Pressor, heart rate and plasma catecholamine responses to noradrenaline in pregnant and nonpregnant women.
OBJECTIVE
To study cardiovascular responses to noradrenaline during early pregnancy.


METHODS
Administration of incremental intravenous infusions of noradrenaline under basal conditions.


METHODS
University Hospital, Nottingham.


METHODS
Nineteen women admitted for termination of pregnancy in first or second trimester and 18 nonpregnant women as control subjects.


METHODS
Recordings of blood pressure and heart rate responses during the infusion of noradrenaline. Blood samples taken before, during and after the infusion.


METHODS
Evoked responses of systolic and diastolic blood pressure and heart rate at steady state during the noradrenaline infusion. Plasma catecholamine concentrations measured by high performance liquid chromatography.


RESULTS
There were no significant differences between the evoked pressor responses to noradrenaline in pregnancy compared to the nonpregnant state, but there was a lesser bradycardia in response to a standardised change in blood pressure. Neither basal plasma catecholamine concentrations nor those achieved during infusion of noradrenaline differed between pregnant and nonpregnant women. Thirty minutes after discontinuance of the infusion there was a persistent elevation of heart rate in all women, although plasma catecholamine concentrations had returned to basal levels. In pregnant women, systolic and diastolic blood pressures were also elevated at this time, compared to preinfusion levels.


CONCLUSIONS
Cardiovascular regulatory mechanisms are altered in pregnancy with a diminution in the bradycardic response to a pressor challenge evoked by noradrenaline and a delayed recovery from that challenge.
Ramsay
M M
MM
Department of Obstetrics, University of Nottingham Medical School, Queen's Medical Centre, UK.
Broughton Pipkin
F
F
Rubin
P C
PC
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D009638:Norepinephrine / Q000494:pharmacology*; D011247:Pregnancy / Q000097:blood / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology
D002395:Catecholamines; D009638:Norepinephrine