Background: Postoperatively reduced concentration of ascorbic acid (AA) in plasma (< or =45.5 micromol/l (< or =800 microg/dl)) is commonly interpreted as increased metabolic requirements, but it is not shown yet that the patient benefits from a substitution toward normal levels of AA. This is due to the missing knowledge on how to substitute AA effectively to normal plasma values in postoperative patients. Therefore, a postoperative AA substitution procedure "overnight" to normal values in plasma was investigated on a postoperative intensive care unit (ICU) in a university hospital.
Material and methods: Fifty-seven operated patients were randomly assigned to a control- or intervention group (CG and IG, respectively). In all patients, the AA plasma concentration was analysed preoperatively and on the first three postoperative days. Patients of the IG received AA intravenously up to four times within 12 h depending upon the initial AA concentration (<34.1 micromol/l (4x500 mg AA); < or =56.8 micromol/l (2x500 mg AA); < or =68.2 micromol/l (1x500 mg AA)).
Results: The preoperative and early postoperative AA values did not differ between the groups. On the first postoperative day in both groups the plasma concentration was lowered (< or =45.5 micromol/l) in 23 of all patients (CG: 85.18%; IG: 82.14%). In the IG, the dosage regime increased the AA plasma concentration to > or =45.5 micromol/l in 26 of 28 (92.86%) patients overnight.
Conclusion: The investigated substitution procedure is sufficient to increase AA plasma concentration overnight to normal or high normal values in postoperative ICU patients.