10-08 L2 General Anesthetics Flashcards
Components of Anesthesia
- Unconsciousness
- Skeletal muscle relaxation
- Analgesia (reduced pain)
- Amnesia
- Inhibition of autonomic reflexes
Propofol
- Unconsciousness
Benzodiazepine
- Amnesia
Fentanyl
- Analgesia
Glycopyrrolate
- Inhibition of reflexes
Vecuronium
- Skeletal muslce relaxation
Elimination of Benzodiazepine
- Liver (Conjugated to glucuronides)
- Body (Redistribution most important)
- Kidney (Eliminated by the kidney)
- Elimination slowed in the elderly, critially ill, (especially in sepsis)
- Pharmacogentic abnormalites (6% of patients accounting for slow metabolism of midazolam)
Benzodiazepines (short acting)
Short acting -Oxazepam (Serax) 5-15 none -Lorazepam (Ativan) 10-20 None -Midazolam (Versed) 6 alpha-hydroxymidazolam
Benzodiazepines (long acting)
Diazepam 20-80 N-desmethyldiazepam, N-methyloxazepam (temazepam), Oxazepam
Morphine
Active metabolite (M6G; Morphine-6-glucuronide excreted in the urine) -Elimination may be delayed in renal failure -During acidemia, 1/2 life of morphine in the brain prolonged by >50%
Fentanyl
-short duration of action (after a single dose due to high lipid solubility & redistribution) -Elimination 1/2 is longer than that of morphine (2-16 h v 1.5-6 h)
IV Anesthetics
Propofol -Ketamine -Etomidate -Dexmedetomidine Secondary -Methohexital, thiopental
Propofolo (Diprivan)
Advantages: rapid induction & emergence, pleasant, minimal ‘hangover’ Disadvantages: Danger of contamination, hypotension (decreased SVR), pain on injection, Respiratory depression, Expensive Dose Ranges: Bolus (1.0-2.5 mg/kg), Infusion: (0.05-0.2 mg/kg/min)
Ketamine
Dissociative state, side effects may be useful, sympathomimetic vagolytic (increases heart rate, blood pressure, bronchodilators) slow arousal, hallucinations may be a problem.
Etomidate
-Inhibits 11B-hydroxylase (converts 11B-deoxycortisol to cortisol) -Single dose may inhibit cortisol production for up to 48 h -Independent risk factor for death in CORTICUS study (28d mortality 43% v 30%, P=0.03) Less likely to respond to corticotropin (60% v 43.4%, P=0.004)
Dexmedetomidine (Precedex)
Alpha-2 adrenergic agonist, aprroved for sedation of intubated and ventilated patietns in an ICU setting -Administered by continuois infusion for up to 24 hours -Sedative, anxiolytic and analgesic effects -Not controlled substance.
Anesthetic uptake
Depends on alveolar concentration, Variables, inspired concentration- higher = faster (overpressure), solubility lower =faster, Alveolar ventilation - increased= faster, Cardiac output - lower = faster, Alveolar- venous difference - smaller = faster
Potency
Concentration of volatile anesthetics measured as partail pressure or % by volume. -site of action is the brain - but difficult to measure anesthetic concentration. -Use alveolar concentration as a surrogate for brain concentration.
MAC (Minimum Alvelar Concentration)
-Alveolar partial pressure of an inhaled anethetic that prevents movement of 1/2 the subjects in response to a noxious stimulus -The lower the MAC the more potent the drug. -MAC of individual drugs are additive -Amnesia occurs at 0.2-0.4 MAC
Factors affecting MAC
Decreases MAC (Extreems of age, hypothermia, hypotensino, other CNS depressents (opioids, alcohol) Increases MAC (youth, vigor, hyperthermia, drug tolerance)
Nitrous Oxide
Bone marrow depression and peripheral nueropathies w/long-term exposure -Diffusion into and expansion of closed gaseous spaces (bowel, pneumothorax)
What are some disadvantages to Fentanyl?
Patient recall during a surgery.
What are some disadvantages of using Desflurane?
- has high incidence of coughing
- sometimes brochospasms
What is a cause of malignant hyperthermia?
- halogenated anesthetics
- skeletal muscle relaxants (succinylcholine and tubocurarine)
What is the genetic presdiposition of malignant hyperthermia?
- Mutations in the gene for ryanodine receptor of L-type calcium channels
What should you use for treatment of Malignant hyperthermia?
- Dantrolene
- MOA: prevents release of calcium from the sarcoplasmic reticulum of skeletal muscle cells.
Which inhalation anesthetic has the fastest onset?
- A) Enflurane
- B) Isolflurane
- C) Nitric oxide (NO)
- D) Nitrogen dioxide (NO2)
- E) Nitrous oxide (N2O)
anwser is E. Nitrous oxide (N2O) this is used an inhalation anesthetic agent.
- realize that they can trick you on the names or just give you the molecular formula.
- Nitric oxide (NO) powerful vasodilator
- NO2:is a pulmonary irritant generated in fermenting silage; it may cause lethal pulmonary damage in farm workers.
What does ketamine do?
- causes analgesia and amnesia
- preservation of muscle tone and minimal depression of repiration.
What local anesthetic is reversed by flumazenil?
- Midazolam
- fluazenial (is a benzodiazepine receptor antagonist.
Which drug is associated with a high incidence of disorientation , sensory and perceputal illusions and vivid dreams during recovery?
What other drug would be given to reduce the side effects of the drugs mentioned?
- Ketamine
- Must adminstrate diazepam immediately before ketamine anesthesis
- (this reduced the incidence of these effects).
Halothane
Hepatic metabolism -Rarely caused immune-mediated hepatitis
Isoflurane
Weak coronary vasodilator
Desflurane
Low solubility, rapid induction and emergence, Rapid increase in concentration can produce tachycardia and hypertension
Sevoflurane
Least pungent volatile anesthetic Bronchodilator
