Emergency Drugs for Sedated Patients (AAPD Guidelines)

In the context of pediatric dentistry and sedation, it is crucial to be prepared for potential emergencies that may arise during or after sedation. The following is a list of emergency drugs that may be needed to rescue a sedated patient, along with their indications and uses.

Emergency Drugs

1. Albuterol for Inhalation

   • Indication: Bronchospasm or asthma exacerbation.
   • Use: Administered via nebulizer or metered-dose inhaler to relieve bronchospasm.

2. Ammonia Spirits

   • Indication: Syncope or fainting.
   • Use: Inhaled to stimulate respiration and increase alertness.

3. Atropine

   • Indication: Bradycardia or asystole.
   • Use: Increases heart rate by blocking vagal effects on the heart.

4. Diazepam

   • Indication: Seizures or severe anxiety.
   • Use: Administered intravenously or intramuscularly for rapid sedation or seizure control.

5. Diphenhydramine

   • Indication: Allergic reactions or anaphylaxis.
   • Use: Antihistamine for allergic symptoms; may also be used for sedation.

6. Epinephrine (1:1,000 and 1:10,000)

   • Indication: Anaphylaxis or severe asthma attack.
   • Use: 1:1,000 for intramuscular injection; 1:10,000 for intravenous administration in cardiac arrest.

7. Flumazenil

   • Indication: Benzodiazepine overdose.
   • Use: Reversal agent for sedation caused by benzodiazepines.

8. Fosphenytoin

   • Indication: Status epilepticus.
   • Use: Anticonvulsant for seizure control, administered intravenously.

9. Glucose (25% or 50%)

   • Indication: Hypoglycemia.
   • Use: Administered intravenously to rapidly increase blood glucose levels.

10. Lidocaine

    • Indication: Cardiac arrhythmias or local anesthesia.
    • Use: Antiarrhythmic agent for ventricular arrhythmias; also used for local anesthesia.

11. Lorazepam

    • Indication: Anxiety or seizures.
    • Use: Sedative and anticonvulsant, administered intravenously or intramuscularly.

12. Methylprednisolone

    • Indication: Severe allergic reactions or inflammation.
    • Use: Corticosteroid for reducing inflammation and managing allergic reactions.

13. Naloxone

    • Indication: Opioid overdose.
    • Use: Opioid antagonist to reverse respiratory depression and sedation caused by opioids.

14. Oxygen

    • Indication: Hypoxia or respiratory distress.
    • Use: Administered to improve oxygen saturation and support respiratory function.

15. Racemic Epinephrine

    • Indication: Croup or severe bronchospasm.
    • Use: Administered via nebulization to reduce airway swelling and improve breathing.

16. Rocuronium

    • Indication: Neuromuscular blockade for intubation.
    • Use: Non-depolarizing neuromuscular blocker for facilitating intubation.

17. Sodium Bicarbonate

    • Indication: Metabolic acidosis or hyperkalemia.
    • Use: Administered intravenously to correct acidosis and manage elevated potassium levels.

18. Succinylcholine

    • Indication: Rapid sequence intubation.
    • Use: Depolarizing neuromuscular blocker for quick intubation.

Pharmacodynamics of Nitrous Oxide

Overview

Nitrous oxide (N2O), commonly known as "laughing gas," is an inhalational anesthetic used primarily for its analgesic and anxiolytic properties. Understanding its pharmacodynamics is crucial for safe and effective use in clinical settings.

Pharmacodynamics

1. CNS Depression:

   • Nitrous oxide produces nonspecific central nervous system (CNS) depression.
   • While it is classified as an inhalational general anesthetic, it provides limited analgesia, making surgical anesthesia unlikely unless concentrations that produce anoxia are reached.

2. Potency:

   • Nitrous oxide is the weakest of all inhalation agents, with a minimum alveolar concentration (MAC) of approximately 105%.
   • The MAC is a measure of the potency of an inhalation agent, defined as the concentration required to produce immobility in 50% of patients in response to a surgical stimulus.

3. Effects at Various Concentrations:

   • 30% to 50% Concentration:
     • Produces a relaxed, somnolent patient who may appear dissociated and is easily susceptible to suggestion.
     • Some patients may experience amnesia, but there is typically little alteration in learning or memory.
   • Greater than 60% Concentration:
     • Patients may experience discoordination, ataxia, giddiness, and increased sleepiness.
     • It is recommended that the concentration of nitrous oxide should not routinely exceed 50% to avoid adverse effects.

4. Titration:

   • One of the advantages of nitrous oxide is its ability to be easily titrated.
   • It can be increased for stimulating procedures (e.g., injections) and decreased during less stimulating periods (e.g., restorations).

Physiological Considerations

1. Entrapment in Gas-Filled Spaces:

   • Nitrous oxide can become entrapped in gas-filled spaces such as the middle ear, sinuses, and gastrointestinal tract.
   • This can lead to increased middle ear pressure, which is generally insignificant in patients with normal Eustachian tube function but can induce pain in patients with acute otitis media.

2. Contraindications:

   • Acute Otitis Media: Use should be avoided in patients with this condition due to the risk of increased middle ear pressure and pain.
   • Severe Behavioral Problems and Emotional Illness: Patients who are uncooperative or have a fear of "gas" may not tolerate nitrous oxide well.
   • Claustrophobia: Patients with this condition may feel uncomfortable with the nasal hood placement.
   • Maxillofacial Deformities: Conditions that prevent proper placement of the nasal hood can contraindicate its use.
   • Nasal Obstruction: Conditions such as upper respiratory infections, nasal polyps, or a deviated septum can hinder effective administration.
   • Chronic Obstructive Pulmonary Disease (COPD): Patients with COPD may have difficulty with nitrous oxide due to respiratory issues.
   • Pregnancy: Caution is advised when using nitrous oxide in pregnant patients.
   • High Oxygenation Situations: Situations where high oxygenation is inadvisable, such as during Bleomycin therapy, contraindicate the use of nitrous oxide.

Intravenous Anesthetic Agents

Intravenous anesthetic agents are crucial in modern anesthesia practice, providing rapid onset of sedation and analgesia. This lecture will cover the most commonly used intravenous anesthetic agents, including their indications, contraindications, and required doses.

1. Benzodiazepines

Overview

Benzodiazepines are primarily used for their anxiolytic (anxiety-reducing) and amnesic properties. They are frequently used in procedural sedation and as adjuncts in general anesthesia.

Common Agents

• Diazepam

  • Dose: 5-10 mg IV (may repeat every 5-15 minutes as needed)
  • Indications: Anxiety, sedation, muscle relaxation, seizure control.
  • Contraindications: Hypersensitivity, severe respiratory depression, acute narrow-angle glaucoma.

• Lorazepam

  • Dose: 1-4 mg IV (may repeat every 6-8 hours as needed)
  • Indications: Anxiety, sedation, preoperative medication.
  • Contraindications: Hypersensitivity, severe respiratory depression, acute narrow-angle glaucoma.

• Midazolam

  • Dose: 1-5 mg IV (may repeat every 2-5 minutes as needed)
  • Indications: Procedural sedation, induction of anesthesia, anxiety reduction.
  • Contraindications: Hypersensitivity, severe respiratory depression, acute narrow-angle glaucoma.

2. Etomidate

Overview

Etomidate is an imidazole derivative used for rapid intravenous induction of anesthesia. It is known for its minimal cardiovascular effects.

Dose

• Dose: 0.2-0.3 mg/kg IV (administered over 30-60 seconds)

Indications

• Induction of anesthesia, particularly in patients with cardiovascular instability.

Contraindications

• Hypersensitivity to etomidate, adrenal insufficiency (due to suppression of adrenal function).

3. Ketamine

Overview

Ketamine is a unique intravenous anesthetic that provides dissociative anesthesia and analgesia. It is known for its ability to increase cerebral blood flow.

Dose

• Dose: 1-2 mg/kg IV (for induction)

Indications

• Induction of anesthesia, analgesia for painful procedures, and in patients with asthma or reactive airway disease.

Contraindications

• Hypersensitivity, severe hypertension, or increased intracranial pressure.

Additional Notes

• Ketamine may offer neuroprotective effects and is often used in pediatric patients due to its safety profile.

4. Barbiturates

Overview

Barbiturates are central nervous system depressants that have been used for induction of anesthesia. They act primarily at the GABA receptor.

Common Agents

• Thiopental

  • Dose: 3-5 mg/kg IV (for induction)

• Methohexital

  • Dose: 1-2 mg/kg IV (for induction)

• Thiamylal

  • Dose: 3-5 mg/kg IV (for induction)

Indications

• Induction of anesthesia, sedation, and as anticonvulsants.

Contraindications

• Hypersensitivity, porphyria, severe respiratory depression.

5. Propofol

Overview

Propofol is an alkylated phenol that provides rapid sedation and is widely used for induction and maintenance of anesthesia.

Dose

• Dose: 1-2.5 mg/kg IV (for induction)

Indications

• Induction and maintenance of anesthesia, sedation for procedures.

Contraindications

• Hypersensitivity to propofol or its components, egg or soy allergy.

Additional Notes

• Propofol is favored for outpatient procedures due to its rapid recovery profile and low incidence of nausea and vomiting.

6. Opioid Analgesics

Overview

Opioids are potent analgesics that act centrally on μ-receptors in the brain and spinal cord. They are often used in conjunction with other anesthetic agents.

Common Agents

• Meperidine

  • Dose: 25-100 mg IV (for analgesia)

• Fentanyl-based compounds

  • Dose: 25-100 mcg IV (for analgesia)

• Morphine

  • Dose: 2-10 mg IV (for analgesia)

• Codeine

  • Dose: 15-60 mg IV (for analgesia)

• Oxymorphone

  • Dose: 1-5 mg IV (for analgesia)

Indications

• Pain management, adjunct to anesthesia.

Contraindications

• Hypersensitivity, respiratory depression, severe asthma, or head injury.

Additional Notes

• Opioids have differing potencies, and equianalgesic doses can result in similar degrees of respiratory depression. Therefore, there is no completely safe opioid analgesic.

1. Refractory periods: absolute (neuron cannot fire) and relative (can fire with greater than normal depolarization)

2. Specific receptor theory: local anesthetics bind inside Na channel, block entry of Na

3. Membrane expansion theory: anesthetics work by disrupting lipid bilayer around ion channel

4. Mechanism of action for local anesthetics: local must be in uncharged form to cross lipid bilayer of axon

a. Locals made as salts (usually mixed with HCl).  [Uncharged form] depends on pH of tissue, pKa of local-found by Henderson-Hasselbach equation- pH = pKa + log ( [RN] / [RNH+] )

b. Once inside axon, only charged form will bind to Na channel.

c. At physiologic pH, enough base exists outside nerve so anesthetic rapidly diffuses into axon.  Rate-limiting step is how much uncharged local is present outside neuron.

d. So, starts with 100 molecules of local, 25 of which are uncharged and 75 charged.  The 25 uncharged enter the neuron, leaving 0 on outside so the remaining 75 re-equilibrate to produce more uncharged which enters neuron .  Inside neuron the reverse happens as converted to ionic form then rapidly binds channel.

5. Inflammatory effects: ® an acidic environment, less of local can be converted to uncharged form (less enters).

6.  Pharmakokinetics: pool of local outside neuron depleted as local diffuses into adjacent muscles, tissues, enters blood vessels.  Since locals are water soluble, they go throughout body (even cross BBB and placenta)

7. Autonomic nervous system: sympathetic and parasympathetic divisions.  Both secrete pre-ganglionic acetylcholine.  Postganglionic NT is acetylcholine for parasympathetic, norepinephrine for sympathetic (also secrete E, dopamine, and seratonin, all are catecholamines).

a. Sympathetic catecholamines affect receptors (local anesthetics affect a1-mediated actions which cause vasoconstriction) ® fight or flight responses (pupil & bronchiole dilation, ­ HR, BP, blood glucose; ¯ GI)

b. Catecholamines inactivated by reuptake, diffusion, or metabolized by monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT) then metabolites excreted in urine.

c.  When choosing sympathomimetic drug, consider receptor subtype in tissue and choose drug that affects it.