This evidence-based series was developed by the Central Venous Access Devise Guideline Panel of Cancer Care Ontario's (CCO's) Program in Evidence-based Care (PEBC). The series is a convenient and up-to-date source of the best available evidence on managing central venous access devices in cancer patients, developed through systematic review, evidence synthesis, and input from practitioners in Ontario.
The Central Venous Lines Guideline Panel:
- Formulated a set of guideline questions relevant to cancer care in Ontario
- Reviewed the available evidence on the effectiveness of locking solutions, volumes, and frequency, and various types of central venous access devices (CVADs)
- Considered the quantity, quality, consistency, completeness, and relevance of the evidence
- Drafted recommendations based on the available evidence, panel members' expert opinions, and guidelines from other groups. Patient safety, convenience, and quality of life were considered in formulating recommendations.
Consensus
The Central Venous Access Device Guideline Panel is comprised of nurses from across Ontario specializing in adult and pediatric oncology care and advanced oncology nurses. The recommendations for the adult population were based on a combination of the evidence presented, existing recommendations from institutions across the province and manufacturers' recommendations. Where those lacked, expert opinion and panel consensus were incorporated into the recommendations. As well, the panel used the Practitioner Feedback as further evaluation of the recommendations.
A consensus recommendation to maintain the status quo in pediatric oncology practice was reached based on the lack of evidence for or against any of the protocols currently in use. Although the pediatric representatives on the panel recognized the value of standardized guidelines and practice, the commitment to individual institutional practices remained strong.
Should central venous lines access devices (CVADs) be locked with heparin or saline?
The uses of either saline or heparin in the catheters are based on the manufacturers' recommendations, institutional protocols, and the panel's expertise. Saline is recommended by the manufacturers of closed ended catheters and positive pressure injection/lock adaptors because these valves prevent blood backflow into the lumen of the catheter and therefore would reduce or eliminate the risk of intraluminal thrombus occlusion. The panel would like to emphasize that with the use of saline in these devices, the proper procedure must be followed as outlined by the manufacturers to prevent blood backflow as an improper flushing procedure and backflow of blood can cause a thrombus or occlusion.
Heparin is used to prevent thrombus development if blood should enter the lumen of the catheter and is therefore used with open ended catheters. Open or closed ended catheters with or without positive pressure devices and external extensions (e.g., Hickman) can become kinked or bent exerting enough pressure to push small amounts of heparin or saline into the vein. This can generate negative pressure when compression is released to draw blood back into the lumen of a catheter, allowing for thrombus development.
Implanted ports are not visible and there is no way of knowing the type of catheter being used or type/size of port unless the patient has some way to verify this. For this reason heparin is used to be safe in reducing the risk of thrombus occlusion.
What volume and strength of solution should be used to lock CVADs?
The volume of solution to be used in a CVAD depends on the catheter length, the internal diameter of the tubing, the reservoirs and extensions, and the need to ensure that all surface areas receive adequate turbulence and flushing. Manufacturer documents state that the volume of the flush solution should be equal to at least twice the volume capacity of the catheter and add-on devices. The panel used the manufacturers' recommendations and expert opinion to arrive at the volume of solution recommendations.
Since there was no evidence to support one concentration of heparin over another, and the manufacturers' recommendation was the use of institutional protocols, the consensus of the group was to recommend a heparin concentration of 100 units/mL since it is the most common concentration of heparin used in most institutions in Ontario.
How frequently should CVADs be locked?
Although patient convenience and costs to patients, families, and institutions may be considered when deciding on the frequency of flushing, the panel used expertise, manufacturers' recommendations and common practice to generate recommendations for the flush frequency for each device. The implanted port does not have any external adaptor that requires changing (i.e., injection caps) unless it is accessed. If a port or catheter is accessed, the recommendations are once weekly, the non-coring needle and extension/injection cap/adaptor are changed and the line flushed. Injection caps require changing a minimum of every week or as needed. For this reason the lines are flushed as a minimum with each cap change since flushing and locking are part of this process with injection cap/adaptor changes.
What type of catheter should be used and what indicators influence the choice?
Consensus was not reached for which indicators had an impact on the decision of inserting a CVAD, due to a lack of evidence and stakeholders. It was determined that, in the lack of evidence, other considerations would be needed to come to a consensus that are practical and clinical that may dictate if a CVAD be used; such as the attending physicians' and the patients' preference, operating room time, cost, expert availability and resources to support the CVAD.
