Pregnancy Flashcards
What is the mean weight gain during pregnancy?
17%
avg 12 kg
The fetus represents what portion of mean weight gain?
1/3
How does weight gain differ in each trimester?
1st Trimester: 1-2kg (mostly water)
2nd & 3rd Trimester: 5-6kg each
What happens to oxygen consumption (VO2) during pregnancy?
Increases approx. 30%
-Predominantly metabolic needs of fetus, uterus, and placenta
Why are pregnant women at an increased risk for epistaxis?
Capillary engorgement of the oropharynx, nasal mucosa, and larynx
What happens to the large airways in pregnant women and what effect does it have on airway conductance?
Dilation of large airways increases airway conductance
What anatomical changes are seen in regards to respiration?
Elevated position of diaphragm
Thoracic cage increases 5 - 7 cm
Vertical measurement of chest decreases 4 cm
What happens to blood volume during pregnancy?
Increases from 60-65 mL/kg to 90 mL/kg
When is blood volume highest during pregnancy?
During the third trimester
What happens to cardiac output during pregnancy?
Increases 40%
When is cardiac output highest for pregnant women?
Immediately postpartum
What effect does term gestation have on stroke volume and heart rate?
Stroke Volume: +30%
Heart Rate: +15-30%
What effect does term gestation have on SVR and PVR?
SVR: -20%
PVR: -30%
How do the fetal and parturient oxyhemoglobin dissociation curves compared to a normal curve.
Fetal = L shift (greater binding affinity) P50 = 19
Parturient = R shift P50 = 30
What happens to uterine bloodflow at term gestation?
Increases from 50 mL/min to 600-700 mL/min
80% of increase to placenta
How is uterine bloodflow regulated?
PRESSURE DEPENDENT
NOT Auto-regulated
What happens to renal plasma flow during gestation?
Increases
-Highest at 26 weeks (+85%)
What happens to skin bloodflow term gestation?
Increases 3-4x nonpregnant flow
What happens to systolic and diastolic blood pressures at term gestation?
Systolic: - 6-8%
Diastolic: - 20-25% early (normal at term)
What is caval compression and when does it begin?
Complete or partial obstruction of the interior vena cava - decreasing venous return
(25-40% CO decrease)
-Begins at 13 to 16 weeks
How is caval compression alleviated?
Left uterine displacement
What happens to tidal volume and FRC at term gestation?
Tidal Volume: +40%
FRC: -20%
What effect does time gestation have on respiratory rate and ventilation?
RR: +0-15%
Minute and Alveolar Ventilation: +40%
What effects do the respiratory changes of the parturient have on the anesthetic plan?
Increased VO2 and decreased FRC lead to faster desaturation
What effect does pregnancy have on MAC requirements?
Decreases progressively up to 40%
What effect does pregnancy have on the CNS?
Progesterone mediated CNS depression
What affects this pregnancy have on the liver?
Hepatic function and blood flow remain largely unchanged
What effect does pregnancy have on colloid osmotic pressure?
Decreases by 5 mmHg at term
Describe the effects of pregnancy on coagulation
Accelerated, compensated coagulation
–Enhanced platelet turnover, clotting, fibrinolysis
PT & PTT: -20%
Bleeding time: -10%
What sort of endocrine changes can be seen in the pregnant patient?
- Thyroid hypertrophy
- Parathyroid and Ca2+ changes (important for fetus)
- Insulin resistance (degree varies)
What sorts of GI changes are seen in the parturient?
Why are these important?
Delayed gastric emptying
Increased gastric volume
Decreased gastric pH
Decreased GI mobility
** Increased aspiration risk **
Pregnancy predisposes women what to GI disturbances?
GERD
Esophagitis
Gallstone formation
At term, pregnant women require more or less local anesthetics?
Local anesthetic requirement reduced up to 30%
What is the average fetal oxygen consumption at term?
21 mL/min
Transfer of oxygen to the placenta is dependent upon what two factors?
Ratio of maternal uterine bloodflow to fetal umbilical bloodflow
20% of women at term develop supine hypotension syndrome. How is it characterized?
Hypotension associated with pallor, sweating, or N/V
Describe the 3 stages of labor
Stage 1: Onset of true labor and ends with complete cervical dilation
Stage 2: Full cervical dilation -> fetal descent -> delivery of fetus
Stage 3: Delivery of placenta
The first stage of labor is divided into the latent and active phase. How are these phases characterized?
Latent Phase: Water breaks, progressive cervical effacement and minor dilation (2-4cm)
Active Phase: Increased frequency of contractions and cervical dilation (up to 10 cm)
What effect does labor have on minute ventilation and oxygen consumption?
MV increases up to 300%
VO2 increases 60% above third trimester values
At what point during labor and delivery is there the greatest strain on the heart?
Immediately after delivery
-increases cardiac output as much as 80% above prelabor values
How do contractions place an additional burden on the heart?
-300-500mL blood displaced from uterus -> central circulation with each contraction
What effects do inhalational agents and N2O have on uterine activity and labor?
Volatile anesthetics depress uterine activity equally at equipotent doses and cause dose-dependent uterine relaxation.
- Effects minor at low doses
- High doses can result in uterine acne and increased blood loss at delivery
N2O has minimal if any effects
What effects do opioids have on the progression of labor? Do they have any effects on the fetus?
Minimally decreased the progression of labor
Opiates readily cross the placenta, but effects on neonates at delivery very considerably.
(Can cause respiratory depression)
Why is Oxytocin (Pitocin) used?
Used to induce or augment uterine contractions or to maintain uterine tone postpartum
NB: Administer slowly to prevent transient systemic hypotension and reflex tachycardia
Why is Methergine used?
Methergine causes intense and prolonged uterine contractions. Given only after delivery to treat uterine atony.
-Usually administered IM because it can cause severe hypertension
Why is Hemabate used?
Stimulates uterine contractions. Used to treat refractory postpartum hemorrhage.
Given IM with side effects of N/V & diarrhea
Why is magnesium used?
Stops premature labor
Prevent eclamptic seizures
Therapeutic serum level = 6-8 mg/dL
(Hypotension, heart block, sedation)
What is PIH and how is it defined?
Pregnancy induced hypertension (preeclampsia)
-Systolic >140 mmHg & Diastolic >90 mmHg
(OR as a consistent increase pressure 20% above the patient’s baseline)
- Proteinuria (>300mg/day)
- Edema
What is eclampsia?
Preeclampsia with seizures (basically)
“Occurrence of generalized tonic-clonic seizures in a pregnant patient with proteinuric hypertension”
What is HELLP syndrome?
Hemolysis
Elevated Liver enzymes
Low Platelets
What is thought to be the cause of preeclampsia and what is the definitive treatment for it?
Cause: abnormal placentation outs out vasoactive substances
Only Definitive Cure: Deliver fetus and placenta
What differential diagnosis must be ruled out in the case of eclampsia?
Amniotic Fluid embolism
True or False: Complications of PIH are limited only to the cardiovascular system
FALSE
Complications of PIH include cardiovascular, pulmonary, neurological, hepatic, renal, and hematological
Acute fatty liver of pregnancy is seen during which trimester?
What are the symptoms and mortality rate?
Rare
3rd Trimester
High Mortality rate
Symptoms: Jaundice, N/V, epigastric pain, increased liver enzymes, decreased serum glucose
What is an amniotic fluid embolism?
Sometimes called “anaphylactoid syndrome of pregnancy”
Presents when mother’s circulation is exposed to amniotic fluid.
How does amniotic fluid embolism present and what is the mortality rate?
Patients typically present with sudden tachypnea, cyanosis, shock, and generalized bleeding –> respiratory distress & CV collapse
-acute PE, DIC, & uterine atony = majot pathophysiological manifestations responsible
86% Mortality (>50% in 1st hour)
-usually diagnosed post-mortem
What is DIC?
Disseminated intravascular coagulation
-Characterized by widespread systemic activation of coagulation, resulting in intravascular formation of fibrin and ultimately thrombotic formation occlusion of small and midsized vessels
Why are pregnant women at increased risk for thromboembolic disease?
What else can increase this risk?
- increase in most clotting factors
- Gravid uterus causes venous stasis
Other risks:
-smoking, obesity, old age, genetics
Pregnant patients with pre-existing renal disease are at an increased risk for what pregnancy induced disease state?
Preeclampsia
What are some of the major concerns for inducing general anesthesia in a pregnant patient?
SECURING AIRWAY
- desat faster
- increased aspiration risk
- VC harder to visualize due to altered anatomy
Extrauterine life is not possible until what point of Gestation?
After 24-25 weeks (formation of pulmonary capillaries)
