- Email: [email protected]
Paediatric fluid and electrolyte therapy guidelines
BASIC SCIENCE
Paediatric fluid and electrolyte therapy guidelines
now to be considered hypotonic since the glucose is ignored. Importantly the NPSA wanted all stocks of 4% glucose with 0.18% saline removed from non-specialized areas and this should now have happened (Table 2).
Anthony Lander
The NPSA say that postoperative fluid prescriptions should never include 4% glucose with 0.18% saline or 0.45% saline with 5% glucose and outside the neonatal period can only be chosen from: 0.9% saline 0.9% saline with 5% glucose Ringer’s lactate/Hartmann’s solution 4.5% albumin. For neonates 10% glucose with 0.18% saline and 0.45% saline with 5% glucose remain options.
Postoperative fluid prescriptions e new regulations
Abstract The advice in this article is based on a multidisciplinary consensus opinion generated by the Association of Paediatric Anaesthetists and on a National Patient Safety Agency (NPSA) recommendation of March 2007 entitled ‘Reducing the risk of hyponatraemia when administering intravenous infusions to children’. To this has been added advice from our specialist hospital fluid policy.
Prescribing intravenous fluids Intravenous fluids should be prescribed with the same care and attention as given to other drugs. No one prescribes analgesics when antibiotics are needed and no one should prescribe maintenance fluids when replacement fluids are intended.
Keywords Hyponatraemia; intravenous fluids; paediatrics
The National Patient Safety Agency (NPSA) Alert of 2007 was expected to bring about a widespread change in postoperative maintenance fluid administration such that children would receive solutions containing 0.9% saline or Hartmann’s solution rather than solutions containing 0.18% or 0.45% saline in glucose. Telephone surveys show that practice has changed such that 0.18% saline has mostly been removed from wards but that the preferred postoperative fluid is often 0.45% saline with 5% dextrose. The potential benefit of the recommendations is that the chances of serious error from bad prescribing will be reduced. However, hypernatraemia or hyperchloraemia should be looked for in those children having 0.9% saline or Hartmann’s solution for protracted periods and instances reported appropriately.
Fluids are given intravenously for the following four reasons:
Intravenous fluid prescriptions Practice should be determined locally and ideally intravenous fluids should be prescribed daily by the team involved in the child’s care either at the morning round or in the early evening before handover. Fluids should not be being prescribed by the night team who will not be as familiar with the patient unless the fluid management requires fine-tuning in response to the clinical situation or as a result of investigations. Such a patient would then have had a detailed and specific handover.
NPSA: The dangers of 4% glucose 0.18% saline The NPSA reminded clinicians of the dangers of the use of low-sodium-containing fluids such as 0.18% saline with 4% glucose. This fluid has always been inappropriate when used for resuscitation or when used to replace most fluid and electrolyte deficits or when given at excessive rates when maintenance fluids were intended. The risk is one of precipitating hyponatraemia which can be fatal. Sadly even in university and tertiary centres local audits have shown that inappropriate prescriptions like this are not rare. Many surgeons have traditionally used 4% glucose with 0.18% saline as a maintenance fluid when given at appropriate rates in well children based on their weight. This or 0.45% saline with 5% glucose has been traditionally given at reduced rates in the postoperative period. The term isotonic is now to be considered in relation to the tonicity of the electrolyte components of fluids. Thus 0.18% saline with 4% glucose and 0.45% saline with 5% glucose are
Potassium Potassium 20 mmol/litre (0.15%) (10 mmol in each 500-ml bag) should be included in maintenance fluids and in replacement fluids unless there are specific contraindications. If there are special reasons not to give potassium these should be detailed in the notes. Potassium is not included in the first 24 hours of life nor traditionally in the first 24 hours after surgery. However, it will be given if Hartmann’s solution is prescribed. Remember that most potassium is intracellular and so a slightly lower serum level than normal may indicate marked potassium depletion. Monitoring Monitoring of the patient’s weight is important and particularly helpful in managing rehydration. Urine specific gravity is also a good guide to rehydration. Daily electrolytes are mandatory in those solely on intravenous (IV) fluids for more than a day. The electrolytes should be looked at in the context of previous results and not simply in relation to the normal values. Typically when the serum sodium falls fluid restriction is appropriate and when it rises fluid rates
Anthony Lander PhD FRCS (Paed) DCH is a Consultant Surgeon at Birmingham Children’s Hospital, Birmingham, UK. Conflicts of interest: none declared.
SURGERY 28:8
circulatory support in resuscitating vascular collapse replacement of previous fluid and electrolyte deficits maintenance replacement of ongoing losses.
369
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
can be increased. This is particularly relevant in managing fluids in the postoperative period. A falling sodium is usually a sign of over administration of fluid and not of giving too little sodium.
saline is administered. Our preferred fluid is Hartmann’s solution since this gives less chloride. In term neonates during the first 48 hours of life 10% glucose should be given at a rate of 60 ml/kg/day unless there is a clinical indication for increased or decreased fluid administration. Sodium would be added to intravenous fluids on day 2e3 depending on renal function, serum sodium and weight. From day 3 of life maintenance fluid should be 0.18% saline with 10% glucose given at a rate of 4 ml/kg/hour or 100e120 ml/kg/day. Preterm babies or those <2 kg may require higher rates of administration and should be assessed at least daily by assessment of weight and electrolytes. Maintenance fluid requirements may need to be increased in children with pyrexia, excess sweating, hypermetabolic states such as burns or when radiant heaters or phototherapy is used. There is no consensus on whether maintenance fluid requirements should be reduced in children on a paediatric intensive care unit (PICU) who are sedated and ventilated with humidified gases. Simple calculations will show that the electrolyte requirements are met if 0.18% NaCl, 0.15% KCl is administered at the prescribed rates. But the dangers of hyponatraemia are considered to outweigh the benefits of restricting the sodium and chloride content of the fluid.
Circulatory support in shock The following fluids are appropriate for bolus administration at 10 or 20 ml/kg given over periods of up to 20 minutes. 0.9% saline Ringer’s lactate or Hartmann’s solution blood 4.5% albumin colloid or blood. It is inappropriate to use low-sodium-containing fluids in these situations. 0.18% saline or 0.45% saline in glucose is not to be used for circulatory resuscitation. Hyponatraemia can result and this can be fatal. Monitoring is typically based on the clinical response, blood pressure, capillary refill, blood gasses, etc. Serum electrolytes should be checked in anyone needing circulatory resuscitation.
Correcting previous fluid and electrolyte deficits However estimated, previous losses are typically between 5 and 15% of body weight. Sometimes the weight loss is accurately known. The fluid used to replace this deficit should be isotonic 0.9% sodium chloride or Ringer’s lactate/Hartmann’s solution. A 15-kg child who is 5% dehydrated has a water deficit of 750 ml. Audits have shown that it is not an uncommon misconception that 10% dehydration can be corrected by increasing maintenance fluid rates by 10%! This is clearly incorrect. Hypovolaemia, should be corrected with an initial fluid bolus of 10e20 ml/kg of an isotonic fluid or colloid, repeated as necessary followed by a slower correction of residual dehydration with an isotonic fluid, taking into account ongoing losses, serum electrolytes and urine output.
Fluids given during operations During surgery the majority of children may be given fluids without glucose. Blood glucose should be monitored. Maintenance fluid used during surgery should be isotonic such as 0.9% sodium chloride or Ringer’s lactate/Hartmann’s solution. Neonates in the first 48 hours of life should be given glucose during surgery. Preterm and term infants already receiving glucose-containing solutions should continue with them during surgery. Infants and children on parenteral nutrition preoperatively should continue to receive parenteral nutrition during surgery or change to a glucose-containing maintenance fluid and blood glucose monitored. Children of low body weight (less than 3rd centile) or having prolonged surgery should receive a glucose-containing maintenance fluid (1e2.5% glucose) or have their blood glucose monitored during surgery. Children having extensive regional anaesthesia with a reduced stress response should receive a glucose-containing maintenance fluid (1e2.5% glucose) or have their blood glucose monitored. All losses during surgery should be replaced with an isotonic fluid such as 0.9% sodium chloride, Ringer’s lactate/
Maintenance fluid requirements in children Maintenance fluid requirements are still to be calculated according to the recommendations of Holliday and Segar (see Table 1). Table 1 is a starting point only and the individual child’s response to fluid therapy should always be monitored and appropriate adjustments made. In children outside the neonatal period 0.45% saline in glucose or Hartmann’s solution or 0.9% saline are options supported by the NPSA. However, in the postoperative period it recommends not using 0.45% saline. These fluids give more than the daily requirements of sodium, but the risks of this are considered to be less than the risks of hyponatraemia if 0.18%
Normal water, electrolyte, energy and protein requirements Body weight First 10 kg Second 10 kg Subsequent kg
Water (ml/kg/day) 100 50 20
Sodium (mmol/kg/day) 2e4 1e2 0.5e1
Potassium (mmol/kg/day) 1.5e2.5 0.5e1.5 0.2e0.7
Energy (kcal/kg/day) 75 75 30
Protein (g/kg/day) 3.00 1.50 0.75
Table 1
SURGERY 28:8
370
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
Commonly available crystalloid fluids Fluid Saline 0.9% (normal saline) Saline 0.9% þ 0.15% KCl Saline 0.9% þ 0.15% KCl þ 5% glucose Hartmann’s solution Saline 0.45%, glucose 2.5% Saline 0.45%, glucose 5% Saline 0.18%, glucose 4% Saline 0.18%, glucose 4%, 10 mmol KCl/500 ml (0.15%) Glucose 5% Glucose 10% Saline 0.18%, glucose 10% Glucose 20%
Isotonic Isotonic Isotonic Isotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic
NaD (mmol/litre) 150 150 150 131 75 75 30 30 0 0 30 0
KD (mmol/litre) 0 20 20 5 0 0 0 20 0 0 0 0
ClL (mmol/litre) 150 170 170 111 75 75 30 50 0 0 30 0
Energy (kcal/litre) 0 0 200 0 100 200 160 160 200 400 400 800
Other 0
Lactate 0 0 0 0 0 0 0 0
Note: The tonicity ignores the glucose component. This is the view of the National Patient Safety Agency (NPSA).
Table 2
Hartmann’s solution, a colloid or blood, depending on the child’s haematocrit. In children over 3 months of age the haematocrit may be allowed to fall to 25%. Children with cyanotic congenital heart disease may need a higher haematocrit to maintain oxygenation.
Postoperative fluid management
Some preoperative surgical conditions are associated with increased antidiuretic hormone (ADH) production: empyema, sepsis, shock, etc. Operative trauma, pain, nausea and vomiting also contribute to ADH release. The NPSA alert has recommended that 0.18% and 0.45% saline in glucose should not be used for postoperative maintenance as they may cause hyponatraemia due to retention of free water released after metabolism of glucose from the solution. It recommends that the following fluids alone should be prescribed: 0.9% saline 0.9% saline 5% glucose Ringer’s lactate/Hartmann’s solution 4.5% albumin. Fluid rates in the postoperative period are still to be calculated using Holliday and Segar’s formula, and may be restricted to 70% of full maintenance if required. Ongoing losses from drains or nasogastric tubes should be replaced with an isotonic fluid such as 0.9% sodium chloride. It is possible that this change in practice may lead to high serum chlorides and these should be monitored. Hyperchloraemia can give rise to headaches, but it is less dangerous than hyponatraemia. Oral fluids should be started and increased after surgery whilst intravenous fluids are reduced and then discontinued. The rate at which this happens depends upon the child and the surgery.
Common electrolyte derangements Hyponatraemia Hyponatraemia (serum Na <135 mmol/litre) may occur in a number of situations, but is commonly seen when inappropriate fluids have been administered or following surgery with any fluid regime. Low-sodium-containing (0.18% NaCl) (hypotonic) maintenance fluids are more likely to precipitate hyponatraemia if fluids rates are inappropriately high. Presenting features of hyponatraemia include seizures or respiratory arrest. Headache is a consistent early sign of hyponatraemia in adults, but is rarely reported in children. Hyponatraemic encephalopathy should be managed as a medical emergency on PICU. Hyponatraemic seizures respond poorly to anticonvulsants and initial management is to give an infusion of 3% sodium chloride solution. One ml/kg of 3% sodium chloride will normally raise the serum sodium by 1 mmol/litre. Serum Na should be raised quickly until the child has regained consciousness and has stopped fitting or the serum Na is above 125 mmol/litre. The amount of Na required can be calculated according to the following formula:
Monitoring of fluid therapy Serum electrolytes do not need to be measured in all preoperatively healthy children prior to elective surgery where
SURGERY 28:8
IV fluids are to be given for the duration of surgery and for a short period thereafter. If there has been bowel preparation or there is unshunted hydrocephalus, electrolytes should be checked preoperatively Serum electrolytes need to be measured preoperatively in all children presenting for elective or emergency surgery who require IV fluid to be administered prior to surgery. Children should be weighed prior to fluids being prescribed. Serum electrolytes should be measured every 24 hours in all children on IV fluids or more frequently if abnormal. Children should be weighed daily while on IV fluids unless this is difficult. A fluid input/output chart must be carefully maintained and checked by the prescribing doctor.
371
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
infusion of 0.3e0.5 g/kg/hour of glucose with 1 unit of insulin for every 5 g of glucose or to give 2.5e5 mg nebulized salbutamol (5 mg/kg in neonates IV). Removal of potassium from the body can be achieved by giving 1 g/kg calcium resonium rectally or orally, by use of furosemide 1 mg/kg or by dialysis or haemofiltration.
mmol of Na required ¼ ð130 present serum NaÞ 0:6 weight ðkgÞ Once seizures have stopped, a slower Na correction should take place using 0.9% sodium chloride solution. Asymptomatic hyponatraemia does not require active correction with 3% sodium chloride solution. The dehydrated child may be treated with enteral fluids or if not tolerated, with intravenous 0.9% sodium chloride solution. The child with asymptomatic hyponatraemia and normal or increased volume status, if taking oral fluids should be volume restricted or if on IV fluids should have fluid administered at 50% of maintenance rate. If eating, salt can be added to the food.
Calcium imbalance Hypocalcaemia (corrected total Ca <2 mmol/litre or <1.5 mmol/litre in neonates) may produce symptoms of twitching and jitteriness, perioral, finger and toe paraesthesia, masseter and carpopedal spasm, prolonged QT interval and reduced cardiac contractility. Immediate treatment is with 10% calcium gluconate 0.5 ml/kg to a maximum of 20 ml over 10 minutes or 10% calcium gluconate 0.2 ml/kg to a maximum of 10 ml over 10 minutes. Warning: there is a danger of extravasation causing tissue injury. The central venous route should be considered for injection with continuous ECG monitoring during injection. Calcium levels appear low in the newborn because of low albumin levels. There is a normal physiological fall in calcium concentration after birth which rises after the second day. Causes of hypocalcaemia in the newborn are encephalopathy, renal failure, Di George syndrome, disordered maternal metabolism or maternal diabetes mellitus.
Hypernatraemia Hypernatraemia (serum Na >150 mmol/litre) commonly occurs as a result of excessive water loss, restricted water intake or an inability to respond to thirst. It may also occur in infants given incorrectly made feeds. Hypernatraemia can be fatal. Signs of hypernatraemia are more severe when it develops rapidly or when the serum Na is >160 mmol/litre. Chronic hypernatraemia is often well tolerated because of cerebral compensation. The true degree of dehydration is often underestimated if clinical signs alone are used compared to loss of weight. Intravascular volume is often well preserved during the initial stages. The management of hypernatraemic dehydration consists of initial volume replacement with 0.9% sodium chloride given in boluses of 20 ml/kg to restore normovolaemia. Complete correction should then be done very slowly over at least 48 hours to prevent cerebral oedema, seizures and brain injury. The serum Na should be corrected at a reduction of no more than 12 mmol/litre/day with 0.45% sodium chloride or 0.9% sodium chloride in glucose. In hypernatraemic dehydration it is important to give maintenance fluid alongside fluid to correct dehydration.
Pyloric stenosis: hypochloraemia correction Children with pyloric stenosis typically present with a mild hypochloraemic alkalotic dehydration. Resuscitation can be based on the serum chloride in most children. Calculate the chloride deficit and replace over 12e48 hours depending on severity. Chloride deficit ¼ 2=3 weight ðkgÞ 110 Cl : Use 0.9% saline 0.15% Kþ (170 mmol Cl/litre) or 0.45% saline, 5% glucose 0.15% Kþ (95 mmol Cl/litre).
Potassium imbalance Hypokalaemia (serum K <3.5 mmol/litre) produces symptoms of cramp, arrhythmias, reduced cardiac contractility and paralytic ileus. If possible oral supplements of 3e5 mmol/kg/ day should be given. Orange juice and bananas are rich in potassium. In severe hypokalaemia (serum K <3 mmol/litre), intravenous correction should be no faster than 0.25 mmol/kg/hour using a maximum peripheral concentration of 40 mmol/litre KCl (as per British National Formulary for Children). For a more rapid correction, the patient should be in PICU and the infusion administered via a central line. Hyperkalaemia (serum K >5.5 mmol/litre) causes skeletal muscle weakness and electrocardiography (ECG) changes when serum K >7 mmol/litre. Immediate treatment of hyperkalaemia is to antagonize membrane effects by giving 100 mg/kg of 10% calcium gluconate. This equates to 0.5 ml/kg of a 10% solution (1 ml 10% calcium gluconate contains 0.22 mmol calcium) Advanced Paediatric Life Support (APLS) recommendation). Alongside this it is important to increase intracellular shift of potassium by giving 1e2 mmol/kg of sodium bicarbonate, an
SURGERY 28:8
Example: a 3.3-kg child is mildly dehydrated with a Cl of 85 mmol/litre: deficit ¼ 2=3 3:3 ð110 85Þ ¼ 55 mmol Cl This is contained in 55/170 ¼ 325 ml of 0.9% saline with 0.15% Kþ. If this fluid is given at 180 ml/kg/day ¼ 25 ml/hour, the child will receive 55 mmol Cl in 13 hours. Alternatively if 0.45% saline, with 5% glucose and 0.15% Kþ is used at 180 ml/kg/day, they will receive 55 mmol in 23 hours. If the serum chloride is then remeasured and the bicarbonate checked, they will most likely be corrected. When corrected use appropriate maintenance fluids, but continue to replace nasogastric losses with 0.9% saline 0.15% Kþ.
Summary Great care and respect should be given to intravenous fluid management. It is important to understand the basic science, the risks and now the national guidelines which have been outlined here and expanded with other consensus statements. A 372
Ó 2010 Elsevier Ltd. All rights reserved.
Paediatric fluid and electrolyte therapy guidelines
now to be considered hypotonic since the glucose is ignored. Importantly the NPSA wanted all stocks of 4% glucose with 0.18% saline removed from non-specialized areas and this should now have happened (Table 2).
Anthony Lander
The NPSA say that postoperative fluid prescriptions should never include 4% glucose with 0.18% saline or 0.45% saline with 5% glucose and outside the neonatal period can only be chosen from: 0.9% saline 0.9% saline with 5% glucose Ringer’s lactate/Hartmann’s solution 4.5% albumin. For neonates 10% glucose with 0.18% saline and 0.45% saline with 5% glucose remain options.
Postoperative fluid prescriptions e new regulations
Abstract The advice in this article is based on a multidisciplinary consensus opinion generated by the Association of Paediatric Anaesthetists and on a National Patient Safety Agency (NPSA) recommendation of March 2007 entitled ‘Reducing the risk of hyponatraemia when administering intravenous infusions to children’. To this has been added advice from our specialist hospital fluid policy.
Prescribing intravenous fluids Intravenous fluids should be prescribed with the same care and attention as given to other drugs. No one prescribes analgesics when antibiotics are needed and no one should prescribe maintenance fluids when replacement fluids are intended.
Keywords Hyponatraemia; intravenous fluids; paediatrics
The National Patient Safety Agency (NPSA) Alert of 2007 was expected to bring about a widespread change in postoperative maintenance fluid administration such that children would receive solutions containing 0.9% saline or Hartmann’s solution rather than solutions containing 0.18% or 0.45% saline in glucose. Telephone surveys show that practice has changed such that 0.18% saline has mostly been removed from wards but that the preferred postoperative fluid is often 0.45% saline with 5% dextrose. The potential benefit of the recommendations is that the chances of serious error from bad prescribing will be reduced. However, hypernatraemia or hyperchloraemia should be looked for in those children having 0.9% saline or Hartmann’s solution for protracted periods and instances reported appropriately.
Fluids are given intravenously for the following four reasons:
Intravenous fluid prescriptions Practice should be determined locally and ideally intravenous fluids should be prescribed daily by the team involved in the child’s care either at the morning round or in the early evening before handover. Fluids should not be being prescribed by the night team who will not be as familiar with the patient unless the fluid management requires fine-tuning in response to the clinical situation or as a result of investigations. Such a patient would then have had a detailed and specific handover.
NPSA: The dangers of 4% glucose 0.18% saline The NPSA reminded clinicians of the dangers of the use of low-sodium-containing fluids such as 0.18% saline with 4% glucose. This fluid has always been inappropriate when used for resuscitation or when used to replace most fluid and electrolyte deficits or when given at excessive rates when maintenance fluids were intended. The risk is one of precipitating hyponatraemia which can be fatal. Sadly even in university and tertiary centres local audits have shown that inappropriate prescriptions like this are not rare. Many surgeons have traditionally used 4% glucose with 0.18% saline as a maintenance fluid when given at appropriate rates in well children based on their weight. This or 0.45% saline with 5% glucose has been traditionally given at reduced rates in the postoperative period. The term isotonic is now to be considered in relation to the tonicity of the electrolyte components of fluids. Thus 0.18% saline with 4% glucose and 0.45% saline with 5% glucose are
Potassium Potassium 20 mmol/litre (0.15%) (10 mmol in each 500-ml bag) should be included in maintenance fluids and in replacement fluids unless there are specific contraindications. If there are special reasons not to give potassium these should be detailed in the notes. Potassium is not included in the first 24 hours of life nor traditionally in the first 24 hours after surgery. However, it will be given if Hartmann’s solution is prescribed. Remember that most potassium is intracellular and so a slightly lower serum level than normal may indicate marked potassium depletion. Monitoring Monitoring of the patient’s weight is important and particularly helpful in managing rehydration. Urine specific gravity is also a good guide to rehydration. Daily electrolytes are mandatory in those solely on intravenous (IV) fluids for more than a day. The electrolytes should be looked at in the context of previous results and not simply in relation to the normal values. Typically when the serum sodium falls fluid restriction is appropriate and when it rises fluid rates
Anthony Lander PhD FRCS (Paed) DCH is a Consultant Surgeon at Birmingham Children’s Hospital, Birmingham, UK. Conflicts of interest: none declared.
SURGERY 28:8
circulatory support in resuscitating vascular collapse replacement of previous fluid and electrolyte deficits maintenance replacement of ongoing losses.
369
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
can be increased. This is particularly relevant in managing fluids in the postoperative period. A falling sodium is usually a sign of over administration of fluid and not of giving too little sodium.
saline is administered. Our preferred fluid is Hartmann’s solution since this gives less chloride. In term neonates during the first 48 hours of life 10% glucose should be given at a rate of 60 ml/kg/day unless there is a clinical indication for increased or decreased fluid administration. Sodium would be added to intravenous fluids on day 2e3 depending on renal function, serum sodium and weight. From day 3 of life maintenance fluid should be 0.18% saline with 10% glucose given at a rate of 4 ml/kg/hour or 100e120 ml/kg/day. Preterm babies or those <2 kg may require higher rates of administration and should be assessed at least daily by assessment of weight and electrolytes. Maintenance fluid requirements may need to be increased in children with pyrexia, excess sweating, hypermetabolic states such as burns or when radiant heaters or phototherapy is used. There is no consensus on whether maintenance fluid requirements should be reduced in children on a paediatric intensive care unit (PICU) who are sedated and ventilated with humidified gases. Simple calculations will show that the electrolyte requirements are met if 0.18% NaCl, 0.15% KCl is administered at the prescribed rates. But the dangers of hyponatraemia are considered to outweigh the benefits of restricting the sodium and chloride content of the fluid.
Circulatory support in shock The following fluids are appropriate for bolus administration at 10 or 20 ml/kg given over periods of up to 20 minutes. 0.9% saline Ringer’s lactate or Hartmann’s solution blood 4.5% albumin colloid or blood. It is inappropriate to use low-sodium-containing fluids in these situations. 0.18% saline or 0.45% saline in glucose is not to be used for circulatory resuscitation. Hyponatraemia can result and this can be fatal. Monitoring is typically based on the clinical response, blood pressure, capillary refill, blood gasses, etc. Serum electrolytes should be checked in anyone needing circulatory resuscitation.
Correcting previous fluid and electrolyte deficits However estimated, previous losses are typically between 5 and 15% of body weight. Sometimes the weight loss is accurately known. The fluid used to replace this deficit should be isotonic 0.9% sodium chloride or Ringer’s lactate/Hartmann’s solution. A 15-kg child who is 5% dehydrated has a water deficit of 750 ml. Audits have shown that it is not an uncommon misconception that 10% dehydration can be corrected by increasing maintenance fluid rates by 10%! This is clearly incorrect. Hypovolaemia, should be corrected with an initial fluid bolus of 10e20 ml/kg of an isotonic fluid or colloid, repeated as necessary followed by a slower correction of residual dehydration with an isotonic fluid, taking into account ongoing losses, serum electrolytes and urine output.
Fluids given during operations During surgery the majority of children may be given fluids without glucose. Blood glucose should be monitored. Maintenance fluid used during surgery should be isotonic such as 0.9% sodium chloride or Ringer’s lactate/Hartmann’s solution. Neonates in the first 48 hours of life should be given glucose during surgery. Preterm and term infants already receiving glucose-containing solutions should continue with them during surgery. Infants and children on parenteral nutrition preoperatively should continue to receive parenteral nutrition during surgery or change to a glucose-containing maintenance fluid and blood glucose monitored. Children of low body weight (less than 3rd centile) or having prolonged surgery should receive a glucose-containing maintenance fluid (1e2.5% glucose) or have their blood glucose monitored during surgery. Children having extensive regional anaesthesia with a reduced stress response should receive a glucose-containing maintenance fluid (1e2.5% glucose) or have their blood glucose monitored. All losses during surgery should be replaced with an isotonic fluid such as 0.9% sodium chloride, Ringer’s lactate/
Maintenance fluid requirements in children Maintenance fluid requirements are still to be calculated according to the recommendations of Holliday and Segar (see Table 1). Table 1 is a starting point only and the individual child’s response to fluid therapy should always be monitored and appropriate adjustments made. In children outside the neonatal period 0.45% saline in glucose or Hartmann’s solution or 0.9% saline are options supported by the NPSA. However, in the postoperative period it recommends not using 0.45% saline. These fluids give more than the daily requirements of sodium, but the risks of this are considered to be less than the risks of hyponatraemia if 0.18%
Normal water, electrolyte, energy and protein requirements Body weight First 10 kg Second 10 kg Subsequent kg
Water (ml/kg/day) 100 50 20
Sodium (mmol/kg/day) 2e4 1e2 0.5e1
Potassium (mmol/kg/day) 1.5e2.5 0.5e1.5 0.2e0.7
Energy (kcal/kg/day) 75 75 30
Protein (g/kg/day) 3.00 1.50 0.75
Table 1
SURGERY 28:8
370
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
Commonly available crystalloid fluids Fluid Saline 0.9% (normal saline) Saline 0.9% þ 0.15% KCl Saline 0.9% þ 0.15% KCl þ 5% glucose Hartmann’s solution Saline 0.45%, glucose 2.5% Saline 0.45%, glucose 5% Saline 0.18%, glucose 4% Saline 0.18%, glucose 4%, 10 mmol KCl/500 ml (0.15%) Glucose 5% Glucose 10% Saline 0.18%, glucose 10% Glucose 20%
Isotonic Isotonic Isotonic Isotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic Hypotonic
NaD (mmol/litre) 150 150 150 131 75 75 30 30 0 0 30 0
KD (mmol/litre) 0 20 20 5 0 0 0 20 0 0 0 0
ClL (mmol/litre) 150 170 170 111 75 75 30 50 0 0 30 0
Energy (kcal/litre) 0 0 200 0 100 200 160 160 200 400 400 800
Other 0
Lactate 0 0 0 0 0 0 0 0
Note: The tonicity ignores the glucose component. This is the view of the National Patient Safety Agency (NPSA).
Table 2
Hartmann’s solution, a colloid or blood, depending on the child’s haematocrit. In children over 3 months of age the haematocrit may be allowed to fall to 25%. Children with cyanotic congenital heart disease may need a higher haematocrit to maintain oxygenation.
Postoperative fluid management
Some preoperative surgical conditions are associated with increased antidiuretic hormone (ADH) production: empyema, sepsis, shock, etc. Operative trauma, pain, nausea and vomiting also contribute to ADH release. The NPSA alert has recommended that 0.18% and 0.45% saline in glucose should not be used for postoperative maintenance as they may cause hyponatraemia due to retention of free water released after metabolism of glucose from the solution. It recommends that the following fluids alone should be prescribed: 0.9% saline 0.9% saline 5% glucose Ringer’s lactate/Hartmann’s solution 4.5% albumin. Fluid rates in the postoperative period are still to be calculated using Holliday and Segar’s formula, and may be restricted to 70% of full maintenance if required. Ongoing losses from drains or nasogastric tubes should be replaced with an isotonic fluid such as 0.9% sodium chloride. It is possible that this change in practice may lead to high serum chlorides and these should be monitored. Hyperchloraemia can give rise to headaches, but it is less dangerous than hyponatraemia. Oral fluids should be started and increased after surgery whilst intravenous fluids are reduced and then discontinued. The rate at which this happens depends upon the child and the surgery.
Common electrolyte derangements Hyponatraemia Hyponatraemia (serum Na <135 mmol/litre) may occur in a number of situations, but is commonly seen when inappropriate fluids have been administered or following surgery with any fluid regime. Low-sodium-containing (0.18% NaCl) (hypotonic) maintenance fluids are more likely to precipitate hyponatraemia if fluids rates are inappropriately high. Presenting features of hyponatraemia include seizures or respiratory arrest. Headache is a consistent early sign of hyponatraemia in adults, but is rarely reported in children. Hyponatraemic encephalopathy should be managed as a medical emergency on PICU. Hyponatraemic seizures respond poorly to anticonvulsants and initial management is to give an infusion of 3% sodium chloride solution. One ml/kg of 3% sodium chloride will normally raise the serum sodium by 1 mmol/litre. Serum Na should be raised quickly until the child has regained consciousness and has stopped fitting or the serum Na is above 125 mmol/litre. The amount of Na required can be calculated according to the following formula:
Monitoring of fluid therapy Serum electrolytes do not need to be measured in all preoperatively healthy children prior to elective surgery where
SURGERY 28:8
IV fluids are to be given for the duration of surgery and for a short period thereafter. If there has been bowel preparation or there is unshunted hydrocephalus, electrolytes should be checked preoperatively Serum electrolytes need to be measured preoperatively in all children presenting for elective or emergency surgery who require IV fluid to be administered prior to surgery. Children should be weighed prior to fluids being prescribed. Serum electrolytes should be measured every 24 hours in all children on IV fluids or more frequently if abnormal. Children should be weighed daily while on IV fluids unless this is difficult. A fluid input/output chart must be carefully maintained and checked by the prescribing doctor.
371
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
infusion of 0.3e0.5 g/kg/hour of glucose with 1 unit of insulin for every 5 g of glucose or to give 2.5e5 mg nebulized salbutamol (5 mg/kg in neonates IV). Removal of potassium from the body can be achieved by giving 1 g/kg calcium resonium rectally or orally, by use of furosemide 1 mg/kg or by dialysis or haemofiltration.
mmol of Na required ¼ ð130 present serum NaÞ 0:6 weight ðkgÞ Once seizures have stopped, a slower Na correction should take place using 0.9% sodium chloride solution. Asymptomatic hyponatraemia does not require active correction with 3% sodium chloride solution. The dehydrated child may be treated with enteral fluids or if not tolerated, with intravenous 0.9% sodium chloride solution. The child with asymptomatic hyponatraemia and normal or increased volume status, if taking oral fluids should be volume restricted or if on IV fluids should have fluid administered at 50% of maintenance rate. If eating, salt can be added to the food.
Calcium imbalance Hypocalcaemia (corrected total Ca <2 mmol/litre or <1.5 mmol/litre in neonates) may produce symptoms of twitching and jitteriness, perioral, finger and toe paraesthesia, masseter and carpopedal spasm, prolonged QT interval and reduced cardiac contractility. Immediate treatment is with 10% calcium gluconate 0.5 ml/kg to a maximum of 20 ml over 10 minutes or 10% calcium gluconate 0.2 ml/kg to a maximum of 10 ml over 10 minutes. Warning: there is a danger of extravasation causing tissue injury. The central venous route should be considered for injection with continuous ECG monitoring during injection. Calcium levels appear low in the newborn because of low albumin levels. There is a normal physiological fall in calcium concentration after birth which rises after the second day. Causes of hypocalcaemia in the newborn are encephalopathy, renal failure, Di George syndrome, disordered maternal metabolism or maternal diabetes mellitus.
Hypernatraemia Hypernatraemia (serum Na >150 mmol/litre) commonly occurs as a result of excessive water loss, restricted water intake or an inability to respond to thirst. It may also occur in infants given incorrectly made feeds. Hypernatraemia can be fatal. Signs of hypernatraemia are more severe when it develops rapidly or when the serum Na is >160 mmol/litre. Chronic hypernatraemia is often well tolerated because of cerebral compensation. The true degree of dehydration is often underestimated if clinical signs alone are used compared to loss of weight. Intravascular volume is often well preserved during the initial stages. The management of hypernatraemic dehydration consists of initial volume replacement with 0.9% sodium chloride given in boluses of 20 ml/kg to restore normovolaemia. Complete correction should then be done very slowly over at least 48 hours to prevent cerebral oedema, seizures and brain injury. The serum Na should be corrected at a reduction of no more than 12 mmol/litre/day with 0.45% sodium chloride or 0.9% sodium chloride in glucose. In hypernatraemic dehydration it is important to give maintenance fluid alongside fluid to correct dehydration.
Pyloric stenosis: hypochloraemia correction Children with pyloric stenosis typically present with a mild hypochloraemic alkalotic dehydration. Resuscitation can be based on the serum chloride in most children. Calculate the chloride deficit and replace over 12e48 hours depending on severity. Chloride deficit ¼ 2=3 weight ðkgÞ 110 Cl : Use 0.9% saline 0.15% Kþ (170 mmol Cl/litre) or 0.45% saline, 5% glucose 0.15% Kþ (95 mmol Cl/litre).
Potassium imbalance Hypokalaemia (serum K <3.5 mmol/litre) produces symptoms of cramp, arrhythmias, reduced cardiac contractility and paralytic ileus. If possible oral supplements of 3e5 mmol/kg/ day should be given. Orange juice and bananas are rich in potassium. In severe hypokalaemia (serum K <3 mmol/litre), intravenous correction should be no faster than 0.25 mmol/kg/hour using a maximum peripheral concentration of 40 mmol/litre KCl (as per British National Formulary for Children). For a more rapid correction, the patient should be in PICU and the infusion administered via a central line. Hyperkalaemia (serum K >5.5 mmol/litre) causes skeletal muscle weakness and electrocardiography (ECG) changes when serum K >7 mmol/litre. Immediate treatment of hyperkalaemia is to antagonize membrane effects by giving 100 mg/kg of 10% calcium gluconate. This equates to 0.5 ml/kg of a 10% solution (1 ml 10% calcium gluconate contains 0.22 mmol calcium) Advanced Paediatric Life Support (APLS) recommendation). Alongside this it is important to increase intracellular shift of potassium by giving 1e2 mmol/kg of sodium bicarbonate, an
SURGERY 28:8
Example: a 3.3-kg child is mildly dehydrated with a Cl of 85 mmol/litre: deficit ¼ 2=3 3:3 ð110 85Þ ¼ 55 mmol Cl This is contained in 55/170 ¼ 325 ml of 0.9% saline with 0.15% Kþ. If this fluid is given at 180 ml/kg/day ¼ 25 ml/hour, the child will receive 55 mmol Cl in 13 hours. Alternatively if 0.45% saline, with 5% glucose and 0.15% Kþ is used at 180 ml/kg/day, they will receive 55 mmol in 23 hours. If the serum chloride is then remeasured and the bicarbonate checked, they will most likely be corrected. When corrected use appropriate maintenance fluids, but continue to replace nasogastric losses with 0.9% saline 0.15% Kþ.
Summary Great care and respect should be given to intravenous fluid management. It is important to understand the basic science, the risks and now the national guidelines which have been outlined here and expanded with other consensus statements. A 372
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