Q: What is the difference between a PICC and a midline?

Peripherally inserted central catheters (PICC), which are central lines, and midline catheters, which are peripheral lines, are two types of vascular access devices (VAD) that are used frequently and are often confused with one another. The patient's diagnosis, the predicted span of time the line will be required for therapy, the type of infusion needed, and the cognitive and intellectual level of the patient or caregiver are all considered when deciding which type of VAD the patient will need. PICC lines are typically chosen when longer lengths of intravenous therapy are needed but both PICC lines and midlines can remain in place for an indeterminable amount of time provided they are properly monitored for complications.

The PICC is inserted via the cephalic, basilic, brachial, or median cubital veins in the upper arm, and threaded so the catheter tip is located in the lower segment of the superior vena cava, which is considered central placement as defined by the Infusion Nursing Society (INS) (Gorski et al., 2016). Because a PICC lies within this large vessel, a blood return should be swift and substantial. The INS defines blood return as being "the color and consistency of whole blood when aspirated" (Gorski et al.). Take note that aspirate consisting of blood tinged saline would not be considered sufficient. A "flash" or sluggish return is not acceptable and requires further assessment. The line MUST be flushed with saline after this procedure. This clears the line of any blood residue and along with a "push-pause" method, reduces the buildup of fibrin and platelets. Recognize that blood present in the catheter lumen is a perfect medium for microbes to flourish. This maneuver should not be utilized without an adequate blood return first. As it is a central line, any infusion therapy can be administered via a PICC. A PICC is available with single, double, and triple lumens; however, a PICC with the fewest number of lumens needed should be placed. More lumens equal more catheter manipulations and increased risk for bloodstream infection. Furthermore, larger gauge PICCs are associated with increased risk for venous thrombosis. A chest x-ray is required to confirm placement, unless tip locator technology (e.g., electrocardiograph) is used during insertion. A PICC may be used for laboratory blood draws. It is essential to flush the line with saline (e.g., 20 mL) following blood withdrawal to clear the line of any residue. Aseptic technique and properly trained and competent clinicians are essential for this (and all) procedures.

Midline catheters, which vary in length, are inserted via the same veins used for PICC placement in the middle third of the upper arm; however, the midline catheter is advanced and placed so that the catheter tip is level or near the level of the axilla and distal to the shoulder (Gorski et al., 2016). Midline catheters are contraindicated when there is a history of venous thrombosis, restricted blood flow to the extremities, and end-stage renal disease requiring peripheral vein preservation (Gorski et al.). Recognize that a midline is NOT a central VAD and should never be used for continuous vesicant infusions, total parental nutrition, solutions that are greater than 900 mOsm/L, and those infusates that mandate central line-only administration (Gorski et al.). Midline catheters are inserted by competent clinicians using aseptic technique, most often with the use of maximal sterile barrier precautions. Radiologic confirmation is not required prior to use.

As stated earlier, it is important to assess catheter patency. This means the line must not only flush without resistance, but an adequate blood return should be obtained when the line is aspirated (As stated by one of my colleagues, true patency is a two-way street!). A midline will often fail to present a blood return after several days of dwell time. This alone may not be a reason to remove and replace the line if it is otherwise flushing adequately without patient discomfort and there are no signs of complications such as phlebitis or infiltration. Often, inability to aspirate may be overcome by repositioning the patient (e.g., position arm at 90-degree angle from body), checking for clamps and kinks, as well as an additional saline flush. Careful assessment is required and if the problem persists, further investigation is warranted. Although not indicated for a midline, instillation of a thrombolytic may be considered to restore patency of the PICC.

Infected lines are not only detrimental to patients, but are extremely costly to an already overburdened healthcare system. Once the skin is punctured, the inflammatory cascade and the coagulation process begin. This is the body's defense mechanism in response to foreign intrusion. Attention to reducing microbial growth at the site and to microbial entry via the catheter lumen are critical aspects of post insertion care. Scrupulous hand hygiene and use of hand sanitizers are the single most important tools in preventing the spread of healthcare-associated infections. Aseptic technique must always be practiced when changing the dressing and with every catheter access. A semipermeable transparent dressing is changed every 5 to 7 days (for gauze dressings, every 2 days) in conjunction with site care, which includes careful site assessment, skin antisepsis, and replacement of the stabilization device (Gorski et al., 2016). It is important to perform site care and dressing changes earlier if the dressing becomes loose or wet. Alcoholic chlorhexidine is the preferred skin antiseptic as it provides residual suppression of microbial growth at the site (Gorski et al.). Be sure to note the patient's allergy record prior to proceeding. A semipermeable transparent dressing is best to allow examination of the insertion site for erythema, swelling, and drainage. Catheter stabilization devices should be used to minimize catheter movement at the insertion site to reduce the risk of complications including inadvertent dislodgment. Prior to each catheter access, a 15- to 30-second scrub of the hub with a 70% alcohol swab (no "drive by" scrubbing!) should be performed. Although more expensive, passive disinfection caps containing isopropyl alcohol have been shown to reduce intraluminal microbial contamination and have decreased the rates of central line-associated blood stream infection (Gorski et al.). These caps are placed on the needleless connector in between intermittent infusions and are discarded after removal with a fresh cap replaced after the infusion.

Although the two devices look similar on the outside, they vary greatly on the inside. In many cases, these catheters are placed outside of the home care setting. Home care organizations should obtain and place a copy of the catheter insertion procedure in the medical record so that documentation of the type of catheter is readily available. Labeling the dressing as to the type of line is also recommended (Gorski, 2017). Documentation in the patient's electronic medical record should also be done at the time of placement, and every visit thereafter. This information should also be accurately relayed while communicating with the patient and other healthcare providers.

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