CNS Medications Review

NURS 3340 - Pharmacology: CNS Medications

Overview of CNS Medications and Analgesics

  • CNS drugs and analgesics are crucial in nursing due to:
    • Narrow therapeutic windows: The difference between the minimum effective dose and the minimum toxic dose is small.
    • High potential for respiratory compromise: Many CNS medications can affect respiratory function.
    • High risk of drug interactions: Polymedication leads to potential adverse effects and reduced effectiveness.

Analgesics

  • Definition: Analgesics are medications used to relieve pain without causing loss of consciousness.
  • Mechanism: They decrease pain perception by acting on either the central or peripheral nervous system.
  • Key Points:
    • Used for mild to severe pain.
    • Can act locally (at the site of injury) or centrally (in the brain/spinal cord).
    • Do not treat the underlying cause of pain; they manage the symptom.
    • Necessitate careful assessment of pain levels, timing, effectiveness, and side effects.

1. Non-Opioids

  • Examples:

    • Acetaminophen (Tylenol)
    • Ibuprofen (Advil)
    • Naproxen (Aleve)
    • Aspirin

  • Acetaminophen (Tylenol):

    • Monitoring: Assess liver function through labs (AST, ALT).
    • Dosage: Maximum of 4,000 mg in 24 hours (lower doses for liver disease, malnourished or chronic alcohol users).
    • Toxicity Indicators: Early signs include nausea/vomiting, anorexia, abdominal pain.
    • Antidote: Acetylcysteine (Mucomyst).

  • NSAIDs (Ibuprofen [Advil], Naproxen):

    • Monitoring: Renal function (BUN, Creatinine), gastrointestinal bleeding, blood pressure.
    • Side Effects: Gastrointestinal pain, reflux, GI bleeding, nephrotoxicity.
    • Contraindications: Patients with asthma (risk of bronchospasm), renal failure, or active GI bleed.

2. Opioids

  • Examples:

    • Hydrocodone-acetaminophen (Norco)
    • Codeine (Tylenol #3)
    • Morphine sulfate
    • Fentanyl (known for causing itching & nausea)
    • Hydromorphone (Dilaudid)

  • Key Nursing Assessments:

    • Respiratory Rate: Hold administration if RR < 12.
    • Level of Consciousness (LOC): Monitor for pinpoint pupils (indicative of opioid toxicity) and decreased bowel sounds.
    • Urine Output: Assess for renal perfusion issues.
    • Pain Assessment Pre/Post Administration: Evaluate pain in a timely manner.
    • Concurrent CNS Depressants: Assess for use of alcohol, benzodiazepines, antihistamines.

  • Contraindications: Severe asthma/resipiratory disease, increased intracranial pressure/head injury, paralytic ileus, pregnancy.

    • Antidote: Naloxone (Narcan).
    • Common Side Effects: Nausea.

  • Safety Considerations:

    • Keep narcan available with any opioid order.
    • Rotate patch sites and monitor IV sites.
    • Implement fall precautions and reassess pain promptly.

Anesthetics

1. General Anesthetics

  • Examples:
    • Propofol (Diprivan)
    • Dexmedetomidine (Precedex)
    • Monitoring Requirements:
    • Airway, vital signs, cardiac rhythm, and LOC after procedures.
    • Adverse Effects: Hypotension, dysrhythmias, post-operative confusion.
    • Malignant Hyperthermia:
    • Signs: Muscle rigidity, rapid increased temperature, tachycardia, tachypnea, acidosis.
    • Intervention: Stop anesthetic, provide oxygen, initiate cooling, IV fluids, administer dantrolene if not allergic.
    • Prevention: Screen for family history.

2. Moderate Sedation

  • Definition: Patient is sleepy but easily arousable and maintains airway independently, responding to verbal or light tactile stimuli.
  • Instances of Use:
    • Dental procedures, endoscopy, bronchoscopy.
  • Drug Example:
    • Midazolam (Versed) - used for moderate sedation.
    • Monitor airway, telemetry, respiratory rate, and O2 saturation; have flumazenil available as a reversal agent.

3. Local Anesthetics

  • Definition: Block nerve conduction in a specific area, causing a temporary loss of sensation without affecting consciousness.

  • Mechanism: Blocks sodium (Na+) channels in nerve cells preventing depolarization, thus blocking pain signals.

  • Common Local Anesthetics:

    • Lidocaine (most common - essential for exams)
    • Bupivacaine
    • Procaine
    • Tetracaine

  • Common Uses:

    • Surgical procedures, IV insertions, dental procedures, chest tube placements and regional anesthesia.

  • Important Nursing Considerations:

    • Assess for allergies, especially to -caine drugs (e.g., Bupivacaine).
    • Vasoconstrictors (e.g., Epinephrine): Used to keep drugs localized, prolong duration, decrease bleeding. Conversely, should never be applied to areas with poor circulation due to risk of tissue necrosis (e.g., fingers, toes, nose, ears, penis).

  • Safety Teaching for Patients:

    • Do not engage in activities like chewing or walking until sensation is fully restored; protect the area from extreme temperatures.
    • Report any unusual sensations such as palpitations, dizziness, or unusual numbness.