EXAM 3 Review Flashcards
In the liver, blood flow through the
DUCTUS VENOSUS
When Ductus Venosus closes remnant is
LIGAMENTUM VENOSUS
Foramen Ovale closes and becomes the
FOSSA OVALIS
When Ductus Arteriosus closes it becomes
LIGAMENTUM ARTERIOSUM
DUCTUS venosus shunt is
LIVER
Foramen ovale shunt is
Right atrium to left atrium
Ducturs arteriosus shunt is CONNECTION between
Pulmonary artery to AORTA
Fetal blood Oxyhemoglobin dissociation curve
↓ 2,3 DPG, shift to the left (Left for LOVE of oxygen) increased affinity for oxygen (hold on to oxygen)
Womb approx hgb
15g/dL
Fetal PO2 max is
50-60mmhg
Fetal blood and CO2 relationship
less affinity for CO2
Highest possible baby SPO2 is
90%
For a PaO2 of 60 what is the SPO2 approx?
90%
For a PaO2 of 50, what is the SPO2 approx?
80%
In the fetal circulation, Hgb binding is (increased/decreased)
Increased
Parallel circuit in the fetal circulation
Both right and left venticles provide systemic blood flow
In fetal circulation, PVR is
High
In fetal Circulation, SVR is
Low
What is the ratio of R to left contribution in fetal circulation
2:1 Right to left ration
Right is 2x LV output because of R to L shunt
The ductus venosus receives blood
Inferior vena cava coming from lower extremities
Where does the first admixture occur
in the Ductus venous in the liver
The presence of which structure makes the SVR low in the fetal circulation?
Placenta
Immediately after delivery, the removal of the placenta leads to what changes?
ELEVATED SVR
Most of the oxygenated blood in fetal circulation comes from ?
UMBILICAL VEIN from PLACENTA
Where does blood/ nutrients exchange occur?
In the INTERVILLOUS SPACE
Explain blood flow in fetal circulation
Path of oxygenated blood from placenta
- OXYGENATED: From placenta, blood flow through umbilical vein which separates into 2 branches (one is portal vein, the other is DUCTUS VENOSUS, which join the IVC
- The blood bypasses the liver, goes through the Ductus venosus into the IVC
- Blood enters RA
- Goes from RA through FORAMEN OVALE to LA
- From LA to LV
- From LV to proximal aorta then supplied to the coronaries and Head vessels and upper torso
Fetal blood in the
Chorionic villi
What are the 4 shunts
Ductus Venosus :
Foramen Ovale : right atrium to Left atrium
Ductus Arteriosus: pulmonary artery to Aorta
What are the 4 shunts
Ductus Venosus : Joins IVC blood, blood bypasses liver
Foramen Ovale : right atrium to Left atrium
Ductus Arteriosus: pulmonary artery to Aorta
Placenta
Path of UNOXYGENATED blood in fetal circulation
- flow directly from Superior vena cava to tricuspid to Right ventricle
- From RV to Pulmonary artery
Path of UNOXYGENATED blood in fetal circulation( blood from body)
- flow directly from Superior vena cava to tricuspid to Right ventricle
- From RV to Pulmonary artery
- Because lungs not inflated , and PVR is high, most of the DEOXYGENATED blood return to AORTA via the DUCTUS ARTERIOSUS
- Then from the aorta FLOW to UMBILICAL ARTERIES
- FROM UMBILICAL ARTERIES back to PLACENTA
What maintains DA potency ?
Prostaglandings
How can hypoxemia leads to PDA?
Hypoxemia will release endothelial nitric oxide which will results in vasoilation, may OPEN PDA after closure
What medication is given to attempt to close PDA?
Indomethacin (blocks PGE1, prostaglandins)
Functional closure of shunt happens
Immediately after birth
What causes the dramatic increase in SVR in postnatal circulation ?
Removal of placenta
What causes the dramatic decrease in PVR in postnatal circulation?
INFLATION of the lungs with the first breath
What pressure must be generated to fully expand lungs
40-60 cm H2O
In maternal circulation what is the direction of the Oxyhemoglobin curve?
↑ 2,3 DPG, Shift to the Right ( R- for RELEASE O2) lower O2 affinity)
Foramen ovale in fetal circulation closes due to
Increase in LVEDP (Left ventricle End diatole Pressure)
Functional closure of shunt happens
immediately
Does mother and Baby blood ever mix?
No
90 % of placental blood flow through which structures
Intervillous space
Properties that facilitate placental transfer
High lipid solubility
Low molecular weight
Lipophillic
CO2 is present in the form of ? Give percentage
62% of CO2 is in the form of BICARBONATE (HCO3-)
Placental O2 consumption rate
8ml/min/kg of FETAL WEIGHT
Efficiency of placenta compared to lungs
1/5th the efficiency of adult lung
The Placenta is supplied by 2 arteries which are
UTERINE and OVARIAN arteries
Uterine blood flow is
Directly proportional to the fetal umbilical venous partial pressure of O2
These arteries may bleed after placental removal
Spiral arteries
What can worsen spiral arteries bleeding after removal of placenta?
Nitrous oxide
Connect placenta to uterus
Spiral arteries
Uterine blood flow formula
Uterine arterial- venous pressure / Uterine Vascular resistance
Perfusion pressure relationship with Uterine Blood flow
Direct relationship (as one increases, the other increases)
Vascular resistance and Uterine Blood flow
INVERSE PROPORTIONAL relationship (as VR increases, UBF decreases vice versa)
2 main determinants of UBF
Perfusion pressure and vascular resistance
UBF at term is
> 700-900 ml/min
Uterine blood vessels are _________to vasopressors than systemic blood vessels
More sensitive
Vasodilators that may dilate uterine vessels
Nitrous oxide
PGE (prostanglandins)
What is altered in pregnancy as vasoconstriction?
Hypertensive response to IV epinephrine, phenylephrine and Angiotensin II is diminished
This receptor altered in pregnancy
Altered receptor mediated G-protein coupling
Placental transfer requiring ATP (2)
Active transport
Pinocytosis
Placental transfer NOT REQUIRING ATP
Passive transport
Facilitated transport
Placental transfer is LIMITED To
FLOW
Placental transfer is not limited to
diffusion
Placental transfer : passive transport driven by (COMLDM)
Concentration gradient Occurs via membrane or protein Molecular weight Lipid solubilty Degree of ionization Membrane surface area
Passive process requiring carrier protein
Facilitated transport
Determinants of ACUTE changes in UBF are
Systemic Blood pressure
Uterine venous pressure
Uterine Vascular resistance
The 3 Determinants of ACUTE changes in UBF are
Systemic Blood pressure
Uterine venous pressure
Uterine Vascular resistance
Best positions for UBF
Prone- best (i.e on all four extremities)
Left LATERAL TILT
Worst position for UBF
SUPINE
Why is supine position worse for the pregnant female?
AORTAL CAVAL Compression: Gravid uterus sitting on top of major vessels, decreases preload and venous return which decreases CO and lead to hypotension
HYPOTENSION in pregnant ladies associated with
VOMITING
Which medication can be given IM to prevent vomiting
EPHEDRINE IM 50mg
These 2 hormones increases vascular resistance leading to decrease perfusion
Vasopressin
Angiotensin II
Factors that decrease UTERINE arterial presure
Supine position
Hemorrhage/ hypotension
Drug induced hypotension
Hypotension during sympathetic Blockade
Factors that increase UTERINE PRESSURE
Venal caval compression
UTERINE CONTRACTION
Drug induced uterine hypertonus (oxytocin, cocaine)
Skeletal muscle hypertonous
Most common cause of UTERINE PRESSURE increase is
Uterine contractions
2 major thing in summary decreasing perfusion pressure
Decrease Arterial pressure
Increase uterine venous pressure
Causes of Decrease uterine Blood flow
- Endogenous vasoconstrictors (catecholamines, vasopressin)
2. Exogenous Vasoconstrictors ( Phenylephrine> ephedrine) high concentrations of local anesthetics
Uterine blood flow if often reduce clinically (P-DUE) 4 factors
Position
Drug induced HYPOTENSION
UTERINE CONTRACTIONS and PUSHING EFFORTS
Endogenous and Exogenous vasoconstrictors
PaO2 of 60 gives SPO2 of
90
Diffusion rate of O2 vs CO2
CO2 has a high diffusion capacity, 20x greater than O2
Progesterone in pregnancy direct effect
Dilation of airways
***Progesterone on CO2
Increased sensitivity of CENTRAL CHEMORECEPTORS to CO2
Progesterone in pregancy indirect effect
Enhances B2 agonist activity
**Progesterone and MAC
It decreases MAC requirement by 30 %
If progesterone decreases MAC by 30%, if the MAC is 1.4 what would be the new MAC?
1.4 (0.30) = 0.42 so 1.4-0.42 = 0.98
Hormonal changes due to 4 main hormones (PECR)
Progesterone
Estrogen
Cortison
Relaxin
Action of Cortison and Relaxin
Dilates airways
Pregnancy and Estrogen
High local ESTROGEN leads to a DIMINISHED in activity of KEY intracellular enzymes that mediate vasconstriction
Plasma volume changes secondary to hormones
Increases due Progesterone and Estrogen
Progesterone and GI
Esophageal peristalsis/intestinal transit are slowed
due to Progesterone
_____And _______ are minimally affected if at all?
Gastric acid content and plasma gastrin levels
Progesterone on Kidneys and ureters
Kidneys enlarge and the ureters/renal pelvis dilate
Kidneys enlarged due to
Progesterone
Ureter and renal pelvis dilate due to
Progesterone
Estrogen increases ____% which leads to ______
What other thing causes renin release beside Estrogen?
100%; renin releases from juxtaglomerular cells of nephron cleave angiotensinogen
Sympathetic input
Pregnancy induced ↑ forgetfulness due to
Progesterone
Alveolar anesthetic concentrations rise fastersecondary to
- ↑ MV
* ↓ FRC
Progesterone increases by _____% which leads to _________
Increase aldosterone levels
2 Actions of aldosterone
Increase sodium and water reabsorption by nephron collecting duct →Increase effective blood volume to correct initial stimulus to the system
Vicious cycle of persistent Fetal circulation (HPIR)
- hypoxia/hypercabnia/acidosis/ cold
- Pulmonary vasoconstriction
- Increased pulmonary vasoconstriction
- RIGHT TO LEFT SHUNTING of BLOOD
Back to number 1.. vicious cycle