Obstetrical Anesthesia Flashcards
RSI, application of cricoid pressure, and a cuffed ETT is needed for pregnant women receiving general anesthesia after the __________.
first trimester
What are 3 lung capacities that do not change during pregnancy?
vital capacity, total lung capacity, and inspiratory capacity
Would you expect PaO2 to be higher in pregnant or non-pregnant state?
pregnant
*CO2 would be higher in the non-pregnant state
What happens to the diaphragm in pregnancy?
displaced cephalad about 4 cm by the expanding uterus
An increase in oxygen consumption produces a ______% increase in alveolar ventilation at term.
70
Why do pregnant pt’s desat quickly?
they have a decreased FRC and increased alveolar ventilation resulting in faster desaturation
*an increased maternal oxygen consumption and any episodes of apnea will lead to maternal hypoxia
When is airway edema most evident?
airway edema d\t engorgement is most evident during the third trimester
What central hemodynamics increase at term?
increase: \+50% in CO \+25% in SV \+25% in HR LVEDV EF
What central hemodynamics decrease at term?
decrease:
-20% in SVR
What happens to CVP in the parturient at term?
no change
What happens to LVESV in the parturient at term?
no change
What happens to PCWP in the parturient at term?
no change
What happens to pulmonary artery diastolic pressure in the parturient at term?
no change
What two changes result in a dilutional anemia in the parturient at term?
a +45 % increase in blood volume, but another +55% in plasma volume
What is a typical H&H in the parturient at term?
11.6/35.5%
What is maternal supine hypotensive syndrome?
compression of IVC decreases venous return and this will result in decreased SV and hypotension
What is another name for maternal supine hypotensive syndrome?
aortocaval syndrome
How can you treat maternal supine hypotensive syndrome?
LUD–> left side with wedge under right hip 15%
Blood flow to uterine vasculature is approximately _______.
700-800ml/minute
must keep maternal SBP >100mmHg to ensure perfusion
Why does the increase in blood volume not cause an increase in BP?
due to a decrease in peripheral vascular resistance
A healthy parturient will tolerate up to _____ml of blood loss.
1500mL
A high Hgb of >14 can indicate a low volume state caused by ________. (3)
1) preeclampsia
2) HTN
3) inappropriate diuretics
Why do women with cardiac and pulmonary disease remain at risk after delivery?
b\c CO remains high in the first few hours following postpartum (80%)
Cardiac output during labor:
Latent Phase - increases ________%
15%
Cardiac output during labor:
Active Phase - increases ________%
30%
Cardiac output during labor:
Second Stage - increases ________%
45%
Cardiac output during labor:
Postpartum - increases ________%
80%
Always avoid aortocaval compression: _______% of supine parturients with a T4 sympathectomy develop significant hypotension.
70-80%
What clotting factors increase at term?
1, 7, 8, 9, 10, 12
What clotting factors decrease at term?
11, 13 (thromboplastin and fibrin stabilizing factor)
What happens to LES tone and gastric emptying during pregnancy? What causes this change?
decreased; d\t circulating progesterone
*also decreased GI motility, food absorption
Elevated _____ from the placenta increases intragastric pressure, making the patient prone to ______.
gastrin; reflux
What do narcotics, valium, and atropine d\t LES tone and gastric emptying time?
decrease LES tone and prolong gastric emptying time
_________ increases LES tone and increases gastric emptying.
metoclopramide
What happens to BUN and creatinine during normal maternal changes?
decreased d\t increases in renal blood flow and GFR
What happens to renal blood flow and GFR by the fourth month of gestation?
increases by 50-60%, but slowly returns to normal during third trimester; GFR remains elevated until delivery
Describe how maternal blood circulates through the placenta.
maternal blood is carried initially in the uterine arteries—> blood is spurted into intervillous space—> blood in this space passes fetal villi before draining back to veins of the uterine wall
How many microscopic layers are found in the placental membrane?
3
General Anesthesia Changes During Pregnancy:
MAC is reduced by ______.
15-40%
General Anesthesia Changes During Pregnancy:
What are some considerations for ETT choice and intubation?
use small tube, aspiration risk, RSI, cricoid, engorgement, increased risk of failed intubation, increased MV required
Regional Anesthesia Changes During Pregnancy:
The curvature of the spine is the parturient is increased and termed as ______.
lumbar lordosis is increased
Regional Anesthesia Changes During Pregnancy:
Does subarachnoid dosing change for the parturient?
reduce subarachnoid dose by 25%
Regional Anesthesia Changes During Pregnancy:
Does epidural dosing change for the parturient?
epidural dose (large dose) unaltered epidural dose (small dose) reduced
Name 3 things that result in an increase in uterine blood flow.
1) pain relief
2) decreased sympathetic activity; no pain
3) decreased maternal hyperventilation; no pain
Name 3 things that result in an decrease in uterine blood flow.
1) hypotension (maternal SBP <100)
2) unintentional IV injection of local anesthetic and/or EPI
3) absorbed local anesthetic (little effect)
What is the first stage of labor?
from onset of contractions to complete dilation of the cervix
1) latent- little dilation of cervix, but becomes softer
2) active- regular cervical dilation
pain T10-L1—-> “First Four”
What is the second stage of labor?
begins at full cervical dilation (10cm) and ends with delivery of infant
pain T10-S4 dermatomes–> “Second Sacrum”
What signals the start of the second stage of labor?
onset of perineal pain at the end of the first stage of labor is the signal of fetal descent and the beginning of the second stage
Sensory innervation of the perineum is provided by the ______ nerve (S2-S4).
pudendal nerve
What is the third stage of delivery?
delivery of the placenta
What is the most commonly used opioid for parturients?
meperidine 10-25mg IV or 25-50mg IM
This drug is most useful prior to delivery or as an adjunct to regional anesthesia.
ketamine 10-15mg IV with good analgesia in 2-5min
Why are NSAIDs such as Ketorolac not recommended for the parturient?
d\t suppression of uterine contractions; promotes closure of fetal ductus arteriosus
What are benzodiazepines not recommended for the parturient?
strong potential to cause prolonged neonatal depression
What are 3 advantages of spinal opioids?
1) preservative free
2) useful in high risk patients
3) they do not impair mom from pushing the baby out
What are 3 disadvantages to spinal opioids?
1) less complete analgesia
2) lack of perineal relaxation
3) pruritus, nausea, vomiting, sedation, and respiratory depression
What is the most common side effect of regional anesthesia?
hypotension= 20-30% decline in BP or a SBP <100
What is the most common cause of hypotension in regional anesthesia?
d\t decreased sympathetic tone with aortocaval compression in the upright position
What is the treatment for hypotension associated with regional anesthesia?
1) ephedrine boluses (25-50mg)
2) oxygen
3) LUD
4) IV fluids
* small doses of phenylephrine (25-50mcg) may also be used
Regional Anesthesia:
What do you do in the event of an unintentional IV injection?
1) avoid head up position
2) LUD
3) treat seizures if manifested (thio, prop, midaz)
4) Bupivacaine induced cardio collapse can be treated with 20% intralipid 1.2-2ml/kg
5) intubate and ventilate
Regional Anesthesia:
What do you do in the event of an unintentional intrathecal injection?
1) supine with LUD
2) treat hypotension with ephedrine and fluids
3) high spinal may need intubation
Regional Anesthesia:
What do you do in the event of a PDPH with mild h\a?
1) bed rest
2) hydration
3) oral analgesics
4) epidural saline injection (50-100ml)
5) caffeine sodium benzoate (500mg)
Regional Anesthesia:
What do you do in the event of a PDPH with moderate to severe h\a?
1) epidural blood patch (10-30cc)
2) prophylactic EBP not recommended
What is considered to be nonreassuring fetal heart rate patterns?
1) repetitive LATE decelerations
2) loss of beat-to-beat variability
3) sustained FHR <80
What are signs of fetal distress?
- NRFHT’s
1) repetitive LATE decelerations
2) loss of beat-to-beat variability
3) sustained FHR <7.20 - meconium stained amniotic fluid
- oligohydramnios (too little fluid)
- intrauterine growth restriction
What 4 P’s go with placenta previa?
P-painless vaginal bleeding (2nd or 3rd tri)
P-Preterm bleeding
P-Planned (known about it in most cases)
P-Pass on pushing
When do fetal lungs mature?
37 weeks
What is the initial treatment for placental previa?
bedrest and observation
*avoid vaginal exams–> placenta is covering vaginal opening
What is the goal for placental previa?
delay the delivery until the fetus is mature–> c-section (urgency based on maternal hypotension)
When is the first episode of bleeding for placenta previa?
usually preterm and there are no contractions with the bleeding
_______ lying placenta previa increases the risk of excessive bleeding for c-section.
anterior
What can be used for confirmation of diagnosis of placenta previa?
ultrasonography
What is placental abruption?
like an O2 tank getting ripped off a scuba divers back–> separation of the placenta from the deciduas basalis before delivery of the fetus—> acute bleeding, which is often hidden
What is the cause for fetal distress with placental abruption?
loss of area for maternal fetal gas exchange–> late decels
What is the classic presentation of placental abruption?
1) painful bleeding
2) uterine tenderness
3) increased uterine activity
4) atypical presentation
With a placental abruption, the uterus can contain up to how much blood?
2500mL
What are some risk factors for placental abruption?
1) HTN
2) advanced age
3) parity
4) tobacco or cocaine use
5) trauma
* so basically vascular paths
Is regional more appropriate with placental previa or abruption?
PREVIA…. but still based on patient
NO REGIONAL FOR ABRUPTION (coagulopathy and uncertain uteroplacental BF)
What is the treatment for placental abruption?
NO DELAYS–> continued placental separation may lead to fetal death
What is the etiology of placental abruption?
unknown
What are the 3 abnormal placental implantation defects?
1) Placenta Accreta Vera
2) Placenta Increta
3) Placenta Percreta
List the 3 abnormal placental implantation defects in order from most to least prevalent?
1) Placenta Accreta Vera 78%
2) Placenta Increta 17%
3) Placenta Percreta 5%
What is Placenta Accreta Vera?
ADHERES to the myometrium without invasion of or passage through the uterine muscle
What is Placenta Increta?
INVADES and is confined to the myometrium
What is Placenta Percreta?
invades and may PENETRATE the myometrium, the uterine serosa, or other pelvic structures
KNOW
PREVIA– playing peek a boo
ABRUPTION– there’s an “abruption” that is… “eruption” of blood
IMPLANTATION DEFECTS= AIP (accreta, increta, percreta)
Adhere, INVADE, and PROTRUDE the myometrium
If mom has had a placenta previa, previous c-section or had uterine trauma, she is at risk for developing _______.
placenta accreta
State whether regional anesthesia in a parturient with one of the following is wise:
- mitral valve disease
- aortic insufficiency
- congenital lesions with left to right shunting
yes its fine—> decreased preload, decreased afterload, reduced pulmonary congestion…. together the above may increase CO
State whether regional anesthesia in a parturient with one of the following is wise:
- aortic stenosis
- congenital lesions with right to left shunting
- primary pulmonary HTN
regional anesthesia is detrimental–> the decreased preload and afterload are detrimental
-best managed with intraspinal opioids alone, systemic medications, pudendal nerve blocks, and possibly general anesthesia
What is pre-eclampsia?
syndrome of HTN, proteinuria, and generalized edema occurring after the 20th week of gestation
What is eclampsia?
occurrence of convulsions superimposed on pre-eclampsia
What do you give for pre-eclampsia?
magnesium is for pre-eclampsia–> attenuates smooth muscle contraction by competing with calcium at the cell membrane level and preventing an increase in free intracellular calcium
*tocolysis–> improves uterine BF and antagonizes uterine hyperactivity (but this also prolongs labor and increases postpartum hemorrhage)
What is the normal plasma level of Magnesium?
1.5-2
What is the therapeutic plasma level of Magnesium for pre-eclampsia?
4.0-8.0
What are the neonatal effects of magnesium administration?
- lower APGAR scores
- decreased muscle tone (only with maternal overdose)
What type of deceleration is seen with cord compression?
variable decels
What type of deceleration is normal and results from head compression or stretching of neck during uterine contractions (vagal stimulation)?
early decels (Type I)
What type of deceleration is caused from uteroplacental insufficiency and fetal compromise with a decrease in HR?
late decels (Type II)
What position should be avoided in the parturient?
supine
This level of block is needed to be secured for a c-section.
T4
Is hyperglycemia a problem associated with infant prematurity?
No…. but the following is:
1) hypoglycemia
2) respiratory distress
3) hypocalcemia
4) hyperbilirubinemia
Which of the following is not a cause of neonatal depression at birth?
a) maternal HTN
b) trauma
c) drugs
d) prematurity
TRAUMA is not a cause
Is normal delivery of the placenta a common cause of postpartum hemorrhage?
No
What level of neural blockade is required for optimal anesthesia during the second stage of labor?
T10-S4
How much of the total uterine blood flow goes into the intervillous space (ml/min)?
550ml
