The quality of evidence is downgraded by study quality (unclear allocation concealment and lack of blinding) and by inconsistency (unexplained variability in results).
A Cochrane review [Abstract] 1 included 35 studies with a total of 4 284 subjects; 28 in children, 5 in adults and 2 in both. The trials were conducted in India (10), Bangladesh (9), Egypt (3), Chile (2), Mexico (2), Australia (1), Colombia (1), Madagascar (1), Malaysia (1), Pakistan (1), Philippines (1), Romania (1), Sudan (1), and Thailand (1). All but 2 studies were conducted in hospital settings.
Polymer-based ORS versus glucose-based ORS (osmolarity ≤ 270):Eight studies (n=752) evaluated this comparison, and 7 studies used rice as a polymer source. Polymer-based ORS decreased mean stool output in the first 24 hours (MD −24.60 mL/kg, 95% CI −40.69 to −8.51; 1 study, n=99). The average duration of diarrhoea was reduced by 8 hours (MD −8.24 hours, 95% CI −13.17 to −3.30; statistical heterogeneity I²=86%, 5 studies, n=364) with polymer ORS. Limited studies showed no observed difference in the risk of unscheduled use of intravenous fluid (RR 0.66, 95% CI 0.43 to 1.02; 4 studies, n=376), vomiting, and hyponatraemia.
Polymer-based ORS versus glucose-based ORS (osmolarity ≥ 310):Twenty-seven studies (n=3 532) evaluated this comparison using a variety of polymers. Polymer ORS reduced the total stool output in the first 24 hours (MD −65.47 mL/kg, 95% CI −83.92 to −47.03; statistical heterogeneity I²=100%, 16 studies, n=1 483), and reduced the duration of diarrhoea by around 8 hours (MD −8.47 hours; SD −12.86 to −4.08; statistical heterogeneity I²=100%, 16 studies, n=1 187) with substantial heterogeneity. The proportion of participants that required intravenous hydration was low in most studies with fewer in the polymer ORS group (RR 0.75, 95% CI 0.57 to 0.98; 19 studies, n=1 877) . Subgroup analysis by type of pathogen suggested an effect on unscheduled intravenous fluid in those infected with mixed pathogens (RR 0.63, 95% CI 0.41 to 0.96; 11 studies, n=928), but not in participants positive for Vibrio cholerae (RR 0.94, 95% CI 0.66 to 1.34; 7 studies, n=535). No difference was observed in the number of patients who developed vomiting (RR 0.91, 95% CI 0.72 to 1.14; 10 studies, n=584), hyponatraemia (RR 1.82, 95% CI 0.52 to 6.44; 4 studies, n=385), hypokalaemia (RR 1.29, 95% CI 0.74 to 2.25; 2 studies, n=260), or persistent diarrhoea (RR 1.28, 95% CI 0.68 to 2.41; 2 studies, n=885).
Note: Most studies compared polymer-based ORS with a sugar-salt ORS with a particular strength (ORS ≥ 310), which is slightly more salty than the currently agreed best formula (≤ 270 mOsm/L). Since 2004, the World Health Organization (WHO) has recommended the use of reduced osmolarity ORS≤ 270.
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