Date Published: November 15, 2007
Publisher: BioMed Central
Author(s): Anna H Edner, Görel C Nyman, Birgitta Essén-Gustavsson.
Many colic horses are compromised due to the disease state and from hours of starvation and sometimes long trailer rides. This could influence their muscle energy reserves and affect the horses’ ability to recover. The principal aim was to follow metabolic parameter before, during, and up to 7 days after anaesthesia in healthy horses and in horses undergoing abdominal surgery due to colic.
20 healthy horses given anaesthesia alone and 20 colic horses subjected to emergency abdominal surgery were anaesthetised for a mean of 228 minutes and 183 minutes respectively. Blood for analysis of haematology, electrolytes, cortisol, creatine kinase (CK), free fatty acids (FFA), glycerol, glucose and lactate was sampled before, during, and up to 7 days after anaesthesia. Arterial and venous blood gases were obtained before, during and up to 8 hours after recovery. Gluteal muscle biopsy specimens for biochemical analysis of muscle metabolites were obtained at start and end of anaesthesia and 1 h and 1 day after recovery.
Plasma cortisol, FFA, glycerol, glucose, lactate and CK were elevated and serum phosphate and potassium were lower in colic horses before anaesthesia. Muscle adenosine triphosphate (ATP) content was low in several colic horses. Anaesthesia and surgery resulted in a decrease in plasma FFA and glycerol in colic horses whereas levels increased in healthy horses. During anaesthesia muscle and plasma lactate and plasma phosphate increased in both groups. In the colic horses plasma lactate increased further after recovery. Plasma FFA and glycerol increased 8 h after standing in the colic horses. In both groups, plasma concentrations of CK increased and serum phosphate decreased post-anaesthesia. On Day 7 most parameters were not different between groups. Colic horses lost on average 8% of their initial weight. Eleven colic horses completed the study.
Colic horses entered anaesthesia with altered metabolism and in a negative oxygen balance. Muscle oxygenation was insufficient during anaesthesia in both groups, although to a lesser extent in the healthy horses. The post-anaesthetic period was associated with increased lipolysis and weight loss in the colic horses, indicating a negative energy balance during the first week post-operatively.
An approximately ten-fold higher incidence of anaesthetic-related deaths has been reported in colic horses undergoing emergency abdominal surgery in comparison with healthy horses undergoing elective anaesthetic procedures [1-3]. Attempts have been made in several studies to identify parameters that may be used to predict the probability of survival in colic horses [4-12]. The best predictors seem to be parameters that assess the cardiovascular function of the horse. The progress of different clinical-chemical parameters has been studied in venous or arterial blood during and after anaesthesia in horses subjected to emergency abdominal surgery [9,13-15]. Metabolic changes that occur locally in a muscle can be studied by analysis of muscle biopsy specimens and microdialysis techniques. Studies have shown that anaesthesia in healthy horses is associated with anaerobic metabolism observed as a degradation of adenosine triphosphate (ATP) and creatine phosphate (CP) and production of lactate within the muscle [16,17]. This may be related to general hypoperfusion caused by the anaesthetic agents per se  or to compressive forces, or both restricting local blood perfusion [19,20].
The results from analyses of blood parameters and muscle biopsy samples before, during and up to one week post anaesthesia show that metabolism pre- and post-anaesthesia differs between healthy horses and horses subjected to emergency abdominal surgery. The higher pre-anaesthetic levels of plasma cortisol, FFA, glycerol, glucose and plasma and muscle lactate at START in colic horses suggest a greatly increased sympathetic output, which profoundly affected the metabolic processes with activation of both the carbohydrate and lipid metabolic pathways [27,28].
The surgical colic cases displayed different degrees of metabolic stress with parallel activation of lipolysis and glycolysis and a depletion of muscle energy reserves before anaesthesia. The horses with the most severe pre-anaesthetic metabolic derangements died or were euthanised during anaesthesia or in the recovery box. Anaesthesia and surgery relieved the colic horses from some of the general stress response whereas anaesthesia induced a stress response in the healthy horses. Muscle oxygenation was insufficient during anaesthesia in both groups, with increases in lactate in muscle and plasma, although the levels were higher in the colic horses. The post-anaesthetic period was associated with increased lipolysis and weight loss in the colic horses, indicating a negative energy balance at least during the first week post-operatively.
Att metabolismen är förändrad hos kolikhästen jämfört med den friska hästen är välkänt. De uppvisar ofta förhöjda blodnivåer av bland annat laktat, glukos, fria fettsyror och cortisol vilket tyder på ett stresstillstånd med aktiverad kolhydrat-och fettomsättning samt nedsatt perifer cirkulation. Kolikhästar har markant förhöjd mortalitet i samband med anestesi jämfört med den friska hästen och flera studier har påvisat ett samband mellan laktatnivån i plasma och sannolikheten att dö i samband med anestesi. Det saknas dock studier som närmare studerat metabolismen i hästens största energireservoar, nämligen skelettmuskeln.
The author(s) declare that they have no competing interests.
AE planned the study, carried out the practical work (collecting samples and data) as well as prepared the major part of the manuscript.