OBGYN - Maternal-Fetal Physiology
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*Non-pregnant lab values and measurements are frequently abnormal in the pregnant state | *Non-pregnant lab values and measurements are frequently abnormal in the pregnant state | ||
- | ==First Trimester== | + | ==Case: First Trimester== |
- | *21 y/o G1P0 at 8w0d by L=6 week US at the | + | *21 y/o G1P0 at 8w0d by L=6 week US at the WVC (women's visit center at Wishard) presents for her OB registration appointment. |
**She denies any LOF (leaking of fluid), VB (vaginal bleeding). | **She denies any LOF (leaking of fluid), VB (vaginal bleeding). | ||
**Pt with C/C of cramping and dark “poop”, nausea and vomiting with heart burn. | **Pt with C/C of cramping and dark “poop”, nausea and vomiting with heart burn. | ||
*PMH: Denied | *PMH: Denied | ||
- | * | + | *PSocialH: Denied |
*OB: G1 | *OB: G1 | ||
*Gyn: Denied | *Gyn: Denied | ||
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*Allergies: NKDA | *Allergies: NKDA | ||
*Medications: PNV (Prenatal Vitamin) | *Medications: PNV (Prenatal Vitamin) | ||
- | *VS: BP: 110/80 P: 80 T: 98.6 Weight: 65Kg Height: 5’1 UA: WNL | + | *VS: BP: 110/80 P: 80 T: 98.6 Weight: 65Kg Height: 5’1 |
+ | *UA: WNL | ||
*PE: WNL | *PE: WNL | ||
- | + | ==GI Issues in the First Trimester== | |
- | + | *Constipation: | |
- | ** | + | **Iron (ferrous-sulfate) in the pre-natal vitamins slows GI motility and causes constipation. |
- | + | **'''Progesterone: a smooth muscle relaxant; causes decreased bowel movement which can lead to increased time for water reabsorption and thus constipation''' | |
- | + | **Tx: give colace | |
- | + | **Could be as bad a month! | |
- | + | **There is fear of miscarriage throughout pregnancy so anything seeming abnormal (like not pooping) starts a fear of miscarriage. | |
- | + | ||
- | + | ||
- | ** | + | |
- | ** | + | |
- | + | ||
- | + | ||
- | ==Second Trimester== | + | *Nausea and Vomiting: |
+ | **beta-HCG causes n/v | ||
+ | ***beta-HCG peaks at 10-12 weeks. | ||
+ | **{rogesterone: a smooth muscle relaxant; causes decreased bowel movement which can lead to n / v. | ||
+ | |||
+ | |||
+ | *Weight gain: | ||
+ | **can occur early or late, ideal is a progression. | ||
+ | **vomitting can lead to weight loss over the first weeks, but mom and baby will be ok | ||
+ | **Normal Weight for Height: about 20 lbs | ||
+ | **Underweight Women: about 30 lbs | ||
+ | **Overweight Women: about 16 lbs | ||
+ | **Only an addition 300 calories / day are necessary to feed a fetus. | ||
+ | ***500 cal for twins | ||
+ | |||
+ | ==Case: Second Trimester== | ||
*21 y/o is now 20 weeks pregnant | *21 y/o is now 20 weeks pregnant | ||
*Presents to triage at Wishard with horrible heartburn after eating a deep fried twinkie at the state fair. | *Presents to triage at Wishard with horrible heartburn after eating a deep fried twinkie at the state fair. | ||
- | *She threw-up so much in early pregnancy that she is making up for it now. | + | *She threw-up so much in early pregnancy that she is making up for it now. |
+ | **She has gained 25 lbs (from 8 weeks to second trimester). | ||
+ | **That is a lot of weight gain. | ||
*She denied any LOF (leaking of fluid), denied VB (vaginal bleeding) or cramping. | *She denied any LOF (leaking of fluid), denied VB (vaginal bleeding) or cramping. | ||
*She stated that she had some of the chalkie things and it didn’t make it better this time. | *She stated that she had some of the chalkie things and it didn’t make it better this time. | ||
+ | **Tums. | ||
*She was given a GI cocktail in triage and she was still miserable. | *She was given a GI cocktail in triage and she was still miserable. | ||
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**Constipation | **Constipation | ||
***Small bowel obstruction | ***Small bowel obstruction | ||
+ | ***Ask when they last deficated. | ||
**Gallstones | **Gallstones | ||
+ | ***Increased estrogen and progesterone | ||
+ | ***Slow emptying of the stomach | ||
+ | ***Often already at high risk (four "F"s: fat, forty, fertile, female) | ||
+ | ***Can look really, really, bad. | ||
**Pancreatitis | **Pancreatitis | ||
**Appendicitis | **Appendicitis | ||
+ | ***Appendix moves from right lower quadrant to midquadrant | ||
+ | ***Can get tucked up behind the uterus | ||
+ | |||
+ | ==First / Second Trimester GI Presentations== | ||
+ | *High levels of estrogen / progesterone in pregnancy lend themselves to gallstone formation | ||
+ | **Especially when woman gets pregnant a second time without having gallstones from a previous pregnancy removed. | ||
- | |||
- | |||
*Recall that progesterone is a smooth muscle relaxant. | *Recall that progesterone is a smooth muscle relaxant. | ||
*Recall that progesterone is at high levels throughout pregnancy to maintain the uterine environment. | *Recall that progesterone is at high levels throughout pregnancy to maintain the uterine environment. | ||
+ | **Progesterone is really rampinig up during the first trimester. | ||
*High circulating levels of progesterone can lead to: | *High circulating levels of progesterone can lead to: | ||
**Increased GERD from relaxation of GE sphincter | **Increased GERD from relaxation of GE sphincter | ||
**Constipation from delayed transit through large bowel | **Constipation from delayed transit through large bowel | ||
**Increased N/V from delayed gastric emptying | **Increased N/V from delayed gastric emptying | ||
+ | **Stomach can still be full of content 8 hours later. | ||
**“Full stomach” sensation | **“Full stomach” sensation | ||
- | * | + | *Tx is often to keep pt from eating for 8 to 12 hours and then to switch to a little bit, throughout the day type consumption pattern. |
- | ==Second / Third Trimester | + | ==Case: Second / Third Trimester== |
*21 y/o G1P0 at 28w0d | *21 y/o G1P0 at 28w0d | ||
*Presents to triage at St. Francis Beech Grove. | *Presents to triage at St. Francis Beech Grove. | ||
*Patient has been brought in by her family “Doc I feel horrible. I am dizzy. I was sitting at the high-school football game, I stood up to cheer, my heart started racing and I felt like I was going to pass-out! My ankles are swollen and I feel horrible." | *Patient has been brought in by her family “Doc I feel horrible. I am dizzy. I was sitting at the high-school football game, I stood up to cheer, my heart started racing and I felt like I was going to pass-out! My ankles are swollen and I feel horrible." | ||
*Denies LOF (leaking of fluid), VB (vaginal bleeding), CTXs (contractions). | *Denies LOF (leaking of fluid), VB (vaginal bleeding), CTXs (contractions). | ||
- | + | *'''Endorses +FM (fetal movement).''' | |
- | *ED doctor noticed that she is breathing deeply. | + | *ED doctor noticed that she is '''breathing deeply.''' |
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*Labs ordered: | *Labs ordered: | ||
- | + | **CBC w/platelets | |
- | + | **CXR (chest xray) | |
+ | **ABG (arterial blood gas) | ||
+ | **UA (urinary analytes) | ||
+ | **CMP (complete metabolic panel) | ||
+ | **Coags (coagulation studies) | ||
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*Lab results: | *Lab results: | ||
- | **WBC: 10, 000 (slightly elevated) | + | **WBC: 10,000 (slightly elevated) |
- | **Hgb/HCT: 10.5/31.7% (decrease) | + | **Hgb / HCT: 10.5/31.7% (decrease) |
**Platelets: 200,000 (slight decrease) | **Platelets: 200,000 (slight decrease) | ||
**Fibrinogen: 600 (increased) | **Fibrinogen: 600 (increased) | ||
- | **Bun / Cr | + | **Bun / Cr: 3 / 0.6 (decreased) |
- | ** | + | **pH: 7.44 |
**pCO2: 30 | **pCO2: 30 | ||
**BiCarb: 21 | **BiCarb: 21 | ||
- | **paO2 | + | **paO2: 103 |
- | + | ==Physiological Changes in Pregnancy== | |
- | + | ||
===Blood pressure in pregnancy=== | ===Blood pressure in pregnancy=== | ||
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*Systalic decreases 5-10 mmHg | *Systalic decreases 5-10 mmHg | ||
*Diastolic decreases 10-15 mmHg | *Diastolic decreases 10-15 mmHg | ||
+ | *We even take severe hypertensive pts off their meds. | ||
*Normal | *Normal | ||
+ | |||
+ | |||
+ | *Monitor from baseline! | ||
+ | **Athletes will have low baseline BP and therefore it will be a challenge to keep their BP up during pregnancy. | ||
===Pulse in pregnancy=== | ===Pulse in pregnancy=== | ||
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*CO increases at ''8 weeks'' and peaks at ''20 weeks''. | *CO increases at ''8 weeks'' and peaks at ''20 weeks''. | ||
*CO increases by 30-50% | *CO increases by 30-50% | ||
- | + | *CO rises to 4.5-6.0 L / min | |
How do we know her stroke volume? | How do we know her stroke volume? | ||
*Systolic ejection murmur is common (90% of women). | *Systolic ejection murmur is common (90% of women). | ||
*S3 gallop is common (90% of women). | *S3 gallop is common (90% of women). | ||
*'''Peripheral vascular resistance falls during pregnancy, too.''' | *'''Peripheral vascular resistance falls during pregnancy, too.''' | ||
+ | **Hence the swelling. | ||
+ | **Wear flipflops, wear compression socks | ||
+ | **Especially medical residents. | ||
===Respiratory rate in pregnancy=== | ===Respiratory rate in pregnancy=== | ||
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*Note that '''respiratory rate should remain unchanged''' in normal pregnancy. | *Note that '''respiratory rate should remain unchanged''' in normal pregnancy. | ||
**This is possible because the tidal volume increases (because the minute ventilation increases). | **This is possible because the tidal volume increases (because the minute ventilation increases). | ||
+ | *Functional residual capacity decreases by 20% because of displacement the uterus. | ||
+ | |||
http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/004f.gif | http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/004f.gif | ||
http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/001f.gif | http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/001f.gif | ||
+ | |||
*So '''dyspnea ''is'' normal with pregnancy'''. | *So '''dyspnea ''is'' normal with pregnancy'''. | ||
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|} | |} | ||
- | ===ABG in | + | ===Arterial blood gas (ABG) in pregnancy=== |
- | * | + | *NB: '''ABG should never be "normal" in pregnancy!''' |
- | * | + | **Should have a respiratory alkalosis from blowing off their CO2 at higher rates. |
- | * | + | **Should have a metabolic acidosis (compensatory). |
- | * | + | *Many pregnant women will hyperventalate. |
- | * | + | **Give them a bag in which to breath. |
+ | **Very hard to settle them down so important to give the bag quickly and pt will often become syncopous. | ||
- | * | + | *Pt's ABG was: |
- | * | + | **pH: 7.44 ( |
+ | **pCO2: 30 | ||
+ | **BiCarb: 21 | ||
+ | **paO2: 103 | ||
- | * | + | *Recall that O2 consumption increases in pregnancy. |
- | * | + | **15-20% |
+ | *Recall that minute ventilation (the amount of air breathed in over the course of one minute) is increased ''relatively more than the O2 consumption''. | ||
+ | **This means that '''more air is breathed in and out than is necessary for the rate of oxygen consumption.''' | ||
+ | **This is the '''definition of hyperventilation!''' | ||
+ | *Recall the chemical equation: CO2 + H20 <=> H2CO3 <=> HCO3 + H | ||
+ | *Recall that hyperventilation gives off CO2, dragging the equation to the left. | ||
+ | **That is, pCO2 will be decreased. | ||
+ | *Therefore pregnant, hyperventilating women become '''alkalotic''' (decreased H+). | ||
+ | **That is, pH will be high (less H+). | ||
+ | **This is a '''respiratory alkalosis'''. | ||
+ | *Recall that the kidneys can excrete HCO3 to compensate for loss of CO2 (because of hyperventilation) and thus draw the equation back to the right. | ||
+ | **Thus we expect the serum HCO3 to be low. | ||
+ | *Recall that in pregnancy there is an increased oxygen carrying capacity (facilitated by RBC volume increased by 50%). | ||
+ | **Thus we expect the pO2 to be high. | ||
- | + | *Given this respiratory alkalosis and metabolic (compensatory) acidosis, we expect: | |
- | * | + | **the pCO2 to be low: 26-32 mmHg (compared to non-pregnancy 38-45) |
- | + | **the pH to be high (alkaline): 7.40-7.46 (compared to non-pregnancy 7.38-7.42) | |
- | ** | + | **the HCO3 to be low: 18-21 mEq / L (compared to non-pregnancy 24-31) |
- | + | **the pO2 to be high: 106-108 mmHg (compared to non-pregnancy 70-100) | |
- | + | ||
- | + | ||
- | ** | + | |
- | ** | + | |
- | + | ||
- | * | + | *A high pCO2 is cause for alarm in the asthmatic pregnant woman. |
+ | *Also, pCO2 should be monitored carefully in the acutely infected pregnant woman because they are '''immune compromised''' and have '''very little respiratory reserve'''. | ||
{|border=1 | {|border=1 | ||
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!Pregnant | !Pregnant | ||
!Change | !Change | ||
+ | !Reason | ||
|- | |- | ||
!pH | !pH | ||
|7.38 - 7.42 | |7.38 - 7.42 | ||
|7.4 - 7.46 | |7.4 - 7.46 | ||
- | | | + | |Higher |
+ | |Because of the balance of respiratory alkalosis and (compensatory) metabolic acidosis. | ||
|- | |- | ||
!pCO2 (mmHg) | !pCO2 (mmHg) | ||
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|26 - 32 | |26 - 32 | ||
|Lower | |Lower | ||
+ | |Because minute ventilation increases more than oxygen consumption (CO2 breathed off faster than oxygen consumed). | ||
|- | |- | ||
!pO2 (mmHg) | !pO2 (mmHg) | ||
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|101 - 106 | |101 - 106 | ||
|Lower | |Lower | ||
+ | |Because RBC volume is increased. | ||
|- | |- | ||
!HCO3- (mEq / L) | !HCO3- (mEq / L) | ||
|24 - 31 | |24 - 31 | ||
|18 - 21 | |18 - 21 | ||
- | | | + | |Lower |
+ | |Because the kidneys are excreting HCO3- in an attempt to compensate for respiratory alkalosis. | ||
|- | |- | ||
!O2 saturation (%) | !O2 saturation (%) | ||
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|95 - 100 | |95 - 100 | ||
|None | |None | ||
+ | | | ||
|} | |} | ||
*Importance: | *Importance: | ||
- | **A normal pregnant woman has a compensated respiratory alkalosis and a diminished pulmonary reserve. | + | **'''A normal pregnant woman has a compensated respiratory alkalosis (with a compensatory metabloic acidosis) and a diminished pulmonary reserve.''' |
- | + | ||
*Cause: | *Cause: | ||
- | **Progesterone | + | **Progesterone: relaxes the smooth muscle |
**Diaphragm raised 4cm | **Diaphragm raised 4cm | ||
- | |||
===CBC in pregnancy=== | ===CBC in pregnancy=== | ||
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**“Physiologic anemia of pregnancy” | **“Physiologic anemia of pregnancy” | ||
**The mean Hgb is about 11.5 g/dl | **The mean Hgb is about 11.5 g/dl | ||
+ | *At 28 weeks, get new labs. | ||
+ | *'''Will likely need to start iron.''' | ||
+ | **Start at or below 10. | ||
+ | **Yucky tasting, makes woman feel horrible. | ||
+ | **''Necessary for proper oxygenation.'' | ||
===Coagulation in pregnancy=== | ===Coagulation in pregnancy=== | ||
- | *In pregnancy the pt is hypercoaguable | + | *'''In pregnancy the pt is hypercoaguable''' |
+ | **This is the body's way to not die from bleeding when the parasite is ejected / ripped from the internal surface of the uterus. | ||
+ | *DIC is the number 1 cause of death in laboring women around the world. | ||
+ | **Not so much here in the US. | ||
*Procoagulant’s are increased: I, VII, VIII, IX, X and Fibrinogen. | *Procoagulant’s are increased: I, VII, VIII, IX, X and Fibrinogen. | ||
*Prevents Peripartum Hemorrhage | *Prevents Peripartum Hemorrhage | ||
- | + | *Can lose 1500mL without blinking. | |
+ | *Over 2000 mL lost, start worrying b/c coag factors are becoming deficient. | ||
===Renal System in pregnancy=== | ===Renal System in pregnancy=== | ||
*Bun & Serum Creatinine decreases by about 25% | *Bun & Serum Creatinine decreases by about 25% | ||
+ | **Low because of increased blood volume, increased GFR, increased blood flow to the kidneys | ||
*Plasma osmolarity decreases by about 10 mOsm / kg H20 | *Plasma osmolarity decreases by about 10 mOsm / kg H20 | ||
*Increase in tubal reabsorption of sodium | *Increase in tubal reabsorption of sodium | ||
*Marked increase in renin and angiotensin levels | *Marked increase in renin and angiotensin levels | ||
- | **But markedly reduced vascular sensitivity to their hypertensive effects | + | **But '''markedly reduced vascular sensitivity to their hypertensive effects''' |
*Increased glucose excretion | *Increased glucose excretion | ||
+ | **Fine during labor, a coping mechanism. | ||
+ | **Labs at 28 weeks detect gestational diabetes. | ||
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**Kidney weight increases | **Kidney weight increases | ||
**Ureteral dilation (right side greater than left side) | **Ureteral dilation (right side greater than left side) | ||
+ | ***Because of the angle of the uterus | ||
**Bladder becomes an intra-abdominal organ | **Bladder becomes an intra-abdominal organ | ||
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**GFR increase by 50% | **GFR increase by 50% | ||
**Renal plasma increased by flow by 75% | **Renal plasma increased by flow by 75% | ||
- | **Creatinine Clearance increases to 150-200 cc / min | + | **'''Creatinine Clearance increases to 150-200 cc / min''' |
+ | ***Most important kidney function test in pregnancy | ||
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***1 / 3rd intravascular | ***1 / 3rd intravascular | ||
***Intravascular increase is put in the "dependent" (affected by gravity) areas like the lower venous system. | ***Intravascular increase is put in the "dependent" (affected by gravity) areas like the lower venous system. | ||
+ | **Hard to move fluids through the venous system. | ||
- | ==Caring Family== | + | ==Case: Caring Family== |
*The patient’s husband lies her flat in an effort to keep her comfortable. | *The patient’s husband lies her flat in an effort to keep her comfortable. | ||
- | + | *The fetus’s FHTs (fetus heart tones) drop to 80. | |
*But, the ROCK STAR medical student wedges the patient quickly on her left side and the FHT’s recover quickly! | *But, the ROCK STAR medical student wedges the patient quickly on her left side and the FHT’s recover quickly! | ||
+ | **Turns her off the vena cava. | ||
+ | **Aids in venous return to the heart and therefore to oxygenation of blood for mom and baby. | ||
- | *What happened? | + | *What happened to the cared-for mother? |
- | *Gravid Uterus placed pressure on the IVC | + | *Gravid Uterus placed pressure on the IVC which resulted in decreased “utero-placental blood flow.” |
- | + | ||
**Cardiac output falls | **Cardiac output falls | ||
**Blood is shunted '''to the brain''' and | **Blood is shunted '''to the brain''' and | ||
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**Decreased BP | **Decreased BP | ||
**Swollen ankles | **Swollen ankles | ||
- | **CXR cardiomegaly | + | **CXR: cardiomegaly, leftward deviation |
**Systolic Ejection murmur | **Systolic Ejection murmur | ||
**Dyspnea | **Dyspnea |
Revision as of 23:16, 2 December 2011
Maternal-Fetal Physiology
Objectives
- List pertinent physiologic changes in various maternal systems
- Recognize that signs and symptoms in a pregnant patient are often more difficult to interpret
- Non-pregnant lab values and measurements are frequently abnormal in the pregnant state
Case: First Trimester
- 21 y/o G1P0 at 8w0d by L=6 week US at the WVC (women's visit center at Wishard) presents for her OB registration appointment.
- She denies any LOF (leaking of fluid), VB (vaginal bleeding).
- Pt with C/C of cramping and dark “poop”, nausea and vomiting with heart burn.
- PMH: Denied
- PSocialH: Denied
- OB: G1
- Gyn: Denied
- Social Hx: Denied x 3
- Allergies: NKDA
- Medications: PNV (Prenatal Vitamin)
- VS: BP: 110/80 P: 80 T: 98.6 Weight: 65Kg Height: 5’1
- UA: WNL
- PE: WNL
GI Issues in the First Trimester
- Constipation:
- Iron (ferrous-sulfate) in the pre-natal vitamins slows GI motility and causes constipation.
- Progesterone: a smooth muscle relaxant; causes decreased bowel movement which can lead to increased time for water reabsorption and thus constipation
- Tx: give colace
- Could be as bad a month!
- There is fear of miscarriage throughout pregnancy so anything seeming abnormal (like not pooping) starts a fear of miscarriage.
- Nausea and Vomiting:
- beta-HCG causes n/v
- beta-HCG peaks at 10-12 weeks.
- {rogesterone: a smooth muscle relaxant; causes decreased bowel movement which can lead to n / v.
- beta-HCG causes n/v
- Weight gain:
- can occur early or late, ideal is a progression.
- vomitting can lead to weight loss over the first weeks, but mom and baby will be ok
- Normal Weight for Height: about 20 lbs
- Underweight Women: about 30 lbs
- Overweight Women: about 16 lbs
- Only an addition 300 calories / day are necessary to feed a fetus.
- 500 cal for twins
Case: Second Trimester
- 21 y/o is now 20 weeks pregnant
- Presents to triage at Wishard with horrible heartburn after eating a deep fried twinkie at the state fair.
- She threw-up so much in early pregnancy that she is making up for it now.
- She has gained 25 lbs (from 8 weeks to second trimester).
- That is a lot of weight gain.
- She denied any LOF (leaking of fluid), denied VB (vaginal bleeding) or cramping.
- She stated that she had some of the chalkie things and it didn’t make it better this time.
- Tums.
- She was given a GI cocktail in triage and she was still miserable.
- Differential Diagnosis:
- Constipation
- Small bowel obstruction
- Ask when they last deficated.
- Gallstones
- Increased estrogen and progesterone
- Slow emptying of the stomach
- Often already at high risk (four "F"s: fat, forty, fertile, female)
- Can look really, really, bad.
- Pancreatitis
- Appendicitis
- Appendix moves from right lower quadrant to midquadrant
- Can get tucked up behind the uterus
- Constipation
First / Second Trimester GI Presentations
- High levels of estrogen / progesterone in pregnancy lend themselves to gallstone formation
- Especially when woman gets pregnant a second time without having gallstones from a previous pregnancy removed.
- Recall that progesterone is a smooth muscle relaxant.
- Recall that progesterone is at high levels throughout pregnancy to maintain the uterine environment.
- Progesterone is really rampinig up during the first trimester.
- High circulating levels of progesterone can lead to:
- Increased GERD from relaxation of GE sphincter
- Constipation from delayed transit through large bowel
- Increased N/V from delayed gastric emptying
- Stomach can still be full of content 8 hours later.
- “Full stomach” sensation
- Tx is often to keep pt from eating for 8 to 12 hours and then to switch to a little bit, throughout the day type consumption pattern.
Case: Second / Third Trimester
- 21 y/o G1P0 at 28w0d
- Presents to triage at St. Francis Beech Grove.
- Patient has been brought in by her family “Doc I feel horrible. I am dizzy. I was sitting at the high-school football game, I stood up to cheer, my heart started racing and I felt like I was going to pass-out! My ankles are swollen and I feel horrible."
- Denies LOF (leaking of fluid), VB (vaginal bleeding), CTXs (contractions).
- Endorses +FM (fetal movement).
- ED doctor noticed that she is breathing deeply.
- Pertinent Vitals:
- BP: 100/60
- P: 90
- T: 98.6
- RR: 16
- O2: 96% RA
- Weight: 80kgs
- Labs ordered:
- CBC w/platelets
- CXR (chest xray)
- ABG (arterial blood gas)
- UA (urinary analytes)
- CMP (complete metabolic panel)
- Coags (coagulation studies)
- PE:
- Lungs: CTA B
- CV: Systolic murmur
- Abd: Gravid, NT
- Extrem: +1 pitting edema
- Lab results:
- WBC: 10,000 (slightly elevated)
- Hgb / HCT: 10.5/31.7% (decrease)
- Platelets: 200,000 (slight decrease)
- Fibrinogen: 600 (increased)
- Bun / Cr: 3 / 0.6 (decreased)
- pH: 7.44
- pCO2: 30
- BiCarb: 21
- paO2: 103
Physiological Changes in Pregnancy
Blood pressure in pregnancy
- Pt blood pressure: 100/60
- Both systolic and diastolic BP decrease in 2nd trimester
- Systalic decreases 5-10 mmHg
- Diastolic decreases 10-15 mmHg
- We even take severe hypertensive pts off their meds.
- Normal
- Monitor from baseline!
- Athletes will have low baseline BP and therefore it will be a challenge to keep their BP up during pregnancy.
Pulse in pregnancy
- Pt's pulse: 90
- Increases 20 beats (peak at 32 weeks, middle of 3rd trimester)
- Normal
Cardiac output in pregnanc
- Recall that cardiac output (CO) is stroke volume (SV) multiplied by the heart rate (HR).
- CO increases at 8 weeks and peaks at 20 weeks.
- CO increases by 30-50%
- CO rises to 4.5-6.0 L / min
How do we know her stroke volume?
- Systolic ejection murmur is common (90% of women).
- S3 gallop is common (90% of women).
- Peripheral vascular resistance falls during pregnancy, too.
- Hence the swelling.
- Wear flipflops, wear compression socks
- Especially medical residents.
Respiratory rate in pregnancy
- Recall your standard respiratory volumes (see image below).
- Note that O2 demand (consumption) is increased by 15-20% in pregnancy.
- These volumes are affected by the displacement of the diaphragm rostrally.
- Note that respiratory rate should remain unchanged in normal pregnancy.
- This is possible because the tidal volume increases (because the minute ventilation increases).
- Functional residual capacity decreases by 20% because of displacement the uterus.
- So dyspnea is normal with pregnancy.
Volume (mL) | Definition | Non-pregnant | Pregnant | Change |
---|---|---|---|---|
Total lung capacity | Vital capacity + residual volume | 4200 | 4000 | -4% |
Vital Capacity | Total lung capacity - residual volume | 3200 | 3200 | 0% |
Inspiratory Capacity | Vital capacity - expiratory reserve volume | 2500 | 2650 | +6% |
Tidal volume | Volume moved in and out with each normal breath | 450 | 550 | +33% |
Expiratory Reserve Volume | Vital capacity - inspiratory capacity | 700 | 550 | -20% |
Inspiratory Reserve Volume | Inspiratory capacity - total volume | 2050 | 2050 | 0% |
Residual volume | Total volume - vital capacity | 1000 | 800 | -20% |
Functional Residual Capacity | Residual volume + expiratory reserve volume | 1700 | 1350 | -20% |
Arterial blood gas (ABG) in pregnancy
- NB: ABG should never be "normal" in pregnancy!
- Should have a respiratory alkalosis from blowing off their CO2 at higher rates.
- Should have a metabolic acidosis (compensatory).
- Many pregnant women will hyperventalate.
- Give them a bag in which to breath.
- Very hard to settle them down so important to give the bag quickly and pt will often become syncopous.
- Pt's ABG was:
- pH: 7.44 (
- pCO2: 30
- BiCarb: 21
- paO2: 103
- Recall that O2 consumption increases in pregnancy.
- 15-20%
- Recall that minute ventilation (the amount of air breathed in over the course of one minute) is increased relatively more than the O2 consumption.
- This means that more air is breathed in and out than is necessary for the rate of oxygen consumption.
- This is the definition of hyperventilation!
- Recall the chemical equation: CO2 + H20 <=> H2CO3 <=> HCO3 + H
- Recall that hyperventilation gives off CO2, dragging the equation to the left.
- That is, pCO2 will be decreased.
- Therefore pregnant, hyperventilating women become alkalotic (decreased H+).
- That is, pH will be high (less H+).
- This is a respiratory alkalosis.
- Recall that the kidneys can excrete HCO3 to compensate for loss of CO2 (because of hyperventilation) and thus draw the equation back to the right.
- Thus we expect the serum HCO3 to be low.
- Recall that in pregnancy there is an increased oxygen carrying capacity (facilitated by RBC volume increased by 50%).
- Thus we expect the pO2 to be high.
- Given this respiratory alkalosis and metabolic (compensatory) acidosis, we expect:
- the pCO2 to be low: 26-32 mmHg (compared to non-pregnancy 38-45)
- the pH to be high (alkaline): 7.40-7.46 (compared to non-pregnancy 7.38-7.42)
- the HCO3 to be low: 18-21 mEq / L (compared to non-pregnancy 24-31)
- the pO2 to be high: 106-108 mmHg (compared to non-pregnancy 70-100)
- A high pCO2 is cause for alarm in the asthmatic pregnant woman.
- Also, pCO2 should be monitored carefully in the acutely infected pregnant woman because they are immune compromised and have very little respiratory reserve.
Measure | Non-pregnant | Pregnant | Change | Reason |
---|---|---|---|---|
pH | 7.38 - 7.42 | 7.4 - 7.46 | Higher | Because of the balance of respiratory alkalosis and (compensatory) metabolic acidosis. |
pCO2 (mmHg) | 38 - 45 | 26 - 32 | Lower | Because minute ventilation increases more than oxygen consumption (CO2 breathed off faster than oxygen consumed). |
pO2 (mmHg) | 70 - 100 | 101 - 106 | Lower | Because RBC volume is increased. |
HCO3- (mEq / L) | 24 - 31 | 18 - 21 | Lower | Because the kidneys are excreting HCO3- in an attempt to compensate for respiratory alkalosis. |
O2 saturation (%) | 95 - 100 | 95 - 100 | None |
- Importance:
- A normal pregnant woman has a compensated respiratory alkalosis (with a compensatory metabloic acidosis) and a diminished pulmonary reserve.
- Cause:
- Progesterone: relaxes the smooth muscle
- Diaphragm raised 4cm
CBC in pregnancy
- Plasma Volume and RBC Mass
- Plasma volume increases by about 50%
- RBC volume increases by about 30%
- Result:
- “Physiologic anemia of pregnancy”
- The mean Hgb is about 11.5 g/dl
- At 28 weeks, get new labs.
- Will likely need to start iron.
- Start at or below 10.
- Yucky tasting, makes woman feel horrible.
- Necessary for proper oxygenation.
Coagulation in pregnancy
- In pregnancy the pt is hypercoaguable
- This is the body's way to not die from bleeding when the parasite is ejected / ripped from the internal surface of the uterus.
- DIC is the number 1 cause of death in laboring women around the world.
- Not so much here in the US.
- Procoagulant’s are increased: I, VII, VIII, IX, X and Fibrinogen.
- Prevents Peripartum Hemorrhage
- Can lose 1500mL without blinking.
- Over 2000 mL lost, start worrying b/c coag factors are becoming deficient.
Renal System in pregnancy
- Bun & Serum Creatinine decreases by about 25%
- Low because of increased blood volume, increased GFR, increased blood flow to the kidneys
- Plasma osmolarity decreases by about 10 mOsm / kg H20
- Increase in tubal reabsorption of sodium
- Marked increase in renin and angiotensin levels
- But markedly reduced vascular sensitivity to their hypertensive effects
- Increased glucose excretion
- Fine during labor, a coping mechanism.
- Labs at 28 weeks detect gestational diabetes.
- Anatomic:
- Kidney size increases
- Kidney weight increases
- Ureteral dilation (right side greater than left side)
- Because of the angle of the uterus
- Bladder becomes an intra-abdominal organ
- Hemodynamic:
- GFR increase by 50%
- Renal plasma increased by flow by 75%
- Creatinine Clearance increases to 150-200 cc / min
- Most important kidney function test in pregnancy
- Swollen Ankles:
- Recall that the Plasma Volume Increases 50% in pregnancy.
- Recall that there is decreased Systemic Vascular resistance in pregnancy.
- Recall that there is renal retention of Na and H20 in pregnancy.
- Leads to a total increase of 6 – 8 L in total body H20!
- 2 / 3rd extracellular
- 1 / 3rd intravascular
- Intravascular increase is put in the "dependent" (affected by gravity) areas like the lower venous system.
- Hard to move fluids through the venous system.
Case: Caring Family
- The patient’s husband lies her flat in an effort to keep her comfortable.
- The fetus’s FHTs (fetus heart tones) drop to 80.
- But, the ROCK STAR medical student wedges the patient quickly on her left side and the FHT’s recover quickly!
- Turns her off the vena cava.
- Aids in venous return to the heart and therefore to oxygenation of blood for mom and baby.
- What happened to the cared-for mother?
- Gravid Uterus placed pressure on the IVC which resulted in decreased “utero-placental blood flow.”
- Cardiac output falls
- Blood is shunted to the brain and
- Blood is shunted away from the uterus and placenta
- This causes a reflex fetal bradycardia
Importance of Physiology
- All can be abnormal in the Non-Pregnant state:
- Decreased BP
- Swollen ankles
- CXR: cardiomegaly, leftward deviation
- Systolic Ejection murmur
- Dyspnea
- Anemia
- Hypercoaguable
- NORMAL for Pregnancy
Maternal Physiology Review