Acute watery diarrhoea (AWD) remains a major global health problem in children under five (05) years of age. According to the World Health Organization (WHO), diarrhoeal disease is one of the leading causes of childhood mortality and morbidity worldwide [1]. In developing countries in particular, severe dehydration (SD) from diarrhoea contributes significantly to hospital admissions and deaths [2, 3]. In Pakistan, the burden is especially heavy: a recent commentary reported that diarrhoeal illness accounts for approximately 74 deaths per 1,000 children annually, highlighting the persistent vulnerability of the under-five age group [4]. Given the high prevalence of hazardous water and sanitation conditions, the management of acute diarrhoea with dehydration is a public health priority in the country.

Intravenous fluid therapy is central to the children management with AWD and SD. Two widely used isotonic crystalloids are Ringer’s Lactate (RL) and Normal Saline (NS). RL is a “balanced” crystalloid solution that contains lactate, which is metabolised to bicarbonate and thus may help correct acidosis; in contrast NS is high in chloride and has been associated with hyperchloraemic metabolic acidosis in some studies [5]. Balanced crystalloids such as RL have been shown in recent reviews to reduce post-resuscitation chloride burden compared to NS, although evidence in paediatric diarrhoeal dehydration is limited [6]. Therefore, comparing RL and NS in the context of acute paediatric diarrhoeal dehydration is of clinical importance.

There is evidence to suggest that RL may be superior to NS in improving acid-base status and reducing fluid volumes required, yet many studies in children with diarrhoea and severe dehydration remain small or outdated. For example, a recent single-centre observational study in Pakistan found significantly higher mean serum bicarbonate and pH at 6 hours in children receiving RL versus NS [7]. However, larger prospective observational studies in similar settings are scarce. Understanding the comparative performance of RL and NS in routine clinical care will help optimise fluid management protocols, particularly in resource-limited settings where rapid correction of metabolic disturbances can influence outcomes.

The objective of the present study is to observe the difference in acid-base correction (as indicated by serum bicarbonate and blood pH) at 6 hours in children aged 1–5 years with AWD and SD, between those receiving RL and those receiving NS.

This prospective observational study was done in the Department of Paediatrics Unit I, Services Hospital, Lahore. It was completed over six months after approval from the Ethical Review Committee (Ref. No. 2025/12/R-80; dated 17-12-25). Children were selected by consecutive sampling. Children aged 1 to 5 years were included. They had acute watery diarrhoea (three or more watery stools in 24 hours) for less than 14 days. They also had severe dehydration on clinical examination. Children were not included if they had blood in stool (dysentery). Children with severe malnutrition were excluded. Children were excluded if they had dysentery, severe malnutrition, underlying renal disease, congenital heart disease or metabolic disorders (e.g., diabetic ketoacidosis), had received intravenous rehydration before presentation, or were in shock requiring inotropes/needed intensive care. Consent was taken from the parent or guardian before enrolment. Treatment was given as routine hospital care. The treating doctor chose the IV fluid. Children were observed in two groups based on the fluid used. One group received Ringer’s lactate (RL). The other group received normal saline (NS). The sample size was calculated using the WHO sample size calculator for two independent means, with mean serum bicarbonate at 6 hours as the primary endpoint (α=0.05, power=80%, clinically important difference=1.1 mEq/L, pooled SD=2.25 mEq/L), resulting in 70 children per group (total n=140) [8]; recruitment continued until at least 70 eligible participants were included in each group. Baseline clinical assessment and relevant laboratory investigations were recorded at presentation (T0), including venous blood pH and serum bicarbonate (and other clinically indicated parameters), and the same key measurements were repeated at 6 hours (T6) to assess correction of metabolic acidosis. Clinical status during the initial 6 hours was documented, including hydration status, need for further intravenous therapy, any adverse events, and disposition after reassessment. Statistical Analysis Data were analyzed using SPSS (version 24). Continuous variables (e.g., serum bicarbonate, serum potassium, and venous blood pH) were summarized as mean ± standard deviation (SD), while categorical variables (e.g., sex, hydration status, need for further IV therapy, disposition, and adverse events) were presented as frequencies and percentages. Normality of continuous variables was assessed (Shapiro–Wilk). For between-group comparisons (Ringer Lactate vs Normal Saline), an independent-samples t-test was used for approximately normally distributed data; otherwise, the Mann–Whitney U test was applied. Gender-wise comparisons were performed similarly within each fluid group. To evaluate response to treatment over time, change scores (Δ = 6-hour value − baseline value) were calculated for key outcomes (e.g., bicarbonate, pH, potassium) and compared between groups using the same approach. Categorical outcomes were compared using the chi-square test (or Fisher’s exact test when expected cell counts were small). All tests were two-tailed, and a p-value ≤ 0.05 was considered statistically significant.

Gender-wise comparisons within each treatment arm showed that male and female children were broadly similar in baseline characteristics in both the normal saline (NS) and Ringer lactate (RL) groups. In the NS arm, there were no significant gender differences in age, weight, baseline serum bicarbonate, baseline serum potassium, baseline venous pH, stool frequency, or 6-hour values of serum bicarbonate, potassium and venous pH (all p > 0.05). In the RL arm, baseline variables were also comparable between males and females (all p > 0.05), and serum bicarbonate at 6 hours did not differ by gender (p = 0.8968). However, at 6 hours in the RL group, female children had significantly higher serum potassium (3.94 ± 0.23 vs 3.82 ± 0.27; p = 0.0409) and slightly higher venous pH (7.40 ± 0.03 vs 7.39 ± 0.03; p = 0.0397) compared with males (Table 1).

In the comparison between NS and RL, baseline acid–base status was broadly similar between groups, with no significant differences in baseline serum bicarbonate (p = 0.2208) or baseline venous pH (p = 0.0910). At 6 hours, children who received RL showed significantly better correction of metabolic acidosis than those who received NS, with higher serum bicarbonate (p < 0.0001) and higher venous pH (p < 0.0001). The magnitude of improvement from baseline was also greater in the RL group, with a higher ΔHCO3 (p < 0.0001) and a higher ΔpH (p < 0.0001). Additionally, serum potassium at 6 hours and ΔK+ were significantly higher in the RL group than in the NS group (p < 0.0001 for both) (Table 2).

In the comparison between NS and RL, baseline acid–base status was broadly similar between groups, with no significant differences in baseline serum bicarbonate (p = 0.2208) or baseline venous pH (p = 0.0910). At 6 hours, children who received RL showed significantly better correction of metabolic acidosis than those who received NS, with higher serum bicarbonate (p < 0.0001) and higher venous pH (p < 0.0001). The magnitude of improvement from baseline was also greater in the RL group, with a higher ΔHCO3 (p < 0.0001) and a higher ΔpH (p < 0.0001). Additionally, serum potassium at 6 hours and ΔK+ were significantly higher in the RL group than in the NS group (p < 0.0001 for both) (Table 2).

Table 1. Gender-wise comparison of quantitative variables in children receiving normal saline (NS) versus Ringer lactate (RL), expressed as mean ± SD.

Table 2. RL versus NS comparison of acid–base correction at 6 hours.

In this prospective observational study from a pediatric unit in Lahore, children who received Ringer’s lactate (RL) showed faster correction of metabolic acidosis than those who received normal saline (NS). Baseline acid–base values were broadly similar between groups. At 6 hours, RL produced a higher mean serum bicarbonate (26.32 ± 1.56 vs 21.35 ± 1.20 mEq/L; p< 0.0001) and a higher venous pH (7.39 ± 0.03 vs 7.33 ± 0.04; p < 0.0001). The rise from baseline was also larger with RL (ΔHCO₃: 6.81 ± 1.75 vs 2.10 ± 1.55; p < 0.0001 and ΔpH: 0.08 ± 0.04 vs 0.03 ± 0.04; p < 0.0001). Serum potassium at 6 hours and the increase in potassium were also higher in the RL group (both p < 0.0001).

These findings are biologically plausible. RL is a “balanced” crystalloid. Its lactate is metabolized to bicarbonate in the liver. This can help improve bicarbonate and pH. NS contains a high chloride load. High chloride can lower the strong ion difference. This may worsen or prolong metabolic acidosis (hyperchloremic acidosis). So, even if dehydration improves, acidosis may correct more slowly with NS.

High-quality Pakistani comparative trials in the last few years are limited. This made our local evidence base weak. Our results therefore add new local data from routine care in a high-burden setting. A recent Cochrane systematic review (2023) evaluated balanced crystalloids versus 0.9% saline in severely dehydrated children with acute diarrhoea. It reported that balanced fluids probably increased blood pH and bicarbonate compared with saline and likely reduced post-treatment hypokalaemia. This matched the direction of our findings, where RL achieved higher pH, higher bicarbonate, and higher potassium values at 6 hours.[9] Large randomized trials in ICU patients also provided useful context. In BaSICS (JAMA 2021), use of a balanced solution did not reduce 90-day mortality compared with saline, but it supported that “hard outcomes” may not always change even when biochemical profiles differ. This helped interpret our results: RL improved acid–base correction quickly, but this did not automatically mean mortality or major outcomes would change (especially since we only measured early 6-hour correction). [10] The PLUS trial (NEJM 2022) similarly found no clear mortality or kidney benefit for balanced multielectrolyte solution versus saline in critically ill adults. This again suggested that balanced fluids mainly improve biochemical patterns, while clinical outcomes depend on many other factors. [11] A 2023 systematic review and meta-analysis in ICU patients also reported that balanced crystalloids did not clearly reduce mortality or major kidney outcomes versus saline, although some analyses suggested reduced AKI incidence. This reinforced the idea that biochemical benefits are more consistent than mortality benefits. [6]

Potassium improved more in the RL group at 6 hours. This could be because correction of acidosis shifts potassium back into cells less aggressively than persistent acidosis, and because balanced fluids may reduce chloride-related effects on renal potassium handling. The Cochrane review also suggested balanced fluids likely reduce hypokalaemia after correction. [9]

This study reflected real-world practice in a busy pediatric unit and used objective biochemical endpoints at baseline and 6 hours. However, it was observational. Fluid choice was decided by the treating doctor, so confounding by indication was possible. We also assessed only short-term correction (6 hours). We did not evaluate longer outcomes (length of stay, readmission, renal outcomes) in the same table. Future work should include longer follow-up, adjustment for baseline severity, and ideally randomized allocation.

In children aged 1–5 years with acute watery diarrhoea and severe dehydration, Ringer’s lactate produced a faster and better correction of metabolic acidosis than normal saline at 6 hours. The Ringer’s lactate group achieved higher serum bicarbonate and venous pH levels, with a greater improvement from baseline, and showed a more favorable potassium profile. Overall, these findings support using Ringer’s lactate as the preferred intravenous fluid for early resuscitation and correction of acidosis in this clinical setting.

FUNDING

None.

CONFLICT OF INTEREST

None.

AUTHORS’ CONTRIBUTION

All authors contributed equally as per ICMJE.

ACKNOWLEDGMENT

None.