Anaemia and blood product transfusions

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CHAPTER 16 Anaemia and blood product transfusions

Mark Davies, David Cartwright

Anaemia of prematurity

Newborn infants have decreased red blood cell (RBC) production and their haemoglobin concentration [Hb] falls in the weeks/months following birth. This normal fall in Hb is exaggerated in the preterm infant because of decreased erythropoietin production, decreased RBC survival, and blood loss due to frequent blood sampling. This results in anaemia of prematurity: common in preterm infants and universal in extremely low birth weight (ELBW) infants.

The clinical effects of anaemia include:

• increased respiratory effort or shortness of breath

• oxygen requirement not due to other obvious cause (such as chronic lung disease)

• poor weight gain.

When recovery from anaemia of prematurity occurs, iron stores are depleted quickly. Iron treatment is used to aid recovery from anaemia of prematurity (see page 76).

Erythropoietin has not been reliably demonstrated to prevent anaemia of prematurity or RBC donor exposure.

Top-up transfusion

• Always get consent for transfusion from parents before administering, and note this in the chart.

• Blood for neonatal ‘top-up’ transfusions is supplied in paediatric packs (paed packs). A single unit of donor RBC is split into 4 packs averaging ∼50 mL (25–100 mL). When a baby uses one of the 4 packs, the other 3 may be set aside for possible future use in that baby, thus limiting the number of donors the baby may be exposed to.

• The blood supplied in the paed packs has a haematocrit of about 0.6 (0.5–0.7). The blood is filtered to remove 99.998% of white cells, and irradiated.

• Indications:

— Capillary [Hb] <80 g/L and symptomatic in recovering babies. Some use the haematocrit as a guide — e.g. <0.25–0.3. However, using Hb is better because you are considering the oxygen-carrying capacity of the blood, which correlates more closely to the Hb concentration.

— Blood may be given at higher [Hb] in more acutely ill babies.

— Beware of the differences between capillary, venous and arterial Hb measurements. Arterial [Hb] may be 30 g/L below capillary [Hb]; venous [Hb] is in between (Starling’s hypothesis of capillary return).

• Dose: usual volume given is 25–30 mL/kg, over 4–6 hours.

Many would transfuse with smaller volumes: this is OK if the haematocrit of the transfused blood is higher (∼0.8); however, if not, the actual amount of transfused RBC will be inadequate and more transfusions may be required. This may increase the number of donors that any particular baby is exposed to.

Platelets

Thrombocytopaenia is a common problem in neonates. A cause should be looked for. It may be due to infection, thrombosis, ischaemic gut or isoimmunisation (neonatal alloimmune thrombocytopaenia — can be severe and cause devastating intracranial bleeds).

• Give a platelet transfusion if the platelet count is <25 × 10⁹/L. Always get consent for transfusion from parents before administering, and note this in the chart.

• Platelet transfusion may be required at higher platelet counts if there is bleeding or the baby requires surgery or other vascular procedures (e.g. central venous line insertion).

• In alloimmune thrombocytopaenia you may need specially matched platelets (although do not wait for them if there is bleeding). Diagnosis is made by testing both parents’ platelet groups for incompatibility. Intravenous immunoglobulin is sometimes used for refractory alloimmune thrombocytopaenia.

• Dose: usual volume given is 10 mL/kg, over 0.5–1 hour.

Albumin

The use of albumin infusions for infants with hypoalbuminaemia is controversial.

• Many ELBW infants (especially those whose main nutrition source is parenteral) do not make albumin well. It is these infants who some believe may benefit from an albumin infusion if the serum albumin is <25 g/L.

— If used, usually 1–2 g/kg of 20% (or 25%) albumin is given over at least 4 hours.

• An infusion of albumin may increase intravascular volume. This may lead to cardiovascular compromise if the albumin is infused too quickly.

Some clinicians would give frusemide half-way through the infusion to pre-empt this.

• Beware if there are leaky capillaries, as one might see in babies with capillary leak syndrome (CLS) secondary to septicaemia or trauma/surgery. Any infused albumin will leak into the tissues, osmotically dragging fluid with it — making any oedema worse. This may also deplete intravascular volume.

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