A 38-year-old woman undergoes suturing of a laceration on her forearm under local infiltration anaesthesia. The surgeon uses 0.5% bupivacaine without epinephrine, injecting a total of 80 mL over 10 minutes. After 20 minutes, the patient complains of dizziness, develops slurred speech, and then has a brief generalized tonic-clonic seizure lasting 30 seconds. Vital signs: BP 110/70 mmHg, HR 92/min, RR 16/min, O₂ saturation 98% on room air. The seizure self-terminates. What is the most appropriate immediate next step in management?

Explanation

## Seizure from Local Anaesthetic Toxicity — Management Algorithm ### Clinical Context: Bupivacaine Overdose **Key Point:** This patient received **400 mg of bupivacaine** (80 mL × 0.5% = 400 mg), which **exceeds the safe dose limit of 175 mg without epinephrine** in a 70 kg adult. The CNS symptoms (dizziness, slurred speech) followed by seizure are classic for local anaesthetic toxicity. ### Why This Is NOT Simple Seizure Management | Approach | Why It's Wrong Here | |----------|---------------------| | **Lorazepam alone** | Benzodiazepines treat seizure *symptomatically* but do NOT address the underlying toxin (bupivacaine). Seizures may recur as drug levels remain elevated. | | **Phenytoin** | Phenytoin is for chronic seizure prophylaxis, not acute toxicity. It does NOT remove or inactivate bupivacaine and delays definitive therapy. | | **Observation only** | Bupivacaine has a long half-life (3.5 hours) and high lipophilicity. Without intervention, plasma levels remain toxic and may progress to **cardiovascular collapse** (arrhythmias, hypotension, cardiac arrest). | ### Definitive Management: Lipid Emulsion Therapy ```mermaid flowchart TD A[Local anaesthetic toxicity with seizure]:::outcome --> B{Seizure controlled?}:::decision B -->|Yes| C[Secure airway, 100% O₂]:::action B -->|No| D[Benzodiazepine + airway]:::action C --> E[Administer 20% lipid emulsion<br/>1.4 mL/kg bolus IV over 1 min]:::action D --> E E --> F[Continue infusion at 15 mL/kg/min<br/>until signs of toxicity resolve]:::action F --> G[Monitor for recurrent seizures,<br/>arrhythmias, hypotension]:::action G --> H[ICU admission for observation]:::outcome ``` **High-Yield:** **Lipid emulsion therapy** is the **gold standard** for local anaesthetic toxicity because: 1. **Mechanism:** Lipophilic local anaesthetics (especially bupivacaine) partition into the lipid phase, reducing free plasma concentration 2. **Rapid onset:** Begins working within minutes 3. **Evidence:** Multiple case reports and animal studies show reversal of CNS and cardiovascular toxicity 4. **Guideline:** ACLS 2015 and beyond recommend lipid emulsion as first-line for local anaesthetic toxicity ### Correct Sequence of Actions 1. **Immediate:** Secure airway, give 100% O₂, stop injection 2. **If seizure ongoing:** Benzodiazepine (lorazepam 2–4 mg IV) or propofol 3. **Definitive:** **20% lipid emulsion 1.4 mL/kg IV bolus over 1 minute** - For a 70 kg patient: 98 mL bolus 4. **Maintenance:** Infusion at 15 mL/kg/min (1050 mL/min for 70 kg) until toxicity resolves 5. **Monitoring:** Continuous cardiac monitoring, repeat bolus if toxicity recurs 6. **ICU admission** for observation and supportive care **Clinical Pearl:** In this case, the seizure has already self-terminated, so benzodiazepine is NOT the immediate priority — **lipid emulsion is**. The goal is to prevent **cardiovascular collapse** (hypotension, arrhythmias, cardiac arrest), which can occur as bupivacaine levels remain high. **Warning:** Do NOT delay lipid emulsion therapy while waiting for seizure recurrence or cardiovascular instability. Administer as soon as toxicity is recognized. [cite:KD Tripathi 8e Ch 11; ACLS Guidelines 2015]