Exam 2: Maternal Physiology Flashcards
Pregnancy is ____ weeks, ____ trimesters, and a term gestation is ____ - ____ weeks
Pregnancy is 40 weeks, 3 trimesters, and a term gestation is 37-40 weeks
anything before 37 weeks is considered preterm
Parturient refers to what
one who is preggers/in labor
Gravida refers to what?
Number of pregnancies (not babies)
Para refers to what?
numbers of births (including stillbirths >20weeks)
What is G0P0?
Nulligravida/Nulliparous
- No pregnancies
- No births
What would G3P2 refer to?
Multigravida/ Multiparous
- 3 pregnancies
- 2 births
What are the components that result in the 12kg weight gain typical of pregnancies?
- Uterus & Amniotic Fluid = 1kg each
- Fetal/Placental Weight = 4kg
- New Fat/Protein stores = 4kg
- Blood volume increase = 2kg
Do women of all BMI’s gain weight the same during pregnancies?
No
How much does total blood volume increase during pregnancy?
30 - 35% increase
When does the increase in total blood volume of the typical pregnant woman occur?
8 - 32 weeks (Majority of increase by 24 weeks)
Does plasma volume or RBC volume increase more during pregnancy?
Both increase but plasma volume increases more.
-therefore we may see a little bit of dilusional H&H (usually not super significant)
Why does blood volume increase during pregnancy?
To counteract delivery blood loss
- on average loss 500mL for vaginal delivery and 800mL for C-section delivery
Approximately when does maternal blood volume return to normal post-delivery?
6 weeks
Compare the blood volume of a pregnant patient and a non-pregnant patient in mL/kg.
Non = 65mL/kg
Pregnant= 85-90 mL/kg
CO will increase by ____% by term pregnancy
40%
In regards to hemodynamics, by 6 weeks there will be an increase in maternal ____ and by 8 - 10 weeks there will be an increase in _____.
Heart Rate : Stroke Volume
What is the mechanism for increased Stroke Volume in the pregnant patient?
↑ Plasma Renin = ↑aldosterone = ↑Na+ reabsorption (↑water retention) = ↑ Preload = ↑ SV
therefor increased CO
How much does uterine blood flow increase during pregancy?
Baseline = 50 mL/min
Term = 700 mL/min
20x increase!
What is the cause of the pregnancy symptoms of warm skin, flushing, and itching?
3-4x increase in skin blood flow
-d/t increase in CO
What changes in SVR occur in pregnancy?
20% lower
What hormones are responsible for maternal vasodilation?
- Progesterone
- Prostacyclin
- Relaxin
- Estrogen
Pregnancy is a ____ flow, _____ resistance state.
High flow : low resistance
↑ CO and ↓ SVR
Do the following increase or decrease during pregnancy?
- Blood volume
- Cardiac Output
- SVR
- Heart rate
- ↑ Blood volume
- ↑ Cardiac Output
- ↓ SVR
- ↑ Heart rate
What changes are seen in a maternal heart due to pregnancy?
Eccentric Hypertrophy (as much as 50% increase in LV mass at term)
How does the heart shift due to pregnancy?
Why does this occur?
- Heart shifts anterior and leftward due to diaphragmatic elevation.
Where does the point of maximal impulse for auscultation shift in a pregnant patient?
4th ICS mid-clavicular line
What EKG changes are seen in a pregnant patient?
- Left Axis shift in 3rd trimester
- Lead III T-wave inversion
- PR interval shortened (d/t ↑ SNS in third trimester which leads to an accelerated AV node conduction activity)
- ST segment depressed
- QT interval increased
What are the most common EKG abnormalities in pregnant patients?
Tachydysrhythmias
(Sinus tach, PAC, PVC)
Caused by cardiac ion channel conduction, increases in cardiac size, changed in autonomic tone and hormones
What valvular changes are typical of pregnancy?
- Tricuspid & Pulmonic regurgitation (seen in >90% pts d/t extra fluid)
- Mitral regurgitation (~25-30% of pts)
These typically reverse postpartum.
What heart sound is often heard in the 3rd trimester?
What causes this?
Ventricular Gallop
Due to inrush of large blood volume into very compliant left ventricle.
What heart sound disappears at term?
4th heart sound
What murmur can occur due to cardiac enlargement?
Where is this best heard?
- Grade II SEM (systolic ejection murmur)
- Heard right side of heart, near sternal border
What occurs in the supine position of a pregnant woman?
Aortocaval compression
Uterus compresses great vessels.
Occurs as early as 13-16 weeks. (usually just when the weight of the fetus can compress the vessels)
What exacerbates aortocaval compression?
Anesthesia due to vasodilation. (epidurals and spinals)
Steps of aortocaval compression
- decreased venous return to RA
- decreased CO
- HoTN
- decreased Uterine blood flow
- and therefore decreased perfusion to fetus
What are the s/s of aortocaval compression?
- Initially Tachycardia → bradycardia
- N/V
- Pallor
- Syncope
- Fetal Distress
I Please Need Fucking Sleep
What is the treatment for aortocaval compression?
LUD (Left Uterine Displacement)
Done by tilting the patient to the left.
chart this
What cardiovascular changes occur during the first stage of labor?
- CO increases between & during contractions
- HR increases
- Autotransfusion of 300-500mls from uterus to general circulation w/ each contraction.
What cardiovascular changes occur during the second stage of labor?
CO increases by 50% due to:
- Pushing effort
- ↑ SV & HR
What cardiovascular changes occur Immediately after delivery?
CO increases by 60 - 80% due to
- Relief from vena cava obstruction
- Uterine continues to contract which releases blood into systemic circulation
When does CO decline and then return to normal post-delivery?
- CO declines about 10 min after delivery
- CO returns to normals 24 hours after delivery
What happens to the airway in obstetric patients?
Lots of edema
Avoid nasal trumpets with preggers
What are the anesthetic implications of edematous airways?
- Smaller ETT necessary
- Avoid NGT/Nasal trumpets (bloody nose)
- Airway obstruction risk increases
- mallampati class may worsen even during labor
- unanticipated airway difficulties may arise (have backup airway stuff)
How does the hormone estrogen effect the obstetric patient’s pulmonary system?
Estrogen will ↑ number and sensitivity of progesterone receptors in the respiratory center of the brain.
How does the hormone Progesterone effect the obstetric patient’s pulmonary system?
- ↑ respiratory center sensitivity to CO₂
- Bronchodilates
- Causes edematous airways
How does the hormone Relaxin effect the obstetric patient’s pulmonary system?
Causes ligamentous attachments to lower ribs to relax.
- subcostal angle increases
- widened AP & transverse diameter of chest wall.
Is Total Lung Capacity reduced or preserved during pregnancy?
Preserved.
Chest height is shortened but A-P dimension increases with barrel shape due to relaxin.
What is FRC?
Volume of air that prevents complete emptying of lungs and keeps small airways open.
What is ERV?
Volume of air that can be expired with maximum effort at the end of normal expiration.
What is RV?
Residual Volume = Volume of air in the lungs after ERV is expired
Uterine elevation of the diaphragm results in a ____% decrease in FRC.
20% ↓ in FRC at term (Both ERV and RV are decreased).
What causes the earlier closure of small airways in the obstetric patient?
Elevated Diaphragm → increased negative pleural pressure = small airway closure
Small airway closure d/t:
- decreased RV
- decreased ERV
- decreased FRC
What position results in a more profound decrease in FRC?
Supine
- diaphragm elevates even more and results in increased alveolar atelectasis
What happens if closing capacity exceeds FRC?
Small airway closure & V/Q mismatch leading to
O₂ desaturation.
What respiratory volumes are increased during pregnancy?
- VT ( increased CO₂ production = increased respiratory drive)
- IC (Inspiratory Capacity)
What respiratory volumes are unchanged by pregnancy?
- TLC (all lung volumes)
- VC (IC + VT + ERV)
How can pre-oxygenation be achieved?
- denitrogenate the residual lung capaticy and maximize the O2 storage in the lungs
- 3 - 5 VC breathes with tight face mask w/ 100% O₂
- 8 deep breaths at O₂ flow rate 10L/min over 1 min.
What FeO₂ (fraction of expired O₂) is desirable?
0.9 or greater
What positioning is helpful for preoxygenation?
20° Reverse Trendelenburg
How much does O₂ consumption increase by at term?
20%
Due to increased metabolism of mom & baby, increased work of breathing, and increased cardiac workload.
What ventilatory changes do we see during pregnancy?
- Dyspnea begins 1st trimester
- increased respiratory drive
- increased O2 consumption
- decreased PaCO2
- larger pulmonary blood volume
- anemia (plasma volume > than RBC volume)
- nasal congestion
How do minute ventilation and alveolar ventilation change in pregnancy?
Both Increase.
RR increases by 1-2 breaths per minute, mediated by hormonal changes
Tidal volume increases as well.
How do ABG’s change during pregnancy?
What does this result in?
PaCO₂ decreases by 8-10 mmHg (d/t hyperventialation)
PaO₂ increases by 5 mmHg
Respiratory Alkalosis is normal in healthy pregnancies.
Compare and contrast a typical ABG vs an obstetric ABG.
What pulmonary change occurs during the first stage of labor?
Minute ventilation increases by up to 140%.
What pulmonary change(s) occurs during the second stage of labor?
- V̇T goes up by 200%
- Maternal CO₂ decreases by 10 - 15
- O₂ consumption increases
- aerobic requirements increase
- Maternal lactate increases
Supplemental O₂ might be necessary.
What hematologic changes occur during pregnancy?
- Plasma volume increases more than RBC mass resulting in dilutional anemia.
- Hgb drops by 2.4 g/dL
- HCT decreases by 6.5%
What Hgb range do we like for maternal patients?
11 - 13 g/dL
- Less than 11 is abnormal (get type/cross)
- > 13 means you need to watch for pre-eclampsia (warning sign).
What kind of anemia do we see with pregnant pts?
- iron deficency anemia (Fe is needed to make RBCs)
- treated with oral iron formulations
What changes occur with platelets during pregnancy?
- Normal 165 - 415
- No change or moderate decrease is typically seen with pregnancy.
Thrombocytopenia is defined as ____
- Platelets <150
- Idiopathic
- HTN disorder in preggers
- could be gestational without abnormal plt function seen
Why do we care about platelets in obstetric patients?
Risk for epidural hematoma from neuraxial techniques.
give platelets before surgery if needed
Pregnancy produces a hypercoagulable or hypocoagulable state?
Hypercoagulable.
What coagulation factor has the most significant increase during pregnancy?
Factor 1 (Fibrinogen)
protective against blood loss
What is hyperfibrinogenemia?
Fibrinogen (Factor I) > 400mg/dL at term
- Increased clotting efficiency
- Impaired fibrinolysis
protects against hemorrhage, but risk for blood clots increases
What factors are increased at term gestation?
Will be on test
- I (Fibrinogen)
- VII (proconvertin)
- VIII (Antihemophilic factor)
- IX (Christmas factor)
- X (Stuart-Prower factor)
- XII (Hageman factor)
ways to remember:
1 fibrinogen (duh)
7 is everyone’s fav number - so its a PRO at CONVERTING people to love it
8 if you have hymolytic disease, you are factor 8 deficient
9 some kid has to celebrate 9 christmases because his parents got divorced so many times
10 stuart little (the orphan mouse) went through 10 families to find the perfect one
12 Hageman - its an old clotting factor because it startes the intrinsic cascade
What factors are unchanged at term gestation?
Will be on test
- II (Prothrombin)
- V (Proaccelerin)
What factors are decreased at term gestation?
Will be on test
- XI (Thromboplastin antecedent)
- XIII (Fibrin-stabilizing factor)
- PT & PTT ↓ by 20%
- Fibrinolytic activity overall decreases in 3rd trimester
Ways to remember:
11 PLASTER the THROMBIN all over the sides the alley (11 through the alley)
13 not unlucky when it STABILIZES you
What occurs with WBC’s during pregnancy?
- Increase steadily to 9 - 10 throughout pregnancy (normal)
- Spike up to 34 during labor
How does immune function change during pregnancy?
- Leukocyte function is impaired
- increased risk and severity of infection
- may see autoimmunie disease s/s improve
- Antibody titers can decrease to certain viruses
- Measles, Influenza A, herpes
All parturient patients are considered to be ____ stomach.
full
How does lower esophageal sphincter tone change throughout pregnancy?
- Tone decreases throughout pregnancy with the lowest tone occurring at term.
- LES tone normalizes at 4 weeks post-partum.
risk for aspiration duiring preg. but also up to 4-6 weeks postpartum
Gastric emptying during pregnancy and during labor
- During pregnancy: generally the same throughout pregnancy
- During Labor: Gastric emptying delayed
- Clear liquids ok
- solid foods generally not ok (can depend on the OB Dr. or the hospital)
What is Mendelson’s Syndrome?
Aspiration pneumonitis & inflammatory response of lung parenchyma
What puts one at greater risk of Mendelson’s syndrome?
- pH < 2.5
- > 25mL gastric volume
Uterus takes ____ weeks to return to normal size.
6
What changes occur in the liver during pregnancy?
size of liver ususally is unchanged
↑ risk of esophageal varices due to increased portal vein pressure.
↑ Liver enzymes and cholesterol
What do liver enzymes do during pregnancy?
Increased: serum aspartate aminotransferase, lactic dehydrogenase, and alkaline phosphatase
cholesterol increased too
What occurs with serum albumin during pregnancy?
- colloid oncotic pressure decreases
- decreased total protein
- decreased albumin-to-globulin ratio
What occurs with pseudocholinesterase levels during pregnancy?
pseudocholinesterase decreases by 25 - 33% during the peri-delivery timeframe.
- returns to normal 2-6 weeks postpartum
*Usually still okay to give Sux. make sure to check twitches
What is cholestasis?
- reversible
- biliary stasis and increased bile secretion
- increased risk for cholelethiasis
- high probablility of returning in subsequent pregnancies
- may have to have gallbladder out
When can cholestasis occur to parturient patients?
3rd trimester
What are the s/s of cholestasis?
- Pruritis
- ↑ bilirubin
- ↑ LFTs
During pregnancy the kidneys see a ____ increase in renal blood flow.
75% kidneys increase in size too
What are the results of increased renal blood flow during pregnancy?
- ↑ GFR
- ↑ Creatinine clearance
- ↓ Creatinine
- ↓ BUN
What BUN/Creatinine levels are typical of pregnant patients?
- BUN: 8 - 9 mg/dL at term
- Ct: 0.5 - 0.6 mg/dL at term
What changes in the urine can occur during pregnancy?
- Glycosuria common (Glucose reabsorption can’t keep up with ↑ GFR)
- Proteinuria normal
What would a finding of excessive proteinuria possibly indicate in a parturient patient?
preeclampsia
What would the following labs in a parturient patient suggest?
- BUN > 15mg/dL
- Creatinine > 1.0 mg/dL
- Creatinine Clearance < 100 mL/min
Abnormal renal function
Further evaluation required.
What occurs with the thyroid during pregnancy?
Enlargement by 50 - 70% (risk of difficult airway)
Hypothyroidism (10% of pts) may occur and require levothyroxine to prevent fetal issues.
Insulin resistance during pregnancy is the result of what hormone?
Human placental lactogen
Hormone that prepares the body for breastfeeding.
How does adrenal function change in the parturient patient?
- ↑ cortisol (100% increase in 1st trimester and 200% increase by term)
- ↑ plasma endorphins
How does the anterior pituitary change during pregnancy?
- 300% increase in size
- ↑ Prolactin secretion (hyperplasia of lactotrophic cells)
What causes increased acne seen in pregnancy?
↑ Prolactin secretion by adenophypophysis hyperplasia.
How does the posterior pituitary change during pregnancy?
Oxytocin secretion increases by 30% by term
- Stimulates contractions
- Breast milk letdown
- “Bonding hormone”
What kind of musculoskeletal changes occur with pregnancy?
Relaxin is released
- increased joint mobility: sacroiliac pain, knee pain
- overstretching of joints is possible (exercise caution)
What nerve pains are common with pregnancy?
- Sciatic
- Meralgia paresthetica
What is meralgia paresthetica?
- Compression of lateral femoral cutaneous nerve at exit site of pelvis)
Tingling, numbness, and burning on lateral aspect of the thigh.
What is the reason for lots of pelvic pain during pregnancy?
Lumbar lordosis w/ anterior pelvic tilt and narrowing of intervertebral spaces.
What CNS changes occur during pregnancy?
- ↑ CBF
- ↑ BBB permeability
- ↑ pain threshold
What is the mechanism for increased pain threshold for parturient patients?
- Progesterone activates κ-opioid receptors
- ↑ plasma endorphins
What occurs with the epidural space in pregnant women?
- ↑ Venous plexus volume
- ↓ CSF volume (greater spread of LA)
What is the result of increased venous plexus volume?
Engorged epidural veins and a higher risk of venous puncture during epidural placement.
What is the result of decreased CSF volume on local anesthetic spread?
↑ spread of LA
T/F. A higher total dose of local anesthetic is necessary to produce the same level of neuraxial block in parturient patients.
False. A lower total dose of LA is necessary.
Parturient patients have an increased sensitivity to ____ neuromuscular blockers.
Non-depolarizing.
Roc & Vec
What can happen with succinylcholine administration in a pregnant patient?
Prolonged paralysis due to ↓ pseudocholinesterase activity.
doesn’t usually happen with 1 dose of sux, but is can so check twitches
