Obstetrics (part 1) Flashcards
EBL in a pregnant woman
90cc/kg
Twin gestation EBV
105cc/kg
Blood volume is _____ in pregnancy.
Blood volume increased in pregnancy….calculations used for C/S, esp. will affect ongoing blood loss
Blood loss for different delivery types
Average blood loss vaginal delivery is 400-500cc
Average blood loss C/S 800-1000cc
Average blood loss twins by C/S-1000cc
Blood volume gradually returns to normal by _____ post partum
6-9 weeks
Why do pregnant women have physiologic anemia?
Intravascular fluid volume: increased 35%
….relative anemia of pregnancy due to increase of 55% in plasma volume and the erythrocyte volume increases 30%
Most common cause of PPH is ____.
uterine atony
PPH occurs in 1-5% of all deliveries
Late in pregnancy uterine artery blood flow is _____.
500-700cc/min and approx 15% of cardiac output
New/updated definition of PPH
Cumulative blood loss greater than or =1000cc
OR
Bleeding associated with signs/symptoms of hypovolemia within 24hrs of birth process
Uterine atony (first line med and second line med)
FIRST LINE = Oxytocin(30 units in 500cc LR)-lowdose/infusion
SECOND LINE = Methylergonovine .2mg IM –Ergot Alkaloid
contraindicated with hypertension or preeclampsia
Hemabate = ____. Used for?
(prostaglandin F2-alpha) 250mcg IM or endometrially for uterine atony
Misoprostol(Cytotec) = ___. used for?
prostaglandin PGE1analogue—off label rectally
used for uterine atony
could also be used sublingually
Oxytocin Hormone use
Used to induce or augment labor process
FIRST LINE drug for Uterine Tone and minimizing blood loss after delivery
FDA alerts for oxytocin
FDA high alert black box during labor for “medical indications”
SE: hypotension, tachy, flushing, emesis,
myocardial ischemia
High alert medication (InstSafeMedPractice)
Oxytocin Rule of 3s
Low dose RULE OF 3s for CESAREAN SECTION by Lawrence Tsen
3 units IV loading dose over 30 seconds/ assess at 3 minute intervals….. Give 3 IU units rescue dose…. Then 3 total doses of oxytocin initial plus 2 rescue
30IU/L at 100cc/hr
Initial 3 units is for effective Uterine contractions for laboring and nonlaboring women….
Study of Elective c/s delivery cases
(rule of 3s vs continuous “wide open” infusion)
TXA for PPH
Tranexamic acid –give within 3 hours
Lysine analogue
Prevents fibrinolysis
Competitively blocks plasminogen and plasmin
TXA dosing for PPH
TXA half life is 2-3 hours with normal renal fxn
1 gram in 100cc over 10min
1 gram in 250cc over 8hr infusion
Fibrinogen importance in pregnancy
Low is MOST predictive variable for EARLY Hemorrhage
Goal is greater than 200mg/dl
GIVE EARLY!!!!
What are the determinants of placental transfer?
Principally by DIFFUSION from maternal to fetal circulation
Concentration gradients
Maternal protein binding
Molecular weight
Lipid solubility
Degree of ionization
What are the qualities of a drug that passes RAPIDLY to the placenta?
Low protein binding
<500 molec weight
High lipid solubility
Minimal ionization
What are the qualities of a drug that passes SLOWLY to the placenta?
High protein binding
>1000 molec weight
Low lipid solubility
Maximal ionization
Benzodiazepines and the placenta
Benzodiazepines readily cross placenta/ May affect beat to beat variability
Opioids and the placenta
Opioids rapidly cross-Narcan available for neonatal respiratory depression
Ketamine and the placenta
Ketamine readily crosses, but in low doses does not cause neonatal depression
Which drugs do NOT cross the placenta?
All Neuromuscular blocking agents
Glycopyrrolate
Insulin
Heparin
Weight gain with pregnancy
Uterus 1kg
Fetus and placenta 4kg
Blood volume/fluid 4kg
Additional Fat 3kg
(Normal weight pt with BMI 18.5-24.9) is recommended total weight gain of 25-35lb
Overweight definition
Overweight
BMI 25-29.9 kg/m2
6.8-11.3 kg
(15-25 pounds)
___ pregnant women are obese – and BMI rates
Half of pregnant women are overweight or obese
C/S rates:
BMI 29 or less= 20%
BMI 35-39= 47%
Obesity and risks
Obesity-INCREASED RISK OF COMPLICATIONS
Gest DM
HTN/PEC
Fetal Macrosomia
Premature labor
Stillborn/anomalies
Infection w C/S- 2 abx
Off spring of obese mothers are at increased risk of childhood and adult obesity
Obesity related insulin resistance and inflammatory pathways linked to development of PEC
Obesity labor times
Labor duration nulliparas increased .3 hours for each 10kg increment in maternal weight
Failed induction rate twice as likely
C/Section rate BMI greater than 60kg/m2— 69%
Obese women and C/S -ABX and closure of subQ layer (reduce wound disruption)
Obesity & maternal morbidity and mortality
Normal BMI 143/10,000 women; Class 3 obesity (BMI 40 or higher…) 203/10,000 women
Hemorrhage require transfusion, serious cardiac respiratory hematologic, thrombus, embolism, sepsis shock, hepatic renal failure, uterine rupture
Cardiac changes with pregnancy - HR and SVR
Heart rate only increased 15%
LVH
SVR decreased 20% at term
Cardiac Output
Cardiac output increased 40% above non pregnant levels mostly due to 30% increase in stroke volume
Greatest increase in CO?
Immediately after delivery of placenta
Cardiac output increases 60%-80% above pre-labor values
CO returns to non pregnant value 2 weeks postpartum
CO increased mostly due to INCREASE in stroke volume… uterine contraction 300-500cc
Peripheral Circulation - SVR
Normally no change in Systolic BP
SVR is decreased by 20%
Supine Hypotensive Syndrome
Watch for supine hypotension syndrome in about 10% of patients at term…ie decreased venous return due to compression of the IVC by gravid uterus
Use left uterine displacement(LUD)!!!!
Ideal vasopressor??
ASA practice guidelines for OB anesthesia….both ephedrine and phenylephrine are acceptable agents for treating hypotension during neuraxial anesthesia.
Respiratory Changes - MV
Minute ventilation increased 50% d/t progesterone (also relaxes bronchial smooth muscle)
Respiratory Changes - TV
TV increased 40%
Respiratory Changes - RR
Resp rate increased 10%
Respiratory Changes - ERV
ERV decreased 20%
Respiratory Changes - RV
Residual volume decreased 20%
Respiratory Changes - FRC
FRC decreased 20%
Respiratory Changes - Thoracic cage
Thoracic cage increased diameter
Further Resp - TLC
Minimal/No change in VC or TLC
Further Resp - MAC requirement
Changes in anesthetic depth with GA is faster in pregnancy (decreased MAC)
Further Resp - O2 consumption
Increased oxygen consumption by 20%
Oxyhemoglobin Dissociation Curve
Left shift of oxyhemoglobin dissociation curve (fetal hemoglobin)
Respiratory alkalosis….Increased affinity for fetal hemoglobin/holds onto oxygen shift left for fetal hemoglobin diss curve….
Right shift of oxyhemoglobin dissociation curve (maternal term hemoglobin)
Maternal P50 increases from 26 to 30mmhg at term(maternal O2 diss curve shifts to RIGHT to offload Oxygen to fetus….)