A midline catheter offers an alternative to peripheral and central venous access. Where patients present with poor peripheral venous access and when the use of a central venous catheter (CVC) is contraindicated, a midline catheter provides venous accessibility along with easy, less hazardous insertion in veins of the upper arm, above the antecubital fossa (Dawson and Moureau [108], Mushtaq et al. [340], Weinstein and Hagle [465]). Because the tip of the catheter does not extend beyond the extremities in which it is placed, radiographic confirmation of tip placement is optional and recommended only when there is difficulty in insertion or flushing (Gorski and Czaplewski [180], Weinstein and Hagle [465]).

Midlines are experiencing a resurgence of attention and usage due to improvements in catheter materials and product development. Newer midline catheters are 8–10 cm in length and can be placed using a modified Seldinger technique (MST). Some models are all‐in‐one devices with the needle, wire and introducer in a combined unit for ease and speed of access; for these, the insertion technique referred to as accelerated Seldinger (AST) should be used (Moureau and Chopra [330]). The growing evidence to support the use of midlines demonstrates lower phlebitis rates than those for peripheral intravenous cannulas and lower rates of infection than those for CVCs (Caparas and Hu [61], Dawson and Moureau [108], Moureau and Chopra [330], Mushtaq et al. [340], Warrington et al. [462]). Other benefits to patients include less frequent re‐siting of peripheral intravenous cannulas and a subsequent reduction in associated venous trauma (Gorski and Czaplewski [180], Moureau and Chopra [330], Weinstein and Hagle [465]).

The insertion is performed via an introducer or using an MST (i.e. when venous access is established with a needle, a guidewire is threaded through the needle, the needle is removed, an introducer/peel‐away sheath is threaded over the guidewire, the guidewire and dilator are then removed, and the catheter is advanced into the venous system through the introducer/peel‐away sheath) (Hadaway [194], Weinstein and Hagle [465]). Newer all‐in‐one midlines follow an AST as the needle, guidewire and introducer are combined (Moureau and Chopra [330]). Adequate ultrasound assessment of the patient's veins is vital to ensure vessel patency, identify any thrombosis and assess the diameter of the vein to be cannulated (Alexandrou et al. [4], Gorski et al. [181]). Given the choice, the non‐dominant arm should be used (Alexandrou et al. [4]).