Pharmacology of General Anesthetics Flashcards
True/False. Etomidate is an anesthetic.
False. Etomidate acts only as general anesthesia.
What are the advantages of ketamine?
Strong analgesia, no significant respiratory depression, CV support (increased HR & BP)
What is Minimum Alveolar Concentration (MAC)?
The minimum partial pressure of an inhaled anesthetic in the lungs required for 50% of patients to not feel a surgical incision (1 MAC). The dose-response curve is extremely steep. At 1.1 MAC, 95% of patients do not feel a surgical incision
True/False. N2O is an inhalation anesthetic that will take patients into stage 3 of anesthesia.
False. N2O can induce loss of consciousness, but will not take patients beyond stage 2 of anesthesia - even at 100% N2O
Why are benzodiazepines given before surgery?
To relieve anxiety
Where is the body do general anesthetics most accumulate?
Adipose tissue - general anesthetics are highly lipid soluble to cross the BBB
When is ketamine most commonly used?
Emergency surgeries, outpatient procedures, diagnostic procedures in children, changes to burn dressings
What are the disadvantages of ketamine?
Prolonged retention in the body, adverse psychological reactions (less than PCP), flashbacks up to a year after use
This general anesthesia is no longer used due to adverse psychological reactions, but is used as an illicit drug.
Phencyclidine (PCP)
What are the uses of N2O?
Analgesic (dentistry, early labor), Induction of general anesthesia
General anesthetics have a very (low/high) therapeutic index.
Low therapeutic index - making them very dangerous
Describe the pharmacokinetics of propofol.
Wide tissue distribution, hypnosis within 40s, general anesthesia within 1-3 minutes
True/False. Respiration is normal during surgical anesthesia.
False. While respiration may be regular, it is typically abnormal. Respiration usually slows.
What drug may be given before surgery to increase HR and counteract bradycardia?
Atropine
What are the disadvantages of thiopental?
Poor moment-to-moment control, poor analgesia, respiratory depressant, poor skeletal muscle relaxation
What is the MOA of ketamine?
Antagonist of the NMDA receptor to block glutamate binding
This drug induces dissociative anesthesia. Patients eyes are open, but they appear to be in a trance and are unresponsive to painful stimuli.
Ketamine
What stage of anesthesia is most risky and where problems generally begin to arise?
Stage 2 - loss of consciousness and depression of the cortex
What risks are associated with enflurane use?
Fluoride toxicity, seizures in patients with a seizure disorder
What is the relationship between blood/gas coefficient and recovery time?
A higher blood/gas coefficient leads to longer recovery time
How can induction time of inhaled anesthetics be reduced (similar to a drug loading dose)?
Higher gas concentration, faster respiration, deeper breaths
These inhalation drugs can be used to induce general anesthesia and relax skeletal muscles.
Isoflurane, enflurane, sevoflurane (exception is desmoflurane that causes bronchospasms)
Seizures, confusion, hallucinations, hyperventilation, and bronchospasms are associated with what general anesthesia?
Propofol
What is the proposed MOA of general anesthetics?
Hyperpolarization due to K+ efflux or Cl- influx
A general anesthetic has a very high blood/gas partition coefficient. What does this tell you about drug solubility and effectiveness?
The drug is highly soluble in the blood, but this also means it will take longer for the drug to exit the blood and enter tissues - thus there is a longer induction time
True/False. Propofol is an anesthetic.
True. Propofol induces general anesthesia and also has some anesthetic ability
Describe the pharmacokinetics of thiopental.
Administered via IV, anesthesia within seconds, rapid redistribution and emergence, not biotransformed
What drug may be given before surgery to decrease secretions?
Scopalamine
What is the primary point of action of thiopental?
Reticular Activating System (RAS)
This drug is used as sole general anesthesia for short procedures without significant pain.
Thiopental
This drug has the lowest biotransformation of the volatile liquid inhalants, but it not recommended for induction of anesthesia due to the high incidence of bronchospasm.
Desmoflurane
This IV general anesthetic is biotransformed by the liver and excreted by the kidney.
Etomidate
What ADRs are associated with chronic toxicity of N2O?
Ataxia, leg weakness, peripheral neuropathy, impotence. This generally happens amount healthcare providers, not patients
What is the primary site of action of ketamine?
Cerebral cortex and limbic system
This drug is often used for outpatient and diagnostic procedures.
Propofol
What ADRs are associated with Etomidate?
Myoclonic muscle movements, hypotension, tachycardia, hyperventilation, apnea, hiccups, post-op nausea and vomiting
