A diagnosis of polycythemia can be made when the venous hematocrit of a newborn within the first week of life is ≥65%, the peripheral hematocrit is ≥70%, or the hemoglobin level is >220g/L. At this point, increased blood viscosity and sluggish blood flow can lead to multi-system dysfunction. This condition may be seen in cases of twin-to-twin transfusion and fetal-maternal transfusion (with a hemoglobin difference >40g/L between twins), delayed cord clamping, or when the newborn is placed more than 20cm below the level of the maternal placenta after birth. Chronic intrauterine hypoxia, which increases fetal erythropoietin production, can also lead to polycythemia, as seen in small-for-gestational-age infants, post-term infants, and infants of mothers with pregnancy toxemia. Additionally, it may occur in conditions such as trisomy 21 syndrome, congenital adrenal hyperplasia, and neonatal hyperthyroidism.

bubble_chart Diagnosis

(1) Medical History Maternal medical history during pregnancy and childbirth history, etc. (2) Clinical Manifestations Symptoms may appear within 12 hours after birth, primarily due to increased blood viscosity, affecting the heart, lungs, central nervous system, gastrointestinal tract, and kidneys. Manifestations include: rapid breathing, persistent fetal circulation and heart failure, increased muscle tone and spasms, decreased appetite and vomiting, and even necrotizing enterocolitis, oliguria or proteinuria, hyperbilirubinemia, hypoglycemia, etc. The severity of these symptoms varies, and some cases may show no obvious symptoms. (3) Laboratory Tests Hemoglobin >220 g/L, often accompanied by thrombocytopenia. The primary diagnostic criterion is hematocrit.

﹝Treatment﹞

For symptomatic individuals, partial exchange transfusion should be promptly performed to reduce hematocrit and thereby decrease blood viscosity. Partial exchange transfusion, also known as small-volume isovolemic exchange transfusion, involves removing a certain amount of blood and replacing it with fresh plasma or 5% albumin to achieve a hematocrit below 60%. The calculation for the volume of blood to be exchanged is as follows: Exchange volume (ml) = (Patient's venous hematocrit - Target hematocrit) / Patient's venous hematocrit × kg (body weight) × 85. For example, if the target hematocrit = 55–60%, and the patient's venous hematocrit is 70%, then (70 - 60) × 3kg × 85ml/kg = 255/7 = 36ml, meaning 36 ml of blood should be exchanged.