General Anesthetics Flashcards
Intravenous Anesthetics: Barbiturates and Non-Barbiturates
Barbiturate: Methohexital
Non Barbiturate: Propofol, Etomidate, Ketamine
Inhalation anesthetics
- Nitrous Oxide (gas)
- Deflurane
- Halothane
- Isoflurane
- Sevoflurane
Inhalation anesthetics have a broad or narrow therapeutic index?
Narrow (2-4)
Sevoflurane is the least ____________ ether for anesthetics.
Pungent- least irritating so used in children.
T/F: Inhalation anesthetics require special equipment and monitoring while IV anesthetics require monitoring but no special equipment.
True
Current theory of the MOA of inhalation anesthetics
Anesthetics reversibly interact with hydrophobic sites specific membrane proteins, altering signal transduction pathways.
Targets for inhalation anesthetics
1) Enhancement of inhibitory GABA-A, glycine receptor activity
2) Inhibition of excitatory glutamate, nicotinic, 5-HT3 receptors.
3) Voltage gated ion channels (Na, K)-inhibits action potential propagation
4) GPCRs
What are 3 factors that affect rate of anesthetic uptake
1) Blood solubility
2) Alveolar blood flow
3) Difference in “partial pressure” of agent in alveolar gas vs. venous blood
T/F: Most important determinant of rate of induction; counter-intuitively, agents with LOW blood solubility have more RAPID induction.
True
The concentration of inhaled anesthetics is expressed as _______________ (% of total atmospheric pressure) rather than concentration.
Partial pressure
T/F: Partial pressure exerted by any gas in a mixture of gases is proportional to the concentration of each gas (vol%). Give an example as of how to find partial pressure.
True: 7L nitrous oxide +3L oxygen= 70% NO
-Partial pressure of NO=70%x760mm hg= 532mm
T/F: The more soluble an anesthetic agent is in blood, the less that must be taken up before partial pressure in brain can reach equilibrium.
False: the more that must be taken up
Explain concentration gradient and “second gas” effects on uptake
If a second gas is delivered along with nitrous, the concentration gradient effect of nitrous accelerates uptake of the 2nd drug.
Tissue solubility of anesthetics: The ________ is highly lipophilic and receives 3X the blood flow of other tissues; other tissues will equilibrate more slowly.
Brain- equilibrium is reached when the partial pressure among various tissues are equivalent.
Potency of inhalation anesthetics is defined by the
Minimum alveolar concentration.
T/F: A high MAC in inhalation anesthetics correlates with high solubility.
False: correlates with low solubility
What maintains alveolar tension and hastens induction; more important for agents with high blood solubility.
Pulmonary Ventilation rate
Rank order of liver metabolism of Inhaled anesthetics
Halothene> enflurane>sevoflurane>isoflurane>deflurane>NO
Recovery is __________ with more blood soluble anesthetic agents.
Prolonged
T/F: If potency is low and drug is not very soluble (NO), then the alveolar concentration necessary to establish anesthesia cannot be reached while providing adequate oxygenation.
True
Factors that increase MAC (decrease potency)
- Infancy
- Chronic alcohol intake
- Hypernaturemia
- Sympathomimetics
Factors that decrease MAC (increase potency)
- Elderly
- Acute alcohol intake
- Pregnancy
- Opoids,sedatives
- Hypothermia
What is a rare but life-threatening, hypermetabolic syndrome in genetically predisposed individuals exposed to a volatile anesthetic or muscle relaxant.
Malignant Hyperthermia
A patient was administered halothane and know shows unexplained tachycardia, hypercarbia, tachypnea, acidosis, muscle rigidity, hypoxemia, ventricular arrhythymias, hyperkalemia, and elevated body temp. What does this patient have
Malignant hyperthermia- death if untreated
Treatment for Malignant hyperthermia
-Stop trigger
-Cool, iced normal saline
-100% Oxygen 10L/min
etc.
Cause of Malignant Hyperthermia
Mutation in skeletal ryanodine receptor calcium release channel
What is the main contributor to duration of action in intravenous anesthetics
Redistribution out of CNS
Methohexital is a ___________ acting barbiturate whose mechanism activates barbiturate binding site on _________receptors. Onset is 30 sec and duration is _______ min. The use is…
1) Short-acting
2) GABA-A
3) 10 min
4) induction of anesthesia and procedural sedation
Most commonly used IV agent in US.
Propofol
Mechanism of propofol
GABA-A agonist: Sedative and amnestic but not analgesic
Onset and duration of propofol
40 sec, 6 min
Use of propofol
General anesthesia induction and maintenance.
- Procedural sedation
- Post-op anti-emetic
Side effects of propofol
- Hypotension, resp. depression
- Pain at injection site potential for inducing hypertriglyceridemia
Mechanism of Etomidate
Potentiation of GABA-A currents
- Minimal CV and resp effects
- Not analgesic
Use of Etomidate
Induction and maintenance of general anesthesia.
- Procedural sedation (off label)
- Patients with hypotension
SE of etomidate
- Injection site pain
- Myoclonic movements
- Some post op nausea and vomiting
- Adrenal insufficiency with continuous infusion
Intravenous anesthetic that is a derivative of PCP
Ketamine
What anesthetic is this: NMDA receptor antagonist (blocks glutamate).
1) Produces dissociative sedation.
2) Produces significant analgesia and bronchodilation.
3) Minimal cardiovascular effects
Ketamine
Use of Ketamine
- Less often due to unpleasant emergence phenomenon.
- Induction and maintenance of pediatric anesthesia; children are less prone to unpleasant emergence.
- Procedural analgesia/sedation (off label); for brief painful procedures like fracture.
- Patients with airway disease.
Side effects of Ketamine
CNS psychotomimetic- vivid dreams; hallucinations; distorted visual and auditory sensitivity; associated with fear and confusion but may also produce euphoria; counteracted in adults with benzodiazepines.
-Some nausea/vomiting, tachycardia and hyper-salivation.
