General Anesthesia Flashcards
Pharmacodyamic effect on organ systems:
- CV
- Resp
- Hepatic
- Uterine Smooth Muscle
- CV: decrease BP
- Resp: decrease minute volume (increase RR, decrease Vt)
- Hepatic: decrease portal vein flow
- Uterine Smooth Muscle: decrease in uterine tone (may lead to increase in uterine bleeding)
Three major IV anesthetics
- Propofol
- Etomidate
- Ketamine
Propofol
- used for induction and maintenance of GA as well as sedation
- important to use w/in 8 hrs of dispensing to prevent bacterial contamination
- GABA angonist
- non-analgeisic
- amnestic
- CV: vasodilatory and negatively inotropic
- Respiratory: decrease in Vt, RR, and Minute volume
- Decrease in Upper Airway Reflexes
- Antiemetic (effective against vomiting and nausea)
Etomidate
- minimal hemodynamic effect (on HR, BP, inotropy)
- used for induction and short sedation
- GABA angonist
- non-analgeisic
- can lead to hypoadrenal syndrome (inhibits 11 Beta hydroxylase)
- may cause vomit/nausea
Ketamine
- use sparingly
- dissociative anesthesia with nystagmus
- NMDA receptor antagonists
- analgesic
- increased in HR, BP, and CO
- minimal if any respiratory depression (pts will keep breathing)
- airway reflexes are preserved in most situations
- may cause hallucinations
Dexmedetomidine
- alpha-2 agonist (decrease HR and BP)
- used for sedation or adjunct to GA
- sedative and analgesic
- context sensitive 1/2 time is significantly increased after 8 hours of infusion
What are the major effects of a general anesthetic?
1) Unconsciousness
2) amnesia
3) analgesia
4) attenuation of autonomic reflexes
5) Skeletal muscle relaxation
What is the difference between sedation and general anesthesia?
Once pt has lost ability to protect the airway = general anesthesia
“Conscious sedation”: minimal amts of amnestic and opiod; able to protect airway and maintain ventilation
What are the major factors involved in the onset of and emergence from an inhalational anesthetic?
ONSET:
- ideal agent is fast on/fast off with adequate potency
- alveolar fraction (alveolar partial pressure) is driving force for uptake to target organ (CNS)
- anesthesiolgist controls: inspired fraction (F_I_) and increased alveolar ventilation
- more insoluble agents have faster onset (agent dependent)
EMERGENCE FROM:
- alveolar ventilation is the most important factor
- metabolism is minor
- think: onset in reverse, except F_I_ is zero
What is MAC? (significance)
Minimal Alveolar Concentration
measure of potentcy
- partial pressure of inhalation anesthetic in the alveoli at which 50% of a population on non-relaxed pts remain immobile at skin incision
- high MAC means lower potency (relative to another drug with lower MAC)
What are the IV agents?
Propofol
Etomidate
Ketamine
Dexmedetomidine
What is MH (malignant hyperthermia)?
- hypermetabolic syndrome in genetically susceptible pts after exposure to triggering agents (halogenated inhalatinals and succinylcholine)
- rare incidence
- caused by decrease in reuptake of Ca2+ from sarcoplasmic reticulum
- prolonged muscle contraction –> hyperthermia, hypercapnia, hypoxia, hyperkalemia
- antidote: dantrolene
Explain balanced anesthesia
combo of inhaled and IV (multiple agents)
Volatile vs. Gaseous
Gasous: gas at room temp; currently only Nitrous Oxide (Xenon is experimental); good amnestic and analgestic actions
Volatile: liquid at room temp; halogenated ethers (isoflurane, sevoflorane, desflurane); used primarily for maintenance, except in peds, where it is used for induction
What is the difference between the IV anesthetic agents?
propofol/etomidate/ketamine: all lipophlic, rapid onset, preferential partitioning to highly perfused lipophilic tissues (brain and spinal cord)
