Flashcards in General Anesthesia Deck (51):
Name the 4 Inhaled Anesthetic Agents.
1) NITROUS OXIDE
Name the 4 Intravenous Anesthetic Agents.
What are the 5 Major effects of a general anesthetic?
4) Attenuation of Autonomic Reflexes
5) Skeletal Muscle Relaxation
What are the 3 conditions of the IDEAL general anesthetic?
1) RAPID smooth loss of consciousness
2) RAPID reversal on discontinuation
3) WIDE margin of safety
What is CONSCIOUS SEDATION?
CONSCIOUS SEDATION (3 glasses of wine analogy)
1) AMOUNT - MINIMAL amount of amnestic and opioid
2) PATIENT INTERACTION - Still able to converse, respond to stimlui and commands
3) ABC - Able to protect airway and maintain ventilation
What is the continuum of conscious sedation -> General anesthesia?
Decrease in any of the 3 conditions of conscious sedation (Low amount, pt still able to interact and respond to stimuli, maintain airway and ventilation)
What condition distinctly differentiates SEDATION from GENERAL ANESTHESIA?
When the pt has LOST the ability to protect the airway and maintain normal ventilation
General anesthesia is actually **PREFERRED** by operators bec immobility/unresponsiveness to protecting the airway (e.g. aspirating, vomiting) is desired [Prevents potential pneumonitis]
What is BALANCED ANESTHESIA?
Utilizing SMALL doses of multiple agents (Inhaled, IV, Opioids, Benzodiazepines, Neuromuscular blocking drugs) to MINIMIZE side effects and MAXIMIZE efficacy
GASEOUS vs VOLATILE: What is the one commonly used gaseous anesthetic?
NITROUS OXIDE - Gaseous inhaled anesthetic (Gas at room temperature) Has GOOD Amnestic, and analgesic actions
GASEOUS vs VOLATILE: Is N2O inhaled agent used alone?
NO, almost ALWAYS used in addition to other agents
GASEOUS vs VOLATILE: What are the 3 volatile inhaled agents used?
VOLATILE - Liquid at room temperature
GASEOUS vs VOLATILE: What is the chemical structure of volatile inhaled agents? What is its importance?
D,I,S are FLUORINATED ethers - Fluoride addition stabilizes the ether -> Prevents ether flammability
INHALED ANESTHETIC ONSET: What is the major factor determining the ONSET of an INHALED anesthetic?
1) HIGH Fa - Alveolar fraction of anesthetic to its target organ (CNS) or Alveolar partial pressure
INHALED ANESTHETIC ONSET: How does the anesthesiologist control for a HIGH Fa (alveolar fraction) to CNS? (2)
1) HIGH Fi - Inspired fraction or partial pressure (vaporizer reading)
2) HIGH ALVEOLAR VENTILATION - High respiration rate of the pt
INHALED ANESTHETIC ONSET: What is the other factor that the anesthesiologist can NOT control for but still contributes to a HIGH Fa?
LOW SOLUBILITY (INSOLUBLE) of Inhaled Agent (Blood: Gas partition coefficient)
*Solubility is INVERSELY proportional to onset*
INHALED ANESTHETIC ONSET: Rank the onset of the inhaled anesthetics based on solubility.
N2O (Least soluble) > DESFLURANE > SEVOFLURANE > ISOFLURANE (Most soluble)
"No doctor sounds ill"
INHALED ANESTHETIC EMERGENCE: What is the Fi during emergence
ZERO - No more of the anesthetic is being delivered to the pt
INHALED ANESTHETIC EMERGENCE: What is the major determining factor of an inhaled anesthetic's emergence? What is a minor factor?
1) MAJOR: Alveolar Ventilation - The quicker the pt breathes, the more the gas can be removed from the lungs
2) MINOR: Metabolism
What is MAC? What does it measure?
Minimal Alveolar Concentration - Measures potency
Ex: 1MAC >> 10MAC in potency
How is MAC experimentally determined?
Basically P50 - ALVEOLAR partial pressure of the inhaled anesthetic at which 50% of the population of non-muscle relaxed pts remain immobile at skin incision
What is the effect of inhaled agents on major organ systems (CV, Respiratory, Hepatic, Uterine SM)
1) CV: DECREASE BP (Due to decreased SVR and negative inotropy)
2) Respiratory: Very shallow rapid breathing, INCREASED RR, DECREASED Vt = Decrease in minute ventilation (Respiratory Minute Volume)
**Respiratory minute volume (minute ventilation) = Vt * RR
3) Hepatic: DECREASED Portal Vein flow but increase in liver enzymes are rarely seen
4) Uterine SM: DECREASED Uterine tone (Helpful for C section- can deliver baby via small incision) BUT potential painful risk due to INCREASED Uterine bleeding
What is malignant hyperthermia (MH)?
Rare hypermetabolic syndrome that presents in GENETICALLY susceptible pts after toxicity due to exposure of triggering agents (Volatile inhaled agents + Succinylcholine)
What are the top 4 triggering agents that induce MH?
1-3) VOLATILE AGENTS - Desflurane + Sevoflurane + Isoflurane
What is the physiological event of MH?
Decrease in Ca2+ reuptake from the sarcoplasmic reticulum -> Excess Ca2+ buildup -> Prolonged muscle contraction
What are the 4 resulting events of MH? (4 H's)
1) HYPOXIA - Increased BMR
2) HYPERCAPNIA - Increased metabolism
3) HYPERTHERMIA - Feverish
4) HYPERKALEMIA - Rupture of constantly contracting cells
What is the antidote of MH? What is its mechanism of action?
DANTROLENE - Inhibits Ca2+ release from the sarcoplasmic reticulum (Very work intensive and time intensive, very short shelf-life)
What is the PREFERRED method of ANESTHETIC INDUCTION?
IV (PROPOFOL/ ETOMIDATE/ KETAMINE): What is the nature of the onset of these IV anesthetics?
RAPID ONSET OF ACTION
These three IV agents are LIPOPHILIC -> Preferentially partitions into highly perfused lipophilic tissues (Brain + Spinal cord)
IV (PROPOFOL/ ETOMIDATE/ KETAMINE): What is the nature of emergence of these three IV anesthetics?
RAPID EMERGENCE - Based on concentration gradient
IV anesthetics will rapidly redistribute from highly perfused tissues (e.g. brain) -> Lean tissues = Quick offset of action
RAPID LIVER METABOLISM (occurs later)
What is context sensitive half time? Is a high or low context sensitive half time desired?
Elimination half time after a prolonged continuous infusion
LOW Context sensitive half time is desired
IV AGENTS: What is the mechanism of action of PROPOFOL and ETOMIDATE?
GABA Agonist - Promote synaptic inhibitory neurotransmission
IV AGENTS: What are the amnestic and analgesic properties of PROPOFOL?
IV AGENTS: What is the effect of PROPOFOL on CV, Respiratory, and Nausea?
CV: Vasodilatory, negatively inotropic - Do NOT want to use on a pt who has cardiac myopathy
Respiratory: Decreased RR, Decreased Vt, Decreased Minute Volume, DECREASED upper airway reflexes - can intraoperatively vomit -> risk for aspirative pneumonitis
Antiemetic: Reduces nausea
IV AGENTS: What is the use of ETOMIDATE?
IV AGENTS: Which pt pool is it most beneficial to use ETOMIDATE?
Pts who have heart pathology OR can go into shock
Reason: ETOMIDATE has minimal hemodynamic effect (HR, BP, inotropy)
IV AGENTS: **Why can you NOT use ETOMIDATE for PROLONGED SEDATION?
Because Etomidate has a dose-dependent inhibition of 11-b-hydroxylase (important for cholesterol -> cortisol) = INHIBITION OF CORTISOL PRODUCTION
IV AGENTS: What are two distinct uncomfortable factors of using ETOMIDATE?
1) Burns on injection
2) Post-operative nausea/vomiting (Also known as "vomidate")
IV AGENTS: What is the mechanism of action of KETAMINE?
NMDA Receptor ANTAGONIST
IV AGENTS: What is the anesthesia state after administering KETAMINE?
Dissociative Anesthesia (Cataleptic State) With HORIZONTAL NYSTAGMUS - Not complete unconsciousness
IV AGENTS: What is the analgesic property of KETAMINE?
YES, ANALGESIC - Very helpful to treat burns
IV AGENTS: What is the effect of KETAMINE on CV, Respiratory, and upper airway reflexes
CV: INCREASED HR, Inotropy, and CO
Respiratory: MINIMAL if any respiratory depression
Upper Airway Reflexes: Preserved
IV AGENTS: What are the negative effects of using KETAMINE?
1) Hallucinations and unpleasant emergence may occur -> Therefore, coadminstration of benzodiazepine is recommended
2) INCREASED Lacrimations and Secretions (saliva)
IV AGENTS: What is KETAMINE'S potential drug interaction that can be utilized with regards to opioids?
Ketamine in SUBANALGESIC doses can LIMIT or REVERSE opioid tolerance
IV AGENTS: What is the use of DEXMEDETOMIDINE?
Adjunct to General Anesthesia
IV AGENTS: What is the mechanism of action of DEXMEDETOMIDINE?
Alpha-2 agonist receptors located in the locus ceruleus and spinal cord
IV AGENTS: What are the sedative and analgesic properties of DEXMEDETOMIDINE?
IV AGENTS: Which two IV agents are analgesic, and which two are NON-analgesic
NON-analgesic: Propofol + Etomidate
Analgesic: Ketamine + Dexmedetomidine
IV AGENTS: What is the effect of DEXMEDETOMIDINE on CV and respiratory?
CV: DECREASED BP, HR, CO
Respiratory: Preserved respiratory drive
IV AGENTS: Does the context sensitive half time of DEXMEDETOMIDINE make it a preferable drug or non-preferred?
Context sensitive time of dexmedetomidine is SIGNIFICANTLY INCREASED after 8hrs of infusion
IV AGENTS: What are the respiratory effects of all the inhaled agents PROPOFOL, ETOMIDATE, KETAMINE, DEXMEDETOMIDIINE?
Propofol + Etomidate = Respiratory Depressants
Ketamine + Dexmedetomidine = Preserved Respiratory Drive