Introduction

Cardiac troponin I (cTnI), a cardiac marker which is released into the blood stream when membranes of myocytes are damaged, is both sensitive and specific for cardiac myocyte ischaemia. General anaesthesia results in important cardiovascular changes with the risk of a decreased oxygen delivery to the myocardium. An increase in cTnI was already reported in dogs after general anaesthesia.

Aim

The aim of this study was to compare cTnI levels before and 12 hours after general anaesthesia.

Methods

Eighteen client-owned dogs (ASA I and II), presented for orthopedic surgery necessitating general anaesthesia, were enrolled in the study after gaining owner consent. A venous blood sample was taken, centrifuged within 30 minutes and the serum was stored in a 1 mL eppendorf tube at -80°C until analysis for cTnI concentration, before anaesthesia. After placing an intravenous catheter into the cephalic vein, the patient was premedicated with 0.5 mg/kg methadone IV. Anaesthesia was induced with 0.2 mg/kg diazepam IV and propofol 6 mg/kg IV administered to effect . After endotracheal intubation, anaesthesia was maintained using isoflurane (1% end-tidal concentration) in oxygen in combination with a continuous rate infusion of fentanyl (10 µg/kg/h). Arterial haemoglobin oxygen saturation (SpO₂) and pulse rate were monitored by pulse oximetry and systolic arterial blood pressure (SAP) by Doppler. Respiratory rate, electrocardiogram, end-tidal carbon dioxide and inspiratory and end-tidal isoflurane concentration were continuously monitored. Twelve hours after discontinuation of anaesthesia, a second blood sample was drawn from the jugular vein and processed in the same way as the pre-anaesthetic sample. Serum cTnI concentrations were measured using a chemiluminescent microparticle immunoassay (Architect STAT Troponin-I, Abbott Laboratories) designed for use with the Architect i2000 (Abbott Laboratories), with a detection limit of 0.01 ng/mL.

Results

An increase in the cTnI concentration was seen in ten dogs (55%), two dogs showed a decrease and in the remaining 6 dogs no change was observed.

Conclusion

In this study in healthy dogs, a frequency of increased cTnI of 55% was observed. Since determination of cTnI is currently one of the most reliable methods to assess myocardial damage, the importance of an optimal myocardial oxygen delivery during general anaesthesia should be emphasized.