Comparative efficacy of tricaine methanesulfonate and clove oil for use asanesthetics in red pacu (Piaractus brachypomus)

Objective-To compare the anesthetic efficacy and physiologic changes associ ated with exposure to tricaine methanesulfonate and clove oil (100% eugenol ). Animals-15 adult cultured red pacu (Piaractus brachypomus). Procedure-Fish were exposed to each of 6 anesthetic concentrations in a wit hin-subjects complete crossover design. Stages of anesthesia and recovery w ere measured, and physiologic data were collected before and during anesthe sia. Results-interval to induction was more rapid and recovery more prolonged in fish exposed to eugenol, compared with those exposed to tricaine methanesu lfonate. The margin of safety for eugenol was narrow, because at the highes t concentration, most fish required resuscitation. Mixed venous-arterial Po -2 consistently decreased with anesthesia, while Pco(2) consistently increa sed with anesthesia in all fish regardless of anesthetic agent. The increas e in Pco(2) was accompanied by a decrease in pH, presumably secondary to re spiratory acidosis, Anesthesia was associated with increased blood glucose, potassium, and sodium concentrations as well as Hct and hemoglobin. Fish a nesthetized with eugenol were more likely to react to a hypodermic needle p uncture than fish anesthetized with tricaine methanesulfonate. Conclusions and Clinical Relevance-Anesthesia induced with tricaine methane sulfonate or eugenol contributes to hypoxemia, hypercapnia, respiratory aci dosis, and hyperglycemia in red pacu. Similar to tricaine methanesulfonate, eugenol appears to be an effective immobilization compound, but eugenoi is characterized by more rapid induction, prolonged recovery, and a narrow ma rgin of safety. Care must be taken when using high concentrations of eugeno l for induction, because ventilatory failure may occur rapidly. In addition , analgesic properties of eugenol are unknown.