Isotonic solutions, which are commonly used in clinical practice, mainly consist of 5% glucose injection, 0.9% sodium chloride injection, 5% sodium chloride glucose injection, 1.87% sodium lactate solution and 1.4% sodium bicarbonate solution. An isotonic solution is a solution prepared to keep the osmotic pressure of the fluid containing the drug in line with that of the fluid in the human body and to keep it in balance so that the cells do not swell and die due to water loss or water absorption as a result of pressure. Such a solution is maintained at a concentration of 280-320 mmol/L. Therefore, as long as the liquid concentration is within this range, it can be called an isotonic solution.