Step 1: General Anesthetics Flashcards
** Balanced anesthesia**
- Anesthesia produced by a combination of drugs, often including both inhaled and intravenous agents.
Inhalation anesthesia
Inhalation anesthesia
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Balanced anesthesia
Balanced anesthesia
Balanced anesthesia
Balanced anesthesia
Balanced anesthesia
A zxcasdfasdfasdfasdfasdfInhalation anesthesia
Anesthesia induced by inhalation of the drug
MAC (Minimal alveolar anesthetic concentration)
The alveolar concentration of an anesthetic that is required to prevent a response to a standardized painful stimulus in 50% of patients.
Analgesia
A state of decreased awareness of pain, sometimes with amnesia.
Stages of Anesthesia
- **Stage 1: ** Analgesia
- Stage 2: Disinhibition
- **Stage 3: ** Surgical Anesthesia
- Stage 4: Medullary Depression
** Inhaled Anesthetics (categories)tgorie( ca **
- Classification & Pharmacokintetics
- Elimination
- Miniminum alvelolar anesthetic concentration
- Effects of inhaled anesthetics
5.
Anestheisa protocols
Minor procedures: conscious sedation techniques that combine intravenous agents with local anesthetics are often used.
Extensive surfgical procedures: anesthesia protocols commonly include the use of IV drugs to induce the anesthetic state (inhaled anesthetics (with or without IV agents) to maintain an anesthetic staet and neuromuscular blocking agents to effect muscle relazation.
Inhaled Anesthesia
MOA
- Increase threshold fo rfiring of CNS neurons
- (potency of inhaled anesthetics is roughly proportionate to their lipid solubility.
- effects on ion channesl by interactions of anesthetic drugs with membrane lipies or proteins with subsequent effects on central neurotransmitter mechanism.
**Classification & Pharmacokinetics **
(inhaled anesthetics)
- Solubility (rapid equilibration with the blood, the more quickly the drug passes into the brain)
- Inspired gas partial pressure (high partial pressure of the gas, in the lungs –> more rapid achievement of anesthetic levels in the blood).
- Ventilation rate (greater the ventialtion, the more rapid is the rise in alveolar and blood partial pressure of the agent and the onset of anesthesia)
- Pulmonary blood flow (at high pulmonary blood flows, the gas parital pressure rises at a slower rate: thus the speed of the anesthetia is reduced)
- Arteriovenous concentration gradient (Uptake of soluble anesthetics into highly perfused tissues may decrease gas tension in mixed venous blood.)
Elimination
(Inhaled Anesthesia)
- Termination occurs by redistribution of the drug from the brain to the blood
- And elimination of the drug through the lungs.
MAC
(Minimum alveolar anesthetic concentration)
- Alveolar concentraiton required to eliminate the response to a standardize painful stimlus in 50% of patients.
- MAC values lower for adolescents and young adults vs. infants and elderly.
- Several anesthetic agents are used simultaneously, their MAC values are additive.
Effects of Inhaled Anesthetics
- CNS effects (decrease brain metabolitc rate, reduce vascular resistance and thus increase Cerebral blood flow–>increase in intracranial pressure).
- Cardiovascular effects (decrease arterial blood pressure moderately).
-
Respiratory effects (all inhaled anesthetics cause a dose-dependent decrease in tidal volume and minute ventilation, leading to an increase in arterial CO2 tension)
- malignant hyperthermia:
Malignant hyperthermia
- When anesthetics are used together with neuromuscular blockers (especially succinylcholine).
- This rare condition is thought in some cases to be due to mutations in teh gene loci corresponding to ryanodine receptor (RyR1).
- Treatment: Dantrolene w/supportive management.
IV Anesthetics
(BB POKE)
- Barbiturates
- Benzodiazepines
- Propofol
- Opioids
- Ketamine
- Etomidate
Barbiturates
Thiopental & methohexital
- Have lipid solubility (which promotes rapid entry into the brain and results in surgical anesthesia)
- Respiratory and circulatory depressants (b/c they depress cerebral blood flow, they can also decrease intracranial pressure).
Benzodiazepines
(Midazolam)
- widely used, adjunctively, with inhaled anesthetics and IV opoids
- slower than thiopental and it has a longer duration of action
- Benzodiazepine receptor antagonist, flumazenil, accelerates recovery from midazolam and other benzodiaepines.
Ketamine
(dissociative agent)
- dissociative anesthesia (in which the patient remains conscious but has marked catatonia, analgesia, and amensia.
- congener of the PCP (phencyclidine; psychotomimetic agent)
- benzodiazepines: can be used for emergence reactions wich occur during recovery from ketamine
Opioids
(Morphine & Fentanyl)
- used with other CNS depresssants (Nitrous oxide, benzodiazepines)
- IV opioids may cause chest wall rigidty that can impar ventilation
- Naloxone: can reverse postoperatively these respiratory depression made with the opioids
Opioids
(Neuroleptanesthesia)
- state of analgesis and amensia
- produced when fentanyl is used with droperiodol and nitrous oxide.
Propofol
(Phenols)
- produces anesthesia as rapidly as the intravenous barbituarates and recovery is more rapid.
- used as a component of balanced anesthesia and as an anesthetic in outpatient surgery.
- may cause marked hypotension during induction of anesthesia (primarily through decreased peripheral resistance)
- Total body clearance of propofol is greater than hepatic blood flow
Etomidate
(Imidazole)
- affords rapid induction with minimal change in cardiace function or respiratory rate and has a short duration of action
- (not analgesic
- advantage: anesthesia in patients with limited cardiac or respiratory reserve.
-
side effects:
- may cause pain and myoclonus on injection and nausea postoperatively.
- Prolonged administration may cause adrenal suppression.
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).
