Lessons from in vitro testing of spinal needles

In vitro testing of spinal needles is intended to identify a best buy, but such tests are not necessarily good indicators of clinical performance and some bench tests appear to conflict with mock clinical assessments. Discrepancies can be explained by examining the role of the hub. The Visual Probability Test, which assesses the needle as a complete unit, would appear to be more useful than the more complex measurements of shaft flow. Not all needle manufacturers use the same gauge, creating confusion when comparisons are made. Packaging frequently fails to give adequate information. Changes in hub design could permit earlier identification of dural puncture.