Intraoperative Fluid Administration in ENT Surgery: Impact on Acid-Base Balance and Renal Function (Experience from a Developing Country)

Background: Excessive administration of 0.9% sodium chloride may induce hyperchloremic metabolic acidosis and impair postoperative organ function. This study aimed to evaluate the incidence of perioperative hyperchloremic acidosis in major ENT surgery and to assess its association with intravenous fluid volume and early postoperative renal function. Methods: This was a prospective observational study approved by the institutional ethics committee (Approval No. 2025/RSI/127; ethics committee registration number: 2024/BOC/187). The study was conducted in the ENT operating theatre between November 2024 and March 2025. Adult patients (>18 years) undergoing procedures lasting more than 3 hours were included. Patients with pre-existing renal failure, preoperative acidosis, or surgeries requiring controlled hypotension were excluded. Pre- and postoperative biological parameters were correlated with fluid volume, type of surgery, operative duration, and perioperative complications using Fisher's exact test. Results: Forty patients were included (male-to-female ratio = 2.64). Oncologic procedures represented 92.5% of cases. The mean intraoperative fluid volume was 2.91 L, and all patients received 0.9% sodium chloride exclusively. The incidence of hyperchloremic acidosis was 22.5%. A highly significant association was found between fluid volume >4 L and hyperchloremic acidosis (p = 0.00002). Operative duration was also significantly associated with acidosis occurrence. Although 10% of patients developed KDIGO stage 1 acute kidney injury on postoperative day 1, hyperchloremic acidosis was not statistically associated with acute kidney injury (p = 0.213). Conclusion: Hyperchloremic metabolic acidosis is a frequent iatrogenic complication in major ENT surgery, strongly associated with high intravenous fluid volumes and prolonged operative duration. These findings support an individualized perioperative fluid strategy favoring balanced crystalloid solutions. Larger multicenter studies are needed to confirm these findings.