Intermittent Boluses of Balanced Salt Solution for Post-operative Intravenous Hydration Following Elective Major Abdominal and Thoracic Surgery in Children

Background: Traditional protocols for maintenance intravenous fluids (mIVF) following major abdominal or thoracic operations in children emphasize continuous fluid administration, total volume based on the 4:2:1 rule, hypotonic solutions, and the inclusion of 5% dextrose1,2. Recent studies questioned these tenets and argue that isotonic, balanced salt solutions with lower doses of dextrose better maintain homeostasis3,4. There are limited data, however, that address the use of continuous fluids. We believe that administering maintenance fluids in the form of intermittent boluses is more physiologic and could limit the volume of post-operative fluids, thereby avoiding harmful effects of maintenance fluids on electrolyte homeostasis, glucose metabolism, and organ function. We began implementing this strategy several years ago and in this study sought to compare patients treated with post-operative boluses to those still managed with continuous fluids.

Methods: We included children aged 1-21 admitted to a regular hospital bed after an elective major abdominal or thoracic operation from 2015-2021. Operations included tumor resection or biopsy, small and large bowel resection, J-pouch creation, and nephrectomy. We excluded patients undergoing non-elective operations and those who received peri-operative parenteral nutrition. We analyzed total volume of fluid at 0-24, 24-48, 48-72, and 72-96 hours, time to regular diet and discharge, and end-organ complications.

Results: We included 362 patients, 108 of whom were treated with bolus mIVF and 254 with continuous mIVF. Patients in the bolus group had significantly less fluid up to 72h post-operatively with average rates of 0.49mL/kg/h vs 0.86mL/kg/h at 0-24h (p< <0.05), 0.57mL/kg/h vs 1.46mL/kg/h at 24-48h (p< <0.05), 0.50 vs 0.92 mL/kg/h at 48-72h (p< <0.05), and 0.57mL/kg/h vs 0.69mL/kg/h at 72-96h (p=0.44). These differences hold true on subgroup analysis of each operation. Additionally, the bolus group tolerated a regular diet sooner than the continuous group (2.08 days vs 2.51 days; p=0.0023) and averaged a shorter hospital stay (3.12 vs 4.14 days; p=0.004). Six patients in the continuous mIVF group required temporary supplemental oxygen, compared to two in the bolus group. Given our practice of limiting post-operative labs, there was insufficient data to compare creatinine, sodium, and glucose values between groups, but only one patient in each group required free water restriction for clinically evident fluid retention and no patients developed seizures or symptoms of hypoglycemia.

Conclusion: Patients in the bolus IV-fluid group received less fluid than the continuous group up to 72 hours and achieved a faster time to regular diet and discharge. Additionally, the bolus strategy appears to be safe with no difference in supplemental oxygen requirement, seizures, or need for glucose supplementation. This study provides a proof of concept for a planned randomized trial that will be necessary to better address the underlying questions.