Don’t Overflush Lines
Julie Marshall MD
Peter Rock MD, MBA
Anesthesiologists become experts at the placement of lines for access and monitoring, but the routine care and maintenance of these lines may be less familiar. It is important to remember that unintentional overflushing of arterial and central lines happens commonly (especially during the busier intervals in a procedure) and can lead to significant complications. Also, patients not infrequently come to the operating room (OR) or intensive care unit (ICU) with indwelling devices already in place. These may under certain circumstances be accessed for use in the OR, provided that the anesthesia providers have a plan and proceed carefully.
Overzealous flushing of arterial lines may lead to retrograde embolization of air or clot into the central arterial circulation. It has been shown that the saline volume needed to reach the subclavian-vertebral artery junction from a radial artery averages just 6.6 mL, with a range from 3 to 12 mL. Arterial catheter continuous-flush devices deliver 3 mL/hour of saline, often with heparin, at a pressure of 300 mm Hg. Flushing the line through the flush valve or with a syringe can increase the volume and rate of delivery. Continuous-flush devices have been reported to deliver 0.8 to 4.7 mL/second when flushing an arterial line by opening the flush valve (commonly referred to as the “pigtail”). An increased rate of delivery, smaller patient size (infants), and increased flush volume all increase the potential for embolization of air bubbles into the central arterial circulation. To decrease the risk of embolization, all air should be removed from the arterial line. The drip chamber in the flush bag should be completely filled with fluid to decrease the chance of entraining air. Volume and rate of flush should be limited by opening the flush valve for only 2 to 3 seconds at a time. When flushing an arterial line with a syringe, the volumes should be small, 1 to 3 mL, and the flush should be done slowly. Both the injection port and the syringe should be free of air. Emboli may also occur from a clot in the arterial line or from arterial thrombi at the end of the catheter. If the line is not cleared following blood draws, small clots may be found in arterial lines or stopcocks. These small clots can be embolized with a forceful flush. Thrombi may form on the tip of the arterial catheter, which may also embolize with forceful flushing. These emboli have the possibility of entering the central circulation or embolizing peripherally to cause tissue ischemia. Care should be taken to monitor for clots in the line and avoid forceful flushing.
Central lines and vascular access devices are common in the OR and ICU population. Lumens not connected to continuous infusions require intermittent flushing to remain patent or before being put into use. Every line that remains patent is one less line you will have to replace. As with arterial lines, there is risk of air and clot embolization with excessive flushing of lines and/or lack of vigilance in eliminating air and clot from circuits and injections. Infection from indwelling catheters is a serious and frequent occurrence. Maintaining aseptic technique by using alcohol to clean the access port before flushing or accessing lines is required to decrease this risk. Before flushing, the line should be aspirated and the old blood that has been sitting in the line should be discarded. There are two reasons to do this—first, there is no reason to flush into the circulation blood that may have formed clots or be colonized with bacteria that found a nice culture medium of old blood. Second, large-bore indwelling catheters such as the double-lumen Groshong or Shiley catheters that are used for dialysis access will have between 2,500 and 5,000 units of heparin in each lumen. The frequency and volume of flush varies among institutions and depends on the type of catheter. Typically, central lines list the volume on the packaging or on the lumen of the catheter. Groshong catheters need to be flushed weekly; other central lines often need to be flushed more than once per day to remain patent. Saline or heparinized flush may be used, depending on institution preference. When in doubt, consult the ICU or dialysis services at your practicing institution; they will be able to advise you.