Isotonic is better than hypotonic saline for intravenous rehydration of children with gastroenteritis: a prospective randomised study

A randomized controlled trial of isotonic versus hypotonic maintenance intravenous fluids in hospitalized children

Background

Isotonic saline has been proposed as a safer alternative to traditional hypotonic solutions for intravenous (IV) maintenance fluids to prevent hyponatremia. However, the optimal tonicity of maintenance intravenous fluids in hospitalized children has not been determined. The objective of this study was to estimate and compare the rates of change in serum sodium ([Na]) for patients administered either hypotonic or isotonic IV fluids for maintenance needs.

Methods

This was a masked controlled trial. Randomization was stratified by admission type: medical patients and post-operative surgical patients, aged 3 months to 18 years, who required IV fluids for at least 8 hours. Patients were randomized to receive either 0.45% or 0.9% saline in 5.0% dextrose. Treating physicians used the study fluid for maintenance; infusion rate and the use of additional fluids were left to their discretion.

Results

Sixteen children were randomized to 0.9% saline and 21 to 0.45% saline. Baseline characteristics, duration (average of 12 hours) and rate of study fluid infusion, and the volume of additional isotonic fluids given were similar for the two groups. [Na] increased significantly in the 0.9% group (+0.20 mmol/L/h [IQR +0.03, +0.4]; P = 0.02) and increased, but not significantly, in the 0.45% group (+0.08 mmol/L/h [IQR -0.15, +0.16]; P = 0.07). The rate of change and absolute change in serum [Na] did not differ significantly between groups.

Conclusions

When administered at the appropriate maintenance rate and accompanied by adequate volume expansion with isotonic fluids, 0.45% saline did not result in a drop in serum sodium during the first 12 hours of fluid therapy in children without severe baseline hyponatremia. Confirmation in a larger study is strongly recommended.

Clinical Trial Registration Number

NCT00457873 (http://www.clinicaltrials.gov/)

Dental hyponatraemia

A 14-year-old girl developed dental pain and was treated for acute infected pulpitis of her right upper lateral incisor with drilling and filling. The pain continued and was helped by analgesia, sucking ice cubes and drinking cold water. Forty-eight hours later, she became confused and disoriented. She started to vomit and complained of headache. Investigations revealed hyponatraemia with normal serum potassium levels and initially normal urinary sodium excretion. Over the next 24 hours, she passed 5.45 L of urine and her serum sodium rose from 125 to 143 mmol/L. Self-induced water intoxication has been described during drinking games and initiation ceremonies, but this would appear to an unusual cause. Conservative management proved successful in allowing this girl to recover without sequelae.

Hypotonic versus isotonic maintenance fluids in critically ill children: a multicenter prospective randomized study

AIM

Study the influence of hypotonic (HT) and isotonic (IT) maintenance fluids in the incidence of dysnatraemias in critically ill children.

METHODS

Prospective, randomized study conducted in three paediatric intensive care units (PICU). One hundred and twenty-five children requiring maintenance fluid therapy were included: 62 received HT fluids (50-70 mmol/L tonicity) and 63 IT fluids (156 mmol/L tonicity). Age, weight, cause of admission, sodium and fluid intake, and diuresis were collected. Blood electrolytes were measured on admission, 12 and 24 h later.

RESULTS

Blood sodium levels at 12 h were 133.7±2.7 mmol/L in HT group vs. 136.8±3.5 mmol/L in IT group (p=0.001). Adjusted for age, weight and sodium level at PICU admission, the blood sodium values of patients receiving HT fluids decrease by 3.22 mmol/L (CI: 4.29/2.15)(p=0.000). Adjusted for age, weight and hyponatraemia incidence at admission, patients receiving HT fluids increased the risk of hyponatraemia by 5.8-fold (CI: 2.4-14.0) during the study period (p=0.000).

CONCLUSIONS

Hypotonic maintenance fluids increase the incidence of hyponatraemia because they decrease blood sodium levels in normonatraemic patients. IT maintenance fluids do not increase the incidence of dysnatraemias and should be considered as the standard maintenance fluids.

Iatrogenic hyponatremia in hospitalized children: Can it be avoided?

Iatrogenic hyponatremia in hospitalized children is a common problem. It is usually caused by the administration of free water, either orally or through the prescription of hypotonic intravenous fluids. It can result in cerebral edema and death, and is most commonly reported in healthy children undergoing minor surgery. The current teachings and practical guidelines for maintenance fluid infusions are based on caloric expenditure data in healthy children that were derived and published more than 50 years ago. A re-evaluation of these data and more recent recognition that hospitalized children are vulnerable to hyponatremia, with its resulting morbidity and mortality rates, suggest that changes in paediatricians' approach to fluid administration are necessary. There is no single fluid therapy that is optimal for all hospitalized children. A thorough assessment of the type of fluid, volume of fluid and electrolyte requirements based on individual patient requirements, plus rigorous monitoring, is required in any child receiving intravenous fluids. The present article reviews how hyponatremia occurs and makes recommendations for minimizing the risk of iatrogenic hyponatremia.

Pediatric rapid fluid resuscitation

PURPOSE OF REVIEW

Intravenous and enteral fluid resuscitation are frequently used therapies in the management of pediatric patients in emergency departments and critical care settings. Any state of intravascular fluid deficit, ranging from mild dehydration due to gastroenteritis to fulminant septic shock, requires careful assessment and early restoration of hemodynamic stability. Rapid fluid resuscitation has gained increased recognition since the most recent pediatric shock management guidelines. We sought to review the evidence for rapid fluid resuscitation and to outline its clinical indications, implementation, and potential associated risks.

RECENT FINDINGS

Rapid fluid resuscitation benefits pediatric patients with severe dehydration or signs of shock. Studies have proven the modality to be safe and efficacious and to reduce morbidity and mortality. Initial and frequent clinical assessments are key in reducing potential complications of overhydration or clinically significant electrolyte disturbances. Rapid enteral rehydration may be used in the uncomplicated, mildly to moderately dehydrated patient. Antiemetics may facilitate rehydration efforts by limiting further fluid losses.

SUMMARY

Rapid fluid resuscitation is most commonly used for children with moderate-to-severe dehydration, or for patients in shock to restore circulation. Concerns regarding potential for fluid overload and electrolyte disturbances and regarding the method of rehydration (i.e., enteral versus parenteral) raise some debate about the safety and efficacy of rapid fluid resuscitation in the pediatric patient. Recent studies show that early, aggressive fluid resuscitation of up to 60 ml/kg within 1-2 h may be necessary to replenish circulating intravascular fluid volume. Complications of severe electrolyte disturbances, cerebral edema, or uncontrolled hemorrhage are uncommon and can often be avoided with early clinical assessment and reassessments throughout the resuscitation. In the mildly to moderately dehydrated child, enteral fluid resuscitation with the aid of an antiemetic such as ondansetron can be as effective and efficient as intravenous fluid resuscitation.

[Infusion therapy for neonates, infants and children]

Intravenous administration of fluids, electrolytes and glucose are the most common interventions in hospitalized pediatric patients. Parenteral fluid administration can be life-saving, however, if used incorrectly it also carries substantial risks. Perioperatively, adequate hydration, prevention of electrolyte imbalances and maintenance of normoglycemia are the main goals of parenteral fluid therapy. Conceptionally, the distinction between maintenance requirements, deficits and ongoing loss is helpful. Although the pathophysiological basis for parenteral fluid therapy was clarified in the first half of the 20th century, some aspects still remain controversial. In newborn infants, rational parenteral fluid therapy must take into account large insensible fluid losses, adaptive changes of renal function in the first days of life and the fact that neonates do not tolerate prolonged periods of fasting. In older infants the occurrence of iatrogenic hyponatremia with the use of hypotonic solutions has led to a critical reappraisal of the validity of the Holliday-Segar method for calculating maintenance fluid requirements in the postoperative period. Pragmatically, only isotonic solutions should be used in clinical situations which are known to be associated with increases in antidiuretic hormone (ADH) secretion. In this context, it is important to realize that in contrast to lactated Ringer's solution, the use of normal saline can lead to hyperchloremic acidosis in a dose-dependent fashion. Although there is no convincing evidence that colloids are better than crystalloids, there are clinical situations where the use of the more expensive colloids seems justified. It may be reasonable to choose a solution for fluid replacement which has a composition comparable to the composition of the fluid which must be replaced. Although hypertonic saline can reduce an elevated intracranial pressure, this therapy cannot be recommended as a routine procedure because there is currently no evidence that this intervention improves long-term outcome in pediatric patients with traumatic brain injury.

Intravenous fluid management for the acutely ill child

PURPOSE OF REVIEW

To review the principles of prescribing intravenous fluids (IVFs) to the acutely ill child and of adjusting sodium composition and fluid rate to prevent disorders in serum sodium or volume status from occurring.

RECENT FINDINGS

Recent data have revealed that the historic approach of administering hypotonic IVFs results in a high incidence of hospital-acquired hyponatremia in children. The majority of hospitalized children requiring IVFs are at risk for developing hyponatremia from numerous stimuli for arginine vasopressin (AVP) production, such as volume depletion, pain, stress, nausea, vomiting, respiratory or central nervous system (CNS) disorders, or the postoperative state. Multiple recent prospective studies in over 600 children have demonstrated that hypotonic fluids cause acute hyponatremia, whereas 0.9% sodium chloride (NaCl) effectively prevents it. 0.9% NaCl is the most appropriate IVF for the majority of hospitalized children. Fluid and sodium restriction will be needed for children with edematous or oliguric states and hypotonic fluids needed for children with urinary or extra-renal free water losses or hypernatremia.

SUMMARY

Hypotonic fluids should not be administered routinely in children due to the risk of hospital-acquired hyponatremia. 0.9% NaCl is the preferred IVF for the vast majority of hospitalized children.

Intravenous fluid regimen and hyponatraemia among children: a randomized controlled trial

The aim of this study was to compare the effect of three different intravenous (i.v.) fluid regimes on the incidence of hyponatraemia in hospitalized children ranging in age from 3 months to 12 years. Children who required the administration of i.v. maintenance fluid for at least 24 h following hospitalization were eligible for inclusion. The children were randomized to three i.v. fluid groups: Group A, 0.9% saline in 5% dextrose at the standard maintenance rate; Group B, 0.18% saline in 5% dextrose at the standard maintenance rate; Group C, 0.18% saline in 5% dextrose at two-thirds of the standard maintenance rate. The primary outcome measure was incidence of hyponatraemia (plasma sodium < 130 mEq/L). Of the 167 patients enrolled, 58, 56 and 53 patients were randomized to Group A, B and C, respectively. We observed that 14.3% (8/56) of the children administered 0.18% saline in 5% dextrose at the standard maintenance rate (Group B) developed hyponatraemia compared with 1.72% of the children in Group A and 3.8% of those in Group C. Based on these results, we conclude that the administration of 0.9% saline in 5% dextrose as i.v. maintenance fluid helps in reducing the incidence of hospital-acquired hyponatraemia among children.

Incidence of hyponatremia in children with gastroenteritis treated with hypotonic intravenous fluids

Hypotonic saline solutions have been used for over five decades to treat children with diarrheal dehydration. However, concern has recently been raised about the potential for iatrogenic hyponatremia as a result of this therapy. We reviewed the medical records of 531 otherwise healthy children with gastroenteritis who had been admitted to the hospital for intravenous fluid therapy. We retrospectively collected data on 141 of these children who had received two serum electrolytes (one upon admission and the other 4-24 h thereafter). The remaining 390 children were excluded because their charts lacked the required data. We analyzed data in 124 of these 141 patients whose initial serum sodium (Na) level was between 130-150 mEq/l and excluded 17 patients whose admission serum sodium fell outside this range. All patients were treated with intravenous hypotonic fluids (5% dextrose in 0.2% saline, n = 4; 5% dextrose in 0.3% saline, n = 102; 5% dextrose in 0.45% saline, n = 18 patients) as maintenance fluid therapy or maintenance fluid plus deficit therapy; 100 of these children had received an initial saline bolus of 21.05 +/- 8.5 ml/kg upon admission. The serum Na level decreased by 1.7 +/- 4.3 mEq/l in the whole group. Of the 97 children with isonatremia (Na 139.5 +/- 2.7 mEq/l) on admission, 18 (18.5%) developed mild hyponatremia (Na 133.4 +/- 0.9 mEq/l, range 131-134), with a decrease in serum Na of 5.7 +/- 3.1 mEq/l, and 79 remained isonatremic (Na 138.3 +/- 2.7 mEq/l), with a decrease in serum Na of 1.8 +/- 3.4 mEq/l (p < 0.0005). There was no significant difference in type, rate, or amount of intravenous fluid or saline bolus (26.1 +/- 10.4 vs. 20.2 +/- 8.6 ml/kg, respectively) administered in these two groups. Children who became hyponatremic were older (5.8 +/- 2.7 years) than those who remained isonatremic (2.8 +/- 3.1 years) (p < 0.0005), but there was no statistical difference in gender, degree of dehydration, and severity of metabolic acidosis between the two groups. Although serum Na increased by 3.9 +/- 2.5 mEq/l in 19 patients with mild hyponatremia upon admission (Na 132.8 +/- 1.3 to 136.7 +/- 2.6 mEq/l) and 73% of these became isonatremic, hypotonic saline solutions have the potential to cause hyponatremia in children with gastroenteritis and isonatremic dehydration.

New aspects in the pathogenesis, prevention, and treatment of hyponatremic encephalopathy in children

Hyponatremia is the most common electrolyte abnormality encountered in children. In the past decade, new advances have been made in understanding the pathogenesis of hyponatremic encephalopathy and in its prevention and treatment. Recent data have determined that hyponatremia is a more serious condition than previously believed. It is a major comorbidity factor for a variety of illnesses, and subtle neurological findings are common. It has now become apparent that the majority of hospital-acquired hyponatremia in children is iatrogenic and due in large part to the administration of hypotonic fluids to patients with elevated arginine vasopressin levels. Recent prospective studies have demonstrated that administration of 0.9% sodium chloride in maintenance fluids can prevent the development of hyponatremia. Risk factors, such as hypoxia and central nervous system (CNS) involvement, have been identified for the development of hyponatremic encephalopathy, which can lead to neurologic injury at mildly hyponatremic values. It has also become apparent that both children and adult patients are dying from symptomatic hyponatremia due to inadequate therapy. We have proposed the use of intermittent intravenous bolus therapy with 3% sodium chloride, 2 cc/kg with a maximum of 100 cc, to rapidly reverse CNS symptoms and at the same time avoid the possibility of overcorrection of hyponatremia. In this review, we discuss how to recognize patients at risk for inadvertent overcorrection of hyponatremia and what measures should taken to prevent this, including the judicious use of 1-desamino-8d-arginine vasopressin (dDAVP).

Prevention of hyponatremia during maintenance intravenous fluid administration: a prospective randomized study of fluid type versus fluid rate

OBJECTIVES

To determine the importance of sodium content versus administration rate of intravenous fluids in the development of hyponatremia in postoperative children.

STUDY DESIGN

In this prospective, randomized, nonblinded study, 124 children admitted for surgery received 0.9% (NS) or 0.45% (N/2) saline solution at 100% or 50% maintenance rates. Plasma electrolytes, osmolality, and ADH at induction of anesthesia were compared with values 8 hours (T(8)), and 24 hours (T(24); n = 67) after surgery. Blood glucose and ketones were measured every 4 hours. Electrolytes and osmolality were measured in urine samples.

RESULTS

Plasma sodium concentrations fell in both N/2 groups at T(8) (100%: -1.5 +/- 2.3 mmol/L 50%: -1.9 +/- 2.0 mmol/L; P < .01) with hyponatremia more common than in the NS groups at T(8) (30% vs 10%; P = .02) but not T(24). Median plasma antidiuretic hormone concentrations increased 2- to 4-fold during surgery (P < or = .001) and only reattained levels at induction of anesthesia by T(24) in the N/2 100% group. On multiple linear regression analysis, fluid type, not rate determined risk of hyponatremia (P < .04). Two children on 100% developed SIADH (1NS). Fourteen (23%; 7NS) on 50% maintenance were assessed as dehydrated. Dextrose content was increased in 18 for hypoglycemia or ketosis.

CONCLUSIONS

The risk of hyponatremia was decreased by isotonic saline solution but not fluid restriction.

Acute and persistent diarrhea

Socially disadvantaged Indigenous infants and children living in western industrialized countries experience high rates of infectious diarrhea, no more so than Aboriginal children from remote and rural regions of Northern Australia. Diarrheal disease, poor nutrition, and intestinal enteropathy reflect household crowding, inadequate water and poor sanitation and hygiene. Acute episodes of watery diarrhea are often best managed by oral glucose-electrolyte solutions with continuation of breastfeeding and early reintroduction of feeding. Selective use of lactose-free milk formula, short-term zinc supplementation and antibiotics may be necessary for ill children with poor nutrition, persistent symptoms, or dysentery. Education, high standards of environmental hygiene, breastfeeding, and immunization with newly licensed rotavirus vaccines are all needed to reduce the unacceptably high burden of diarrheal disease encountered in young children from Indigenous communities.

Randomised controlled trial of intravenous maintenance fluids

AIM

Traditional paediatric intravenous maintenance fluids are prescribed using hypotonic fluids and the weight-based 4:2:1 formula for administration rate. However, this may cause hyponatraemia in sick and post-operative children. We studied the effect of two types of intravenous maintenance fluid and two administration rates on plasma sodium concentration in intensive care patients.

METHODS

A Factorial-design, double-blind, randomised controlled trial was used. We randomised 50 children with normal electrolytes without hypoglycaemia who needed intravenous maintenance fluids for >12 h to 0.9% saline (normal saline) or 4% dextrose and 0.18% saline (dextrose saline), at either the traditional maintenance fluid rate or 2/3 of that rate. The main outcome measure was change in plasma sodium from admission to 12-24 h later.

RESULTS

Fifty patients (37 surgical) were enrolled. Plasma sodium fell in all groups: mean fall 2.3 (standard deviation 4.0) mmol/L. Fluid type (P = 0.0063) but not rate (P = 0.12) was significantly associated with fall in plasma sodium. Dextrose saline produced a greater fall in plasma sodium than normal saline: difference 3.0, 95% confidence interval 0.8-5.1 mmol/L. Full maintenance rate produced a greater fall in plasma sodium than restricted rate, but the difference was small and non-significant: 1.6 (-0.7, 3.9) mmol/L. Fluid type, but not rate, remained significant after adjustment for surgical status. One patient, receiving normal saline at restricted rate, developed asymptomatic hypoglycaemia.

CONCLUSION

Sick and post-operative children given dextrose saline at traditional maintenance rates are at risk of hyponatraemia.

Rehydration: role for early use of intravenous dextrose

Acute gastroenteritis is a common reason for children to seek health care. Among the potential complications of acute gastroenteritis, the most common is dehydration. For mild to moderate dehydration, treatment options include oral and intravenous rehydration. Outpatient treatment failure for either method, when it occurs, is often due to persistent nausea and vomiting. Some authorities have suggested that the early administration of dextrose to patients receiving intravenous rehydration may help terminate vomiting and result in fewer outpatient treatment failures. The purpose of this report was to review the evidence supporting the effectiveness of early intravenous dextrose administration in the outpatient management of dehydration in children with acute gastroenteritis.

The use of isotonic fluid as maintenance therapy prevents iatrogenic hyponatremia in pediatrics: a randomized, controlled open study

OBJECTIVES

Hypotonic fluids are widely used in pediatrics. Several articles have reported the risk of iatrogenic hyponatremia secondary to this practice. We primarily intend to determine whether the use of isotonic fluids prevents hyponatremia and, secondly, whether these fluids increase the incidence of adverse events.

STUDY DESIGN

One hundred twenty-two pediatric patients hospitalized in intensive care unit requiring maintenance fluid therapy were randomized to receive isotonic fluids (isotonic group, NaCl = 140 mEq/L) or hypotonic fluids (hypotonic group, NaCl <100 mEq/L). Electrolyte blood concentration, glycaemia, and blood pressure were measured at 0, 6, and 24 hrs after the beginning of fluid therapy. Plasma creatinine, urine specific gravity, and urine electrolyte concentration were measured at 6 hrs. Standard intention-to-treat analysis and Bayesian analysis were conducted to assess the probability of hyponatremia and hypernatremia in each group.

RESULTS

At the time of admission to hospital, no differences in natremia or the percentage of hyponatremia were found between groups. At 24 hrs, the percentage of hyponatremia in the hypotonic group was 20.6% as opposed to 5.1% in the isotonic group (p = 0.02). No differences in the number of adverse events other than hyponatremia were observed between groups.

CONCLUSIONS

The use of hypotonic fluids increases the risk of hyponatremia when compared with isotonic fluids at 24 hrs following infusion (number needed to harm [confidence interval 95%] = 7[4;25]). In our sample, the use of isotonic fluids did not increase the incidence of adverse events compared with hypotonic fluids.

An audit of intravenous fluid prescribing and plasma electrolyte monitoring; a comparison with guidelines from the National Patient Safety Agency

OBJECTIVES

To audit past practice of intravenous (i.v.) fluid prescribing and electrolyte monitoring, prior to the publication of guidelines by the National Patient Safety Agency (NPSA, Ref. NPSA/2007/22) in March 2007, highlighting areas of discrepancy, in a specialist children's hospital.

METHODS

We performed a retrospective case note review of 100 appendectomy patients between February 2004 and March 2007, recording; fluid type and volumes given as maintenance therapy, resuscitation boluses and nasogastric replacement; the frequency and timing of plasma electrolyte measurement; the relationship between plasma sodium [Na] concentration and i.v. fluid prescribed; and patient weight recordings.

RESULTS

Ninety-eight acute appendectomies and two interval elective appendectomies. Median age 10 years (interquartile range: 8-11.25). Before surgery, hypotonic maintenance fluid was prescribed for 94% patients. During surgery, maintenance fluid was predominantly isotonic. After surgery, hypotonic maintenance fluid was prescribed for 92% patients. All maintenance fluid volumes were appropriately calculated according to weight using the Holliday and Segar formula (Paediatrics, 19, 1957, 823). Fluid boluses were isotonic on 128/129 occasions and all accurately calculated according to weight. Nasogastric losses were replaced with 0.9% sodium chloride. No patient had daily plasma electrolyte measurements whilst administered i.v. fluid. Twenty-seven patients had recorded hyponatremia ([Na] <135 mmol x l(-1); 21 at presentation, six subsequently after admission). Hypotonic maintenance fluid was continued in 26/27 patients with hyponatremia. No patient had daily weight recorded.

CONCLUSIONS

Our practice of i.v. fluid prescribing and electrolyte monitoring in children, prior to the publication of guidelines by the NPSA in March 2007, did not fully meet the recommended standards.

Maintenance fluid therapy: what it is and what it is not

Fifty years after the publication of a prescription for maintenance fluid therapy, concerns have been raised about the use of hypotonic fluids in hospitalized children. We discuss what maintenance fluid therapy is or what it is not; where maintenance fluid therapy has been misused. We also discuss concerns with the immediate adoption of isotonic fluid as maintenance fluid without careful consideration and testing.

Hypotonic versus isotonic maintenance intravenous fluid therapy in hospitalized children: a systematic review

A systematic review of studies comparing hypotonic versus isotonic intravenous maintenance fluids in hospitalized children was conducted to determine whether hypotonic solutions increase the risk of acute hyponatremia. Studies were identified from electronic databases and hand-searched reference lists. A total of 283 abstracts were reviewed, 55 full-text articles were retrieved, and 3 studies were included. All studies were observational and were overall inconclusive. All authors cautioned against the routine use of hypotonic maintenance fluids, but hypotonic fluid administration did not always explain the development of acute hyponatremia. Further evidence is required as to the appropriate maintenance solution for hospitalized children.

Hospital-acquired hyponatremia—why are hypotonic parenteral fluids still being used?

Hospital-acquired hyponatremia can be lethal. There have been multiple reports of death or permanent neurological impairment in both children and adults. The main factor contributing to the development of hospital-acquired hyponatremia is routine use of hypotonic fluids in patients in whom the excretion of free water, which is retained in response to excess arginine vasopressin (AVP), might be impaired. The practice of administering hypotonic parental fluids was established over 50 years ago, before recognition of the fact that there are numerous potential stimuli for AVP production in most hospitalized patients. Virtually all neurological morbidity resulting from hospital-acquired hyponatremia has been associated with administration of hypotonic fluids. Multiple prospective studies have shown that 0.9% NaCl is effective prophylaxis against hyponatremia. There is not a single report in the literature of neurological complications resulting from the use of 0.9% NaCl in non-neurosurgical patients. Patients at greatest risk of developing hyponatremic encephalopathy following hypotonic fluid administration are children, premenopausal females, postoperative patients, and those with brain injury or infection, pulmonary disease or hypoxemia. When hyponatremic encephalopathy develops, immediate administration of 3% NaCl is essential. In this Review, we discuss the question of why administering hypotonic fluids is unphysiologic and potentially dangerous, the settings in which isotonic fluids should be administered to prevent hyponatremia, and the appropriate treatment of hyponatremic encephalopathy.

Fluid therapy for children: facts, fashions and questions

Fluid therapy restores circulation by expanding extracellular fluid. However, a dispute has arisen regarding the nature of intravenous therapy for acutely ill children following the development of acute hyponatraemia from overuse of hypotonic saline. The foundation on which correct maintenance fluid therapy is built is examined and the difference between maintenance fluid therapy and restoration or replenishment fluid therapy for reduction in extracellular fluid volume is delineated. Changing practices and the basic physiology of extracellular fluid are discussed. Some propose changing the definition of "maintenance therapy" and recommend isotonic saline be used as maintenance and restoration therapy in undefined amounts leading to excess intravenous sodium chloride intake. Intravenous fluid therapy for children with volume depletion should first restore extracellular volume with measured infusions of isotonic saline followed by defined, appropriate maintenance therapy to replace physiological losses according to principles established 50 years ago.

Hypotonic versus isotonic saline in hospitalised children: a systematic review

BACKGROUND

The traditional recommendations which suggest that hypotonic intravenous (i.v.) maintenance fluids are the solutions of choice in paediatric patients have not been rigorously tested in clinical trials, and may not be appropriate for all children.

AIMS

To systematically review the evidence from studies evaluating the safety of administering hypotonic versus isotonic i.v. maintenance fluids in hospitalised children.

DATA SOURCES

Medline (1966-2006), Embase (1980-2006), the Cochrane Library, abstract proceedings, personal files, and reference lists. Studies that compared hypotonic to isotonic maintenance solutions in children were selected. Case reports and studies in neonates or patients with a pre-existing history of hyponatraemia were excluded.

RESULTS

Six studies met the selection criteria. A meta-analysis combining these studies showed that hypotonic solutions significantly increased the risk of developing acute hyponatraemia (OR 17.22; 95% CI 8.67 to 34.2), and resulted in greater patient morbidity.

CONCLUSIONS

The current practice of prescribing i.v. maintenance fluids in children is based on limited clinical experimental evidence from poorly and differently designed studies, where bias could possibly raise doubt about the results. They do not provide evidence for optimal fluid and electrolyte homoeostasis in hospitalised children. This systematic review indicates potential harm with hypotonic solutions in children, which can be anticipated and avoided with isotonic solutions. No single fluid rate or composition is ideal for all children. However, isotonic or near-isotonic solutions may be more physiological, and therefore a safer choice in the acute phase of illness and perioperative period.

Perioperative fluid therapy in children: a survey of current prescribing practice †

BACKGROUND

Fluid therapy in children may be associated with iatrogenic hyponatraemia. We surveyed anaesthetists' current fluid prescribing practice during the perioperative period, departmental fluid protocols and awareness of the concerns of the Royal College of Paediatrics and Child Health (RCPCH) about the use of dextrose 4%/saline 0.18% in children.

METHODS

Questionnaire survey of 477 consultant anaesthetists in two training areas in the UK.

RESULTS

Responses were received from 289 anaesthetists (60.6%)--responses from the 203 consultants that anaesthetized children were analysed. A total of 67.7% did not have a local departmental policy for fluid prescription, and 58.1% were unaware of the concerns of RCPCH. A total of 60.1% of anaesthetists said that they prescribed hypotonic dextrose saline solutions in the intraoperative period and 75.2% did so in the postoperative period. Anaesthetists working in specialist paediatric hospitals were 5.1 times more likely to prescribe isotonic fluids intraoperatively than those working in district hospitals (95% CI 1.48-17.65, P=0.01), but they all prescribed hypotonic dextrose saline solutions postoperatively. The Holliday and Segar formula for maintenance fluid was quoted by 81.8% of anaesthetists; only 5.9% of anaesthetists would restrict fluids in the immediate postoperative period. Anaesthetists working in specialist paediatric hospitals were 13.2 times more likely to restrict fluids postoperatively than those working in district hospitals (95% CI 2.8-61.8, P=0.001).

CONCLUSIONS

The prescription of hypotonic dextrose saline solutions by anaesthetists may be putting children at risk from iatrogenic hyponatraemia. Departmental protocols for perioperative fluid prescription in children are uncommon. We suggest that national guidance is required.

The maintenance need for water in parenteral fluid therapy

PURPOSE OF REVIEW

Maintenance fluid therapy represents the volume of fluids and amount of electrolytes and glucose needed to replace anticipated physiological losses from breath, sweat and urine and to prevent hypoglycaemia. For 50 years, this therapy was based on Holliday and Segar's formula, which proposed to match children's water and electrolyte requirements on a weight-based calculation using hypotonic solutions. Recent publications highlight the risk of hyponatraemia in the postoperative period and the facilitating role of a hypotonic infusion, leading some people to recommend replacing hypotonic with isotonic solutions.

RECENT FINDINGS

The postoperative period is at risk for nonosmotic secretion of antidiuretic hormone, which reduces the ability of the kidneys to excrete free water. In the context of antidiuretic hormone release, the associated low urine output makes maintenance volume requirement decrease to 50% of the calculated hourly rate. While isotonic fluids are recommended during anaesthesia, controversies still exist on the nature of fluid for maintenance therapy in the postoperative period. The proof for a benefit of isotonic fluids in this context is weak; further investigations are needed to make a decision. Whatever the choice, an individualized maintenance infusion protocol for each patient is necessary.

SUMMARY

As free water excretion is altered for all children in the postoperative period, it is necessary to reduce the volume of maintenance fluid therapy to half the previously recommended volume. The choice of an isotonic solution should be more pertinent to that of a hypotonic solution, but evidence is lacking for a definitive answer.