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REGIONAL ANESTHESIA

Tensile Strength of 19- and 20-Gauge Arrow Epidural Catheters

From the Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, Alberta, Canada

Address correspondence and reprint requests to Ban C. H. Tsui, MSC, MD, FRCP(C), Department of Anesthesiology and Pain Medicine, University of Alberta Hospitals, 3B2.32 Walter Mackenzie Health Science Centre, 8440–112 Street, Edmonton, Alberta, Canada T6G 2B7. Address email to btsui{at}ualberta.ca

There are no data about the mechanical properties of the 20-gauge reinforced Arrow epidural catheter, which has a similar design to the 19-gauge reinforced Arrow catheter. In this study, we compared the mechanical properties of 19- and 20-gauge Arrow epidural catheters at 22°C and 37°C. The distal 12 cm of each catheter was suspended in an enclosed chamber maintained at either 22°C or 37°C. A pair of forceps was applied to each catheter 5 cm from the distal end (fixed site). Another pair of forceps was applied 15 cm from the catheter tip (traction site). The catheter was pulled. At 22°C, the mean fracture force was 2.24 kg (range, 1.96 – 2.41 kg) for 5 19-gauge catheters and 2.17 kg (range, 2.04–2.41 kg) for 5 20-gauge catheters. At 37°C, the mean force was 1.98 kg (range 1.84- 2.15 kg) for 5 19-gauge catheters and 1.99 kg (range, 1.81–2.09 kg) for 5 20-gauge catheters. There were no significant differences in tensile strength between the two different gauge catheters at either temperature. All the 19-gauge catheters fractured at the same "fixed site" at both temperatures. All the 20-gauge catheters elongated at the "fixed site" but fractured at the "traction site." We conclude that using the smaller-gauge catheter (20-gauge) is not associated with a more frequent rate of fracture.

IMPLICATIONS: The 20-gauge Arrow epidural catheters had similar tensile strengths as the 19-gauge epidural catheters but fractured at the traction site rather than at the fixed site. Thus, the 20-gauge Arrow catheter may be a reasonable alternative to the 19-gauge Arrow catheter.