Yes, this is indeed a practice to consider, however when and how it is done requires some practice changes. The 2016 INS Standard on Phlebotomy states to consider using a peripheral catheter for blood sampling in pediatric patients, adults with difficult venous access, the presence of bleeding disorders and the need for serial tests. The issue is the point in the procedure when the sample should be obtained. The answer is after the procedure is completed. Tourniquet time is the reason for this recommendation. The length of time that a tourniquet should be on for drawing all blood samples is no more than 1 minute. Lengthy tourniquet times cause changes in the venous endothelial that produces changes in the lab values for many tests. Longer tourniquet time is usually needed for insertion of a short peripheral catheter using customary techniques of seeing and feeling the vein. Instead of drawing the sample as you insert the catheter, finish the procedure with complete securement and dressing. Then draw the sample. This allows for the tourniquet to be removed and the normal blood flow to flush away the blood containing the cellular substances that leads to alterations in lab values. Learn more about the decisions for obtaining a blood sample in our online course – Blood Sampling: Venipuncture or VAD? The focus is now on preventing hospital-acquired anemia associated with blood sampling and several other issues. Yes, the parameters for pH have been removed from the INS Standards of Practice. Evidence shows that this is not the critical factor in reducing intraluminal vein damage that we originally thought it to be. But I have encountered lots of confusion on this issue since the Standards were released.
There seems to be a prevailing idea that pH of the solution is the only factor that causes a medication to be a vesicant but this is not a correct idea. In our online course, Infiltration and Extravasation from Vascular Access Devices, 5 causes of tissue damage are discussed including osmotic pressure, non-physiologic pH, ischemia, mechanical compression, and cellular toxicity. Additionally, an I.V. medication can cause vein irritation (phlebitis) and subcutaneous tissue damage due to the excipients in the medication. Excipients are the “inactive ingredients” added to medications, primarily for the sake of drug stability. Examples include various types of alcohol, preservatives, and other agents. Here is the full ingredient list for promethazine: “Each mL contains promethazine HCl, either 25 mg or 50 mg, edetate disodium 0.1 mg, calcium chloride 0.04 mg, sodium metabisulfite 0.25 mg and phenol 5 mg in Water for injection. pH 4.0 to 5.5; buffered with acetic acid-sodium acetate.” The full ingredient list for phenytoin sodium injection (Dilantin) is: “phenytoin sodium in a vehicle containing 40% propylene glycol and 10% alcohol in water for injection, adjusted to pH 12 with sodium hydroxide.” Vancomycin may contain hydrochloric acid and/or sodium hydroxide for pH adjustment. Nafcillin has dextrose, sodium citrate hydrous, hydrochloric acid or sodium hydroxide added for a final pH between 6.5 to 8. Although the pH of nafcillin is as close as any drug to physiologic pH, the drug literature also states: “Pain, swelling, inflammation, phlebitis, thrombophlebitis, and occasional skin sloughing at the injection site have occurred with intravenous administration of nafcillin. (See Dosage and Administration.) Severe tissue necrosis with sloughing secondary to subcutaneous extravasation of nafcillin has been reported.” The list of non-antineoplastic medications that are vesicants is extensive and also included in our online course. “Vesicant” is defined as a drug causing blisters and other tissue injury that may be severe and can lead to tissue necrosis. There is nothing in this definition about the actual reason for any drug being a vesicant. For this reason, anyone involved with administering I.V. medications must know the full nature of these medications, and the risks involved. Infiltration and extravasation are one of the most common causes of infusion-related lawsuits. Learn more by taking our online course. Click here for more information. The typical procedure for thrombolysis in central vascular access devices calls for the use of tPA (Alteplase) 2 mg in 2 mL. But what about the implanted ports that hold more volume than 2 mL? The internal volume of the catheter plus the port body plus the access needle could easily be more than 2 mL. Large lumen catheters and high profile port bodies could easily equal 3 mL or more. Before using any medication for catheter clearance, ensure you have ruled out other causes of the occlusion. VADs without a blood return should not be used, but make sure your technique is not the problem. Use a slow, gentle technique to aspirate. Use a smaller diameter syringe (e.g. 5 mL or 3 mL) as these cause LESS pressure on aspiration. Look at the history of the problem to determine if this is truly a thrombotic occlusion or if it could be caused by contact between incompatible medications producing a precipitate or a total nutrient admixture that causes a lipid buildup on the intraluminal catheter walls. Mechanical problems such as pinch-off syndrome should also be considered for subclavian insertion sites. Also check for external problems such as closed clamps or kinked tubing. The internal volume of the entire catheter system can be difficult to determine. The design of the port body and lumen size of the catheter varies. The manufacturer provides the internal volume or priming volume of each brand of implanted port. However, the catheter is cut to a patient-specific length, which decreases the original internal volume. Several interventions to manage this problem should be considered. Obtaining the internal lumen volume could be done by simple aspiration. First flush the catheter with normal saline. Attach an empty syringe, and slowly aspirate until the blood has reached the connection of the syringe to the needleless connector on the port access extension set. Note the space in the syringe as this should approximate the catheter’s internal volume. But remember, this has to be done and documented before an occlusion occurs. This volume would determine the amount of tPA required to fill the entire length of the system. The other option is to instill the tPA dose of 2 mg in 2 mL, and then follow it be a small amount of normal saline such as 0.5 to 1 mL to move the tPA to the distal end of the catheter and into direct contact with the location of the thrombus. Dilution of the tPA to less than 2 mg in 2 mL by adding more volume is not recommended as this may not be as effective. I would recommend reading the 2016 Infusion Therapy Standard of Practice #48 Central Vascular Access Device Occlusion for more details. This question is not addressed because there are no studies reporting these variations, but there can be concern among nurses doing this procedure for implanted ports. There are currently several midline catheters available with a labeled indication for power injection of contrast agents. While the catheter are build to withstand the pressure that may be created with power injection, we need to ask another question – Is it safe to use a midline tip location for power injection of contrast agents? The simple answer is we don’t know yet.
The concern is the injection of a hypertonic contrast agent considered to be vesicants into the deep upper arm location of a midline catheter. Deep veins could mean that fluid in the tissue may go undetected and potentially damage large arteries and nerves in the area. Many clinicians report that a midline catheter will not typically produce a blood return, thus eliminating one component of a complete clinical assessment of catheter patency. One the positive side, evidence is showing that longer catheters are needed when ultrasound is used to access deep vessels. Higher rates of infiltration/extravasation are reported when deep veins are used, even with 1.8 and 2 inch long catheters. This may indicate tht a 3 inch long catheter could be safer than a 2 inch catheter in the veins of the upper extremity. At the present time, there is a distinct need for more research on midline catheters and the midline tip location. I am aware of 2 simple descriptive clinical studies on the newer midline catheters labeled for power injection. These studies included a brief statement about small numbers of patients having the midline catheter used for contrast injection. These studies did not include details of the types of contrast agents used, the rates of injection, or the dwell time of the midline catheter when the contrast was injected. Extravasation with contrast agents happens, although it is reported to have very low rates usually less than 1%. In my experience as an expert witness, I have seen about 15 cases of contrast extravasation however all have involved short peripheral catheters inserted in the hand, wrist or antecubital fossa. No cases have involved a midline catheter or midline tip location. The bottom line is we need more data for these critical clinical decisions. I think that the language we use is important for adequate communication. If we are not using the same words to indicate certain actions, how can we understand each other? Or adequately communicate good practices to our patients? The 2016 Infusion Therapy Standards of Practice contains an expanded Glossary so we can enhance our communication with each other. One area where there seems to much confusion is how we use the words “flushing” and “locking” for all VADs. The INS glossary defines
Flushing is done most commonly with normal saline, although a few drugs may be incompatible with saline. In that case, 5% dextrose in water is used to flush the drug from the lumen but saline should be used to flush out the dextrose as this will provide nutrients for growing biofilm. Solutions for locking a VAD are expanding. Evidence now shows that either normal saline or heparin lock solution produces similar outcomes for locking a central VAD. One solution is not better than the other. Additionally, new antimicrobial lock solutions such as ethanol, citrate, and numerous antibiotic solutions are proving to prevent and treat catheter related bloodstream infection. All studies refer to these as “locking solutions”. Different purposes, a variety of solutions, different volumes, and locking periods makes this an expanding and complex topic. So flushing and locking are not interchangeable terms. Using the correct word will enhance interprofessional communication. |
Author: Lynn HadawayLynn Hadaway is an international thought leader in infusion therapy and vascular access, having been in this practice for more than 40 years. Her experience comes from hospital-based infusion teams, device manufacturers, and continuing education services. Her journal and textbook publications are extensive. She also maintains board certification in infusion nursing (CRNI) and nursing professional development (RN-BC). Categories
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May 2019
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