Cullen's circle

Published: December 2007 by R. Legerstee, RN, MSc in Wound Healing & Tissue Repair

The insights that we have today (many of which we now consider self-evident) have not always been as clear. An insight has always started somewhere, started by someone who began to think about a notion, concept or another complex process. It also takes time before new insights are actually generally accepted. This also applies to insights about wound care.

The composition of wound exudate in chronic and acute wounds is totally different

Attention was first devoted to the wound exudate environment more than 10 years ago, with a publication by Schultz and Mast (1996). In this publication, it was clearly demonstrated that the composition of the wound exudate of chronic wounds (see: 'Chronic wounds do not exist') differs significantly from the exudate in 'acute' wounds (see figure 1).

MMPs and the chronic wound

During the first couple of days after injury (see the wound healing process in the short specification) quite a bit of 'housekeeping' has to take place and that is primarily done by a group of proteins (enzymes) called MMPs (see: the principle of MMPs in WM10). MMPs are needed for recovery and, in an acute wound the role of the MMPs suddenly comes to an end. This is not the case in a chronic wound. If the wound continues to break down, then the MMP level will rise excessively and it will often not repair at all. The wound has become complicated.

The origin of the vicious circle

During the years following the publication by Schultz and Mast, it became evident that the MMPs result in a some kind of vicious circle for the complicated wound. Damaged cells produce the MMPs, but in addition they also provide nutrients for bacteria, which are liberated by the bacteria by producing of MMPs, i.e. they dissolve their surrounding space and use that as nutrition. Also, the environment that is introduced by wound dressings can be harmful to the wound. We have already known for a long time that dry gauzes are very harmful to the tissue and also to the cells (Wood, 1976) as yet.

If we are all conscious of that, then we should also be able to find a way out of this situation. In other words, if we combat damage, physiological imbalance and the micro-organisms, we have found something that could lead to the problem being resolved (and thus exiting the vicious circle).

What does the vicious circle look like?

The evidence that has been collated to date for the existence and continuation of a complicated wound can be clearly shown in a picture of a vicious circle (figure 2):

Because it is a vicious circle, it doesn’t matter where you start to read. However, let us start, for example, with the proteases (predominantly MMPs) that are released when cells (fibroblasts, keratinocytes, macrophages, etc.) are damaged. These MMPs not only damage the newly formed tissue, but growth factors (being proteins themselves) are also destroyed.

Bacteria are greatly attracted to damaged tissue. Bacteria also produce MMPs in order to release the nutrients from the cells/tissues. The micro-organisms also excrete toxins, through which increasingly larger numbers of leucocytes have to be mobilised to the area of the wound. The leucocytes try to kill the bacteria, also resulting in serious damage to the 'normal' cells and tissues. And this is what makes the circle "vicious", because the damaged cells again produce yet more MMPs.

It becomes even easier if we simplify figure 2 to the figure shown below:

Figure 3 shows a road sign that we all know: that of a roundabout. A roundabout is also rather like a vicious circle - after all, you could continue to drive around it for as long as you want to. However, a roundabout does offer exits, and is, therefore, different from a real vicious circle, from which an exit doesn’t seem evident or possible

Intuitively, as a car driver we know that when we enter a roundabout, there will always be a time at which we can leave the roundabout again. You would also receive rather strange looks if you arrive at work late and say that you have just driven around the roundabout for several hours because you weren’t able to find the exits!

If we consider this, why do we therefore frequently not find the exits when treating a wound? Even in that case, we are aware of them: damage, imbalance and micro-organisms.

The ways out of the vicious circle

Using the Clean, Close and Cover model discussed above, it is easy to explain why, based on these insights, it is possible to close wounds that have sometimes existed for a very long time (years):

• The use of antimicrobial agents (i.e. SILVERCEL™) can result in a significant reduction in microbes, which can, therefore, also no longer produce their toxins and MMPs.
• The introduction of the ideal moist conditions (such as, for example, with TIELLE™) will ensure that the cells can once again do their job and do not fall prey to the barren situations that dryness or soaking wet conditions introduce.
• Finally, the physiological imbalance can (on the basis of evidence) be abolished through the use of materials that can capture the MMPs (such as with PROMOGRAN PRISMA™).

In short, the seemingly complex model in figure 2 (however true and correct it might be) can, after all, also be shown as follows in figure 4. There are three possible ways out of the vicious circle!