A. Banic et al., INFLUENCE OF AGE ON THE CARDIOVASCULAR-RESPONSE DURING GRADED HEMORRHAGE IN ANESTHETIZED RATS, Research in experimental medicine, 193(5), 1993, pp. 315-321
The present study was designed to follow the cardiovascular response t
o graded haemorrhage in two groups of adult rats of different ages. Gr
oup A (n = 10) had a mean body weight (bwt) of 655 g (50 weeks old) an
d group B (n = 10) had a mean bwt of 250 g (12 weeks old). After induc
tion of anaesthesia, the carotid artery was cannulated for continuous
intra-arterial blood pressure monitoring and for controlled haemorrhag
e. Five per cent of the total blood volume (TBV) was removed every 15
min until a maximum of 50% was reached. Mean arterial pressure (MAP) f
ell by 4-9 mm Hg each time 5% TBV was removed in both groups, and at t
he end of the study the MAP was comparable in the two groups (34 +/- 1
0 mm Hg in group A and 28 +/- 8 mm Hg in group B). There were no signi
ficant changes in heart rate (HR) in the young animals during haemorrh
age, while there was a significant drop in heart rate in the older ani
mals when blood loss exceeded 15% of TBV (P < 0.05). A significant dif
ference was also observed in HR between the two groups of animals with
blood loss in excess of 20% TBV (P < 0.05). It was concluded that alt
hough the hypotension induced by graded haemorrhage was similar in you
ng and old rats, the older animals were less able to maintain their HR
, probably as a consequence of age- and anaesthetic-related changes in
sympathetic activity.