DISTINGUISHING CEREBROSPINAL-FLUID FROM SALINE USED TO IDENTIFY THE EXTRADURAL SPACE

Because of the potential seriousness of unrecognized dural puncture-du ring the performance of extradural analgesia and the widespread use of normal saline for the ''loss of resistance'' technique, it is importa nt to differentiate between cerebrospinal fluid (CSF) and saline dripp ing from the extradural needle. During insertion of lumbar drains in 1 0 neurosurgical patients, we first identified the extradural space usi ng saline for loss of resistance. Temperature (using the back of the g loved hand), pH, glucose and protein (using urine testing sticks) were tested by a blinded observer for ability to distinguish saline aspira ted from the extradural space from CSF aspirated on establishing the d ural puncture. Temperature, glucose and protein were independently 100 % accurate in distinguishing saline from CSF. One saline sample had a pH value greater than 7 compared with nine CSF samples. We conclude th at simple bedside testing for temperature, glucose, protein and pH acc urately distinguished between CSF and saline used to identify the extr adural space.