Background

Hypernatraemic dehydration can be difficult to diagnose clinically as classic signs of dehydration may be absent. It is more common in breast fed infants. In Edinburgh, babies are weighed on day 3 of life, on the postnatal ward or in the community.  Those exhibiting ≥13% weight loss on PNW are referred to the PNW junior, with those exhibiting 13% - 14.9% weight loss in the community referred to middle grade/consultant. Any baby in the community with ≥15% weight loss should be referred to ED for initial assessment.

Babies in the community will be risk assessed and a decision made as to whether baby requires U&Es and any other relevant assessments or investigations. The aim is to keep mothers and babies together whenever safe and possible. Consider checking U&E’s on babies on the PNW when their day 3 weight loss is ≥13% as this enables early detection and management of hypernatraemia before babies go home. Always check U&E’s if ≥15% weight loss.

Assessment

• Details of pregnancy, delivery and resuscitation
• Feeding History (frequency and length / volume of feeds, milk supply, vomiting)
• History of weight loss
• Jaundice

Clinical Examination

• Assess hydration (mucous membranes, tissue turgor)
• Assess tissue perfusion (urine output, capillary refill time)
• Signs of shock (Unresponsiveness, tachycardia, hypotension)
• Is there anything that could potentially be interfering with breastfeeding?
• Severe tongue tie, cleft palate etc

Differential Diagnosis

• Insufficient milk supply
• Severe Jaundice
• Sepsis
• Metabolic disorders

Appropriate Investigations

For all babies:

• Plasma urea and electrolytes
• Creatinine
• Glucose

In addition the following samples should be considered in those with Na >160mmol/l

• Blood Gas
• Blood glucose
• SBR (if Jaundiced)
• Full blood count
• Septic screen
• Metabolic screen
• Urine for Organic acids, creatinine and urinary electrolytes
• Coagulation and LFT's

Fluid Management

Treatment of Shock

• Inform Consultant
• IV Access and bloods as above (if not already taken)
• Bolus of 10ml/kg 0.9% sodium chloride
• If the baby is hypoglycaemic
• consider giving glucose as part of the initial bolus, or
• give a single 1 hourly volume NG as part of the fluid resuscitation
• re-measure blood sugar an hour later.
• Assess the response to 1st bolus
• DO NOT give a 2nd bolus without discussing it with the consultant

Start maintenance fluids.

• Once the baby has been stabilised, start on maintenance fluids
• The volume and type of maintenance fluids depend both on the clinical state of the baby and on the plasma sodium level
• Aim to rehydrate babies slowly to prevent a rapid fall in plasma sodium
• A gradual reduction in Na concentration of no more than 1mmol/l/hour would be reasonable
• A more rapid fall should be discussed with seniors and fluid management adjusted accordingly.

Infants with severe hypernatraemia who are rehydrated at a rate of 150 ml/kg/day are more likely to develop convulsions and peripheral oedema than the infants whose fluid intake is restricted to 100 ml/kg/day (Banister et al (1974))

Suggested fluid regimes depending on Na concentration

If Na >170mmol/l

• Inform Consultant
• Slow rehydration is essential because of the risk of complications in severely hypernatraemic babies
• Start the baby on 100 ml/kg/day of 0.9% sodium chloride.
• Measure blood glucose 3 hourly and U&E's every 6 hours.
• Plasma sodium should not be allowed to fall more than 1mmol/l/ hour
• Continue on this regime for 24 hours
• In the event of blood glucose falling below 2.6
• Discuss with consultant
• Probably best to continue with 100mls/kg 0.9% sodium chloride and add concentrated (50%) glucose to the infusion
• After 24 hours, change to 0.45% sodium chloride in 5-10% glucose at same rate

If Na 160-170mmol/l

• Inform Consultant
• IV rehydration is usually not necessary in these babies and oral rehydration should usually suffice
• Use cup / bottle / syringe feeding if the baby is able to feed
• Use NG feeds if the baby is sleepy.
• Start the baby on 100ml/kg/day of milk given initially as hourly volumes.
• Ensure where appropriate that mum receives breastfeeding support and advice from nursing and midwifery staff
• Use expressed breast milk if available.
• Measure U&E's and blood glucose every 6 hours.
• Plasma sodium should not be allowed to fall more than 1mmol/l/ hour

If 150-160mmol/l

• Ensure where appropriate that mum receives breastfeeding support and advice from nursing and midwifery staff
• Feed the baby using a combination of breast or bottle feeds with top ups as required.
• Plasma Na should be checked every 12 hours.
• Consider if consultant needs to know

Ongoing management

• When Na falls below 150mmol/l baby can be weaned onto oral feeds
• Use either formula or breast milk, with top-ups as necessary
• The baby should be weighed daily until weight gain is satisfactory.
• Inform the community support team prior to discharge.