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20 Cards in this Set
- Front
- Back
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Stages of anesthesia:
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Stage I: analgesia-decreased awareness of pain with some amnesia
Stage-II: disinhibition- delirious and excited. Reflexes are enhanced, irregular respiration Stage-III: surgical anesthesia-Pt unconscious, no pain and reflexes Stage-IV: Medullary paralysis- severe respiratory and cardiovascular depression |
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Classification of General anesthetics
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Inhaled anesthetics (gases or volatile liquids)
Intravenous anesthetics |
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Minimal alveolar concentration (MAC)
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measure of potency of Inhaled Anesthetics
MAC is defined as the minimal alveolar anesthetic concentration at which 50% of patients do not respond to a surgical stimulus Less the MAC, more the potency of a drug Methoxyflurane is the most potent (0.16) and the nitrous oxide is the least potent anesthetic (105.0) |
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Give graph with data- which one is most potentent? The one with the
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SMALLEST MAC conc!
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Which drug has the longest duration of action- (lipid solubility, or soluble in plasma= both different ways to ask same thing)=
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Desflurane
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Blood-gas partition coefficient:
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Determine the duration of action- HOW FAST ( fast drug- short duration of action)
The rate of onset and recovery depend on the individual (drug not person) blood gas partition coefficient Blood gas partition coefficient is a measure of blood solubility of the anesthetic gas The more soluble the anesthetic in the blood, the longer it takes to achieve a partial pressure which will allow the gas to move from the blood into CNS Anesthetics with high blood-gas solubility ratios are slow in onset and slow in recovery Good anesthetic: low MAC and low blood gas partition ratio |
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2. Inspired gas partial pressure:
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Higher the partial pressure of the gas in the lungs, the more rapid the induction
Can be achieved by giving high concentrations of gas initially (than that required for maintenance) |
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3. Ventilation rate:
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The greater the ventilation rate the more rapid is the onset of anesthesia
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4. Pulmonary blood flow (which is decided by cardiac output):
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Higher the pulmonary blood flow the slower the onset of anesthesia
Higher blood flow means that same volume of gas from the alveoli diffuses into a larger volume of blood per unit time |
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Nitrous oxide
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least potent of the inhalational anesthetics
Nitrous oxide is frequently used as a component of balanced anesthesia in combination with another anesthetic agent Nitrous oxide has significant analgesic and amnesic properties People that cannot take a full dose- ex ppl with kidney prob etc, older ppl |
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Enflurane
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myocardial depressants – decrease cardiac output
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Halothane
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sensitizes the myocardium to catecholamines Arrhythmia*
hepatic toxicity malignant hyperthermia- rare condition due to uncontrolled release of Ca by endoplasmic reticulum Treated by dantrolene |
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Intravenous anesthetics
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Barbiturates: thiopental (inducing agent)
Benzodiazepines: midazolam (inducing agent), diazepam (maintaince agent) Dissociative anesthetic: ketamine Opioids: morphine and fentanyl Propofol The more the lipid solubility of these drugs the faster it enters CNS |
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Barbiturates
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Have a high lipid solubility
High lipid solubility promotes rapid entry into the brain Results in surgical anesthesia in one circulation time (1 minute) Used as inducing agents for short surgical procedures Termination of anesthetic effects by redistribution from brain to other tissues Elimination after metabolism in liver Barbiturates are circulatory and respiratory depressants |
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Benzodiazepines
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Midazolam: widely used with inhaled anesthetics
Onset of effect slower than thiopental Longer duration of action Severe postoperative respiratory depression can occur Flumazenil to reverse the effects of midazolam |
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Ketamine
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patient remains conscious
Has marked catatonia, analgesia and amnesia Acts as an antagonist to glutamic acid (blocks the actions of glutamate on NMDA receptor) Ketamine is a cardiovascular stimulant (Heart rate, arterial blood pressure, and cardiac output are increased) Increases intracranial pressure Hallucination, excitation, disorientation can occu |
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Opioids
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Morphine and fentanyl
Are used with other CNS depressants (Nitrous oxide and benzodiazepines) Valuable in high risk patients where the patient may not survive a full dose of anesthetic Cocktail of drugs are used may cause chest wall rigidity which can impair ventilation |
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If we notice chest wall rigidity, ventilator not working well- drug?
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was prob morphine or another opiods
need to use naloxone – antagonist |
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Propofol
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Induces anesthesia at a rate similar to thiopental
More rapid recovery than barbiturates Commonly used as an anesthetic in outpatient surgical procedures May cause marked hypotension (decreased PVR) |
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Etomidate
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Rapid induction
Minimal change in cardiac functions Short duration of action Advantage in patients having a poor cardiovascular status ADR: Pain and myoclonus on injection Prolonged administration can cause adrenal suppression |
