Intravenous Lipid Emulsion (ILE - Intralipid)

Mechanism

Pharmacological Group and Molecular Target

Emulsion of hydrophobic neutral lipids based on soybean oil or medium chain triglycerides.

Detailed Mechanism of Action

Local anesthetics (such as bupivacaine) and certain cardiotoxic xenobiotics (such as verapamil, amitriptyline or haloperidol) are highly lipophilic. Its overdose blocks cellular cardiac sodium channels and alters myocardial mitochondrial oxidative phosphorylation, inducing refractory cardiac arrest. Treatment with intravenous lipid emulsion acts through two main biophysical mechanisms:

1. Lipid Sink Mechanism: Lipid infusion creates a large-volume suspended lipid phase in the plasma intravascular space that attracts, sequesters and absorbs free lipophilic drug molecules from vulnerable cardiac and brain tissues, reducing their bioavailability and cellular toxicity.
2. Direct metabolic effect: The lipid emulsion provides medium chain free fatty acids to the compromised myocardium, restoring mitochondrial ATP production by overcoming local enzymatic inhibition induced by the toxin.

Indicators and dose

Specific Clinical Indications

• Severe systemic local anesthetic toxicity (LAST) characterized by seizures, coma, or refractory hemodynamic collapse following administration of bupivacaine, levobupivacaine, or ropivacaine.
• Refractory cardiac arrest secondary to overdose of highly lipophilic cardiotoxic drugs (such as tricyclic antidepressants, highly soluble beta-blockers such as propranolol, or calcium antagonists).

Dosage Scheme and Infusion Protocols

Rescue Protocol in LAST (Use of 20% Emulsion)

1. Initial Rescue Bolus: Administer 1.5 mL/kg of 20% lipid emulsion IV as a rapid bolus in 1 minute. In a 70 kg adult, this is equivalent to approximately 100 mL of emulsion.
2. Maintenance Infusion: Start a continuous infusion of the emulsion at a rate of 0.25 mL/kg/minute progressively for the next 30 to 60 minutes.
3. Repetition of bolus: If cardiovascular collapse persists or the pulse does not recover within 3-5 minutes of onset, an identical rapid bolus dose can be repeated (up to a maximum of 3 boluses in total) and double the infusion rate to 0.5 mL/kg/minute.

Security

Adverse Effects (ADR) and Complications

• Transient acute pancreatitis (massive hypertriglyceridemia after infusion), systemic fluid overload with mild pulmonary edema, subclinical pulmonary fat embolism, total analytical interference in hospital laboratories due to high plasma opacity (temporary inability to quantify creatinine, electrolytes or cardiac enzymes).