TOXICOLOGY
Checklist for the successful use of intravenous lipid emulsion therapy:
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What is the lipophilicity (published Log-P value) of the toxicant?
Is there an established, effective antidote available for the toxicant?
Is the toxicosis severe enough to require nonstandard intervention?
Is the present standard of care or antidote therapy cost prohibitive?
Does the owner understand the experimental nature of the therapy, the possible side effects and consent to its
off-label usage?
followed by a constant rate infusion of 0.25ml/kg/min
for 30 to 60 minutes. If no improvement is noted ILET
is unlikely to work and must be discontinued. If some
improvement is noted but some clinical signs persist
intermittent boluses of 1.5ml/kg may be repeated at
4 – 6 hourly intervals for 24 hours and to a maximum
of 8ml/kg/day. Alternatively, a constant rate infusion
of 0.5ml/kg/hour for up to 24 hours is presumed to
be reasonably safe.
Reported side effects with the use of ILET in veterinary cases include post-infusion facial pruritus in a
cat responsive to chlorpheniramine. Pancreatitis and
hyperlipidaemia are the most common side effects reported to the American Animal Poison Control Center
due to the use of lipid emulsions secondary to hyperlipidaemia. A single report of extravasation injury causing local pain and swelling has also been described.
The side effects, of ILET secondary to microbial contamination when used as part of a parenteral nutrition
protocol are well described, however patients requiring parenteral nutritional are more compromised than
healthy animals presenting with acute toxicity
Most commercial lipid emulsion preparations are stabile at room temperature for up to 2 years but once
opened need to be used within 24 hours or discarded and replaced every 24 hours. Appropriate product
storage and strict aseptic technique during the ILET is
imperative to prevent contamination.
Side effects described in human medicine can be
grouped as directs effects including colloidal changes,
pyrexia or anaphylaxis. These are rare with anaphylaxis reported in < 1% of humans and usually manifests
within 20 minutes of administration. Fatty overload
syndrome (FOS) is seen when an excess amount of
lipid emulsion is administered. In humans FOS is seen
at rates over 0.11g/kg/day. Clinical signs include fat
embolism, hyperlipidaemia, hepatomegaly, icterus,
splenomegaly, thrombocytopaenia, prolonged clotting times, haemolysis and neurological signs. These
side effects are thought uncommon when using ILET
in clinical toxicology due to the difference in administration technique. In toxicosis large boluses and infusions are given over short periods but the total daily
dose is significantly less than that administered during
parenteral nutrition. ILET should be avoided in patients
that are critically ill patients or those suffering from
severe pulmonary disease or sepsis as in humans it
caused worsening of oxygenation and diffusion parameters on arterial blood gas measurement.
In conclusion, ILET is a life-saving, non-specific treatment for a variety of lipophilic toxicities causing a
rapid and dramatic improvement in clinical signs with
decreased hospitalisation time. However, it does not
replace conventional antidote therapy and supportive
care. Commercial lipid emulsions are relatively inexpensive with a long shelf-life and easy to administer.
Although the treatment is off-label and experimental,
acceptance for its clinical use has grown, and continues to do so. Further research to elucidate on its
safety and efficacy in clinical toxicology is needed.
Appropriate case selection, understanding the mechanism of action of both ILET and toxicant, as well as
sufficient resources in a hospital setting to allow for
careful monitoring and exact administration technique is imperative for a successful outcome.
List of toxicants whose side effects may potentially be
reversed with the use of intravenous lipid emulsion
therapy:
Toxicant
Log-P value
Amlodipine*
1.90
Baclofen*
1.30
Carprofen*
4.13
Chlorpheniramine*
3.17
Chlorpromazine*
5.35
Clomipramine*
3.30
Cyclosporine*
3.00
Dexamethasone*
1.83
Diazepam*
2.82
Digoxin*
1.26
Diltiazem*
2.80
Ibuprofen ∆
3.50
Itraconazole*
5.90
Ivermectin*
3.50
Ketoprofen*
3.12
Lidocaine*
2.26
Moxidectin*
4.10
Permethrin
6.10
Ŧ
Promethazine*
2.85
Vinblastine*
3.69
* Fernandez et al., 2011 ∆ Bolfer et al., 2014 Ŧ Peacock et al.,
2015
References available on www.vet360.vetlink.co.za
Issue 06 | DECEMBER 2016 | 25