Obstetrics/OBGYN Flashcards
Cardiovascular Changes w/ Pregnancy
↑HR 20-30% peaks at 32 weeks ↑CO 40% returns to baseline w/in 14 days Ventricular walls thicken ↑EDV Dilutional anemia ↑↑plasma volume ↑RBCs ↓SVR → venous pooling & ↓diastolic BP to compensate BP w/ hypervolemia & ↑blood volume
Aortocaval Compression
Supine position → HoTN d/t aorta & vena cava compression from gravid uterus
Treatment = L uterine displacement
Hematological Changes w/ Pregnancy
Hypercoagulable ↑clotting factors VII-IX & fibrinogen
↑risk thromboembolic events (leading cause maternal mortality)
↓platelet count minimal
↑WBC count
Dilutional anemia
Airway Changes w/ Pregnancy
Airway swelling during labor
Capillary engorgement → narrowed glottic opening (use smaller ETT 6.0 or 6.5 cuffed), oral & nasal pharynx edema (avoid nasal intubation), & laryngeal edema
Consider short laryngoscope handle
Respiratory Changes w/ Pregnancy
↑oxygen consumption
↑minute ventilation ↑↑VT ↑RR (tachypnea not normal)
↓PaCO2 minimal w/ compensatory ↓HCO3¯
Diaphragm shifts upward ↓FRC
Rapid desaturation in apneic patient (ensure adequate pre-oxygenation)
Neurological Changes w/ Pregnancy
↑sensitivity to anesthetic gases & LAs
↑block height d/t engorged epidural veins that compress the dura & exaggerate the LA spread
↑intra-abdominal pressure ↓epidural & subarachnoid spaces
Gastrointestinal Changes w/ Pregnancy
↑risk regurgitation & aspiration
↑gastrin levels
Mechanical obstruction d/t upward displacement
Labor further ↓gastric emptying
What medications to administer prior to C-section to ↓aspiration risk?
- Bicitra (non-particulate antacid)
- Famotidine (Pepcid) H2 receptor antagonist
- Metoclopramide (Reglan) prokinetic that neutralizes stomach acid
Hepatic Changes w/ Pregnancy
↓serum albumin
↑free fraction highly protein-bound drugs
Renal Changes w/ Pregnancy
↑GFR
↓BUN & creatinine
Glucose excreted via urine d/t ↑GFR & ↓renal absorption
↑protein excretion
Uterine Blood Flow
Term ↑800mL/min
Receives 10% CO
- 150mL/min supplies nutrients to the myometrium
- 100mL/min flow to the decidua basalis (maternal portion placenta)
Fetus sends O2 poor blood to the placenta AVA
Placenta exchanges nutrients, respiratory gases, & waste
O2 & CO2 exchange are perfusion limited
How do medications transfer across the placenta? What is able to cross?
Transfer via diffusion
Other factors:
- Non-ionized
- Small (molecular weight)
- Dependent on concentration gradient & lipid solubility
- Protein binding
How much fetal CO returns directly back to the placenta? How?
1/5 fetal CO
Shunts flows from PFO & PDA
What affects drug accumulation w/in the fetus?
Acid-base status
Ion trapping
What decreases the fetal drug effects?
Dilution w/ intervillous blood
Redistribution w/in the fetus
1st pass liver effect
↑maternal hepatic enzymes ↓serum drug levels
Labor & Delivery
STAGE I
Cervix effacement & dilation
Latent - labor onset to rapid cervix dilation
Active - cervix dilation 2cm to full dilation at 10cm
Non-localized aching or cramping T10-12 & L1
Labor & Delivery
STAGE II
Cervix dilation 10cm to fetus delivery
Presenting part descends into the pelvis → perineal stretching S2-4
Labor & Delivery
STAGE III
Placenta delivery
Fetal Heart Rate
Variability
Indicates fetal well-being & O2 reserve
Hypoxia → CNS depression ↓HR
Accelerations are reactive - indicate fetal movement & adequate oxygenation
Fetal Heart Rate
Early Decelerations
Occur w/ uterine contractions
Consistent
↓fetal HR approximately 20bpm
Fetal Heart Rate
Variable Decelerations
Abrupt ↓HR irrespective to contractions
Baroreflex-mediated response to umbilical cord compression
Fetal Heart Rate
Late Decelerations
NON-REASSURING
Lowest deceleration point occurs after peak contraction
Represent uteroplacental insufficiency
Fetal Heart Rate
Category I
Normal baseline HR & moderate variability w/ NO variable or late decels
Fetal Heart Rate
Category II
All tracings not included in I or III
Do not indicate acid-base imbalance
Warrant continued observation
Fetal Heart Rate
Category III
Fetal bradycardia & absent variability w/ variable or late decels
Warrants prompt intervention
Labor analgesia dermatome level goal:
T10-L1
Caesarean section dermatome level goal:
T4-6 to provide adequate analgesia
Epidural 10-15mL
Combined Spinal/Epidural (CSE)
Place spinal 1st then place the epidural one level above
OR
Needle through needle technique
CSE Advantages
Lower spinal dose
Ability to re-dose w/ epidural catheter
CSE Disadvantages
Potential lower block height
Surgical start delay
Neuraxial Opioid Side Effects
Respiratory depression
Itching
Urinary retention
N/V
Opioids have ceiling effect beyond conventional doses
Caesarean Section Indications
Cephalopelvic disproportion Non-reassuring fetal status (ex: late decels) Failure to progress (dilation arrest) Malpresentation Prematurity Previous C/S or uterine surgery
Neuraxial Advantages over General
↓mortality risk d/t failed intubation
↓aspiration risk
Improved neonatal outcomes
Mother able to participate in birth
When to utilize L uterine displacement?
Regardless the anesthetic technique to prevent aorta compression → late decels
Spinal Advantages
Simple to perform
Rapid onset
Reliable block
Less toxic
0.75% hyperbaric Bupivacaine
DOA 90-120min
Spinal Disadvantages
Fixed DOA (single shot)
HoTN
Inadequate coverage
Epidural Advantages
Less abrupt blood pressure changes
Able to re-dose catheter
Epidural Disadvantages
Slower onset
Higher LA dose required
General Anesthesia Indications
Patient refusal
Coagulopathy
Spinal or epidural does not provide adequate surgical coverage
Urgent delivery
OB Complications
Post-Partum Hemorrhage
EBL >
- Vaginal delivery 500mL
- C-section 1,000mL
Post-Partum Hemorrhage
Causes & Risk Factors
Uterine atony 80% Uterine abnormalities Placental retention Lacerations Uterine inversion Coagulation abnormalities
Multiparity (previous pregnancy)
Prolonged oxytocin infusion
Polyhydramnios
Multiple gestation
Post-Partum Hemorrhage
Treatment
Uterotonics stimulate uterine contractions
- Oxytocin, Methergine, PGEs (Carboprost/Hemabate), and/or Misoprostal
Antifibrinolytics TXA
MTP and/or cell salvage
Surgical intervention
- Retained placenta, NTG, hysterectomy
Intrauterine balloon
Oxytocin
Synthetic Pitocin lowers depolarization threshold
Ca2+ channel activation & ↑prostaglandin production
20-40 units
Methylergonovine (Methergine)
Ergot alkaloid
0.2mg IM repeat Q15-20min
Max dose 0.8mg
NEVER IV BOLUS → profound HTN & cerebral hemorrhage
Contraindicated in pre-existing HTN, PVD, & ischemic heart disease
Prostaglandins
Carboprost (Hemabate)
↑myometrial Ca2+ levels & MLCK activity
250mcg IM or direct into myometrium repeat Q15-30min
Max dose 2mg
Reactive airway disease → bronchospasm, VaQ mismatch, & hypoxemia
Misoprostol
Prostaglandin E1 analog
↑myometrial Ca2+ levels & MLCK activity
800-1,000mcg sublingual or buccal
Okay to admin to patients w/ reactive airway disease or pulmonary HTN
Nitroglycerin
Nitric oxide donors
↑cyclic guanosine monophosphate
Inactivates MLCK causing smooth muscle relaxation
Administered as muscle relaxant to allow surgeon to remove retained placenta ↑bleeding
OB Complications
Preeclampsia
Pregnancy-specific multisystem disorder
Etiology not understood - failure normal angiogenesis resulting in ↓placental perfusion
↑vascular tone & sensitivity to catecholamines
Pronounced upper airway edema during labor
Preeclampsia S/S
HTN > 140/90 Proteinuria Thrombocytopenia < 100,000 Impaired liver function & severe RUQ pain Renal insufficiency Cerebral or visual disturbances CNS effects - headache, hyperexcitability, & hyperreflexia Hepatocellular necrosis
Preeclampsia Treatment
Avoid uteroplacental hypoperfusion Magnesium sulfate (tocolytic) ↓seizure incidence, venous dilation, ↓uterine activity HTN management Only way to end disease process = delivery
OB Complications
HELLP
Preeclampsia complication
Hemolysis, elevated liver enzymes, & low platelet count
Associated w/ progressive & sudden deterioration in maternal & fetal condition
HELLP S/S
HTN
Proteinuria
N/V
OB Complications
Obesity
> 20% pregnancies complicated d/t obesity
↑risk HTN, diabetes, & complicated labor → fetal macrosomia (LGA), failed induction/progression, difficult or failed neuraxial, prolonged procedures, & infectious complications
OB Complications
Placenta Previa
Abnormal placental implantation Placenta implants on lower uterine segment & covers the opening to the cervix 1% incidence Painless vaginal bleeding - Hemodynamically significant blood loss - ↑risk postpartum bleeding C-section indicated
OB Complications
Placenta Accreta
Placenta normally implants into the endometrium, but placenta accreta implants into the myometrium
Placenta increta describes growth through the myometrium & into surrounding organs
Associated w/ massive hemorrhage - uterine artery embolization & Caesarean hysterectomy
OB Complications
Placenta Abruption
Placenta separates from the uterus during delivery
More common in women w/ HTN & PEC
Open venous sinuses allows amniotic fluid to enter circulation ↑DIC incidence
Placenta Abruption S/S
Hemorrhage Painful vaginal bleeding Uterine irritability Abdominal pain Fetal hypoperfusion & distress
OB Complications
Amniotic Fluid Embolism
Rare event
Potential to occur during labor (vaginal delivery or C-section)
Occasionally associated w/ placenta abruption
Amniotic Fluid Embolism
S/S
Anxiety Dyspnea Hypoxia HoTN Cardiovascular collapse Coagulopathy
Amniotic Fluid Embolism
Treatment
Supportive AOK - Atropine - Ondansetron - Ketorolac
OB Complications
Prematurity
Labor & delivery before 37 weeks gestation
Birth weight < 1,500g associated w/ long-term complications (respiratory distress syndrome, intracranial hemorrhage, & hyperbilirubinemia)
Non-Obstetric Surgeries in Pregnant Women
1-2% pregnant women require non-OB surgeries Most common = cerclage 2nd lap chole Avoid HoTN & maintain uterine perfusion Prevent premature labor Avoid surgeries in 1st trimester
APGAR
8-10 normal
4-7 moderate distress or impairment
0-3 immediate resuscitation
