Clearance of ascorbic acid in plasma in patients before major maxillofacial surgery compared with that in volunteers.

Reduced concentration of ascorbic acid (AA) in plasma is often observed in tumor patients. Besides malnutrition, an increased AA consumption in tumor patients is discussed as a main reason for reduced AA concentration in plasma. A reduced AA concentration caused by malnutrition would not influence the total clearance (Cltot) of AA in plasma; however, a change in AA consumption would alter the Cltot. To investigate this further, a study was carried out on 20 patients hospitalized for major maxillofacial surgery and 20 volunteers. The Cltot of AA in plasma after bolus injection of AA (4 mg/kg body wt) in tumor patients was compared with that in volunteers. AA concentration in plasma (P < 0.05) was significantly lower in tumor patients (median and 25th and 75th percentiles: 23.7, 14.6, and 32.7 mumol/l) than in volunteers (median and 25th and 75th percentiles: 66.5, 59.6, and 78.6 mumol/l). No significant change in Cltot was observed for tumor patients (median and 25th and 75th percentiles: 11.5, 8.0, and 14.0 l/h) compared with volunteers (median and 25th and 75th percentiles: 11.3, 9.9, and 13.2 l/h). No indication of an increased consumption of AA in tumor patients could be detected. The lowered concentration of AA in plasma observed in our patients might be the result of a reduced AA intake.