Craniopharyngiomas and giant invasive pituitary adenomas, with lesions originating from the pituitary stalk, are frequently associated with intraoperative and postoperative diabetes insipidus (DI). DI can lead to hypernatremia, and the rapid elevation of serum sodium within hours can precipitate acute brain tissue shrinkage, potentially resulting in devastating complications including intracerebral hemorrhage, cerebral venous sinus thrombosis, seizures, somnolence, and coma. Furthermore, dehydration secondary to DI may compromise organ perfusion and enhance anaerobic glycolysis in tissues, leading to hyperlactatemia and even lactic acidosis. However, the currently available evidence is insufficient to support the routine prophylactic anti-diuretic therapy during surgery.This study aims to evaluate the efficacy and safety of prophylactic low-dose continuous intravenous dDAVP infusion in patients undergoing surgery for complex sellar region lesions, with respect to reducing the incidence of hypernatremia occurring during surgery or within the first 24 hours postoperatively.

Inclusion Criteria:

• (1) Demographic information: Age 18 to 75 years, any gender, any race. (2) Target disease: Preoperative pituitary MRI-confirmed diagnosis of sellar region lesions requiring surgical intervention, including craniopharyngioma, pituitary adenoma, and other sellar region lesions. The patient must meet at least two of the following high-risk criteria:

  1. Preoperatively confirmed central diabetes insipidus (CDI);

  2. Maximum tumor diameter > 3 cm with imaging evidence of suprasellar extension;

  3. Imaging evidence of close anatomical relationship with the pituitary stalk, posterior pituitary, or hypothalamus, including compression, encasement, or invasion;

  4. Estimated surgical duration > 4 hours. (3) Health status: Adequate organ function to tolerate surgery, and no contraindications to desmopressin (dDAVP) administration. American Society of Anesthesiologists (ASA) Physical Status classification I, II, or III, with comorbid conditions being stably controlled prior to surgery.

     (4) Concomitant medication: Patients must have discontinued medications that may significantly affect intraoperative water-electrolyte balance (e.g., thiazide diuretics, antipsychotics such as chlorpromazine, olanzapine, clozapine, carbamazepine, etc.) prior to surgery, until the investigator assesses the risk as acceptable

     Exclusion Criteria:

• (1) Patients with pre-existing comorbidities affecting water and salt metabolism, including but not limited to:

  1. Renal insufficiency (dDAVP is predominantly excreted unchanged by the kidneys; renal impairment may significantly prolong its half-life and increase the risk of hyponatremia);

  2. Cardiac insufficiency (dDAVP-induced water and sodium retention may increase circulating blood volume and potentially precipitate heart failure);

  3. Untreated adrenal insufficiency (cortisol deficiency impairs free water excretion);

  4. Uncorrected hyponatremia prior to surgery. (2) Patients requiring concomitant use of medications that may induce hyponatremia and cannot be temporarily discontinued, including but not limited to chlorpromazine, olanzapine, clozapine, carbamazepine, thiazide diuretics, etc.

     (3) Pregnant or breastfeeding patients. (4) Patients with known hypersensitivity to dDAVP or any of its excipients. (5) Patients currently participating in any other clinical trial. If the patient has previously participated in a drug clinical trial, the time from the last dose of the investigational drug must exceed 4 weeks.

     (6) Any other conditions deemed unsuitable for participation in this study by the investigator's judgment.