General Anesthesia Flashcards
Main difference between local and general anesthesia
Loss of consciousness with general anesthesia
Balanced anesthesia?
In addition to general anesthesia you also need to use opioids or NSAIDs
Balanced anesthesia provides (6)
- Amnesia
- Analgesia
- Reduce anxiety
- Sedation
- Sk. msk relaxation
- Suppress reflexes
(You must use multiple different drugs to obtain all of these effects)

Why are neuromuscular blockers used in general anesthesia?
- Tracheal intubation
- Muscle relaxation for surgery

2 routes of administration of general anesthetics
- Inhalation
- IV
Inhaled anesthetics are typically _______ (3)
Volatile, halogenated hydrocarbons
(except for nitrous oxide)
IV anesthetics usually consist of ______.
chemically unrelated drugs used to rapidly induce anesthesia
Adjunct agents used as pre-anesthetic medications (7)
- Anticholinergics
- Antiemetic
- Antihistamine
- BZD
- H2 blockers
- Non-opioid (tylenol)
- Opioids (fentanyl)
Why are anticholinergics used in anesthesia?
prevent bradycardia & secretion of fluids into the respiratory tract
What is the ideal stage of anesthesia for surgery?
Stage 3
(stage four risks death)

Three phases of anesthesia required for surgery
- Induction: admin (usually IV)→effect
- Maintenance (volatile anesthetics)
- Recovery: discontinuation → re-gaining consciousness
What does recovery from general anesthesia depend on?
- How fast the anesthetic diffuses from the brain
- Redistribution rather than metabolism
(recovery from inhalation drugs depends on respiration)
3 general mechanisms of action for general anesthetic
- Modulation of ion channels → increasesGABAA sensitivity→ increases Cl influx → depolarization
- NO & ketamine are mediated via inhibition of NMDA receptors (excititory))
- Inhalation anesthetics block excititory postsymnaptic currents of nicotinic receptors

Advantages of inhalation and anesthetics (3)
- Controlling depth of anesthesia
- Minimal metabolism (goes straight to brain)
- Excretion by exhalation
Factors influencing rate of induction of gen. anesthesia (6)
- Blood solubility
- Blood flow
- Concentration
- Second gas effect (effects are additive)
- Tissue solubility
- Ventilation rate and depth
(high blood gas solubility = slower rate of induction/recovery)

Rate of equilibrium of inhalation and anesthetics depends on ____
Blood/gas partition coefficient: ratio of anesthetic concentration in blood/alveolar space when partial pressures are equal
(Low blood/gas partition coefficient = higher rate of induction)

Low blood solubility = ______ rate of induction
fast
(high blood solubility = slow rate of induction)

Molecules with a higher λ (oil/gas) are _____ (more/less) potent.
more
(lipid-solubility increases potency)

High minimum alveolar concentration (MAC) = _____ (high/low) potency.
low
(High MAC = low potency)
The more lipid soluble the _____ (lower/higher) concentration needed and the ______ (lower/higher) the potency.
- lower
- higher
Factors that increase MAC (patient less sensitive) (3)
- Hyperthermia
- Drugs that increase CNS catecholamines
- Alcohol abuse
Factors that decrease MAC (6)
- Age
- α2-adrenergic receptor agonists
- Hypothermia
- Intoxication/other IV anesthetics
- Pregnancy
- Sepsis
Higher cardiac output removes anesthetic from the alveoli faster and slows the rate _____.
of rise in alveolar concentration of gas (takes longer for the gas to reach eq. between the alveoli & brain)
(higher cardiac output slows the rate of induction)
Why does nitrous oxide equilibriate rapidly
Insoluble in blood and other tissues
(this serves to concentrate co-administered halogenated anesthetics → second gas effect)
Primary use of inhalation of anesthetics
- Anaesthetic maintenance
- Depth altered by changing inhaled concentration
- Steep dose response curves
- Narrow therapeutic indices
(caution: no defined receptor for drugs)

Halogenated hydrocarbons are a potent anesthetic but a weak _____
analgesic
(same for propofol)
Why are halogenated hydrocarbons contraindicated in obstetrics?
Relaxes uterine muscles
(also causes bronchodilation, respiratory & cardiac depression)
Halogenated hydrocarbons are usually co-administered with ______ to achieve balanced anesthesia.
nitrous oxide, opioids, muscle relaxants and other adjuncts
Adverse effects of inhalation anesthetics
Malignant hyperthermia: mutation in RYR 1
Antidote to malignant hyperthermia
Dantrolene (blocks the release of calcium from the sarcoplasmic reticulum in muscle cells)
Isoflurane is less potent than ______ and is metabolized in the ____.
- Halothane
- Little metabolism (non-toxic to the liver or kidney)
Isoflurane uses
Muscle relaxation
(may cause hypotension)
Why is Sevoflurane used frequently in pediatric patients?
- Low pungency and respiratory irritation
- Rapid onset and recovery due to low blood solubility
- Low hepatotoxic potential
- Nephrotoxic potential
Sevoflurane uses
Induction (suitable for pediatric population)
(may be nephrotoxic)
Desflurane decreases _____ and _____ all major tissues.
- vascular resistance
- perfuses
Desflurane: onset, solubility, volatility
- rapid onset
- low blood solubility
- low volatility (admin. via heat vapor)
(not for inhalation-causes respiratory tract irritation)
Nitrous oxide non-halogenated (aka laughing gas) characteristics
- Potent analgesic
- Weak general anesthetic
- Poorly soluble in blood and other tissues (moves rapidly in and out of the body)
Uses of nitrous oxide non-halogenated laughing gas
- Combined with other more potent agents for surgical anesthesia
- Dentistry
Side effects of nitrous oxide non-halogenated laughing gas
- Diffusion hypoxia
- Chronic exposure can cause megaloblastic anemia
(must give full O2 to bring them out)
What sets sevoflurane apart from isoflurane and desflurane?
Decreased respiratory reflexes
(the other to cause an initial simulation)

Tissue compartments (3)
- Vessel rich group vs. vessel poor group
- Skeletal muscle (moderate perfusion)
- Fat (poor profusion)
(highly perfused issues = rapid steady state; poor profusion = reservoir)
Which tissue is our vessel-rich group (5)
- Brain
- Endocrine glands
- Heart
- Kidney
- Liver
3 tissues that are vessel-poor groups?
- Bones
- Ligament
- Cartilage
The rate of induction depends on which factors (2)?
- Lipid-solubility (higher is better)
- Arteriole concentration
General anesthesia recovery depends on ______ (2)
- Redistribution from CNS
- Metabolism and plasma clearance with repeated doses
The greater the cardiac output, the _____(more/less) anesthetic enters the cerebral circulation. Decreased CO will cause ______(rapid/prolonged) circulation time.
- more (dose must be reduced)
- prolong
(Cardiac output with the inhalation drug quickly transports blood to brain = slower induction time)
Propofol uses
- Induction (fast - 30-40 sec)
- Maintenance (due to re-distribution)
Propofol side effects (4)
- Muscle twitching, spontaneous movement, yawning & hiccups
- Decrease BP
- Reduce ICP
- Less depressant affect than volatile anesthetic
(No analgesic effect)
Etomidate used for _______; good for patients who have ______.
- Hypnotic agent used for induction
- coronary artery disease are cardiovascular dysfunction
Etomidate characteristics (3)
- Rapid induction
- Short-acting
- Little to no effect on heart and circulation
(good for patients w/cardiac dysfunction)
Etomidate adverse effects (2)
- Decrease plasma cortisol and aldosterone levels by inhibiting 11 beta-hydroxylase involved in steroidogenesis
- Seizure
Ketamine MOA
NMDA receptor antagonist
(aka PCP- dissociates patients)

Ketamine uses (3)
- Induction and maintenance
- Patients with hypovolemic or cardiogenic shock, asthmatics, pediatric patients (does not cause them to have dissoc. amnesia)
- Stimulate central sympathetic outflow

Ketamine contraindications
Hypertensive or stroke patients due to the stimulation of the central sympathetic outflow
(side effect: hallucination, disorientation)

_______ has a higher blood solubility than desflurane & sevoflurane.
Isoflurane
Barbiturates activate the _____ receptors
GABA (inhibition)
(potent anesthetic but weak analgesic)
Why do barbiturates remain in the body for a long time?
(ex: Methohexital)
Small percent is metabolized by the liver
(enters and exits the CNS rapidly)
Barbiturate side effects (2)
(ex: Methohexital)
Respiratory and cardiovascular depression

Benzodiazepines (ex: Midazolam) uses
- Sedation
- Amnesia
(they act on Gaba receptors, like barbiturates)

All benzodiazepines have potential to depress the respiratory system & can induce temporary _____.
Anterograde amnesia
______ may prolong the effects of midazolam (benzodiazepine).
Erythromycin
(reversed by flumazenil)
Administration route of opioids
- IV
- Epidural
- Intrathecal
Physiologically all opioids will cause _____ (3) side affects.
- Respiratory depression
- Muscle rigidity
- Post anesthesia N/V

Neuroleptanalgesia (twilight sleep) is induced with _____ (2).
Fentanyl + droperidol (antipsychotic)
(side effect: chest wall rigidity)

What determines the speed of recovery from intravenous and anesthetics used for induction?
Redistribution of the drug from sites in the CNS
Which medication is a potent intravenous anesthetic but a weak analgesic?
propofol
(as well as halogenated hydrocarbons; must give with an analgesic)
What would you expect to see in a patient with heart failure and significantly reduced cardiac output during surgical anesthesia?
Slower induction time with IV anesthetics
General anesthesia can lead to hypertension which may result in _____
Reduced perfusion pressure and ischemic tissue injury
What are two things to consider in regards to the respiratory system when choosing an anesthetics?
- All supress respiration (inhaled, IV & opioid)
- Inhaled agents may also bronchodilate
What is the concern with repeated administration halogenated hydrocarbons?
Release of fluoride, bromide → damage to liver, kidney & CNS
(neurologic disorders)
General anesthetics in early pregnancy may cause ______(2).
- Disrupt fetal organogenesis
- NO → plastic anemia in fetus
Dexmedetomidine is a _______ & _______ used in ICU settings
- analgesic
- sedetive
Dexmedetomidine decreases the release of ________ leading to hypotension & bradycardia.
catecolamine by stimulating a2 receptors in the brain
What makes remifentanil unique
rapidly metabolized
Remifentanil is an _____ at low doses and a _____ at higher doses.
- anxiolytic
- sedative
Transient use of nitrous oxide in pregnant patients may cause _______ in the fetus
aplastic anemia
Inhaled agents depress respiration but also act as _______.
bronchodilators
Which 4 general anesthetics are used for induction?
- propofol
- ketamine
- sevoflurane
- etomidate
(propofol & ketamine are also used for maintenance)
Which 2 general anesthetics are used for maintenance (as well as induction)?
- Propofol
- Ketamine