Objectives

1. To observe whether sodium bicarbonate Ringer injections can reduce the incidence of postoperative complications in elderly patients undergoing abdominal surgery.
2. To observe the effects of sodium bicarbonate Ringer injections on the internal environment, such as water, electrolytes, acid-base balance, and other physiological indexes, in the perioperative period of elderly patients undergoing abdominal surgery.

Research design：This study adopts a multicenter, prospective, randomized, controlled, pragmatic clinical trials (PCT) research design.

Sample size：5000 cases. Indication：The experimental group is the elderly patients undergoing abdominal surgery who were administered sodium bicarbonate Ringer injections intraoperatively; the control group is the elderly patients with abdominal surgery who were administered lactated Ringer's injections intraoperatively.

Observational index

Preoperative baseline data collection:

General patient information: basic information (age, height, and weight), preoperative diagnosis, past history, auxiliary examination results, etc.

Intraoperative data collection:

Perioperative vital signs information and arterial blood gas analysis results; The surgical method, operation time, and anaesthesia time; Intraoperative fluid management: The total amount of intraoperative fluids, blood transfusion volume, bleeding volume, urine volume, types and dosage of vasoactive drugs, diuretic dosage, sodium bicarbonate dosage.

Postoperative index:

Postoperative blood biochemical examination: liver function, renal function (urea nitrogen, creatinine), osmotic pressure, lactic acid, and blood sugar levels; Postoperative complications and treatment status Postoperative recovery: postoperative outcome, length of hospital stay, admission to ICU (duration of stay), postoperative eating time, out of bed activity time, gastrointestinal recovery time (exhaust), time for removal of various tubes (gastric tube, urinary tube, and drainage tube), etc.

The observation cut-off point is the patient's discharge. If the patient is still hospitalized 30 days after the operation, the observation will be terminated.

Research process

1. Elderly abdominal surgery patients who meet the inclusion criteria will be enrolled and randomly divided into two groups according to the intraoperative application of extracellular fluid supplements. The experimental group is sodium bicarbonate Ringer injection group, and the control group is sodium lactate Ringer injection. Basic preoperative information of patients will be collected. The vital signs, fluid treatment, and surgical anaesthesia will be recorded during the operation, while the recovery and postoperative complications will be recorded during postoperative visits.
2. The ability of sodium bicarbonate Ringer injections to reduce postoperative complications in elderly patients undergoing abdominal surgery will be observed.
3. The effects of sodium bicarbonate Ringer injection on the internal environment, such as water, electrolytes, acid-base balance, and other physiological indexes in elderly patients undergoing abdominal surgery will be observed and compared.
4. The safety and efficacy of sodium bicarbonate Ringer injection in elderly patients with abdominal diseases will be comprehensively assessed.

Inclusion Criteria:

• (1) Patients need to be over 65 years of age, while there is no restriction on gender.
• (2) Patients are planned to undergo upper abdominal surgery under general anaesthesia, with an expected operation time of >2 h, and the infusion volume is >1000ml.
• (3) The patient agrees to participate in the clinical research and signs the informed consent.

Exclusion Criteria:

• (1) Emergency surgery
• (2) Hypermagnesemia (defined as serum Mg2+ >1.25mmol/L)
• (3) Patients who participated in other drug trials in the past 6 months
• (4) Known allergic reactions to the test drug and/or its components
• (5) Patients judged to lack the ability of providing informed consent
• (6) Other situations considered unsuitable for enrollment by the researcher.