This article is part of the operation script for grafting an abdominal aortic aneurysm. The article can be used on its own, or to go to the next part of the operation, click on NEXT PART OF THE OPERATION at the bottom of this page.

AORTIC ANEURYSM 070 - SUTURING REVIEW

The tissues

The anastomoses of the graft onto the aortic or arterial wall are dependent more on the condition of the blood vessel than on the graft.

Modern grafts do pose their own suturing problems, but they are of lesser importance than previously.

For instance, the aortic end of a graft should be sutured through an outer transverse ridge to prevent buckling.

Grafts do not delaminate, so a needle can be passed through the fabric in either direction.

In contrast, in blood vessels, needles passing from outside to inside run the risk of causing the intima or atheromatous plaques to detach from the vessel wall.

The blood vessel that is stitched is always affected by aneurysmal or occlusive disease to some degree.

Paradoxically, a healthy vessel wall is more delicate than one with minor atheromatous disease.

Severe aneurysmal disease in the upper subrenal aorta may make the anastomosis impossible.

The sutures just cut through the weakened tissue.

Even relatively normal looking subrenal aorta is difficult to anastomose.

Intermediate amounts of disease affect the wall ranging from a consistency resembling wet blotting paper to severe calcification.

However, even the most unlikely and unhealthy tissues can provide a satisfactory anastomosis, given satisfactory needles, sutures and impeccable technique.

Needles

The needles should be round bodied to minimise a cutting action on the vessel wall.

Also accidental cutting of a previous stitch by a cutting needle is avoided.

Remember that a round bodied needle may transfix a previous stitch.

The aortic needle should be strong enough to pass through thick atheromatous tissue.

It should be long enough and strong enough to take large bites of aortic tissue.

The needle must be able to pass through the anterior longitudinal ligament of the vertebrae in the case of a posterior rupture.

A 25mm. half curved round bodied needle is satisfactory.

The femoral anastomoses are more delicate, and require a smaller, less traumatic needle.

A 17mm half curved round bodied needle is satisfactory.

The atheromatous and calcified plaques round the lumbar arteries are often so tough that a round bodied needle will not pass through.

A strong tapercut needle is usually needed to stitch off these vessels.

Sutures

A non-absorbable suture is essential.

The healing of the graft to a blood vessel is slower than the inevitable reduction in strength of an absorbable suture.

The strength of the suture should be high enough.

ie To withstand the stresses of pulling of the suture though the tissues and also the pressure of blood in the vessel.

Monofilament sutures, such as polypropylene, have a very smooth surface.

The material gives a low friction when passing through the tissues.

The stitches of up to half an anastomotic line can be inserted before tightening the tissues onto the graft.

A Blalock nerve hook is useful to do this.

The monofilament sutures can slip if the assistant lets go accidentally.

They can snap if kinked.

They need at least 6 throws for a secure knot.

Braided sutures', such as Ethibond, have a rougher surface with much higher friction in the tissues.

They have largely been superceded by monofilament sutures.

The aortic anastomosis requires a suture with a knotted breaking strength of 1500 grams.

This is close to the breaking strength of 3/0 polypropylene (1600grams).

The femoral or iliac anastomoses require a knotted breaking strength of 750grams.

4/0 polypropylene is suitable, with a breaking strength of 1200grams.

Stitching off the lumbar arteries requires a stronger suture.

This is because of tough atheroma and calcification around their orifices.

Use 2/0 polypropylene with a knotted breaking strength of more than 2600grams.

Satisfactory sutures

Every surgeon has his own preference, but we find the sutures below satisfactory.

Ethicon W89772/0 Monofilament polypropylene 90cm. long with 2 25mm.half curved tapercut needles

Ethicon W8522 3/0 Monofilament polypropylene 90 long with 2 25mm. half curved round bodied needles

Ethicon W8935 4/0 Monofilament polypropylene 90 long with 2 17mm. half curved tapercut needles.

Suturing technique

The success of the anastomosis depends very much on the surgeon’s technical skill.

He/she has to be very familiar with and completely confident in the needle and the suture.

While performing an anastomosis, he/she must notbe preoccupied with or be let down by these items.

Any new or alternative suture should be viewed with suspicion and be thoroughly assessed before the operation starts.

There is usually just one chance to place a suture correctly.

There is no room for uncertainty about placement of individual stitches or for inaccurate insertion.

There are various fail safe techniques.

Eg. Tie the first knot of an anastomosis at the centre of the suture.

Stitch with the first needle and that half of the suture.

Keep the second needle and the second half of the suture still attached to the knot.

If the first needle or suture break during an anastomosis:

You can use the second needle and the second half of the suture.

Do not use dissecting forceps to hold any part of the suture that will be incorporated in the anastomosis.

They can damage and weaken the suture.

If a knot appears in the suture, pulling it through the anastomosis may tear the vessel.

Use the second needle and suture or a complete new stitch instead.

Suturing the aorta

Place the stitches 5mm. from the edge of the graft to prevent fraying

Place the stitches 5 – 10mm. from the edge of the aorta to prevent tearing.and to encourage bunching of the tissue for a watertight anastomosis.

Place the stitches 3mm. apart on the graft.

A 16mm. graft has a circumference of 50mm. (pi times the diameter, say 3 times ).

This means 8 stitches on the anterior wall and 8 on the posterior wall.

Insert the suture into the graft from outside to inside.

This will ensure the needle will go through the aorta from inside to outside (preventing lifting the intima or atheroma)

Pull the suture through the graft before passing the needle through the aortic wall.

This will minimise the tearing stress on the aorta.

If avoidance of delaminating a blood vessel means stitching backhand, consider standing on the opposite side of the patient.

You will avoid the delamination and still stitch forehand.

Adjust the distance between bites on the aorta to allow for differences in diameter compared with that of the graft.

Avoid passing the needle through the graft and the aortic wall in one go.

This is often unsuccessful and has to be repeated singly, wasting time and damaging the aorta.

Take as deep a bite as you can without bending the needle.

Exit the aorta from the inside at least 10mm. distal to the entry site.

Catch the end of the needle with your dissecting forceps and then with the needle holders to prevent it popping back into the aortic tissues.

Avoid bending or breaking the tip of the needle.

If you do:

Use a new stitch for the next bite and tie the first suture to it with 6 throws.

Knot tying

In these aortic anastomoses, there is one major knot at the end, and two less major

knots at the beginning of each suture line.

The main dangers are:

The suture not being tight enough.

The maximum strength of the tissues is about 750grams.

The maximum strength of the suture is about 1200grams or more.

The surgeon must be able to tighten the suture enough knowing that the suture is much stronger than the tissues.

If the suture, especially a polypropylene suture, is not tight enough:

Use a blunt Blalock nerve hook like a crochet hook to tighten the sutures.

The suture breaking.

Deliberately break a knotted suture before the operation to find out how strong it is.

Make sure all first throws lie correctly in line before tightening them.

Ie the suture only changes 30 degrees in direction in the throw.

Throws lying out of line, ie with a 450 degree change of direction in the throw, halve the strength of the suture.

Be gentle, particularly when you are under extreme pressure.

Check you have been given the correct suture.

The suture slipping.

Use double or triple turns on the first throws, particularly if you are using a coated monofilament suture.

Hand tie all sutures.

Tie the sutures without slackening the pull on the suture at any stage.

Keep calm.

The graft tearing.

The graft is most unlikely to tear.

If the graft does tear:

Pass the needle through the graft further away from its edge.

The blood vessel tearing.

Preventing blood vessel tears.

The blood vessel tissues may be extremely poor and tear easily.

Reduce the stresses on the tissues by lining all first throws up correctly.

Push the suture beyond the knot wound when tightening.

This will counteract any upward pull on the stitch.

Be gentle, even when you are at extremes of pressure.

Remove any calcified plaques that may be interfering with how the suture runs.

Take a deeper bite and tie the new stitch with greater care and caution.

With a monofilament suture, take two bites and snug the tissues down with great care.

If the blood vessel tears:

Stitch a patch of graft into the area to bolster the tissues.

Stitch the aorta higher up in an untorn area.

You may not be able to retrieve the situation if the tissues disintegrate.

Suturing the femoral anastomosis

These anastomoses are much more delicate than for the aorta.

Use 4/0 polypropylene with a 15mm. 2 round ended needles.

Place the sutures 1mm. apart and 1mm. from the edges of the graft and the vessels.

The assistant's role

The surgeon should control the tension, the direction of pull and the placement of the suture on the tissue and graft.

The assistant must hold the sutures with the exact tension and direction that the surgeon has used.

No swaying of the suture. No alteration of the tension.

The assistant should use fingers or arterial dissecting forceps (e.g. Atraugrip forceps) to hold the sutures.

The forceps should only hold that part of the suture that will not be involved in the anastomosis.

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