How To Take Care of the Plaster Cast
January 23, 2008 by Dr Arun Pal Singh
Filed under Trauma
Plaster of Paris casts become supportive in three to five minutes, depending on the water temperature and the thickness of the cast. The cast does not fully dry out until 36 to 72 hours after application.
Examples of drying times:
- Forearm plaster – 36 hours
- Leg plaster – 48 hours
- Trunk plaster or plaster bed – 72 hours
When a dry cast is tapped with the knuckles, it gives a crisp, clear sound, but the damp cast gives a dull sound.
Damage due to Pressure
The supports used should be firm cushions or sandbags which have a protective covering. A sheet or old towel should lie between the plaster and any waterproof surface. If this is not done, dampness will collect and cause softening of the plaster.
At home, the patient must be advised not to rest the wet cast on a firm surface such as an unpadded chair. This will dent the cast and produce a ridge on the internal surface which may cause soreness. Unsuspected hazards, such as the ridge on the arm of a chair, can cause a dent in still-damp plaster.
The Drying Cast
The most common method is to allow the cast to dry naturally in circulating air.
The bed-patient has a cage over the plaster and the bedclothes are left open at the end. When possible the patient’s position should be changed every two to four hours to ensure even drying of both surfaces of the cast.
The out-patient should be instructed to expose the cast to warm air but not to sit with one surface of the cast constantly directed towards heat (e.g. a fire).
The dry Cast
Once dry, the cast will tolerate moderate pressure but for walking, a reinforcing sole or heel of wood or rubber should be added after the cast has dried.
Canvas or plastic coverings may be used for short periods to protect the cast from water. These must be removed regularly to prevent the plaster becoming damp as sweat fails to evaporate.
Forearm casts are particularly prone to getting wet at the lower edge which may fray. Small fragments may be detached and slip between the skin and plaster causing irritation. Thus care of the cast is essential for healing without complications.
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