Elsevier

Clinics in Perinatology

Volume 31, Issue 3, September 2004, Pages 545-553
Clinics in Perinatology

Neonatal polycythemia: is partial exchange transfusion justified?

https://doi.org/10.1016/j.clp.2004.04.020Get rights and content

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Viscosity and flow

Poiseuille's equation provides a useful model to explain the physical properties that influence blood flow. The equation can be used to extrapolate the impact of polycythemia on tissue blood flow. Poiseuille's equation relates flow (F), difference in pressure (ΔP), the radius of the tube (r), viscosity (η), and the length of the tube (L) as follows: (F α ΔP.r4 / η.L). Nevertheless, one must remember that the equation was formulated for long straight tubes, a newtonian fluid (eg, water), and a

Measurement of viscosity

The gold standard for the measurement of viscosity is a whole blood viscometer that can accurately measure the viscosity of blood at the low shear rates that occur naturally in the capillary circulation. Unfortunately, whole blood viscometers are not universally available in the clinical setting. Because the erythrocyte number is the most important factor affecting viscosity, measurement of the neonatal Hct has been suggested as the best clinical screening test for identifying infants with

Polycythemia

The reported incidence of neonatal polycythemia in term newborns ranges from 0.4% to 12% [6], [7], [8]. This wide variation may result from different screening techniques, different sampling sites (capillary versus peripheral or central venous), varied patient populations, the mode of delivery and methodology of measuring (Coulter counter or centrifuged capillary blood), and the sampling time. The sampling time is the most important source of this variation. Shohat et al demonstrated that the

Treatment of polycythemia

Currently, hemodilution by PET is the recommended therapy for the polycythemic infant. PET has been shown to reduce pulmonary vascular resistance [10] and increase cerebral blood flow velocity [11], [12]. Bada et al [13] have documented that PET normalizes cerebral hemodynamics and improves the clinical status of infants with polycythemia. PET is a relatively simple procedure but has numerous potential complications. Unfortunately, there are no data regarding the incidence of complications of

Review of the literature

Given the uncertainty for the justification of continuing with such routine treatment protocols, the discussion herein systematically reviews the existing published literature. The objective of this review is to evaluate the efficacy of PET in preventing neurodevelopmental problems and other associated complications in infants with neonatal polycythemia. Only randomized or “quasi randomized trials” are reviewed; the subjects are term or near-term infants with neonatal polycythemia (defined as a

Review results

A search for the term hyperviscosity yielded 90 articles, whereas a search for the term polycythemia yielded 416 articles. The relevant articles could be categorized as 55 review articles, two practice guidelines, and 11 controlled clinical trials of PET. Careful reading of the articles revealed major differences and inconsistencies in the methodology used by different investigators. Differences were found in the definition of polycythemia, the populations studied, the age that the Hct was

Discussion

A systematic search of the literature for reports of neonatal hyperviscosity and polycythemia revealed few randomized controlled studies. Half of the reviewed studies were not relevant to this discussion, because they compared the use of different solutions in PET rather than the need for and results of PET [16], [23], [24], [25], [26]. Other studies could not document any consistent results suggesting that PET affected the long-term neurodevelopmental outcome, especially in asymptomatic

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      The long-term outcome is most likely to be related to the underlying cause of polycythemia. Schimmel et al. made the following recommendations based on the above studies45: In an asymptomatic polycythemic infant with presumed normal or increased blood volume: monitoring is sufficient.

    • The IUGR Newborn

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