FAS ENDOLUMINAL BRUSH
TECHNICAL NOTE 2:
A DETAILED RESPONSE TO THE FREQUENTLY ASKED QUESTION:
Why is the risk of fibrin emboli when using the FAS Endoluminal Brush very much lower than one would expect?
Introduction:
Understanding the risks associated with the safety of patients and healthcare workers is important when new medical procedures are introduced to the healthcare systems. Although the benefits of using the FAS Endoluminal Brush are usually apparent to prospective users so is a perceived risk of fibrin emboli.
This technical note explains how the physical properties of the FAS Endoluminal Brush virtually eliminate the chance of producing fibrin emboli during insertion and withdrawal. It also includes references and electronmicrographs taken when the safety issues were being studied in detail.
Why the risk of fibrin emboli when using the FAS Endoluminal Brush is very much lower than one would expect
The first major concern that a prospective user of the FAS Endoluminal Brush voices is the fear of fibrin emboli. Surely if you insert a brush into a catheter and push it through the whole internal length, then fibrin must be pushed into the blood stream? However, clinical experience with the FAS Endoluminal Brush has shown that this potential complication simply does not occur - at least not with any detectable detrimental effect (1-5). Indeed, attempts to measure the microemboli have proved unsuccessful (5).
One may argue that emboli do in fact occur but the pulmonary bed is generally able to cope with the amount of material generated. Obviously there is precedent for this belief since emboli must also occur when catheters are removed or exchanged over a guidewire or flushed or treated with thrombolytic chemicals and reports of serious embolic consequences of these routine practises are fortunately rare.
The biological safety system is nonetheless significantly helped by both the design of the FAS Endoluminal Brush and the recommended use procedure, both of which are designed to minimise the generation of fibrin debris during the forward motion of the brushing procedure.
Brushes, the most commonly used cleaning device in all aspects of life, are designed to clean by virtue of the bristle ENDS. The body of the bristle generally retains material rather than releasing it - anyone who has used and then cleaned a paintbrush will appreciate this point!! The FAS Endoluminal Brush is spirally wound such that the bristle ends are orientated to the rear of the brush and therefore do not abrade the surface of the biofilm in a forward motion (Figure 1 and 2). When the motion is reversed and the FAS Endoluminal Brush is withdrawn from the catheter, then all of the bristle ends are "turned" to abrade the biofilm and thus to remove material which is then retained by the body of the bristles (Figure 3 and Electronmicrograph #1). This natural physical property of brushing is enhanced in the design of the FAS Endoluminal Brush by the use of an oversize bristle length. If the correct FAS Endoluminal Brush is selected for a designated catheter then the brush head diameter will be approximately one and one half to two and half times the internal diameter of the lumen. This "flattens" the bristles such that the vast majority of the biofilm surface has contact with only the body, and not the ends, of bristles. Any effect upon the biofilm is generally limited to the cutting of channels through the film (Electronmicrograph #2).
When the motion is reversed all of the bristle ends (due also to the orientation of the spiral wind) come into contact with the biofilm (Figure 3).
Catheter with biofilm and FAS Endoluminal Brush with correct size bristles
Figure 2
FAS Endoluminal Brush being inserted showing "flattening" of bristles such that they "bounce" over the surface of the biofilm.
Figure 3
FAS Endoluminal Brush being withdrawn showing reversal of bristles and deposition of fibrin in bristle body.
Listed below are publications, which address the safety issues of using the FAS Endoluminal Brush, including the common concern of fibrin emboli.
References
1. Tighe MJ et al. An endoluminal brush to detect the infected central venous catheter in situ: A pilot study. BMJ 1996:313:1528
2. Kite P et al Evaluation of a novel endoluminal brush for the in situ diagnosis of catheter related sepsis. J Clin Pathol 1997:50:278
3. Farmer CKT et al Endoluminal brushing of blocked permanent indwelling haemodialysis catheters saves money Nephrol Dial Transplant 1997:12:2040
4. Dittmer ID et al The use of catheter brushes to diagnose internal luminal colonisation of haemodialysis catheters. Renal Association Meeting Oct 1996 Abstract 25
5. Dobbins BM and Kite P Endoluminal Brushing in Catheter-Related Sepsis: A "Sweeping" Statement. Nutrition 1998:14:11
Scanning Electronmicrograph #1 showing biofilm retained on and between the shaft bristles of the FAS Endoluminal Brush
Scanning Electronmicrograph #2 showing tracks cut in biofilm by forward motion of a FAS Endoluminal Brush.
FAS ENDOLUMINAL BRUSH
TECHNICAL NOTE 2:
A DETAILED RESPONSE TO THE FREQUENTLY ASKED QUESTION:
Why is the risk of fibrin emboli when using the FAS Endoluminal Brush very much lower than one would expect?
Introduction:
Understanding the risks associated with the safety of patients and healthcare workers is important when new medical procedures are introduced to the healthcare systems. Although the benefits of using the FAS Endoluminal Brush are usually apparent to prospective users so is a perceived risk of fibrin emboli.
This technical note explains how the physical properties of the FAS Endoluminal Brush virtually eliminate the chance of producing fibrin emboli during insertion and withdrawal. It also includes references and electronmicrographs taken when the safety issues were being studied in detail.
Why the risk of fibrin emboli when using the FAS Endoluminal Brush is very much lower than one would expect
The first major concern that a prospective user of the FAS Endoluminal Brush voices is the fear of fibrin emboli. Surely if you insert a brush into a catheter and push it through the whole internal length, then fibrin must be pushed into the blood stream? However, clinical experience with the FAS Endoluminal Brush has shown that this potential complication simply does not occur - at least not with any detectable detrimental effect (1-5). Indeed, attempts to measure the microemboli have proved unsuccessful (5).
One may argue that emboli do in fact occur but the pulmonary bed is generally able to cope with the amount of material generated. Obviously there is precedent for this belief since emboli must also occur when catheters are removed or exchanged over a guidewire or flushed or treated with thrombolytic chemicals and reports of serious embolic consequences of these routine practises are fortunately rare.
The biological safety system is nonetheless significantly helped by both the design of the FAS Endoluminal Brush and the recommended use procedure, both of which are designed to minimise the generation of fibrin debris during the forward motion of the brushing procedure.
Brushes, the most commonly used cleaning device in all aspects of life, are designed to clean by virtue of the bristle ENDS. The body of the bristle generally retains material rather than releasing it - anyone who has used and then cleaned a paintbrush will appreciate this point!! The FAS Endoluminal Brush is spirally wound such that the bristle ends are orientated to the rear of the brush and therefore do not abrade the surface of the biofilm in a forward motion (Figure 1 and 2). When the motion is reversed and the FAS Endoluminal Brush is withdrawn from the catheter, then all of the bristle ends are "turned" to abrade the biofilm and thus to remove material which is then retained by the body of the bristles (Figure 3 and Electronmicrograph #1). This natural physical property of brushing is enhanced in the design of the FAS Endoluminal Brush by the use of an oversize bristle length. If the correct FAS Endoluminal Brush is selected for a designated catheter then the brush head diameter will be approximately one and one half to two and half times the internal diameter of the lumen. This "flattens" the bristles such that the vast majority of the biofilm surface has contact with only the body, and not the ends, of bristles. Any effect upon the biofilm is generally limited to the cutting of channels through the film (Electronmicrograph #2).
When the motion is reversed all of the bristle ends (due also to the orientation of the spiral wind) come into contact with the biofilm (Figure 3).
Catheter with biofilm and FAS Endoluminal Brush with correct size bristles
Figure 2
FAS Endoluminal Brush being inserted showing "flattening" of bristles such that they "bounce" over the surface of the biofilm.
