choice for patients with CVD), dilates coronary arteries, and can be beneficial for patients with ischemic heart disease. However, it does produce dose-dependent hypotension due to peripheral vasodilation.
65
What adverse effect is associated with the metabolism of Isoflurane?
Isoflurane produces halogenated metabolites which can lead to hepatotoxicity.
66
What are the onset and recovery times like for Desflurane, and how does this relate to its use in surgeries?
Desflurane has a very rapid onset and recovery due to its low blood solubility, making it the volatile anesthetic with the lowest solubility and a popular choice for outpatient surgery.
67
Why is Desflurane not used for inhalation inductions?
Desflurane is pungent and can irritate the airway, potentially causing laryngospasm, coughing, and excessive secretions, similar to Isoflurane. Therefore, it is not used for inhalation inductions.
68
How does Desflurane affect vasodilation and cardiac output?
Desflurane produces greater vasodilation with minimal effect on cardiac output, making it a better choice for patients with cardiovascular diseases (CVDs).
69
What is required for the administration of Desflurane due to its physical properties?
Due to its high volatility, Desflurane must be delivered using a special vaporizer.
70
How is Desflurane metabolized and what does this mean for tissue toxicity?
Desflurane undergoes minimal degradation as it is eliminated unchanged through the lungs, which means tissue toxicity is rare.
71
What characterizes the induction process with Sevoflurane?
Sevoflurane allows for rapid induction due to its rapid onset and recovery, attributed to its low blood solubility.
72
Why is Sevoflurane often chosen for inhalation induction in pediatric patients?
Sevoflurane has low pungency and does not cause airway irritation, making it suitable for inhalation induction in pediatric patients and often the first choice for this purpose.
73
What makes Sevoflurane a preferred anesthetic in cardiac surgery?
Sevoflurane is preferable for cardiac surgery because it produces greater vasodilation with minimal effect on cardiac output, making it a good option for patients with cardiovascular diseases (CVDs).
74
What is the metabolic fate of Sevoflurane and its implication for nephrotoxicity?
Sevoflurane is metabolized by the liver into two metabolites, including fluoride, resulting in minimal nephrotoxicity.
75
What is the common name for Nitrous Oxide and how is it characterized as an analgesic?
Nitrous Oxide is commonly known as laughing gas and is characterized as a potent analgesic.
76
Why is Nitrous Oxide usually combined with another anesthetic?
Although Nitrous Oxide is a potent analgesic, it is a weak anesthetic, so it is typically combined with another anesthetic to produce pain-free anesthesia.
77
What are the respiratory and muscular effects of Nitrous Oxide?
Nitrous Oxide is non-irritating (non-pungent), does not depress respiration (acts as a bronchodilator), and does not produce muscle relaxation.
78
What is the solubility of Nitrous Oxide in blood and how does it affect induction and recovery?
Nitrous Oxide is poorly soluble in blood, allowing for very rapid induction and recovery times.
79
What is diffusion hypoxia and how is it prevented when using Nitrous Oxide?
Diffusion hypoxia occurs because Nitrous Oxide diffuses rapidly from blood back to alveoli, diluting oxygen. To prevent this, Nitrous Oxide must be combined with at least 20% oxygen.
80
How does Nitrous Oxide affect the cardiovascular system and cerebral blood flow?
Nitrous Oxide has moderate to no effect on the cardiovascular system and does not significantly increase cerebral blood flow.
81
What is the hepatotoxic potential of Nitrous Oxide compared to other inhalation anesthetics?
Nitrous Oxide is the least hepatotoxic of the inhalation anesthetics as it is eliminated unchanged by the lungs.
82
Why is Nitrous Oxide contraindicated in pregnancy?
Nitrous Oxide is contraindicated in pregnancy due to the risk of causing hematologic complications, including aplastic anemia.
83
What is the primary effect of intravenous anesthetics on the induction of anesthesia?
Intravenous anesthetics cause the rapid induction of anesthesia.
84
What is the preferred method of anesthesia induction in most settings?
The preferred method of anesthesia induction in most settings is intravenous, except for pediatric anesthesia where inhalation is commonly used.
85
How can IV anesthetics be administered during longer procedures?
IV anesthetics may be administered as infusions to help maintain anesthesia during longer procedures.
86
What is a secondary use of IV anesthetics at lower doses?
At lower doses, IV anesthetics may be used to provide sedation.
87
What is the analgesic potency of Thiopental and Methohexital?
Thiopental and Methohexital are potent anesthetics but weak analgesics.
88
Why do Thiopental and Methohexital enter the CNS quickly?
Their high lipid solubility allows them to quickly enter the CNS and depress function.
89
What has replaced Thiopental and Methohexital as induction agents and why?
Propofol has largely replaced Thiopental and Methohexital as induction agents due to its fast onset of action.
90
What duration of action do Thiopental and Methohexital have?
They are ultrashort-acting barbiturates.
91
What respiratory side effects may Thiopental and Methohexital cause?
Thiopental and Methohexital might cause laryngospasm and bronchospasm if used for anesthesia, making them contraindicated in asthma.
92
What cardiovascular effect can Thiopental and Methohexital have?
They may produce hypotension.
93
What is the role of Propofol in anesthesia?
Propofol is an IV sedative/hypnotic used in the induction or maintenance of anesthesia.
94
How fast is the onset of anesthesia with Propofol?
The induction of anesthesia with Propofol is very rapid, typically occurring within 30-40 seconds.
95
Why is recovery from Propofol anesthesia typically rapid?
Plasma levels of Propofol decline rapidly, allowing for a quick recovery due to the redistribution of the drug.
96
What occasional side effects can Propofol have on the CNS?
While Propofol facilitates CNS depression, it can occasionally cause excitatory phenomena such as muscle twitching, spontaneous movement, and hiccups.
97
What effects does Propofol have on blood pressure and intracranial pressure?
Propofol decreases blood pressure and reduces intracranial pressure due to systemic vasodilation.
98
Why can Propofol lead to respiratory depression?
Propofol leads to respiratory depression primarily due to its inhibitory effects on the central nervous system, which can dampen the respiratory drive.
99
In what context is Propofol commonly used at lower doses?
Propofol is commonly infused in lower doses to provide sedation for outpatient procedures.
100
Why is the incidence of postoperative nausea and vomiting low with Propofol?
The low incidence of postoperative nausea and vomiting with Propofol may be related to its antiemetic properties and the fact that it is less likely to stimulate the chemoreceptor trigger zone.
101
What feeling does Propofol produce in patients?
Propofol produces a feeling of euphoria in some patients.
102
How does the CNS depressant effect of Propofol compare to other anesthetics?
Propofol is considered a less potent CNS depressant compared to other anesthetics.
103
Which intravenous anesthetic has Propofol replaced as a first-choice induction agent?
Propofol has replaced thiopental as the first choice for anesthesia induction.
104
Why is Propofol typically prepared in a viscous or milky emulsion formulation?
Propofol is poorly soluble in water, which leads to its preparation in a viscous formulation that can cause pain at the IV injection site, or in a milky emulsion formulation that has an increased chance of bacterial contamination.
105
What is the solution to the problems associated with Propofol's formulations?
The preparation of Fospropofol, a water-soluble prodrug of Propofol, presents less problems than lipid-formulated Propofol.
106
How is Fospropofol related to Propofol in terms of pharmacological effects?
Fospropofol is metabolized into Propofol in the body, and the pharmacological effects of Fospropofol are attributed to Propofol.
107
What is the primary effect of Etomidate and does it have any analgesic activity?
Etomidate is an IV anesthetic with hypnotic effects and lacks analgesic activity.
108
What are the benefits of using Etomidate for anesthesia?
The benefits of Etomidate include rapid induction and recovery, and little to no effect on the heart and circulation, making it useful for patients with coronary artery disease or cardiovascular dysfunction.
109
What are the common adverse effects of Etomidate?
Etomidate can cause pain, nausea, vomiting, and excitatory phenomena such as involuntary movements.
110
Why can Etomidate cause a decrease in plasma cortisol and aldosterone levels, and how does this affect its usage?
Etomidate inhibits the enzyme 11-β-hydroxylase, leading to decreased cortisol and aldosterone levels. Because of this, Etomidate is not recommended for long-term use, such as continuous infusion, since it can increase mortality.
111
What type of anesthetic is Ketamine and what analgesic property does it have?
Ketamine is a short-acting, non-barbiturate anesthetic with good analgesic properties.
112
What is the dissociated state induced by Ketamine characterized by?
Ketamine induces a dissociated state where the patient remains conscious, may appear to be awake, but does not feel pain.
113
How does Ketamine interact with CNS receptors and affect respiratory function?
Ketamine interacts with the N-methyl-D-aspartate (NMDA) glutamate receptor. It is an inhibitory neurotransmitter but also activates the respiratory centers and causes bronchodilation.
114
What effects does Ketamine have on the cardiovascular system?
Ketamine stimulates the central sympathetic outflow, which causes an increase in blood pressure and cardiac output. It's beneficial for patients with hypovolemic or cardiogenic shock, asthma, or when cardiac depression is undesirable, but it should not be used alone in heart failure patients.
115
How is Ketamine metabolized, and what should be considered in patients with liver impairment?
Ketamine is metabolized in the liver, but small amounts can be excreted unchanged. The dose of Ketamine should be reduced in patients with liver impairment.
116
Why is Ketamine not preferred in certain patients due to its effect on cerebral blood flow?
Ketamine increases cerebral blood flow, which is why it is not preferred in patients with increased intracranial pressure or those at risk for cerebral hemorrhage.
117
What are the potential psychological disadvantages of using Ketamine?
Ketamine can induce postoperative hallucinations, often referred to as "nightmares," particularly in adults. It also has a potential for abuse.
118
Why are Benzodiazepines used in conjunction with anesthetics?
Benzodiazepines are used with anesthetics to sedate the patient, providing anxiolysis and amnesia, which can make the overall anesthesia process smoother and less stressful.
119
Which Benzodiazepine is most commonly used for anesthesia and why?
Midazolam is the most commonly used Benzodiazepine for anesthesia due to its rapid onset and short duration, making it suitable as a preoperative medication and for brief therapeutic procedures.
120
What are the alternatives to Midazolam and their onset/duration characteristics?
Diazepam and Lorazepam are alternatives to Midazolam, with slower onsets and longer durations of action.
121
How do Benzodiazepines affect memory and anxiety during anesthesia?
All three Benzodiazepines mentioned (Midazolam, Diazepam, Lorazepam) facilitate amnesia and have anxiolytic and sedative actions by enhancing the inhibitory effects of neurotransmitters, particularly GABA.
122
What is the effect of Benzodiazepines on cardiovascular and respiratory function, contributing to their safety profile?
Benzodiazepines have minimal cardiovascular and respiratory depressant effects, which contributes to their safety in anesthetic procedures.
123
Why are opioids commonly used with anesthetics?
Opioids are used with anesthetics due to their potent analgesic properties, which are effective both intraoperatively and postoperatively.
124
What makes fentanyl and its congeners commonly used opioids in anesthesia?
Fentanyl and its congeners, such as sufentanil and remifentanil, are commonly used because they induce analgesia more rapidly and are significantly more potent than morphine.
125
How can opioids be administered during anesthesia?
Opioids can be administered intravenously, epidurally, or intrathecally.
126
Are opioids effective amnesics?
No, opioids are not considered good amnesics.
127
What side effects can opioids cause during anesthesia?
Opioids can cause hypotension, respiratory depression (especially with large doses of fentanyl), muscle rigidity, and postanesthetic nausea and vomiting.
128
How can the effects of opioids be reversed?
Opioid effects can be antagonized by naloxone.
129
What are the primary uses of neuromuscular blockers in anesthesia?
Neuromuscular blockers are used to abolish reflexes for tracheal intubation and provide muscle relaxation during surgery.
130
What is the mechanism of action for neuromuscular blockers?
Neuromuscular blockers work by blocking nicotinic acetylcholine receptors at the neuromuscular junction.
131
Can you name some commonly used neuromuscular blockers?
Common neuromuscular blockers include cisatracurium, pancuronium, rocuronium, succinylcholine, and vecuronium.
132
Do local anesthetics cause unconsciousness?
No, local anesthetics do not cause unconsciousness.
133
How are local anesthetics applied and what is their primary function?
Local anesthetics are applied or injected to block nerve conduction of sensory impulses from the periphery to the CNS.
134
What is the mechanism of action of local anesthesia?
Local anesthesia prevents action potentials by blocking sodium ion channels, which are necessary for the transient increase in permeability of the nerve membrane to sodium that is required for an action potential. This action results in the loss of sensation from the source of stimulation to the brain, leading to a loss of sensation in a limited region of the body.
135
Which local anesthetic compounds are most widely used?
The most widely used local anesthetic compounds are bupivacaine, lidocaine, mepivacaine, procaine, ropivacaine, and tetracaine. Lidocaine is probably the most commonly used among these.
136
Why can't some local anesthetics be used systemically, and which local anesthetic is an exception to this rule?
Some local anesthetics cannot be used systemically due to poor absorption. However, lidocaine is an exception and is used systemically as an antiarrhythmic agent.
137
How is Prilocaine metabolized and what is a potential side effect?
Prilocaine is metabolized in the plasma and kidneys, and one of its metabolites may lead to methemoglobinemia, which is a condition with an increased level of methemoglobin that decreases the blood's ability to carry oxygen.
138
Why should Mepivacaine not be used in obstetric anesthesia?
Mepivacaine is contraindicated in obstetric anesthesia due to its toxicity to neonates.
139
What factors are most important in influencing the onset and duration of action of local anesthetics?
The pH of the tissue and the pKa of the drug are the most important factors influencing the onset and duration of local anesthetics.
140
How does physiologic pH affect local anesthetics?
At physiologic pH, local anesthetics are charged ionized, which is the active form that interacts with sodium channels to inhibit their function.
141
How can the pH of infection sites affect local anesthetic action?
The pH may drop in sites of infection, causing the onset of local anesthetic action to be delayed or even prevented.
142
What does a low pKa indicate about a local anesthetic and its form at physiological pH?
A low pKa indicates that the local anesthetic is a weak base and will exist in a predominantly uncharged form at physiological pH.
143
What does a high pKa indicate about a local anesthetic and its form at physiological pH?
A high pKa indicates that the local anesthetic is a strong base and will exist in a predominantly charged form at physiological pH.
144
What effect do local anesthetics have on blood vessels, and how does this affect their duration of action?
Local anesthetics cause vasodilation, which leads to rapid diffusion of the drug from the site of application and a shorter duration of action when these drugs are administered alone.
145
What is the benefit of adding epinephrine to local anesthetics?
Adding the vasoconstrictor epinephrine to local anesthetics decreases the rate of local anesthetic diffusion and absorption, which minimizes systemic toxicity and increases the duration of action at the applied site.
146
What happens if a patient is allergic to one ester-type local anesthetic?
An allergy to one ester-type local anesthetic usually rules out the use of another ester, because the allergenic component is the breakdown product para-aminobenzoic acid, which is common to all esters upon metabolism.
147
Does an allergy to one amide-type local anesthetic rule out the use of another amide?
No, an allergy to one amide-type local anesthetic does not necessarily rule out the use of another amide, as their metabolic pathways may differ.
148
Can a patient be allergic to components in local anesthetics other than the active drug?
Yes, a patient may be allergic to other compounds in the local anesthetic, such as preservatives found in the vials.
149
Which local anesthetics belong to the amide group?
The amide group includes Lidocaine, Mepivacaine, Bupivacaine, Etidocaine, and Prilocaine.
150
Which local anesthetics belong to the ester group?
The ester group includes Cocaine, Procaine, Chloroprocaine, and Tetracaine.
