Posts Tagged ‘radial artery friction’

Radial access  for both diagnostic  coronary angiogram  and  PCI has been increasing steadily.Many centres have adopted an  exclusive radial approach. Newer ,  radial specific  hard ware  is  being produced.(Link) .It is surprising , radial approach has  gained momentum  primarily outside  USA (Europe , Japan, India ).The advantages of radial access is primarily , patient comfort, less local site complication.

Prerequisite for radial approach.

The importance of  pre procedural Allen test to document dual blood supply is  well established but the less  appreciated  concept is  preprocedure  radial artery size  assessment . It  could be as important as Allen test .

The normal diameter of radial artery lumen is 2.4mm (Range 1.8-3.0) .Some population have still smaller radial lumen(India KA.Sambasivam et all mean 1.8mm). Compare femoral artery (8.5mm diameter, 4 times bigger )

Imagine this  situation ,  a 1.65 mm (5 F) diameter catheter trying to enter a 1.7mm radial artery !

Is it not a futile excercise ?   Many of the failed radial access is due to  radial artery /catheter mismatch .


There has been occasions , when the radial sheath is larger than radial artery itself !

So the size of the radial artery becomes vital in planning radial CAG.

What are ways one can estimate the size  of the radial artery ?

  • Volume of pulse (Still Useful , but can fool us some times!)
  • Thick radial walls (Monckeberg,s sclerosis)
  • Ultrasound imaging

Radial artery spasm

Radial artery has more medial  smooth muscle and further the fibres  criss cross the artery. Further , the radial artery is richly innervated by sympathetic  nerve terminals.

The major factor that determines likely hood of spasm is

  • Pain  intensity.
  • Amount of free space between sheath and vessel wall
  • The frictional force between sheath and artery wall is the powerful trigger for spasm and pain.

What is the biochemical mediators of radial artery spasm ?

It is logical to believe all  vascular  spasm are due to calcium .But it is not. Calcium blockers have  no definite relief for  spasm.Nor adrenaline mediated alpha receptor stimulation  has a major contribution for RAS. Phentolamine is useful

Is there a objective and quantitative method to assess radial artery spasm ?

Removal of the radial  requires some force.  Kiemeneij ( Measurement of radial artery spasm using an automatic pullback device. Catheter Cardiovasc Interv 2001;54:437–441.) demonstrated if one require > 1kg force to remove a sheath it correlates with clinically significant spasm.

What are the serious sequel of radial artery spasm ?

Radial artery rupture and radial artery avulsion has been reported when attempting to remove the sheath from spastic arteries

Management of radial spasm

There are two aspects to this problem

  • Prevention of  spasm
  • Treatment of established spasm

How to prevent or reduce  radial artery spasm ?

Radial artery is a very sensitive artery .The incidence of spasm can be up to 20%  The spasm can be due to

Hardware, technical ,anatomical factors.

Apart from  above  three factors,  the most important is anxiety related .The key principle is ,   sedating the  radial artery is as important as sedating the patient .

Sedating the patient

Explaining to the patient about the procedure can allay the anxiety. It is a fact , the tactile perception of catheter movement  in radial route is more than the femoral .In very anxious patients (Some centres use it routinely )  IV sedation (Midazolam)

Sedating  the radial artery.

Local anesthesia : Subcutaneous lignociane , though widely used has a drawback.It can aggravate pain, induce spasm , accidental entry into lumen may cause a hematoma  .All can potentially make the pulse feeble. So care should be taken in giving minimal lignocaine ( At a specific  point needle entry) with a short needle . One should watch , the grace with which experienced radial interventionist give the local anesthetics !

Arterial cocktail

The arterial cocktail consists of combination of Nitroglyceine (200 mcg) , Xylocaine (50 mg) Verapamil (5 mg) an. Heparin(5000 IU). Sodium bicarbonate (4%) is optional to neutralise the acidity of the solution

How to administer ?

Ideally spasmolytic cocktail should be given before the sheath is introduced immediately after puncture . As the drugs has to get in contact with the arterial wall .if cocktail is given after introduction of sheath one of the following may be done.

  • Give the drug as it enters the artery.
  • Pull back the sheath when injecting the drug.
  • Use a side holed sheath.

Technical issues to prevent radial artery spasm

Try to puncture in single prick . If the first puncture is not successful , don’t attempt to cross a spastic radial artery Remember (Unlike femoral ) successful puncturing of a spastic radial artery may be the beginning of a vexing and tiring procedure.So if we have lot of difficulty in getting in ,  please avoid the procedure and switch to femoral . (Spastic signals may spill over to left hand also !)

Remember unlike femoral cathetrisation , in radial access,  getting out the catheter could  be more tricky   than getting in !

Avoid procedures that would  require  multiple catheter , guide wire exchange .Complex lesions and in emergencies.( Some experts do Primary PCI through radial !) .Now  dedicated radial hardware are available.

Sheath selection (Visit :  Arrow International )

Long sheaths have been used in the past. It makes the spastic segment lengthier.Now short sheaths are increasingly used. Long sheaths (20-25cm ) give better suppport during catheter manipulation. Side holed sheaths  is a newer innovation. This maintains the  blood flow on the sides of sheath and reduces friction with vessel wall .Further, it can deliver the arterial cocktail to vessel wall and effectively prevent or reduce spasm.

Catheters : Use 5 F/6F. Rarely 7f are used.

Guide wires :Hydrophilic guidewire are radial friendly.

How to manage established severe spasm ?

For severe  spasm with sticky sheath / catheter

  • Increase the analgesia with morphine
  • Repeat NTG and Verapamil
  • Warm compresses over the forearm
  • Never pull with force
  • Wait for an hour and try pulling again (Often successful )

Last resorts

An axillary block

Vascular surgery

Reference and further reading

For excellent collection of radial access resources  please visit  www.radialforce.org

(Much of this blog’s content is based on this article )



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