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Wednesday, June 14, 2017

From the SIR Residents and Fellows Section

Teaching Topic: Influence of different flush methods on transfemoral cerebral angiography 

Lee HJ, Yang PS, Lee SB, et al. The influence of flush methods on transfemoral catheter cerebral angiography: continuous flush versus intermittent flush. J Vasc Interv Radiol. 2016; 27:651-657.

Click here for abstract

This manuscript compares different flush methods on transfemoral cerebral angiography (TFCA) in a single-blind randomized trial. Fifty patients were allocated to intermittent-flush (n = 25) and continuous-flush (n = 25). Researchers evaluated differences in procedure duration, amounts of contrast and heparinized saline used, , heparin dose, blood loss, fluoro time, radiation dose, and development of new embolic signal (NES) on diffusion-weighted imaging (DWI). There were noted differences in procedure duration, amount of contrast used, wasted heparinized saline, and aspirated blood. However, there were no differences in the occurrence of NES on DWI between the treatment groups.

Clinical Pearls

What is a new embolic signal (NES)?

NES identifies an area of brain hyperacutely affected by microembolism during a neurovascular, angiographic procedure. Diffusion-weighted imaging (DWI) is the gold standard to confirm these lesions. A new, diffusion-prolonged, foci can be considered a procedure-related embolic signal. Alternatively, transcranial Doppler (TCD) can be performed at the bedside and is easily repeated. Flushing with heparinized saline during TFCA is mandatory for protecting against thromboembolic complications.

What are the most common complications of cerebral angiography?

Access-site hematoma is the most common complication overall (4.2%), neurologic complications are seen in 2.63% with 0.14% being strokes with permanent disability. Factors associated with increased risk of neurologic complication include the indication of atherosclerotic cerebrovascular disease, indication of subarachnoid hemorrhage, and the comorbidity of frequent TIAs. Conversely, involvement of a trainee in the cerebral angiogram decreased the risk of complication1.


Preparation of the diagnostic catheter in each group. (a) The diagnostic catheter was connected to a 10-mL syringe filled with heparinized saline via a one-way connector in the intermittent-flush group. (b) The diagnostic catheter was connected to a Y connector in the continuous-flush group. The side arm of the Y connector was connected to the pressurized flushing line (A) and a connecting line (B) via a three-way connector. Another three-way connector was connected to the connecting line of the mechanical power injector (C) and a syringe for manual injection (D).

Questions to Consider

What types of flushing methods can be used?

Heparinized saline (5,000 U/L) was used for the flushes during TFCA in this study. A conventional continuous flushing system through a vascular sheath is formed by connecting the sheath to a plastic bag of heparinized saline surrounded by a pressure cuff inflated to 300 mmHg. A reducer permits a rate of 1 drop/sec into the sheath and catheter system. Some operators believe that the use of a continuous flushing method reduces the possibility of air embolism compared to intermittent flushing during the procedure, which requires blood aspiration into the flush syringe to ensure air bubbles are removed from the catheter prior to injection. It is generally accepted that intermittent flushing be performed whenever wires and catheters are removed and exchanged during the procedure.

How may the flush method affect the procedure?

Depending on the type of flush method used, procedure duration, amounts of contrast medium and heparinized saline used, heparin dose, blood loss, fluoroscopy time, radiation dose, and occurrence of new embolic signal (NES) on diffusion-weighted imaging (DWI) may differ and were monitored in this study. The authors found that although it is time-consuming to set up the more complex continuous-flush system, total procedure time in the continuous-flush group was significantly shorter than the total procedure time in the intermittent-flush group. Three NESs on DWI occurred in three of the 27 patients who underwent DWI in this study (11%). All lesions were asymptomatic and occurrence was lower than the previously reported prevalence (15%–26%). The amount of heparinized saline wasted, contrast used, contrast wasted, and blood aspirated were also significantly lower in the continuous-flush group.

Additional Citations:

Kaufmann TJ, Huston J, Mandrekar JN, Scleck CD, Thielen KR, Kallmes DF. Complications of diagnostic cerebral angiography: evaluation of 19,826 consecutive patients. Radiology. 2007; 243: 812-9.

Post Author:
Rajat Chand, MD
Diagnostic Radiology Resident, PGY-2
John H. Stroger Hospital of Cook County

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