Term
| what is the difference between hypoxemia/hypoxia? |
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Definition
| hypoxemia - in blood, hypoxia - in tissue |
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Term
| what is the difference between acidemia/acidosis? |
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Definition
| acidemia - in blood, acidosis - in tissue |
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Term
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Definition
| hypoxia w/metabolic acidosis |
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Term
| what was fetal O2 delivery depend on? |
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Definition
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Term
| how do uterine contractions affect fetal O2 delivery? |
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Definition
| contractions decrease placental blood flow w/intermittent decreases in O2 delivery. the severity of this deficit is dependent on the frequency/strength/duration of contractions, maternal position, anesthesia, preeclampsia, abruption, chorio, CHTN, DM, and CT disorders |
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Term
| what characterizes the blood supply to the umbilical cord? |
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Definition
| 2 arteries from the fetal hypogastric artery drain the fetus and the fetal umbilical vein (which returns blood to the fetus through the liver and inferior vena cava via the ductus venosus) supplies the fetus |
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Term
| what is the umbilical cord protected by? how is it protected? |
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Definition
| wharton's jelly which protects against prolapse w/membrane rupture, entanglement, and compression w/oligohydramnios. |
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Term
| what is the fastest, normal heart rate in the fetus? |
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Definition
| the sinoatrial node (R atrium) |
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Term
| how do parasympathetics affect fetal heart rate (FHR)? where do they originate? |
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Definition
| parasympathetics (vagus/CNX) decrease FHR, cause beat-beat variability, and influence increases w/gestational age. the parasympathetics originate in the brainstem) |
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Term
| how do sympathetics affect fetal heart rate (FHR)? where do they originate? |
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Definition
| the sympathetics (in heart muscle) increase FHR. sympathetic impulses originate in the brain stem via cervical fibers and humeral stimulation of cardiac B-receptors via epinephrine from the adrenal medulla. |
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Term
| what is normal baseline FHR? how does this change w/gestational age? |
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Definition
| 110-160 bpm - which gradually decreases w/age (increased parasympathetic tone) |
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Term
| what is considered a reactive fetal heart acceleration at 32 wks or later? |
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Definition
| 15 bpm above baseline for 15 sec+ (but less than 2 min) within a 20 min timespan. |
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Term
| what is considered a reactive fetal heart acceleration at before 32 wks? |
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Definition
| 10 bpm above baseline for 10 sec+ (but less than 2 min) within a 20 min timespan. |
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Term
| what is the initial stimulus for variable decelerations? |
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Definition
| the umbilical vein is collapsed (compressed between the baby+uterine wall etc) which leads to a response from the baroreceptors (via reflex up afferent limb of neural reflex - affects vagal reflex), increasing the heart rate. then the umbilical arteries are the next to collapse. (remember these arteries/veins are flipped in the fetus) |
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Term
| what characterizes variable decelerations? |
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Definition
| slowing of the FHR w/abrupt onset and return, frequently preceded by and followed by accelerations (V, W shaped). these mainly coincide w/cord compression or maternal contraction and are associated w/favorable outcome. |
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Term
| what is a prolonged variable deceleration? what happens w/these? |
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Definition
| at least 15 bpm for more than 2 min (less than 10). prolonged variable decelerations are often followed by a blunt acceleration lasting more than a min w/o SVT. |
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Term
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Definition
| accelerations on either side of a variable deceleration. the rise of the first shoulder is due to increased heart rate (barometric response to the collapse of the umbilical vein), which then drops as the umbilical arteries collapse. |
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Term
| what are early decelerations? |
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Definition
| shallow and symmetric decelerations w/their nadir (bottom) at the same time as the peak of contraction. these are a benign response to head compression (change in cerebral blood flow stimulates vagal centers). |
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Term
| what is a jagged FHT baseline indicative of? |
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Definition
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Term
| what is a late deceleration? |
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Definition
| a gradual decrease in FHT w/return to baseline. onset to nadir is 30 sec or more. onset/nadir/recovery occur after the beginning and peak of a contraction. (more concerning) |
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Term
| what can cause a late deceleration? |
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Definition
| uteroplacental insufficiency - deoxygenated blood carried from the placenta through the umbilical vein to the heart/body, which is sensed by chemoreceptors that stimulate vagal discharge and a transient deceleration. acutely, distress, asphyxia, and intrapartum death can cause late deceleration and chronically, CHTN/DM/IUGR can cause this. chronic conditions are a more common cause of late deceleration. |
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Term
| what characterizes late decelerations during labor? |
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Definition
| occasional/intermittent late decelerations in labor are not uncommon, but persistence w/most contractions regardless of depth is not reassuring. late decelerations due to CNS response will get deeper w/more hypoxia - and may eventually lead to metabolic acidosis (very sick baby at birth). |
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Term
| what is considered tachycardia in the fetus? what may cause this? |
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Definition
| > 160 bpm, which may be due to maternal fever, intraamniotic infection, congenital heart disease, parasympathetic drugs (atropine/vistaril/atarax/phenothiazines), B-sympathetic drugs, and maternal hypothyroidism |
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Term
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Definition
| variation in successive beats, which indicates fetal CNS integrity, while decreasing variability can indicate poor response to hypoxia. |
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Term
| what is absent FHR variability? |
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Definition
| an undetectable amplitude range (flat line) |
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Term
| what is minimal FHR variability? |
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Definition
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Term
| what is moderate FHR variability? |
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Definition
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Term
| what is marked FHR variability? |
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Definition
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Term
| how does loss of FHR variability indicate? |
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Definition
| worsening hypoxia, but decreasing variability w/o decels is unlikely due to hypoxia (decels precede loss of variability) |
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Term
| what are other causes of variability loss besides hypoxia? |
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Definition
| medications (analgesics/narcotics, barbiturates, MgSO4, phenothiazines, general anesthetics, parasympatholytics), fetal sleep, prematurity, preexisting neurologic abnormalities (anencephaly), tachycardia, and complete heart block |
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Term
| what is a sinusoidal pattern? what can cause it? |
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Definition
| an oscillating baseline (sine wave) which lasts at least 10 min w/a 5-15 bpm amplitude. this can be due to chronic anemia or severe hypoxia/acidosis and is rare. |
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Term
| how is external fetal heart tracing (FHT) accomplished? |
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Definition
| indirectly/externally through a doppler. rate is calculated based on time from R wave to R wave. artifacts are possible. |
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Term
| how is internal FHT accomplished? risks? |
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Definition
| via a fetal scalp electrode (requires SROM/AROM - maternal rupture) which directly records the EKG. risks: prolapse, infection, trauma to eye/cord/placenta, and transmission of HSV/HIV |
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Term
| what does external tocometry measure? |
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Definition
| contractions. artifacts are possible (coughing/movement) |
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Term
| how is internal tocometry accomplished? |
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Definition
| via intrauterine pressure catheter (IUPC) and the montevideo units (MVU) need to be >200 over 10 min. |
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Term
| what is documented in terms of FHR? |
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Definition
| FHT: baseline, accels, decels - describe bpm/length/recovery/variability. |
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Term
| what is documented in terms of uterine contractions?? |
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Definition
| toco: contractions every 3-4 min and regularity/irritability |
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Term
| how can you decide if resuscitative measures for the fetus are necessary? |
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Definition
| vaginal exam to determine: rapid dilation/descent, prolapsed cord, and how close to delivery |
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Term
| how does a supine maternal position affect the fetus? |
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Definition
| when the mother is supine, the vena cava and aortoiliac vessels are compressed by the uterus (causing decreased blood return to the maternal heart and decreased CO/BP, decreasing uterine blood flow). therefore, the best maternal position is *lateral recumbent. |
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Term
| what can be done to increase FHR? |
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Definition
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Term
| what should happen w/scalp stimulation? |
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Definition
| an accel of 15 bpm for 15 sec, which lets you know the pH is at least 7.2. if no accel, 30% will have pH less than 7.2. *do not stimulate the scalp during deceleration. |
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