The Benefits of Saline and Dual-Head Injectors

The use of single-head injectors in CT imaging has shifted significantly to dual-head and syringeless injectors. The advantages of dual-head and syringeless systems are that they permit loading of contrast and saline onto the same injector. Newer contrast-injection systems integrate enhancements to manage injector protocol data, improve patient safety, and workflow efficiency.

Among the available CT dual-head injectors in the United States, several include Bracco Diagnostics’ EmpowerCTA®⁺, Bayer’s Medrad® Stellant, and Guerbet’s OptiVantage®. The most recent technologies, known as Smart CT injectors, are capable of capturing injection protocol data for every CT study and delivering it to Voice Dictation, RIS, PACS, and EMR systems for standardized documentation. Concurrently, radiation dose can be collected, recorded, and made available for each exam. 

Ryan Lee, MD, Section Chief of Neuroradiology and Vice Chair of Safety and Quality at the Einstein Healthcare Network, gave his perspective on data collection during a recent expert panel meeting. “I think where we want to go is tailor the protocols to the specific patient,” Dr. Lee said. “If we can pull information from any source that we have and figure out what the correct protocol should be, including the correct radiation dose, I think we can do the same thing for contrast dose.”

“I think as we get more and more Big Data we can use the power of informatics and machine learning and move towards the direction of tailoring protocols for specific patients,” he added.

Besides offering multiple patient safety measures, smart dual-head injectors can incorporate a saline flush, which ensures complete delivery of the contrast dose into the circulatory system and can reduce the amount of iodine needed to achieve optimal imaging. They also can offer such benefits as better bolus geometry, fewer artifacts on some CT studies, and reduced risk for contrast-induced nephropathy.¹

A dual-head injection protocol consists of an initial saline test injection administered manually to confirm patency of venous access, followed by power injection of contrast bolus and a saline chaser.

Expert panel members Daniele Marin, MD, Medical Director, Duke University School of Medicine and Emilio Vega, Manager, CT Quality and Safety, NYU Langone Health, discuss the benefits of saline utilization. Click here to view the video.

Since contrasted CT studies require contrast administration at high-flow, high-volume fixed rates, they are associated with relatively high pressure that can increases extravasation risk. Extravasation typically occurs during intravenous (IV) administration, when the IV cannula dislodges and punctures the vessel wall, causing leakage into extravascular tissue. While most extravasation cases cause minimal inflammation and erythema, further complications such as skin ulceration, tissue necrosis, and compartment syndrome, can occur.

According to American College of Radiology (ACR) estimates, of the 36 million contrast-enhanced CT (CECT) exams performed annually in the United States, extravasations occur in 0.1% to 1.2%, or about 36,000 to 430,000 procedures, per year. In this context, prevention strategies and best practices to identify at-risk patients are important; the Einstein Healthcare Network modified its practices to leverage saline to help reduce the number of extravasations. During monthly quality improvement meetings, Dr. Lee said, he and his colleagues reported lower extravasation rates for cardiac CT angiography (CCTA) exams compared to other CT exams.

“We wondered what we were doing differently in CCTA exams,” he said, noting that the difference lay in the performance methodology of saline test injections. Manual hand test injections were performed in all CECT studies except for CCTA examinations, which utilized power test injections. The group began experimenting with saline test injections using the power injector in all CECT studies. Their rationale: power injecting saline mimics the pressures of contrast injection more closely than hand injection. As such, the method has a better chance of identifying a weak IV line. Extravasation of saline during a test injection is less risky than contrast extravasation, which can have toxic side effects.

“Additional benefits of using a power-injected test bolus of saline is the standardization effect. By routinely using power injection for the test bolus, the test injections were consistent using the same flow rate each time as opposed to hand injections, which vary from technologist to technologist,” Dr. Lee said, noting the new test injection protocol has proven to reduce the facility’s extravasation rate by over 50%.

Hear Dr. Lee describe the Einstein department’s experience.

“There are more costs associated with a dual-head injector,” Dr. Lee said. “The argument I presented was, ‘if this works, we're going to be saving costs on the backend for not having to deal with as many extravasations.’” The saline test injection protocol has since been adopted across the network; emergency, in-patient, and outpatient sites all employ a saline test injection using the power injector prior to contrast administration.

Dr. Lee believes the saline test injection protocol can be generalized to other institutions to reduce variability and risk while helping clinicians achieve the best possible images. The expert panel agreed that leveraging the use of saline with the dual-head injectors leads to more efficient workflows and better patient care.

References:

1. Bae KT. Intravenous contrast medium administration and scan timing at CT: considerations and approaches. Radiology. 2010; 256:32-61.