Ex1 OB 1 Flashcards
1
Q
CVS system changes in pregnancy
A
increased HR, SV
therefore increased CO
2
Q
Respiratory system changes in pregnancy
A
- displacement of diaphragm superiorly
- decreased FRC
- increased risk of apnea/dyspnea
- hyperventilation
3
Q
GI changes during pregnancy
A
- N/V
- heart burn + acidity
4
Q
Major cardiovascular changes during pregnancy
A
- increased intravascular volume
- increased cardiac output
- decreased vascular resistance
- supine HOTN
5
Q
Changes to the heart during pregnancy
A
heart enlarges, displaces upward + to Left
6
Q
Why does CO change during pregnancy?
A
Increase in both HR, SV
Decrease in SVR
7
Q
Decreased SVR is due to
A
initiating factor: estrogens, progesterone, prostacyclin
8
Q
CO is greatest when?
A
Right after delivery
9
Q
When does moms CO return to baseline?
A
~ 2 weeks after delivery
10
Q
What compensates for the blood loss during delivery?
A
contractions of engorged uterus provide 300-500mL autotransfusion into maternal circulation –> increased CO
11
Q
Common cause of moms HOTN
A
While laying flat on back: weight of placenta + amniotic sac can compress IVC
12
Q
Increased risk of ____ in mom d/t decreased vascular resistance/venodilation?
A
epidural vein puncture
13
Q
While placing epidural, what should be ensured?
A
Remaining midline (avoid epidural veins)
14
Q
90% of pregnant women have a ____
A
late systolic or ejection murmur
15
Q
Common murmurs in pregnant women are attributable to
A
increased stroke volume
decrease in blood viscosity
16
Q
At term, what may be seen on the CXR?
A
Larger cardiac silhouette d/t diaphragm shifting heart up + Left
17
Q
What changes may be seen in 3rd trimester on EKG?
A
Increased incidence of dysrhythmias (PAC, PVC, SVT) d/t Left Axis shift on ECG
18
Q
Second trimester
A
20-28 weeks gestation
19
Q
important but preventable cause of fetal distress
A
aortocaval compression
-after 20-28w gestation
20
Q
aortocaval compression
A
gravid uterus obstructs aorta + inferior vena cava (while supine) –> no blood supply to placenta (uteroplacental circulation) –> no blood supply to baby –> asphyxia
21
Q
What will be seen on the fetal heart monitor if aortocaval syndrome occurs?
A
Late decelerations
22
Q
How to avoid aortocaval syndrome?
A
Tilt parturient to left side
23
Q
3rd trimester
A
29-40 weeks
24
Q
Cause of LE edema, venous stasis
A
Chronic partial caval obstruction in 3rd trimester
25
Beginning location of aortic compression
L3-L4
| upper body BP may remain normal
26
Changes in blood volume during pregnancy are due to
increased mineralocorticoid activity --> sodium retention + increased body water content
27
Blood volume changes during pregnancy
increased:
plasma volume ( +50%
total blood volume (+45%)
red cell volume (+25%)
28
Which increases more during pregnancy: plasma volume or red cell volume?
Plasma volume
29
Changes in blood volume lead to ____ during pregnancy
relative dilutional anemia
30
TBV at term
85-100 mL/kg
31
Healthy parturients can tolerate up to _____ mL blood loss without a transfusion
1500mL
32
High Hgb levels may indicate
Normal Hgb > 11
High Hgb = > 14
*may indicate low volume state caused by preeclamsia, HTN, or inappropriate diuresis
33
Approximate intravascular volume change
1000-1500 mL
| *helps compensate for EBL
34
EBL vaginal
300-500 mL
35
EBL section
800-1000mL
36
Coagulation changes during pregnancy
- coagulation factors + fibrinogen increase
| - platelets remain same or decrease 10% during 3rd trimester
37
Factors that increase during pregnancy
I, VII, VIII, IX, X, and XII
38
Factors that decrease during pregnancy
XI and XIII
39
Coagulation lab changes in pregnancy
PT -20%
PTT -20%
No change: platelets or bleeding time
40
Coagulation lab changes in pregnancy: thromboeleastography
hypercoagulable
41
Coagulation lab changes in pregnancy: antithrombin III
decreased
42
Coagulation lab changes in pregnancy: fibrin degradation products
increased
43
Coagulation lab changes in pregnancy: plasminogen
increased
44
What may worsen airway edema in pregnancy?
- preeclampisa
- trendelenberg position
- Tx w/ tocolytics
45
Average size ETT in pregnancy
6-6.5
46
changes in airway during pregnancy
- capillary engorgement of mucosal lining
- mucous membranes = friable
- swelling of false vocal cords (narrowed glottis)
- weight gain/breasts = hinder laryngoscopy
47
key for successful airway placement
- proper axis alignment (via positioning)
- short laryngoscopy handles
- know where glidescope is at all times (video laryngoscope)
48
What does diaphragmatic elevation cause?
- less negative intrathoracic pressure
| - decreased FRC, ERC, RV (20%)
49
significant PFT changes
compensatory increase in thoracic anterior-posterior diameter
50
What change in moms body causes the majority of respiratory changes?
Hormones (increased progesterone)
+
Enlarged Uterus
51
What physical changes in moms body causes respiratory changes?
Enlarged uterus --> ribcage becomes wider, back broader (+ diaphragm pushed up)
52
Why is mom at a higher risk of rapid oxygen desaturation during periods of apnea?
Combo:
| decreased FRC + increased O2 consumption
53
What is mandatory prior to GA in pregnant patients?
Preoxygenation
54
Risk of pain/anxiety during labor in relation to respiratory system
increased RR --> hypocapna, faintness, perioral numbness
| --> fetal hypoxia/distress
55
What occurs to 2,3-DPG during pregnancy?
| Why does this change?
- 2,3-dpg concentration increases
| - lowers affinity of maternal Hgb for O2
56
Reason for change of 2,3-dpg
Lowers moms affinity of Hgb for O2 --> facilitates dissociation of oxygen from Hgb thru intervillous space in placenta, enhances delivery of O2 to growing fetus
57
Dissociation curve is affected during pregnancy how?
increased 2,3-DPG shifts O2 Hgb dissoc. curve to the Right (P50 increases from 27-30 mmHg)
58
Most significant Respiratory changes
Decreased FRC
No change in VC
Increased TV
Decreased ERV
59
When does mom's minimal alveolar concentration return to normal?
3 days post-partum
60
Effect of pregnancy on MAC
decreases by up to 40%
61
Cause of changed MAC during pregnancy
Progesterone + B-endorphin
62
Pregnant patients reaction to local anesthetics + cause
enhanced sensitivity d/t increased spread of LA in epidural/subarachnoid spaces (occurs d/t epidural venous engorgement)
63
Parturient is highly dependent on _____ for blood pressure control
SNS
64
D/t increased SNS role in parturient, what occurs after regional anesthesia?
significant decrease in BP
65
When does SNS return to normal?
36-48 hours postpartum
66
cause of constipation during pregnancy
progesterone --> slowed GI motility --> enhanced water absorption
67
All moms after ______ (time) are at risk for what?
12 weeks +
increased risk for aspiration
RSI
68
If GA is administered to parturient, what should also be given?
- nonparticulate antacid (Bicitra)
- H2 blocker
- Reglan (consider)
69
What occurs to GFR during pregnancy?
- Increased by 50% in 1st trimester
| - declines to normal in 3rd trimester
70
Hepatic effects during pregnancy
Serum cholinesterase activity decreases by ~ 30%
| NOT clinically relevant for sux/mivacurium
71
When does pseudocholinesterase activity return to normal?
6 weeks postpartum
72
Effect of pregnancy on urine labs
```
Mild glucosuria (1-10g/dL) or proteinuria (<300mg/dL)
d/t decreased renal tubular threshold for glucose/amino acids
```
73
What joins the mother and fetus?
Placenta
74
Uterine blood flow receives how much CO?
10% CO at term (600-700mL/min)
| nongravid = 50mL/min
75
T/F: the uterus is capable of autoregulation
False
76
Uterine perfusion is dependent on
- adequate driving pressure (uterine arterial pressure)
- low uterine venous pressure
- low uterine vascular resistance
77
Increased uterine venous pressure _____ uterine blood flow
lowers
78
Increased uterine venous pressure is d/t
```
Caused by:
Vena caval compression
Uterine contractions
Drug-induced hypertonus (oxytocin, LA)
Skeletal muscle hypertonus (seizures, valsalva)
```
79
Increased uterine venous resistance ______ uterine blood flow
lowers
80
Causes of increased uterine venous resistance
1. endogenous vasoconstrictors
| 2. exogenous vasoconstrictors
81
Endogenous vasoconstrictors that may cause increased UVR
- catecholamines (stress)
| - vasopressin (in response to hypovolemia)
82
Exogenous vasoconstrictors that may cause increased UVR
- epinephrine
- vasopressors (phenyl, ephedrine)
- local anesthetics in high concentrations
83
Transfer of oxygen from mom to baby is dependent on
ratio of maternal UBF to fetal blood flow
84
oxygenated blood from placenta has PaO2 of
40mmHg (80% saturated)
85
fetal Hgb O2 dissociation curve is shifted ____
to the Left
| HgbF > affinity for O2 than HgbM
86
Fetal Hgb vs. Mom Hgb
Fetal ~ 15 g/dL
| Mom ~ 12 g/dL
87
transport of anesthetics from mom to baby occurs via
passive diffusion
88
The rate of transfer of anesthetics from mom to baby occurs based on
Fick Principle
89
Factors that promote rapid diffusion (anesthetics from mom to baby)
* most anesthetics
* NOT muscle relaxants
- low molecular weight (<500 daltons)
- high lipid solubility
- low degree of ionization
- low protein binding
90
Ion trapping
fetal acidosis/low pH --> Rx = greater tendency to exist in ionized form, unable to diffuse back across placenta into maternal plasma --> Rx trapped in fetus (larger amounts)
91
Rx used to stimulate/strengthen uterine contractions
oxytocics
92
Rx used to delay/stop premature labor
tocolytics
93
Oxytocics indications
- induce/augment labor
- control PP bleeding/uterine atony
- induce therapeutic abortion
94
Oxytocics
- Oxytocin (pitocin)
- Ergot alkaloids: Ergonovine (ergotrate), Methylerogonovine
- Prostaglandin 15-methyl F2a
95
Oxytocin MOA
Acts on uterine smooth muscle to stimulate the frequency and force of contractions; potent vasodilator
96
Oxytocin S/E
CV effects: vasodilation, HOTN, tachycardia, arrhythmias
-high doses: may have antidiuretic effect + produce water intoxification, cerebral edema, convulsions
97
Oxytocin dosage
- diluted (20-40 u/L)
- IV infusion
- NEVER BOLUSED/PUSHED
98
Risk of Oxytocin
Added preservative (chlorbutanol) = vasodilatory + negative inotropic effects
99
Mom complains of N/V after oxytocin given, what can you assume?
BP will drop soon, even if it doesn't show it yet. Slow down drip.
100
Ergot Alkaloids - MOA
small doses: increase force + frequency of uterine contractions
high doses: contractions more intense, prolonged, resting tone increased, tetanic contractions occur
101
Ergot Alkaloids - Rx
Most commonly used: methergine (methylerogonivine)
102
Methergine A/E
CV: vasoconstriction, HTN augmented in presence of pressors
103
Ergot Alkaloids: restrictions
Administration is restricted to 3rd stage of labor to control postpartum bleeding
104
Methergine Administration
- ONLY IM, 0.2mg
| * prefer to give in thigh if spinal/epidural given
105
Methergine - avoid in
PVD, HTN, CAD
106
Methergine - why not IV?
associated with severe HTN, convulsions, stroke, retinal detachment, pulm edema
107
Prostaglandin 15-methyl F2a
Hemabate
| "carboprost tromethamine"
108
Hemabate
3rd line Tx for uterine atony
| goal: achieve uterine contraction
109
Hemabate SE
transient HTN, severe bronchospasm, increased PVR
110
Hemabate avoid in
asthmatics
111
Hemabate administration
0.25mg IM
or intramyometrially (OB)
*must be refrigerated, $$$$
112
Tocolytics are used for
delay or stop premature labor
- used for fetuses gestational age 20-28 weeks
- cervical dilation < 4cm + effacement < 80% associated with greater likelihood of terminating premature labor
113
Tocolytics C/I
- chorioamnionitis
- fetal distress
- intrauterine fetal demise
- severe or chronic pregnancy-induced HTN
- severe hemorrhage
114
Terbutaline
Selective B2-adrenergic agonist
| -used to inhibit preterm labor by producing myometrial inhibition by directly relaxing uterine smooth muscle
115
Terbutaline SE
```
maternal bronchodilation
vasodilation
tachycardia
hyperglycemia
hypokalemia
hyperinsulinemia
metabolic acidosis
```
116
What is magnesium sulfate used for in OB?
Preeclampsia + tocolytic agent
117
MOA Mag Sulfate
- reduces presynaptic release of Ach, which decreases hyperactivity at neuromuscular junction, thus weakening contractions
- physiologic calcium antagonist, prevents increase of free intracellular calcium
118
Mag Sulfate Administration
1. Loading dose (4gm over 20 min)
Followed by
2. Infusion (2-4g/hr)
119
Mag Sulfate SE
sedation, flushed face, hypotension, heart block, skeletal muscle weakness, respiratory depression, cardiac arrest
*flushed, weak, tired, soft, mushy
120
Mag Sulfate Safety Precautions
Soft, boggy uterus --> high risk for PPH.
| *have blood available, may need methergine, make sure T&C
121
Other agents used to delay preterm labor
Indomethacin
| Nifedipine
122
Indomethacin MOA
NSAID that inhibits prostaglandins
123
Nifedipine MOA
CCB
124
most common drug given systemically to mother
opioids
125
Opioids AE
- cross placental circulation freely (RR depression in newborn), limited to early stages of labor OR regional not available
- maternal SE: RR depression, N/V, altered MS
126
If regional not available, best option?
Remifentanil bolus PCA
127
Duramorph
preservative free morphine used in spinal/epidural
128
Which opioid is not used and why?
- Morphine not used
| - excessive RR depression in neonate
129
Duramorph administration
10mg/10mL (1mg/mL)
or
5mg/10mL (0.5mg/mL)
130
Duramorph administration for spinal vs epidural
Spinal: use TB syringe (small amount)
Epidural: use normal syringe (bigger volume)
131
Fentanyl use in OB
-adequate labor analgesia with minimal neonatal depression
132
Maternal effects from Fentanyl
Maternal respiratory depression outlasts analgesia
| -do NOT give near delivery
133
Neonatal effects from Fentanyl
- transient decrease in FHR variability noted
| - doses of 1mcg/kg no adverse effects
134
Fentanyl administration
```
25-50 mcg IV
peak 3-5 min
DOA 30-60min
Best: epidural/spinal
Not-ideal: IV/PCA
```
135
Reason for using Butorphanol or Nalbuphine
produce less N/V than other opioids
136
Butorphanol MOA
"Stadol"
| kappa-agonist + mu-antagonist, minimal affinity for delta receptors
137
Butorphanol administration
1-2mg IV/IM
| DOA up to 4h
138
Nalbuphone MOA
"Nubain"
| partial kappa-agonist + mu-antagonist, minimal delta activity
139
Nalbuphone administration
10mg IV/IM
| DOA up to 6h
140
Nalbuphone Equipotent dose
10mg morphine = 10mg Nalbuphone
141
Remifentanil compared to epidural
Remifentanil less effective than standard epidural
142
PCA remifentanil dosage
0.25 mcg/kg q2 minutes
143
Remifentanil characteristics
- ultra-short acting with context sensitive 1/2t = 3.2 minutes
- crosses placenta readily, rapidly redistributed + metabolized by fetus
144
When is ketamine used?
Adjunctive, used for "hot spot", subanesthetic doses = result in analgesia w/o LOC or loss in reflexes
145
Disadvantages of Ketamine
HTN, emergence delirium
146
Advantages of Ketamine
Maintains maternal CVS + uterine blood flow
147
Ketamine dose
0.25-0.5 mg/kg IV
or
10 mg q2-5min IV
148
High doses of ketamine may cause
High doses ( > 2mg/kg)
psychomimetic effects
increased uterine tone (+ low Apgar score)
149
Typical duration of C/S
45 minutes
150
Most frequently used inhalational technique
outside of US: 50:50 N2O + O2
