OBGYN - Maternal-Fetal Physiology

From Iusmicm

(Difference between revisions)
(OjTKwZ Very informative post.Really looking forward to read more.)
 
(10 intermediate revisions not shown)
Line 1: Line 1:
-
=Maternal-Fetal Physiology=
+
OjTKwZ Very informative post.Really looking forward to read more.
-
 
+
-
==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.
+
-
 
+
-
 
+
-
*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
+
-
 
+
-
==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.
+
-
 
+
-
 
+
-
http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/004f.gif
+
-
http://www.glowm.com/resources/glowm/graphics/figures/v3/0260/001f.gif
+
-
 
+
-
 
+
-
*So '''dyspnea ''is'' normal with pregnancy'''.
+
-
 
+
-
{|border=1
+
-
!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'''.
+
-
 
+
-
{|border=1
+
-
!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==
+
-
http://mypage.iu.edu/~pbaenzig/medschoolfiles/icm/obgyn/Pages_from_111202_OBGYN_4_Maternal_Fetal_Physiology_Slides.png
+

Current revision as of 18:11, 15 December 2013

OjTKwZ Very informative post.Really looking forward to read more.

Personal tools