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Why are pregnant women chronically volume overloaded?

1. INcrease in TBW
2. Active sodium and water retention
- due to changes in osmoreg and RAAS


RAAS in pregnancy

Early pregnancy changes cause decreased MAP -->

Marked increases in all components !
(including aldosterone: increases sodium retention and prevents Na+ loss)


ANP and BNP in pregnancies

Normally ANP and BNP are elevated in path states of vol overload

In preg:
ANP slightly increased (w/in nl range)
BNP increases in 3rd tri: especially those complicated by preeclampsia (but lower than lvls seen in CHF)

*many phys states in preg mimic heart disease


What hormone affects plasma vol most during pregnancy?
(plasma vol increases by ~50% starting at 6-8 weeks)

Increased Progesterone

--> lead to decreased smooth muscle tone and increased volume capacity.


Blood pressure fx in pregnancy

blood pressure decreasing during the first 14-16 weeks, stabilizing and then increasing back to baseline during the third trimester.
- This decrease in SVR is due primarily to effects on smooth muscle by progesterone as well as increased NO production decreasing vascular tone/resistance

*the blood pressure is USUALLY never be higher than baseline blood pressure in a normal pregnancy.


What accounts for the 40% increase in CO in pregnancy?

Stroke vol increase

- Also due to increase in HR by 10-20 beats/min


What position can we see the greatest increase in CO?

in left lateral pos
- the BP of the superior arm is 10-12 mm lower than the inferior arm.


Changes in heart due to preg

1. Hypertrophy of vent muscle
2. Increase in preload: due to increased venous return
3. Decrease in afterload due to decreased vascular resistance


CO increases perfusion to many organs, except which ones?

Brain and liver

*it does increase perfusion to kidney, breasts, skin, uterus


Which murmur is nl in pregnancy?

Systolic ejection murmur along Left sternal border (96%)
- due to more volume
S3 common
- due to vent enlargement to increase EDV

*diastolic mumur very uncommon --> echo


How common are arrhythmias in preg?

Common: almost all women will have some typ
- heart moves closer to the chest wall --> more likely to notice palpitations


When will you see highest increase in CO?

10-30 min after delivery
- Symp stim (pain, anxiety)
- Uterine autotransfusion (500cc blood forced fr uterus --> systemic circ during each contraction)


What type of lesions on heart valves are more tolerable? Regurgitant or stenotic?


*Pts with AS have a fixed stroke vol. so CO depends mainly on HR
- very limited:
bradycardia --> hypotension
Tachycardia --> hypotension


What should you avoid in pts with pregnancy regarding fx on bp?

Vasodilators: it can lead to a precipitous drop in systemic blood pressure.

Thus, during pregnancy, the decrease in SVR can lead to precipitous drops in BP as well, and higher rates of syncopal episodes.


What hormone affects the sensitivity of respiratory centers to CO2 resulting in hyperventilation?

- minute ventilation is increased (RRx TV)

Resp. rate remains unchanged


Why is there decreased levels of PaCO2 in preg?

due to increased gas exchange


Are resp muscles affected by preg?

- max insp and exp pressures are unchanged


Minute ventilation (RRxTV) increases in preg, how is maternal pH maintained?

increase in bicarb excretion
- nl in preg = 18-21


Dyspnea of pregnancy

Dyspnea is mild, doesn't interfere with daily activities. DOES NOT OCCUR AT REST.
- common complaint


Pregnancy is a state of primary _____ with a compensatory ______

resp. alkalosis

metabolic acidosis

*There is an increase in arterial PO2, a decrease in PCO2, but a concomitant decrease in HCO3- to compensate
- Thus, in spite of the physiologic hyperventilation that ensues, pH is relatively unchanged, or increases slightly by several hundredths of a point. In order to compensate for the decrease in arteriolar C02 levels, renal bicarb excretion is increased resulting in a decrease in serum levels.


Nl PCO2 in pregnancy vs nl

Nl O2 in preg

Nl PCO2: 40

Pregnancy: 27-32 mmHg
- 40 would be a sign of impending resp failure

Nl O2 sat: >95% or hypoxemic


Does GFR and renal plasma flow increase or decrease in pregnancy?

Increase both

*thus filtration fraction GFR/RPF actually falls
Importantly, the increase in hyperfiltration occurs without an increase in glomerular pressure, which if it occurred , could have the potential for injury to a woman’s kidney with long term consequences.


High GFR and plasma vol does what to Cr and BUN?

Lowers both

A Cr of 0.8 and above can be seen as a red flag in pregnancy as a sign of decreasing renal function.


Pts with renal insufficiency are at risk for what?

1. Worsening renal disease
2. Preeclampsia
(intrauterine growht restrictions)
4. PTB


Anemia in preg

There is this increase in plasma volume, by about 50%, however there is only about a 20-30% increase in red blood cell mass, thus there is a concomitant dilutional anemia.
- presyncopal and syncopal episodes and fatigue. Any symptomatic patient should be begun on iron supplementation if labs point to iron deficiency.


T cell shift in pregnancy

Shift from T helper cells (TH1) away from cell mediated immunity towards humoral (TH2) response


Do increase in clotting factors play a role in objective tests of clotting such as PT, PTT or clotting times?

No the increase in coagulability is not due to increase in clotting factors
- concentration in the serum is not dramatically affected.

The increase in DVT and PE: most likely secondary to other aspects of Virchow’s triad. In pregnancy, there is much more stasis of blood flow in the lower extremities secondary to compression of the pelvic vessels by the uterus.


DVT is more common on which side?

- L common iliac vein is more compressed due to R common iliac artery overlying it

DVT is one of the most common cause of maternal mortality


Std prophylaxsis for DVT and PE

LMW heparin (long half life)
- but must switch to unfractionated heparin at 36 weeks to prevent hemorrhage during pregnancy


Why is warfarin (coumadin) contraindicated?

Nasal hypoplasia
Stippling of bones, brachydactyly