physiologic foundations Flashcards
biggest change for cardiovascular system
high flow (increased blood volume and cardiac output)
low resistance (vasodilation)
hematocrit levels for nonpregnant woman?
pregnant woman?
nonpregnant: Hct 38
pregnant: 34.7
what are Hgb and Hct levels for diagnosis of anemia during pregnancy
Hct <33
Hgb: <11
what masks the signs of hemorrhage during pregnancy
extra blood volume
*assess fetal HR first
most important assessment of CV system in pregnancy
cardiac output
-maintains moms bp and ensures profusion to placenta
baseline cardiac output L/min
6-7 L/min
what factors affect (increase) cardiac output
-b agonist drugs (terbutaline)
-twins
-sepsis
-labor
-exercise
-position (knee-chest and R are highest)
what is frank starlings law
-greater ventricles are stretched during diastole, the stronger the force of contraction during systole
(decreases cardiac output)
optimal HR range during pregnancy
40-140 bpm
3 determinants stroke volume
preload
afterload
contractility
volume; amount of blood in ventricle at end of diastole
preload
pressure; resistance that opposes ejection of blood from ventricles
afterload
how does pregnancy affect preload, afterload, contractility
preload: higher volume and flow
afterload: lower resistance
contractility:
sympathetic response to falling BP
-compensatory tachycardia
-vasoconstriction
-conservation blood volume (shunting)
-hyperglycemia
force of contraction of heart
contractility
how to increase preload
IV fluid bolus
positioning: keep her off back
how to decrease afterload
vasodilator/bp med if too high
positioning: keep her off back
how to increase contractility
increase preload
noninvasive assessment of cardiac output
-BP
-pulses
-breath sounds
-urine output
-heart sounds
-SaO2
-skin color, turgor
-temp
-LOC
-neck veins
-mucous membranes
meds that affect HR
chronotropes
meds that affect preload
diuretics (decreases)
volume expanders (increases)
meds that affect afterload
vasodilators (decreases)
vasoconstrictors (increases)
meds that affect contractility
inotropes (digoxin)
pulmonary physiologic alteration with pregnancy
compensated resp alk
if mom needs to be intubated what size would she need and why
6.5-7.0
because of edema and airway swelling with pregnancy
functional changes in oxygen with pregnant mom
-increased O2 consumption because increased metabolic rate
-increased tidal volume (how much you breathe in and out with breath)
-decreased functional residual capacity (amount air left in lungs after breathe out)
amount of air left in lungs after breathing out
functional residual capacity
how much you breathe in and out with each breath
tidal volume
nonpregnant blood gases (pH, O2, CO2, HCO3, b.d.)
pH: 7.35-7.45
O2: 90-100
CO2: 35-45
HCO3: 22-26
b.d.: -2
pregnant blood gases (pH, O2, CO2, HCO3, b.d.)
pH: 7.40-7.45
O2: 104-108
CO2: 27-32
HCO3: 18-22
b.d.: -3 to -4
what is SaO2 measuring
how is it measured
% hemoglobin molecules saturated by oxygen
pulse ox
what is PaO2 measuring
how is it measured
total oxygen content of blood
mmHg, blood gas
binding and unbinding of oxygen to Hgb
oxygen affinity (oxygen magnet)
(98-99% O2 bound to Hgb)
*ability of O2 to bind to and release from Hgb
*fetal oxygen affinity is greater than mom
product of PaO2 and cardiac output; oxygen sent to tissues
oxygen delivery
how does pregnancy affect oxygen dissociation curve
shifts right
*oxygen released more quickly from Hgb
*you always want fetal Hgb to be left of mom
how to assess oxygenation of baby during pregnancy
fetal heart rate patterns
major affect of renal system during pregnancy (2)
increased filtration
decreased reabsorption
anatomic changes renal system during pregnancy
-possible obstruction due to enlarging uterus
-dilation of urinary collection system (hydronephrosis, hydroureter)
-displacement bladder at term
-hyperemic (more blood flow)
normal glucose in urine during pregnancy
+1
possible complications renal system with pregnancy
-increased risk UTI
-increased risk pyelonephritis
-increased risk traumatic injury
functional changes renal system during pregnancy
-increased renal perfusion and GFR
-decreased reabsorption
-decreased: Cr, BUN, uric acid
-trace protein and +1 glucose in urine
what pulls fluid into blood vessels
colloid osmotic pressure (oncotic)
decreases with pregnancy
what pushes fluid out of blood vessels
hydrostatic pressure
increases with pregnancy
*causes edema
possible complication with fluid balance (r/t colloid osmotic pressure)
decreased colloid osmotic pressure
*increases risk pulmonary edema (especially postpartum, preeclampsia)
normal prepregnancy colloid osmotic pressure
COP = 25
major hematologic alteration in pregnancy
hypercoagulability
what causes hypercoagulability during pregnancy
increases clotting factors
decreased fibrinolytics
possible complication due to hypercoagulability with pregnancy
increased risk clot formation
triad of factors that increases risk clot formation
-venous stasis
-hypercoagulable blood
-endothelial injury (stirrups)
DVT prophylaxis
leg exercises
compression stockings
maybe use heparin
why is warfarin contraindicated during pregnancy
teratogenic
biggest risk with GI system alterations during pregnancy
increased risk aspiration
(stomach displaced, gastric emptying delayed, gastric secretions increased, lower esophageal sphincter tone)
causes interference with placental function (4)
-constriction spiral arteries (HTN)
-failure spiral arteries to dilate (preeclampsia)
-disruption intervillous space (abruption)
-compression spiral arteries (contractions)
effects of poorly perfused placentas
-IUGR (malnutrition)
-oxygen problems
assessment of placenta
-sonogram
-MRI (less common)
-(indirect) fetal HR monitoring
-doppler blood flow (umbilical artery)
-amniotic fluid index/volume
doppler blood flow assessment of umbilical artery indicating poor placental perfusion
absent/reverse diastolic blood flow
Dx of genetics anomalies
amniocentesis
chorionic villi sampling
percutaneous umbilical blood sampling
fetal assessments of oxygen during pregnancy
-sonogram: BPP, growth
-FHR
intrinsic mechanisms FHR
-CNS
-heart
-hormonal
how does sympathetic nervous system affect FHR
speeds up (“sympa = speedy”)
how does parasympathetic nervous system affect FHR
slows down (“para = pokey”)
receptors that take autonomic nervous system impulses to brain
-chemoreceptors
-baroreceptors
effects of stimulation of chemoreceptors on FHR
-increased FHR
-severe = bradycardia
effects of stimulation of baroreceptors on FHR
(responds to pressure)
-increase bp = rapid decrease FHR
-decrease bp = rapid increase FHR
what causes FHR variability
interplay between sympathetic and parasympathetic firing
affects of catecholamines on FHR
-shunts blood flow to vital organs (from GI and renal to brain, heart, adrenal)
sign of placental insufficiency
result from shunting of blood flow to vital organs
asymmetrical IUGR
(normal head growth, smaller chest/abdomen)
causes symmetric IUGR
-genetics
-problems early in pregnancy (TORCH infection, substance abuse)
