Study objective: To determine how and why cholesterol concentrations decrease after surgery, and the effect of the administration of nutritional support.
Design: Prospective, observational study.
Setting: Surgical intensive care unit of a university hospital.
Patients: 213 consecutive patients admitted to a surgical intensive care unit after major surgery.
Measurements and main results: Serum concentrations of cholesterol, serum albumin and total protein. The initial portion of this study demonstrated that serum concentrations of cholesterol, like those of serum albumin and total protein, decreased by approximately 30% immediately following surgery. These changes were directly related to changes in hematocrit and inversely correlated with the volume of perioperative intravenous (IV)fluid, the degree of positive fluid balance, and the estimated blood loss. The study's second phase examined the 19 patients who received at least 10 days of nutritional support. After 1 week of feeding, serum total protein concentrations increased significantly, but did not return to preoperative levels. Serum concentrations of cholesterol, which were markedly decreased prior to nutritional repletion, increased significantly after 9 days of treatment. The changes in serum cholesterol concentration were negatively correlated (r = -0.32) with the daily intake of IV fluid.
Conclusion: Serum cholesterol concentrations, like those of serum albumin and total protein, are markedly reduced immediately following major abdominal surgery, often to levels reported in malnutrition. Dilution by IV fluid and redistribution into an expanded extracellular fluid space are likely the major causes of these decreases. Serum cholesterol concentrations are therefore not useful in the nutritional assessment of patients in the immediate postoperative period.