Electrolyte Disturbances - Hypernatraemia

Signs and symptoms

Management

• Most often seen with incorrect ORS 
• Severe dehydration in small children 
• Children who can’t regulate intake eg CP 
• Over concentration of milk feeds 

Signs & Symptoms 

• Irritability increased tone 
• Doughy skin 
• Doesn’t look dehydrated 
• Seizures 
• Altered level of consciousness 

Management 

• If child is dehydrated, with hypernatremia Na+< 160, rehydrate with ½DD (60mmol/l Na+). 
• If child is dehydrated, with Na+>160, rehydrate with fluid containing a higher Na+ content up to approximately 2/3 of the serum Na+. Discuss fluid to be used with consultant. See how to mix below. 
• If child is not dehydrated, but hypernatremia is due to Na+ intoxication, use 5%DW. 
• Rehydrate slowly over 24-48 hrs. Aim for 0.5-1mmol/l decrease in sodium per hour. 
• Failure to decrease Na+ usually means the rehydration rate is probably too slow. 
• Fall of more than 1 mmol/l/hr on average means the rehydration rate is probably too rapid. 
• Repeat Na+levels at 4-6 hrs to observe response and adjust fluid type/rate appropriately. 
• If fluid mixture does not contain glucose, add 50% DW to make 5% solution (20ml 50% DW to 200ml). 
• If convulsions considered likely in the setting of high serum sodium (decreased level of consciousness, hyper-irritable child), refer to secondary level hospital, consider the use of prophylactic PhenobarbitoneIV20 mg/kg as a single dose. 

Sodium bicarbonate mixture in hypernatremia dehydration with severe metabolic acidosis 

This is not for rapid correction of a metabolic acidosis, but for persistent metabolic acidosis with high bicarb loss (eg. severe ongoing diarrhea). If child has severe metabolic acidosis with hypernatremia, custom made solution can be made by adding 4,2% NaBic (0,5mmol Na+/ml) to Na+ containing fluids. Use solution containing approximately 2/3 Na+ of the patient’s formal serum Na+. Always consult specialist. 

Eg. 10 kg child 10 % dehydrated with Na+175 

Volume required: Rehydration: 100ml/kg/24hrs = 1000ml= 42ml/hr, then add 

Maintenance: 100ml/kg/24hrs = 1000ml = 42ml/hr 

Ongoing losses: 50-100ml with each loose stool 

Solution to be used: 2/3 X 175 Na+= 116mmol/l (let’s use 100mmol/l solution) 

100mmol/l solution: ½DD has 60mmol/l Na+therefore we must add 40mmol/l Na+per 1000ml 

40mmol/l Na+= 80 ml 4.2% Nabic(0,5mmol Na+/ml) per 1000ml 

Divide 80 ml / 5 = 16ml 4.2% Nabic (to get from 1000ml to 200ml) 

16 ml 4.2% Nabic must be added to 200ml ½DD to make 100mmol/l solution 

Sodium concentrations: 

• 0,9% NaCl (154 mmol/l) 
• 1/2 DD (60 mmol/l) 
• 0,2% NaCl (34 mmol/l) 
• 4.2% Nabic (0,5mmol/ml) 

Sodium 140-160mmol/l 

To make a 50 mmol/L solution of Sodium. Mix 20ml 4.2% bicarbonate with 180ml 5%DW to use as maintenance fluid. KCl can be added 2ml/200ml = 20mmol/l or 4ml/200ml = 40mmol/l. 

Sodium > 160mmol/l 

Add 10 ml 4.2% bicarbinate to 190ml . DD (Na = 85mmol/l) use for maintenance and dehydration if necessary (ie not tolerating feeds) and hydrate slowly over 36hrs. 

Sodium > 170mmol/l 

Add 20ml 4.2% bicarbonate to 180ml . DD (Na = 110 mmol/l) use as above hydrate over 36hrs.