Polycythemia of the newborn is first mentioned in the Bible as Esau and Jacob are described at the time of their birth. Esau appears to be the recipient of a twin-to-twin transfusion (Genesis 25:25: “The first one emerged red …”). There is little in the modern medical literature concerning polycythemia in the newborn until the early 1970s [1–5]. During this time, there were a number of case reports and small series of infants with various symptoms that were thought to be secondary to an elevated hematocrit and blood viscosity. It was not until the 1980s that several investigators systematically examined the association between polycythemia, hyperviscosity of the blood, and organ-system dysfunction. These studies have done much to enlighten our understanding of the relationships between abnormalities of the hematocrit, blood viscosity, organ blood flow, and organ function. The dissemination of this knowledge has provided a clinical approach that is based on well-defined data and has clarified the role of polycythemia as an etiologic factor for organ dysfunction in the neonate.

Introduction

Polycythemia of the newborn is first mentioned in the Bible as Esau and Jacob are described at the time of their birth. Esau appears to be the recipient of a twin-to-twin transfusion (Genesis 25 : 25: “The first one emerged red …”). There is little in the modern medical literature concerning polycythemia in the newborn until the early 1970s (1–5). During this time, there were a number of case reports and small series of infants with various symptoms that were thought to be secondary to an elevated hematocrit and blood viscosity. It was not until the 1980s that several investigators systematically examined the association between polycythemia, hyperviscosity of the blood, and organ-system dysfunction. These studies have done much to enlighten our understanding of the relationships between abnormalities of the hematocrit, blood viscosity, organ blood flow, and organ function. The dissemination of this knowledge has provided a clinical approach that is based on well-defined data and has clarified the role of polycythemia as an etiologic factor for organ dysfunction in the neonate.

Definitions

Definitions of polycythemia and hyperviscosity have varied by study and methodology. Common variables have been the source of the blood sample and the age of the infant at the time of measurement (6–11). In many studies, a hematocrit value of 65% or above has been diagnostic for polycythemia. Using cord blood from appropriate-for-gestational-age (AGA) infants, Gross and colleagues defined hyperviscosity as a value that was two standard deviations greater than the mean (Fig. 9.1) (5). Using blood samples from three different sites (peripheral vein, umbilical vein, and capillary), Ramamurthy and Brans defined hyperviscosity as a value that was three standard deviations from the mean (6). This coincided with an umbilical venous hematocrit value of 63% or above. This study also found that capillary samples were higher than those from the peripheral vein, which in turn were greater than those from the umbilical vein.

Introduction

Since the third edition, this chapter has been expanded to cover both polycythemia and fetomaternal hemorrhage, a topic that is not extensively or comprehensively discussed in most commonly used textbooks. In the former the hematocrit and blood volume are generally increased, while in the latter both are generally very low. In both conditions, however, there is concern about inadequate organ blood flow, oxygenation delivery, and potential for hypoxic injury, especially in the brain. A large body of definitive information on polycythemia is available that allows conclusions to be made as to management and patient outcome. However, the area of fetomaternal hemorrhage has not been as comprehensively investigated and relies mostly on small clinical series and case reports. There are no controlled basic or clinical trials, which hampers our understanding of pathophysiology as well as therapeutic modalities. This leaves us with gaps in our knowledge of this important topic. What is presented here is the most current body of information and recommendations for diagnosis, treatment, and reported outcomes.

Polycythemia

Polycythemia and hyperviscosity were first associated with adverse neurologic events and sequelae in a series of case reports. The first case often referenced was published by Wood in 1952, and this was followed by a small series of infants with polycythemia and hyperviscosity who displayed multiple problems, including cerebral dysfunction.

Introduction

Polycythemia of the newborn is first mentioned in the Bible as Esau and Jacob are described at the time of their birth. Esau appears to be the recipient of a twin-to-twin transfusion (Genesis 25:25: “The first one emerged red …”). There is little in the modern medical literature concerning polycythemia in the newborn until the early 1970s [1–5]. During this time, there were a number of case reports and small series of infants with various symptoms that were thought to be secondary to an elevated hematocrit and blood viscosity. It was not until the 1980s that several investigators systematically examined the association between polycythemia, hyperviscosity of the blood, and organ-system dysfunction. These studies have done much to enlighten our understanding of the relationships between abnormalities of the hematocrit, blood viscosity, organ blood flow, and organ function. There has been little new information over the past ten years. However, the dissemination of this knowledge has provided a clinical approach that is based on well-defined data and has clarified the role of polycythemia as an etiologic factor for organ dysfunction in the neonate.

Definitions

Definitions of polycythemia and hyperviscosity have varied by study and methodology. Common variables have been the source of the blood sample and the age of the infant at the time of measurement [6–11]. In many studies, a hematocrit value of 65% or above has been diagnostic for polycythemia.

Introduction

Polycythemia and hyperviscosity were first associated with adverse neurologic events and sequelae in a series of case reports. The first case often referenced was published by Wood in 1952 and was followed by a small series of infants with polycythemia and hyperviscosity who displayed multiple problems, including cerebral dysfunction. Since those early reports it has become clear that polycythemia has multiple etiologies which influence whether and which problems may be associated with it in the newborn period. In addition more recent animal and human studies have clarified the relationship between polycythemia and alterations in function of various organs.

Definition

Polycythemia is usually defined in the literature as a hematocrit value ≥ 65% when the blood sample is obtained from a free-flowing, large venous blood vessel such as the inferior vena cava (umbilical vein sample) spun in a centrifuge. Sampling from small vessels with low flow or capillary samples will have higher values. In addition, hematocrits calculated by a Coulter counter will yield comparatively lower values. Independent of sample site or measurement technique, the hematocrit increases over the first 2–4 h of life, gradually returning to the birth value by 12–24 h of age.

Incidence

The incidence of polycythemia varies by definition, altitude of the population, pregnancy risk factors, and techniques involved in the delivery of the fetus, and timing and sampling sites of blood samples.