The role of bicarbonate and base precursors in treatment of acute gastroenteritis

Additional Bicarbonate Infusion Complements WHO Rehydration Therapy in Children with Acute Diarrhea and Severe Dehydration Presenting with Severe Non-anion Gap Metabolic Acidemia: An Open Label Randomized Trial

OBJECTIVES

To assess the efficacy and safety of bicarbonate infusion in children with Acute Diarrhea and Severe Dehydration (ADSD) having severe Non-Anion Gap Metabolic Acidemia (sNAGMA).

METHODS

Children (aged 1-144 mo) with ADSD and sNAGMA (pH ≤7.2 and/or serum bicarbonate ≤15 mEq/L) were enrolled in an open-label randomized design. Controls (n = 25) received WHO-recommended rehydration therapy with Ringer Lactate, while intervention group (n = 25) received additional bicarbonate deficit correction. Primary outcome was time taken to resolve metabolic acidemia (pH >7.30 and/or bicarbonate >15 mEq/L). Secondary outcome measures were adverse outcome [composite of pediatric intensive care unit (PICU) transfer and deaths], acute care area free days in 5 d (ACAFD5), hospital stay, and adverse effects.

RESULTS

Time taken to resolve metabolic acidemia was significantly lesser with intervention [median (IQR); 8 h (4, 12) vs. 12 h (8, 24); p = 0.0067]. Intervention led to acidemia resolution in significantly more children by 8 h and 16 h (17/25 vs. 9/25, p = 0.035 and 23/25 vs. 17/24, p = 0.018, respectively). Patients with fluid refractory shock needed lesser inotropes in intervention group [median Vasoactive Inotrope Score (VIS), 10.5 vs. 34]. Intervention led to significantly lesser adverse outcome (0/25 vs. 5/25, p = 0.049), and noticeably more ACAFD5 [median (IQR); 2 (1, 2) vs. 1 (1, 2); p = 0.12]. Two patients died in the control group while none in the intervention group. No adverse effect was documented.

CONCLUSIONS

Additional calculated dose of bicarbonate infusion led to significantly early resolution of metabolic acidemia, lesser utilization of critical care facilities, and lesser adverse outcome in children with ADSD and sNAGMA, compared to standard therapy, with no adverse effect.

Acute Diarrhea and Severe Dehydration in Children: Does Non-anion-gap Component of Severe Metabolic Acidemia Need More Attention?

Background

Despite significant loss of bicarbonate during acute diarrhea, pediatric data are scarce with acute diarrhea/severe dehydration (ADSD) and severe non-anion-gap metabolic acidemia (sNAGMA). We planned to study their clinical profile, critical care needs, and outcome.

Patients

Children (1 month-12 years) with ADSD and sNAGMA (pH <7.2 and/or bicarbonate <15 mEq/L, and normal/mixed anion gap) admitted in Pediatric Emergency Department from January 2016 to December 2018 were enrolled. Children with pure high-anion-gap metabolic acidemia were excluded.

Methods

Medical records were reviewed retrospectively. The primary outcome was time taken to resolve acidemia. Secondary outcomes were acute care area free days in 5 days (ACAFD₅), and adverse outcome as composite of Pediatric Intensive Care Unit (PICU) admission and/or death.

Results

Out of 929 diarrhea patients admitted for intravenous therapy, 121 (13%; median age, 4 months) had ADSD and sNAGMA. Median (IQR) pH was 7.11 (7.01-7.22); 21% patients had pH <7.00. Hyperchloremia (96%) and hypernatremia (45%) were common. About 12% patients each required inotropes and ventilation, while 58% had acute kidney injury (AKI). Median (IQR) time for resolution of acidemia among survivors was 24 (12, 24) hours. Thirty-two patients had adverse outcome. Higher grades of sNAGMA were associated with shock, AKI, coma, hypernatremia, hyperkalemia, adverse outcome, and lesser ACAFD₅. Shock, ventilation, renal replacement therapy (RRT), and higher grades of sNAGMA were predictors of adverse outcome, with former two being independent predictors.

Conclusion

Severe non-anion-gap metabolic acidemia in children with ADSD is associated with organ dysfunctions, dyselectrolytemias, and lesser ACAFD5. Resolution of acidemia took unacceptably longer time. Higher grades of sNAGMA were a predictor of adverse outcomes. Trials are suggested to assess the role of additional bicarbonate therapy.

How to cite this article

Takia L, Baranwal AK, Gupta PK, Angurana SK, Jayashree M. Acute Diarrhea and Severe Dehydration in Children: Does Non-anion-gap Component of Severe Metabolic Acidemia Need More Attention? Indian J Crit Care Med 2022;26(12):1300-1307.

Oral rehydration therapy

Oral rehydration therapy (ORT) with glucose-electrolyte solutions has been considered to be one of the greatest therapeutic advances of this century. ORT is effective in acute diarrheal disease of diverse etiology. The most widely used oral rehydration solution (ORS) worldwide is that recommended by the World Health Organisation (Na 90, K 20, glucose 111 and citrate 10 mmol/L). Attempts to improve the efficacy of ORS have been made by using complex substrates (rice and other cereals) in place of glucose, and by reducing osmolality by decreasing glucose and sodium concentrations in monomeric ORS. ORS may have wider applications in the management of patients with the short bowel syndrome and in post-surgical patients.

Randomised double blind trial of hypotonic oral rehydration solutions with and without citrate

Hypotonic oral rehydration salts solutions (ORS) have been proved to be better than isotonic solutions with respect to water absorption. To establish whether a base precursor is essential in the composition of a hypotonic ORS with improved absorption properties, a randomised double blind clinical trial was conducted comparing two formulas of hypotonic ORS, each with an osmolality of 224 mmol/l, with or without citrate, in a group of 107 children admitted to hospital with acute diarrhoea. The two solutions were effective in the correction of dehydration and there was no difference between the treatments in the duration of diarrhoea. The patients receiving the hypotonic ORS with citrate consumed less of the solution, however, and their metabolic acidosis was corrected earlier. It is concluded that citrate is clinically advantageous in a hypotonic ORS, but a hypotonic formula without a base precursor is also effective.

Management of gastroenteritis in early childhood

The most important aspect of modern management of acute diarrhoeal illness in children is that of oral rehydration therapy, and drug therapy is very rarely indicated. Despite the dramatic decline in mortality and morbidity in recent years, there is still the need for continuing education in the appropriate use of oral rehydration solutions. The constitution of oral rehydration solutions and policies of feeding practices during illness continue to be controversial, mainly because of wide variation in the aetiology of the diarrhoea, the nutrition of the child, and the economic and public health factors involved in any particular community. The priority of all healthcare workers is to provide simple guidelines in the use of a safe oral rehydration solution while discouraging unsafe treatments.

Search for the ideal oral rehydration solution: studies in a model of secretory diarrhoea

In situ perfusion of whole rat small intestine was used to compare the efficacy of five oral rehydration solutions in promoting water and sodium absorption in normal intestine and secreting intestine after exposure to cholera toxin. Solutions varied in their sodium (35-90 mmol/l) and glucose (111-200 mmol/l) concentrations, molar ratio of glucose:sodium (1.2-5.8), and osmolality (281-331 mOsmol/kg), and contained either bicarbonate (18-30 mmol/l) or citrate (10 mmol/l). In normal intestine all solutions promoted net water absorption. Cholera toxin induced reproducible water secretion but all solutions reversed this to absorption. Water absorption was greatest with solutions containing sodium 60 mmol/l and glucose 111 or 140 mmol/l, and with a glucose:sodium ratio approximately 2, in both normal and secreting intestine. All solutions promoted net glucose absorption in both normal and secreting intestine. Net sodium absorption occurred with solutions containing greater than or equal to 60 mmol/l sodium in normal intestine but sodium secretion occurred from all solutions in secreting intestine. Sodium movement was directly related to the sodium concentration of the solution and sodium secretion occurred despite net water and glucose absorption. We consider that these studies may guide future development of oral rehydration solutions.

Assessment of water and solute absorption from experimental hypotonic and established oral rehydration solutions in secreting rat intestine

Water and solute absorption from three experimental hypotonic oral rehydration solutions (HYPO-ORS; sodium 45, 60 and 75 mmol/L, glucose 90 mmol/L), the World Health Organization recommended ORS (WHO-ORS; sodium 90 mmol/L, glucose 111 mmol/L), and the British National Formulary recommended ORS (BNF-ORS; sodium 35 mmol/L, glucose 200 mmol/L), have been assessed by perfusion studies in cholera toxin-induced secreting rat intestine. Net water absorption was greatest from the most hypotonic solution (HYPO-45; P less than 0.05). UK-ORS prevented net water secretion and WHO-ORS promoted moderate net water absorption. Net sodium secretion was seen with all solutions but was least from WHO-ORS and greatest with BNF-ORS (P less than 0.01). Glucose absorption was similar from BNF-ORS, WHO-ORS and HYPO-45 and in each case was greater than glucose absorption from HYPO-60 and HYPO-75 (P less than 0.05). These results suggest that net water and sodium absorption from ORS may be enhanced if osmolality is reduced by decreasing the glucose content.

Comparison of rat and human intestinal perfusion models for assessing efficacy of oral rehydration solutions

The optimal composition for oral rehydration solutions remains controversial. Animal models have been used to assess the efficacy of new formulations but the relevance of these studies to the handling of oral rehydration solutions in human intestine during diarrhoeal disease states remains uncertain. Using steady state perfusion techniques we have compared water and solute transport from a variety of oral rehydration solutions in both the entire rat small intestine and in the human jejunum. Overall the pattern of water, sodium and glucose absorption was similar from the three oral rehydration solutions tested, indicating close parallelism between the two models despite the species and methodological differences. Although the relationship between the findings of these studies to the handling of oral rehydration solution in diarrhoeal disease states remains uncertain, we believe they do support the view that animal models may have a part to play in the preliminary screening of oral rehydration solutions before clinical trial.

The role of oral rehydration solutions in the children of Europe: continuing controversies

Controversy remains concerning ORS composition in Europe. This centres chiefly upon the sodium level. Solutions with a low sodium content continue to be widely used in Europe. ORS with Na 90 mmol/l when given correctly is safe and effective. However when this solution is prepared incorrectly there is a risk of hypernatraemia. In most of Europe mortality and morbidity from gastroenteritis is now very low. Therefore any change from current formulation must not carry any risk in this regard. The need for bicarbonate or indeed any base in ORS is also controversial. There is a clear need in Europe for controlled trials of ORS solutions of various composition to determine the ideal solution for the children of Europe who have acute diarrhoea.

Disease-related animal models for optimising oral rehydration solution composition

To optimise the composition of oral rehydration solutions (ORS) for European children is not a simple task. Although controlled clinical trial is ultimately the only way to determine whether a new solution is superior to an established ORS, testing many different formulations is neither feasible nor ethical. Several groups of investigators have evolved the concept of using animal models to test new ORS formulations. Disease-related animal models using perfusion of cholera toxin-treated rat small intestine or experimental rotavirus infection of neonatal rats suggest that optimal water absorption will be obtained by using a hypotonic ORS with a sodium concentration of 50-60 mmol/l and a glucose concentration of 50-100 mmol/l. Addition of citrate or bicarbonate had no benefit with respect to the promotion of water absorption.

Optimising oral rehydration solution composition for the children of Europe: clinical trials

Clinical trials testing different oral rehydration solutions (ORS) are reviewed. The effects of individual components and their concentrations are analysed in order to establish margins of safety for the composition of the ideal ORS for children in Europe. Glucose is the solute of choice for ORS and concentrations of 70-140 mmol/l are adequate. Glucose may be replaced by sucrose or glucose polymers. "Low" sodium concentrations (35-60 mmol/l) are advised for rehydration and maintenance in acute non-cholera diarrhoea, for children of all ages, including neonates, and for any degree of dehydration except shock. Although intended for children who are not malnourished, the European ORS should have an adequate potassium concentration (20-30 mmol/l), namely the same concentration as found in WHO-ORS. Chloride concentration depends upon other constituents of ORS, namely sodium and potassium, but the range of 30-90 mmol/l is considered to be adequate. Base or base precursors are not required for correction of acidosis except in the severe cases that always need intravenous replacement. A relatively low osmolality seems advisable.

Evaluation of three oral rehydration solutions designed for use in developed communities

One hundred and sixteen children (less than 2 years old) admitted to a London hospital with acute gastroenteritis were randomized to receive either an oral rehydration solution (ORS) with low sodium and high glucose concentration (Na+ 35, glucose 200 mmol/L), an ORS with a high sodium but low glucose concentration (Na+ 60, glucose 111 mmol/L), or an ORS containing glycine and a glucose polymer (Na+ 50, glucose 50, glycine 50 mmol/L). Clinical, biochemical and haematological features of the three groups were similar on admission. Rotavirus was common (31%); the majority of children had minimal dehydration or acid-base disturbance. The clinical outcome, including ORS intake, prevention of dehydration, rehydration, and duration of hospital stay was similar in the three treatment groups. All initial electrolyte abnormalities were corrected; no child developed hypernatraemia or hyponatraemia. At 24 h, the mean serum urea was higher in those who received the ORS containing glycine than in other groups, and it had not fallen significantly since admission. Eighteen per cent of children had carbohydrate intolerance: four children with greater than or equal to 2% reducing substances in their stool had all received ORS with a high glucose content and had numerous watery green stools containing rotavirus. All ORS solutions were safe and effective for rehydration and correction of biochemical abnormalities, however carbohydrate intolerance was more prevalent in children who received the ORS with a high glucose content.

Effect of bicarbonate, acetate, and citrate on water and sodium movement in normal and cholera toxin-treated rat small intestine

Bicarbonate, citrate, or acetate are commonly included in oral rehydration solutions to correct acidosis and possibly because of their ability to promote water and sodium absorption. We have investigated the effect of these anions on water and sodium transport in normal and also in secreting (cholera toxin-treated) rat small intestine using a single-pass perfusion technique. In normal jejunum bicarbonate and acetate produced net absorption, and citrate net secretion of both water and sodium. In normal ileum all anions produced net absorption of water and sodium. In the secreting jejunum, however, bicarbonate had no effect on water and sodium secretion, whereas acetate and citrate actually enhanced the secretory state for both water and sodium. None of these anions had any effect on water and sodium secretion in the ileum. These observations suggest that normal and secreting intestine are qualitatively different with regard to handling of these organic anions. The addition, therefore, of bicarbonate, acetate, or citrate to oral rehydration solutions may have no beneficial effect with regard to the promotion of water and sodium absorption in the secreting intestine during acute diarrhoeal states and could actually be deleterious.

Effect of bicarbonate on efficacy of oral rehydration therapy: studies in an experimental model of secretory diarrhoea

In situ perfusion of rat intestine was used to evaluate the effect of bicarbonate on the efficacy of a low sodium (35 mmol/l) glucose-electrolyte oral rehydration solution in normal and cholera toxin-treated rat small intestine. In normal intestine, absorption of water was greater (108 (8.1) microliters/min/g; p less than 0.01) and sodium secretion less (-4.3 (0.3) mumol/min/g; p less than 0.01) from the oral rehydration solution containing bicarbonate than from the solution in which bicarbonate was replaced by chloride ions (59.5 (7.2) microliters/min/g and -7.8 (0.8) mumol/min/g, respectively). Glucose absorption in normal intestine was similar with both solutions. In the secreting intestine, both oral rehydration solutions reversed net water secretion to absorption, but inclusion of bicarbonate resulted in significantly less net absorption of both water (2.18 (6.9) microliters/min/g; p less than 0.05) and glucose (18.7 (2.1) mumol/min/g; p less than 0.001) compared with bicarbonate free oral rehydration solution (19.4 (3.9) microliters/min/g and 35.8 (3.7) mumol/min/g, respectively). Net sodium secretion occurred in normal and secreting intestine but was significantly less with the bicarbonate containing oral rehydration solution. These findings suggest that the demonstrable advantage of bicarbonate in promoting water absorption from this oral rehydration solution in normal rat intestine does not apply to cholera toxin treated secreting intestine.

Oral rehydration therapy without bicarbonate for prevention and treatment of dehydration: a double-blind controlled trial

Forty children (less than or equal to 2 years of age) were admitted to hospital with acute gastroenteritis and were randomly assigned to receive either an oral rehydration solution (ORS) containing bicarbonate (Na 35, K 20, Cl 37, HCO3 18, glucose 202 mmol litre-1) or an identical solution in which bicarbonate was replaced by chloride ions. Groups were matched for age, sex, ethnic origin, duration of diarrhoea and nutritional status. On admission, degree of dehydration, biochemical and haematological parameters were similar. The majority had minimal or no dehydration and only 30% had moderate to severe dehydration. All children were treated successfully with no complications. Oral rehydration solution intake by each group was similar. Clinical outcome, as judged by speed of rehydration or maintenance of hydration, duration of diarrhoea, stool frequency and length of hospital stay, was the same in both groups. After 24 h of ORS there was no difference between groups in venous pH, serum bicarbonate, urea and electrolytes. In hospitalized children with acute gastroenteritis in the United Kingdom an ORS without bicarbonate is a safe, effective means to prevent dehydration and maintain hydration and acid-base status where dehydration is not severe. Exclusion of bicarbonate would simplify production, increase stability and reduce the cost of ORS without apparent impairment of efficacy.

Experimental models for the investigation of water and solute transport in man. Implications for oral rehydration solutions

For patients suffering from mild to moderate dehydration, oral rehydration therapy has proved a simple and efficacious treatment. There remains, however, a need to develop improved oral rehydration solutions (ORS), and suitable experimental models are required to develop and assess new formulations. The ideal model for such investigations would take into account rates of gastric emptying, influx and efflux of water and solutes in the intestine, and the consequent changes in body composition. As no such definitive model is currently available, a variety of techniques are used to examine parts of the process of intestinal absorption. Clinical studies which assess the recovery of dehydrated patients during therapy using different ORS will ultimately evaluate the efficacy of treatment. However, ethical considerations, the relative insensitivity of this technique and the exacting nature of such studies make this approach unsuitable for the development of specific ORS. Gastric emptying of solutions can be determined by a variety of techniques, among which the radioactive tracer method offers the advantage of having no direct effect on the emptying rate, giving almost continuous measurement and allowing the use of relatively small volumes of fluids. Perfusion techniques allow measurement of the net flux of water and solute in predetermined sections of the intact human intestine. Measurement of the rate of accumulation in the circulation of orally ingested tracer molecules for water and solutes can estimate unidirectional flux. This method allows for the rates of gastric emptying and intestinal absorption of the test substance, but the rate of efflux of the tracer from the vascular space must be known to calculate net uptake. Each of these models has limitations, and care must be taken in interpreting the results in a clinical context. However, their use in the development of improved formulations is well established.

History and rationale of oral rehydration and recent developments in formulating an optimal solution

Oral rehydration therapy with glucose-electrolyte solutions has been one of the major therapeutic advances of the century. This alarmingly simple intervention developed from a basic scientific observation in the laboratory, when it was shown that sodium and glucose transport in the small intestine are coupled and thus the presence of glucose in an electrolyte solution promotes absorption of both sodium ions and water. Even more important, sodium/glucose co-transport continues despite the secretory diarrhoea of cholera and enterotoxigenic E. coli and after intestinal damage due to rotavirus. Despite widespread use of the oral rehydration solutions (ORS) recommended by the World Health Organization (WHO), controversy continues about the optimal composition of these solutions. Discussion centres around the sodium and glucose concentrations, the osmolality and whether base (bicarbonate) or base-precursor (citrate) is necessary. Already there is a clear divide between the developing world, where the WHO solution (Na 90, glucose 111 and bicarbonate 30 mmol/L) is widely used, and the industrialised world, where solutions with lower sodium and until recently higher glucose concentrations have been favoured. Recently, attempts have been made to optimise ORS using animal and human model systems before submitting new candidate ORS to clinical trial. Results to date suggest that hypotonic ORS containing 50-60 mmol/L sodium and 90-100 mmol/L glucose produce maximal water absorption. The presence of base or base-precursor appears to offer little with regard to the promotion of sodium and water absorption and its role in combating acidosis remains controversial. Complex substrates such as rice powder and glucose polymers may eventually replace glucose in ORS, since their addition reduces ORS osmolality still further.