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Age‐dependent cardiovascular responses to severe haemorrhage in conscious lambs
Author(s) -
Samhan Mohamed A,
Qi Wei,
Smith Francine G
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.794.1
Subject(s) - medicine , mean arterial pressure , blood pressure , heart rate , hemodynamics , anesthesia , cardiology
The present study was designed to investigate cardiovascular responses to severe haemorrhage (exceeding the critical point at which compensatory mechanisms fail) in two age groups of conscious lambs (Group I: 1‐2 weeks, N=5; group II: 6‐7 weeks, N=6). Mean arterial pressure (MAP), systolic and diastolic pressures (SAP, DAP), heart rate (HR) and renal blood flow (RBF) were measured for 20 min before (Control, C) and after a fixed haemorrhage of 30% of calculated blood volume. After haemorrhage in group I lambs, MAP decreased from 75±5 [SD] (C) to 55±8 mmHg at 5 min, returning to 61±6 mmHg at 20 min, while in group II lambs, MAP decreased further from 74±4 (C) to 38±7 mmHg at 5 min, returning to 55±6 mmHg at 20 min. The fall in SAP 5 min after haemorrhage was also greater in group II lambs (104±8 (C) to 65±15 mmHg) than in group I lambs (110±14 (C) to 91±8 mmHg), whereas DAP followed changes in MAP in both groups. HR increased in group I lambs from 164±43 (C) to 193±45 at 5 min, decreasing thereafter, whereas in group II lambs, HR was unaltered from 119±20 (C). After haemorrhage, RBF fell to zero at 5 min in both groups, returning towards C at 20 min. These results provide new evidence that the cardiovascular responses to severe haemorrhage are developmentally regulated. Mechanisms underlying these differential responses are not yet known. This research was supported by the Canadian Institutes of Health Research (CIHR).