OB I Flashcards
Risk factors in OB?
- Advanced maternal age
- african american race
- maternal obesity
- cesarean delivery
What is the big piece of advice Allen said in class that is always important for OB?
Always have the room prepped!
- Anesthesia services must be readily available continuously
- c-section should be started within 30 min of recognition of need
- most deahts occur during or after csection, 2x the risks compared to toher surgeries
- all patients are full stomach and are at risk for aspiration
When is RSI, application of cricoid pressure with ETT insertion necessary?
anything after 12 weeks
What is the “hallmark of successful anesthetic management of the pregnant woman”
Recognition of these changes and appropriate adaptation of anesthetic techqniques to account for them
What hormones contribute to some of the altered maternal physiology?
gastrin, relaxin, estrogen, progesteron, progestins?
- Hormonal produciton by the ovaries and placenta alters maternal physiology
- gastrin: increases gastric volume and lower pH
- Relaxan: causes relaxation of the ligamentous attachments of hte lower ribs widening, promotes lordosis, increase incidence carpal tunnel syndrome
- estrogen: nasal stuffiness, epistaxis, increase plasma renin activity, increase Na absorption and water rentetion (RAAS), increase stoke volume
- Progesterone: respiratory stimulant, smooht muscle relaxant- intestinal contractile inhibior, delays gallbladder motility, increase aldosterone (increase plasma volume)
- progestins: reduces lower esophageal sphincter tone, increase reflux
What is the mean weight gain in pregnancy? What contributes to the weight gain?
- Mean weight gain is 12 kg (26 lbs)
- uters= 1 kg
- amniotic fluid= 1kg
- fetus and placenta= 4 kg
- increase blood voluem and interstitial fluid= 2 kg
- deposition of new fat + protein= 4 kg
- 1st trimester= 1-2 kg
- 2nd and 3rd trimester= 5-6 kg increase in each
- obesity- recommended gain is less
- increase risk for adverse preganncy outcome and c-section
Recommended weight gain if BMI <18.5?
18.5-24.9?
25-29.9?
>30?
-
<18.5= 12.7-18.2 kg (28- 40 lb)
- ( RATE OF 0.45 KG/WK (1lb/week))
-
18.5-24.9= 11.4- 15.9 kg (25-35 lb)
- (rate of 0.45 kg/wk (1lb/week))
-
25-29.9= 6.8- 11.4 kg (15-25 lb)
- (rate of .27 kg/week (0.6 lb/week)
-
>30= 5-9.1 kg (11-20 lb)
- (rate of 0.23 kg /week (0.5lb/week)
CV changes in pregnancy?
- Heart size increase–> increased blood vol and increase force of contraction
- increase CO 50%
- svr decrease d/t progesterone (as well as PVR)
- HR, SV, LVEDV all up
- eccentric LV hypertrophy
- heart shift up and to the left d/t elevation of diaphragm
- accentuation of first heart sound (S1)
- Systolic ejection murmur is common
- possible S3 &S4 - no clinical relevance
- leftward displacement of PMI
- Mitral, tricuspid and pulmonic valves dilate
- aortic insufficiency would be pathologic!
- CVP, PAD and PCWP all stay normal!!!
When does maternal CO reach max value? In pregnancy or postpartum?
postpartum
What are hemodynamics like during peurperium?
peurperium= period immediately following deliver)
- CO and SV increase up to 75% of predelivery values and 150% above prepreganncy baseline
- during the next hour, CO decrease to 30% above pre-delivery (d/t decrease SV and HR)
- CO returns ot prepregnancy levels in about 2 weeks postpartum
- HR
- falls rapidly after delivery
- back to normal in about 2 weeks postpartum
- SV
- remains above prelabor values for 48 hours then begins declining
- studies ahve shownt hat anatomic (LV wall thickening) and funcitonal changes of the heart durign pregnancy are fully reversible
When is maternal cardiac output the greatest?
immediately following stage 2
What is BP affected by during pregnancy?
- age- increase age causing higher BP
- Position- left lateral position is when mom’s BP will be lowest
- parity- nulliparous have higher BP than someone that has had previous children
- Systolic, diastolic and MAP- should decrease, with diastolic decreasing the most
What is aortocaval compression?
- Decrease BP, decrease CO and impairment of UPBF (uteroplacental blood flow) caused by compression of great vessel (highest compression supince)
- Tx- left uterin deplacement (tilt mom to left via IV bag, blanket, etc)
- IV fluids
- vasopressors (ephedrine too)
- Aortocaval syndrome will cause increase in venous pressure in lower limbs
- there is collateral flow via the epidural venous plexus
What is a supine hypotensive syndrome?
- Up to 15% of term patients experience compression of the aorta when lying supine–> bradycardia and hypotension
- may take several minutes for instabilities to occur
- bradycardia is often preceded by tachycardia
- results form profound decrease in venous return
- 10-20% in SV and CO
- supine position should be avoided after 20 weeks
What is uteroplacental blood flow?
- UBF= (uterine arterial- uterine venous pressure)/ uterine vascular resistance
- UBF @ term= 500-700 mL/min
- uterine blood flow will decrease whenever perfusion pressure decreases or uterine vascular resistance increases. the uterine vascular bed lacks autoregulation because uterine arteries max dilated
- unable to dilate futher in time of hypotension/trauma
- therefore, UBF dependent on maternal BP and CO
- if mom’s BP is low, then placenta isn’t getting oxygenated enough
- no autoregulation in placenta!
What characteristics of drugs causes high rates of placental transfer?
- Low molecular weight
- small molecules
- poorly ionized- non ionized
- high lipid solubility
- low protein binding
Which anesthesia drugs have significant placenta transfer?
- IV anesthetic
- VA
- Opioids
- Benzo
- beta blocker
- magnesium
Which drugs have no transfer across placenta?
- NMB
- glycopyrrolate (robinol)
- heparin
- insulin
Respiratory changes in OB patient?
- Despite mutiple naatomic and physiologic changes during pregnancy, lung function is only slightly impacted
- AP and transver diameters increase by 2 cm
- thoracic cage circumference
- increase 5-7 cm
- vertical measurement of chest
- decrease 4 cm from the elevation of the diaphragm
- elastin causes changes
- capillary engorgmenet
- oral, nasal and larynx mucosa
- increase in nose bleeds (d/t engorgement)
- estogen related
- oral, nasal and larynx mucosa
How are lung volumes affected during pregnancy?
- TLC- down 5%
- VC- no change
- IC - increas 15%
- IRV- increase 5%
- TV- increase 45%
- FRC- decrease 20%
- ERV- decrease 25%
- RV- decrease 15%
What makes up inspiratory capacity (IC)
What makes up Functional Residual Capacity (FRC)
What makes up TLC?
IC= IRV +TV (inspriatory reserve volume and tidal volume)
FRC= ERV + RV (expiratory reseve volume + residual volume)
TLC= IC + FRC
Would we expect Pao2 to be higher in pregnancy or non pregannt?
PaCO2?
Denitrogeination achieved faster in pregnancy or non pregnant?
PAO2- higher in pregnant
PACO2- higher in non pregnant
Denitrogeination- faster in pregnancy
Other respiratory changes noted?
Why changes?
Minute ventilation?
- Dyspnea is common (75% of women)
- Increased respiratory drive
- decreased PaCO2 (causes respiratory alkalosis)
- Increased oxygen consumption from enlarging uterus and fetus
- larger pulmonary blood volume
- anemia
- nasal congestion
- minute ventilation- increase d/t progesterone
- 70-140% (1st stage of labor)
- 120-200% 2nd stage labor
What b/g state is comon pregnancy?
respiratory alkalosis
Respiratory anesthetic implications?
- The proportion of pregnant women with mallampati IV increase by 34% between 12-18 weeks vascular engorgement of the airway- edema of oral and nasal pharynx, larynx and trachea–> dififcult intubation!!
- bleeding!!
- probably shouldn’t use a nasal airway
- airway edema may be exacerbated in pts with URI or preelampsia or those who have been pushing for a long time
- Hypoxemia develops more rapidly in pregnant female during apnea
- d/t decrease in FRC
- Increase in oxygen consumption
- FRC <closing></closing>
- Enlarged breasts and redundant tissue in neck
What happesn in RSI in pregnant female?
- PaO2 declines twices as rapidly
- denitrogenation is achieved faster in pregnant vs non pregnant female
- increase in minute ventilation and decrease in FRC
- parturients tolerate only 2-3 min of apnea vs 9 min in nonpreg pt before O2 decreases to <90%
Anesthesia implication in tracheal intubation in pregnancy?
- Increased rate of decline in PaO2 during apnea
- smaller ETT required (6.5/7)
- Increased risk for dififuclt or failed mask ventilation
- increased risk for failed intubation with traditional laryngosocpy
- increased risk for bleeding with nasal instrumentation
Difficult airway management in pregnancy
- Be prepared for difficult intubation with emergency airway cart
- avoid manipulation of upper airway- avoid aggressive suctioning, insertion of airways
- proper positoning of patient, including HOB up
- use smaller ETT 6/6.5
- Use short stubby laryngoscopy handle (datta)
- first attempt is best chance at intubation
- regional when possible
What are some hematological changes in pregnant female?
- maternal plasma volume increase by 50% by 34 weeks’ gestation
- although RBC volume increase, the increase in plasma volume exceeds the increase in RBC volume–> physiologic anemia of pregnancy “dilutional anemia”
-
The physiologic hypervolemia
- delivery of nutrients to fetus
- protects the mom from hypotension
- reduces hemorrhage risk at delivery
What happens to plasma protein values during pregnancy?
- total protein decreased
- albumin decreased
- plasma cholinesterase decrease- don’t need to alter dose of succinylcholine howver
- colloid osmotic pressure decreases
What is an early deceleration?
- Begins when the contraction begins, and returns to baseline when the contraction ends
- significant- head compression resulting in vagal stimulation
- characteristics:
- occur simultaneously with each uterine ctx
- onset/offset of decel PARALLELS the onset/offset of each ctx
- uniform in appearance
- a/w mild decrease in FHR (20bpm or less)
- accompanied by loss of beat-to-beat variability during the decel
- early decels are NOT ominous
What are variable decels?
- Sudden decrease in FHR that occur irrespective of uterine ctx
- significance- umbilical cord compression
- Most common
- varied appearance, duration, depthy and shape (V or U shaped)
- demonstrate abrupt onset and recovery
- maintain beat to beat variability
- SEVERE–>FHR drops by 60 bpm, if FHR drops to <60 bpm, or if decel last >than 60 seconds need immediate intervention!!
What are late decels?
- Significance: uteroplacental insufficiecy
- causes: maternal hypotension, hypovolemia, acidosis, preeclampsia
- intervention: requires urgent asessment of fetal status. MOST OMINOUS TYPE OF DECEL-LATE with lack of beat-to-beat variaiblity
- Characeristics of late decels:
- begin 10-30 seconds after beginning of uterine ctx and end 10-30 sec after completion of ctx
- occur with each fetal ctx
- low point of decel after peak of ctx
- gradually decrease in rate and end in a return to baseline
- are uniform in appearance
- vary in depth according ot strenght of ctx
- may be subtle
- may or may not be accompanied by beat-to-beat variability
