Fetal Heart Tracing

let's discuss the interpretation of fetal heart rate tracings so let's go over some terminology and some nomenclature when we talk about the fetal heart rate tracing we talked about the baseline the variability and accelerations when we talk about contractions the bottom part of this example we discuss if the contractions are normal and what tacca systole means let's start with baseline so a normal baseline is between 110 beats to 160 beats per minute and this is for the fetal heart rate tachycardia is considered to be 160 beats per minute sustained for a 10 minute timeframe and bradycardia is considered to be less than 100 beats per minute when it's sustained for a 10 minute timeframe so variability talks about the ability of the fetal heart rate to change above or below baseline when the variability is absent that means there's no change in the baseline when it's minimal it means it's less than 5 beats per minute moderate is 6 to 25 beats per minute and market is greater than 25 beats per minute in our example here we would call this moderate variability now when we discuss accelerations we divide that 2 before 32 weeks gestation and after 32 weeks gestation after 32 weeks gestation we expect to see an increase in the fetal heart rate by 15 beats per minute for 15 seconds over a two minute tracing but for 32 weeks normal accelerations consist of an increase in the fetal heart rate by 10 beats per minute for 10 seconds over a 2 minute tracing now contractions a normal amount of contractions are 5 or less contractions in a 10 minute time frame uterine taka Sicily means greater than 5 contractions in 10 minutes now there's something called montevideo units when a normally a patient is monitored in labor they have an external fetal monitor on because it sits on top of the it only tells us how often a patient is contracted it doesn't tell us how strong those contractions are with an intrauterine pressure catheter we're able to determine the strength of the contractions now how do we do this we take a 10-minute strip or a 10-minute tracing we look at the contractions during that time and we measure the area under the curve now a normal amount of contraction or a strength of contraction would be between 180 to 220 Montevideo units that's considered to be adequate contractions to allow labor to progress now that we've talked about the the fetal heart rate tracing and some of the terminology let's talk about the nomenclature so why do we even look at fetal heart rate tracing well fetal heart rate tracing provide some information to us to tell us about the current asset-based status of the fetus now we have three categories category one which is normal category two which can be indeterminate and category three which we consider abnormal let's see what makes each of those categories so a category one tracing in order for a tracing to be considered category one such as this one the fetal heart rate has to be between 110 to 160 beats per minute there must be moderate variability and there are no late or variable decelerations now a category 2 tracing again this is indeterminate to determine the acid-based status of our fetus so the fetal heart rate can be between 110 to 160 beats per minute but it can also be less than a hundred beats per minute which remember that means bradycardia but variability must be present it can be greater than 160 beats per minute which again that means tachycardia but again variability must be present as far as the variability it can be minimal or moderate or if it is absent such in this case there can be no late or variable accelerations for it to be considered a category two tracing acceleration should be present and if there are decelerations which again those can be later variable they can be present if there is a mental or moderate variability present now category three tracing this is considered abnormal and this would mean that the acid base fetal status is abnormal so category three what makes a category three tracing as far as variability it is absent with late or variable decelerations such as in this tracing there can be bradycardia which again is less than a hundred beats per minute or something call a sinusoidal pattern you'll also see this called a seesaw pattern and that actually shows fetal anemia now let's talk about the different types of decelerations that we can see on a fetal heart rate tracing we have early decelerations these decelerations particularly mirror the contractions and these are physiologic they're due to the two head compression and due to stimulation of the vagus nerve because they are physiologic there's nothing that we need to do the about them variable decelerations you can see there's a sharp decline in the fetal heart rate and then there's a sharp incline back to the baseline variable decelerations are due to cord compression now they can be relieved by doing an amnio infusion which is placed in fluid inside the uterus through the intrauterine pressure catheter that allows the fetus to get off of the court and to relieve these variable decelerations now late decelerations are a little bit more ominous these are due to utero placental insufficiency these we do have to address and we do want to correct so how do we address them one we give oxygen to the mom so there's more oxygen going to the fetus two if we are given pitocin to make contractions happen we want to stop the pitocin three we want to give IV fluids because that will allow more fluid to go to the placenta and then four we want to commonly place the patient in left lateral decubitus so that means we roll the mom to the left side that will rotate the uterus off of the inferior vena cava so we have increased venous return to the placenta now let's take a case you were called to the bedside of a 23 year old gravida one pair of zero female who has admitted an active labor on her most recent cervical exam she was 590 and minus one she received an epidural approximately 10 minutes ago her fetal heart racing which was category 1 is now shown to be this how would you describe this tracing what nomenclature would you use now would you say that a the patient is having early decelerations most likely from rapid cervical change be patient is having variable decelerations most likely from rapid cervical change see patient is having late decelerations most likely from hypotension related to recent epidural placement or D patient demonstrates a category 1 fetal heart tracing the answer is C we would describe this fetal heart rate tracing as a category 3 we can see that the patient is having a large late deceleration now it's important to remember that when the epidural is place a lot of times moms will suffer from hypotension this causes utero placental insufficiency and the fetus will compensate by having late decelerations

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