Anesthesia

ANESTHESIA

UNIT 4 OBJECTIVES: ANESTHESIA

  • Differentiate Between Local Anesthetics and General Anesthetics
    • Reference to Example Drugs, Uses, Pharmacokinetics, Pharmacodynamics, and Nursing Implications (SLO 1)
  • Develop a Nursing Care Plan
    • For a Patient Receiving Anesthetic Agents, with an Emphasis on Post-Anesthesia Care (SLO 4)
  • Develop a Patient Education Plan
    • For a Patient Receiving Anesthetic Agents (SLO 3)

ANESTHESIA DEFINED

  • Definition: Anesthesia is a drug-induced state whereby the central nervous system is altered to produce varying degrees of:
    • Pain relief
    • Loss of sensation
    • Depression of consciousness
    • Skeletal muscle relaxation
    • Diminished or absent reflexes.

ANESTHESIA TYPES

  • Two Primary Types:
    1. General Anesthesia
    • Global state of anesthesia affecting the whole body.
    • Can produce a loss of consciousness.
    1. Local/Regional Anesthesia
    • Specific portion of the body becomes insensitive to sensations without affecting consciousness.

ANESTHETIC AGENTS

  • General Anesthetics:
    • Intravenous:
    • Inhalation:
  • Local Anesthetics:
    • Infiltration:
    • Peripheral Nerve Block (Specific Nerve Path):
    • Regional Block (Area of the Body):
    • Spinal:
    • Epidural:
    • Topical:

STAGES OF ANESTHESIA

Stage 1: Induction to Loss of Consciousness
  • Primary effect is analgesia and relaxation.
  • Spontaneous but slow respirations.
Stage 2: Loss of Consciousness until Point of Automatic Reflex Breathing
  • Primary effects include:
    • Delirium
    • Muscle hyperexcitability
    • Possibly incontinence and vomiting
  • Breathing and heart rate may be irregular.
Stage 3: Begins with Onset of Reflex Breathing
  • Extends until apnea (absence of breathing) and diaphragmatic paralysis.
  • Primary effect is complete muscle relaxation.
  • Must have artificial airway/breathing.
  • Known as the surgical stage.
Stage 4: Overdose
  • Begins with respiratory paralysis and extends to death.
  • Initially reversible, but there is a narrow window of opportunity for reversal.

GENERAL EFFECTS OF ANESTHESIA

  • Common Effects Include:
    • Respiratory depression
    • Cardiovascular depression
    • Skeletal muscle relaxation
    • Central nervous system (CNS) depression
    • Decreased renal and gastrointestinal (GI) function.

INTRAVENOUS MEDICATIONS

  • Most commonly used for rapid or initial induction or when only “light” anesthesia/conscious sedation is needed.
  • Not good for maintenance due to high doses required to achieve surgical anesthesia.
  • Drugs have rapid onset and most have a short duration.

EXAMPLES OF IV ANESTHETIC MEDICATIONS

  • Benzodiazepines:
    • Midazolam (Versed)
    • Diazepam (Valium)
    • Lorazepam (Ativan)
  • Opiates:
    • Fentanyl
    • Morphine
    • Meperidine (rarely used)
  • Barbiturates:
    • Phenobarbital
    • Secobarbital
  • Hypnotic:
    • Etomidate
  • Anesthetic:
    • Propofol (Diprivan)
    • Very strict aseptic technique is needed for this medication.
    • Used primarily for patients on mechanical ventilation (including the ED/ICU).
    • Short half-life allows easy management of sedation.

NEUROMUSCULAR BLOCKING AGENTS

  • Primary Uses:
    • Facilitate intubation or promote skeletal muscle relaxation.
    • Rapid onset (usually less than 1-2 minutes).
NEUROMUSCULAR BLOCKING AGENT CATEGORIES
  1. Depolarizing:
    • Example: Succinylcholine
    • Genetic predisposition to difficulty metabolizing.
    • Side effect of possible malignant hyperthermia when used with general anesthetics.
  2. Non-Depolarizing:
    • Examples:
      • Rocuronium
      • Vecuronium
      • Pancuronium
      • Tubocurarine and others
    • Can be reversed with an anticholinesterase agent such as Neostigmine, which increases acetylcholine at the receptor site, leading to muscle contraction.

GENERAL ANESTHETICS (INHALATION)

  • Used for maintenance during surgery, allows easier maintenance of desired level by adjusting flow rates and concentration of anesthesia and oxygen.
  • Minimal muscle relaxant effect unless very deep anesthesia is achieved.
  • Adverse Effects:
    • Excessive sedation
    • Cardiopulmonary depression
    • Halothane is hepatotoxic and proarrhythmic (causes abnormal heartbeat).
    • Risk of malignant hyperthermia in genetically predisposed individuals.

INHALATION ANESTHETIC MEDICATIONS

  • Drugs that include “ane”:
    • Halothane (Fluthane)
    • Enflurane (Ethrane)
    • Isoflurane (Florane)
  • All are volatile liquids.
  • Nitrous Oxide (“Laughing Gas”):
    • When used alone induces Stage 2 anesthesia, however, it has a higher analgesic effect than other agents.

NURSING CONSIDERATIONS

  • Frequent assessment of vital signs (VS), level of consciousness (LOC), and oxygen saturation (O2 sats) during and after surgery.
  • Post-operatively assess for bladder and bowel function, respiratory status, and encourage turn/cough/deep breathing (TCDB) and ambulation as soon as ordered and possible.
  • Monitor for signs of malignant hyperthermia.

MALIGNANT HYPERTHERMIA

  • Description: Malignant hyperthermia is an uncommon but potentially fatal adverse reaction.
  • Signs & Symptoms:
    • Rapid rise in body temperature (severe elevation)
    • Tachycardia
    • Tachypnea
    • Muscle rigidity
  • Believed to be genetically linked.
TREATMENT
  • Medication: Dantrolene.

MONITORED ANESTHESIA CARE/CONSCIOUS SEDATION

  • Usually for planned procedures but may also be used in emergency departments or critical care areas.
  • Combination of local anesthesia along with sedation and analgesics.
  • Aims to provide sedation, reduction of pain, and anxiety.
  • Patient's Condition: Patient should be able to answer questions and protect their own airway.

CONSCIOUS SEDATION

  • Also referred to as “twilight sleep.”
  • Minimally depresses the level of consciousness while allowing the patient to maintain their own airway independently.
  • Primary Goal: Reduce anxiety and discomfort while facilitating cooperation.
  • Useful for diagnostics and minor surgical procedures (e.g., endoscopy or bronchoscopy).
CONTINUED CONSCIOUS SEDATION
  • Light Sedation: Uses Ramsay Scale Levels 2-4, meaning patients are able to respond to commands but easily drift back to sleep when not stimulated.
  • Depending on medications used, many patients exhibit an amnesic effect, resulting in little or no recollection of the procedure.
  • Rapid recovery (30-90 minutes) occurs once medications are discontinued.
  • Side Effects:
    • Excessive sedation
    • Bradycardia
    • Respiratory depression.

RAMSAY SCALE FOR ASSESSING SEDATION

  • Level 1: Anxious, agitated, restless.
  • Level 2: Cooperative, oriented, tranquil.
  • Level 3: Responds to commands only.
  • Level 4: Asleep but will respond to loud auditory or painful stimuli.
  • Level 5: Asleep with only sluggish response to stimuli.
  • Level 6: No response.

NURSING CONSIDERATIONS

  • Frequent assessment of vital signs (VS), level of consciousness (LOC), and oxygen saturation (O2 sats).
  • Continuous monitoring during and assessments every 5-15 minutes afterwards for the first 1-2 hours.
  • Have antidotes ready in case of excessive sedation:
    • Opiate medications: Naloxone
    • Benzos: Flumazenil.

DISSOCIATIVE ANESTHESIA

  • Interrupts brain pathways and blocks sensory pathways without significant motor effects.
  • Useful for analgesia and amnesia without muscle relaxations (e.g., major burn dressing changes).
  • Primary Drug: Ketamine.
  • Caution: May produce psychological reactions such as hallucinations and delirium.

ADJUNCTS TO ANESTHESIA

  • Medications Used to Enhance Effects:
    • Opiates
    • Benzodiazepines (sedatives and hypnotics)
    • Neuromuscular blocking agents
  • Counteracting Undesirable Effects:
    • Anticholinergics: Dry up secretions to prevent aspiration and decrease nausea.
    • Antiemetics: Decrease nausea.

LOCAL ANESTHESIA

  • Affects autonomic, sensory, and motor fibers in order, with recovery occurring in the reverse order.
  • Techniques Include:
    • Infiltration (direct to the area to be desensitized)
    • Nerve block/regional injection into a nerve or nerve bundle affecting tissues or structures in that designated region.
CONTINUED LOCAL ANESTHESIA
  • Spinal Anesthesia: Injected into the cerebrospinal fluid (CSF) in the subarachnoid space, inducing paralysis below the area.
  • Epidural Anesthesia: Injection into the epidural space (not into CSF).
    • Can be done as a single injection or through a catheter inserted for sustained control of pain.
    • Popular in obstetrics.
  • Topical Anesthesia: Applied directly to the skin or mucous membranes (e.g., eye drops, anesthetic creams or ointments).

MEDICATIONS FOR LOCAL ANESTHESIA

  • Family: All end with “caines” (important: differentiate from “anes” which refer to inhaled general anesthetics).
    • Lidocaine (Xylocaine): Most common, used for injections or topical, including throat spray.
    • Cocaine: Used only for ear/nose/throat (ENT) procedures as a topical because, unlike others, it causes significant vasoconstriction.
    • Procaine (Novocaine): Primarily used by dentists.
    • Benzocaine: Mostly topical.
    • Others include Bupivacaine, Tetracaine, etc.

NURSING CONSIDERATIONS FOR LOCAL ANESTHESIA

  • Assessment Considerations:
    • Allergies (before and after administration)
    • Vital signs
    • Neuromuscular status
    • Headache (common side effect of spinal/epidural anesthesia).
    • Protect from injury until fully recovered from effects.
    • For spinal procedures, monitor bowel and bladder function.