OB Flashcards
Describe the parturients blood gas levels:
pH - no change
PaO2 - increase - 104-108
PaCO2 - decrease - 28-32
Bicarb - decrease - 20
Describe O2 consumption in the parturient in the different stages of labor:
Term - increase 20%
First stage of labor - increase 40% over prelabor
Second stage of labor - increase 75% over prelabor
Describe CO of the parturient:
Increase 40% (10% goes to uterus)
HR increases 15%
SV increases 30%
Discuss CO during labor (as compared to pre-labor values)
1st stage: increases 20%
2nd stage: increases 50%
3rd stage: increases 80%
When does CO return to pre-labor values after birth?
24-48 hours
When does CO return to pre-pregnancy values?
About 2 weeks
How do twins affect CO?
Increase CO 20% above a single fetus pregnancy
Do MAP, SBP, or DBP change in the parturient?
MAP = no change (increased blood volume + decreased SVR = net even)
SBP = no change
DBP = decreased 15%
To which parturient should you apply left displacement of the uterus?
Anyone in the second or third trimester
How does intravascular fluid volume change in the parturient?
Increases 35% to prepare for hemorrhage in labor; creates dilution anemia
How do plasma volume and erythrocyte volume change in the parturient?
Plasma - increases 45%
Erythrocyte - increases 20%
What clotting factors increase in mom?
1, 7, 8, 9, 10, 12
What clotting factors decrease in mom?
11 and 13
What changes occur in antithrombin, protein s, and protein c?
antithrombin and protein s decrease. no change in protein c.
What changes occur in moms fibrinolytic system?
increased fibrin breakdown
Describe the parturients hematologic change overall?
Mom makes more clot, but she breaks it down faster.
How do PT and PTT change?
Decrease by 20%
Normal PT at term - 9.6-12.9s
Normal PTT at term - 24.7-35.0s
What occurs with platelet count?
Unchanged or decrease up to 10% due to hemodilution and consumption
How does MAC change in the parturient?
Decreases 30-40%
Does gastric volume increase or decrease in the parturient? Why?
Increases due to increased gastrin
How does gastric pH change in the parturient? Why?
Decreased due to increased gastrin
How does LES tone change in the parturient? Why?
Decreases due to increased progesterone and estrogen. Cephalad displacement also contributes.
Describe gastric emptying changes in the parturient:
No change before onset of labor; decreases after labor begins
What renal functions increase in the parturient and why?
GFR - increased blood volume and CO
Creatinine clearance - increase blood volume and CO
Glucose in urine - increased GFR and decreased renal absorption
What renal functions decrease in the parturient and why?
Creatinine and BUN - increased creatinine clearance
How many mL/min of blood flow does the uterus receive?
700-900 mL/min, which accounts for 10% of CO
How does serum albumin change in the parturient? How does this affect the free fraction of highly protein bound drugs?
Albumin is decreased, so the free fraction is increased.
Is pseudocholinesterase increased or decreased in the parturient?
Decreased (no meaningful effect on sux metabolism)
What is uterine blood flow dependent on?
Does NOT auto regulate, so dependent on MAP, CO, and uterine vascular resistance (low resistance system)
What reduces uterine blood flow?
Decreased perfusion. Ex: maternal hypotension (sympathectomy, hemorrhage, aortocaval compression)
Increased resistance. Ex: uterine contraction, hypertensive conditions that increase uterine vascular resistance
What drug characteristics favor placental transfer?
Low molecular weight <500 Daltons
High lipid solubility
Non-ionized
Non-polar
What drugs do not cross the placenta?
Heparin
Insulin
NMBs
Glycopyrrolate
Describe Stage 1 of labor:
Beginning of regular contractions to full cervical dilation (10cm)
Describe Stage 2 of labor:
Full cervical dilation to delivery of the fetus
Describe Stage 3 of labor:
Delivery of the placenta
When do the latent and active phases of labor occur?
Stage 1:
Latent ends when the cervix dilates to 2-3 cm
Active begins 3-10 cm
Why is lidocaine not popular for labor analgesia?
Produces strong motor block (good for C-section)
What local anesthetic reduces the efficacy of epidural morphine and why?
2-chloroprocaine. It antagonizes opioid receptors (mu and kappa)
What is the dosing of epidural opioids?
Fentanyl bolus - 50-100 mcg
Fentanyl infusion - 1.5-3 mcg/mL
Sufentanil bolus - 5-10 mcg
Sufentanil infusion - 0.2-0.4 mcg/mL
Discuss opioid spinal dosing:
Fentanyl: 15-25 mcg
Sufentanil: 1.5-5 mcg
Morphine: 125-250 mcg
Meperidine: 10-20 mg
Discuss spinal adjunct medications and doses:
Epinephrine: 2.25-200 mcg
Clonidine: 15-30 mcg
Discuss epidural bolus dosing of adjuncts:
Epinephrine: 25-75 mcg
Clonidine: 75-100 mcg
Neostigmine: 500-750 mcg
Discuss epidural continuous infusion dosing of adjuncts:
Epinephrine: 25-50 mcg/hr
Clonidine: 10-30 mcg/hr
Neostigmine: 25-75 mcg/hr
What are 3 ways a patient can develop a total spinal?
- An epidural dose injected in the subarachnoid space
- An epidural dose injected in the subdural space
- A single shot spinal after a failed epidural
How does a total spinal present?
Rapid progression of sensory and motor block
Dyspnea, difficulty phonating, and hypotension
Loss of consciousness
What does a fetal heart rate of 110-160 indicate?
Normal acid-base balance and intact CNS and ANS of the fetus
What does a fetal heart rate of <110 indicate?
Bradycardia.
Fetal causes: asphyxia or acidosis
Maternal causes: hypoxemia or drugs that decrease uteroplacental perfusion
What does a fetal heart rate >160 indicate?
Tachycardia.
Fetal causes: hypoxemia, arrhythmias
Maternal causes: fever, choriamnionitis, atropine, ephedrine, terbutaline
At what magnesium level does loss of deep tendon reflexes occur?
7-12 mg/dL
At what level of magnesium do seizures occur?
<1.2 mg/dL
Respiratory depression occurs at what magnesium level?
> 12 mg/dL
What medications can be used for tocolysis to suppress labor?
Beta 2 agonists, magnesium, calcium channel blockers, nitric oxide donors (not common d/t hypotension)
Discuss oxytocin
First line utertonic
SE: water retention (similar structure to vasopressin), hyponatremia, hypotension, reflex tachycardia, coronary vasoconstriction
Give IV or directly into uterus (rapid IV admin can cause CV collapse)
hepatic metabolism
half-life: 4-17 min
Discuss methergine
second line uterotonic
Ergot Alkaloid
Dose 0.2 mg IM (IV admin can cause significant vasoconstriction, hypertension, and cerebral hemorrhage)
hepatic metabolism
half-life = 2 hours
Discuss prostaglandin F2
third-line uterotonic
Hemabate or Carboprost
dose: 250 mcg IM or injected into uterus
SE: N/V, diarrhea, hypotension, hypertension, bronchospasm
What medications should you give for aspiration prophylaxis to a pregnant mother?
Sodium citrate - neutralize gastric acid
H2 receptor antagonist (ranitidine) - reduce gastric acid secretion
Gastrokinetic agent (metoclopramide) - hasten gastric emptying and increase LES tone
Ideally, how long should surgery be delayed postpartum?
2-6 weeks
If surgery cannot be delayed in a pregnant patient, what is the best trimester to undergo anesthesia?
2nd trimester
avoids higher risk of teratogenicity in the 1st trimester (13-60 days is organogenesis)
avoids increased risk of preterm delivery that’s highest in the 3rd trimester
What non-OB procedures lead to the highest incidence of preterm labor?
intra-abdominal and pelvic surgery
What inhalation agent should be avoided in the pregnant patient and why?
Nitrous oxide showed congenital disabilities in animals who received it for 1-2 days due to inhibition of DNA synthesis (lack data in humans); many avoid nitrous in the first 2 trimesters
When is a pregnant patient considered a full stomach?
18-20 weeks gestation
Treat like full term (RSI, aspiration prophylaxis, etc.)
Treat like full term also applies to immediate postpartum period
Why should you avoid hyperventilation in the pregnant mother?
Normal PaCO2 ~30 mmHg -> hyperventilation reduces placental blood flow -> risk of fetal asphyxia
What medication class should a pregnant mother avoid after the first trimester and why?
NSAIDs due to potential to close the ductus arteriosus.
When is chronic htn in the parturient diagnosed? When does it return to normal?
Before 20 weeks gestation. It does not return to normal after delivery.
When does gestational htn occur in the parturient and how is it diagnosed?
After 20 weeks gestation. It’s only diagnosed post-delivery when BP returns to normal (rules out chronic htn).
When is preeclampsia diagnosed in the parturient and what are the diagnostic criteria?
htn >140/90 (mild) or >160/110 (severe) develops after 20 weeks gestation. Proteinuria is typically present.
Can preeclampsia exist without proteinuria? If so, what would be present instead?
Yes. Instead could have:
persistent RUQ or epigastric pain
persistent CNS or visual symptoms
fetal growth restriciton
thrombocytopenia
elevated serum liver enzymes
At what BP is severe eclampsia diagnosed? When does it progress to eclampsia?
BP > 160/110. Progresses to eclampsia when mom develops seizures.
Maternal physiologic effects of preeclampsia
What is thought to be the cause of preeclampsia?
Abnormal placental implantation leads to elevated vascular resistance and decreased placental blood flow. The placenta and fetus don’t receive an adequate amount of O2 or metabolic substrate to normally develop.
What placental production changes occur with preeclampsia?
Produces 7xs more thromboxane than prostaglandin, which favors vasoconstriction, platelet aggregation, and reduced placental blood flow. Also releases cytokines that lead to endothelial dysfunction through the body.
Mild Preeclampsia vs Severe Preeclampsia: BP
<160/<110 vs >160/>110 due to increased thromboxane vasoconstriction
Mild Preeclampsia vs Severe Preeclampsia: proteinuria
< 5 g/24H, < 3+ dipstick
>= 5 g/24H, >= 3+ dipstick
Due to destruction of glomerular capillary endothelium
Mild Preeclampsia vs Severe Preeclampsia: 24H urine total
> 500 mL
<= 500 mL
Due to destruction of glomerular capillary endothelium and renal edema
Mild Preeclampsia vs Severe Preeclampsia: edema
generalized edema in both
pulmonary edema only in severe (due to HF)
due to decreased oncotic pressure & increased vascular permeability
Mild Preeclampsia vs Severe Preeclampsia: cyanosis
no - mild
yes - severe
Mild Preeclampsia vs Severe Preeclampsia: headache
no - mild
yes - severe
due to cerebral edema
Mild Preeclampsia vs Severe Preeclampsia: visual impairment
no - mild
yes - severe
due to vasoconstriction of ocular arterioles
Mild Preeclampsia vs Severe Preeclampsia: epigastric pain
no - mild
yes - severe
due to liver subcapsular hemorrhage and hypoxic liver
Mild Preeclampsia vs Severe Preeclampsia: HELLP syndrome
no - mild
yes - severe
Mild Preeclampsia vs Severe Preeclampsia: platelet count
> 100,000/mm3
< 100,000/mm3
due to consumption by endothelial damage
Mild Preeclampsia vs Severe Preeclampsia: fetal growth
normal
impaired
due to uteroplacental hypo perfusion
What is the definitive treatment for preeclampsia/eclampsia?
delivery of the fetus and placenta
When can mother with preeclampsia be medically managed?
Mild symptoms + young fetus -> bed rest and observation
When is immediate delivery required in the preeclamptic patient?
Symptoms become severe or fetal distress ensues
When and why should you employ antihypertensive medications in mom?
Treat BP >160/110 to prevent cerebrovascular accident, myocardial ischemia, or placental abruption.
What antihypertensives can be given for maternal acute htn?
labetalol 20 mg IV followed by 40-80 mg q 10 min, max 220 mg
hydralazine 5 mg IV q 20 min, max 20 mg
nifedipine 10 mg PO q 20 min, max 50 mg
nicardipine infusion at 5 mg/hr, titrated 2.5 mg/hr q 5 min, max 15 mg/hr
How long do risks of complications related to severe preeclampsia continue?
Up to 4 weeks postpartum.
Stroke and pulmonary HTN risk highest postpartum period.
Discuss seizure prophylaxis in eclampsia:
Mag sulfate loading dose of 4 g over 10 min
infusion 1-2 g/hr
Mag tox treatment: 10 mL 10% CaGluconate IV
HELLP Syndrome
Hemolysis
Elevated Liver enzymes
Low Platelet count
Develops in 5-10% of those with preeclampsia
SS: epigastric pain and upper abdominal tenderness
higher risk for DIC and abnormal bleeding from the liver
What is the definitive treatment for HELLP syndrome?
Delivery
However, could present for first time in postpartum period
MAC values for maternal acute vs chronic cocaine use:
acute intox: MAC increased
chronic use: MAC decreased
OB risks of maternal cocaine use:
spontaneous abortion
premature labor
placental abruption
low APGAR
CV risks in maternal cocaine use:
tachycardia
dysrhythmias
coronary vasoconstriction
myocardial ischemia
CNS risks in maternal cocaine use:
cerebral vasoconstriction
ischemia
seizures
stroke
What antihypertensive do you caution use of in maternal cocaine use?
Caution beta block -> HF if SVR elevated significantly due to myocardial depression from B1 block or further increased SVR from B2 block
What antihypertensives can be used in maternal cocaine use?
Labetalol - reasonable due to blockage of alpha-mediated peripheral vasoconstriction
Vasodilators - but could cause hypotension
How do you treat hypotension in maternal cocaine use?
Phenylephrine
Ephedrine may not elicit response in chronic use due to catecholamine depletion
What lab should you check before neuraxial placement in maternal cocaine use?
Platelet count. Chronic cocaine abuse can cause thrombocytopenia.
What is the preferred anesthetic for abnormal placental implantation?
General. Big risk for tremendous blood loss due to impairment of uterine contractility.
However, neuraxial is safe.
What two conditions is abnormal placental implantation closely associated with?
Placenta previa
Previous c-sections
Discuss placenta previa and risk factors:
placenta partially covers cervical os when attaches to lower uterine segment
PAINLESS VAGINAL BLEEDING
often requires c-section
risk factors: previous c-sections, history of multiple births
Placental abruption risk factors include:
All increase driving pressure to placenta..
PIH
preeclampsia
chronic HTN
cocaine use
smoking
excessive alcohol use
Discuss placental abruption:
maternal pain + vaginal hemorrhage and fetal hypoxia
risk of amniotic fluid embolism that leads to DIC
obtain large-bore IV and have blood products ready
prep for c-section; vaginal delivery possible if fetus is stable
What is the most common cause of postpartum hemorrhage? What risk factors lead to this?
Uterine atony
multiparty
multiple gestations
polyhydramnios
prolonged oxytocin infusion before surgery
What are treatments for obstetric bleeding?
uterine massage
oxytocin
ergot alkoloids
manual massage
intrauterine balloon if these don’t work
What conditions often lead to DIC in the parturient?
DIC
placental abruption
intrauterine fetal demise
often accompanied by circulatory shock
Discuss APGAR scores:
Normal: 8-10
Moderate distress: 4-7
Impending demise: 0-3
What categories are included in the APGAR system?
Heart rate
Respiratory effort
Muscle tone
Reflex irritability
Color
APGAR Score: heart rate
0: absent
1: < 100 bpm
2: > 105 bpm
APGAR Score: respiratory effort
0: absent
1: slow, irregular
2: normal, crying
APGAR Score: muscle tone
0: limp
1: some flexion of extremities
2: active motion
APGAR Score: reflex irritability
0: absent
1: grimace
2: cough, sneeze, or cry
APGAR Score: color
0: pale, blue
1: body pink, extremities blue
2: completely pink
How soon after delivery should neonatal SpO2 increase?
Should increase from 60% to 90% within 10 minutes.
Should O2 be used to assist ventilation in the newborn? Why or why not?
No, it increases the risk of an inflammatory response. Room air should be used instead.
What is the best indication of adequate ventilation in resuscitation of a neonate?
The resolution of bradycardia. If ventilation doesn’t improve cardiovascular performance, emergency drugs should be given.
What three routes can emergency medications be given to a neonate?
Umbilical vein, ETT, or IO
Discuss emergency meds for neonatal resuscitation:
Epi: 1:10,000, dose 10-30 mcg/kg IV or 0.05-0.1 mcg/kg intratracheal
Volume expansion:
PRBCs 10 ml/kg over 5-10 minutes
NS
LR
Discuss emergency meds for neonatal resuscitation:
Epi: 1:10,000, dose 10-30 mcg/kg IV or 0.05-0.1 mcg/kg intratracheal
Volume expansion:
PRBCs 10 ml/kg over 5-10 minutes
NS
LR
Neonatal resuscitation algorithm
What physiologic increases does progesterone cause?
Minute ventilation (decreased PaCO2 and increased HCO3 excretion)
RAAS activity (increased blood volume -> increased CO)
Vascular muscle relaxation (decreased SVR and decreased PVR)
Sensitivity to local anesthetics
What physiologic decreased does progesterone cause?
Airway resistance (increased bronchodilation)
MAC
Lower esophageal sphincter tone
