Changes in maternal heart dimensions and plasma atrial natriuretic peptide levels in the early puerperium of normal and pre‐eclamptic pregnancies

Abstract

Objective To measure plasma atrial natriuretic peptide (ANP) in relation to maternal haemodynamics and body fluid balance in the early puerperium following uncomplicated pregnancy and pre‐eclampsia. Design A longitudinal study from late pregnancy and into the early postpartum period (days 1 to 3 and days 4 to 6) compared with nonpregnant controls. Subjects Eleven women with uncomplicated pregnancies, 12 women with pre‐eclampsia and 12 healthy, nonpregnant women. Main outcome measures Maternal heart dimensions determined by M‐mode echocardiography, concentrations of ANP, and daily urine output and sodium excretion. Results After delivery increases in left atrial dimensions, represented as mean (SEM), from 33.2 (1–6) to 37.7 (1.7) mm and ANP levels from 7.9 (1.1) to 19.0 (2.7) pmol/L were observed at 1–3 days postpartum in normal pregnant women, but we were not able to demonstrate a significant increase in diuresis and natriuresis. In the third trimester left atrial dimensions (38.4 (1.2) mm) and ANP levels (15.4 (2.2) pmol/L) were greater in pre‐eclampsia. ANP levels rose further in pre‐eclamptic women in the early puerperium (27.4 (7.4) pmol/L) with an increase in diuresis and natriuresis, while left atrial dimensions did not change significantly (39.4 (1.7) mm). A pericardial effusion was found in 11 pre‐eclamptic but in only three healthy pregnant women. Conclusions A concommitant increase in left atrial dimensions and ANP in the early puerperium following uncomplicated pregnancies is consistent with the mechanism of atrial stretch as a stimulus for ANP release, although the biological significance of this finding remained unclear. A significantly higher release of ANP in the early puerperium after pregnancies complicated by pre‐eclampsia may be a mechanism which promotes the renal elimination of excessive body fluids and sodium.

Normal urine output after elective caesarean section: an observational study

“…The median (range) for parity was 1 (0-4). Thirty-eight (64%) operations were for previous caesarean section, 13 (22%) for breech presentation and 8 (14%) for other reasons. Spinal anaesthesia was used in 39 (66%) women and combined spinal-epidural in 20 (34%).…”

“…Oxytocin infusions were used prophylactically at obstetric request in 45 women (75%), at a standardised dose of 10 IU in 125 mL every hour for the first 4 h. Urine output during the first 6 h and at 12 and 18 h, according to body weight, are shown in Table 1, for the whole group and according to whether oxytocin infusion was used. Median (95% CI) 24-h intravenous fluid input were 2.8 (1.8-4.3) L. Median (IQR [range]) times to first oral fluids and cessation of intravenous fluid were 3 (2-4 [2][3][4][5][6][7][8][9][10][11]) h and 6 (5-7 [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]) h. Mean (±SD) haemoglobin concentrations on the day of surgery and the following day were 11.9 (±1.2) and 10.5 (±1.0) g/dL, respectively. The mean (±SD) drop in haemoglobin concentration with or without oxytocin infusion was 1.4 (±0.9) and 1.4 (±0.4) mg/dL respectively; no patient received blood products.…”

“…The investigators found no difference in urine output between the third trimester and days 1-3 post partum in normal pregnancy, despite increases in atrial size and concentrations of atrial natriuretic peptide, although they did note a statistically significant post partum increase in diuresis and natriuresis in preeclampsia. 13 In the other study, 207 women had a caesarean section under general anaesthesia and the effects of early oral intake were examined. From their data, we calculated an hourly urine output during the first 48 h to be approximately 0.8 mL kg À1 h À1 , similar to our own findings.…”

Right atrial dimension-pressure relation during volume expansion is unaltered by pregnancy in the rat

“…Left atrial dimension has been measured and increases ϳ16%, peaking at 28 wk of pregnancy in humans. A further increase in dimension occurs in the first few days postpartum (15,16). We showed a 26% increase in RAD at full-term pregnancy in rats, in which the maximum plasma volume increase is slightly higher than in humans.…”

The fluid balance observed postnatally on normal pregnancies, pregnancies with preeclampsia, and on pregnancies with oedema and proteinuria

“…The first was conducted by Pouta et al 20 in which women with normal pregnancy and women with preeclampsia were compared with non-pregnant women. The researchers found no particular difference in the urine output in the third trimester of pregnancy, compared to 1-3 days postpartum in normal pregnancy, despite an increase in atrial size and in the concentration of Atrial Natriuretic Peptide (ANP).…”