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I. Definition of termsA. Anesthesia loss of the ability to feel pain, resulting from the administration of

an anesthetic drug or other medical intervention.

B. Anesthetics drug that depress the central nervous system (CNS) to producediminution of consciousness, loss of responsiveness to sensory stimulation, ormuscle relaxation.

C. Balanced Anesthesia the practice of using combinations of drugs rather toproduce a single drug to produce anesthesia. A common combination is a

mixture of a sedative-hypnotic, an antianxiety drug, an analgesic, an antiemetic,

and an anticholinergic.

D. General Anesthesia a drug induced state in which the CNS is altered to producea varying degrees of pain relief throughout the body as well as depression of

consciousness, skeletal muscle relaxation, and diminished or absent reflexes. It is

most commonly induces for performance of surgical procedure.E. General Anesthetic a drug tat induces a state of anesthesia. Its effects are

global in that they involve the whole body, with loss of consciousness being one

of those effects.

F. Local Anesthetics drugs that render a specific portion of the body insensitive topain at the level of the peripheral nervous system, normally without affecting

consciousness. Also call regional anesthetic.

G. Parenteral Anesthesia any anesthetic drugs that can be administered byinjection via any route (e.g., intravenously, spinally/epidurally, as a local nerve

block). Depending on the specific site of injection the drug may anesthetize all or

parts of the central or peripheral nervous system or both.

H. Topical Anesthesia a class of local anesthesia that are applied directly to theskin and mucous membranes. They consist of solutions, ointments, gels, creams,

powders, ophthalmic drops, and suppositories.

II. Types of Anesthesia:There are many mechanisms by which anesthetics accomplish these responses, but in

general they do so by interfering with nerve conduction. Anesthetics are most commonlyclassified as either general anesthetics or local anesthetics, depending on where in the CNS or

PNS the particular anesthetic drug works. Functions of the autonomic nervous system, which is

a branch of the PNS, may also be affected.

A.General Anesthesia

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Advantages of general anesthesia include rapid excretion of the anesthetic agent and

prompt reversal of its effects when desired. Additionally, general anesthesia can be used with

all age groups and any type of surgical procedure. It produces amnesia.

Disadvantages of general anesthesia include risk associated with circulatory, respiratory,

hepatic and renal side effects. Clients with serious respiratory or circulatory diseases, such as

emphysema or congestive heart failure, are at greater risk for complications. Clients with renaland hepatic disease cannot metabolize and eliminate anesthetics effectively.

o Two Main Categories:Inhaled anesthetics are volatile liquids or gases that are vaporized in oxygen and

inhaled to induce anesthesia through a mask or through an endotracheal tube inserted

in the trachea. E.g. nitrous oxide laughing gas and isoflurane (Forane) is an inhaled

volatile liquid.

Injectable anesthetics - are administered intravenously. These drugs are used for

induction or maintenance of general anesthesia, inducing amnesia, and as an adjunct to

inhalation-type anesthetics. Common intravenous anesthetic drugs include general

anesthetics such as ketamine (Ketalar) and barbiturates such as thiopthal.

o Mechanisms of Action ad Drug EffectsThe overall effect of general anesthetics is an orderly and systematic reduction of

sensory and motor CNS functions. They produce a progressive depression of the cerebral and

spinal cord functions. Therapeutic (anesthetics) does cause minimal depression of the

medullary centers that govern vital functions.

o IndicationsGeneral anesthetics are used to produce unconsciousness, skeletal muscular relaxation,

and visceral smooth muscle relaxation for surgical procedures.

o Contraindications Adverse EffectsContraindications to use of anesthetic drugs include known drug allergy and, depending

on the drug type, may include pregnancy, narrow-angle glaucoma, and known susceptibility to

malignant hyperthermia from prior experience with anesthetics.

B.Regional/Local AnesthesiaLocal anesthetics are also called regional anesthetics because they render a specific

portion of the body insensitive to pain without major reduction of CNS functions and level of

consciousness. They do this by interfering with the nerve transmission in specific area of the

body, blocking nerve conduction only in the area in which they are applied without causing loss

of consciousness. They are most commonly used in those clinical setting in which loss of

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consciousness, whole body relaxation, and loss of responsiveness are either undesirable or

unnecessary. Other uses for local anesthesia include dental procedures, the suturing of skin

lacerations, spinal anesthesia, and diagnostic procedures such as lumbar puncture or

thoracentesis.

o Types of Local Anesthesia Central - Spinal or intraspinal analgesia: anesthetic drugs are injected into the area

near the spinal cord within the vertebral column. Intraspinal anesthesia is commonly

accomplished by one or two injection techniques:

Intrathecal anesthesia involves injection of anesthetic into the subarachnoid space.

Intrathecal anesthesia is commonly used for patients undergoing major abdominal or

limb surgery for whom the risk of general anesthesia are too high or patient who prefer

this technique instead of complete loss of consciousness during their surgical procedure.

More recently, intrathecal injection of anesthetics through implantable drug pumps is

even being used on an outpatient basis in patients with severe chronic pain symdromes.Epidural anesthesia involves injection of anesthetics via a small catheter into the

epidural space without puncturing the dura. Epidural anesthesia is commonly used to

reduce maternal discomfort during labor and delivery and to manage postoperative pain

management after a major abdominal or pelvic surgery. The route is becoming popular

for the administration of opioids for pain management.

PeripheralInfiltration: small amount of anesthetic solution are injected into this tissue that

surrounds the operative site. This approach to anesthesia is commonly used for suchprocedures as wound suturing and dental surgery. Often drugs that cause constriction of

local blood vessels (e.g. epinephrine, cocaine) are also administered to limit the site of

action of the local area.

Nerve Block: anesthetic solution is injected at the site where a nerve innervates a

specific area such as a tissue. This allows large amount of anesthetic drug to be

delivered to a very specific area without affecting the whole body. This method is often

reserved for more difficult-to-treat pain syndromes such as cancer pain and chronic

orthopedic pain.

Intravenous Block (Bier block): is used most often for procedures involving the arm,wrist, and hand. An occlusion tourniquet is applied to the extremity to prevent

infiltration and absorption of the injected intravenous agent beyond the involved

extremity.

Topical Anesthesia: the anesthetic drug is applied directly onto the surface of the skin,

eye or any other mucous membrane to relieve pain or prevent it from being sensed. It is

commonly used for diagnostic eye examinations and skin suturing.

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o Mechanisms of ActionLocal anesthetics block both the generation and conduction of impulses through all

types of nerve fibers (sensory, motor, and autonomic) by blocking the movement of certain ions

(sodium, potassium, and calcium) important to this process. They do this by making it movedifficult for these ions to move in and out of the nerve fiber. In terms of paralysis, usually

autonomic activity is affected first, and then pain and other sensory functions are lost. Motor

activity is the last to be lost. When the effects of the local anesthesia wear off, recovery occurs

in reverse order: motor activity returns first, then sensory, and finally autonomic activity.

o IndicationsLocal anesthetics are used for surgical, dental, or diagnostic procedures, as well for the

treatment of various types of chronic pain. Infiltration anesthesia is commonly used for minor

surgical and dental procedures. It involves injection of the local anesthetic solution by ID, SQ or

IM routes and across the path of nerves supplying the area to be anesthetized. The local

anesthesia may be administered in a circular pattern around the operative field. Nerve block

anesthesia is used for surgical, dental, and diagnostic procedures and for the therapeutic

management of chronic pain. It involves the injection of the local anesthetic directly into or

around the nerve trunks or nerve ganglia that supply the area to be numbed.

o ContraindicationsContraindications for local anesthesia include known drug allergy. Only specially

designed dosage forms are intended for ophthalmic use.

C. Conscious SedationAn increasing number of surgical and diagnostic procedure are being performed using

conscious sedation. This type of anesthesia provides analgesia, amnesia, and moderate

sedation. The pharmacologic effects are produced by administering a combination of

intravenous medications with opioids (such as morphine sulfate, meperidine hydrochloride

[Demorol], and fentanyl [Sublimaze]) or sedatives (such as diazepam [Valium] and midazolam

[Versed]). During conscious sedation the client is able to independently maintain an open

airway. This allows the client to respond to verbal and physical stimulation. Physician

supervision is always required and registered nurse must be prepared to initiate rescue if

sedation becomes too deep.Conscious sedation increases the clients pain threshold and includes degree amnesia

but allows for prompt reversal of its effects and a rapid return to normal activities if daily living.

Procedures such as endoscopes, incision and drainage of abscesses, and even balloon

angioplasty maybe performed under conscious sedation.