ANESTHESIA

General Anesthesia

     A. General information
          1. Drug-induced depression of CNS; produces decreased muscle reflex activity and loss of
              consciousness.
          2. Balanced anesthesia: combination of several anesthetic drugs to provide smooth induction,
              appropriate depth and duration of anesthesia, sufficient muscle relaxation, and minimal
              complications.

     B. Stages of general anesthesia: induction, excitement, surgical anesthesia, and danger stage.
     C. Agents for general anesthesia
          1. Inhalation agents
               a. Gas anesthetics
                    1. nitrous oxide: induction agent; component of balanced anesthesia; used alone for
                        short procedures; always given in combination with oxygen
                    2. cyclopropane: obstetric anesthesia; clients with cardiovascular complications; highly
                        flammable and explosive
 

               b. Liquid anesthetics 
                    1. halothane (Fluothane): widely used; rapid induction, low incidence of post-op nausea
                        and vomiting; may cause bradycardia and hypotension; contraindicated in clients with
                        liver disease. 
                    2. enflurane (Ethrane): effects similar to halothane, but muscle relaxation is stronger and
                        hepatotoxicity not a problem; use cautiously in clients with cardiac disease. 
                    3. methoxyflurane (Penthrane): very potent agent with slow onset and recovery;
                        circulatory depression at high concentrations; associated with liver and kidney
                        damage; rarely used. 
                    4. isoflurane (Forane): rapid induction and recovery; potentiates muscle relaxants;
                        causes profound respiratory depression; monitor respirations carefully. 

          2. IV anesthetics: used primarily as induction agents; produce rapid, smooth induction; may be
              used alone in short procedures such as dental extractions. 
               a. Common IV anesthetics: methohexital (Brevital), sodium thiopental (Pentathol) 
               b. Disadvantages: poor relaxation; respiratory and myocardial depression in high doses;
                   bronchospasm, laryngospasm; hypotension, respiratory depression

          3. Dissociative agents: produce state of profound analgesia, amnesia, and lack of awareness
              without loss of consciousness; used alone in short surgical and diagnostic procedures or for
              induction prior to administration of more potent general anesthetics. 
               a. Agent: ketamine (Ketalar) 
               b. Side effects: tachycardia, hypertension, respiratory depression, hallucinations, delirium 
               c. Precautions: decrease verbal, tactile, and visual stimulation during recovery period

          4. Neuroleptics: produce state of neuroleptic analgesia characterized by reduced motor activity,
              decreased anxiety, and analgesia without loss of consciousness; used alone for short
              surgical and diagnostic procedures, as premedication or in combination with other
              anesthetics for longer anesthesia. 
               a. Agent: fentanyl citrate with droperidol (Innovar) 
               b. Side effects: hypotension, bradycardia, respiratory depression, skeletal muscle rigidity,
                   twitching 
               c. Precautions: reduce narcotic doses by 1/2 to 1/3 for at least 8 hours postanesthesia as
                   ordered to prevent respiratory depression.

     D. Adjuncts to general anesthesia: neuromuscular blocking agents: used with general anesthetics
          to enhance skeletal muscle relaxation.

Agents: gallamine (Flaxedil), pancuronium (Pavulon), succinylcholine (Anectine), tubocurarine, atracurium besylate (Tubarine), vecuronium bromide (Norcuron)

Precaution: monitor client's respirations for at least 1 hour after drug's effect has worn off.

TABLE 4.12 Stages of Anesthesia

Stage	From	To	Client Status
Stage I (induction)	Beginning administration of anesthetic agent	Loss of consciousness	May appear euphoric, drowsy, dizzy.
Stage II (delirium or excitement)	Loss of consciousness	Relaxation	Breathing irregular; may appear excited; very susceptible to external stimuli.
Stage III (surgical anesthesia)	Relaxation	Loss of reflexes and depression of vital functions	Regular breathing pattern; corneal reflexes absent; pupillary constriction.
Stage IV (danger stage)	Vital functions depressed	Respiratory arrest; possible cardiac arrest	No respirations; absent or minimal heartbeat; dilated pupils

Regional Anesthesia

General information (see also Table 4.13).

Produces loss of painful sensation in one area of the body; does not produce loss of consciousness.

Uses: biopsies, excision of moles and cysts, endoscopies, surgery on extremities; childbirth

Agents: lidocaine (Xylocaine), procaine (Novocain), tetracaine (Pontocaine)

TABLE 4.13 Regional Anesthesia

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Types	Method
Topical	Cream, spray, drops, or ointment applied externally, directly to area to be anesthetized.
Local infiltration	Injected into subcutaneous tissue of block surgical area
Field block	Area surrounding the surgical site injected with anesthetic.
Nerve block	Injection into a nerve plexus to anesthetize part of body.
Spinal	Anesthetic introduced into subarachnoid space of spinal cord producing anesthesia below level of diaphragm.
Epidural	Anesthetic injected extradurally to produce anesthesia below level of diaphragm; used in obstetrics.
Caudal	Variation of epidural block; produces anesthesia of perineum and occasionally lower abdomen; commonly used in obstetrics.
Saddle block	Similar to spinal, but anesthetized area is more limited; commonly used in obstetrics.

 

      a. Circulating nurse
      b. Others – med tech, rad tech, transport aides