Glucose in epidural catheter aspirate

Frequently fluid may be aspirated from epidural catheters during epidural anesthesia/analgesia. This fluid may be either cerebrospinal fluid or local anesthetic. Several methods for differentiation of the two fluids have been recommended. In this study, the reliability of the "glucose test" was analyzed. Epidural catheters were inserted into 43 healthy, nondiabetic parturients and then gently aspirated. Aspirate was tested for glucose using glucose oxidase paper. Positive aspirates were assessed for the presence of prealbumin, which is a protein marker for cerebrospinal fluid. Of the patients undergoing cesarean section, 17 of 27 patients yielded a glucose-positive aspirate, and of the patients undergoing labor analgesia, 6 of 16 patients were found to be positive for glucose. None of these patients developed total spinal anesthesia or postdural puncture headache. Visually, none of the aspirates were significantly blood-tinged, blood being a possible source of glucose. When the glucose-positive aspirates were subjected to immunoelectrophoresis, 6 of 7 aspirates revealed a prealbumin band. In conclusion, the glucose test for cerebrospinal fluid may be misleading. The source of this glucose may be normal cerebrospinal fluid drainage into the epidural space.