Maternal Physiology (Exam 2) Flashcards
Gravida refers to what?
Number of pregnancies (not babies)
Para refers to what?
numbers of births (>20weeks)
What is G0P0?
Nulligravida/Nulliparous
- No pregnancies
- No births
What would G3P2 refer to?
Multigravida/ Multiparous
- 3 pregnancies
- 2 births
How long is a pregnancy? When is a gestation “term”?
- 40 weeks
- Term at 37 - 40 weeks
What are the components that result in the 12kg weight gain typical of pregnancies?
- Uterus & Amniotic Fluid = 1kg
- Fetal/Placental Weight = 4kg
- New Fat/Protein stores = 4kg
- Blood volume increase = 2kg
lol this is 11kg…
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 by 24 weeks)
Does plasma volume or RBC volume increase more during pregnancy?
Both increase but plasma volume increases more.
Why does blood volume increase during pregnancy?
To counteract delivery blood loss
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.
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 = ↑ Preload = ↑ SV
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
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%)
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
- ST segment depressed
- QT interval increased
What are the most common EKG abnormalities in pregnant patients?
Tachydysrhythmias
(Sinus tach, PAC, PVC)
What valvular changes are typical of pregnancy?
- Tricuspid & Pulmonic regurgitation (>90% pts)
- Mitral regurgitation (~25% 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.
What exacerbates aortocaval compression?
Anesthesia due to vasodilation.
What are the s/s of aortocaval compression?
- Fetal Distress
- Tachycardia → bradycardia
- N/V
- Pallor
- Syncope
What is the treatment for aortocaval compression?
LUD (Left Uterine Displacement)
Done by tilting the patient to the left.
What cardiovascular changes occur during the first stage of labor?
- CO increases before & 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 during the second stage of labor?
CO increases by 60 - 80% due to
- Relief from vena cava obstruction
- Uterine contracts blood into circulation
When does CO return to normal post-delivery?
24 hours
What happens to the airway in obstetric patients?
What are the anesthetic implications of edematous airways?
- Smaller ETT necessary
- Avoid NGT/Nasal trumpets (bloody nose)
- Airway obstruction risk increases
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 (Both ERV and RV are decreased).
What causes the earlier closure of small airways in the obstetric patient?
Elevated Diaphragm → more negative pleural pressure = small airway closure
What position results in a more profound decrease in FRC?
Supine
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?
- 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.
How do minute ventilation and alveolar ventilation change in pregnancy?
Both Increase.
RR increases by 1-2 breaths per minute, mediated by hormonal changes.
How do ABG’s change during pregnancy?
What does this result in?
PaCO₂ decreases by 8-10 mmHg
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
- 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 2.5 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
- > 13 means you need to watch for pre-eclampsia.
What changes occur with platelets during pregnancy?
- Normal 165 - 415
- No change or moderate decrease is typically seen with pregnancy.
Why do we care about platelets in obstetric patients?
Risk for epidural hematoma from neuraxial techniques.
Pregnancy produces a hypercoagulable or hypocoagulable state?
Hypercoagulable.
What coagulation factors increase due to pregnancy?
All of them, except II, V, XI, and XIII.
What coagulation factor has the most significant increase during pregnancy?
Factor 1 (Fibrinogen)
What is hyperfibrinogenemia?
Fibrinogen (Factor I) > 400mg/dL at term
- Increased clotting efficiency
- Impaired fibrinolysis
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)
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
What occurs with WBC’s during pregnancy?
- Increase steadily to 9 - 10 throughout pregnancy
- Spike up to 34 during labor
How does immune function change during pregnancy?
- Leukocyte function is impaired
- Antibody titers can decrease
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.
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?
↑ risk of esophageal varices due to increased portal vein pressure.
↑ Liver enzymes and cholesterol
What occurs with serum albumin during pregnancy?
serum albumin decreases
What occurs with pseudocholinesterase levels during pregnancy?
pseudocholinesterase decreases by 25 - 33% during the peri-delivery timeframe.
*Usually still okay to give Sux**.
When can cholestasis occur to parturient patients?
3rd trimester
What are the s/s of cholestasis?
- Pruritis
- ↑ bilirubin
- ↑ LFTs
What are the consequences of cholestasis in obstetric patients?
- ↑ risk of cholelithiasis
- ↑ risk of cholecystectomy
- ↑ risk of cholestasis in subsequent pregnancies
During pregnancy the kidneys see a _____ increase in renal blood flow.
75%
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
What would a finding of 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%
Hypothyroidism 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 (200% by term)
- ↑ plasma endorphins
How does the anterior pituitary change during pregnancy?
- 300% increase in size
- ↑ Prolactin secretion
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 hormone is responsible for breast milk letdown and is known as the “bonding” hormone?
Oxytocin
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
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.
