We discuss the etiology, presentation, complications, and management of neonatal polycythemia. We are joined by Lincy Thomas, MD, Assistant Professor of Pediatric Hematology and Oncology at the University of Texas Southwestern Medical Center.
Dr. Neeta Goli:
Welcome to Newborn News, a podcast where we discuss educational topics for medical professionals who care for newborns. I'm your host, Dr. Neeta Goli, a pediatrician in the UT Southwestern newborn nursery. Welcome back to the podcast. In today's episode, we will be discussing neonatal polycythemia. We're recording remotely due to the ongoing COVID pandemic. We're joined today by Dr. Lincy Thomas, Assistant Professor of Pediatric Hematology and Oncology at UT Southwestern.
Dr. Lincy Thomas:
Hello.
Dr. Neeta Goli:
Hi, Dr. Thomas. Thanks for joining us today.
Dr. Lincy Thomas:
Thank you so much for having me.
Dr. Neeta Goli:
Neonatal polycythemia, if left untreated, might be related to hyperviscosity and can lead to significant neonatal morbidity which includes neurologic, cardiovascular, and GI effects. Please can you start by defining our normal range for hemoglobin and hematocrit in a newborn, and then how we define polycythemia?
Dr. Lincy Thomas:
Yeah. The normal range for hemoglobin is around 19, 19.3 plus or minus two, and then hematocrit is around 61 with a bigger range. It's plus or minus seven. Neonatal polycythemia is defined as a hematocrit or hemoglobin greater than about two standard deviations above the normal value for gestational and postnatal age. In term infants, polycythemia is when hematocrit from a peripheral venous sample is greater than 65% or the hemoglobin is greater than 22 grams per deciliter.
Dr. Lincy Thomas:
Now, in the clinical circumstances, the definition is typically based on hematocrit rather than hemoglobin concentration. It's based on peripheral venous samples because there's so much variability in the measurement for capillary samples. When we get a call about a capillary hematocrit from a heel stick that's elevated, we usually ask for the providers to confirm with a venous hematocrit before any clinical management decisions are made.
Dr. Neeta Goli:
Is there any general rule of thumb in terms of is the capillary expected to be higher or lower than the venous?
Dr. Lincy Thomas:
Sometimes, it's a falsely elevated. There's some variability. That's why when we get the calls, it's usually because they're elevated. So in our eyes, they're falsely elevated. We see it from the elevated standpoint because if they get a capillary hematocrit that's lower, they never call us for that.
Dr. Neeta Goli:
Okay. Why is normal hemoglobin and hematocrit so much higher in neonates than in adults?
Dr. Lincy Thomas:
Compared to older infants and children, term newborns just have an increased red cell mass. This is because of fetal response to increased hemoglobin concentration because they live in a relatively hypoxic intrauterine environment. It could also be because of vasomotor instability and venous pooling after the newborn is born.
Dr. Neeta Goli:
There are certain infants who we consider to be at higher risk of polycythemia. For example, infants of diabetic mothers, premature infants, those who are either small or large for gestational age and those with chromosomal abnormalities. In our institution, these infants routinely receive a one-time check of either hemoglobin or hematocrit as a screening test. Why are these infants specifically at higher risk of polycythemia?
Dr. Lincy Thomas:
Polycythemia is multifactorial. It's either because of active erythropoiesis, because of increased fetal erythropoiesis, or passive because of red cell transfusion. When you've got increased fetal erythropoiesis or active erythropoiesis, it's associated with many conditions such as placental insufficiency, endocrine abnormalities, and genetic disorders. But when you've got erythrocyte transfusion, or passive erythropoiesis, it's associated with conditions such as placental-fetal transfusion, delayed cord clamping, and even twin-to-twin transfusion syndrome. That's why these kids are at higher risk.
Dr. Neeta Goli:
You mentioned delayed cord clamping. ACOG now recommends delayed cord clamping, which is defined as clamping of the umbilical cord for 30 to 60 seconds after delivery for healthy, vigorous term and preterm infants. What are the neonatal outcomes from this? Have we seen any increases in polycythemia?
Dr. Lincy Thomas:
Delayed cord clamping as recommended by ACOG has actually been shown to have significant neonatal benefits, even in preterm infants, because it improves the transitional circulation and just establishes a better red cell volume with decreased need for blood transfusion later. Essentially, delayed cord clamping leads to an expanded blood volume being conveyed to the newborn child. But when cord clamping is delayed for greater than three minutes after birth, that's when you kind of run into issues with blood volumes rising greater than 30%. So when that happens, when it's delayed past three minutes, you could possibly see polycythemia and hyperbilirubinemia.
Dr. Neeta Goli:
Okay. So if we do discover a neonate to have hematocrit greater than 65%, what signs or symptoms should we watch out for?
Dr. Lincy Thomas:
A neonate with polycythemia usually has ruddy or dusky skin. They're usually lethargic and very tired with poor feeding, and may have an increased risk of seizures as well. In dealing with symptoms with little ones, first off, they're so little and fragile that some of their symptoms are not as specific, so just being hypervigilant if the little ones are being more irritable, lethargic, not feeding as well, just really having a high index of suspicion. Check the hemoglobin and hematocrit because the symptoms of polycythemia are not always as clear-cut.
Dr. Neeta Goli:
Polycythemia can often be associated with hyperviscosity. What is the relationship between these two?
Dr. Lincy Thomas:
A high concentration of red blood cells makes the blood thicker naturally. That's what hyperviscosity is. This can slow down the blood flow through small blood vessels and interfere with the delivery of oxygen to the tissues.
Dr. Neeta Goli:
Can you tell us a little bit about the relationship between polycythemia and hypoglycemia?
Dr. Lincy Thomas:
With polycythemia, because the blood flow is slower from the thicker blood volume, you can have ischemia and consumption of platelets in the small blood vessels. It's important to remember that glucose is actually transported mainly in the plasma. Because the relative plasma volume is decreased in the state of polycythemia, this decreased blood flow can actually result in hypoglycemia. So with patients with polycythemia, it's very important to monitor blood sugar levels in these little infants who at baseline are also at higher risk of hypoglycemia.
Dr. Neeta Goli:
What are some of the potential sequelae if this is left untreated?
Dr. Lincy Thomas:
Essentially, if the blood is flowing slower because of the thickness of the blood, you can have microcirculatory hypoperfusion. In the long run, this can lead to multisystem organ dysfunction. Like I mentioned the symptoms earlier, in addition to the symptoms, seizures are very rare. But because of the hypoperfusion, you can see seizures and increased neurological deficits as sequelae.
Dr. Neeta Goli:
Okay. In addition to potential neurologic and cerebrovascular complications, what other organ systems might be affected?
Dr. Lincy Thomas:
With microvascular hypoperfusion, you can honestly see an insult in any of the organ systems. But one of the most common ones that we see is also renal infarctions and insults. So making sure that you are checking renal function, liver function, all of those, are also very essential to follow up if you're worried about symptomatic polycythemia.
Dr. Neeta Goli:
And then if we do have a baby with polycythemia, how should we manage that baby?
Dr. Lincy Thomas:
It depends if the patient has symptoms or not. If it's a newborn that has no symptoms, we would recommend fluids for hydration given by venous or IV because dehydration can make the blood even thicker. But when the newborn has symptoms, then treatment with partial exchange transfusion may be given to reduce the concentration of the red blood cells. With partial exchange, some of the newborn's blood is removed and replaced with an equal amount of saline solution to dilute the remaining red blood cells and therefore correct the polycythemia.
Dr. Neeta Goli:
What are some complications or things that we should be aware of if babies need this procedure done?
Dr. Lincy Thomas:
You can have cardiovascular issues with the transition of the removal of the blood and dilution. It's not often common, especially in the situation of polycythemia where they already have sequelae and side effects from having increased thickness.
Dr. Neeta Goli:
What are the long-term outcomes for these babies?
Dr. Lincy Thomas:
These infants actually typically do really well. After having one partial exchange tranfusion, we usually follow them outpatient for a few more visits. These kids usually don't need any further interventions and it resolves. The longer that these children are out of the uterus and away from the passive transfusion that they are getting from their mom in utero, the less likely they are to continue to have polycythemia.
Dr. Neeta Goli:
To end today's episode, do you have any advice for our listeners while they care for newborns?
Dr. Lincy Thomas:
Really, just understanding that newborns are extremely fragile. They don't always present with classic symptoms that you would expect in an older child. Especially in the case of polycythemia, if there's any suspicion or concerns, we as hematologists would love to get that referral. Feel free to call us at any point if you have any questions or concerns.
Dr. Neeta Goli:
Okay. Thank you so much for joining us today, Dr. Thomas.
Dr. Lincy Thomas:
Thank you for having me.
Dr. Neeta Goli:
Thanks for listening to Newborn News. We hope you join us next time. If you like what you hear, make sure to subscribe and leave us a review. If you have questions, comments, feedback or suggestions for future episodes, please email me at NewbornNews@utsouthwestern.edu. As a reminder, this content is educational and is not meant to be used as medical advice. Views or opinions expressed in this podcast are those of myself and my guests, and do not necessarily reflect the views of the university.