Imagine this clinical scenario: a four-year-old spayed female domestic short-haired cat is presented to your emergency room with seizures and hypersalivation. The owners described the first episode of seizures as occurring almost three hours after applying a permethrin spot-on product designed for dogs directly on their cat’s coat. This scenario is common in emergency rooms as many owners do not know that permethrin-based products intended to control ectoparasites in dogs should not be used in cats and may cause severe clinical signs or death.
The owners are concerned about their cat’s welfare and the associated costs of treatment. You discuss with them two novel intravenous lipid emulsion (IVLE) therapies useful for reducing hospitalisation times: soybean oil-based therapy and ClinOleic therapy.
Five case reports and one randomised clinical trial were critically appraised. Limitations of the studies include low sample sizes, only one study which evaluated ClinOleic therapy and no study directly comparing treatments.
Pelizzola et al. (2018) showed that three patients had neurological improvement after being treated with soybean oil-based IVLE therapy, with a mean time to recovery of 10 hours. An important limitation is that each patient had different treatment protocols, and the study design did not quantify the intrinsic effect of IVLE therapy alone or in combination with other medications (injectable anaesthetics, anticonvulsants). The study also reported differences in permethrin product concentration among the evaluated cases; however, according to Boland and Angles (2010), there is no reported correlation between the amount of permethrin exposure and the severity of clinical signs induced. Therefore, this may not lead to significant differences in the time to recovery.
There is no reported correlation between the amount of permethrin exposure and the severity of clinical signs induced
Ceccherini et al. (2015) found that four patients had neurological improvement within a mean of five hours after low-dose soybean oil-based IVLE administration. A limitation is that three patients were treated in another clinic before arriving at the hospital, and information about any previous treatment was not available. Also, different dosages and constant rate infusions (CRI) were used for each patient, which can make it difficult to establish a dosing protocol for this treatment.
Haworth and Smart (2012) found that three patients showed a clinical improvement after soybean oil-based IVLE therapy with a mean time to recovery of 8.3 hours. One of the key limitations of this study was that one case received IVLE therapy 72 hours after the exposure and had a second permethrin exposure once discharged from the hospital, which influenced the overall recovery time. Meanwhile, Kuo and Odunayo (2013) found that following initial soybean oil-based IVLE therapy, the mean recovery time in patients with permethrin toxicosis was 14 hours. Both cases required additional IVLE doses, which makes it difficult to establish a dosage protocol.
Brückner and Schwedes (2012) was the only study that evaluated ClinOleic IVLE therapy administration, with the mean recovery time being 39 hours. There were, however, differences in the administration of ClinOleic IVLE therapy after initial exposure (24 hours for case one and nine hours for case two), which could have influenced the time to recovery between both cases.
A statistically significant difference in recovery time (P <0.006) was found among patients treated with soybean oil-based IVLE therapy compared to control patients
The randomised clinical trial by Peacock et al. (2015) evaluated 34 cats treated with soybean oil-based IVLE therapy (20 cats) compared with a saline solution control (14 cats). A statistically significant difference in recovery time (P <0.006) was found among patients treated with soybean oil-based IVLE therapy compared to control patients. The mean time to recovery was 5.5 hours in the treatment group and 16.2 hours in the control group. This study also used other medications in combination with IVLE therapy, but no statistically significant differences were found between control and treated patients.
Overall, the findings showed that the mean recovery time after soybean oil-based IVLE therapy in patients with permethrin intoxication was 8.5 hours and the mean time to recovery after olive oil-based emulsions (ClinOleic therapy) was 39 hours. This may suggest that soybean oil-based formulations are a better option for reducing the recovery time in cats after permethrin toxicity. However, the availability of evidence to answer this clinical question is scarce, particularly surrounding the clinical effectiveness of ClinOleic IVLE therapy. Further research into its use is therefore required, alongside robust clinical trials comparing both intralipid therapies.
Considering that IVLE therapy is still an experimental procedure, it is important to be prepared for any potential adverse reactions that could arise
All the studies appraised used different dosage protocols of intravenous boluses or CRIs of lipids. Currently, there is no consensus among guidelines or protocols for IVLE therapy dosage in feline patients with permethrin intoxication, but, on average, the dosage protocols used for both IVLE therapies ranged from an initial bolus of 1 to 2.5ml/kg and a CRI of 4 to 5ml/kg/h. It is worth noting that any intralipid therapy must be used as part of an adjuvant protocol, and, considering that IVLE therapy is still an experimental procedure, it is important to be prepared for any potential adverse reactions that could arise.