title: Influence of age on the cardiovascular response during graded haemorrhage in anaesthetized rats.
abstract: The present study was designed to follow the cardiovascular response to graded haemorrhage in two groups of adult rats of different ages. Group A (n = 10) had a mean body weight (bwt) of 655 g (50 weeks old) and group B (n = 10) had a mean bwt of 250 g (12 weeks old). After induction of anaesthesia, the carotid artery was cannulated for continuous intra-arterial blood pressure monitoring and for controlled haemorrhage. 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) fell by 4-9 mm Hg each time 5% TBV was removed in both groups, and at the end of the study the MAP was comparable in the two groups (34 +/- 10 mm Hg in group A and 28 +/- 8 mm Hg in group B). There were no significant changes in heart rate (HR) in the young animals during haemorrhage, while there was a significant drop in heart rate in the older animals when blood loss exceeded 15% of TBV (P < 0.05). A significant difference 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 although the hypotension induced by graded haemorrhage was similar in young 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.
authors.affiliation: Department of Plastic Surgery, University of Berne, Inselspital, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Banic
authors.forename: G H
authors.initials: GH
authors.lastname: Sigurdsson
authors.forename: A M
authors.initials: AM
authors.lastname: Wheatley
mesh_terms: D000375:Aging / Q000502:physiology*; D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume; D002320:Cardiovascular Physiological Phenomena; D006339:Heart Rate / Q000502:physiology; D008297:Male; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012771:Shock, Hemorrhagic / Q000503:physiopathology*