The Accelerated Seldinger Technique (AST) is a medical technique for inserting catheters into blood vessels. Introduced in 2008, it was developed to be a faster, simpler, and safer improvement over the so-called Modified Seldinger Technique (MST), which is the current standard technique for over-wire insertion.
In AST, the various components of MST – including the introducer needle, guidewire, dilator and sheath – are combined in a single, engineered device.
The evolution of the Seldinger technique began in 1953, when Swedish radiologist Sven Ivar Seldinger, M.D. introduced the original Seldinger Technique as a means of reducing complications when inserting medical devices. Despite its safety benefits, however, it still entailed certain unavoidable risks. The Modified Seldinger Technique (MST) was developed as an improvement on the original technique. Its primary advantage is that the dilator and sheath are coupled together. The risks of the original technique remain.
Those risks include:
Hematoma. In MST, a hollow introducer needle is advanced into a target blood vessel. Vascular access is confirmed when blood ascends through the opaque shaft of the needle and appears at the needle's open end. By the time this has occurred, the needle may have punctured the back wall of the vessel, leading to a hematoma.
Needlestick injury to the clinician. Although safety introducer needles are typically included in MST kits, they are most often of the “active” type. That is, the clinician must do something to activate the safety mechanism. Needlestick injuries can still occur when active safety needles are used if there is mechanical malfunction or operator error. These injuries can infect clinicians with dangerous bloodborne pathogens such as HIV, hepatitis B, or hepatitis C, if their patients are also infected with these diseases.
Air embolism. Venous air embolism (VAE), or gas bubbles in the bloodstream, occurs when air enters the peripheral or central vasculature. During MST, the first risk of embolism occurs after the clinician inserts a hollow needle into the patient's vasculature. The uninserted end of the needle is open to the air, potentially allowing air to enter and cause a VAE. Later in the process, the guidewire and dilator are removed from the vein together. This causes a second open-to-air event, during which a VAE is once more a possibility,. VAE can cause catastrophic outcomes such as severe neurologic injury, cardiovascular collapse, and death. While the actual frequency of VAE in the U.S. is not known, estimates related to central venous catheterization are as high as 1 in 47 cases.
Bloodstream infection. When the non-inserted end of the needle is open to the air, it can also permit entry by bacteria, leading to a bloodstream infection. Much as with VAE, another opportunity for bloodstream infection occurs during MST's second open-to-air event, created by the withdrawal of the guidewire and dilator from the vein. Catheter-related bloodstream infections are fatal in up to 25 percent of cases.
Bleeding. Because there is no cap or valve on the end of the needle used in MST, excessive bleeding can occur if intravascular pressure is positive,. As with needlestick injury risk, bleeding can also expose the clinician to infected blood.
Contamination. The complicated MST process can also lead to contamination of the procedure's components. For instance, when the clinician grasps for the proximal end of the guidewire, the remainder of the 40-cm wire may twist off the sterile field, contaminating the wire’s distal tip.
Guidewire embolism. MST presents the risk that the guidewire will be lost in the vein while the clinician is pushing in the dilator or sheath over it. When a guidewire embolism occurs, the guidewire must be surgically removed.
Splash contamination. When the guidewire and dilator are removed, there is the potential for the clinician to be splashed with pathogen-containing blood.
Loss of cannulation. Another potential consequence of MST's multiple steps and component exchanges is loss of cannulation (access to the vein). For example, cannulation can be lost if the clinician inadvertently pulls the introducer needle out of the vein while reaching for the guidewire.
The Accelerated Seldinger Technique reduces or eliminates the above risks. For example, because all of the components of the Modified Seldinger Technique are incorporated into a single device, AST reduces the often-cumbersome exchanges and reaches for components that lead to complications such as contamination. The AST device also includes a passive needlestick safety lock – that is, a safety mechanism that is automatically engaged without requiring the clinician to do anything. This design feature prevents potentially deadly needlestick injuries. In addition, the AST device is designed to prevent hematoma and loss of cannulation from the delayed confirmation of vascular access that sometimes occurs during MST, as described above. With AST, blood can be viewed through the device's transparent sheath as it flashes up the needle. This “fast flash” provides quicker, reliable confirmation of vascular access and helps to prevent complications. Finally, AST reduces by 50% the open-to-air events that can cause an embolism.
Currently, one manufactured device, The WAND (Access Scientific, San Diego, Calif.), is available for performing AST. Different iterations of the device are used for insertion of extended-dwell IV lines and peripherally inserted central catheters (PICCs).
