General Anesthetics Flashcards
What are 5 major effects of GAs?
Unconsciousness, amnesia, analgesia, attenuation of autonomic reflexes, skeletal muscle relaxation
What are 3 characteristics of an ideal GA?
(1) Rapid, smooth loss of consciousness
(2) Quick on, quick off
(3) Wide safety margin
What is balanced anesthesia?
Using small doses of multiple agents: IV anesthetics --> induction Inhaled --> maintenance Opioids --> analgesia BZs --> amnesia Neuromuscular blocking drugs --> allows less use of inhaled
What is the difference between sedation & general anesthesia?
Patients under general anesthesia have lost their ability to protect the airway while sedated patients can protect their airway and also respond to stimuli and commands.
What are the differences between a gaseous and volatile anesthetic?
Gaseous - gas at room temperature (NO)
Volatile - liquid at room temperature; used mostly for maintenance (other inhaled GAs)
What is alveolar fraction?
Alveolar partial pressure; driving force for inhaled anesthetics to be uptake by CNS
How does inspired fraction influence anesthetic onset?
Higher the inspired fraction (amount of anesthetic flowing through airway), faster the anesthetic onset
How does alveolar ventilation influence anesthetic onset?
The greater the alveolar ventilation, the faster the anesthetic onset
How does blood solubility influence the onset of the GA?
More insoluble agents have a faster onset.
ISO (most soluble, longest) > SEVO > DES > N2O (fast but cannot be used alone)
What is the most important factor in emergence?
Alveolar ventilation
What is MAC?
Minimal Alveolar Concentration; 1/MAC measures potency!
Partial pressure of inhalational anesthetic in alveoli at which 50% of non-relaxed patients remain immobile in response to noxious stimulus (skin incision)
How do inhaled anesthetics impact cardiovascular, respiratory, hepatic systems and uterine smooth muscle?
CV: decrease in BP
Respiratory: increased RR, decreased minute volume (panting)
Hepatic: decrease in portal vein flow
USM: decrease in uterine tone
Which inhaled anesthetic can lead to hepatotoxicity
Halothane
Which inhaled anesthetic can lead to nephrotoxicity?
Methoxyflurane
Which inhaled anesthetic is proconvulsant?
Enflurane
Which inhaled anesthetic can cause expansion of trapped gas in a body cavity?
Nitrous oxide
What is malignant hyperthermia and what is it caused by?
Rare, life-threatening, hereditary condition; caused by decrease in Ca reuptake –> prolonged muscle contraction –> hyperthermia, hypercapnia, hypoxia, hyperkalemia, myoglobinuria
Induced by inhaled anesthetics (except NO) & succinylcholine
How is malignant hyperthermia treated?
Dantrolene
What are some features of the onset of IV anesthetics?
Lipophilic —> preferential partitioning into lipophilic tissues (brain & spinal cord) –> rapid onset
What are some features of the elimination of IV anesthetics?
Rapid redistribution from rapidly perfused tissues into lean tissues –> rapid offset
Liver metabolism too
What is context sensitive 1/2 time?
Describes the elimination 1/2 time after a continuous infusion
Propofol: type of GA; mechanism of action; clinical uses; features
IV anesthetic; GABA agonist; used for induction & maintenance of GA + sedation; non-analgesic but amnestic
What are some side effects of propofol use?
CV: vasodilation and decreased BP
Respiratory: decreased Vt, RR, minute volume
Anti-emetic
Etomidate: type of GA; clinical uses; features
IV anesthetic; Induction & short sedation; non-analgesic
