Maternal Physiology (Exam II) 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 ea
- Fetal/Placental Weight = 4kg
- New Fat/Protein stores = 4kg
- Blood volume increase = 2kg
this is the minimal weight gain expected
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)
retaining water, feeling bloated
Does plasma volume or RBC volume increase more during pregnancy?
Both increase but plasma volume increases more.
dilutional anemia
Why does blood volume increase during pregnancy?
To counteract delivery blood loss
How much blood can be lost in a vaginal delivery?
C-section?
~500mL
~800mL
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 CO in the pregnant patient?
↑ Plasma Renin = ↑aldosterone = ↑ Preload = ↑ SV = ↑ CO
↑ Na reabsorption & water retention = ↑ plasma volume
What causes the increased plasma renin activity & increased aldosterone in the pregnant patient?
- Pregnancy Hormones: estrogen & progesterone
How much does uterine blood flow increase during pregancy?
Baseline = 50 mL/min
Term = 700 mL/min
10-20x 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 and ↓ in SVR?
- Progesterone
- Prostacyclin
- Relaxin
- Estrogen
the arterial bed of the uterus is maximally dilated at term
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 Ventricular Hypertrophy (as much as 50%)
this accomodates the increase in blood volume
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
LAD - I & aVL positive, II & aVF negative
What are the most common EKG abnormalities in pregnant patients?
Tachydysrhythmias
(Sinus tach, PAC, PVC)
What are some causes of tachydysrhythmias in pregnant patients?
- change in cardiac ion channel conduction
- increase in cardiac size
- changes in autonomic tone
- hormones
- Anxiety/exercise triggered
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 rush of large blood volume into very compliant left ventricle.
What heart sound disappears at term?
4th heart sound
low-pitched sound that coincides w/ late diastolic filling of the ventricle d/t atrial contraction
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 hemodynamic change occurs in the supine position of a pregnant woman?
When can it begin to occur in pregnancy?
Aortocaval compression
Uterus compresses great vessels (inferior vena cava, aorta)
Occurs as early as 13-16 weeks.
What exacerbates aortocaval compression?
Anesthesia - due to vasodilation.
Epidural/Spinal & Sympathectomy
What is the physiology of aortocaval compression?
- ↓ venous return to RA
- ↓ CO
- HoTN
- ↓ uterine blood flow
- ↓ perfusion to fetus
ensure pregnant mom maintains normal BP
What are the s/s of aortocaval compression?
- Fetal Distress
- Tachycardia → bradycardia
- N/V
- Pallor
- Syncope (LOC)
What is the treatment for aortocaval compression?
LUD (Left Uterine Displacement)
Done by tilting the patient to the left.
Can tilt the table to the left or use a hip bump
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
body working harder and harder
What cardiovascular changes occur immediately after delivery?
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
begins to decline within 10 minutes of delivery
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
- mallampati class may worsen, even during labor
How does the hormone estrogen affect 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 affect the obstetric patient’s pulmonary system?
- ↑ respiratory center sensitivity to CO₂
- Bronchodilates
- Causes edematous airways (hyperemia)
How does the hormone Relaxin affect the obstetric patient’s pulmonary system?
Causes ligamentous attachments to lower ribs to relax.
- subcostal angle increases
- widened AP & transverse diameter of chest wall.
barrel chest - makes up for the fact that the gravid uterus is pushing up on diaphragm & shortening the lungs
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.
FRC = ERV + RV
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 → negative pleural pressure becomes more positive = small airway closure
What position results in a more profound decrease in FRC?
Supine
- @ risk of atelectasis
- preoxygenation important!!
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
r/t the West Perfusion Zones
How much does O₂ consumption increase by at term?
What causes the increase in O2 consumption?
20%
Due to increased metabolism of mom & baby, increased work of breathing, and increased cardiac workload.
What are possible causes of dyspnea in pregnancy?
- Increased respiratory drive (progesterone & estrogen mediated)
- increased O2 consumption
- Decreased PaCO2
- Larger pulmonary blood volume
- Anemia (dilutional)
- 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.
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 (hyperventilation)
- O₂ consumption increases
- Maternal lactate increases
- Aerobic requirements increase
Supplemental O₂ might be necessary.
What hematologic changes occur during pregnancy with Hgb and Hct?
- 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
- > 13 means you need to watch for pre-eclampsia.
What type of anemia is common in pregnancy?
Iron deficiency anemia
What changes occur with platelets during pregnancy?
- Normal 165 - 415
- No change or moderate decrease is typically seen with pregnancy.
What Plt count is considered thrombocytopenic in pregnancy?
What are 3 possible causes?
- < 150,000 mm3
1. Idiopathic
2. Hypertensive disorder of pregnancy (Pre-eclampsia - HELLP)
3. Gestational < 150,000K
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
protects against hemorrhage, risk for 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)
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 - 11K throughout pregnancy
- Spike up to 34K during labor
How does immune function change during pregnancy?
- Leukocyte function is impaired
- Antibody titers to certain viruses can decrease (measles, influenza A, herpes simplex)
may see autoimmune disease symptom improvement
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.
RSI up to 4 weeks PP
What is Mendelson’s Syndrome?
Aspiration pneumonitis & inflammatory response of lung parenchyma
What puts one at greater risk of Mendelson’s syndrome?
- gastric pH < 2.5
- > 25mL gastric volume
give bicitra
Uterus takes ____ weeks to return to normal size.
6
What changes occur in the liver during pregnancy?
↑ risk of esophageal varices due to increased splanchnic, portal, & esophageal venous pressure
↑ Liver enzymes and cholesterol
What occurs with protein during pregnancy?
- Decreased total protein
- Decreased albumin-globulin ratio
Colloid oncotic pressure decreases
What occurs with pseudocholinesterase levels during pregnancy?
What is the impact of this?
When do they return to normal?
pseudocholinesterase decreases by 25 - 33% during the peri-delivery timeframe.
*Usually still okay to give Sux (won’t cause prolonged paralysis)
returns to normal 2-6 wks PP
What is cholestasis?
biliary stasis & increased bile secretion
increased risk for cholelithiasis
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%
vasodilation in renal system = decreased SVR
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% (increased risk of difficult airway)
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
- Hyperplasia of lactotrophic cells =↑ Prolactin secretion (prep for breastefeeding)
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 musculoskeletal changes does Relaxin cause?
- increased joint mobility (sacroiliac & knee pain)
- overstretching of joints possible
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/back 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 in the spinal cord
- ↑ plasma endorphins
What occurs with the epidural space in pregnant women?
- ↑ Venous plexus volume (higher risk for venous puncture in epidural)
- ↓ 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.
not usually clinically signifanct
