Intralipid (IL) is a solution of small lipid droplets suspended in water. When administered intravenously, IL provides essential fatty acids, linoleic acid (LA), an omega-6 fatty acid, alpha-linolenic acid (ALA), an omega-3 fatty acid. It is made up of 20% soybean oil/fatty acids (comprising linoleic acid, oleic acid, palmitic acid, linolenic acid and stearic acid), 1.2% egg yolk phospholipids (1.2%), glycerin (2.25%) and water (76.5%).
Possible Mode of Action:
It is thought that fatty acids within the emulsion serve as ligands to activate peroxisome proliferator-activated receptors (PPARs) expressed by the NK cells. This is believed to decrease NK cytotoxic activity, and thereby enhance implantation. A growing number of IVF programs, including ours, perform egg retrieval under conscious sedation using Propofol, a short acting hypnotic agent. Interestingly, similar to Intralipid 1% Propofol also contains the same concentration of soybean oil, and purified egg phospholipid, with glycerin. Perhaps its use offers a fringe benefit in cases of immunologic implantation dysfunction.
Whatever the exact mechanism of action might be, IL exerts a modulating effect on certain immune cellular mechanisms largely by down-regulating cytotoxic /activated natural killer cells (NKa). This effect is enhanced through the concomitant administration of corticosteroids such as dexamethasone, prednisolone and prednisone which in my opinion do so by immune modulation of T cells . The combined effect of IL + steroid therapy is thought to suppresses pro-inflammatory cellular (Type-1) cytokines such as interferon gamma and TNF-alpha, produced in excess by activated NK cells and cytotoxic T cells.
IL will in about 80% of cases, successfully down-regulats activated natural killer cells (NKa) within 2-3 weeks. In this regard it is likely to be just as effective as IVIg but at a fraction of the cost and with a far lower incidence of side-effects. Its effect lasts for 4-9 weeks when administered in early pregnancy.
Can in-vitro (laboratory) tests assess for an immediate benefit of IL on Nka?
Since the down-regulation of NKa through IL (or IVIg) therapy can take several weeks to become detectable, it follows that there is really no benefit in trying to assess the potential efficacy of such treatment by retesting NKa in the laboratory after adding IL (or IVIg) to the cells being tested.
Treatment of NKa Using IL:
- Autoimmune Implantation Dysfunction: When it comes to NKa in IVF cases complicated by autoimmune implantation dysfunction, the combination of daily oral dexamethasone commencing with the onset of ovarian stimulation and continuing until the 10th week of pregnancy, combined with an initial infusion of IL (100ml, 20% Il dissolved in 500cc of saline solution, 10-14 days prior to embryo transfer and repeated once more (only), as soon as the blood pregnancy test is positive), the anticipated chance of a viable pregnancy occurring within 2 completed IVF attempts (including fresh + frozen ET’s) in women under 39Y (who have normal ovarian reserve) is approximately 80%.
- Alloimmune Implantation Dysfunction
- Partial DQ alpha match: IVF patients who have NKa associated with a partial alloimmune implantation dysfunction (DQ alpha match between partners) we use the same IL, infusion as with autoimmune-NKa, only here we prescribe oral prednisone rather than dexamethasone until the 10th week of pregnancy and IL infusions are repeated every 2-4 weeks following the chemical diagnosis of pregnancy until the 24th week. Additionally, (as alluded to elsewhere) in such cases we transfer only a single embryo at a time. This is because in such cases, the likelihood is that one out of two embryos will “match” and we are fearful that if we transfer >1 embryo, and one transferred embryos “matches” it could cause further activation of uterine NK cells and so prejudice the implantation of all transferred embryos. Since we presently have no way of determining which embryo carries the matching paternal DQ alpha gene and thus would transfer only one embryo at a time, it follows that the anticipated viable pregnancy rate per cycle will be much lower than with autoimmune implantation dysfunction. It also follows the only way to improve success with a single embryo being transferred would be to perform PGS on the embryos in advance of ET and then selectively transfer a “chromosomally normal-euploid (“competent”) embryos.
- Total (complete) DQ alpha Match: In cases where the partners have a total alloimmune (DQ alpha) match with accompanying NKa the chance of a viable pregnancy occurring or (if it does) resulting in a live birth at term, is so small as to be an indication for using a non-matching sperm donor or resorting to gestational surrogacy would, in our opinion, be preferable by far.
Contra-Indications and Cautions with Intralipid Infusion:
IL is only contraindicated in conditions associated with severely disordered fat metabolism (e.g. severe liver damage, acute myocardial infarction and shock,
Rarely, hypersensitivity has been observed in patients allergic to soybean protein, egg yolk and egg whites and where fat metabolism may be disturbed (e.g. renal insufficiency, uncontrolled diabetes, certain metabolic disorders and in cases oif severe infection (sepsis) sepsis
Adverse Reactions During Infusions of IL (rare):
Adverse reactions (rare) reported to occur during and/or following infusion of Intralipid include: transient fever, chills, nausea, vomiting, headache, back or chest pain with dyspnea and cyanosis.
In cases of verified or suspected liver insufficiency, liver function must be closely followed. If increased levels of transaminases, alkaline phosphatases or bilirubin appear, infusion of Intralipid should be withheld or postponed, until normalization is achieved.
Very rare cases of hypersensitivity have been observed in patients allergic to soybean protein, egg yolk and egg whites.
Fat metabolism may be disturbed in conditions such as renal insufficiency, uncompensated diabetes, certain forms of liver insufficiency, metabolic disorders and sepsis.
The drip rate is adjusted to 500 ml of a 20% solution should be infused over about 2-3 hours. The infusion should be started at half the infusion rate during the first 30 minutes, under supervision.