Age-related differences in the cardiovascular responses to haemorrhagic shock in rats

The cardiovascular responses to haemorrhagic shock were studied in male Sprague-Dawley rats of different age groups, ranging from 6-15 weeks (body weight 250-460 g). Haemorrhagic shock was induced by bleeding (2% body weight), under urethane anaesthesia, from the cannulated femoral artery at a rate of 1 ml/min. It was found that the younger rats had significantly smaller values of left ventricular pressure and dLVP/dtmax following haemorrhage and a greater mortality rate. Older animals exhibited significantly greater falls in blood pressure and pulse rate during the bleeding procedure, and slower recovery in these parameters after the bleeding was stopped. However, these rats had a significantly higher left ventricular pressure and dLVP/dtmax following haemorrhage, and a markedly lower mortality rate. The findings demonstrate the existence of age-related cardiovascular responses to haemorrhagic shock in rats.