Medical management of pneumoperitoneum, gastric pneumatosis, and hepatic venous gas secondary to 3% hydrogen peroxide toxicity in a dog

OBJECTIVE

To describe the medical management and outcome of a dog suffering severe hydrogen peroxide toxicity.

CASE SUMMARY

A 3-year-old neutered female Bichon Frise was presented to an emergency and referral practice after ingestion of 10-20 mL/kg 3% hydrogen peroxide. On presentation, the dog was obtunded, was tachypneic, and had severe gastric tympany. Abdominal radiographs revealed pneumoperitoneum, gastric pneumatosis, and hepatic venous gas. The dog was managed conservatively with supportive care and oxygen therapy. Repeat radiographs 6 hours later showed complete resolution of all gas inclusions. While hospitalized, the dog developed severe hematemesis, and abdominal ultrasound revealed severe gastric wall thickening. Subsequent endoscopy confirmed severe gastric mucosal necrosis without evidence of deeper ulceration and relatively mild petechiation of the esophagus. The dog was ultimately discharged after 5 days of hospitalization and continued to do well at home. Recheck ultrasound 5 weeks postdischarge showed normal gastric wall appearance.

NEW OR UNIQUE INFORMATION PROVIDED

To the authors' knowledge, this is the first reported case of pneumoperitoneum secondary to hydrogen peroxide toxicity and the first description of the clinical course of severe toxicity in dogs.

Evidence for the efficacy of the emetic PP796 in paraquat SL20 formulations - a narrative review of published and unpublished evidence

BACKGROUND

The bipyridyl herbicide paraquat was first introduced into agriculture in the 1960s by Imperial Chemical Industries. Due to issues with unintentional poisoning, the centrally acting emetic PP796 was added in 1976 to the company's 20% paraquat ion soluble liquid (SL20) formulations (Gramoxone^®) at a concentration of 0.5 g/L or 0.05% (equivalent to 0.071 mg/kg in a 70 kg adult ingesting a minimum lethal dose of 10 mL) to induce early vomiting (within 30 min), reduce paraquat absorption from the gut, and prevent deaths. Its presence in paraquat products was subsequently mandated by the Food and Agriculture Organization Committee of Experts on Pesticides in Agriculture (predecessor to the current FAO/WHO Joint Meeting on Pesticide Specifications). However, no primary pre-clinical or clinical data have been published regarding the effectiveness of PP796. We reviewed the published literature and unpublished company reports for data on the effectiveness of PP796.

METHODS

PubMed and Google were searched for published studies on the emetic using the search terms "paraquat" and ["emetic" or "PP796"]. Company documents reporting pre-clinical and clinical studies were accessed at the website of U.S. Right to Know (https://usrtk.org/pesticides/paraquat-papers/). Primary study reports were sought as well as overviews written by company toxicologists.

RESULTS

Pre-clinical dog and monkey studies indicated that the PP796 EC50 dose for vomiting was around 0.5-2 mg/kg. Further increasing the PP796 concentration speeded up the time to first vomit and reduced the amount of paraquat absorbed (as assessed by the 0-24 h plasma area-under-the-curve) 100-fold compared to a control group receiving no PP796. However, the dose selected for paraquat SL20 formulations by the company (0.5 g/L or 0.05%) was based exclusively on a phase II study in the early 1970s involving five volunteers receiving 3 different doses, with only two individuals actually vomiting, supplemented by data from 37 patients taking 2 mg in clinical trials. A UK-mandated toxicovigilance study in the 1980s identified only 21 patients ingesting paraquat SL20 with PP796 for whom data on time to vomit was available; of these patients, 11 vomited within 30 min (52.4%, 95%CI 31-73.7%). No effect on mortality could be identified from any study of paraquat SL containing 0.05% PP796. A clinical study in Sri Lanka 30 years after the emetic was first introduced, of a revised formulation (Gramoxone^® Inteon) containing a three-fold higher amount of PP796, as well as MgSO4 and an alginate, showed increased rates of early vomiting and modestly reduced mortality for patients ingesting up to 100 mL.

CONCLUSION

Pre-clinical studies showed a clear dose response for PP796 to cause early vomiting, with effective doses in the 0.5-20 mg/kg range. A too low concentration of PP796 was selected for paraquat formulations based on an inadequate phase II study. Currently, evidence that PP796 at 0.05% in paraquat SL20 causes more rapid vomiting after ingestion is weak or unpublished; no evidence of clinical benefit or fewer deaths has been identified. There is no evidence to support the FAO/WHO Joint Meeting on Pesticide Specifications mandate to include PP796 or any other emetic in paraquat products. Products with higher emetic concentrations have been developed but are not widely used; it is possible they may prevent deaths.

Phenotypic homogeneity of emetic Bacillus cereus isolates in China

Emetic Bacillus cereus strains produce a potent cereulide cytotoxin, which can cause acute and fatal cases of food poisoning. We isolated 18 emetic B. cereus strains from a food poisoning event, and from clinical and non-random food surveillance in China and phenotypic characteristics of haemolysis, starch hydrolysis, salicin fermentation, gelatin liquefaction, cytotoxicity, and susceptibility to antibiotics were assessed. All isolates were positive for haemolysis and gelatin liquefaction, and negative for starch hydrolysis and salicin fermentation. Their haemolytic potentials were intermediate to Bacillus anthracis and B. cereus ATCC 14579 (a non-emetic strain). All isolates were cytotoxic to CHO, Hep-2, and Vero cells, and were sensitive to ampicillin. The homogeneous phenotypes of emetic isolates from China are similar to the corresponding traits of European and Japanese isolates that have been characterized, suggesting highly similar phenotypes of emetic B. cereus worldwide.

Risk Comparison of the Diarrheal and Emetic Type of Bacillus cereus in Tofu

We investigated the ability of biofilm formation, survival, and behavior of diarrheal and emetic Bacillus cereus vegetative cells and spores in tofu. Both diarrheal and emetic B. cereus did not proliferate at a temperature below 9 °C in tofu. However, the emetic B. cereus grew faster than diarrheal B. cereus at 11 °C and had better survival ability at low temperatures. Both diarrheal and emetic B. cereus were able to form a biofilm on stainless steel. These biofilm cells were transferred to tofu in live state. The transferred biofilm cells could not grow at a temperature below 9 °C but grew over 11 °C, like planktonic cells. B. cereus contamination in tofu at a high concentration (>6 logs CFU/g) was not entirely killed by heating at 80, 85, or 90 °C for 2 h. Spores and emetic B. cereus had higher resistance to heat than vegetative cells and diarrheal B. cereus, respectively.

Effect of 50 mg/kg intravenous tranexamic acid on coagulation assessed by rotational thromboelastometry (ROTEM) in healthy Beagle dogs

INTRODUCTION

In people, the antifibrinolytic drug tranexamic acid reduces bleeding and the need for blood products with both normal and exaggerated fibrinolysis without increasing the number of thromboembolic events. In dogs, in addition to prevention and treatment of bleeding, higher doses of tranexamic acid can be used to induce vomiting. The objective of this study was to evaluate the effect of a high dose of tranexamic acid on the coagulation of healthy Beagle dogs. A prospective trial was conducted in eight healthy Beagles receiving tranexamic acid for a concurrent trial evaluating different antiemetics. Rotational thromboelastometry (ROTEM) analysis (EXTEM, APTEM, FIBTEM, INTEM) was performed before and 30 minutes after intravenous administration of 50 mg/kg tranexamic acid. ROTEM parameters before and after tranexamic acid administration and between EXTEM and APTEM were compared with Wilcoxon matched-pairs signed rank test and data is presented as median (range). After tranexamic acid administration, FIBTEM clotting time became significantly shorter (p=0.03) from 37 s (28-124 s) to 33 s (27-40 s) and INTEM clot formation time significantly decreased (p=0.02) from 82 s (47-132 s) to 60 s (43-107 s). After tranexamic acid APTEM MCF was significantly weaker (p=0.01) with 45 mm (30-63 mm) than EXTEM MCF with 55 mm (43-69 mm) and than APTEM MCF before tranexamic acid with 55 mm (43-69 mm) (p=0.02). All other analysed parameters including maximum lysis did not change after administration of tranexamic acid. The administration of 50 mg/kg intravenous tranexamic acid resulted in small changes in ROTEM profiles without inducing a hypercoagulable clot. In conclusion, tranexamic acid can safely be administered to healthy dogs with normal coagulation profiles. As an additional finding, APTEM parameters measured in the current study do not support the use of this test in dogs.

Assessment of hydromorphone and dexmedetomidine for emesis induction in cats

OBJECTIVE

To compare the efficacy of hydromorphone and dexmedetomidine at inducing emesis in cats.

DESIGN

Prospective, blinded, randomized crossover study.

SETTING

Veterinary university teaching hospital.

ANIMALS

12 healthy purpose-bred cats.

INTERVENTIONS

Cats were randomly assigned to receive hydromorphone (0.1 mg/kg, subcutaneously) or dexmedetomidine (7 μg/kg, IM). Following administration, the incidences of emesis, number of emetic events, signs of nausea (hypersalivation, lip licking), temperature, heart rate, respiratory rate, and sedation score were recorded for 6 hours.

MEASUREMENTS AND MAIN RESULTS

Emesis was successful in 9 of 12 (75%) cats when treated with hydromorphone and in 7 of 12 (58%) cats when treated with dexmedetomidine (P = 0.67). Dexmedetomidine was more likely to cause sedation than hydromorphone (P < 0.001). Heart rate in cats was significantly decreased at 1 and 2 hours post-hydromorphone (P = 0.003, 0.014, respectively) and at 1, 2, 3, 5, 6 hours post-dexmedetomidine (P = 0.001, 0.003, 0.038, 0.013, 0.001, respectively). Cats were more likely to develop an increase in body temperature with hydromorphone administration although this was not clinically significant.

CONCLUSIONS

Results of the present study indicate that hydromorphone is an effective alternative to dexmedetomidine for the induction of emesis in cats. Hydromorphone appears to cause less sedation and less decrease in heart rate. Further investigation into the most adequate dose of hydromorphone for optimizing emesis is warranted.

Genotypic heterogeneity of emetic toxin producing Bacillus cereus isolates from China

Emetic toxin-producing Bacillus cereus (emetic B. cereus) is the third member of B. cereus group whose toxins are encoded by megaplasmids, beside anthrax and insecticidal toxins of B. anthracis and B. thuringiensis, respectively. A total of 18 emetic isolates collected from food poisoning events, clinical and non-random food samples in Zhejiang province of China, were analyzed by plasmid screening, pulse field gel electrophoresis, multilocus sequence typing, and toxic gene identification to investigate their genotypic diversity. In this study, 13 plasmid profile types, 14 pulse types and 6 different STs from emetic isolates were detected, in which ST 1035,1038,1053,1054 and 1065 were first assigned and reported. The toxic gene ces existed on its own, or coexisted with other toxic genes bceT, cytk, entFM and nhe, but never with hbl in emetic isolates. The results demonstrated that the emetic B. cereus strains from China were heterologous at genotypic level.