Flashcards in Maternal Changes in Preg Deck (35)
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
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)
--> 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
- 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 ______
*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?
*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?
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
(intrauterine growht restrictions)
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