Mechanical Aspects of Epidural Catheter Insertion—Prevention of Catheter Buckling by Means of a Needle Hub Insert

Abstract

Six commercially available epidural catheters were tested in a special apparatus designed to simulate epidural catheter insertion and quantitatively measure the buckling strength of these catheters. The experimental apparatus utilized a modified Tuohy needle and a specially calibrated force transducer. Catheters were inserted through the Tuohy needle in a manner similar to that employed clinically, and the maximum forces developed against the surface of the force transducer were recorded electronically. In addition, a custom-designed "needle hub insert" was tested for its ability to prevent catheter buckling during insertion of an epidural catheter through a Tuohy needle. Catheter buckling forces were measured with new catheters and also with catheters that had been damaged by previous insertion attempts. Both the new and damaged catheters were tested with and without the presence of a needle hub insert. Each combination of experimental conditions was replicated four times. The results showed a marked difference in the effective buckling strength of the catheters tested. Buckling strengths ranged from a minimum of 201 +/- 21 g (SD) to 418 +/- 15 g of force. The largest forces were obtained with a Deseret type catheter that had an internal plastic stylet. When comparing only new catheters without stylets, the buckling forces ranged from 201 to 285 g. All catheters, whether new or damaged showed an increase in the maximum buckling force with the use of the needle hub insert. The percentage increase in force (needle hub insert vs. no insert) ranged from a low of 23% to a maximum of 108%.(ABSTRACT TRUNCATED AT 250 WORDS)