Preeclampsia is not associated with elevated muscle sympathetic reactivity

To determine whether increased chemoreflex tonic activity is associated with augmented muscle sympathetic nervous system activity (MSNA) in women diagnosed with preeclampsia. Women with preeclampsia (n = 19; 32 +/- 5yr old, 31 +/- 3 wk of gestation) were matched by age and gestational age with pregnant women (controls, n = 38, 32 +/- 4yr old, 31 +/- 4 wk gestation; 2:1 ratio). MSNA (n = 9 preeclampsia) was assessed during baseline, peripheral chemoreflex deactivation (hyperoxia), and a cold pressor test (CPT). Baroreflex gain and diastolic blood pressure at which there is a 50% likelihood of MSNA occurring (T50) and plasma noradrenaline concentrations were measured. Baseline mean arterial pressure (MAP: 106 +/- 11 vs. 87 +/- 10 mmHg, P < 0.0001), noradrenaline concentrations (498 +/- 152 pg/mL vs. 326 +/- 147, P = 0.001), and T50 (79 +/- 7 vs. 71 +/- 9 mmHg, P = 0.02) were greater in women with preeclampsia than in controls. However, baseline MSNA (burst incidence [BI]: 41 +/- 16 vs. 45 +/- 13 bursts/ 100 hb, P = 0.4) was not different between groups. Responses to hyperoxia (Delta BI 5 +/- 7 vs. 1 +/- 8 bursts/100 hb, P = 0.1; Delta MAP -1 +/- 3 vs. 2 +/- 3 mmHg, P = 0.7) and CPT (Delta BI 15 +/- 7 vs. 12 +/- 11 bursts/100 hb, P = 0.6; Delta MAP 10 +/- 4 vs. 12 +/- 11 mmHg, P = 0.6) were not different between groups. Our findings question the assumption that increased MSNA contributes to hypertension in women with preeclampsia. The chemoreflex does not appear to contribute to an increase in MSNA in women with preeclampsia. NEW & NOTEWORTHY We wanted to determine whether increased chemoreflex tonic activity is associated with augmented muscle sympathetic nervous system activity (MSNA) in women diagnosed with preeclampsia. The chemoreflex does not contribute to increased MSNA in women with preeclampsia. Our data also challenge the belief that preeclampsia is associated with sympathetic neural hyperactivity. Thus, targeting sympathetic neural hyperactivity as therapeutic strategy is unlikely to be the most efficacious approach to treatment and management.

Automated summary

This study found that women with preeclampsia had higher baseline mean arterial pressure, noradrenaline concentrations, and MSNA occurrence probability compared to controls, but no significant difference in baseline MSNA levels between the two groups. The chemoreflex does not contribute to increased MSNA in women with preeclampsia.