Chapter 12- General and Local Anesthetics 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 of anesthesia
- General anesthesia
* Local anesthesia
General Anesthetics
- Drugs that induce a state in which the CNS is altered to produce verying degress of:
- analgesia
- depression of consciousness
- skeletal muscle relaxation
- reflex reduction
General Anesthetics: Inhaled anesthetics
Volatile liquids or gases that are vaporized/mixed in oxygen and inhaled
General Anesthetics: 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:
- etomidate (Amidate)
- ketamine (Ketalar)
- methohexital (Brevital)
- propofol (Diprivan)
- thiamylal (Surital)
- thiopental (Pentothal)
Sedative-hypnotics
- Barbiturates (pentobarbital, secobarbital)
- Benzodiazepines (diazepam, midazolam)
- hydroxyzine
- promethazine
Opioid Analgesics
fentanyl, sufentanil, meperedine, morphine
Neuromuscular blocking drugs (NMBDs)
- depolarizing drugs (succinylcholine)
- nondepolarizing drugs (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
- 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: Malignant Hyperthermia
- occurs during or after general anesthesia or use of the NMBD succinylcholine
- sudden elevation in body temperature (greater that 104)
- 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 patients ability to maintain own airway and to respond to verbal commands
Moderate Sedation also 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: Topical
- Applied directly to skin or mucous membranes
- creams, solutions, ointments, gels, ophthalmic drops, lozenges, suppositores
Local Anesthetics: 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
Infilitration anesthesia
- Minor surgical and dental procedures
- injection of the anesthetic solution intradermally, subcutaneously, or submucosally across the path of nerves supplying the target area
- May be given in a circular pattern around the operative area
Infilitration 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
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
- “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: When used during surgery
Artificial mechanical ventilation is required -these drugs paralyze respiratory and skeletal muscles -patient cannot breathe on is or her own -do not cause sedation or pain relief -patient may be paralyzed yet conscious -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 succinylcholine is present, repolarizing 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
Nodepolarizing 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
- finally, intercostal muscles and diaphragm affected,
