Module 2-3 Anesthetic drugs Flashcards
Anesthetics
Drugs that depress the central nervous system (CNS) Depression of consciousness Loss of responsiveness to sensory stimulation (including pain) Muscle relaxation
Anesthesia
A state of depressed CNS activity Two types General anesthesia Local anesthesia Balanced anesthesia
General Anesthetics
Drugs that induce a state in which the CNS is altered to produce varying degrees of: analgesia Depression of consciousness Skeletal muscle relaxation Reflex reduction
General Anesthetics (cont’d)
Inhaled anesthetics Volatile liquids or gases that are vaporized/mixed in oxygen and inhaled Parenteral anesthetics Administered intravenously
Inhaled Anesthetics
Inhaled gas nitrous oxide Inhaled volatile liquids desflurane enflurane (Ethrane) halothane (Fluothane) isoflurane (Forane) methoxyflurane (Penthrane) sevoflurane
Injectable Anesthetics
Used:
To induce or maintain general anesthesia
To induce amnesia
As an adjunct to inhalation-type anesthetics
Injectable Anesthetics (cont’d)
etomidate (Amidate) ketamine (Ketalar) methohexital (Brevital)* propofol (Diprivan)* thiamylal (Surital) thiopental (Pentothal)*
Adjunct Drugs
Sedative-hypnotics
Barbiturates (pentobarbital, secobarbital)
Benzodiazepines (diazepam, midazolam)
hydroxyzine
promethazine
Opioid Analgesics
fentanyl, sufentanil, meperedine, morphine
Adjunct Drugs (cont’d)
Neuromuscular blocking drugs (NMBDs) Depolarizing drugs (succinylcholine) Nondepolarizing drugs (pancuronium pancuronium, d-tubocurarine, vecuronium) Anticholinergics atropine, glycopyrrolate, scopolamine
Mechanism of Action
Varies according to drug
Overton-Meyer theory
Overall effect
Orderly and systematic reduction of sensory and
motor CNS functions
Progressive depression of cerebral and spinal
cord functions
Indications
General anesthetics used during surgical procedures to produce: Unconsciousness Skeletal muscular relaxation Visceral smooth muscle relaxation Rapid onset; quickly metabolized Also used in electroconvulsive therapy treatments for depression
Adverse Effects
Vary according to dosage and drug used Sites primarily affected Heart, peripheral circulation, liver, kidneys, respiratory tract Myocardial depression is commonly seen
Adverse Effects (cont’d)
Malignant hyperthermia
Occurs during or after general anesthesia or use
of the NMBD succinylcholine
Sudden elevation in body temperature (greater
than 104° F)
Tachypnea, tachycardia, muscle rigidity
Life-threatening emergency
Treated with dantrolene (skeletal muscle relaxant)
Moderate Sedation
Also called conscious sedation, procedural
sedation
Combination of an IV benzodiazepine and an opiate analgesic
Anxiety and sensitivity to pain are reduced,
and patient cannot recall the procedure
Preserves the patient’s ability to maintain own airway and to respond to verbal commands
Moderate Sedation (cont’d)
Used for diagnostic procedures and minor
surgical procedures that do not require deep
anesthesia
Topical anesthetic may be applied also
Rapid recovery time and greater safety profile than general anesthesia
Local Anesthetics
Also called regional anesthetics
Used to render a specific portion of the body
insensitive to pain
Interfere with nerve impulse transmission to
specific areas of the body
Do not cause loss of consciousness
Local Anesthetics (cont’d)
Topical
Applied directly to skin or mucous membranes
Creams, solutions, ointments, gels, ophthalmic
drops lozenges suppositories
drops, lozenges,
Parenteral Injected parenterally or into the CNS by various spinal injection techniques
Types of Local Anesthesia
Spinal or intraspinal Intrathecal Epidural Infiltration Nerve block Topical
Parenteral Anesthetics
procaine (Novocain) tetracaine (Pontocaine) lidocaine (Xylocaine) mepivacaine (Carbocaine) bupivacaine
Drug Effects: Paralysis
First, autonomic activity is lost
Then pain and other sensory functions are
lost Last, motor activity is lost
As local drugs wear off, recovery occurs in
reverse order (motor, sensory, then
autonomic activity are restored)
Indications
Local anesthetics are used for:
Surgical, dental, and diagnostic procedures
Treatment of certain types of chronic pain
Spinal anesthesia: to control pain during surgical
procedures and childbirth
Local anesthetics are given by:
Infiltration anesthesia
Nerve block anesthesia
Indications (cont’d)
Infiltration anesthesia
Minor surgical and dental procedures
Injection of the anesthetic solution intradermally,
subcutaneously or submucosally across the path
subcutaneously, of nerves supplying the target area
May be given in a circular pattern around the operative area
Indications (cont’d)
Infiltration anesthesia and epinephrine
Some local anesthetics used for infiltration or
nerve block are combined with vasoconstrictors
• To prevent systemic absorption of anesthetic
• To help confine local anesthetic to injected area
• To reduce local blood loss during procedure
• Epinephrine, phenylephrine, norepinephrine
Indications (cont’d)
Nerve block anesthesia
Used for surgical, dental, and diagnostic
procedures
Also used for therapeutic management of pain
The anesthetic drug is injected directly into or around the nerve trunks or nerve ganglia that
supply the area to be numbed
Adverse Effects
Usually limited
Adverse effects result if:
Inadvertent intravascular injection occurs
Excessive dose or rate of injection is given
Slow metabolic breakdown occurs
Injection into highly vascular tissue occurs
“Spinal headache,” treated with an epidural blood patch
Neuromuscular Blocking Drugs
Also known as NMBDs
Prevent nerve transmission in certain
muscles, resulting in muscle paralysis
Used with anesthetics during surgery
Neuromuscular Blocking Drugs (cont’d
When used during surgery, artificial
mechanical ventilation is required
These drugs paralyze respiratory and skeletal
muscles
Patient cannot breathe on his or her own
Do not cause sedation or pain relief
Patient may be paralyzed yet conscious
Neuromuscular Blocking Drugs (cont’d
Depolarizing drugs Nondepolarizing drugs Short acting Intermediate acting Long acting
NMBAs: Depolarizing Drug
Succinylcholine
Works similarly to neurotransmitter acetylcholine
(Ach), causing depolarization
Metabolism is slower than Ach so as long as
Ach, succinylcholine is present, repolarization cannot
occur
Result: flaccid muscle paralysis
NMBAs: Nondepolarizing Drugs
Short acting mivacurium (Mivacron) Intermediate acting atracurium Tracrium), vecuronium Norcuron) rocuronium (Zemuron) Long acting pancuronium (Pavulon), doxacurium (Nuromax) d-tubocurarine
Nondepolarizing NMBAs
Prevent Ach from acting at neuromuscular
junctions
Muscle fibers are not stimulated
Skeletal muscle contraction does not occur
Neuromuscular Blocking Drugs
First sensation is muscle weakness
Followed by total flaccid paralysis
Small, rapidly moving muscles affected first (fingers,
eyes) then limbs neck trunk
eyes), limbs, neck, Finally, intercostal muscles and diaphragm affected,
resulting in cessation of respirations
Recovery of muscular activity usually occurs in reverse order
Transient muscle fasciculations may result in later
muscle soreness
NMBAs:
Indications
Main use: maintaining controlled ventilation
during surgical procedures
Endotracheal intubation (short acting)
To reduce muscle contraction in an area that needs surgery
NMBAs:
Adverse Effects
Few when used appropriately
May cause:
Hypotension (blockade of autonomic gangli
Tachycardia (blockade of muscarinic receptors)
Hypotension (release of histamine)
NMBDs: Safety
Respiratory muscle paralysis occurs with
these drugs
Emergency ventilation equipment must be
immediately available
NMBDs: Overdose
Overdose causes prolonged paralysis
requiring prolonged mechanical ventilation
Cardiovascular collapse may occur
