Considerations in Pregnancy Flashcards
Cardiovascular Adaptations
blood ovolume
cardiact output
bp changes
§ Blood volume increases by 40 – 50%.
* Plasma volume increases by 40 – 50% (early in pregnancy)
* RBC volume increases by 30 – 40% (later in pregnancy)
§ Cardiac output increases by 30 – 50%
* This includes both stroke volume and heart rate.
* Occurs by 8 weeks.
§ Blood pressure may decrease in the first trimester
Now what’s interesting is that you can actually see a decrease in blood pressure in the first trimester. And this is due secondary, due to decrease in peripheral vascular resistance.
in the third trimester, because of all the increase in plasma volume as well as blood volume, you could actually look like it can look like a physiologic anemia, meaning that it’s not a true anemia at that time. It could just look like that because of the overall plasma volume. Plasma volume can increase more than the , red blood cell volume.
Cardiovascular Adaptations
regional blood flow
vascular resistance
lower limb vneous pressure
§ Regional blood flow is altered.
§ Systemic (peripheral) vascular
resistance decreases.
* ?possibly a role of placental
steroid hormones (specifically
progesterone)
* Placenta is a low resistance
circuit with high blood flow.
Lower limb venous pressure increases
§ Possible causes: enlarging uterus
impedes inferior vena cava pressure +
placenta acts as an “A-V shunt”
§ Third trimester may see supine
hypotensive episodes from gravid
uterus impeding flow in inferior vena
cava.
§ Increased varicosities common (ie
hemorrhoids, varicose veins)
§ Increased risk of deep vein thrombosis
Supine Hypotensive Episodes
it also depends on how the mother is lying down. So lying down straight on the back, this really can impede that inferior vena cava versus lying on the side has less effect. So they do recommend as the baby grows, the fetus grows that moving more sleeping on the side versus on the back. And there’s reasons for that. So to avoid that hypotensive effects
Respiratory Changes
§ Increased oxygen consumption (both maternal and
fetal/placental needs).
§ Progesterone causes increased sensitivity of the medullary
respiratory center to CO2
So there’s an increased response. So at a lower carbon dioxide, then you start breathing heavier. And so that’s why pregnant individuals can breathe more, higher respiratory rates because that increased sensitivity
§ Enlarging gravid uterus may compromise lung volumes
Respiratory Changes: Summary
§ Minute ventilation _________
Minute ventilation increases 40 – 50%
* By increases in tidal volume and
respiratory rate
§ There is no change to Vital Capacity.
§ Residual volume is decreased
§ Blood gases reflect these changes.
* There is a compensated respiratory
alkalosis.
Of note: respiratory complications
no more common than nonpregnant. Treat same as nonpregnant.
there’s really not a change in the overall vital capacity.
increase in tidal volume. So that’s the normal breath and then out
Increase the respiratory rate. Remember, because that increased sensitivity to carbon dioxide
But what decreases is this excretory volume. So if you breathe in as much as you can and then breathe it out, that excretory, that remaining reserve that you’re trying to breathe out can, can, can get lessened.
Then there’s also this lesson of this residual volume a bit too.
Hematologic Changes
§ Iron requirements in pregnancy:
Ø450 ml maternal RBC 500 mg Fe
ØLoss at delivery 200 mg
ØFetal/placental need 300 mg
ØTotal 1000 mg
§ Supplements usually recommended:
* 50 – 60 mg elemental iron per day during last half of pregnancy
* Absorption increases (to ~15%)
you’re looking at about 50 to 60 mg of elemental iron per day during that last half of the pregnancy is usually recommended. One note, I just, I don’t know if it makes a clinical significance, but absorption overall increases with pregnancy as well. So I’m not sure if it makes a clinical difference, but just to be aware.
Hematologic Changes
changes in clotting factors and risk of thrombosis
§ Increased clotting factors
* Estrogen induced
§ Increased risk of thrombosis
* Greatest risk is peri and post-partum
* Virchow’s triad:
* Venous stasis
* Hypercoagulability
* Endothelial damage
So there’s facts that can increase this risk, including hypercoagulability from the estrogen, venous stasis, things aren’t moving around as, as easily. And there could be endothelial damage, especially during delivery.
iggest risk is during that just immediately that postpartum, right? Like that peripartum period where they delivered, and especially back to that first six weeks after delivery is the greatest risk.
Gastrointestinal Changes
§ Relaxation of smooth muscle in GI tract.
* Results in delayed gastric emptying.
* Upper GI symptoms are very common.
* Can lead to heartburn and GERD – can be as common as 30 – 50% of
pregnancies.
§ Nausea and vomiting (refer to GI block)
relaxation of smooth muscles in the GI track. This can affect certain things. Delay, gastric emptying, which could affect obviously more heartburn. That’s why pregnant women can have more upward or reflux can be worsened or all the ones they start experiencing it for the first time.
Renal Changes
Increased blood flow (~40%)
* Increase in GFR
§ Increased activity of renal-angiotensin system
* Estrogen induces increase in angiotensin in the liver
§ Increased glucosuria – may see glucosuria at normal blood
glucose levels
* Even though GFR increases ability to absorb glucose stays the same.
* May not be a good indicator of glucose control in diabetics.
Fetal-Placental Metabolism
§ Placenta is metabolically active
BUT! Assume everything you give to the mother gets to the fetus.
§ Fetus actively metabolizes and excretes.
Summary of Pharmacokinetic Changes from
Physiologic Adaptations
§ Increased volume of distribution
§ Increased clearance of drugs
* Increased flow to kidneys and GFR
* Increased hepatic flow andmetabolism
* May be placental clearance and metabolism
Others:
§ Absorption
* Reduction in GI motility/emptying may delay time to peak but usually not clinical significant.
§ decreased protein binding
(albumin)
this is just going to affect more of those drugs that are highly protein bound, right? And then you have more free. But you also see an increase effect on the liver. So for the most part, clinically significant, it’s not an issue because it’s gonna be metabolized by the liver and there’s an increased metabolism already.
Other than if somebody has issues with hepatic clearance or they have some liver dysfunction or something already that can’t match that, then that’s gonna be more of the issue for those drugs. S
