The National Institute for Clinical Excellence is examining thrombin injection for pseudoaneurysms and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about thrombin injection for pseudoaneurysms.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendation
• the identification of factual inaccuracies
• additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows:

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
• The Advisory Committee will then prepare draft guidance, which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.

For further details, see the Interim Guide to the Interventional Procedures Programme, which is available from the Institute's website (www.nice.org.uk/ip).

Closing date for comments: 24 February 2004

Target date for publication of guidance: May 2004

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence on the safety and efficacy of thrombin injections for pseudoaneurysms appears adequate to support the use of this procedure provided that the normal arrangements are in place for consent, audit and clinical governance.

A pseudoaneurysm is a collection of blood and blood clot that has formed outside a blood vessel, usually following an injury. The collection is connected by a channel to the blood vessel, so blood flows through it. A pseudoaneurysm may rupture and bleed. Pseudoaneurysms (also called false aneurysms) differ from true aneurysms in that blood within a true aneurysm is contained by the weakened wall of the blood vessel. The most common cause of pseudoaneurysm is femoral artery puncture during cardiac catheterisation. Pseudoaneurysms may also occur following other procedures that involve puncture of an artery, including removal of an arterial blood pressure line or intra-aortic balloon pump, or following accidental trauma.

Many pseudoaneurysms resolve spontaneously by thrombosis and need no treatment. If treatment is required, treatment options include compression under ultrasound control, embolization of the pseudoaneurysm with a variety of materials, or surgical repair.

In this procedure, thrombin (a blood clotting agent) is injected under ultrasound guidance into the pseudoaneurysm. This causes thrombosis of the pseudoaneurysm cavity, which seals the arterial puncture site. The resulting clot is gradually reabsorbed.

Four historically controlled studies were identified comparing thrombin injection with compression. All four studies reported greater success in treating pseudoaneurysms with thrombin injection. In these studies, success rates ranged between 93% (27/29) and 100% (24/24) using thrombin injection, and between 63% (25/40) and 95% (102/107) using compression. For more details, refer to the sources of evidence (see Appendix).

The Specialist Advisors did not note any concerns regarding the efficacy of this procedure.

In the studies identified, the main complications reported were: intra-arterial thrombin injection necessitating thrombectomy for artery occlusion, 2% (3/131); pseudoaneurysm rupture after thrombosis, 1% (1/131); groin abscess, 1% (1/114); leg ischaemia, 1% (1/114); blue toe, 1% (1/114); and buttock pain, 1% (1/114). For more details, refer to the sources of evidence (see Appendix).

The Specialist Advisors listed the main potential adverse events of this procedure as thrombosis of the damaged artery, and treatment of a clinically infected pseudoaneurysm (because infection can cause late recanalisation and rupture). The Advisors also noted that there was controversy over the safety of the use of bovine thrombin.

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

• Interventional Procedure Overview of thrombin injections for pseudoaneurysms , December 2002

Available from: www.nice.org.uk/ip171overview