OB Anesthesia Exam #1 Flashcards
When do CV changes begin to occur during pregnancy?
they begin the 4th week of pregnancy
The HR increases ___ to ___% and peaks at ___ weeks gestation.
- 20 to 30%
- 32 weeks
Cardiac output increases to ___%(begins ____ week of pregnancy) and the stroke volume increases to ____ to ___%
- 40%
- 5th
- 20 to 50%
Cardiac output is at its greatest……
immediately after delivery as a result of increased central volume(may possibly get pulmonary edema or other CV issues)
Cardiac Output returns to baseline in ___ days
14
Thoracic changes during pregnancy:
- diaphragm rises
- heart shifts up and left
- heart appears enlarged on CXR
- ventricular walls thicken
- End-Diastolic volume increases
- Benign Grade I-II SEM(normal)
- Diastolic Murmurs pathologic(consult cardiology)
Auto transfusion amount?
With adequate neuraxial analgesia, HR tends to drop wit each contraction. Why?
SVR?
LVE systolic volume/EF?
- 300-500 ml/contraction
- lower HR due to compensatory mechanism 2ndary to increased volume
- SVR changes(decrease ~20% by end-term) due to decreased resistance in the uteroplacental, pulmonary, renal and cutaneous vascular beds.
- decreasing SVR affects Diastolic pressure leading to a decrease in MAP
- L ventricular end-systolic/EF=increased
CV CHANGES: cardiac output? stroke volume? heart rate? diastolic BP? systolic BP? mean arterial pressure? total peripheral resistance? systemic vascular resistance CVP/PCWP?
CO +40% SV +20 to 50% HR +20 to 30% DBP -10 TO 20 MMHG SBP -0 TO 15 MMHG MAP -15 MMHG (BLOOD PRESSURES DECREASED DUE TO DILATED VASCULAR BEDS) PVR -15% SVR -20%
What is Supine Hypotensive Syndrome? and when does it become significant?
- syndrome is caused by compression of Vena Cava by gravid uterus, which restricts venous return decreasing preload
- becomes significant at 20 weeks
What are the signs and symptoms of Supine Hypotensive Syndrome?
- max drop in BP may take 10 min to develop
- normal physiologic response is tachycardia and vasoconstriction of lower extremities
- results is decreased uterine BF and fetal oxygenation
- mom may display diaphoresis, nausea, lightheaded, vomiting, pallor or “feeling faint”
What should be done if patient is experiencing supine hypotensive syndrome?
raise right hip and tilt onto left hip displacing the uterus off the vena cava
This position should be avoided in the OB patient:
- semi fowler’s
- prone
- lateral
- supine
supine
What is the primary hematology changes during pregnancy?
“Hypercoagulable”
- Fibrinogen normally 200-400 goes to 400-650 mg/dl
- parturient at risk of embolic event(one of the leading causes of maternal mortality)
- platlets normal..slightly decreased in 3rd trimester
- WBC rises during pregnancy. Mean-10500 and in labor may rise to 20000-30000
- during pregnancy the P-50 of maternal hemoglobin increases to about 30 mmHg
During pregnancy, what clotting factors are increased, decreased and unchanged?
INCREASED: factors I(fibrinogen), VII(proconvertin), VIII(antihemophiliac), IX(christmas factor), X(stuart-prower factor), XII(hageman factor)
DECREASED: factors XI(thromboplastin antecedent), XIII(fibrin-stabilizing)
UNCHANGED: factors II(prothrombin), V(proaccelerin)
Coagulation Laboratory Test changes: PT- PTT- TEG- Fibrinopeptide A- Antithrombin(AT)- Platelet count- Bleeding time- Fibrin Degradation Products-
- shortened 20%
- shortened 20%
- hypercoagulable
- increased
- decreased
- no change or decreased
- no change
- increased
TBV increases\_\_\_\_? Plasma volume increases \_\_\_\_? RBC volumen increases\_\_\_\_? Why are plasma/blood volumes increased? What is the result of these increases?
- 25-40%
- 40-50%
- increases 20%
- increased plasma volume due to increased levels of progesterone and estrogen
- Result: relative or dilutional anemia exists
- increased progesterone and estrogen yield enhanced renin-angiotensin-aldosterone activity*
- RBC volume increased due to elevated erythropoietin seen after 8 weeks gestation*
What is the average blood loss for a vaginal deliver versus blood loss for an uncomplicated C/S?
- vag(500 ml)
- C/S(800-1000 ml)
What are 5 anesthetic implications of CV and hematologic changes associated with the pregnant patient?
- beware of platelet countsprior to placing epidural know hospital policy
- –>acute drops?s/S of low platelets? increased risk of an epidural hematoma? - investigate elevated WBC
- –>3rd trimester ~10500 mm, in labor ~20-30K mm - Left uterine displacement(beware supine)
- be prepared for massive blood loss
- at term pseudocholinesterase activity is decreased 30%
Parturient request epidural placement. Upon inspection of CBC, WBC reflects a level of 12,500 mm^3. The next most appropriate action is to:
a. redraw the CBC
b. accept as normal for this population and proceed
c. reject as normal for this population and decline service
d. both a and c
accept as normal for this population and proceed
List 8 respiratory changes for the pregnant patient.
- capillary engorgement in upper airway
- O2 consumption increases 33% at rest and 100% during 2nd stage of labor
- MV increased 50%(breathing for two)
- VT increases 40%
- FRC decreases 20%
- arterial PaO2 decreases slightly due to fall in PaO2
- HCO3- levels decrease 4 meq/L to keep pH in normal range b/c of the respiratory alkalosis
- upward pressure of diaphragm
What are some issues related to capillary engorgement in the upper airway?
- narrowed glottic opening
- edema in nasal and oral pharynx, larynx and trachea
- Mallampati score changes as labor progresses
- friable tissue(bleeds really easy secondary to capillary engorgement)
What are some issues related to the upward pressure of the diaphragm? Expiratory Reserve Volume: Residual Volume: Vital Capacity: Flow volume loops:
Mimics Restrictive Lung Disease
ERV=decreased ~20%
RV=decreased ~15-20%
VC=unchanged
Flow volume loops=unchanged
Intubating the Parturient:
- avoid nasal manipulation(capillary engorgement in upper airway)
- 6.5-7.0 ORAL ETT recommended
- may consider having a short-handled laryngoscope to navigate enlarged breast
- optimize ALL airway circumstances: “take her to the prom”
- get help
Anesthetic Implications in the Parturient:
- maternal PaCO2 at term?
- Increased MV during contraction leads to?
- Preoxygenate?
- ~32 mmHg
- maternal hypocarbia(PaCO2 ~32/PH > 7.55)
- –>this can lead to uteroplacental vasoconstriction, decreased respiratory drive-hypoxia and lethergy
- MUST ADEQUATELY PREOXYGENATE secondary to decreased oxygen reserves, increased oxygen consumption and decreased FRC
Rapid desaturation during induction!!!
Beginning in 1st trimester women have _____ sensitivity of LA and general anesthetics. They also require ____ MAC of inhalational drugs…why?
- increased
- decreased
- endogenous opiates and progesterone
Why are decreased LA dosages needed in the Parturient?
- increase in sensitivity of nerves to LA
- distended epidural venous plexus
- increased epidural blood volume
- increased pressure within epidural space
- decreased volumes of both epidural and subarachnoid spaces
so VOLUME VOLUME VOLUME with epidurals!!!
All this lead to potential for increased block height
Due to elevations in the parturient’s sympathetic outflow, which of the following cardiac parameters occur at term?
a. increased CVP
b. decreased SVR
c. decreased LVESV
d. decreased EF
decreased SVR
What are 4 spinal/epidural implications for the Parturient?
- enhanced cephalic spread of LA
- PDPH mor common(cause of dilated vertebral spaces)
- Intravenous epidural catheter threading more likely(descended veins)
- LA requirement decreased ~30%
What are the GI changes of Parturient?
- gastric reflex/heartburn/esophagitis(what % have):
- gastric motility?
- food absorption?
- gastric pressure?
- esophageal sphincter tone?
- gastric volumes(>25ml)?
- gastric pH(
- ~30 to 70%
- decreased gastric motility
- decreased food absorption
- increased gastric pressure
- decreased esophageal sphincter tone
- increased gastric volumes(>25mls)
- decreased gastric pH(
GI anesthesia implications:(3)
- > 12 weeks gestation=RSI with cricoid
- strict NPO for elective procedures
- 4-5xhigher risk of aspiration
What precautions to take in cause of aspiration and treatment for?
- Sodium citrate is most useful agent in raising gastric pH before induction of GA prior to C/S
- If aspirates..initiate 100% ox and PEEP
- prevent Mendelson’s syndrome
- –>pHgastric vol > 25 ml(admin hypermotility agent=metoclopramide)
What are the hepatic changes associated with pregnancy?
- LFTs increase to upper limits of NORMAL
- Decreased albumin(increased free-fraction of protein bound drugs)
- subclinical pseudocholinesterase deficiency
- –>serum cholinesterase activity decreases 30% so give less succ
Renal changes:
- kidney size?
- ureters and renal pelves…..?
- renal plasma flow?
- GFR?
- creatine clearance?
- BUN?
- serum creatinine?
- Glucose resorptive capacity of the proximal tubules?
- kidneys enlarge and return to pre-pregnant size by 6 months postpartum
- ureters and renal pelves dilate by the end of first trimester due to hormonal changes
- renal plasma flow increases 75-85%
- GFR increases 50%
- Creatinine clearance increases
- BUN decreases
- serum creatinine {} falls
- glucose resorptive capacity of the proximal tubules decreases
Uterine blood flow:
- Supplied by?
- What % of CO and how many ml/min?
- O2 and CO2 are ___ limited?
- Decreased UA blood flow or increased placental vascular resistance =?
- How does volatiles affect UBF?
- supplied by 2 uterine arteries
- 10 of CO and 700-800 ml/min
- –>150ml/min ~ myometrium
- –>100ml/min ~ decidua
- –>remainder ~ intervillous space
- “perfusion limited”(by blood pressure)
- decreased fetal O2
- UBF: unchanged on 0.5-1.5 MAC w/ all VA
What 4 factors decrease uterine arterial pressure?
- supine position
- hemorrhage/hypovolemia
- drug induced hypotension
- hypotension during sympathetic blockade
What 4 factors increase uterine venous pressure?
- vena caval contraction
- uterine contractions
- drug induced uterine hypertonus(oxytocin, LA)
- skeletal muscle hypertonus(seizures, valsalva)
Factors causing decreased UBF secondary to increased uterine vascular resistance?
- endogenous vasoconstrictors
- –>catecholamines(stress)
- –>vasopressin(in response to hypovolemia) - exogenous vasoconstrictors
- –>epinephrine
- –>vasopressors(phenylephrine>ephedrine)
- –>LA(high concentrations)
Placental transfer and fetal effects of drugs is dependent upon(diffusion)? 5 things?
- magnitude of {} gradient
- molecular weight(smaller substances pass through easier)
- lipid solubility
- state of ionization
- maternal protein binding
What are the fetal:maternal ratios of these drugs?
- morphine
- vecuronium
- glycopyrrolate
- labetalol
- ephedrine
- diazepam
- metoprolol
- morphine 0.61
- vecuronium 0.07
- glycopyrrolate 0.22
- labetalol 0.38
- ephedrine 0.7
- diazepam 1.0
- metoprolol 1.0
(baby gets the same amount as mother 1mg/1mg)
Describe what characterizes the three stages of labor
- 1st Stage of Labor: onset of cervical dilation to complete cervical dilation(10 cm)
- 2nd Stage of Labor: delivery of the fetus
- 3rd Stage of Labor: expulsion of placenta
The time is takes to progress through these stages is dependent upon: parity, effective uterine contractions, size of pelvis, type of pelvis and fetal presentation
What is meant by the terms gravida and para?
gravida = # of pregnancies para = # of fetus carried to a viability(20 weeks or longer)
1st Stage of Labor pain is a result of, mediated by and described as what?
- primary result of cervical distention, stretching of lower uterine segment and myometrial ischemia
- mediated by T10-L1 visceral C fibers(so this is the level that should be blocked by a regional block.)
- described as non-localized aching, dull and cramping
2nd Stage of Labor pain begins when, is mediated by and is described how?
- begins when cervical dilation is complete and presenting part descends into pelvis
- pain impulses carried by somatic nerves via Pudendal nerves…mediated by S2, S3, S4 in addition to T10-L1
- –>LA induced lumbar epidural block provides complete anesthesia for BOTH 1st and 2nd stage of labor pain
- sharp pain, fast pain…..a delta fibers
pain medication affects mothers ability to deliver fetus…25g spinal with sufenta or 25 mcg fentanyl can help…for a vaginal birth the spinal/epidural must be blocked at T10 down(so the umbilicus down)
The first stage of labor has two phases. What are these two phases and the characteristics of them both?
- The first stage of labor consists of cervical effacement and dilation*
- Latent Phase: defined as onset of labor- point at which cervix begins to rapidly change
- Active Phase: begins at 2-3 cm dilation. Cervix undergoes max rate of dilation ~ 1-1.2 cm/hr.
When labor ceases to follow this pattern, it is said to be “dysfunctional”
What is the most readily available method for assessing fetal condition?
- Fetal heart rate monitoring
- it is not a specific predictor of feta well-being
- FHR reveals info pertaining to anesthetic intervention
Overall FHR predicts baseline status
How does the Fetal heart rate monitor work?
- FHR recorded on a graph running 3cm/min
- uterine tone or pressure recorded concurrently on second channel below FHR tracing
- non invasive tracing(abd U/S) or invasive(scalp electrode)
- invasive embedded 2 mm and requires ROM with partially dilated cervix
Fetal oxygenation is limited mostly by what? Decreases in maternal BP or uterine artery blood flow also decreases what?
- by uteroplacental blood flow, NOT maternal oxygenation
- uteroplacental blood flow
responsible for decels
What is the normal FHR, what characterizes brady/tachy and the causes of both?
- normal FHR is 110 - 160
- Brady(FHR
The number 1 reason for a brady FHR is?
a paracervical block
What is the single best indicator of fetal well-being and indicates adequate fetal oxygen reserve?
FHR variability
What does variability represent and what are the descriptive terms used to describe variablity?
- variability represent an intact central nervous system and normal cardiac function
- variability descriptors: absent, minimal(25bpm)
What is the ideal FHR variability?
moderate(6-25bpm)
What are some causes of FHR variability?
Causes of CNS depression, hence decreased variability: hypoxia, fetal sleep, acidosis, anencephaly, drugs(CNS depressants, autonomic agents, magnesium, and opioids), and defects in fetal cardiac conduction system
FHR variability increases with…….?
advancing gestational age
What are some causes of decreased variability?
hypoxia, fetal sleep, acidosis, anencephaly, drugs(CNS depressants), fetal heart defects
On the FHR monitor, absent variability is characterized by……?
a “smooth line”
On the FHR monitor, minimal variability is characterized by……?
On the FHR monitor, moderate variability is characterized by……?
6 - 25 bpm around baseline
On the FHR monitor, marked variability is characterized by……?
> 25 bpm variation around baseline
each line is 10 bpm
What are accelerations, when do they occur and what is meant when the FHR pattern is said to be reactive?
- abrupt increases in FHR above baseline
- occur in response to fetal movement and indicate adequate oxygenation
- FHR is said to be REACTIVE when there are 2 or more accelerations in a 20 min period
Decelerations are NOT normal and are classified as early, variable and late. Describe each classification of decels:
EARLY DECELERATIONS:
- occur in concert with uterine contractions
- begins when contractions begins and returns to baseline when contraction ends
VARIABLE DECELERATIONS:
- sudden decrease in FHR that occurs irrespective of uterine contraction
- may occur in response to Umbilical Cord Compression
- abrupt onset to nadir = 15 secs/ 30 seconds after peak contraction
- onset, nadir and recovery of decal follow beginning, peak and end of contraction
- flip the patient, place them on oxygen, possible fluid bolus, call the OB
If FHR recording during pre anesthesia assessment suggest hypoxia……
- exercise caution in deciding to proceed with neuraxial analgesia
- –>check severity of fetal hypoxia(variability and decals)
- –>sympathectomy secondary to epidural or spinal may worsen fetal condition
What are some anesthetic considerations for Intrauterine resuscitation in the presence of a non reassuring FHT?
- changing maternal position
- rapid infusion of IV fluids
- discontinuing oxytocin
- maternal O2 delivery
- if hypotensive, delivery of vasopressors
- use of tocolytic agents
Factors to ponder when considering anesthetic technique:
- cervical dilation and effacement
- parity
- labor pattern
- fetal well being and tolerance to labor
- OB assessment with accompanying RED FLAGS
- patient’s desire or willingness to receive anesthetic
What to do when confronted with a non-reassuring FHR tracing:
- call for help
- turn LUD, RUD or on all fours
- administer O2
- consider adjusting or stopping epidural infusion
- assess vital signs
- fluid bolus??
- OB/RN may stimulate fetal scalp, adjust or stop Piton, assess MgSO4, call an emergency C/S
