Guess Lecturer - A Good Pregnancy Flashcards
State the cardiac output equation, and define each term.
CO = SV x HR
CO is the amount of blood pumped out of heart in one minute.
SV is the amount of blood pumped out of LV in one beat
What is meant by ‘term’?
Ready to give birth, 39-41 weeks
During pregnancy, is there increased or decreased vascular resistance? Why?
Peripheral vasodilation causes decreased vascular resistance. Mediated by endothelium-dependent factors e.g. NO and PGI2
State the equation that links cardiac output and total peripheral resistance together.
MAP (mean arterial pressure) = CO x TPR
What is the result of a reduction in systemic vascular resistance?
Increased cardiac output, predominantly due to increase in stroke volume (lowered resistance allows more blood to be pumped out of LV at each beat), not much change in HR
When is CO highest during pregnancy?
20-28 weeks
Does CO fall or rise at term?
Small fall
Increased circulating vasodilators has what effect on the capacitance of venous/arterial bed ?
Increased capacitance
How does peripheral vasodilation affect the kidneys?
Increased blood flow to kidneys, so increased GFR, thus decreased serum creatinine levels (more filtered/excreted)
How does peripheral vasodilation affect the extremities, breasts and nasal mucosa?
More blood flow so warm hands and feet, nasal congestion, and breast engorgement.
What is the effect of maternal supine position?
Pressure of uterus and fetus on IVC causes reduction in venous return, thus decreased SV and hence CO. Reduces uterine blood flow and may compromise fetus.
How does the blood volume change during pregnancy?
Increased blood volume, without increase in red cell mass, causes a relative haemodilution, leading to anaemia of pregnancy.
Why is arrhythmogenicity a likely risk factor in pregnancy?
Increased blood volume causes atrial and ventricular stretch, this coupled with catecholamine secretion which results in vasodilation and greater adrenergic receptor sensitivity will increase likelihood of arrhythmogenicity.
How is increased stroke volume achieved?
Increase in ventricular wall muscle mass (increased myocardial contractility) and end-diastolic volume (heart is physiologically dilated)
How does cardiac output change intra partum?
Further increase.
Uterine contractions, increases SV.
Sympathetic response to pain and anxiety further increases HR and BP
What are the effects of cardiac output/stroke volume post partum?
Immediate increase due to relief of IVC obstruction thus increase venous return, and contraction of uterus empties blood into systemic circulation, and transfer of blood from extravascular space increases venous return.
Name some cardiovascular symptoms in pregnant women.
Breathlessness, bounding/collapsing pulse Ejection systolic murmur Loud first and third heart sound. Relative sinus tachycardia. Ectopic beats
What are the changes of platelets in pregnant women?
Fall in platelet levels, slow blood clotting.
How does the iron requirement change in pregnant women?
2-3x increase in iron requirement.
For certain enzymes and for foetal growth.
How does pregnancy achieve a hypercoagulable state?
Increase in fibrinogen, factors, and von Willebrand factor levels. Increase in fibrinolytic inhibitors. Hypercoagulable state in readiness for haemostats following delivery.
Why does risk of venous thromboembolism increase?
Venous stasis induced by venous dilation
Obstruction to venous return
Hypercoagulable state
Pro-inflammatory state with activation of endothelial cells
How does venous stasis in lower limbs differ from left to right?
Compression of L iliac vein by iliac artery and ovarian artery. No crossing of veins on right side. So venodilatation and decreased flow more marks on the left.
Pregnancy is a diabetogenic state. How does insulin requirement change throughout pregnancy?
Initially low requirement. Then insulin secretions increases to counter insulin resistance from higher levels of insulin antagonist.
How does protein excretion change in pregnancy?
Greater GFR means increased protein excretion
