Pregnancy: Physiologic Changes and Pathophysiology Flashcards
What is the average healthy weight gain during pregnancy?
25 - 35 lbs, or 12 kg
What causes increase in body weight during pregnancy?(3)
Increased size of uterus (4kg)
Increased blood volume and interstitial fluid (4kg)
Increased fat and protein deposit (4kg)
How much weight is gained in the 1st, 2nd, and 3rd trimesters?
1st: 1-2 kg
2nd, 3rd: 5-6 kg
How much is VO2 increased during pregancy and what is the primary cause?
Note: VO2 is oxygen consumption.
~ 60%
Primarily: Needs of fetus, uterus, and placenta
Secondarily: Increased work of mom
What are anatomical physiological changes during pregancy? (4)
Thoracic cage circumference increases
Vertical measurement of chest decreases
Capillary engorgement of oropharynx, nasal mucosa, larynx
Dilation of large a/w to allow more ventilation
What can we expect with nasal instrumentation to a pregnant patient?
increased epistaxis
What are respiratory mechanics in pregnant women? (2)
More diaphragmatic excursion
Less thoracic cage movement
What are cardiovascular changes in a pregnant woman? (5)
increased blood volume
increased cardiac output
increased HR
increased stroke volume
right shift of oxyhemoglobin dissociation curve
How much is blood volume increased at full-term?
~1 liter
Note: BV increase mostly due to plasma.
Most CO output changes is due to stroke volume. True or false?
True
Note how CO increases 125% at birth.
What are the hemodynamic changes at full-term gestation relating to:
CO
SV
HR
Contractility
SVR
PVR
Cardiac Output +40%
Stroke Volume +30%
Heart Rate +15 (15-20 bpm)
Contractility negligible
SVR - 20%
PVR - 30%
What is the p50O2 in mmHg?
Fetal
Normal
Parturient (mom)
19
27
30
Note: P50 = 50% of Hb is saturated with oxygen.
What are uterine blood flow increases at full-term gestation?
Normal 50 ml/min to 600-700 ml/min
What are other hemodynamic changes at term gestation besides increased uterine blood flow?
Renal plasma flow increase
Skin blood flow increases 3-4 times
Blood pressure falls
- Systolic 6-8%
- Diastolic 20-25% early, normal at full-term
What are factors that impair uterine blood flow? (5)
- Decreased perfusion pressure
- Decreased uterine arterial pressure
- Increased uterine venous pressure
- Increased uterine vascular resistance
- Exogenous vasoconstrictors
What is important to know regarding uterine blood flow?
It is pressure dependent and not auto-regulated!
What factors decrease uterine arterial pressure? (3)
Supine position due to aortocaval compression
Hemorrhage, hypovolemia
Hypotension from drugs or sympathetic blockade
What factors cause increased uterine venous pressure, which in turn impairs uterine flow? (4)
Vena caval compressions
Uterine contractions
Drug-induced hypertonus (oxytocin, local anesthetics)
Skeletal muscle hypertonus (seizures, Valsava)
What factors cause increased uterine vascular resistance which in turn impair uterine blood flow?
Endogenous vasoconstrictors
- Catecholamines (stress)
- Vasopressin (in response to hypovolemia)
Exogenous vasoconstrictors
- Epi
- Phenyl > ephedrine
- Local anesthetics in high conc.
What is of greater concern, aortic or caval compression?
caval compression
What position results in complete caval compression?
How much does it decrease CO?
supine, begins at 13 weeks
25-40%
Note: lateral decubitus partially obstructs the vena cava, but collateral circulation can compensate.
Lateral decubitus causes little aortic compression. True or false?
True.
At what spinal levels does significant compression of the aorta occur?
L3-L5
What are the greatest changes in lung volumes at full-term?
Tidal volume increases 40%
FRC decreases 20%
What changes in respiratory physiology occur at full-term? (3)
Respiratory Rate +0-15%
Minute ventilation + 40%
Alveolar ventilation + 40%
What is PaCO2 in a non-pregnant vs. a pregnant woman?
Normal: 40mmHg
Pregnant (all trimesters): 30mmHg
How does HCO3 change in a non-pregnant vs. pregnant womam?
Normal HCO3: 24 mmHg
Pregnant (full-term): 20 mmHg
What happens to pH in a pregnant woman?
Slightly increases
What causes CNS depression in a pregnant woman?
progesterone
Note: As a result, less local anesthetics are needed for spinals and epidurals.
Because the CNS is depressed, MAC and amount of local anesthetics needed is decreased as much as ___-____%
30 (LA)-40 (MAC)%
What are special considerations for spinals and epidurals in pregnant women? (2)
Engorged venous plexus can increase risk of puncturing epidural vein or intravascular injection
Decreased CSF volume causes enhanced cephalad spread of LA
What are renal changes relating to:
Blood flow
GFR
BUN/Cr
BF increases
GFR increases
BUN/Cr decrease
What are hepatic changes in pregnant women relating to:
Blood flow
Plasma cholinesterase
Hepatic function and blood flow remain largely unchanged
Plasma cholinesterase decreases, but not signicantly for our purposes
What are hepatic related issues that may present to the pregnant woman?
Acute fatty liver
Gallstone formation more likely due to concentration of bile
What are changes in colloid (a portion of plasma proteins) osmotic pressures in the pregnant pt?
Decreases by 5mmHg at term
What are coagulation changes that occur with pregnant women relating to:
platelet turnover
clotting
fibrinolysis
all increase
By how much does PT and PTT change during pregnancy?
both decrease by 20%
Note: Normal PT is 10-14 sec and PTT is 25-38 sec.
What are changes to the endocrine system with pregnant women relating to the:
thyroid
parathyroid
insulin
Hyper or hypo-thyroidism
Increased PTH
Insulin-resistance in 3rd trimester
What are GI changes during pregnancy? (7)
Delayed gastric emptying
Decreased GI mobility
Decreased gastric pH
Decreased gastric acid secretion
Silent regurgitation
Increased gastric volume
INCREASED ASPIRATION RISK
What are general anesthesia concerns relating to the pregnant pt? (4)
Smaller ETT required
Increased shunt when supine
Increased rate of denitrogenation
Increased rate of decline of PaO2 during apnea
When should you proceed with surgery in the pregnant pt?
If elective, postpone until postpartum.
If greater than minimal increased risk to mother, proceed with surgery.
What are the phases in Stage 1 labor?
What are the cervical dilations for each?
Latent phase: onset of labor, 2-4 cm
Active phase: increased frequency of contractions, up to 10 cm
What is Stage 2 of labor?
Full cervical dilation→Fetal descent→delivery of fetus
What is Stage 3 of labor?
Delivery of the placenta
How much blood is dispaced from the uterus to the central circulation with each contraction?
300-500ml
What drug is given to induce labor?
Pitocin (Oxytocin)
What drugs are given after delivery to contract the uterus back down to prevent hemorrhage?
Methergine
Hemabate
What drug is given for pre-eclampsia?
Magnesium
What are pregnancy induced diseases? (6)
- Pre-eclampsia (pregnancy-induced HTN)
- Eclampsia (severe preg-induced HTN)
- Acute fatty liver
- Amniotic fluid embolism
- Thromboembolic disease
- DVT/pulmonary embolus
What is preeclampsia?
BP > 140/90, or >20% above baseline
Proteinuria and/or Edema
Usually presents 20 weeks after gestation
What is HELLP syndrome?
Hemolysis
Elevated Liver Enzymes
Low Platelets
Note: Only 2 of 3 conditions are needed.
What is eclampsia?
Preeclampsia with seizures
Preeclampsia and HELLP syndrome is an _______ situation.
emergent
What is the treatment for preeclampsia?
Generally resolves after delivery, but others may require ICU if pulmonary/renal issues.
What are the symptoms of eclampsia? (5)
profound HTN
headache
double vision
hyperreflexia
convulsions
What is the differential diagnosis for eclampsia?
Amniotic fluid embolism which leads to hypoxia and seizures
IV injection of LA but no HTN will be present in this instance
What are anesthetic considerations for pts with eclampsia?
Secure the a/w in event of seizure!
Smaller tube
RSI
What are neurological complications of PIH (pregnancy-induced HTN)? (5)
Headache
Visual disturbances
Hyperexcitability
Seizures
Intracranial hemorrhage
What are cardiovascular complications of PIH? (3)
decreased intravascular volume
increased arteriolar resistance
heart failure
What are hepatic complications of PIH? (3)
elevated liver enzymes
hematoma
hepatic rupture
What are renal complications of PIH? (4)
Proteinuria
Na retention
Decreased GFR
Renal failure
What are hematologic complications of PIH? (2)
Coagulopathy
Microangiopathic hemolysis
Acute Fatty Liver is common/rare.
Rare, 1/12,000 of deliveries but deadly.
What are the symptoms of acute fatty liver?
N/V
Epigastric pain
Jaundice
Decreased serum glucose
Increased liver enzymes
Note: Presents in 3rd trimester.
What is the treatment of acute fatty liver? (3)
Supportive
FFP, platelets, albumin
Give vitamin K
Note: Hope that pts do not go into DIC (excessive thrombin).
When is the onset of amniotic fluid embolism?
What are the symptoms? (6)
During delivery
Sudden CV collapse
Profound hypotension
Cyanosis
Seizures, Coma
DIC
Presents as anaphylaxis
Note: Rare, but deadly.
What is the treatment of amniotic fluid embolism?
Deliver the baby
Provide supportive care
What is DIC (disseminated intravascular coagulation)?
Widespread systemic activation of coagulation, resulting in intravascular formation of fibrin and ultimately thrombotic formation occlusion of small and mid-sized vessels.
What are the causes of DIC?
Sepsis
Trauma
Obstretics
Note: Treatment is supportive and treat underlying cause.
What is thromoembolic disease?
Pregnancy causes an increase in most clotting factors.
Gravid uterus causes venous stasis.
What are risk factors for thromboembolic disease? (4)
Smoking
Obesity
Age
Genetics
How do we diagnose DVTs?
What can they ultimately cause?
What is the treatment?
Doppler
Pulmonary embolus
Massage, heparin therapy
Note: Heparin is OK for the baby.
What are anesthetic considerations for respiratory patients with asthma and cystic fibrosis, for example?
Do not go above T8 with the epidural due to effects on breathing!
Is synthroid OK for the pregnant woman?
Yes
Is glucophage OK for the pregnant woman?
Yes, oral hypoglycemics are fine.
What are anesthetic considerations for pregnant women with renal disease?
Increased risk for HTN
Decreased fluid clearance
What are anesthetic considerations for epileptic pregnant patients?
More seizures
Decrease meds due to increased risk of cleft lip/palate
What are anesthetic considerations for myasthenia gravis pregnant pts?
Some pts get better, worse, or stay about the same
Stress can exacerbate MG
Resistance to anticholinesterases?
What are the anesthetic considerations for pregnant women that are morbidly obese?
GI issues
A/w issues
Diabetes