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Accidental overdose of intravenously injected unfractionated heparin followed by prolonged clotting times in an anaesthetised Shetland pony
  1. Vuokko Pekkola,
  2. Christina Braun and
  3. Maria Paula Larenza Menzies
  1. Department for Companion Animals and Horses, Veterinarmedizinische Universitat Wien, Wien, Austria
  1. Correspondence to Dr Vuokko Pekkola; vuokko.pekkola{at}


A six-year-old Shetland pony stallion was presented for elective castration. During surgical preparations, undiluted heparin (120 iu/kg) was unintentionally used for intravenous catheter flushing instead of heparinised saline solution. Surgery was cancelled for that day. Thromboelastography was used to monitor blood coagulation immediately after the accidental heparin overdose and on the following days. Three days after the heparin overdose, the coagulation parameters had returned to normal values and the pony was castrated. Anaesthesia and surgery were uneventful without any signs of coagulopathy. One day after surgery, the pony started to show signs of colic and was further diagnosed with colitis, most likely unrelated to heparin but due to repeated administration of penicillin and anaesthesia. Despite intensive treatment, the pony deteriorated progressively and was euthanased due to poor prognosis. Drug overdose is an example of medication error and is one of the most common errors in medicine.

  • medicines
  • anaesthesia
  • horses
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  • Contributors VP anaesthetised the patient, drafted the manuscript and reviewed it critically. CB took part in patient care and reviewed the manuscript. MPLM wrote part of the manuscript and reviewed it critically. All of the authors have accepted the final version to be offered for publication.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Requests for access to data should be addressed to the corresponding author.

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