Anaesthesia Flashcards
What is the affect of anesthetics on the body?
Depress CNS, which causes:
- Loss of conciousness
- Loss of reponsiveness to sensory stimuli
- Relaxation of muscles
- Analgesia
In what forms are general anesthetics typically administered?
- Volatile liquids or gases vaporized in oxygen
- Administered by inhalation as a gas or by injection as a liquid
What are the 5 drug responses of general anesthesia?
- Analgesia
- Amnesia
- Inhibition of reflexes
- Skeletal muscle relaxation
- Rapid hypnosis
Can a single drug provide all 5 drug responses of general anesthesia? What must be done to have all 5 effects?
No.
Must combine multiple drugs
What other benefits can combinations of general anesthetics provide besides producing all 5 drug responses?
- Reduce dosing requirements, increasing safety
What are the 4 stages of general anesthesia?
1: Analgesia/ Loss of pain
2: Excitement and hyperactivity
3: Surgical Anesthesia
4: Imminent Death/ Paralysis of medulla
What stage of general anesthesia should be patients be in during surgery?
Stage 3
What is manipulated depending on the type of surgery in terms of stages of surgical anesthesia?
Different planes of stage 3
What are the 5 mild adverse effects of gas anesthesia?
- Dizziness
- Drowsiness
- Nausea
- Euphoria
- Vomiting
What are the 3 more severe adverse effects of gas anesthesia?
- Malignant hyperthemia
- Apnea
- Cyanosis
What are the 3 mild adverse effects of volatile liquid anesthesia?
- Drowsiness
- Nausea
- Vomiting
What are the 4 more severe adverse effects of volatile liquid anesthesia?
- Myocardial depression
- Marked hypotension
- Pulmonary vasoconstriction
- Hepatotoxicity
What is the Minimum Alveolar Concentration? What are the 2 units?
- Concentration of drug in gas form at which 50 % of patients do not move during surgery.
- Percent of gas mixture, or percent 760 mmHg pressure
What is the relation of MAC to anesthetic potency?
- MAC is inversely proportional to anesthetic potency
What is the number 1 factor for variation in MAC?
- Age of the patient
What is meant by MAC having a steep dose-response curve?
- Small jump in dosage between the stages of anesthesia
What is the mechanism of action of general anesthetics?
- They are highly lipophilic, which disrupts the membrane lipid bilayer of cells
- Increases threshold to fire
- Also penetrates blood brain barrier
What 3 factors affect MAC?
- Pulmonary ventilation
- Pulmonary blood flow
- Water solubility
How does pulmonary ventilation affect MAC?
The more rapidly air is exchanged, the more rapidly anesthesia is achieved
How does pulmonary blood flow affect MAC?
Faster blood flow through alveoli –> longer it takes for concentration to increase
How does water solubility affect MAC?
More water soluble will mix in watery blood reservoir before sufficient concentrations reach levels capable of inducing unconsciousness. More water soluble –> less potent.
What are the 5 pharamacological effects of general anesthesia?
- Block flow of sodium into neurons
- Enhance inhibitory action of GABA
- Delays impulses and reduces neural activity
- Produces unconsciousness
- Produces lack of responsiveness to painful stimuli
In what type of situations is intravenous anesthesia used?
When short duration anesthesia is required (out patient surgery)
What does intravenous anesthetic typically supplement?
- Inhalation anesthetics
What is administered first; IV or inhalation anesthetics?
- IV
Which type of anesthesia will rapidly induce unconsciousness?
- IV anesthesia
What type of IV anesthetic will have a rapid and potent onset, but without analgesia?
Barbituate
What are 2 barbiturates used for IV anesthesia?
- Thiopental
- Methohexital
What type of IV anesthetic produces sedation, but not analgesia, and will also produce amnesia?
Benzodiazepines
What are 3 examples of benzodiazepines?
- Diazepam
- Lorazepam
- Midazolam
What type of IV anesthetic provides strong analgesia, and is useful for intra-operative pain?
Opioids
What is an example of an Opoid used as an IV anesthetic?
Fentanyl
What type of IV anesthetic is used during procedures in the ICU?
Propofol
What type of IV anesthetic produces good analgesia and delusions, and is rarely used in adults?
Ketamine
** Come back to slide 16 **
** Come back to slide 16 **
What are the 5 techniques for applying local anesthetics?
- Topical
- Nerve block
- Infiltration
- Spinal
- Epidural
What is the effect of local anesthetics?
Rapid loss of sensation in a limited part of the body
How do local anesthetics block sensation?
Stop axonal conduction by blocking sodium channels
What are the 2 types of local anesthetics?
- Amides
- Esters
Why may local anesthetics be contraindicated in patients with cardiovascular conditions?
- Have antiarrhythmic properties
How long does short-acting procaine last?
1 hour
How long does intermediate-acting-lidocaine last?
1 - 2.5 hours
How long does long-acting teracaine last?
3 - 9 hours
Why are vasoconstrictive substances such as norepinephrine co-administered with local anesthetics?
- Limit absorption and concentrate local anesthetics at site of injection
- Also limit bleeding
To what are topical anesthetics applied?
Directly to the skin or mucous membrane
What is the major drug of topical anesthetics? What are the 2 more minor drugs?
Benzocaine is major
Lidocaine and tetracaine are minor
What is the use of a topical anesthetic?
- Relieve or prevent pain from minor burns, irritation, itching
- Also numb area before injection
What type of adverse effects can be expected from topical anesthetics?
- Skin irritation
- Hypersensitivity reactions
What are the 2 types of muscle relaxants?
- Neuromuscular blockers
- Spasmolytics
Which type of muscle relaxant is used to cause paralysis, and as an adjunctive to anesthesia?
Neuromuscular blockers
Which type of muscle relaxant is used to reduce spasticity in a variety of neurologic disorders?
Spasmolytics
What are the 3 indications for neuromuscular junction blockers?
- Surgery
- Muscle spasms from electrically induced convulsions
- Patients fighting mechanical ventilation
What are the 2 types of NMJ blockers?
- Non-depolarizing agents
- Depolarizing agents
What are 4 non-depolarizing NMJ blocker drugs?
- Tubocurarine
- Pancuronium bromide
- Pipecuronium
- Vecuronium
Do NMJ non-depolarizing blockers cross the blood-brain barrier?
No.
Do NMJ blockers affect the CNS?
No.
Is anesthesia induced before or after NMJ blockers are applied?
Before
What type of drug may reverse tubocurarine (a non-depolarizing NMJ blocker)?
- Anticholinesterases
What is the most common depolarizing NMJ blocker?
- Succinylcholine
What is the mechanism of action of succinylcholine?
- Excessive depolarization
- Desensitizes muscles rendering them unresponsive
** See slide 25 **
- See slide 25 **
- Assess the different levels at which the drug may block the endplate
How are tonic stretch reflexes affected in spasticity?
- Increased
Are flexor or extensor muscle spasms caused more commonly in spasticity?
Flexor
Are muscles weaker or stronger in spasticity?
Weaker
What internal systems of motor systems are affected by spasticity?
Reflex arcs
Why are motor neurons hyper excitable in spasticity?
Loss of inhibition from higher centers.
Upper motor neuron lesion
What type of NMJ is used to block spasticity?
Spasmolytics
What are the 4 types of central spasmolytics?
- Carisoprodol
- Baclofen
- Diazepam
- Tizanidine
What central spasmolytic is used to treat acute, painful musculoskeletal conditions due to trauma, inflammation, and anxiety?
Carisoprodol
What central spasmolytic is used for acute and chronic spasticity, especially in patients with spinal cord lesions or cerebral palsy?
Diazepam
What central spasmolytic enhances pre and postsynaptic inhibition in the spinal cord, as well as nociceptive transmission?
Tizanidine
What central spasmolytic is a GABA analog that acts at GABA receptors depressing neuronal activity and frequency and degree of muscle spasms/ tone?
Baclofen
Why is Baclofen the drug of choice?
- Less sedation than diazepam
- Less peripheral muscle weakness than dantrolene
What drug is indicated for patients with spinal cord lesions caused by multiple sclerosis or trauma?
Baclofen
What type of administration is Baclofen given when spasticity/ pain are nonresponsive to medication by other routes of administration?
Intrathecal
What central spasmolytic is vicadin?
Diazepam
What spasmolytic is most effective for spasticity with a cerebral origin, such as MS or CP?
- Dantrolene
Why is dantrolene effective when treating MS or CP?
- It works direction on the muscle
How does Dantrolene work directly on the muscle?
It inhibit calcium release necessary for muscle relaxation
