Introduction: Patients need intravenous fluids during Surgery to maintain adequate intravascular volume, cardiac output, and ultimately tissue Oxygen delivery. Aim of the study: Aim of the study was to evaluate serum sodium after infusion of isotonic fluid containing 131 mEq/L sodium with no glucose versus that after infusion of hypotonic fluids containing 75 mEq/L sodium with 5% dextrose. Methods: This study was conducted on pediatric patients of Bangladesh Shishu Hospital and Institute who underwent hernia operations between January 2021 and September 2021. Data are given as mean+standard deviation. P-value <0.05 was considered to be significant. continuous demographic variables were compared using the unpaired t-test, and the chi-square test was used for categorical variables. Result: There were no adverse events and all 40 patients enrolled in this study completed the procedures. The pre-anesthesia and post-anesthesia induction blood sodium concentration. Pre-anesthesia sodium (mEq/L), Isotonic was 138.7 + 1.4 and Hypotonic was 138.9 + 1.5, the charges from pre-anesthesia to postanesthesia induction was - 0.20 + 1.6. Post-anesthesia sodium (mEq/L), Isotonic was 138.5 + 1.5 and Hypotonic was 137.3 + 1.2, the charges from pre-anesthesia to postanesthesia induction was - 1.60 + 1.8. Conclusion: The administration of hypotonic fluids tends to reduce serum sodium absorption in pediatric cases, indeed when administered for a short period. But the use of isotonic fluids helps to avoid a reduction in serum sodium in pediatric and so may enhance patient safety.