General maintenance fluid
- Maintenance fluid for basal fluid requirements are typically prescribed according to the 4 - 2 - 1 rule ('Holliday–Segar formula')
- 4ml/kg/hr for the first 10kg
- Add 2ml/kg/hr for the next 10kg
- Add 1ml/kg/hr for each additional kg above this
- As a worked example, a 22kg child needs:
- 4 x 10 = 40ml/hr
- 2 x 10 = 20ml/hr
- 2 x 1 = 2ml/hr
- = total of 62ml/hr or a daily fluid requirement of 1,488ml
- Alternatively this could be described as:
- 100ml/kg/day for weight up to 10kg
- 1L + additional 50ml/kg for every kilogram above 10kg, per day
- 1.5L + additional 20ml/kg for every kilogram above 20kg, per day
- For the same 22kg child in the example above this gives a daily fluid requirement of 1,540ml
- In the perioperative period maintenance fluids are often reduced to 60% of calculated maintenance dose in order to prevent hyponatraemia, which is:
- More common due to post-operative ADH release and varying ability to manage salt/water load
- Dangerous owing to the risk of cerebral oedema and central pontine demyelination
- Crytalloids are generally preferred for maintenance fluids, although the key facet is to ensure an isotonic maintenance fluid is given
- Examples of isotonic maintenance fluids include 0.9% NaCl, 0.9% NaCl + 5% dextrose, Hartmann's solution or 4.5% albumin
- Hypotonic solutions (i.e. pure dextrose solutions or lower saline solutions e.g. 4.5% or 0.18%) are more likely to cause hyponatraemia (see Risks section)
- Colloids
- The well-documented issues with hydroxyl-ethyl starch in adults have not been replicated in paediatric populations, with observational data showing no serious adverse drug reactions or incidences of HES-induced renal failure
- Albumin has been shown to be equivalent to HES in terms of its perioperative volume-expansion effect in those 2-12yrs undergoing cardiac surgery, with a similar safety profile
- However, HES is still largely avoided in paediatrics and colloids reserved as 'rescue' or second-line fluid strategies where large volumes of crystalloid have already been used
Neonatal fluid requirements
| Day |
Fluid requirement |
| 1 |
40 - 60 |
| 2 |
60-80 |
| 3 |
80-100 |
| 4 |
100-120 |
| 5+ |
120-150 |
- Generally need to use a dextrose-containing solution to avoid neonatal hypoglycaemia e.g. 10% dextrose
- Also require additives to fulfil requirements e.g. Na+ 3mmol/kg/day and K+ 2mmol/kg/day
Monitoring maintenance fluids
- Daily U&E if receiving IV fluid
- Daily glucose
- Daily weight
- Daily fluid balance assessment
- Fluid input/output chart
Perioperative management of fluids in the child undergoing surgery
- Various guidelines now suggest paediatric fasting rules are:
| Substance |
Fasting time |
| Solids |
6hrs |
| Breast milk |
3-4hrs |
| Clear fluids |
1hr or 'sip-'til-send' |
- Little evidence that 1hr clear fluids increases risk of pulmonary aspiration, and aspiration in paediatrics is both rare (approximately 0.1%) and rarely leads to significant morbidity or mortality even if it does occur
| Issues with excessive fasting |
| Dehydration |
| Hypovolaemia |
| Hypoglycaemia ± ketosis |
| Induced catabolism |
| ↑ patient ± carer distress or anxiety |
Replacement or resuscitation
- Significant hypovolaemia is unlikely in the elective surgical patient, especially if a 'sip-'til-send' strategy has been followed
- For emergency surgery, a fluid deficit may have arisen due to gastrointestinal losses, bleeding, sepsis, fever or burns
- Patients may require pre-operative resuscitation in order to prevent intra-operative haemodynamic compromise
- Hypotension is a late and worrisome sign of dehydration and other measures should be used to estimate degree of dehydration and appropriate volumes of replacement fluids (see above)
- Options include 0.9% NaCl with or without 5% dextrose, or balanced crystalloid solutions
Post-operative hyponatraemia
- Peri-operative factors such as acute illness, nausea, pain, anxiety, opioid use, surgical stimulus and hypovolaemia stimulate ADH release and thus water retention
- Administering hypotonic fluids in such scenarios creates excessive free water and risk of hyponatraemia
- Examples of hypotonic fluid include 0.18% NaCl + 4-5% dextrose, a commonly used maintenance fluid in adult patients
- Hyponatraemia may be further exacerbated by issues such as:
- Gastrointestinal loss
- High insensible loss e.g. sweating
- Cardiac failure
- Renal failure
- Liver failure
- Existing sodium homeostasis disorders e.g. SIADH, adrenal insufficiency
- This can cause a number of sequelae including hyponatraemic encephalopathy due to osmotic stress on neuronal and glial cells
- Management of hyponatraemic encephalopathy includes increasing the plasma sodium level to >125mmol/L to terminate/prevent seizures and then slowly correcting the sodium thereafter at a rate of approximately 0.5mmol/L/hr
- Hypernatraemia
- Occurs as use of isotonic fluids for maintenance fluid therapy provides supranormal sodium doses (daily requirements only ~1mmol/kg/day)
- However, the risk of hypernatraemia following isotonic fluid maintenance therapy is not well quantified
- Fluid overload
- Iatrogenic endothelial dysfunction, with consequent interstitial oedema
- Dilutional anaemia
- Hyperchloraemic acidosis from use of 0.9% NaCl