How sweet is it? Measurement of glucose in epidural fluid and fluid obtained during spinal anesthesia after a failed epidural using a bedside monitor
Abstract Number: S-12
Abstract Type: Original Research
Many cesarean deliveries (CD) are performed by supplementing a pre-existing labor epidural. In some cases, supplementation proves inadequate so the anaesthetist may choose to do a spinal anesthetic. Rarely, this fails; the reason being that epidural local anesthetic fluid is identified as cerebrospinal fluid (CSF). Methods to differentiate between CSF and epidural fluid are not completely reliable but glucose appears to be the best indicator. However, one study found that glucose appears in the epidural space 30 minutes after epidural catheter insertion (false positive). We hypothesized that a bedside glucometer could reliably quantify glucose within fluid aspirated from an epidural catheter. Knowing the normal glucose range in epidural fluid (obtained from a functioning epidural catheter) may help differentiate it from CSF.
In this prospective IRB approved observational study, the epidural catheter of consenting laboring parturients was aspirated >20 min after an epidural bolus. The deadspace volume was discarded and after reaspiration the fluid was tested with a glucometer (Novastat™). If a CD was done and time allowed the epidural fluid was again tested. If spinal anesthesia was required the fluid obtained was also tested. At each testing time a capillary blood glucose was done.
65 women were recruited, 26 samples were sufficient for testing. Epidural glucose in 22 samples was ‘less than 0.6 mmol/L’. 4 samples had glucose values of 0.9-2.2mmol/L and in 3 of the 4 the fluid was serosanguinous. Blood glucose in these women was normal (5.3-5.8 mmol/L). 8 women had a CD and 2 had a spinal (CSF glucoses 2.7, 3.7 mmol/L).
The range of glucose in epidural fluid tested was 0-2.2 mmol/L. Compared to CSF glucose ranges in parturients (2-4 mmol/L) found in a previous study, these results demonstrate the feasibility of using a glucometer to distinguish CSF from epidural fluid but results are not 100% reliable. However, if glucose is <0.6 mmol/L, it is likely epidural fluid. The results of this study suggest that point of care testing for glucose at the time of doing spinal anesthesia after failed epidural top-up may help ensure the needle is in the subarachnoid space.
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