MICROSCOPIC ANALYSIS OF THE TIPS OF THIN SPINAL NEEDLES AFTER SUBARACHNOID PUNCTURE

Background and Objectives. Foreign material may pass unrecognized with the spinal needle into the subarachnoid space. Therefore the tips of three clinically used types of spinal needles-Quincke (27-gauge), two- zone bevel (26-gauge), and Sprotte or pencil point (27-gauge)-were pre pared for microscopic analysis after subarachnoid puncture in human ca davers. Methods. Three cadavers were placed in the lateral position, t he backs were scrubbed with disinfectant solution containing 0.1% fluo rescein, and 12 needles of each type (half of them through an introduc er) were inserted via interspaces L2-L5 into the subarachnoid space. U nder visual control (spinal canal opened), the needle tips were cut an d collected for fluorescence microscopy. Another eight needles of each type (half through an introducer) were inserted, the tips were collec ted into tubes filled with physiologic saline, and cytocentrifuged sme ars of the eluted material were made. Results. On microscopy, only one of the two-zone bevel needles and two of the pencil point needles, pl aced through an introducer, were without attachments. All the others h ad variable amounts of fluorescence, and visible tissue particles adhe red to the lip. The largest particles appeared on two of the Quincke n eedle tips. Bent tips were seen on 7 of the 12 two-zone bevel needles. The Quincke group had two and the pencil point group no bent needle t ips. Clusters of epithelioid cells were seen in the cytocentrifugation smears of Quincke and two-zone bevel needle tips, but only very few c ellular clusters were seen in the smears from the pencil point needle tips. Conclusions. Of the three needle types studied, the pencil point type has a tip that best withstands distortion and adherence of forei gn material during experimental subarachnoid puncture.