Midline Catheter-Associated Thrombosis (MCAT): Does Tip Location in the Axillary Vein Increase Risk?

Midline catheters, used for short- and intermediate-term venous access, are recommended to be placed with the tip in an upper arm vein rather than more proximally, in the axillary vein. Despite guidelines recommending against proximal location of the midline catheter tip, the impact of midline catheter tip location on midline catheter-associated thrombosis (MCAT) risk is unclear. Using a retrospective cohort of hospitalized patients who not only had a midline catheter but also had a chest x-ray and venous duplex performed, the authors evaluated whether axillary vein tip location increased the risk of MCAT. Of the 41 midline catheters with tips located in an arm vein, 17 (41.5%) resulted in a thrombus versus 7 (38.9%) of the 18 midline catheters with tips located in the axillary vein. When compared to midline catheter tips located in an arm vein, midline catheter tips located in the axillary vein were not significantly more likely to result in MCAT in unadjusted analysis (odds ratio [OR] = 0.90 [95% CI, 0.29-2.79], P = .85) or adjusted analysis (OR = 0.62 [95% CI, 0.18-2.12], P = .45). These findings support emerging evidence that there does not appear to be an increased risk of MCAT in midlines with an axillary vein tip location. The practice of avoiding the axillary vein for midline catheter tip placement should be reconsidered.