(1) Changes in protein. During peritoneal dialysis, albumin, globulin and immunoglobulin are all lost to varying degrees. The average daily loss in protein is 5 ~ 15g, and IPD is10.5 ~ 44.3g. During peritonitis, the loss of protein increased exponentially. The lost protein is mainly albumin, accounting for 48% ~ 65%, and IgG accounts for 15%. Although protein was lost during peritoneal dialysis, due to the improvement of uremia symptoms after dialysis, patients' intake of protein increased, reaching more than 1.2g/kg per day, and the total calories could exceed 1.47 kj/kg. Therefore, in the first few months, the average weight of CAPD increased by more than 5 kg, the overall potassium content increased, the circumference and skin fold thickness of the upper arm increased, the hemoglobin increased, and even returned to a near normal level, and the plasma protein was normal. However, with the extension of dialysis time, patients' appetite gradually decreased, protein intake decreased to 65438±0.0g/kg per day, and total calories decreased to 65438±0.26 kj/kg. Some patients suffered from malnutrition and hypoproteinemia. Biochemical examination showed that the total nitrogen decreased gradually, while the output remained unchanged, indicating that they were in a negative nitrogen balance. A few months after dialysis, a lot of protein is lost due to peritonitis. If the intake is insufficient, there will be loss syndrome, which is characterized by weight loss, fatigue, emaciation and weakness, loss of appetite, edema, and peripheral neuritis in the later stage. These patients need hemodialysis.

(2) Changes of amino acids. The loss of amino acids in CAPD patients is the same as that in hemodialysis, which is about 65438±0.2 ~ 3.4g per day, accounting for 5.3% of the nitrogen content in dialysate, of which essential amino acids account for 29%. The clearance rate of amino acids is 20% lower than that of creatinine, because the average molecular weight of the former is 140 dalton, while the average molecular weight of the latter is 1 13 dalton. After CAPD treatment, the plasma amino acid levels did not change significantly, such as valine, leucine, lysine and threonine. Non-essential amino acids such as cheese, silk, glutamic acid and taurine decreased, while other non-essential amino acids increased.

(3) changes in vitamins. Studies have shown that CAPD patients lack water-soluble vitamins, such as vitamin C, vitamin B 1, vitamin B6 and folic acid, which are related to dialysis loss. So these vitamins and folic acid must be supplemented.