IV Lipid Emulsion for Toxicoses
An 11-year-old spayed Jack Russell terrier presented on emergency for acute onset blindness following possible ivermectin ingestion. Examination by a veterinary ophthalmologist revealed an absent direct and consensual pupillary light response (PLR), menace response, and dazzle reflexes in either eye. Fundic changes were noted, including linear areas of retinal edema. Electroretinography (ERG) results were below normal. The dog’s serum was positive for ivermectin. Approximately 3.5 hours after signs were noted, treatment was initiated using a 20% IV intralipid emulsion. Within 30 minutes, slight PLRs and dazzle reflex returned; the dog was sighted enough to navigate obstacles by the end of the infusion (~1.5 hours after treatment initiation). Rechecks 9 and 11 months later revealed normal neurologic reflexes in both eyes and improved, but still abnormal, ERG readings.
The mechanism for ivermectin-induced blindness is not fully understood, but that ERG readings were not completely extinguished at initial examination suggests the retina is not the only location affected; blindness could relate to cranial nerves II and III, as well as cortical involvement. IV lipid therapy may work via a lipid sink, in which lipophilic ivermectin is sequestered into plasma lipids, effectively removing it from the CNS. Possible adverse effects of IV lipid therapy include pancreatitis, fat emboli, phlebitis, and hypersensitivity reactions.
CommentaryIV lipid emulsion (ILE) therapy, or lipid rescue, has become popular in veterinary medicine for the treatment of many lipid-soluble toxins (eg, local anesthetics), macrocyclic lactones (eg, ivermectin), and other drug toxicities. It is inexpensive and has yet to show significant adverse effects with recommended doses. This study discussed an important point about ILE, in that it may not have the same positive effects in dogs having extreme sensitivity to ivermectin (ie, those with a homozygous mutation in the ABCB1-1D).
Lipid rescue should not be considered unless conventional and antidote therapies have failed. It may be used as an alternative intervention to avoid ventilator support for toxicity-related respiratory failure. Consultation with an animal poison control center is always recommended to determine which toxin may be removed with ILE infusion and the current dosage recommendations.—Elke Rudloff, DVM, DACVECC
SourceIvermectin-induced blindness treated with intravenous lipid therapy in a dog. Epstein SE, Hollingsworth SR. JVECC 23:58-62, 2013.