General and Local Anaesthetic Agents

8/3/2019 General and Local Anaesthetic Agents

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General and Local

Anaesthetics


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Agents that depress the central nervoussystem (CNS)

Depression of consciousness

Loss of responsiveness to sensory stimulation(including pain)

Muscle relaxation

Anesthesia: the state of depressed CNSactivity


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A state of depressed CNS activity

Two types

General anesthesia Local anesthesia

Balanced anaesthesia


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Agents that induce a state in which theCNS is altered to produce varying degreesof:

Pain relief

Depression of consciousness

Skeletal muscle relaxation

Reflex reduction


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Inhaled anesthetics:

Volatile liquids or gases that are vaporized inoxygen and inhaled.

Injectable anesthetics:

Administered intravenously.


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Inhaled gas: Nitrous oxide (laughing gas)

Inhaled volatile liquids: enflurane

halothane

isoflurane

methoxyflurane sevoflurane


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Used:

To induce or maintain general anesthesia

To induce amnesia

As an adjunct to inhalation-type anesthetics


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etomidate

ketamine

methohexital*

propofol* thiamylal

thiopental

* May also be used as adjunctive agents at lower dosages


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Sedative-hypnotics

Barbiturates (secobarbital, thiopental)

Benzodiazepines (diazepam, midazolam)

Opioids (narcotics)

morphine, fentanyl, sufentanil


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Neuromuscular blocking agents (NMBAs):

Depolarizing agents (succinylcholine)

Nondepolarizing agents (pancuronium, d-Tubocurarine, vecuronium)

Anticholinergics:

atropine, glycopyrrolate, scopolamine


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Varies according to agent.

Overall effect:

Orderly and systematic reduction of sensoryand motor CNS functions.

Progressive depression of cerebral and spinalcord functions.


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General anesthetics used during surgicalprocedures to produce:

Unconsciousness

Skeletal muscular relaxation

Visceral smooth muscle relaxation

Rapid onset, quickly metabolized.


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Vary according to dosage and agent used.

Sites primarily affected:

Heart, peripheral circulation, liver, kidneys,respiratory tract.

Myocardial depression is commonly seen.


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Malignant hyperthermia:

Occurs during or after general anesthesia

Sudden elevation in body temperature (>104F)

Life-threatening emergency


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Also called regional anesthetics.

Used to render a specific portion of the

body insensitive to pain.

Interfere with nerve impulse transmissionto specific areas of the body.

Do not cause loss of consciousness.


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Topical:

Applied directly to skin or mucousmembranes.

Creams, solutions, ointments, gels,ophthalmic drops, lozenges, suppositories.

Parenteral:

Injected into the CNS by various spinalinjection techniques.


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Epidural

Infiltration

Nerve block Spinal

Topical


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lidocaine \lignocaine

mepivacaine

procaine tetracaine

bupivacaine

ropivacaine


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First, autonomic activity is lost.

Then pain and other sensory functions arelost.

Motor activity is the last to be lost.

As local agents wear off, they do so in

reverse order (motor, sensory, thenautonomic activity are restored).


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Local anesthetics are used for:

Surgical, dental, and diagnostic procedures

Treatment of certain types of pain

Infiltration anesthesia.

Nerve block anesthesia.


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Infiltration anesthesia:

Minor surgical and dental procedures.

Injection of the anesthetic solution

intradermally, subcutaneously, orsubmucosally across the path of nervessupplying the target area.

May be given in a circular pattern around theoperative area.


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Nerve block anesthesia:

Used for surgical, dental, and diagnosticprocedures.

Also used for therapeutic management ofpain.

The anesthetic agent is injected directly into

or around the nerve trunks or nerve gangliathat supply the area to be numbed.


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Usually limited.

Adverse effects result if:

Inadvertent intravascular injection occurs.

Excessive dose or rate of injection is given.

Slow metabolic breakdown.

Injection into a highly vascular tissue.


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Also known as NMBAs.

Prevent nerve transmission in certainmuscles, resulting in paralysis of themuscle.

Used with anesthetics during surgery.


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When used during surgery, artificialmechanical ventilation is required.

These drugs paralyze respiratory and skeletal

muscles

Patient cannot breathe on his/her own

Do not cause sedation or relief of pain

Patient may be paralyzed yet conscious


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Depolarizing agents

Nondepolarizing agents

Short acting

Intermediate acting

Long acting


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succinylcholine is the only one

Works similarly to neurotransmitteracetylcholine (ACh), causing

depolarization Metabolism is slower than ACh, so as long

as succinylcholine is present,

repolarization cannot occur Result: flaccid muscle paralysis


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Short acting mivacurium

Intermediate acting

atracurium rocuronium

Long acting

pancuronium d-Tubocurarine


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Prevent ACh from acting at theneuromuscular junctions

Nerve cell membrane is not depolarized,muscle fibers are not stimulated

Skeletal muscle contraction does notoccur


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First sensation felt is weakness.

Followed by total flaccid paralysis.

Small, rapidly moving muscles are affected first

(fingers, eyes), then limbs, neck, trunk Finally, intercostal muscles and the diaphragm

are affected, resulting in cessation ofrespirations.

Recovery of muscles usually occurs in reverseorder.


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Main use: maintaining controlledventilation during surgical procedures.

Endotracheal intubation (short acting).

To reduce muscle contraction in an areathat needs surgery.

Diagnostic agents for myasthenia gravis.

Other uses.


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Few when used appropriately.

May cause: Hypotension (blockade of autonomic ganglia)

Tachycardia (blockade of muscarinicreceptors)

Hypotension (release of histamine)

Effects vary according to site.


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Overdose causes prolonged paralysisrequiring prolonged mechanicalventilation.

Cardiovascular collapse may occur.

Several conditions may increase thesensitivity of a patient to NMBAs.


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Combination of an IV benzodiazepine andan opiate analgesic used.

Anxiety and sensitivity to pain are

reduced, and patient cannot recall theprocedure.

Preserves the patients ability to maintain

own airway and to respond to verbalcommands.


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Used for diagnostic procedures and minorsurgical procedures that do not requiredeep anesthesia.

Topical anesthetic may be applied also.

Rapid recovery time and greater safetyprofile than general anesthesia.


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Always assess past history of surgeriesand response to anesthesia.

Assess past history, allergies,medications.

Assess use of alcohol, illicit drugs, opioids.


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Assessment is vital during pre-, intra-, andpostoperative phases

Vital signs

Baseline labwork, ECG

Pulse oximeter (PO2)

ABCs (airway, breathing, circulation)

Monitor all body systems


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Nursing considerations during theperioperative phase include the:

Preoperative phase

Intraoperative phase

Postoperative phase

Each phase has its own complex and very

specific nursing actions


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Close and frequent observation of thepatient and all body systems.

During a procedure, monitor vital signs,ABCs.

Watch for sudden elevations in bodytemperature, which may indicate

malignant hyperthermia.


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During recovery, monitor forcardiovascular depression, respiratorydepression, and complications of

anesthesia.

Implement safety measures duringrecovery, especially if motor/sensory loss

occurs due to local anesthesia.


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Reorient patient to his/her surroundings.

Provide preoperative teaching about thesurgical procedure and anesthesia.

Teach the patient about postoperativeturning, coughing, deep breathing.


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If an NMBA is to be used for a procedurewhen the patient is to be awake, teach thepatient that he/she may be paralyzed but

still able to hear and feel.

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General and Local Anaesthetic Agents