Metallic Taste and Seizure After an Interscalene Block

Local anesthetic systemic toxicity (LAST) from the interscalene block.

• Timing: 25 minutes after injection fits gradual intravascular uptake from a plexus/fascial plane block; onset can be immediate or delayed by tens of minutes.
• Prodrome: metallic taste, perioral numbness, and tinnitus are classic early neurologic symptoms, followed by agitation and then a generalized seizure - an excitatory CNS toxicity sequence.
• Dose context: 150 mg in a 62 kg patient is about 2.4 mg/kg, under the often-quoted 3 mg/kg ceiling. That proves a dose limit does not protect you - rapid absorption or intravascular injection can cause toxicity within recommended doses. The clinical picture, not the arithmetic, makes the diagnosis.
• The current phase: SpO2 88% with a rate of 6 is postictal hypoventilation. Hypoxia, hypercarbia, and acidosis lower the seizure threshold and worsen cardiotoxicity, so ventilation is treatment.

First 60 seconds:

1. Call for help - anesthesia, surgeon, rapid response - with a precise message: "suspected LAST, seizure, 150 mg ropivacaine."
2. Airway and breathing: jaw thrust, 100% oxygen by bag-mask with capnography, working suction; support every breath.
3. Stop the seizure: midazolam 2-4 mg IV titrated (lorazepam alternative). Avoid propofol if she is hypotensive. Benzodiazepine is first-line for the convulsion.
4. Get the LAST kit and lipid emulsion into the room - do not wait for cardiovascular collapse to start looking for it.
5. Monitors on and check a pulse - cardiovascular collapse may follow within minutes.

Assume local anesthetic-induced cardiovascular collapse and follow LAST-modified ACLS.

• Start CPR immediately, high-quality compressions with 100% oxygen, and secure the airway early - LAST resuscitation is often prolonged and the patient may need airway protection.
• Lipid emulsion 20% per the ASRA checklist: bolus 1.5 mL/kg lean body weight (~90-100 mL) over about a minute, then infuse at 0.25 mL/kg/min (~15 mL/min). Repeat the bolus once or twice and double the infusion rate if instability persists. Continue for at least 15 minutes after stability is restored.
• Epinephrine in small aliquots, no more than about 1 mcg/kg per dose. Standard ACLS doses can worsen arrhythmias and produce pulmonary edema in LAST.
• Avoid vasopressin, calcium channel blockers, beta blockers, and any additional local anesthetic - including lidocaine for arrhythmias. Amiodarone is acceptable for ventricular arrhythmia.
• Prepare for prolonged resuscitation (hours are possible), activate ECMO or cardiopulmonary bypass capability early if available, and keep the surgeon and anesthesia provider at the bedside.
• Do not inject anything further through the block catheter; note the block time and site for the record.
• Document every drug, dose, and time - this resuscitation has an antidote and the timeline is part of the diagnosis.

• Monitor closely for at least 24 hours. LAST can recur after apparent recovery as lipid-bound drug redistributes. Continuous ECG and neurologic checks; watch for pancreatitis, lipemia, and pulmonary edema from the lipid load.
• Documentation: pre-block vital signs, block time and dose, symptom onset, seizure duration, every drug/dose/time, response, and notification times. Incomplete or late documentation is the most common gap identified in LAST case reviews.
• Report the adverse event and request a team debrief: was aspiration performed before and during injection, was the dose based on lean body weight, was ultrasound used, was the LAST kit stocked and was staff able to locate it under pressure.
• Patient education: explain what happened and why she is admitted, and instruct her to report recurrent numbness, confusion, or palpitations.
• System advocacy: push for LAST kits and checklists in every anesthetizing location, including the Phase I unit, and for periodic simulation. The recovery nurse recognizing the metallic taste and tinnitus prodrome is what buys the team time.