Definition

• Peripheral venous haematocrit (Hct) >65% 
• Symptoms rarely occur with peripheral Hct of <70%
• Hct peaks at 2 hr after birth and then decreases with significant changes occurring by 6 hr

Clinical consequences

• Hyperviscosity
• Decreased blood flow and impaired tissue perfusion
• Thrombus formation

Complications

• Cerebral micro-infarction and adverse neurodevelopmental outcome
• Renal vein thrombosis
• Necrotising enterocolitis (NEC)

Causes

Symptoms and signs

• Commonly plethoric but asymptomatic

In all unwell babies and at-risk babies who look plethoric (as mentioned above)

• FBC/Hct
• If Hct >65%, repeat a free-flowing venous sample or obtain arterial Hct (capillary Hct sample unreliable)
• If polycythaemic, check blood glucose and serum calcium 

• Ensure babies at risk have liberal fluid intake 1 day ahead of usual requirement (see Intravenous fluid therapy guideline)

Asymptomatic babies with Hct >70%

• Repeat venous Hct after 6 hr
  • if still high, discuss with consultant 

Symptomatic babies with Hct >65%

• Possible symptoms: fits and excessive jitteriness, with neurological signs and refractory hypoglycaemia

Treatment

• Dilutional/partial exchange transfusion. Discuss with consultant
  • use of haemodilution for treatment of polycythaemia is not supported by evidence and treatment of asymptomatic babies is not recommended 
  • explain to parents the need for exchange and possible risks before performing partial exchange transfusion. Partial exchange transfusion increases risk of NEC
  • use sodium chloride 0.9% (see Exchange transfusion guideline)
• Volume to be exchanged = 20 mL/kg 
• Perform exchange via peripheral arterial and IV lines or via umbilical venous catheter
• Take 5–10 mL aliquots and complete procedure over 15–20 min 

• Babies who required partial exchange transfusion require long-term neurodevelopmental follow-up
• Otherwise, follow-up will be dependent on background problem