Factors influencing aortocaval compression in late pregnancy

Milsom, Ian; Forssman, Lars

doi:10.1016/0002-9378(84)90563-5

Cited by 65 publications

(38 citation statements)

References 13 publications

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“…2 Despite these physiological adaptations, women often experience edaema in late pregnancy, which is in part due to compression of the vena cava by the gravid uterus. 7,8 A common recommendation for reduction of the edaema associated with late gestational pregnancy is to rest in the LLP. [4][5][6] However, few data are available that explore the physiological phenomenon underlying the water and electrolyte excretion induced by resting in the LLP in late pregnancy.…”

Section: Discussionmentioning

confidence: 99%

“…[4][5][6] The rationale is that, in the lateral recumbent position, the gravid uterus releases the peripheral venous return to the central circulation, which improves cardiac output and consequently renal perfusion. 7,8 The aims of the present study were to characterise the renalelectrolyte physiological adaptations when late-pregnant women move from bed rest in the SP to the left lateral position (LLP) and to identify the RAAS and ANP changes that accompany this physiological phenomenon. We hypothesised that the haemodynamically induced RAAS and ANP adaptations are responsible for the alterations in the renal-electrolyte physiological parameters.…”

Section: Introductionmentioning

confidence: 99%

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The haemodynamic, renal excretory and hormonal changes induced by resting in the left lateral position in normal pregnant women during late gestation

Almeida

Pavan

Rodrigues

2009

BJOG

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Objective To characterise the haemodynamic, renal-electrolyte and hormonal parameters in normal near-term pregnancy.Design Observational prospective case-series study.Setting and population Eleven women with normal pregnancies at 35-39 weeks gestation.Methods Following baseline laboratory assessments and placement of a right-atrial catheter, serial measurements were obtained for 2 hours in the supine position (SP) followed by a change to the (LLP) and subsequent observations for 2 hours.Main outcome measures Blood pressure (BP), central venous pressure (CVP), atrial natriuretic peptide (ANP), plasma renin activity (PRA), plasma aldosterone (ALDO), diuresis, creatinine clearance, sodium and potassium excretion.Results In the SP, the subjects' BP remained stable while their CVP decreased. In the LLP, the subjects' systolic and diastolic BP consistently decreased by about 15 mmHg and their CVP increased within the first 60 minutes. ANP levels doubled in the subjects while they rested in the LLP, whereas the subjects' PRA and ALDO levels decreased by half compared with when they rested in the SP. In the LLP, the subjects' creatinine clearance significantly increased by 12% and their sodium excretion and diuresis increased by 38% and 59% respectively.Conclusion Rest in the LLP induces systemic and intra-renal haemodynamic and hormonal changes that may play a central physiological role in the renal excretory response to restore excessive sodium/water retention in late pregnancy.Keywords Atrial natriuretic peptides, blood pressure in pregnancy, gestation, natriuresis, renin-angiotensin-aldosterone system.Please cite this paper as: Almeida F, Pavan M, Rodrigues C. The haemodynamic, renal excretory and hormonal changes induced by resting in the left lateral position in normal pregnant women during late gestation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The haemodynamic, renal excretory and hormonal changes induced by resting in the left lateral position in normal pregnant women during late gestation

Almeida

Pavan

Rodrigues

2009

BJOG

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“…The blood pressure cuff is commonly placed on the uppermost arm because it is more accessible and because of a fear that, if it is on the dependent arm in the lateral position, it will be compressed leading to an inaccurate reading. Studies in nonlabouring women have shown that blood pressure taken in the uppermost arm in the lateral position is lower than that measured while supine [4][5][6][7][8][9][10][11].…”

Section: Discussionmentioning

confidence: 99%

“…When noninvasive methods are used in this position, however, the arms are at a different vertical level with respect to the heart. The uppermost arm has always been found to have a blood pressure lower than that measured while supine [4][5][6][7][8][9][10][11] or semirecumbent [8]. When blood pressure values have been reported in the dependent arm, they are usually similar to those in the supine [8][9][10][11] or semirecumbent [8] positions.…”

Section: Discussionmentioning

confidence: 99%

Reporting of ‘hypotension’ after epidural analgesia during labour

Kinsella

Black

1998

Anaesthesia

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SummaryWe studied 20 women in labour to see how reporting 'hypotension' after obstetric epidural analgesia is affected by position of the blood pressure cuff and baseline definition. Blood pressure was recorded from both arms simultaneously while the woman was semirecumbent and then in the left lateral position. Three readings were then taken after epidural bupivacaine, one left lateral and the remainder right lateral. Before the epidural, blood pressure in the dependent arm in the lateral position was similar to blood pressure in either arm in the semirecumbent position and an average of 10 mmHg (systolic) and 14 mmHg (diastolic) higher than blood pressure in the uppermost arm (p Յ 0.00005). This difference persisted in both lateral positions as epidural analgesia became established. Choosing different definitions of hypotension, baselines and arm to measure blood pressure resulted in 'hypotension rates' between 0% and 75%. For blood pressure measurement in the lateral position, the blood pressure cuff should be placed on the dependent arm. Hypotension after epidural analgesia during labour is of importance because of the direct link with impairment of uteroplacental blood supply [1]. Hypotension is often attributed to the sympathetic blocking effect of local anaesthetics, but has also been noted after spinal opioids, most of which do not have such an effect. For example, Ducey et al. [2] reported that 46% of women receiving a combination of spinal fentanyl and morphine for analgesia developed hypotension, defined by them as a decrease of more than 20% from baseline. This is considerably more frequent than might be expected after epidural analgesia and is hard to explain as a pharmacological effect.There are two alternative hypotheses to explain why hypotension might be so commonly diagnosed after regional analgesia during labour. Blood pressure increases with the onset of labour as a consequence of painful contractions, and the use of a prelabour value as a baseline has been found to influence the hypotension rate [2,3]. The lateral position is often used in labour to avoid the maternal and fetal effects of supine aortocaval compression, and there must inevitably be a hydrostatic difference in the blood pressure recorded between the uppermost and dependent arms. The blood pressure cuff is commonly placed on the uppermost arm because it is more accessible and because of a fear that, if it is on the dependent arm in the lateral position, it will be compressed leading to an inaccurate reading. Studies in nonlabouring women have shown that blood pressure taken in the uppermost arm in the lateral position is lower than that measured while supine [4][5][6][7][8][9][10][11].We investigated these two influences on recording of blood pressure and hypotension rate after epidural analgesia during labour. Methods

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“…The greater fall in cardiac vagal activity and the greater rise in cardiac sympathetic activity in the supine and right lateral decubitus positions in late pregnancy can be explained by aortocaval compression due to the effect of the gravid uterus. Because of the anatomical position of the inferior vena cava and the abdominal aorta, the enlarged uterus can exert a greater compression on these vessels during supine and right lateral decubitus positioning than in the left lateral decubitus position, thus reducing the venous return and cardiac output [8]. To compensate for the decrease in venous return and cardiac output, sympathetic tone is enhanced and the vagal tone is suppressed in these positions.…”

Section: Discussionmentioning

confidence: 99%

The effect of position on autonomic nervous activity in late pregnancy

et al. 1997

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SummaryWe investigated the effect of three different recumbent positions on autonomic nervous activity in late pregnancy. Thirty pregnant and 24 nonpregnant aged-matched women were studied, and measures of heart rate variability in both time and frequency domains were compared using supine, right and left lateral decubitus positions. In the nonpregnant women, the normalised highfrequency power was greatest in the right lateral decubitus position. In the pregnant women, the normalised high-frequency power was lowest and the low/high-frequency power ratio was greatest in the supine position. Both the percentage decrease of normalised high-frequency power and the percentage increase of low/high-frequency power ratio in the supine and right lateral positions were greater than those in the left lateral position. For women in late pregnancy, the left lateral decubitus position may be beneficial because cardiac vagal activity is least suppressed and cardiac sympathetic activity is least enhanced. Aortocaval compression might be the mechanism underlying the change in cardiac autonomic nervous activity when supine and right lateral decubitus positions are assumed in late pregnancy.Keywords Sympathetic nervous system. Heart; pulse rate, variability. We previously demonstrated that the right lateral decubitus position is associated with the highest vagal tone when three recumbent positions were compared in young normal subjects and recommended this position for routine recumbency in this group [1]. In contrast, Mills and Chaffe observed the sleeping positions adopted by pregnant women of more than 30 weeks gestation and found that the majority adopted a sleeping position that reduced the likelihood of aortocaval compression, with 77% adopting a left tilt, 21% a right tilt and only 2% choosing the supine position [2]. Avoidance of positions which may produce aortocaval compression is desirable because of the higher susceptibility to hypotension from factors that impair normal circulatory control such as regional anaesthesia, labour, fetal blood sampling or general anaesthesia [3,4]. The left lateral decubitus position has been recommended during blood pressure measurement in pregnant women, especially in late pregnancy, by the British Hypertension Society, to minimise the effects of aortocaval compression [5].The aim of this study was to investigate the effect of different recumbent positions on autonomic nervous activity in nonpregnant women and those in late pregnancy by using spectral heart rate variability (HRV) analysis.

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Factors influencing aortocaval compression in late pregnancy

Cited by 65 publications

References 13 publications

The haemodynamic, renal excretory and hormonal changes induced by resting in the left lateral position in normal pregnant women during late gestation

The haemodynamic, renal excretory and hormonal changes induced by resting in the left lateral position in normal pregnant women during late gestation

Reporting of ‘hypotension’ after epidural analgesia during labour

The effect of position on autonomic nervous activity in late pregnancy

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