Adverse Drug Reactions

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ADR Basics - Danger Decoder

  • Definition: Harmful, unintended reaction to a drug at normal therapeutic doses.
  • Classification (Rawlins & Thompson):
    • Type A (Augmented):
      • Pharmacologically predictable, dose-dependent.
      • Common (≈80% of ADRs). Low mortality.
      • Manage: Reduce dose or withhold.
      • E.g., Bleeding with anticoagulants; respiratory depression with opioids.
    • Type B (Bizarre/Idiosyncratic):
      • Non-dose-related, unpredictable; patient-dependent (genetic/immunologic).
      • Uncommon. Higher mortality.
      • Manage: Withdraw drug immediately; avoid in future.
      • E.g., Anaphylaxis to penicillin; Malignant Hyperthermia with succinylcholine.
  • 📌 Mnemonic: A = Augmented (dose-related); B = Bizarre (patient-related).
  • Severity: Graded: Mild, Moderate, Severe, Lethal.
  • Causality Assessment: Naranjo Algorithm commonly used.

⭐ Type B reactions, though rare, often have higher morbidity and mortality, making their recognition critical an anesthesiology practice for drugs like succinylcholine or antibiotics administered perioperatively.

Drug Dossiers - Anesthetic Antagonists

  • Naloxone (Opioid Antagonist)

    • Mech: Competitive antagonist at $\mu, \kappa, \delta$ receptors.
    • Uses: Opioid OD, respiratory depression reversal.
    • Dose: 0.4-2 mg IV; Peds: 0.01 mg/kg. Repeat prn.
    • Onset: 1-2 min (IV). Duration: 30-90 min (⚠️ shorter than agonist).
    • ADRs: Acute withdrawal, pulmonary edema.
    • 📌 "NAloxone = Narcotic Antagonist."
  • Flumazenil (Benzodiazepine Antagonist)

    • Mech: Competitive antagonist at GABA-A BZD site.
    • Uses: BZD OD, sedation reversal.
    • Dose: Initial 0.2 mg IV, then 0.1 mg q1min up to 1 mg. Peds: 0.01 mg/kg.
    • Onset: 1-2 min. Duration: 30-60 min (⚠️ shorter than agonist).
    • ADRs: Seizures (esp. BZD dependence/TCA OD), agitation.
    • Contra: Seizure disorder, BZD dependence, TCA OD.

    ⭐ Flumazenil may precipitate seizures in chronic BZD users or with pro-convulsant co-ingestion (e.g., TCAs).

  • Sugammadex (NMBA Antagonist: Rocuronium, Vecuronium)

    • Mech: Selective relaxant binding agent; encapsulates steroidal NMBAs.
    • Uses: Reversal of rocuronium/vecuronium blockade.
    • Dose: Mod (TOF 2): 2 mg/kg; Deep (PTC 1-2): 4 mg/kg; Immed (Roc 1.2 mg/kg): 16 mg/kg IV.
    • Onset: <3 min for TOF >0.9.
    • ADRs: Anaphylaxis, bradycardia. ⚠️ ↓ hormonal contraceptive efficacy (7 days alt.).
    • 📌 "SUGAmmadex = SUcks GAmmacyclodextrin."

Crisis Calls - Code Red Reactions

Immediate recognition and management are critical for these life-threatening anesthetic adverse drug reactions.

  • Anaphylaxis

    • Triggers: Antibiotics (penicillin), muscle relaxants (suxamethonium, rocuronium), latex, colloids.
    • Signs: Rapid onset hypotension, bronchospasm, flushing, urticaria, angioedema.
    • Management:
      • STOP agent. ABCs (airway, 100% O2, IV fluids).
      • Epinephrine: 0.3-0.5 mg IM (1:1000) or 50-100 mcg IV (1:10000) for severe cases. Repeat q5-15min.
      • Antihistamines (H1/H2), Corticosteroids (Hydrocortisone 100-200 mg IV).
  • Malignant Hyperthermia (MH)

    • Triggers: Volatile anesthetics (sevoflurane), Suxamethonium.
    • Signs: ↑ETCO2 (early, persistent), tachycardia, muscle rigidity (masseter), hyperthermia (late), acidosis.

    ⭐ Unexplained, persistent rise in End-Tidal CO2 (ETCO2) is often the earliest and most sensitive sign of Malignant Hyperthermia.

    • Management:
      • STOP triggers. Call help. Hyperventilate (100% O2, high flows).
      • Dantrolene: 2.5 mg/kg IV push, repeat q5-10min (max 10 mg/kg).
      • Active cooling. Treat acidosis, hyperkalemia.
  • Local Anesthetic Systemic Toxicity (LAST)

    • Causes: Accidental IV injection, excessive dose, rapid absorption.
    • Signs: CNS (metallic taste, tinnitus, agitation, seizures, coma), CVS (arrhythmias, hypotension, cardiac arrest).
    • Management:
      • STOP LA. ABCs. Seizure control (benzodiazepines).
      • Lipid Emulsion (20% Intralipid): Bolus 1.5 mL/kg, infusion 0.25 mL/kg/min. Max 12 mL/kg.
      • Modified ACLS (epinephrine < 1 mcg/kg; amiodarone for VT/VF).

High‑Yield Points - ⚡ Biggest Takeaways

  • Malignant Hyperthermia: Triggered by succinylcholine & volatile anesthetics; RYR1 gene implicated; treat with dantrolene.
  • Anaphylaxis: Common with NMBs (rocuronium), antibiotics, latex; IgE-mediated; adrenaline is cornerstone treatment.
  • Suxamethonium Apnea: Due to pseudocholinesterase deficiency (genetic/acquired); causes prolonged muscle paralysis.
  • Propofol Infusion Syndrome (PRIS): With prolonged, high-dose propofol; features metabolic acidosis, rhabdomyolysis, cardiac failure.
  • Local Anesthetic Systemic Toxicity (LAST): CNS symptoms (seizures) precede cardiac toxicity; lipid emulsion therapy is crucial.
  • Opioid-induced Chest Wall Rigidity: Especially with rapid, high-dose fentanyl; manage with naloxone or NMBs.

Practice Questions: Adverse Drug Reactions

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