General & Local Anesthetics Flashcards
What are the General anesthetics drugs?
Inhalational anesthetics: sevoflurane, isoflurane, nitrous oxide
Intravenous anesthetics:
- propofol
- Barbiturates: thiopental
What are the Local anesthetics drugs?
- lidocaine, bupivacaine
What is the General anesthesia?
is a REVERSIBLE state of central nervous system (CNS) depression
What are the 5 important benefits of General anesthesia?
- Analgesia – surgical incision
- Hypnosis and sedation – loss of consciousness
- Amnesia – loss of memory
- Skeletal muscle relaxation
- Suppression of undesirable reflexes
What are the commonly used drugs for Inhalational general anesthetics?
- sevoflurane, isoflurane, nitrous oxide, …….
- Sedation – loss of consciousness
What are the commonly used drugs for Intravenous general anesthetics?
- Propofol: sedation
- Thiopental (barbiturate): sedation
What are the commonly used Adjunctive drugs?
several categories of drugs are used in combination with anesthetics:
- Benzodiazepines
- Narcotics (opioids)
- Neuromuscular blockers
What are the 3 steps of anesthesia?
a) Induction
b) Maintenance
c) Termination or Recovery
Step 1 of Anesthesia:
Induction:
- Induced by intravenous anesthetics (e.g. propofol, thiopental): Unconsciousness 30-45 seconds
- Adjunctive drugs
Step 2 of Anesthesia:
- Maintained with inhalation anesthetics (sevoflurane…..
- Adjunctive drugs
Step 3 of Anesthesia:
Termination or Recovery:
- Withdraw anesthetic admixture
- Monitor patients for consciousness; respiration, blood pressure, heart rate, intact reflexes….
- May give cholinesterase inhibitors, analgesics
- DETERMINED BY REDISTRIBUTION FROM SITES OF ACTION IN CNS, NOT BY METABOLISM OF THE ANESTHETICS
What are Inhalational anesthetics?
are nonflammable and nonexplosive
- gas (nitrous oxide),
- volatile and halogenated hydrocarbons (i.e. sevoflurane, isoflurane).
Maintenance of anesthesia after administration of an IV agent.
Depth of anesthesia can be rapidly altered.
Delivered in a recirculation system.
What are the Pharmacokinetics of Inhalation anesthetics?
Factors affect onset of action and elimination:
Onset of action:
- Blood/gas partition coefficient: Low coefficient = fast onset of action (=rapid rate of induction, rapid rate of recovery)
Elimination:
- drug effect is not terminated by metabolism of the drug
What are the Pharmacodynamics of Inhalation anesthetics?
Potency:
- minimal alveolar concentration (MAC) of anesthetic gas req. to abolish the response to surgical incision in 50% of pt’s
- MAC/potency relationship (HIGH MAC, LOW potency)
- Factors affecting MAC (lipophilicity) (HIGH potency, LOW MAC)
Action sites:
- Not fully understood
What are the ex’s of Inhalation anesthetics?
Nitrous oxide:
- It is not flammable; Non-irritating; “Laughing gas”
Sevoflurane:
- It is not flammable; volatile halogenated hydrocarbon; has
pungent odor.
What are the Pharmacokinetics (PK) of Inhalation anesthetics (Nitrous Oxide (N2O) vs Sevoflurane)?
Nitrous oxide:
- Blood/gas partition coefficient is low → low blood solubility → uptake rapidly
Sevoflurane:
- Blood/gas partition coefficient is higher than nitrous oxide
BOTH ARE NOT METABOLIZED — ARE NOT TOXIC TO LIVER & KIDNEYS
What are the Pharmacodynamics (PD) of Inhalation anesthetics (Nitrous Oxide (N2O) vs Sevoflurane)?
Potency; MAC
Nitrous oxide:
- MAC is high → Low potency, a weak general anesthetic.
- Does not depress respiration, not used alone for anesthesia
- MAY CAUSE DIFFUSION HYPOXIA
Sevoflurane:
- MAC is lower than nitrous oxide: it is more potent as an anesthetic than nitrous oxide
- Induces respiratory depression.
What is the clinical use of Inhalation anesthetics (Nitrous Oxide (N2O) vs Sevoflurane)?
Nitrous oxide
- 30-50% nitrous oxide and 20% oxygen – dental surgery
- Nitrous oxide has analgesic effects.
Sevoflurane
- Widely used inhalation anesthetic
- maintain a state of general anesthesia
What are ex’s of the Intravenous anesthetics?
Propofol & thiopental
What are the Intravenous anesthetics in general?
- Intravenous injection
- Thiopental – it is an ultra-short acting barbiturate
- Propofol – not barbiturate
What are the Pharmacokinetics (PK) of the Intravenous anesthetics (Propofol vs thiopental)?
Propofol / thiopental: High lipophilicity, rapid transfer across the blood-brain barrier – rapid action – induction of anesthesia is fast (30-45 seconds)
Propofol:
- Rapidly metabolized. NO CUMULATIVE EFFECT, LESS HANGOVER THAN THIOPENTAL
Thiopental:
- Slowly metabolized, accumulates in body fat, cause hang- over
What are the Pharmacodynamics (PD) of the Intravenous anesthetics (Propofol vs thiopental)?
- Enhance GABA-A receptor activation
- Directly activate GABA-A receptor
- Increases chloride channel-opening events →
hyperpolarization - Act as CNS depressants
What is the clinical uses of the Intravenous anesthetics (Propofol vs thiopental)?
For induction of anesthesia
What is Propofol’s clinical use?
- First choice for induction of anesthesia
- Useful for day case surgery
What is the concept of Local anesthetics?
refers to loss of sensation in a limited region of the body
CONSCIOUSNESS IS MAINTAINED
What is the classification of Local anesthetics?
- Esters: procaine, chloroprocaine, cocaine……….
- Amides: lidocaine, bupivacaine, mepivacaine……….
What are the Pharmacokinetics of Local anesthetics?
Systemic absorption, distribution and metabolism
- Play a lesser role than with systemic therapeutics
- Serve only to diminish or terminate their effect.
- Critical to the potential development of adverse reactions
- METABOLISM (BIOTRANSFORMATIONS):
- AMIDES: primarily in liver
- ESTERS: plasma cholinesterases
What are the Pharmacodynamics: Action sites of Local anesthetics?
1) BLOCK VOLTAGE-GATED SODIUM ION CHANNEL
- Inhibit neuron depolarization - Inhibit neuron activity
2) OTHER SITE: inhibit α- adrenergic receptor → vasodilation
What are the Clinical use of Local Anesthesia?
dental surgery, finger stitches, and surgery in the pelvis and legs.
Delivery techniques:
- Topical administration
- Infiltration
- Ring blocks
- Peripheral nerve blocks
- Neuraxial (spinal, epidural or caudal) blocks
MAY BE USED WITH A VASOCONSTRICTOR (EPINEPHRINE)
- Lower blood flow to injection site
- Decrease diffusion and absorption
- Increase duration of action
- Minimize systemic toxicity
