2020 journal article
EVALUATION OF POTASSIUM CHLORIDE ADMINISTERED VIA THREE ROUTES FOR EUTHANASIA OF ANESTHETIZED KOI (CYPRINUS CARPIO)
JOURNAL OF ZOO AND WILDLIFE MEDICINE, 51(3), 485–489.
Immersion in tricaine methanesulfonate (MS-222) is insufficient for euthanasia in at least one species of fish. The current study investigated the effectiveness of potassium chloride (KCl) to euthanize anesthetized koi (Cyprinus carpio). Twenty-eight healthy koi were anesthetized via immersion in 500 mg/L of buffered MS-222 for 10–12 min, manually removed to room air, and randomly administered 10 mEq/kg KCl (333 mg/ml) via one of three routes—intracardiac injection (IC) (n = 7), intracoelomic injection (ICe) (n = 7), or topical instillment over the gill filaments bilaterally (T) (n = 7)—or received no treatment (control, C) (n = 7). A Doppler ultrasonic flow detector was placed over the heart, and sounds were assessed continuously from immediately prior to treatment until 5 min posttreatment and every 5 min thereafter until Doppler sound cessation, resumption of operculation, or 30 min. Time to Doppler sound cessation or resumption of operculation was recorded. Doppler sound cessation occurred in 7/7 fish in IC (median 0.08, range 0–2.75 min) and 1/7 fish in T (10 min). In T, ICe, and C, 6/7, 7/7, and 7/7 fish, respectively, maintained Doppler sounds to 30 min. All fish in ICe (7/7) and C (7/7) resumed operculation with median (range) times of 22 (7–30) min and 16 (9–29) min from treatment, respectively. Intracardiac KCl at 10 mEq/kg rapidly ceases Doppler sounds and is a successful technique for euthanasia of anesthetized koi. Intracoelomic and topical KCl at 10 mEq/kg were not effective for euthanasia of koi.