Circulation and Fluids

Children have comparatively higher water content than adults.  They dehydrate easily.  Stroke volume is relatively fixed, so tachycardia is the main response to poor cardiac output.  Hypotension is a late sign if circulatory insufficiency, it is important therefore to note earlier signs such as prolonged capillary return (>2-3 secs).  Fluid resuscitation in the ICU is generally given IV as bolus 0.9% saline, 10-20ml/kg in the absence of significant cardiac disease.  As circulating blood volume is 80ml/kg, by the time the child has received 2 boluses (total 40ml/kg, ½ circulating volume), consideration should be given to administering blood products.

 
Full maintenance IV fluid is usually 5% dextrose with 0.45% saline or 0.9% saline.  (0.9% saline with dextrose preferred in head injury/neurosurgical patients) "Rule of thumb" maintenance fluid for a WELL child is:

 

4/2/1 Rule of fluids,  Give:
4ml/hr/kg for first 10kg of weight +​
​2ml/kg/hr for next 10 kg of weight +
1ml/kg/hr thereafter​

 

Note that this is recommended for a well child, not a sick child who is ventilated in ICU.  Give ~ 2/3 of recommended amount to ventilated children, (sick, ventilated children have increased ADH production, leaving them vulnerable to water retention / fluid overload and hyponatraemia).  Consider giving maintenance fluid as NG breast milk/formula/standard enteral nutrition if appropriate.  What ever amount of volume is given, accurate 24 hours fluid balance is essential.

Urine output is comparatively higher in small children.  A baby should have a urine output 2ml/hr minimum, an older child 1ml/hr minimum.  An IDC is not mandatory, but moderate opiate doses (>20mcg/kg/hr)  will lead to sphincter dysfunction and urinary retention, so in a child with low urine output, estimation of bladder volume is paramount.

 
Some children (eg:  those with gastro)  will need slow rehydration, depending on estimated degree of dehydration /fluid deficit.  Information on this can be found in the CDHB paediatric handbook on line.

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Page last reviewed: 14 May 2014
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