A 38-year-old woman undergoes femoral nerve block for knee arthroscopy. The anesthesiologist injects 30 mL of 2% lidocaine with 1:100,000 epinephrine. Within 5 minutes, she develops perioral tingling, metallic taste, and visual disturbances. Her blood pressure is 142/88 mmHg and heart rate is 115/min. She is alert and oriented. Which of the following is the MOST appropriate next step?

Explanation

## Graded Response to Early LAST: Prodromal vs. Manifest Toxicity ### Clinical Differentiation This patient presents with **early CNS warning signs** (prodromal phase) without seizure activity: - Perioral tingling and metallic taste (sensory symptoms) - Visual disturbances (CNS excitation) - Hemodynamic changes (mild hypertension, tachycardia) - **Preserved consciousness and orientation** **Key Point:** Not all LAST presentations require immediate lipid emulsion bolus. The 2017 ASRA guidelines stratify management by severity: | Feature | Prodromal LAST | Manifest LAST (Seizure/CV Collapse) | |---------|---|---| | **CNS signs** | Restlessness, tinnitus, circumoral numbness | Seizure, loss of consciousness | | **Cardiovascular** | Mild hypertension, tachycardia | Bradycardia, hypotension, arrhythmia, cardiac arrest | | **Immediate lipid?** | No — observe with readiness | Yes — bolus immediately | | **Management** | Oxygen, IV access, seizure prophylaxis | Lipid 1.5 mL/kg bolus + CPR if needed | ### Management Algorithm for This Patient ```mermaid flowchart TD A[Early LAST signs: alert, no seizure]:::outcome --> B[Stop injection]:::action B --> C[Establish IV access]:::action C --> D[Administer 100% O₂]:::action D --> E[Position supine, elevate legs]:::action E --> F[Have lipid emulsion at bedside]:::action F --> G{Seizure develops or CV collapse?}:::decision G -->|Yes| H[Lipid bolus 1.5 mL/kg immediately]:::urgent G -->|No| I[Continue close monitoring]:::action I --> J{Symptoms resolve?}:::decision J -->|Yes| K[Discharge after observation]:::outcome J -->|No or worsening| L[Administer lipid emulsion]:::action ``` ### Why This Approach? **High-Yield:** The ASRA 2017 update emphasizes: 1. **Lipid emulsion is NOT indicated** for prodromal symptoms alone 2. **Observation with readiness** is appropriate for early warning signs 3. **Lipid bolus is reserved for** seizure activity, loss of consciousness, or cardiovascular instability 4. **Premature lipid administration** exposes the patient to unnecessary IV lipid risks (hypertriglyceridemia, pancreatitis, fat embolism) **Clinical Pearl:** Early recognition of prodromal symptoms (tinnitus, circumoral numbness, visual changes) allows intervention *before* progression to seizure or cardiovascular collapse. Oxygen and IV access alone may prevent escalation. **Mnemonic:** **WATCH & WAIT** for prodromal LAST — **W**arn the team, **A**irway ready, **T**reat with O₂, **C**all for lipid, **H**ave IV access. **W**ait for seizure or CV signs before bolus. **A**void premature lipid. **I**V access mandatory. **T**ransfer to ICU if any progression. **E**xpect full recovery with prompt recognition.