A tale of IVC, CO & the magical 15 degrees…

Lees MM, Taylor SH, Scott D & Kerr MG. A study of cardiac output at rest throughout pregnancy. BJOG: An International Journal of Obstetrics & Gynaecology 1967; 74: 319-328.

RHH Journal Club. December 22nd, 2012. Dr Maneka Braganza

No free full-text available

To describe the overall pattern of change in cardiac output during pregnancy .

Primary Aim:

To describe the overall pattern of change in cardiac output during pregnancy with particular focus on a)the time of onset of rise in cardiac output

b)the time at which it reaches its maximum value

c)the magnitude of this rise

d)its behaviour after it attains this peak value

Study design:

Observational, longitudinal single centre study

Methodology:

Population

Healthy, normotensive primigravidae with uncomplicated preganacies.

Five (from original eleven) completed all three sets of measurements.

  • 1st trimester (11th-13th week) – 11 initial patients studied
  • 2nd trimester (24th-27th week) – 8 patients studied (3 previous data sets ‘unsatisfactory’)
  • 3rd trimester (34th-37th week) – 5 patients studied (3 more data sets ‘unsatisfactory’)

Addition of another nine, isolated third trimester (34th-term)data sets from previously unstudied women into final analysis.

Intervention

  • Fifteen separate measurement of cardiac output at rest using the indicator dilution technique were made in each trimester.
  • Data sets consisted of five readings in a right lateral position, five readings supine and a further five reading right lateral

Control

Five completed measurement sets acted as their own controls (longitudinal study design)

Outcome

Data on MAP, CO, HR and stroke volume changes in 1st, 2nd and 3rd trimester of pregnancy

Validity

  • Single centre, small study with few numbers.
  • No pre-pregnancy or post pregnancy data available.
  • Attempted accurate CO measurements using upto date technology in a protocoled manner while allowing for both beat to beat variations in an individual (five measurements made each time) and variations between individuals (longitudinal study design)

Results

  • Maximum CO rise occurs during the 1st trimester
  • CO rises by 30-40%
  • Importance of IVC compression on CO in the supine position at term

Conclusions

Experimental basis for our understanding of cardiac physiology in pregnancy and importance of left lateral tilt in third trimester.

 

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