ABSTRACT OF THE WEEK

The Canadian veterinary journal. La revue vétérinaire canadienne
Volume 64 | Issue 3 (March 2023)

Treatment and outcome following substantial ketamine overdose in a dog.

Can Vet J. March 2023;64(3):235 - 238.

Lindsay A Parker¹, Katie Krebs², Poching Lydia Pan³, Kelley M Varner⁴, Katie L Hoddinott⁵

¹ Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island (Parker, Krebs, Pan, Hoddinott); University of Missouri Veterinary Health Center, Kansas City, Missouri, USA (Parker, Varner); University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA (Krebs); Central Toronto Veterinary Referral Clinic, Toronto, Ontario (Pan).; ² Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island (Parker, Krebs, Pan, Hoddinott); University of Missouri Veterinary Health Center, Kansas City, Missouri, USA (Parker, Varner); University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA (Krebs); Central Toronto Veterinary Referral Clinic, Toronto, Ontario (Pan).; ³ Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island (Parker, Krebs, Pan, Hoddinott); University of Missouri Veterinary Health Center, Kansas City, Missouri, USA (Parker, Varner); University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA (Krebs); Central Toronto Veterinary Referral Clinic, Toronto, Ontario (Pan).; ⁴ Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island (Parker, Krebs, Pan, Hoddinott); University of Missouri Veterinary Health Center, Kansas City, Missouri, USA (Parker, Varner); University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA (Krebs); Central Toronto Veterinary Referral Clinic, Toronto, Ontario (Pan).; ⁵ Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island (Parker, Krebs, Pan, Hoddinott); University of Missouri Veterinary Health Center, Kansas City, Missouri, USA (Parker, Varner); University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania, USA (Krebs); Central Toronto Veterinary Referral Clinic, Toronto, Ontario (Pan).

Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.

Abstract

A 9-year-old, 3.7 kg (8.14 lb) neutered male Yorkshire terrier mix was treated following a ketamine overdose after subcutaneous ureteral bypass surgery. Due to an error in communication and misinterpretation of an electronic treatment sheet, the dog was inadvertently placed on a continuous rate infusion (CRI) of ketamine at 67.6 mg/kg per hour, rather than the intended 0.2 mg/kg per hour rate. Four hours after initiation of the ketamine CRI, the dog developed signs indicative of a ketamine overdose including tachycardia, hyperthermia, anisocoria, and hypoglycemia. It was determined the dog had received an iatrogenic overdose of ketamine; the infusion had been running at 67.6 mg/kg per hour, resulting in 270 mg/kg of ketamine over 4 h. Aggressive supportive measures were undertaken, and the dog gradually recovered over an 18-hour period, without lasting consequences of the overdose. To the authors' knowledge, there are no current published reports of a ketamine overdose of this magnitude in a dog. This case report documents an iatrogenic 338 times intravenous ketamine overdose in a dog, which was successfully managed with supportive care. In addition, it highlights the importance of doctor-technician communication and the potential errors in using electronic treatment sheets.

PubMed Other Abstract

Traitement et résultat à la suite d’une surdose importante de kétamine chez un chien. Un Yorkshire terrier mélangé mâle de 9 ans et pesant 3,7 kg (8,14 lb) a été traité à la suite d’une surdose de kétamine après un pontage urétéral sous-cutané. En raison d’une erreur de communication et d’une mauvaise interprétation d’une feuille de traitement électronique, le chien a été placé par inadvertance sous une perfusion à débit continu (IRC) de kétamine à 67,6 mg/kg par heure, au lieu du débit prévu de 0,2 mg/kg par heure. Quatre heures après le début de l’IRC de kétamine, le chien a développé des signes indiquant une surdose de kétamine, notamment de la tachycardie, de l’hyperthermie, de l’anisocorie et de l’hypoglycémie. Il a été déterminé que le chien avait reçu une surdose iatrogène de kétamine; la perfusion fonctionnait à 67,6 mg/kg par heure, entraînant 270 mg/kg de kétamine en 4 h. Des mesures de soutien agressives ont été mises en place et le chien s’est progressivement rétabli sur une période de 18 heures, sans conséquences durables du surdosage.À la connaissance des auteurs, il n’existe actuellement aucun rapport publié sur une surdose de kétamine de cette ampleur chez un chien. Ce rapport de cas documente une surdose iatrogène de kétamine de 338 fois par voie intraveineuse chez un chien, qui a été gérée avec succès avec des soins de soutien. De plus, il met en évidence l’importance de la communication médecin-technicien et les erreurs potentielles dans l’utilisation des fiches de traitement électroniques.(Traduit par D^r Serge Messier).

Companion Notes

Case report on the treatment and outcome following substantial ketamine overdose in a dog

Introduction on ketamine

- phencyclidine derivative and dissociative anesthetic

- it dissociates the thalamocortical and limbic systems

- via an antagonistic action on N-methyl-D-aspartate (NMDA) receptors

- resulting in cataleptic consciousness

- primarily metabolized by the liver via demethylation and hydroxylation

- excreted via the kidneys

- at appropriate dosages, it’s a potent anesthetic and analgesic

- results in varying degrees of hypertonicity as a sole analgesic

- therefore it’s often used in combination with other medications

- analgesics, sedatives, or muscle relaxants

- associated with minimal cardiovascular depression

- it’s a mild respiratory depressant

- it has sympathomimetic effects, so it tends to increase the following:

- cardiac output

- mean arterial blood pressure

- heart rate

- in human medicine

- overdoses of ketamine usually result in a full recovery

- in feline medicine, there’s a single report of cardiopulmonary arrest in a cat

- due to a 20X overdose of ketamine as an IV bolus for induction of anesthesia

- cat survived following the following:

- manual and mechanical ventilation

- drug reversal

- closed chest compressions

- emergency drug administration

- IV fluids

- yohimbine, 0.1 mg/kg IV q4h for total of 3 doses also given

- report’s authors suggest it may provide partial antagonism of ketamine in cats

- in 1 research study on antagonism of ketamine anesthesia by a number of agents

- yohimbine alone had the following affects

- increased alertness

- shorter ketamine-induced anesthesia time

Case report of a 9-year-old, 3.7 kg (8.14 lb) neutered, sex:M miniature breed dog

- at referral for right hydronephrosis and hydroureter

- pre-anesthetic PCV/TP, lactate, BUN, glucose and renal biochemistry:

- minor electrolyte abnormalities

- unilateral subcutaneous ureteral bypass (SUB) procedure performed

- performed in right kidney without complication

- dog recovered uneventfully

- postop analgesia requested via electronic treatment sheet

- fentanyl and ketamine continuous rate infusions (CRIs)

- on separate syringe pumps

- analgesic orders also verbally communicated to ICU technicians

- fentanyl dosed at 3 µg/kg per hour

- after an intravenous loading dose of 3 µg/kg

- ketamine dosed at 0.2 mg/kg per hour

- after an intravenous loading dose of 0.2 mg/kg

- dog became sedated after loading doses

- dog also getting IV fluids with KCl, maropitant, ampicillin and pantoprazole

- 4 hour after initiating ketamine CRI, a medical error was noticed

- syringe pump was programmed to deliver ketamine using a 0.3 mg/mL dilution

- but ketamine was administered undiluted (100 mg/mL)

- dog had inadvertently received ketamine at 67.6 mg/kg per hour

- resulting in a total of 270 mg/kg over a 4 hour period

- dog's vital parameters still within normal limits at that time

- ketamine CRI discontinued

(fentanyl continued at 3 µg/kg per hour, as dog was still in early postop)

- ASPCA Animal Poison Control Center (APCC) contacted

(literature review found limited information)

- clinical signs from the sympathomimetic medication could develop

- recommended continued supportive care

- IV fluids (120 mL/kg per day) to promote diuresis

- eye lubrication every 30 min

- 1 hour after discontinuing ketamine CRI

- dog began to develop clinical signs indicative of a ketamine overdose

- tachycardia at 200 bpm

- loss of palpebral reflex

- hyperthermia at 41.3°C [106°F]

- abnormal lung sounds (increased upper respiratory noise)

- suspected due to increased tracheal secretions

- venous blood gas: hypoglycemia, mild at 3.2 mmol/L with reference at 3.3-6.2

- active cooling measures

- ice packs placed onto fluid lines and around dog's body

- dog developed an acute dystonic reaction

(characteristic of ketamine toxicity)

- recumbency care and physiotherapy initiated

- 2 hours after discontinuing ketamine

- signs had developed suggesting possible increased intracranial pressure

- severe anisocoria with left miosis noted

- delayed to absent pupillary light reflex, bilaterally and marked

- treatment: IV fluids with KCl continued

- mannitol IV bolus, 257 mg/kg over 20 min

- towels used to elevate the head

- anisocoria persisted, but overall mentation improved

- 2^nd mannitol bolus given 3 hours later

- due to recurrent depressed mentation

- no improvement seen so mannitol was discontinued

- corneal ulceration detected by fluorescein staining

(attributed to the anisocoria)

- topical tobramycin, ofloxacin, tropicamide and serum initiated

- IV dextrose bolus due to progressive hypoglycemia at 1.5 mmol/L

- hypoglycemia resolved

- normal 3-view thoracic radiography, abdominal ultrasound, and echocardiography

- renal biochemistry profile, urinalysis, and urine culture:

- all normal except for hyposthenuria likely secondary to increased fluid rate

- clinical course over following 18 hours: dog continued to improve

- anisocoria resolved after 3 days of ocular treatment

- 2 days postop: nasogastric tube placed for enteral nutrition

- ondansetron, 0.2 mg/kg IV q8h to reduce nausea

- fentanyl CRI tapered and IV buprenorphine prescribed

- 7 days postop: dog still inappetent

- abdominal ultrasound confirmed pancreatitis

- dog discharged 12 days postop

- outcome at 5 month recheck, full recovery

- dog had no side effects from the ketamine overdose

“As ketamine has no reversal agent, prompt supportive care as highlighted in this report should be initiated as soon as a ketamine overdose has been discovered. In addition, this case report highlights the importance of communication between veterinarians and veterinary technicians to avoid medical errors.”

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