4 - General Anaesthetics Flashcards by G V

General Anaesthetics Parameters (5) That Are Reversible

Analgesia

Amnesia

Loss of consciousness

Inhibition of sensory and autonomic reflexes

Skeletal muscles relaxation

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Stages of Anesthesia (Guedel’s Signs): 1 - Stage of Analgesia (3)

Analgesia

Amnesia

End of this stage there is LOC and goes to next stage

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Stages of Anesthesia (Guedel’s Signs): 2 - Stage of Excitement (6)

LOC and begins to respire on own

Disinhibition

Delirious excitement

Irregular respiration

Amnesia

Reflexes enhanced, unpleasant stage that is reduced

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Stages of Anesthesia (Guedel’s Signs): 3 - Stage of Surgical Anesthesia (5)

Deep unconsciousness

Respiration is regular

Muscle relaxation

Planes 1,2,3, and 4 depending on patient size, eyeball reflexes, and diaphragmatic/chest muscles paralysis

Most surgeries are performed in plane 3

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Stages of Anesthesia (Guedel’s Signs): 4 - Stage of Medullary Paralysis/Toxic (2)

Severe respiratory and cardiovascular depression

Toxic

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Types of General Anaesthesia (2)

Intravenous - used to induce anaesthesia

Inhalation - used to maintain anaesthesia

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Intravenous Anaesthetics: Barbiturates (2 Drugs + statement)

Thiopental

Methohexital

Used to INDUCE anaesthesia

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Intravenous Anaesthetics: Benzodiazepines (2)

Midazolam

Diazepam

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Intravenous Anaesthetics: Opoid Analgesics (4)

Morphone

Fentanyl

Sufentanil

Alfentanil

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Intravenous Anaesthetics: Others (3)

Propofol

Ketamine

Etomidate

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Inhaled Anaesthetics: Gas (1 and Taken up by?)

Nitrous Oxide (Less soluble in blood (low coefficient), so faster induction of anesthesia)

Take up by alveoli by gas exchange

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Inhaled Anaesthetics: Volatile Liquids (5 and Taken up by?)

Halothane (More soluble in blood (high coefficient), so slower induction of anesthesia)

Enflurane

Isoflurane

Desflurane

Sevoflurane

Take up by alveoli by gas exchange

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Balanced Anaesthesia Defined

Combination of intravenous and inhaled drugs

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Inhaled Anaesthetics: Pharmacokinetics (Steps)

Anaestheic machine –> Breathing circuit via FGF –> Lungs –> Arterial and Venous blood –> Brain and back

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Factors Affecting Uptake and Distribution (2)

The concentration of an inhaled anesthetic in a mixture of gases is proportional to its partial pressure –> Higher the partial pressure of the gas in alveoli –> faster uptake of gas into the blood and into brain, faster inducing

Increase partial pressure by increasing the dose (concentration) of anaesthetic

The speed of induction of anesthesia depends on blood gas solubility

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Blood Gas Solubility: Gas Partition Coefficient Defined (Long)

Relative Affinity of an anesthetic/gas towards the blood compared with that of INSPIRED GAS
So, if the anaesthetic agent has more affinity towards the blood, it means it’s more soluble in blood (higher coefficient); if towards inspired air, less soluble in blood (lower coefficient)

An agent with a high coefficient that’s more soluble in blood, the MORE of the agent MUST BE DISSOLVED to RAISE the PARTIAL PRESSURE (so it takes time) –> INDUCTION of ANESTHESIA WILL BE SLOWER

On the other hand…

An agent with low coefficient that’s less soluble in blood diffuses from inspired air to the alveoli to blood, the rise in partial pressure will be much quicker (since it’s not soluble in blood) and rate of inducing anaesthesia will be faster

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Blood Gas Solubility: Coefficient

Less than 1 ==> Less soluble in blood, arterial tension rises quickly, fast onset of action of anesthesia (e.g. NO)

Greater than 1 ==> Highly soluble in blood, arterial tension rises slowly (takes time), slow onset of action of anesthesia

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Minimum Alveolar Concentration (MAC) Defined (4)

Measure of potency

Concentration of anesthetic at which 50% of subjects do not show a motor response to a surgical incision (so basically, dose of anesthesia required to perform surgery) –> Usually MAC of 1

If MAC value is low: potency is high (so only a small dose required for anasthesia)

1.3 MAC –> nearly 100% will NOT respond to stimuli

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Minimum Alveolar Concentration (MAC): Values (3)

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Nitrous Oxide: >100 (LEAST POTENT)

Halothane: 0.75 (Very potent)

Methoxyflurane: 0.16

Properties of Inhaled Anesthetics: Nitrous Oxide (4)

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MAC > 100% (INCOMPLETE anesthetic, so need large doses)

Good analgesia

Rapid onset and recovery due to low blood-gas coefficient

Used along with other anesthetic

Properties of Inhaled Anesthetics: Halothane (5)

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Not pungent (used for induction in children)

Bronchodilator

Medium rate of onset and recovery

Sensitizes the heart to epi-induced arrhythmias

HALOTHANE INDUCED HEPATITIS several days after procedure

Properties of Inhaled Anesthetics: Desflurane (4)

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Most rapid onset of action and recovery of the halogenated GAs

Widely used for outpatient surgery

Irritating to the airway (pungent) in awake patients and causes coughing, salivation, and bronchospasm (poor induction agent)

Used in maintenance of anesthesia

Properties of Inhaled Anesthetics: Sevoflurane (5)

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Very low blood: gas partition coefficient with relatively rapid onset of action and recovery

Widely used for outpatient surgery

NOT irritating to the airway

Bronchodilator

Useful induction agent, particularly in children

Properties of Inhaled Anesthetics: Isoflurane (3)

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Medium rate of onset and recovery

Used for induction and maintenance of anesthesia

Can cause irritation to airway

Adverse Effects of Inhalational GAs: Nephrotoxicity (2 points and 3 drugs)

Chances in renal concentrating ability Formation of fluoride form: Methoxyflurane, Enflurane, and Seveflurane

Adverse Effects of Inhalational GAs: Malignant Hyperthermia Defined, Volatile Agents + Muscle Relaxants, and Side Effects (Effects are 6)

Genetic disorder - AD Volatile agents (e.g.Halothane) + muscle relaxants (Succinyl Choline) Rapid onset of tachycardia and hypertension, severe muscle rigidity, hyperthermia, hyperkalemia, and acid-base imbalance

Adverse Effects of Inhalational GAs: Malignant Hyperthermia Rx Drug (1)

Dantrolene

IV Anesthetics: Barbiturates - Thiopental/Methohexital (5)

Can produce unconsciousness and surgical anesthesia in anesthesia in < 1 min Rx: induction of anesthesia and short procedures With single bolus - emergence from GA occurs in 10 min Cerebral metabolism, oxygen utilization, cerebral blood flow decreased Can precipitate porphyria

IV Anesthetics: Benzodiazepines Drugs (3)

Diazepam Lorazepam Midazolam

IV Anesthetics: Benzodiazepines Use (1)

Used as premedication for surgery prep: produce anxiolysis, amnesia, and sedation prior to induction of GA

IV Anesthetics: Benzodiazepines Midazolam has a more?

Rapid onset, a shorter elimination of half-life and is an inducing agent

IV Anesthetics: Propofol (5)

Rate of onset of action is similar to that of the intravenous barbiturates but recovery is more rapid and no hangover Patients subjectively "feel better" in the immediate postoperative period Both induction and maintenance of anesthesia as part of total intravenous or balanced anesthesia techniques Agent of choice for ambulatory surgery Effective in producing prolonged sedation in patients in critical care

IV Anesthetics: Propofol Adverse Effects (5)

Apnea Marked decrease in BP during inducation from vasodilation of veins and arteries Pain at site of injection Muscle movements/Hypotonus Clinical Infections may occur --> due to propofol containin lecithin (from eggs), which can cause infections

IV Anesthetics: Etomidate (5)

Rapid induction (~1 min) Short duration of action (3-5 mins) *Little effect on CV and Respiration* Maintains cardiovascular stability in patients with coronary artery disease, cardiomyopathy, cerebral vascular disease, or hypovolemia. Can cause post-op nausea

Opioids: Drugs (5)

Morphone Fentanyl Sufentanil Alfentanil Remifentanil

Opioids: High doses can cause?

Post-op-respiratory depression

Opioids Used For?

Post-op analgesia and premedication

Opioids: Neuroleptanalgesia Defined

State of analgesia and amnesia: Fentanyl + Droperidol

Opioids: NeuroleptanesTHIA (Drugs)

Fentanyl + Droperidol +N20 (Nitrous Oxide)

Opioids: Remifentanil is very?

VERY Potent but with a short half life

Ketamine: Defined

"Dissociative anesthetic" that produces a cataleptic state that includes intense analgesia, amnesia

Ketamine: Acts by?

Blocking NMDA receptor of glutamate

Ketamine: Increased Cardiovascular Effects (3)

Increased Heart Rate Increased arterial BP Increased cardiac output

Ketamine: Increased Neurological Effects (4)

Increased cerebral blood flow Increased oxygen consumption Intracranial pressure Can't use on patients with intracranial lesions

Ketamine: Emergence Phenomena (3)

Postoperative disorientation Sensory and perceptual illusions Vivid Dreams

4 - General Anaesthetics Flashcards

(45 cards)