Intravenous fluid for children

Background

Recent guidance from the NPSA has emphasized the importance of accurate fluid management in paediatric patients across the perioperative period. This resulted from the analysis of a series of children who died from hyponatraemic coma. Recommendations on the types of fluid and monitoring of fluid balance and electrolytes have been widely employed throughout paediatric services.

Learning outcomes

1 Prepare appropriate fasting guidelines for elective paediatric surgery

2 Assess fluid dehydration in a child presenting for emergency surgery

3 Appreciate the risks associated with hyponatraemia in the perioperative period.

CPD matrix matches

2D02; 2D04

Case history 1

A 3-year-old boy who weighs 15 kg is scheduled for major elective orthopaedic surgery for an open reduction of a dysplastic hip. You are performing a preoperative assessment on the day prior to surgery.

What fasting instructions would you give his parents?

◆ Clear fluids: 2 hours

◆ Breast milk: 4 hours

◆ Solids and formula milk: 6 hours.

Case update

You review him briefly at 11 a.m. for surgery on the afternoon list. His mother tells you that he did not have any breakfast and last ate and drank at 7.30 p.m. the previous night. He is upset, because he is hungry.

Is this the optimal fasting regimen for this patient?

The ideal fluid management in paediatric practice varies between those patients on a morning list and those on an afternoon list. For a patient on a morning list, it is assumed that an otherwise healthy child scheduled for a morning list is adequately hydrated up until going to bed the previous night. Ideally, the child would have been given a 200 mL clear fluid drink before 7.00 a.m. For a patient on the afternoon list, they should have been given breakfast by 7.30 a.m. and ideally a clear fluid drink before 11.30 a.m.

However, even a prolonged fast, as in this case, as opposed to a 2-hour fast for clear fluids, is unlikely to be physiologically significant in terms of the cardiovascular status of the normally well child. It is likely, however, to result in a very unhappy and uncooperative child.

Your patient is the only case on the afternoon list starting at 1.30 p.m. It is now 11.15 a.m. How would you proceed with his fasting status and fluid management?

Explain to the parents regarding fasting for theatre and that it is not possible for their son to have anything to eat, as his surgery is planned for 1.30 p.m. He can have a clear fluid drink to be finished at 11.30 a.m. Sugar-containing fluids would be preferable, given his prolonged fasting period.

Perioperative hypoglycaemia is rare in most children, and the majority of normal, healthy children over 1 month of age will maintain a normal blood glucose. Children at risk of hypoglycaemia should be commenced on isotonic glucose-containing IV fluids preoperatively.

Your patient is taken to theatre at 1.30 p.m. His surgery will take approximately 3.5 hours, and he has an epidural sited for analgesia. Calculate his maintenance fluid requirements.

This is traditionally calculated in paediatric practice using the 4–2–1 formula, as described by Holliday and Segar in 1957. Hence, for this 15 kg patient:

First 10 kg (A): 4 mL/kg/hour (i.e. 40 mL/hour)

Second 10 kg (B): 2 mL/kg/day (i.e. 10 mL/hour)

For each kg over 20 kg (C): 1 mL/kg/day (i.e. 0 mL/hour)

Maintenance total (D) (which is D = A + B + C): 50 mL/hour.

In any case of prolonged fasting, it is also important to consider any fluid deficit.

What type of maintenance fluid would you use?

An isotonic fluid such as 0.9% NaCl, Hartmann’s solution, or Plasma-Lyte®. Your patient is having prolonged surgery (>3 hours) and regional anaesthesia; he should be given dextrose during surgery and should have his blood glucose level measured regularly.

What is this patient’s fluid deficit?

He has been fasting for 18 hours, with a 200 mL drink 2 hours previously. His hourly maintenance fluid requirement is 50 mL/kg. Therefore, his deficit is:

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Ideally, if he had been given breakfast at 7.30 a.m., with a clear fluid drink at 11.30 a.m., his fluid deficit would have been:

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An IV fluid bolus of 10–20 mL/kg of isotonic fluid should be given during surgery, and the remaining deficit replaced over 24 hours, in addition to maintenance fluid requirements.

You give your patient a 300 mL (20 mL/kg) bolus of fluid at the start of surgery. His remaining fluid deficit is 400 mL which should be replaced over 24 hours at 16 mL/hour, in addition to his maintenance fluids of 50 mL/hour; hence, his total fluid infusion rate should be 66 mL/hour, until full oral intake has been re-established. A single isotonic fluid should be used for both maintenance and correction of fluids.

What fluids would you use in the post-operative period?

Continue isotonic fluid with dextrose, until his oral intake is satisfactory. As per NPSA guidelines, any patient having prolonged IV fluid infusion should have electrolytes and blood glucose checked at least every 24 hours, more frequently if there is an abnormal result.

Case history 2

A 6-year-old girl (19 kg) presents with a 2-day history of abdominal pain, vomiting, and poor oral intake. Clinically, she has acute appendicitis and is moderately dehydrated (5%), but her vital signs are stable.

How would you assess her dehydration preoperatively?

She should have an IV cannula inserted and bloods for U&E and blood glucose. The assessment of dehydration includes the consideration of:

◆ Fluid deficit (to replace the fluid lost from dehydration):

A child’s water deficit in mL can be calculated following an estimation of the degree of dehydration expressed as % of body weight:

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The clinical assessment of hydration is difficult and often inaccurate. The gold standard of assessment is acute weight loss, but this is often difficult due to the lack of pre-illness weight. In this case, the fluid deficit is 5 × 19 × 10 = 950 mL. This should be replaced over 24 hours with isotonic fluid such as NaCl 0.9%, Hartmann’s solution, or Plasma-Lyte®.

◆ Maintenance fluid requirements:

First 10 kg (A): 4 mL/kg/hour (i.e. 40 mL/hour)

Second 10 kg (B): 2 mL/kg/hour (i.e. 18 mL/hour)

For each kg over 20 kg (C): 1 mL/kg/hour (i.e. 0 mL/hour)

Maintenance total (D) (where D = A + B + C): 58 mL/hour.

Both fluid deficit and maintenance fluids requirements should be managed by giving a single isotonic fluid.

◆ Ongoing losses:

Where possible, ongoing losses, e.g. through vomiting, should be measured every 4 hours and additionally replaced with an isotonic fluid such as 0.9% NaCl, Hartmann’s, or Plasma-Lyte®.

If her vital signs were unstable at presentation (e.g. tachycardic, tachypnoeic, with a prolonged CRT), how would this have altered your management?

◆ Call for senior help

◆ IV or intraosseus access: obtain urgent U&E and glucose

◆ Fluid bolus of 20 mL/kg of 0.9% NaCl (i.e. 380 mL)

◆ Reassess the clinical condition, and repeat fluid bolus, as required

◆ Consider the need for blood if Hb is low or if >40 mL/kg of fluid is required.

Case history 3

A 7-year-old boy is admitted for observation, following a head injury, and continues to have frequent vomiting. You are asked to prescribe IV fluids for him.

What is the appropriate fluid for this child?

In some circumstances, including head injuries, children should only ever be administered isotonic fluids such as 0.9% NaCl (with or without glucose), Hartmann’s solution, or Plasma-Lyte® (with or without glucose). Hypotonic fluids must be avoided.

Some children, including those with head injuries and those in the post-operative period, may develop hyponatraemia due to increased antidiuretic hormone (ADH) secretion. In these situations, fluid restriction to 60–70% of normal maintenance rate requirements may be beneficial. Senior and specialist advice should be sought where there is uncertainty about the best course of action.

Summary

The calculation of accurate fluid and electrolyte requirements is integral to the optimal perioperative management of a paediatric patient. Consideration must be given to potential deficits and ongoing losses and the awareness of the risks of hyponatraemia, and, as such, there is little place for hypotonic fluid use in general paediatric practice. Clinicians must be mindful of the incidence of hyponatraemia and must monitor electrolytes regularly in children receiving prolonged crystalloid fluid infusions.