Different crystalloids, namely 0.9% saline and balanced crystalloid may result in different metabolomic profile among surgical patients. This study aims to investigate the serum and urine profiles between patients undergoing major spine surgery using 0.9% saline and balanced crystalloid.

Intravenous fluid is mandatory for acute and critically ill patients as well as for surgical patients. Two crystalloid iv. solutions namely 0.9% saline and balanced crystalloid are the most commonly administrated. However, early literature suggests that 0.9% saline is associated with hyperchloremic acidosis, which affects cellular metabolism and may result in worse prognosis among acute or critically ill patients. However, recent literature in 2018, including a meta-analysis and a large randomized controlled trial published in the New England Journal of Medicine revealed neutral or merely slight different clinical outcomes between 0.9% saline and balanced crystalloids. Therefore, the metabolic differences between these two fluids may only exist in specific metabolic pathway which may be easily masked by the complex pathophysiological changes in acute and critically ill patients. These metabolic alteration may be only identified by precise research t the technology such as liquid chromatography mass spectrometry, which provides more comprehensive metabolomics profiles. By comparison, surgical patients undergoing major spine surgery receive a relatively large amount of intravenous infusion during surgery, and there is not complicated with complex pathophysiological alteration of cormorbid diseases. Accordingly, this study aim to identify the metabolomic differences between 0.9% saline and balanced crystalloid among patients undergoing major spine surgery by using the liquid chromatography mass spectrometry technique.

Inclusion criteria:

1. age between 40 and 65 year-old
2. major lumbar spine surgery (spinal fusion、multiple levels or expected operation time> 2 hr)

Exclusion criteria:

1. Preoperative organ dysfunction, such as impaired liver function, eg. AST or ALT >100; liver cirrhosis > Child B class; Impaired renal function, eGFR< 60 ml/min/1.73 m2; cardiac dysfunction, such as heart failure > NYHA class II, coronary arterial disease, chronic obstructive pulmonary disease
2. Preoperative use of medications which interfere with liver, renal, glucose or electrolyte metabolism, such as insulin, statin or digoxin
3. Pregnancy