Part 1
In this knowing your Jargon #KYJ series we look at the options for wound dressings.
Everywhere I nurse, treatment rooms and clinics have a poster helping nurses recognise different stages of wound healing and usually offering a suggestion of what dressing to use. It's a confusing choice and often we come on shift to see that another nurse has changed to a different product.
So in this mini-series, we look at the different styles of dressing, and when they are indicated.
To get the ball rolling we must understand that wounds need 5 important things to heal.
*oxygen delivery
*nutrition (nutrients)
*moist wound bed
*warmth
*absence of infection
Oxygen / Nutrient
Oxygen and nutrients for cell growth need to be delivered to the wound systemically via the vascular network. Arteries and arterioles deliver to the micro fine capillary beds to diffuse in to the wound. This supports the proliferation of new tissue growth, and feeds hungry immune cells acting watch over the construction zone, preventing bacteria from colonising and initiating infection. In diabetics and other people with poor vascular flow, there exists a chronic reduction in tissue oxygen delivery. If the wound bed oxygen concentration should drop below an oxygen tension of 40mmHg, then wound stop healing. They become indolent and dormant.
For oxygen to get into a wound, blood needs to be adequately drained from the wound. In patients with heart failure (especially right heart), there is often venous engorgement/congestion. This venous congestion (particularly in lower limbs) usually decreases the ability of blood the cycle through the wound. Venous blood is notoriously hypoxic (without oxygen), so venous congested wounds will swell, hold and produce lots of exudate, and healing grinds to a halt. These patients need compression bandaging or stockings to promote venous return. We have to get the oxygen right.
Moist wound bed.
Within 24-48 hours of tissue injury, fibroblast cells commence work to create a protein base to the wound bed. It is called collagen and you could think of it as the frame or foundation of a deck verandah. On top of the frame work, eventually the decking timber will be attached. In wounds this construction is called granulation.
Granulation needs to take place in a moist/warm environment. Ultimately the skin cells that form the decking need to slide (migrate) across the collagen frame to complete the surface of the wound bed (epithelialisation). The process can take weeks, but in small wounds with close edges, the seal in just 48 hours. The wound bed needs to be slippery. This is where moisture comes into play.
As nurses we need to choose a cover that maintains wound warmth (>30 deg), and traps moisture to maintain the slippery environment fibroblasts (builders) need.
Too wet and the healthy tissues in the wound swell and cease to function. Too dry and the migration, and epithelialisation can't happen.
In our next part of the series, we will look at the dressings that do this task.
Absence of infection
If a wound is colonised by pathogenic (disease causing) bacteria, it won't start repairing. In infections, the immune system is activated to search and destroy bacteria, and using many signalling chemicals (cytokines) to aid communication between white blood cells (chemotaxis), the process of tissue repatriation ceases while active infection fighting occurs. Infection is the enemy of wound healing.
When assessing wounds, especially chronic wounds like leg ulcers, and decubitus ulcers, get into the practice of taking a baseline bacterial culture swab. If colonisation is present then the patient should be started on antibiotics for reduction in bacterial numbers. A colonised wound is not an infected wound, but given moisture, time and warmth (all things a healing wound needs), that little bacterial colony becomes a rampant infection. When wound bacteria do the dirty, they secrete toxins into the wound bed that destroys the fresh new growth, causes Vasoconstriction which reduces oxygen to the wound, and fills up the wound with excessive toxic exudate.
Wound cleaning
Warm water/saline irrigation under pressure of a 20ml syringe, and a blunt 18g needle is needed to irrigate /clean the wound. An uninflected wound often needs very little cleaning if it is healing well (every 3-7 days). But in infected wounds, healing is not our goal, cleaning is. Refrain from swabbing with gauze. This cleaning of the wound bed 1-2 times daily during active infection inhibits pus, exudate, and aids in reducing bacterial numbers.
Ok that is it for the first instalment. A primer as it were.
Next episode we will look at the start of our wound dressing list starting with
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