EXAM 3: Fetal Circulation Flashcards
Parallel circuit
Both right and left ventricles provide systemic blood flow
Admixture blood
oxygenated with deoxygenated blood
PVR is because
High ; clamped down fluid filled
SVR is________
low
Placenta makes
SVR stay low
Right to left shunt
Right heart bypass lungs
Blood comes from the __________to the placenta
UMBILICAL VEIN Ductus venosus
The ductus venosus joined with
Inferior vena cava , and blood coming from LE
The ductus arteriosus
2nd place of shunting Right to left , bypass lung
Fetal circulation Right vs LEFT
RV output 2x that of left
Ratio of PVR to SVR
2:1 Right to left ratio
When placenta is removed
SPINAL ARTERY starts bleeding Uterus start Contracting stop mechanically from bleeding
Anesthesia Gases do what to the uterus
Relaxes uterus; may increase bleeding of spinal arteries after placenta has been cut off run MAC less percentage
INTERVILLUS SPACE Does mother and fetus blood mix? Thin membrane allows
where blood exchange happens Blood of fetus and mother’s blood DONT MIX passage of nutrients
RH factor relevant
Rh factor relevant in 2nd pregnancy
****Uteroplacental Perfusion: Originates from
the uterine and ovarian arteries
Blood flow to intervillous space
Maternal blood enters the basal plate of the placenta into the intervillous space • Nutrient exchange occurs with fetal blood coursing through the villi
2 circulations separate
• Normally, the two circulations are separate with no mixing
Uterine blood flow increases___ Prepreg. Level Pregnant _______ml at term
dramatically 50-100 ml/min PREGNANT 700-900ml min at term
Cardiac output to uterus increase from ______to ________
5% to approx 12% at term within the uterus , approxi 90% of blood flow is to the iNTERVILLOUS SPACE>
• Hemodynamic changes are result of_______ • Generalized systemic reduction in sensitivity to_______
-altered vascular responsiveness to endogenous vasoactive substances -vasoconstrictors during pregnancy
Uterine vascular responsiveness to vasoconstrictors What happens in PRE-ECLAMPSIA
• ↓ (meaning BP shouldn’t be higher than normal) Mother who developed preeclampsia lack the systemic reduction in sensitivity to catecholamines. LACK of refractoriness to resistance –> HTN
Uterine vessels are more sensitive to____________
alpha agonists than systemic vessels in general • More uterine vasoconstriction (increase vascular tone of mother, baby does worse, HR decelerates)
Changes in vascular reactivity during pregnancy may be due to:
• Altered receptor number and function (LESS) • Altered metabolism and clearance of drugs (increase BV) • Altered release of endogenous vasodilators or constrictors • Altered sensitivity to endogenous vasodilators (PGE2 and NO) or constrictors
Decrease sensitivity
to alpha agonist , EPINEPRHINE Phenylephrine and ANGIOTENSIN II more pronounce to uterus
Avoid hypotension in pregnant, you want to decrease BP but not too much to
cutting off the circulation of uterine blood flow
Enhanced release of vasodilators by vascular endothelium
Prostacyclin (PGI2) • Nitric Oxide (NO)
IMPORTANT there is alteration in which receptor?
Altered receptor mediated G-protein Most drugs work through GPCR
Determinants of Uterine Blood Flow
• U.B.F. is related to perfusion pressure and vascular resistance
UBF= Formula
uterine artery - uterine venous pressure/ uterine vascular resistance
U.B.F. will _____whenever perfusion pressure _______or uterine vascular resistance_________
↓ ↓ ↑
UBF and perfusion pressure
Direct relationship
UBF and uterine vascular resistane
Inverse
No supine
LEFT LATERAL TILT INSTEAD HEMODYNAMICALLY STABLE THERE IS DECREASED VENOUS RETURN, Decrease CO, decrease hypotension
FIRST SIGN OF HYPOTENSION
VOMITING
↓ Perfusion Pressure
▪ ↓ Uterine Arterial Pressure ▪ Supine position ▪ Hemorrhage/hypovolemia ▪ Drug-induced hypotension ▪ Hypotension during sympathetic blockade
Uterine Blood flow decreases when Vascular resistance increases
▪ ↓ Uterine Arterial Pressure ▪ Supine position ▪ Hemorrhage/hypovolemia ▪ Drug-induced hypotension ▪ Hypotension during sympathetic blockade
▪ ↑ Uterine Venous Pressure (VUDS) MOST COMMON Is
▪ Vena caval compression ▪ Uterine contractions MOST COMMON is ▪ Drug-induced uterine hypertonous (oxytocin, cocaine) ▪ Skeletal muscle hypertonous
THOSE things increase Vascular resistance
VASOPRESSIN ANGIOTENSIN II
Endogenous Vasoconstrictors (2) Prevent constriction (2)
Catecholamines Vasopressin Nitrous oxide , PGE2
Exogenous vasoconstrictors
Epinephrine ▪ Vasopressors (phenylepherine > ephedrine) ▪ Local Anesthetics (high concentrations)
The determinants of acute changes in uterine blood flow are
• systemic blood pressure • uterine venous pressure • uterine vascular resistance
Worst position
SUPINE
BEST POSITION
Left Lateral TILT
Position
Prone or ALL four positions
• Uterine blood flow if often reduced clinically
• Position • Drug induced hypotension • Uterine contractions and pushing efforts • Endogenous and exogenous vasoconstrictors
• Passive Transport-driven by DOES IT require energy ? what is mediated by ?
• Concentration gradients & electrochemical differences • Molecular weight • Lipid solubility • Degree of ionization • Membrane surface area/thickness. *** No use of cellular energy. Occurs thru lipid membrane or via protein channels
Facilitated Transport- Does it require ENERGY
• Intermembrane protein carriers move lipid-insoluble molecules down a concentration gradient (ie; glucose); no , just protein carrier
Active Transport DOES it require energy? Example
-movement of a substance against a gradient and across a cell membrane linked to cellular metabolic activity (energy) and a protein carrier; (ex: Na+/K+ ATPase pump)
• Pinocytosis Does it require energy ?
PLACENTA engorges -large protein macromolecules surrounded by membrane vesicles and moved through the cytoplasm to opposite membrane wall; requires cell energy
Fetal PO2 max is _____Why?
50-60 mmHg; because 1/5 the efficiency of the adult lung
CO2 is in the form of
Bicarbonate
Large partial pressure difference between Driven by O2 partial pressure difference between
Maternal and fetal blood
• Placenta transfers O2 for fetal growth/development Limited to ____not ______
• ~8 ml O2/min/kg fetal weight • Transfer is limited to flow not diffusion
Fetal Hgb has More affinity or less affinity ?
decreased levels of 2,3-DPG increasing O2 affinity
• Fetal PO2 max is 50-60 mmHg due to
Placenta being a venous equilibrator • Placenta’s high O2 consumption rate • Mixture of oxygenated umbilical blood and deoxygenated inferior vena caval blood from fetal lower extremitie
• Fetal PO2 max is 50-60 mmHg due to The mixture of _______ and __________ from _________ Which shunt mix Oxygenated UMBILICAL BLOOD AND Deoxygenated IVC blood from fetal lower ?
Placenta being a venous equilibrator (what’s in venous is also same in arterial) • Placenta’s high O2 consumption rate • Mixture of oxygenated umbilical blood and deoxygenated inferior vena caval blood from fetal lower extremities DUCTUS VENOUS
CO2 is present in many forms in the blood CO2 is present in THE PLACENTA predominantly in the _______form
• Dissolved CO2 ~8% • H2CO3carbonic acid • CO3- Carbonate ion • HCO3 (bicarb) ~62% are the predominant forms involved in placental transfer
• Large partial pressure difference
between fetal-maternal blood driving transfer
• CO2 has a
high diffusion capacity; 20X greater than that of O2
• Inaccessibility of the placenta and maternal/fetal
safety concerns limit direct human studies
Data is a one time measurement; influenced by
metabolism and changes at delivery
• Pharmacokinetic factors
(lipid solubitlity, protein/tissue binding, pKa, fetal bld pH, and blood flow) also affect drug transfer
Data reported as
FETAL to MATERNAL RATIO
• Inhalation agents commonly used as maintenance during
c-section under GA
Halogenated agents have
high lipid solubility and low molecular weight facilitating placental transfer; F/M ratios of 0.6-0.9; may see low Apgar scores such as isoflurane
• Nitrous also rapidly crosses within
3 minutes; may see neonatal depression and diffusion hypoxia can occur; supplemental O2 a must
• Lipophyllic nature enhances placental transfer • Thiopental, methohexital, ketamine, propofol, etomidate, diazepam and midazolam have been studied, they are all ______; enhances •will Ketamine affect baby HIGH FM ratio for_____________+ _________
All show rapid transfer to fetus with high F/M ratios (> 0.5) and may lower the 1 and 5 minute Apgar scores Lipophillic; Yes , FM is 1.6 crosses placenta Diazepam + midazolam
• A mainstay of pain relief in obstetrics
OPIOIDS
• Epidural/intrathecal administration limits s
Systemic levels and fetal transfer; less neonatal depression
OPIOIDS SHOULD GO
EPIDURAL (Same as IV dose for fentanyl) SPINAL or subarachnoid
IV administration of opiods
rapid transfer and neonatal cause ventilation depression
Demerol used for
Shivering Associated with neonatal depression RAPid administration will be 1 in about 2-3 hours
LOCAL anesthetics (GOOD) what enhances transfer as far as molecular weight, degree of ionization and lipid solubility What SLOWS protein binding?
• Commonly used in labor for analgesia • Route of administration effects maternal blood levels and placental transfer • Low molecular weight, low degree of ionization and high lipid solubility enhance transfer • Protein binding slows transfer; bupivacaine is highly protein bound; lidocaine is less protein bound
EPIDURAL REMOVED Epidural and IV dose of fentanyl
MOM needs medications Same
Requires more volume (Epidural vs spinal) EPIDURAL limits
EPIDURAL systemic levels and fetal transfer , less neonatal depression
Differentiate : LIDOCAINE vs BUPIVACAINE
BUPIVACAINE and lidocaine Bupivacaine is HIGHLY PROTEIN bound and Lidocaine is LOW PROTEIN BOUND Faster onset and offset : Lidocaine BUPIVACAINE –> Last LONGER but slower onset. F/M ratio is low
Duramorph to spinal can cause________ monitor for-______
APNEA monitor for 24 hours
LIke lidocaine
MEPIVACAINE
• Animal studies have shown neonate
Less sensitive to CNS/cardiotoxic effects; felt due to larger volume of distribution
• Little direct effect on fetal heart rate; FHR changes Exception : ______Causes less _______
most often due to indirect factors such as maternal hypotension or uterine hyperstimulation; exception may be paracervical block (LESS MATERNAL STIMULATION)
• Minor transient effects on neurobehavioral tests; other
factors more important than choice of LA
• Little direct effect on fetal heart rate; FHR changes
most often due to indirect factors such as maternal hypotension or uterine hyperstimulation; exception may be para-cervical block
Glycopyrrolate does not cross
DO NOT CROSS BARRIER Do not affect neonate
Fully ionized quaternary ammonium salts
• do not readily cross the placenta • rarely effect neonatal muscle tone
• Succinylcholine undetectable after single dose
• repeated high doses (>300 mg) may cause neonatal muscular block or if neonatal pseudocholinesterase deficiency present
• Non-depolarizers F/M is •
LOW F/M concentrations may increase over time • little concern during c-section
You can do this agent with low F/M
Rocuronium in a patient
During C-section, surgeon stated abdomen is tight, already given succ or rocc what to do next?
Give more gases Hypotension , relaxing too much you’re in trouble too
Glycopyrrolate is
poorly transferrd low F/M ratio
Quarternary ammonium
Anticholinesterases NEOSTIGMINE Ionized physiologic pH(limited placental transfer but detectable levels found in umbilical blood) May cause bradycardia.
FetaL lungs are
STAGNANT (not usef for oxygenation) FLUID FILLED High PAP 70/45 normal 15-20
Shunt
Foramen ovale (RA to LA) Ductus arteriosus (Pulmonary artery to Aorta) Ductus venosus (in liver, mix with LE and IVC) Placenta
Lowest site of SVR
Does not completly oxygenate blood Greatest saturation is 70-80% Connected with
Fetal renal function
Low RBF and Low GFR stagnant organ low SVR High Renal vascular resistane Low Permeability of Glomerular Capillaries Small Size and Number of Glomeruli (things not diffuse easily)
Adaptive Alterations•e • Nml 15 g/dL
• ↑ 2,3-diphosphoglycerate (2,3-DPG) ↑ Hemoglobin-binding • Less affinity for carbon dioxide
Normal hemoglobin inside of womb is
15g/dL
PaO2
30-35
Hgb shift to the
LEFT relative to adult curve
HgF
higher affinity of oxygen
2,3 DPG produces in
Higher concentration in placenta
Transitional circulaton
first breath–> Fluid filled to air filled , vaginal deliver squeeze fluids and lymphatics drain that fluid
What negative pressure must be generated
40-60 cm H2O
Surface tension
surfactant help
Within 5-10 min what happen
Normal TV Lung expansion
When is FRC normalized
within 1 hour and stabilized ABG
PO2 of 60 = 90 SPO2, For a PO2 of 50
about 80
With a PO2 of 70
about 100 SPO2
Know
SHUNT, direction of blood flow,
Changes at right Ventricle
Dcrease afterload Decrease pulmonary vascular resistance DUCTAL CLOSURE Volume decrease ELiminated vein return Output diminished 25%
Changes at left Ventricle
Increase afterload Placenta ELIMINATE SHOrtly after lungs expand DUCTAL CLOSURE Increase volume output nearly greater than 50% Transient LEFT TO RIGHT SHUNT
PLACENTA is a shunt
NEED TO DISPLACE OR REMOVE FOR CPR
Left ventricle increases performance
Catecholamines increase
PVR goes from
Constriction to dilation RV wall thickness decrease
Foramen Olvee
Closes due to INCREASE in LVEDP and left atrial pressure
Once closes it’s
FOSSA OVALIS
% percentage with patent FO
25-50% of adults
Anesthesia considerations
Leads to right to left shunt under general anesthesia Significant cause of Persistant arterial despite 100% O2
if not enough pressure on the left you can get a
RIGHT TO LEFT SHUNT< causing arterial desaturation
Considerations for R to LEFT shunt, remove AIR
Right atrium, Right ventricle , lungs,
Ductus arteriosus becomes
Ligamentum arteriosum
Increase PO2 encourages
Closure
Given to patient with no closure
PGE1 blocker INDOMETHACIN
PDA
Failure to thrive Left to right shunt –> Increase PBF –> Volume overload
PDA shunt
oxygen right blood from aorta to pulmonary artery–> volume overload
PDA treatment
Depends on size (small one not treated) Lasix Digoxin (Increase Ca2) PDA closure device.
Ductus Venous turn into
Ligamentum Venosum
Ligementum Venousus CLOSES within Functionally Closes
Shunts blood from liver to IVC 50% or less Closes within 7 days when infant is born
CHANGES at birth Renal GFR ______ mature
similar to lung Arterial Pressure Increase Renal vascular resistance Increase GFR 3-4 days 70 % mature 1 month
Vicious cycle of persistent fetal circulation
Hypoxia/hypercabnia/acidosis/cold –> pulmonary vasoconstriction –> Increase PVR –> R to left shunt (open FO)
Persistent Pulmonary Hypertension
Elevated PVR to point blood is shunted fetal cardiac channels Systemic arterial hypoxemia
Treatment PPH
Treatment • Depends on Severity • Surfactant • Ventilation Techniques • Nitric Oxide • ECMO
Nitrous Oxide
Pulmonary vasculature resistance
Uterine blood flow is ________proportional to fetal umbilical venous partial pressure of O2
DIRECTLY
Venous partial pressure may affected by drugs
May increase or decrease resistance in placenta
RA to LA shunting is through _______and bring oxygen to
Foramen Ovale; Cerebral circulation
Spiral arteries will bleed after placenta is removed, body will try to
Constrict
Mother’s blood into
INTERVILLOUS SPACE
Baby’s blood into
VILLI
Connection between Aorta and pulmonary artery
Ductus Arteriosus ( DA)
Nitrous oxide can make spinal arteries bleeding
worse, more vasodilation
Does vaginal arteries supply placenta
No
Placental septum is an
invagination of tissue
Uterine Blood flow Parallel
Placenta BLOOD FLOW
High Local _______ concentration lead to diminishes activity of key intracellular enzymes that mediate vasonconstriction
ESTROGEN:
Identify the FETAL SHUNTS and structure
A-Ductus Arteriosus
B- SVC
C- Pulmonary artery
D- Foramen Ovale
E- IVC
F- Ductus Venosus
G- IVC
H- Portal vein
I- UMBILICAL vein
J- UMBILICAL arteries
K - Descending Aorta
L- Pulmonary atery
M- Pulmonary Veins
