Intravenous Fluid Therapy in Sick Children
Somashekhar M Nimbalkar
Satvik C Bansal
Intravenous administration of fluids is perhaps the most common treatment provided in the hospitals for various indications. Fluids may be used for maintenance, concurrent replacement and deficit replacement. Understanding of certain basic principles relating to the body composition, behaviour of fluids and electrolytes in the body and composition of available intravenous fluids is a basic prerequisite. Parenteral fluid administration can be life-saving; however, if used incorrectly it can lead to development of avoidable complications such as iatrogenic hyponatremia and cerebral oedema. Type of fluid administered varies with the condition of the patient. Each situation demands an individualized approach with proper assessment and monitoring- clinical signs and laboratory tests. Updated education on intravenous fluid prescription is needed. This article discusses the basic physiology and evolution of our understanding of fluid administration and consensus regarding fluid administration as maintenance therapy and in certain commonly faced situations.
Children require intravenous (IV) fluids for various indications and at various ages. IV fluids may be used for maintenance, concurrent replacement and deficit replacement. IV fluids may be administered to children for maintenance only when neither volume deficits nor continuing losses are ascertained (e.g., a child waiting for an operative procedure and required to be nil by mouth (NBM)). A child may require concurrent replacement therapy if he has continuing losses due to drain from stomach (NG losses) or high urine output due to nephrogenic diabetes insipidus. Deficit replacement therapy may be required when a child is suffering from dehydration due to diarrhea [1-3]. Thus the amount of IV fluids prescribed can vary due to age, clinical condition on presentation and the underlying pathophysiology. This article serves to give broad guidelines on selecting IV fluids on a general basis and also in some common conditions, but in an individual patient various factors as outlined above need to be considered before prescribing IV fluids. This article does not refer to neonatal age group. Regular monitoring is necessary as diseases are dynamic and fluid requirements can change. Thus clinical signs, weight, urine output and laboratory tests such as electrolytes may need to be evaluated regularly. Prescribing IV fluids therapy requires knowledge of body water and electrolyte composition, requirements of fluids, ability to recognize dehydration and over-hydration and the types of solutions available.
Body Water: Body fluids are present in two compartments–the Intracellular fluids (ICF) (40%) and the Extracellular fluids (ECF). The ECF is further divided into plasma (5% of Total Body Weight (TBW)) and interstitial fluid. The proportion of TBW decreases from 75% in a term neonate to 60% in an adult (Table 1 & Table 2). Thus large changes of body weight in younger infants suggest relatively larger changes in TBW as compared to older children or adults.
Malnourished children may have increased TBW (up to 80%) as compared to obese children where there is a reduction in TBW [5, 6]. This assumes clinical importance as dehydration severity may be underestimated in obese children and nutritional wasting in malnutrition may be confused with dehydration .
Maintenance Fluids: Maintenance fluids are those that replenish deficit due to normal loss of fluids through urine, sweat, lungs and feces with the underlying assumption that there is no fluid deficit or on-going losses. This is calculated as per Holliday Segar method (published in 1957 in Pediatrics) as per the following equation:
- For body weight
- From 0 to 10 kg at 100 ml/kg/day,
- From 11 to 20 kg at 1000 ml + 50 ml/kg for every kilogram over 10 kg.
- Over 20 kg, it is 1500 ml + 20 ml/kg for every kg over 20 kg.
These guidelines are to be employed in children who are not seriously ill and it represents the fluid trequired to excrete the daily production of nitrogenous waste the body produces as urine. Any seriously ill child requiring IV fluids is at risk of inappropriate ADH secretion. Conditions such as bronchiolitis, meningitis, pneumonia, encephalitis, perioperative states, nausea, vomiting and burns result in reduced free water secretion. In these patients if there are no deficits to be corrected IV fluids should be used at 70% of maintenance fluid volume and in the form of isotonic saline or ringer’s lactate.
What maintenance fluids are appropriate?
For many years the maintenance fluids that have been used in children have been hypotonic 0.2% NaCl with 5% dextrose. These were essentially the recommendations made by Holliday and Segar. However these recommendations had never been evaluated in clinical trials and the recommendations were based on the best judgement and science available at that time. The recommendations for the amount of intravenous fluids in children have stood the test of time but the type of maintenance fluid that needs to be prescribed has undergone changes. In 1992 in a paper published in BMJ by Arieff et al showed how 16 healthy children died during hospitalization for minor operative surgery. They demonstrated severe hyponatremia as the cause for the deaths and since then multiple case reports and trials have emerged which have substantiated the need for change in the choice of maintenance fluids . Most conditions which cause secretion of ADH will result in free water retention and hence giving fluids with electrolyte free water results in dilution of electrolytes in the ECF. The electrolyte with major presence in the ECF is sodium and hence hyponatremia is a common finding in these situations. As seen from Table 3, 5% dextrose and 5% dextrose with 0.2% NaCl (the most commonly used maintenance solution as Isolyte P, Pedialyte P, etc) have the most electrolyte free water available. The maintenance fluids that are recommended are 0.9% NaCl or 0.45% NaCl with the addition of 20 meq/L of potassium. The choice between these fluids depends upon the expectation of SIADH in the concerned case. 5% Dextrose with 0.9% NaCl or with 0.45% NaCl may be used if maintenance fluids are required for longer duration. However the added dextrose provides only about 20% of the caloric requirements and avoids starvation ketosis. If prolonged IV therapy is anticipated then total parenteral nutrition (TPN) is indicated.
If a child is on oral fluid intake in addition to intravenous fluids then that also needs to be considered while deciding on the intravenous fluid to be used as most oral solutions are hypotonic and can contribute to hyponatremia. Similar is the case with fluids used in total parenteral nutrition (TPN). Children with renal failure, cardiac failure and hepatic failure with ascites have chronic hyponatremia due to water retention and/or abnormalities of the renin- angiotensin mechanism. They are not at risk for cerebral oedema but attempts to rapidly correct this can lead to osmotic demyelination. If serum electrolytes are known before starting therapy then it can be a guide as given in Table 4.
Patients who receive more than 50% of their maintenance fluid by the intravenous route should have daily glucose & electrolyte, daily intake & output and daily weight measured.
Evidence Base for the Change:
Following the report in BMJ (1992) which described 16 cases of deaths in children due to hyponatremia, there were various publications of case reports of hyponatremia in relatively healthy children admitted to hospitals developing hyponatremia due to infusion of hypotonic solutions. Halberthal et al from Ontario reviewed 306 cases of hyponatremia over a period of 10 years and reviewed 30 cases of acute hyponatremia. Of these 13 were postoperative while 15 were referred from wards and all of them received hypotonic fluids. The study warned against using hypotonic fluids given the unpredictability of inappropriate ADH secretion and also suggested evaluating electrolytes before starting intravenous fluids. In 2003 Duke et al and Moritz et al put forward arguments against the use of hypotonic fluids and the lack of evidence for the same. These arguments were based on case reports published previously and a few studies in adults and children. In 2004 Hoorn et al in an observation study of 1586 patients presenting to the hospital over a three month period documented hyponatremia in 131 patients. Thirty five patients developed hyponatremia after presentation while 5 had hyponatremia at presentation which improved with therapy but who again developed hyponatremia on maintenance fluids. Patients developed hyponatremia because they received electrolyte free water (EFW) either intravenously (66%) in form of maintenance fluids or orally. In 2006 Choong et al published a systematic review of 6 trials in a total of 404 patients and pointed that the evidence in favour of using hypotonic fluids which had been the standard of care for more than half a century was poor. They pointed out that hypotonic fluids were potentially dangerous as the odds of developing hyponatremia following hypotonic fluids was 17.2 times greater than with isotonic fluids. The numbers needed to harm (NNH) is 2 (C.I. 2 to 3) for hypotonic fluids using a random effects model, which means that every second patient is likely to develop hyponatremia following infusion of hypotonic maintenance fluids. In 2008 a randomized control trial involving 122 paediatric patients, it was observed that the use of hypotonic fluids increased the risk of hyponatremia at 24 hours as compared to isotonic fluids with a NNH of 7 and there was no significant increase in adverse events with isotonic fluids. In a small double blind randomized trial conducted on 50 patients in Australia, there was a greater fall in sodium in the group receiving 0.18% NS and 4% dextrose versus those receiving 0.9% NaCl. In the UK, after the implementation of the National Patient Safety Alert 22 in an audit over two months in 100 patients, there was a reduction of use of 0.18% NaCl with 5% dextrose no patient who received 0.45% of 0.9% NS became hyponatremic or hypernatremic. There was however less than acceptable monitoring of electrolytes of patients on IV fluids. Neville et al demonstrated in a randomized trial that children receiving 0.9% isotonic saline at 100% maintenance rate did not develop hyponatremia or hypernatremia but there was a higher incidence of hyponatremia in those children receiving 0.45% NaCl whether at 50% or 100% of maintenance rate. In fact the group receiving 0.9% NaCl at 50% of maintenance had episodes of hypernatremia. In a randomized control trial in postoperative pediatric patients, Hartmanns Solution (Sodium-131 mmol/L, Chloride – 111 mmol/L, Lactate -29 mmol/L, Potassium – 5 mmol/L and Calciumion – 2 mmol/L) at full maintenance rate did not produce hyponatremia as compared to children receiving 0.45% NaCl and 5% Dextrose. Hartmann’s Solution is very similar to lactated ringer’s solution which is available in our country. In a similar randomized trial conducted on 258 postoperative pediatric patients, isotonic fluids were significantly safer than hypotonic fluids with 6 patients required to be treated with isotonic fluids to prevent one episode of hyponatremia. Several other studies conducted in Argentina, India, Spain and Canada also support the use of isotonic fluids as maintenance fluids.
IV Fluids in special scenarios:
Acute gastroenteritis in children requires hospitalization following severe dehydration, severe vomiting, severe diarrhoea, etc. Most indications requiring hospitalization usually require intravenous therapy.
- Intravenous fluid therapy in gastroenteritis comprises of three components.
- Firstly restoration of intravascular volume and management of shock by giving fluid boluses;
- Secondly fluid administration to correct dehydration and electrolytes lost by the child before presentation and
Finally administration of maintenance fluid therapy during the management. On-going losses are also to be considered in the calculation of fluids.
Type of Fluids: For restoration of fluid volume Normal Saline (NS) i.e. 0.9% NaCl or Ringer’s Lactate can be used with some preferring Ringer’s Lactate in malnourished children. For fluid deficit replacement and maintenance, the National Institute of Clinical Excellence of the UK recommends isotonic solution such as Normal Saline in 5% Dextrose. WHO recommends Ringer’s Lactate Solution with 5% dextrose as the preferred solution, followed by either Ringer’s Lactate Solution (Hartmann’s Solution for injection) or Normal Saline.
If shock is suspected give rapid infusion of 20 ml/kg of 0.9% NaCl solution. Repeat this if the child remains in shock. Once the shock subsides, give isotonic fluid for fluid deficit replacement and maintenance.
Children who can drink, even poorly, should receive oral rehydration solution (ORS) by mouth even if the IV fluids are running. The ORS fluids provide base and potassium. The WHO guidelines for severe dehydration indicate 100 ml/kg of ringer’s lactate to be given in intravenous treatment protocol as given in table 5.
After six hours (in infants) or three hours (in older patients) the patient needs to be reassessed and treated accordingly.
Newer methods of using rapid IV therapy at about 50-60 ml/kg of saline in an hour are considered experimental and probably offer no benefit and should be used with caution. Additionally in malnourished children it may be difficult to ascertain degree of dehydration and/or septic shock and hence fluid therapy should be given slowly especially as the Fluid Expansion as Supportive Therapy (FEAST) trial in Africa has shown worse outcomes of rapid IV therapy in septic shock.
Fluid Deficit: Dehydration should be assessed based on clinical findings and IV fluids are calculated accordingly. Dehydration is estimated to be 5% if there is reduced skin elasticity, dry mucous membranes, tachycardia, deep breathing and 10% if there are sunken eyes and capillary filling time is more than 3 seconds. Most calculations are based on a deficit of 10% but it is usually an overestimate.
Children who are severely volume depleted but not in shock should receive 0.9% NaCl at the rate of 10 ml/kg/h over 1-2 hours which may be repeated to ensure stable circulatory status. In those with shock 0.9% saline at 20 ml/kg should be given as a bolus as quickly as possible. Repeat if necessary after reassessment. The initial bolus re expansion should never be more than 40 ml/kg of the total fluid requirement in the first 4 hours of management. For the initial 4-6 hours deficit replacement should be done with 0.9% saline. Following this the deficit replacement should be with 0.9 % or 0.45% NaCl depending on corrected serum sodium (Table 6), with added potassium (chloride, phosphate or acetate salt). The corrected serum sodium and active osmolality should be routinely monitored. If corrected, serum sodium falls or fails to rise and active osmolality falls (should not fall >0.5 mOsm/kg/ hr), it indicates excess free water administration. As the blood glucose falls to 14 mmol/l or below, glucose can be added to the IV fluid, two bag system can be used. Rate of rehydration should be such that it is evenly spaced over 48 hours.
The fluid calculations are done on maintenance fluid added to deficit (usually 8 %) minus the fluid already given. This is given over 48 hours. The average weight and fluid rate are given in table 7.
The maintenance requirements as defined by the British Society for Paediatric Endocrinology and Diabetes (BSPED) guidelines are given in table 8.
Fluids should be rarely given in excess of 1.5-2 times the usual daily maintenance requirement. Urinary losses should not be routinely added. If oral fluid is given then the IV fluid may be reduced appropriately. Oral intake should usually begin within 24 hours of starting treatment. IV fluids can be stopped 1-2 hours after consumption of adequate oral fluids without vomiting.
Initial resuscitation of septic shock begins with infusion of isotonic crystalloids or albumin, with boluses of up to 20 mL/kg for crystalloids (or albumin equivalent) over 5–10 min. These should be titrated to reversing hypotension, increasing urine output, and attaining normal capillary refill, peripheral pulses and level of consciousness without inducing hepatomegaly or rales. If hepatomegaly or rales develop, inotropic support should be implemented, not fluid resuscitation. In children with severe hemolytic anemia (severe malaria or sickle cell crises) who are not hypotensive, blood transfusion is considered superior to crystalloid or albumin boluses. Children normally have a lower blood pressure than adults, and a fall in blood pressure can be prevented by vasoconstriction and increasing heart rate. Therefore, blood pressure alone is not a reliable endpoint for assessing the adequacy of resuscitation. However, once hypotension occurs, cardiovascular collapse may soon follow. Thus, fluid resuscitation is recommended for both normotensive and hypotensive children in septic shock. In the absence of signs of fluid overload, large fluid deficits can exist, and initial volume resuscitation can require 40–60 mL/kg or more; however, if these signs are present, then fluid administration should be ceased and diuretics should be given. Inotrope infusions and mechanical ventilation are commonly required for children with fluid refractory shock.
Conclusion: There is emerging evidence to substantiate the use of 0.9% NaCl as a maintenance fluid in children above the age of 1 month until 18 years of age. It is also essential to monitor electrolytes on a daily basis to detect early electrolyte abnormalities in those patients who receive more than 50% of their daily requirement by the intravenous route.
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