Obstetrics Flashcards
Preeclampsia risk factors (6)
Hydatidiform mole, multiple gestational, obesity, polyhydramnios, diabetes, primigravidas
Define mild preeclampsia
Systolic > 140, diastolic > 90, proteinuria >2 gm/day, edema
What vasopressor should be used with mag toxicity and why?
Ephedrine, magnesium antagonizes the effects of alpha agonists
What happens to cardiac output at term, during labor, and immediately after delivery?
40% increase at term, 45% during labor, 60-80% increase following delivery
How much does plasma volume increase? Red cell volume?
40% plasma, 20% red cell volume
During pregnancy, what H&H signifies true anemia?
</= 33/11
What 3 changes happen to the GI system during pregnancy?
Acidity and gastric volume increase, gastric motility decrease (2/2 progesterone), GE sphincter tone decreases
When does aortocaval compression occur?
20 weeks
What happens in supine position after 20 weeks and why?
Aortocaval compression 2/2 a 50% increase in femoral venous pressure that causes a 10-15% decrease in SV and CO
During pregnancy, when is the H&H lowest and why?
30-34 weeks 2/2 plateau in volume expansion
What changes happen to RBF, GFR, and BUN/Cr? When?
They increase by 50% leading to a decrease in BUN and creatinine; 16 weeks
What happens to total protein and albumin/globulin ratio during pregnancy and its importance
Decreased; lower albumin may result in higher free blood levels of substances
Why happens to pseudocholinesterase levels during pregnancy? Does this affect your anesthetic?
Decreased, response to moderate doses of succinylcholine is not prolonged
What happens to SV, HR, and SVR during pregnancy?
SV increases by 25%, HR increases less, SVR decreases by 20%
What CNS changes occur during pregnancy?
40% decrease in MAC, 30-50% decrease in local requirements
What 3 changes occur to the airway during pregnancy?
Capillary swelling leads to mucosal enlargement, tissues become more friable, breast enlargement can cause head positioning difficulty
What happens to minute ventilation during pregnancy and why?
Increases by 50%; progesterone increased tidal volume with little change in RR
What acid/base changes occur during pregnancy?
PaCO2 is ~32 but pH is unchanged because of compensatory metabolic acidosis (HCO3 25 –> 21)
How does inhalational induction change during pregnancy and why?
Increased ratio of minute ventilation to FRC causes rapid induction and emergence
What happens to FRC during pregnancy?
Decreases 20% due to decrease in residual volume; closing capacity exceeds FRC in ~50% of supine women late in pregnancy
What happens to vital capacity during pregnancy?
Unchanged as inspiratory capacity increases and expiratory reserve volume decreases
What happens to PaO2 during pregnancy?
Increases by 10
What happens to airway resistance during pregnancy?
Decreases 2/2 progesterone
What happens to tidal volume during pregnancy?
Increase by 45%
What happens to oxygen consumption and CO2 production during pregnancy?
Consumption increase 30-40%, CO2 production increase 30-40%
What coagulation factors increase during pregnancy?
Factors I (fibrinogen), II, VII, VIII, IX, X
What is the range for leukocytosis after 12 weeks?
10500-16000
Which coagulation factors decrease during pregnancy?
Factors XI, XIII
What is the non-pregnant UBF?
50-200 ml/min
What is pregnant UBF?
10% of CO, 600-700 ml/min
How much must UBF decrease to see fetal distress?
50%
Name drugs that do not cross the placenta (5)
heparin, insulin, glycopyrrolate, non-depolarizing relaxants, succinylcholine
What is the 1st stage of labor?
start of contractions to complete cervical dilation
What nerves are involved in 1st stage of labor and what do they innervate?
T10-L1 visceral pain of contractions and cervical dilation –> uterus, cervix, upper vagina
What is the 2nd stage of labor
complete cervical dilation up until delivery
What nerves are involved in the 2nd stage of labor and what do they innervate?
S2-S4 (pudendal) somatic pain of distention of birth canal, vulva, and perineum–> perineal area
What are the complications associated with paracervical block, what is the incidence, and when can it be used?
10-40% of fetal bradycardia and acidosis because high fetal blood levels cause cardiotoxicity; can be used in 1st stage of labor
What are aortocaval compression symptoms?
n/v, tachycardia, hypotension, sweating; may not have symptoms if uterine artery hypoperfusion and hypotension is present without compromise of maternal CO
What is frank/complete/incomplete breech?
buttocks presenting, buttocks and feet presenting, one or both feet presenting
Breech presentation increases maternal risk of…
maternal mortality 2/2 hemorrhage, infection, and retained placenta
Breech presentation increases risks to fetus…
asphyxia due to cord compression and intracranial hemorrhage due to trauma
Define severe preeclampsia
> /= 160/110, >5 gm proteinurea/day, edema (can include pulmonary edema leading to CHF)
What are the characteristics of eclampsia?
Hypovolemia, thrombocytopenia, DIC, CNS changes
What CNS changes can be seen with eclampsia?
Convulsions, coma, hypoxic cerebral encephalopathy
When does preeclampsia present and end?
24 weeks and ends within 48 hours of delivery
What is the treatment for preeclampsia?
3-5 gm loading dose of magnesium given over 15 min and 1gm/hr maintenance
What is the magnesium goal for preeclampsia treatment?
4-6 mEq/L
What are magnesium side effects?
Skeletal muscle relaxation, anticonvulsant, sedation, tocolytic, vasodilator
What does magnesium cause skeletal muscle relaxation?
It decreases the release of acetylcholine and decreases the sensitivity of the motor end plate to acetylcholine
What are the magnesium side effects for the infant?
Flaccidity, respiratory depression, apnea
How does magnesium treatment change your anesthetic
Increased sensitivity to depolarizing and non-depolarizing relaxants; decrease succinylcholine does by 50%
How is preeclampsia treated?
Bed rest, magnesium, hydralazine
Benefits of hydralazine vs SNP for treatment of preeclampsia
Hydralazine increases uterine and renal blood flow, starts to work in 15-20 min, lasts for 2 hours; SNP decreases uterine blood flow and increases risk of fetal CN toxicity (crosses placenta)
What is placenta previa and what is the incidence?
When the placenta is located over or very near the internal cervical os; 0.1%-1.0% incidence that increases with age
What is abruptio placenta and what is the presentation?
Separation of placenta from uterine wall after 20 weeks; presents as hypotension and fetal distress
What are the symptoms of uterine rupture?
Severe abdominal pain, hypotension, loss of fetal heart tones
Risk factors for uterine atony (4)
Retained placenta, multiparity, large infants, polyhydramnios
What is the treatment for uterine atony?
Uterine massage, oxytocin, prostaglandin F2-alpha, ergots, misoprostol, hysterectomy with ligation of internal iliac artery
What is placenta acreta?
Abnormal adherence of placenta to myometrium
What are the risks to fetus with benzodiazepines and nitrous?
Cleft palate; inhibits methionine synthetase impairing DNA synthesis
What is ritodrine/terbutaline? Uses? Side effects?
Beta agonists used for tocolysis; increased HR and CO (b1) & hyperglycemia and hypotension (b2) also causes pulmonary edema, hypokalemia, arrhyhmias
Why is ethanol used during pregnancy? What is its use associated with?
It’s a tocolytic that works by inhibiting oxytocin; increases the risk of gastric aspiration; administered in D5W
What side effect is ritodrine and magnesium use associated with?
Chest pain
What is prostaglandin synthetase used for? Side effects?
Used for tocolysis; can cause premature closure of PDA, primary pulmonary HTN, and inhibits cyclooxygenase which may lead to bleeding problems
What is normal FHR variability and what does it indicate?
Normal variability is 7-14 beats/min; it is best indication of fetal well being –> absence happens with prematurity,sleeping baby, CNS damage, hypoxia, drug effects
Early deceleration
FHR slowing begins at onset of contraction and ends at the conclusion, caused by fetal head compression leading to bagel stimulation, benign
Late deceleration
FHR dip starts after onset if contraction an persists after he conclusion, indicate uteroplacental insufficiency
Variable deceleration
FHR dips not associated with contractions, due to umbilical cord compression, if last more than 1 minute indicative of severe fetal acidosis with imminent in utero death
What is scalp pH normal range?
7.20-7.25
When and how is L/S ratio helpful?
L/S ratio is = until 35 weeks, if L/S ratio is >/= 2 respiratory distress syndrome is unlikely
APGAR
A - appearance, P - pulse, G - grimace, A - activity, R - respirations
Most common nerve injury during pregnancy and symptoms
Common peroneal nerve compressed between head of fibula and stirrups; foot drop, loss of extension of toes, loss of eversion
Mechanism of sciatic nerve injury during labor and symptoms
External rotation of legs (distance between sciatic notch and fibula is increased); decreased strength in muscles below the knee and decreased sensation of lateral 1/2 of leg and all foot except arch
Mechanism of femoral nerve injury during labor and symptoms
Excessive angulation of thigh; unable to flex the hip or extend the knee, decreased sensation to superior aspect of thigh and antero-medial aspect of leg
What drugs increase/decrease FHR variability?
Increase - ephedrine; decrease with fetal CNS depressants (benzos, barbs, opioids, anesthetics) and block parasympathetic (atropine)
Define “ion trapping”
If the fetus becomes acidotic local anesthetic (weak bases) gets trapped in the ionized form on the fetal side
With a maternal PaO2 of 600 mm Hg what will the fetal PaO2 be?
No more than 50 mm Hg
How much will an FiO2 of 21% –> 100% change the venous O2? Arterial O2?
Umbilical venous 28 –> 47, umbilical arterial 15 –> 25
Pathophysiology of preeclampsia
Thromboxane over production causes vasoconstriction, platelet aggregation, increased uterine activity and impaired uteroplacental blood flow; uterine ischemia causes release of renin which promotes angiotensinogen to angiotensin I
Drugs increasing uterine tone (5)
PGF2 alpha, ergots, oxytocin, ketamine, amide local anesthetics
Drugs that decrease uterine tone (5)
Beta 2 agonists, ethanol, magnesium, methylxanthines, potent anesthetics
Incidence of PDPH
40-50% in the first week PP
Modalities for diagnosing central venous thrombosis
MRV/CTV
PDPH risk factors
Young, female, pregnant, non-smoker, dural thickness
PDPH conservative treatment
Caffeine (increase CSF production and vasoconstricts), theophylline, hydrocortisone, gabapentin
Full stomach
12 weeks
