-Muscle sympathetic nerve activity is increased during normotensive pregnancy while mean arterial pressure is maintained or reduced, suggesting baroreflex resetting. We hypothesized spontaneous sympathetic baroreflex gain would be reduced in normotensive pregnant women relative to nonpregnant matched controls. Integrated muscle sympathetic burst incidence and total sympathetic activity (microneurography), blood pressure (Finometer), and R-R interval (ECG) were assessed at rest in 11 pregnant women (33 Ϯ 1 wk gestation, 31 Ϯ 1 yr, prepregnancy BMI: 23.5 Ϯ 0.9 kg/m 2 ) and 11 nonpregnant controls (29 Ϯ 1 yr; BMI: 25.2 Ϯ 1.7 kg/m 2 ). Pregnant women had elevated baseline sympathetic burst incidence (43 Ϯ 2 vs. 33 Ϯ 2 bursts/100 heart beats, P ϭ 0.01) and total sympathetic activity (1,811 Ϯ 148 vs. 1,140 Ϯ 55 au, P Ͻ 0.01) relative to controls. Both mean (88 Ϯ 3 vs. 91 Ϯ 2 mmHg, P ϭ 0.4) and diastolic (DBP) (72 Ϯ 3 vs. 73 Ϯ 2 mmHg, P ϭ 0.7) pressures were similar between pregnant and nonpregnant women, respectively, indicating an upward resetting of the baroreflex set point with pregnancy. Baroreflex gain, calculated as the linear relationship between sympathetic burst incidence and DBP, was reduced in pregnant women relative to controls (Ϫ3.7 Ϯ 0.5 vs. Ϫ5.4 Ϯ 0.5 bursts·100 heart beats Ϫ1 ·mmHg Ϫ1 , P ϭ 0.03), as was baroreflex gain calculated with total sympathetic activity (Ϫ294 Ϯ 24 vs. Ϫ210 Ϯ 24 au·100 heart beats Ϫ1 ·mmHg Ϫ1 ; P ϭ 0.03). Cardiovagal baroreflex gain (sequence method) was not different between nonpregnant controls and pregnant women (49 Ϯ 8 vs. 36 Ϯ 8 ms/mmHg; P ϭ 0.2). However, sympathetic (burst incidence) and cardiovagal gains were negatively correlated in pregnant women (R ϭ Ϫ0.7; P ϭ 0.02). Together, these data indicate that the influence of the sympathetic nervous system over arterial blood pressure is reduced in normotensive pregnancy, in terms of both long-term and beat-to-beat regulation of arterial pressure, likely through a baroreceptor-dependent mechanism. pregnancy; baroreflex control; blood pressure; sympathetic nerve activity PREGNANCY IS A MAJOR PHYSIOLOGICAL STRESSOR, necessitating significant cardiovascular adaptations to support the healthy development of fetus and mother. Hemodynamic adaptations that occur during normotensive pregnancies are characterized by systemic vasodilation concomitant with elevations in cardiac output and blood volume, resulting in a curvilinear decrease in mean arterial pressure (MAP) (6). This drop in mean arterial pressure has been linked to elevated risk of syncope and presyncope in pregnant women relative to nonpregnant women (15, 25). Conversely, up to 8% of all pregnancies result in the de novo development of acute hypertension, including gestational hypertension and preeclampsia (48). These disorders are associated with significant increases in maternal-fetal morbidity and mortality (43,53,57), and moreover, women who develop maternal hypertensive disorders have an elevated lifelong risk of developing cardiovascular disease (53). These pregnanc...
ObjectiveThe main objectives of this study were to synthesise and compare pandemic preparedness strategies issued by the federal and provincial/territorial (P/T) governments in Canada and to assess whether COVID-19 public health (PH) measures were tailored towards priority populations, as defined by relevant social determinants of health.MethodsThis scoping review searched federal and P/T websites on daily COVID-19 pandemic preparedness strategies between 30 January and 30 April 2020. The PROGRESS-Plus equity-lens framework was used to define priority populations. All definitions, policies and guidelines of PH strategies implemented by the federal and P/T governments to reduce risk of SARS-CoV-2 transmission were included. PH measures were classified using a modified Public Health Agency of Canada Framework for Canadian Pandemic Influenza Preparedness.ResultsA total of 722 COVID-19 PH measures were issued during the study period. Of these, home quarantine (voluntary) (n=13.0%; 94/722) and retail/commerce restrictions (10.9%; n=79/722) were the most common measures introduced. Many of the PH orders, including physical distancing, cancellation of mass gatherings, school closures or retail/commerce restrictions began to be introduced after 11 March 2020. Lifting of some of the PH orders in phases to reopen the economy began in April 2020 (6.5%; n=47/722). The majority (68%, n=491/722) of COVID-19 PH announcements were deemed mandatory, while 32% (n=231/722) were recommendations. Several PH measures (28.0%, n=202/722) targeted a variety of groups at risk of socially produced health inequalities, such as age, religion, occupation and migration status.ConclusionsMost PH measures centred on limiting contact between people who were not from the same household. PH measures were evolutionary in nature, reflecting new evidence that emerged throughout the pandemic. Although ~30% of all implemented COVID-19 PH measures were tailored towards priority groups, there were still unintended consequences on these populations.
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