Health

By J. Glen House, MD

Spinal Cord Injury Secondary Condition: Skin and Pressure Ulcers

A pressure ulcer is a localized area of skin damage that can quickly progress to a serious problem for an individual with a spinal cord injury. Prevention of a pressure ulcer is one of the most important issues after a spinal cord injury that requires lifelong attention. With knowledge about what causes a pressure ulcer and what to do to prevent a pressure ulcer, individuals with a spinal cord injury can live a very productive and fulfilling life without interruption. If pressure ulcers are not taken seriously and they develop, it will require a significant amount of time and money to help them heal and may significantly alter or interrupt work and life activities.

What is a pressure ulcer?
A pressure ulcer is damaged tissue (skin, muscle, blood vessels, etc.) caused by excessive pressure.

What is normal skin made of?
Skin is divided into two specific layers. The outer layer of skin is called the epidermis. The outermost layer of the epidermis is made up of dead cells that are continuously being replaced by cells underneath this layer. In fact, the skin that we look at and touch on the human body is made up of dead cells that shed about every two weeks. The inner living part of the epidermis contains melanin (pigment which colors our skin) and cells that function as the first line of defense of our immune system. The layer of skin beneath the epidermis is called the dermis. The dermis contains sweat glands, oil glands, nerve endings and blood vessels.

What changes occur in the skin after a spinal cord injury?
Many changes occur after a spinal cord injury to the skin below the neurological level of injury. Changes occur in the collagen, which is the supporting structure of the skin. There are also many chemical changes, including involvement of enzymes and amino acids. Changes occur in the normal ability of the skin to control its temperature. The normal sweating reflex is lost in individuals with spinal cord injuries at T6 and above. This limits the ability of the skin to cool itself by way of sweating; body temperature can increase quickly causing spinal cord injured patients to become overheated.

What causes pressure ulcers?
Pressure ulcers are caused by direct pressure on the skin from objects outside the body. Pressure ulcers develop over bony areas that are likely to be pressing against the outside object such as a bed or wheelchair cushion.

Shear is another factor that leads to pressure ulcers. Shearing occurs when a force is applied that leads to a parallel but opposite sliding motion. For example, when someone is in bed and the head of the bed is raised from a 30° incline to a 70° incline, the skin over the sacrum (bottom part of the spine) and coccyx (tailbone) slides upward while the bony areas are sliding down. This puts a strain or force on the skin that can damage blood vessels within this area of the skin. Damage to blood vessels can lead to damage of tissue because of the lack of oxygen and nutrients delivered.

Another very important factor that increases the risk of developing a pressure ulcer is moisture against the skin. This moisture may pool next to the body if the surface the person is lying on is unable to wick moisture away. Another very common cause of excessive moisture is from urinary or bowel incontinence.

Other factors that need to be evaluated include appropriate nutritional status, presence of anemia (low oxygen carrying red blood cells) and age of the skin. 

What areas are most likely to develop pressure ulcers?
When lying in a bed, pressure ulcers are most likely to develop over specific bony areas. These bony areas are shown in the diagram below. The two most common positions when lying in a bed are supine (lying flat the back) and side-lying. When lying supine, the most common locations of pressure ulcers are the sacrum (bottom part of the spine near the tailbone), heels and occiput (back of the head). When lying on the side, the most common locations of pressure ulcers are the trochanter, inside of the top knee and ankle, and outside of the bottom knee and ankle.

In the seated position, pressure ulcers develop in the tissues that lie over the ischial tuberosity (bones that we sit on).

How is the severity of pressure ulcers described? 
The National Pressure Ulcer Advisory Panel (NPUAP) has described the severity of pressure ulcers in stages 1-4. Below is a description of the four stages according to the NPUAP. It is important to note that pressure ulcers do not necessarily progress from stage 1 to stage 4, and healing does not occur in the reverse order.

Stage 1: Non-blanchable erythema not resolved in 30 minutes; epidermis intact; reversible with intervention (not detectable in persons with darkly- pigmented skin).

Stage 2: Partial-thickness loss of skin involving epidermis, possibly into dermis; may appear as blisters with redness, abrasion or shallow crater.

Stage 3: Full-thickness destruction through dermis into subcutaneous tissue that may extend down to, but not through, the underlying fascia. The ulcer presents clinically as a deep crater with or without undermining of adjacent tissue.

Stage 4: Full-thickness skin loss with deep tissue destruction through subcutaneous tissue to fascia, muscle, bone, joint or supporting structures. Undermining and sinus tracts may also be associated with stage 4 pressure ulcers.

A simplified explanation of the four stages of a pressure ulcer
Stage 1: redness that does not blanch (turn white or pale when pushed on) and if it does not return to normal skin color after 30 minutes. The top layer of skin (epidermis) is intact with no open areas.

Stage 2: open area of the top skin layer. Very shallow crater in the skin.

Stage 3: this is a deeper open crater then the superficial stage 2 crater. This ulcer can travel up to but not through muscle.

Stage 4: this is a deep ulcer that does travel into or through muscle, bone, joint or supporting structures such as ligaments and tendons.

How are pressure ulcers prevented?
Pressure relief
The most important action to prevent pressure ulcers is an appropriate and frequent “pressure relief” maneuver. A “pressure relief” maneuver is a change in position to eliminate the direct pressure on the skin lying over a bony area. “Weight shift” is a term used to describe a maneuver in which the patient or caregiver physically lifts or moves the body off of the bony area. It is often recommended that weight shifts take place every 15-30 minutes and last for at least 30 seconds. Some individuals perform weight shifts much more frequently then 15 minutes but for a shorter period of time.
Regardless of recommendations, the patient must perform as many weight shifts as required to prevent developing a stage one pressure ulcer (redness that does not blanch or go away after 30 minutes).

Initially it is recommended that patients are turned every two hours while in bed. The duration between turns may increase after a patient leaves the rehabilitation unit and is discharged home. Increasing the duration between turns needs to be closely monitored and can be gradually increased if no redness is present. The type of mattress is very important in determining this time variable. In fact, individuals who travel or have a change in mattress type must always be reassessing the appropriate time to turn or change positions.

Neuropathic pain
Neuropathic pain is often described as a burning, tingling or shooting painful sensation. Others have described this pain as very bad sunburn. It is this author's opinion that some degree of neuropathic pain is helpful in the prevention of pressure ulcers. Neuropathic pain often intensifies or worsens with prolonged sitting and therefore can act as a protective measure to remind the spinal cord injured patient to change positions and perform a pressure relief maneuver. Therefore, treatment of neuropathic pain with medications should take into consideration that some degree of neuropathic pain is beneficial.

Nutrition
It is important to maintain a well-balanced diet with plenty of fluids. It is important for skin health to maintain adequate calorie, protein and vitamin intake.

Support surface
Surfaces that the spinal cord injured patient will be sitting or lying on need to be able to spread out the pressure. These supporting surfaces should be evaluated prior to use, and continuous maintenance is required. At the first sign that these supporting surfaces are not maintaining ideal pressure relief, they should be replaced. Pressure mapping is a technology that uses a thin pressure-sensing mat connected to a computer that gives information about the degree of pressure. Pressure mapping is often used to assess the appropriateness of a particular cushion or mattress. This can be very useful in determining which cushion is most appropriate for which patient.