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Age dependent effects of haemorrhage on the arterial baroreflex control of heart rate 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.1019.2
Subject(s) - baroreflex , heart rate , blood pressure , medicine , anesthesia , mean arterial pressure , cardiology
Previously, we showed that arterial pressure decreased after moderate haemorrhage in conscious lambs, whereas a compensatory increase in heart rate occurred only in newborns. These findings provided evidence to suggest an age‐dependent effect of haemorrhage on the arterial baroreflex control of heart rate. Therefore, in the present study, the arterial baroreflex was assessed in conscious lambs aged 14±1 days (G I, N=4) and 43±7 days (G II, N=6) before (control, C) and at 30 and 60 min after haemorrhage (30% of calculated blood volume). The following parameters governing the arterial baroreflex were evaluated: Heart rate range ( P1 ), slope coefficient ( P2 ), systolic arterial pressure at midpoint ( P3 ), minimum HR ( P4 ), and maximum gain ( G max ). Values are mean±SEM; *p<0.05 compared with C; †p<0.05 compared with G I. Predominant effects of haemorrhage were: a decrease in P1 which was greater in G I than G II, and a decrease in G max which was greater in G II than G I. Therefore, severe haemorrhage alters several parameters governing the arterial baroreflex control of heart rate, these effects being developmentally regulated. This research was supported by the Canadian Institutes of Health Research (CIHR).