Hyperkalemic periodic paralysis episode during halothane anesthesia in a horse.

The research article discusses a case where a 7-month-old Quarter Horse suffered a hyperkalemic periodic paralysis episode during a surgical procedure, which was induced by halothane anesthesia, and was successfully treated with various interventions, including change of intravenous fluids and medications.

Case Overview

• The subject of the study was a 7-month-old Quarter Horse filly, who was brought for surgical repair of a right olecranon fracture.
• The horse was confirmed to be heterozygous for hyperkalemic periodic paralysis via DNA testing. This genetic disorder is characterized by episodes of muscle weakness or paralysis, often triggered by certain medications, stress, or rest after exercise.

Anesthetic Protocol and Complications

• Anesthesia for the surgery was administered using xylazine hydrochloride, guaifenesin, ketamine hydrochloride, and halothane.
• About two and a half hours after the induction of anesthesia, the horse exhibited signs of myotonia (muscle stiffness), muscle fasciculations (muscle twitches), and sweating. These symptoms were accompanied by an elevated serum potassium concentration and associated electrocardiographic changes — indicative of a hyperkalemic periodic paralysis episode.

Treatment and Outcome

• The interventions deemed necessary for treatment consisted of intermittent positive-pressure ventilation to assist breathing, switching the intravenous fluids from lactated Ringer’s solution to 0.9% NaCl solution, and administering calcium gluconate, glycopyrrolate, dopamine, and sodium bicarbonate for various physiological support.
• The clinical signs began to resolve as the horse’s potassium concentrations returned to a normal range. This suggests that the interventions were successful in treating this episode of hyperkalemic periodic paralysis in the horse.

Significance of the Study

• The study highlights the potential risk of hyperkalemic periodic paralysis episodes in the administration of halothane anesthesia in horses, particularly for those identified with a genetic predisposition.
• This study emphasizes the importance of knowing the genetic profile of animals before anesthetic protocols are determined to avoid such incidents.
• Additionally, early diagnosis and immediate intervention using appropriate and specific treatments can lead to successful outcomes in these potentially life-threatening situations.