Introduction to Intralipid
Intralipid is a sterile, intravenous fat emulsion used primarily as a source of calories and essential fatty acids for patients who cannot receive adequate nutrition through their digestive system. It is a key component of parenteral nutrition (PN). Composed mainly of soybean oil (around 20%), egg yolk phospholipids (1.2%), and glycerin (2.25%), Intralipid provides vital lipids that are crucial for cell function and metabolism. Its two primary indications are providing a dense energy source and preventing or treating essential fatty acid deficiency (EFAD). The composition of Intralipid is designed to mimic the body's own chylomicrons, which are particles that transport dietary lipids from the intestines to other parts of the body. Due to its critical role and potential for complications, administering Intralipid requires strict adherence to established guidelines, particularly regarding the approach to infusion.
Standard Infusion Approaches for Parenteral Nutrition
The appropriate infusion strategy for Intralipid varies significantly based on the patient's age, weight, and clinical condition. A cautious, gradual approach is universally recommended to monitor for adverse reactions.
Adult Infusion
For adults receiving Intralipid 20% as part of PN, the initial approach should involve a slow rate for a defined period. If the patient shows no signs of an adverse reaction, this rate can be increased. The total daily dosage for an adult involves considerations based on body weight and should constitute no more than a certain percentage of the patient's total caloric intake. On the first day of therapy, a limitation on the total volume infused of Intralipid 20% is often recommended.
Pediatric and Neonatal Infusion
Pediatric dosing requires even greater caution, especially in neonates and premature infants who have a limited ability to clear lipids from their circulation.
- Neonates and Infants (Birth to 2 years): The initial dosage starts at a lower level and can be gradually increased to a maximum daily dose. The initial infusion approach should be slow for an introductory period, after which it can be slowly increased. For premature infants, a continuous infusion over 24 hours is often preferred to maintain stable plasma lipid levels. Rapid infusion in this population has been linked to severe adverse reactions, including acute respiratory distress and metabolic acidosis.
- Children (2 to <12 years): The initial dosage is typically within a certain range, with a maximum daily limit. The infusion can be started at a slow rate for an initial period before gradually increasing.
- Adolescents (12 to 17 years): The dosage starts at a particular level and should not exceed a specific limit per day. The initial rate is similar to that of younger children, starting at a conservative level.
Intralipid for Local Anesthetic Systemic Toxicity (LAST)
Beyond nutrition, Intravenous Lipid Emulsion (ILE) therapy, often using Intralipid 20%, has become a critical rescue treatment for Local Anesthetic Systemic Toxicity (LAST), a rare but life-threatening complication of regional anesthesia. The mechanism is often described as a "lipid sink," where the emulsion sequesters the lipid-soluble anesthetic drug in the plasma, pulling it away from its sites of action in the heart and brain.
The dosing for LAST is different from nutritional administration and requires rapid intervention:
- Initial Bolus: For a patient over a certain weight, a specific volume of 20% lipid emulsion is given rapidly over a short period. For patients under that weight threshold, the dose is calculated based on body weight.
- Continuous Infusion: The bolus is immediately followed by an infusion. For patients over the weight threshold, this is typically a certain volume infused over a defined timeframe. For those under that weight, the rate is calculated per body weight per minute.
- Repeat Dosing: If hemodynamic instability persists, the bolus can be repeated, and the infusion rate can be adjusted. There is a recommended upper limit for the total dose.
| Patient Group | Initial Approach (20% Emulsion) | Max Dose Guideline | Key Consideration |
|---|---|---|---|
| Adults (PN) | Slow initial rate for initial period | Do not exceed a specific g/kg/day limit | Consider limiting total volume on day one |
| Neonates/Infants (PN) | Very slow initial rate for initial period | Do not exceed a specific g/kg/day limit | Rapid infusion is dangerous; monitor triglyceride clearance |
| LAST (>70 kg) | Specific volume bolus over short period | Follow with a continuous infusion strategy | For emergency resuscitation from drug toxicity |
| LAST (<70 kg) | Body-weight based bolus over short period | Follow with a body-weight based infusion rate | Consider total dose limit |
Monitoring and Potential Side Effects
Regardless of the indication, patients receiving Intralipid must be monitored closely. Key monitoring includes liver function tests, serum triglyceride levels, blood counts, and coagulation parameters. Hypersensitivity reactions can occur, as Intralipid contains soybean oil and egg phospholipids, making it contraindicated in patients with known allergies to soy, eggs, or peanuts. Other potential adverse effects include fat overload syndrome, pancreatitis, and Parenteral Nutrition-Associated Liver Disease (PNALD), particularly with long-term use in neonates. The most common side effects in adults are nausea, vomiting, and fever, while pediatric patients may experience anemia and vomiting.
Conclusion
The appropriate infusion rate for Intralipids is not a single value but depends on the patient's age, weight, and the clinical reason for its use. Whether for providing life-sustaining calories and fatty acids or as an emergency antidote for LAST, safe administration hinges on following specific, evidence-based protocols. A slow start, gradual increase, and diligent patient monitoring are universal principles that help mitigate the risks associated with this vital therapy.
For more detailed guidelines, consult the official prescribing information: Intralipid® 20% Prescribing Information on accessdata.fda.gov
