The Use of Heart Lung Machine for Cardiac Operations in Small Animals
World Small Animal Veterinary Association World Congress Proceedings, 2004
Schneider K, Ullmann C, Dhein S, Walther T, Kostelka M, Mohr F-W, Oechtering G1
Heart Center Leipzig, Clinic for Cardiac Surgery, Germany; 1University of Leipzig, Clinic for small animals, Germany

Introduction

Although techniques for the perioperative management of patients under open heart surgery with extracorporeal circulation have been established in human, the use of the heart-lung machine to correct heart disease has not been accepted in the veterinary practice, especially in dogs. The most common congenital heart defects in dogs are aortic stenosis (35%), pulmonic stenosis (20%), ventricular septal defect (12%), patent ductus arteriosus (11%), mitral valve dysplasia (8%), tricuspid valve dysplasia (7%) and tetralogy of Fallot (0,6%). However, for most cardiac operations the use of a heart lung machine (HLM) is necessary. The deleterious effects after CPB are haemolysis, low cardiac output, renal failure, cerebral dysfunction, post-perfusion respiratory insufficience. Since the highest sensitivity to HLM-induced insults is found in the brain, we focused on cerebral alterations to optimize HLM for the use in small animals.

Materials and methods

Piglets (n=54, 7-10kg, 3-4 weeks old) were submitted to extracorporeal circulation (ECC) at 25, 50 or 100% of the standard flow rate for 60 min of cardioplegic cardiac arrest. Body temperature was kept at either 18, 25 and 38°C. Routine hemodynamic and functional parameters were measured online until 4 hours of reperfusion. Immunohistology was used to qualify heat shock protein HSP70 level in hippocampus; HPLC was used to quantify jugular venous blood malondialdehyde (MDA) levels as ischemic markers.

Results

Reduced ECC flow led to significant reduction of mean arterial pressure by 79%, reduction of jugular venous saturation by 47%, reduction of carotid blood blow by 92%, Tissue oxygenation index was reduced by 25% while serum lactate was increased by 350%. All these changes were significantly enhanced in the 38°C versus 25°C or 18°C groups. There was a significant increase in HSP70 and MDA in the 25 and 50% flow groups.

Conclusion

It is possible to use ECC in pigs. A reduction in global blood flow during ECC leads to significant biochemical changes in the hippocampus. The lowest cerebral impairment was achieved at 18-25°C with not more than 50% blood flow reduction.

Speaker Information
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K. Schneider
Heart Center Leipzig, Clinic for Cardiac Surgery
Germany


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