Chapter 19 Flashcards
What is anesthesia?
Loss of feeling or sensation through administration of a drug or drugs
What are the three characteristics of general anesthesia?
- State of unconsciousness
- Analgesia
- Amnesia
- all three states must be present
When and how does regional anesthetics occur?
When sensory transmission from a specific area or region of the body to the CNS is blocked
What are the three ways that regional anesthetics can be administered?
- Epidural block
- Spinal block
- Peripheral nerve block
When is regional anesthesia drugs used?
To perform minor surgeries
- for a conscious patient or used with general anesthesia
How is local anesthetics different than regional anesthetics?
Similar to regional anesthetics, but on a smaller region of the body
What do neuromuscular blocking agents do?
Cause paralysis
- loss of motor function
What are the two different groups of neuromuscular blocking agents?
- Non-depolarizing
2. Depolarizing
What is the action of non-depolarizing NMBAs?
Bind to acetylcholine receptors and function as competitive antagonist
- preventing the binding of Ach
- end plate is unable to depolarize
What is the action of depolarizing NMBAs?
Closely resemble acetylcholine, binding to the receptor and functioning as an agonist
- cause continuous muscle depolarization and prevent repolarizing
What does PACU stand for?
Post-anesthesia Care Unit
What is the prototype drug for inhaled anesthetics?
Isoflurane (Forane)
What is the prototype drug for intravenous anesthetics?
Propofol (Diprivan)
What is the prototype drug for local anesthetics (that are used as regional anesthetics)?
Lidocaine (Xylocaine)
What is the prototype drug for non-depolarizing NMBAs?
Vecuronium (Norcuron)
WHat is the prototype drug for depolarizing NMBAs?
Succinylcholine (Anectine)
What is the most likely explanation for how general anesthesia works (since it’s unknown)?
- May provoke a decreased release of neurotransmitters
2. Increased re-uptake and inhibition of the post-synaptic enzymes
What is the action of local anesthetics (how do they work)?
Reversibly block all nerve impulses by disrupting membrane permeability to sodium during an action potential
- stopping the generation and propagation of nerve impulses
When will muscle fasciculation be present, with the use of depolarizing or non-depolarizing drugs?
Use of depolarizing drugs
- muscle is constantly contracting
Why are anesthetics called functional drugs?
Are not used to treat a pathologic disease
What are the 4 levels of sedation?
- Minimal sedation
- Moderate sedation and analgesia (conscious sedation)
- Deep sedation and analgesia
- Anesthesia
The goal of general anesthesia is to achieve, what 3 things?
- Akinesia (loss of voluntary movement)
- Analegsia (inability to feel pain)
- Amnesia (loss of memory)
What is balanced anesthesia?
When a combination of drugs are used rather than 1 single agent
What happens during Stage I, analgesia?
- loss of pain sensation
- still responsive until the end of the stage
What happens during Stage II anesthesia?
Delirium/excitement
- systolic pressure rises
- pt experiences excitation, agitation, restlessness, increase RR
What are potentially dangerous responses to Stage II anesthesia?
Vomiting, laryngospasm, tachycardia, uncontrolled movement
What happens during Stage III anesthesia?
Surgical anesthesia
- there are 4 stages within surgical anesthesia
- by stage IV, respiration ceases
What happens during Stage IV anesthesia?
Medullary depression
- Respiratory and vasomotor centres are depressed
- spontaneous respiration has ceased
- unless rapid intervention and support occur – death follows
What are the 2 drug classes of general anesthetic agents?
- Inhalant agents (like Isoflurane)
2. Parenteral agents (like Propofol)
Describe the pharmacodynamics of Isoflurane (inhaled anesthetic agent).
Unknown
- likely that the effects are mediated through physicochemical properties of the gases (lipid solubility, oil-gas, and blood-gas partition coefficients
What is the minimum alveolar concentration (MAC)?
A measure of potency
- concentration of anesthetic gas required to eliminate movement in 50% of patients challenged by a standardized skin incision
What does it mean if an agent has a small MAC? A large MAC?
The smaller the MAC, the more potent the agent
The larger the MAC, the less potent the agent
What is the MAC of Isoflurane administered alone? Administered with nitrous oxide?
Alone = 1.17%
With nitrous oxide = 0.56%
How does Isoflurane interact with NMBAs that are non-depolarizing?
Potentiates the effects of NMBAs and prolongs the blockade.
How are inhaled anesthetics administered and absorbed?
Administered through the lungs and absorbed across the alveolar membrane
What is Isoflurane (Forane) used for?
Anesthesia; induction, maintenance
What is the most serious adverse effect of Isoflurane?
Respiratory depression
What are intravenous (IV) anesthetics also known as?
Induction agents
What are some examples of classes of drugs that are IV anesthetics used as balanced anesthesia and total intravenous anesthesia (TIVA)?
Barbiturates
Benzodiazepines
Opioid analgesics
Non-barbiturate hypnotic agents
What is Propofol and what is it used for?
Intravenous anesthetic agent
- used for induction and maintenance of general anesthesia and maintenance of sedation in the ICU
How quickly will a patient loose consciousness after being administered Propofol?
Within 40 seconds and continues for 3-5 minutes after a bolus injection
What is the most serious adverse effect of Propofol?
Apnea and anaphylaxis
What are three examples of benzodiazepines that are used in balanced anesthesia?
- Diazepam
- Lorazepam
- Midazolam
What is fentanyl and what is it used for?
Opioid analgesic
- used in general anesthesia and conscious sedation
What are the 2 different groups that local anesthetic agents are divided into?
- Esters
2. Amides
What is the difference between esters and amides?
Esters = rapidly hydrolyzed in the body by plasma cholinesterase and other esterases Amides = slowly degraded in the liver by P-450 enzymes
What do local anesthetics do to the body?
Produce local or regional anesthesia and analgesia by blocking electrical transmission of pain along nerve fibres and abolishing sensations in a limited and well-defined area of the body
- WITHOUT loss of consciouss
In what order are the nerve fibres affected in local anesthesia?
- Autonomic
- Sensory
- Motor
What clinical manifestations are lost by the result of local anesthetics and in what order?
- Temperature
- Pain
- Touch
- Proprioception
- Skeletal muscle tone
What is the prototype drug for local anesthetic agents?
Lidocaine (Xylocaine)
- amide local anesthetic agent
When is Lidocaine used?
Regional blocks Peripheral nerve blocks Ophthalmic anesthesia Dental anesthesia Infiltration anesthesia
When Lidocaine is applied topically, what is it used for?
Dental pain
Neuropathic pain
Skin disorder (inflammation and irritation)
When Lidocaine is administered intranasally, what is it used for?
Migraine headaches
If Lidocaine is administered intravenously, what is it used for?
Ventricular tachycardia and ventricular fibrillation
What is the most serious adverse effect of Lidocaine?
Allergic reactions
What is the action of neuromuscular blocking agents?
Interrupt transmission of nerve impulses at the NMJ causing paralysis
Specifically, what is the action of NMBAs that are non-depolarizing?
They are competitive antagonists preventing the binding of acetylcholine to the cholinergic receptor
What happens if acetylcholine is unable to bind to the receptor (as seen in non-depolarizing NMBAs)?
End plate is unable to depolarize
How are depolarizing drugs different than non-depolarizing drugs?
Depolarizing drugs cause continuous muscle depolarization and prevents repolarization
What are some examples of non-depolarizing NMBAs?
Vecuronium
Rocuronium
Pancuronium
Cisatracurium
What is the prototype drug for non-depolarizing NMBAs?
Vecuronium
- an anesthesia adjunct
What is Vecuronium used for?
- to provide skeletal muscle relaxation
- facilitate intubation and mechanical ventilation
- improve surgical conditions during surgical procedures
How is Vecuronium excreted?
Kidneys
- watch renal function
How can Vercuronium be reversed?
By using anticholinersterases
- such as neostigmine, pyridostigmine, and edrophonium
- block the normal breakdown of acetylcholine at the motor end plate, causing the neurotransmitter to accumulate and returning muscle stimulation
How is NMBAs different than all other drugs discussed so far?
DO NOT affect consciousness or produce sedation!
- patients will be paralyzed
- unable to spontaneous ventilate
What is the most serious adverse effect of Vecuronium?
Prolonged paralysis and apnea
What is the action of depolarizing NMJ blockers?
By causing the muscle cell membrane to depolarize or become excited, which causes muscle contraction
- this leads to paralysis after repeated excitation
What is the prototype drug for depolarizing NMJ blockers?
Succinylcholine
What is succinylcholine used for?
Rapid endotracheal intubation
- other procedures that need a very short acting paralysis
Which receptors does Succinylcholine act as an agonist to?
Cholinergic nicotinic receptors of the motor end plate
Why do patients experience post-operative muscle pain when depolarizing NMJ blockers are used?
Because the muscles have been contracting rapidly, followed by flaccid paralysis
How is nitrous oxide used?
Used to increase the effectiveness of halogenated agents (Isoflurane) without severely depressing the depth of coma
