Effects of Anesthesia and Elective Ovariectomy on Serial Blood Gases and Lactates in Yellow Perch and Walleye Pike: Can Lactate Predict Postoperative Survival?
1Special Species Health Service, Department of Surgical Science, School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA; 2Conservation Health Consortium, School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA; 3Animal Health Center, Milwaukee County Zoo, Milwaukee, WI, USA
Blood gases and lactate have been used as indicators of anesthetic depth and physiologic distress in many species, including fish.1-4 Blood lactate has been evaluated in fish under stress-induced or toxic experimental conditions.1,4 However, there has been no evaluation of blood lactate in fish undergoing clinical procedures nor correlation with postoperative survival. We hypothesized that serial blood lactate concentrations could predict postsurgical survival in fish.
Adult female yellow perch (Perca flavescens) (n=8) and walleye pike (Sander vitreus) (n=4) were anesthetized using MS-222 (induction at 200 mg/L and maintenance at 50–150 mg/L) on a recirculating anesthesia machine for elective ovariectomy. Blood samples were collected via repeated phlebotomy of the caudal vein of each fish at three-time points; preanesthesia, following anesthetic induction (presurgical), and postsurgically. A handheld clinical analyzer (i-STAT®; cartridges CG4+) was used to measure mixed venous/arterial PCO2, PO2, pH, and lactate. Fish were monitored for 2 weeks postoperatively to determine short-term survival, during which time two perch but no walleye died.
For all fish combined, mean PO2 increased from preanesthesia to postsurgery, while PCO2 increased from preanesthesia to presurgery and then decreased postsurgically. Mean pH decreased with anesthesia but returned to preanesthetic levels postsurgery. Mean lactate (±SD) increased from preanesthesia (1.3±1.3 mmol/L) to presurgery (7.3±1.8 mmol/L) but decreased after surgery (6.7±2.3 mmol/L). Surviving perch and walleye had a mean postsurgical lactate of 5.7±1.2 and 6.0±1.9 mmol/L, respectively, whereas the two perch that died had postsurgical lactates >10 mmol/L (10.6 and 10.7 mmol/L). The first perch that died shortly after surgery had a soft-tissue sarcoma, whereas the second perch died from an infarcted tail 10 days postoperatively.
Early results of this study suggest that persistently elevated blood lactate concentrations (>10 mmol/L) may be predictive of poor short-term postsurgical survival in yellow perch and walleye pike.
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