Physio Changes of Pregnancy Flashcards
How does the uterus change?
- Inc size and blood flow
- Inc blood flow is gradual (up to 1 L/ min at peak); big jump in 2nd trimester
Anatomic Cardiac Changes
- Heart displace to left and up (apex more lateral)
- Apparent cardiomegaly on CXR
- Mild inc LV size and end-diastolic dimension
- Grade I to III systolic flow murmurs at L sternal border (extra flow / extra CO)
Changes in Blood Volume (why? how? implications)
- total vol inc by 40-50%
- Plasma volume inc»_space; RBC volume inc … so hemodilution (“physiologic anemia of preg” - dec hematocrit expected); diff norms
- Prenatal vitamins include iron
- Returns to baseline ~ 6 wks postpartum
- Why? meet inc needs of fetus/placenta, prep for poss blood loss in delivery, dec blood viscosity may lower cardiac work needed to perfuse placenta
- How? Luteal hormones (prog, relaxin) and placental hormones –> dec PVR, inc vasodilation, underfiling –> dec renal perfusion –> inc aldosterone –> inc intravascular volume (retention)
How do hemodynamics change?
1 - Huge dec PVR and MAP
- How? hormonal regulation (prog, relaxin), maybe NO, dec response to vasopressors (angio II and NE)
- BP should dec (120/80 is too high for 2nd trimester)
2 - Inc CO by ~50% (inc SV»_space; inc HR)
- Still concerned if HR > 100 BPM
How does blood distribution change?
- Inc flow to … uterus/placenta, kidneys, heart, skin, breasts
- No change to … brain, GI, MSK
Hemodynamic Changes in Labor
- Inc CO in labor…
- Pain
- Pushing (Valsalva)
- Max CO 10-30 min after delivery (b/c uterus clamps down and recycles blood back to vasculature once baby and placenta delivered)
** More stable CO and MAP if epidural
Cardiac Management in Pregnancy
- Epidural
- Close observation in highest risk times - early preg, 28-32 wks (max vol inc), immediately postpartum
- Limit pushing in labor
- Vaginal delivery > C section (more mild cardiac changes)
- Positioning in labor - prefer lateral to supine (hypotension and compression of great vessels by uterus when laying on back)
- Often underlying cardiac conditions can be unmasked during preg, labor, delivery (ex- undiagnosed cardiomyopathy or rheumatic heart disease)
- Note SOB and other symptoms
Why is hyper-coagulation beneficial in pregnancy?
protect against hemorrhage (esp at birth)
Anatomic Pulm Changes
- Elevated diaphragm
- Wider chest diameter
- Cardiac silhouette enlarged and shifted L
- Why? progesterone-induced and physical force of uterus pushing up
2 Major Changes in Lung Function
1 - Dec Lung Capacity
- Dec FRC and RV (b/c elevated diaphragm); important if underlying lung problems - VC not changed
2 - Rate
- Inc tidal volume and RR same = inc minute ventilation (hyperventilation to match inc blood volume)
Implications of Hyperventilation in Pregnancy
- Lower PCO2 than normal b/c hyperventilation (resp alkalosis) –> kidneys comp w/ metabolic acidosis (dec bicarb)
- Keep PCO2 low to inc CO2 gradient b/n baby and mom so that the baby’s CO2 waste can get to mom and be excreted
- Important when considering blood gases; if have normal PCO2 this is too high for pregnant woman
- In ICU … do not use same “permissive hypercapnia” strategy (baby for baby b/c cannot get rid of CO2)
Anatomic Renal Changes
- Inc size (due to inc flow and inc capacity of collecting system)
- Dilation of collecting system (R>L) –> physiological hydronephrosis and hydroureter
- Due to progesterone and R>L b/c uterus is slightly turned to R (dextro-rotated)
Functional Renal Changes
1- Inc in renal blood flow –> inc GFR (highest in 1st trimester)
2 - RETENETION
- Net Na retention - inc tubular reabsorption (aldosterone, estrogen, deoxycorticosterone)
- Total body water inc by 6-8 L
3 - Compensatory metabolic acidosis by inc bicarb excretion - less serum bicarb
**Means pregnant women have less bicarb buffer in their system (dec ability to comp for acidosis - get sicker quicker w/ DKA, lactic acidosis, sepsis, etc)
Renal Labs in Pregnancy
- Dec BUN, dec creatinine
- Inc creatinine clearance
- Glucosuria is not necessarily abnormal (inc GFR)
- Inc urine protein excretion (inc GFR) - still < 300 mg/ 24 hr
