Cryotherapy is a fancy word for the non-fancy practice of “putting ice on someone”. We often think about ice decreasing tissue damage, swelling and pain after injury, but does it actually achieve this? Is ice useful in acute injuries? If it is, how long should ice be applied? Should you really eat the frozen peas or chicken nuggets you used to ice your ankle? All these questions and more (or less) are answered here from the latest research on ice (see below for references).
Does ice application reduce swelling?
Ice application reduces the tissue temperature, which decreases cell metabolism in the area surrounding the injury, and decreases the amount of secondary damage in the tissue surrounding the injury. Animal studies demonstrate a significant decrease in cell metabolism when tissue temperature is lowered to 5 to 15 degrees.
There is level 2 evidence that ice DOES NOT reduce swelling.
The main effect of ice is to decrease nerve conduction velocity, thereby reducing pain from surface tissues. This allows your patient to perform their exercises and mobilise the area, which has a secondary effect of reducing swelling.
What is the best way to apply ice?
Not all ice packs are created equal. For decreased nerve conduction velocity, we are trying to achieve a tissue temperature of 10 degrees.
Frozen peas or gel packs help yourself and your patients to avoid the mess of cleaning up slippery pools of water all over the floor, which is a wonderful thing. Is it all good news on the frozen peas front though?
Crushed ice will achieve our goal skin temperature within 5 minutes, however other types of icing eg gel packs, frozen peas do not get the skin temperature lower than 13 degrees, which unfortunately is not low enough to have an adequate effect on nerve conduction velocity.
Therefore the best way to apply ice is crushed ice in a plastic bag applied directly to the skin, followed by quickly getting someone nearby to mop up the mess you have just created.
How long should we apply ice?
We have all probably used or recommended at one point in time the application of ice for 20 minutes on every hour, or 20 minutes on/20 minutes off.
Using crushed ice, our skin temperature can be reduced to our goal temperature within 5 minutes. If the goal is to reduce nerve conduction velocity and pain, and allow performance of exercise/mobility, this is enough.
If you are trying to achieve a decrease in tissue temperature at the injury site, the depth of the injured tissue and the amount of bodyfat the patient has are also factors in the length of time that ice is applied.
If you have an injured athlete that is very lean, with an injury close to the surface eg lateral ankle ligament injury, you may achieve this with shorter periods of ice. If you have a patient that has a deeper injury eg within the hamstring muscle belly, and has some fat overlying the area, it will require much longer application of ice to reduce tissue temperature, and you may not even be able to reduce the temperature of your targeted tissue at all. 20 minutes of ice application in this instance is unlikely to be enough.
Should we use padding or towels with ice application?
Padding is normally used to protect the skin from frostbite and ice injury. In the 35 studies that have applied ice directly to the skin, there have been no recorded skin injuries in clinical application. The only injuries have occurred are with application for 60 minutes at a time or if the patient has fallen asleep.
Before applying ice, as with all treatments, you need to check the patient does not have any contraindications or precautions to ice application eg allergy to cold.
If crushed ice is applied directly to the skin, it is not comfortable, but it is very effective. If it is applied over bandages or dry towels, icing is ineffective.
Check the skin for adverse or allergic reaction after the first minute, and every five minutes.
Contraindications and precautions to ice
Contraindications to ice therapy include:
- Active deep vein thrombosis or thrombophlebitis
- Areas near a chronic wound
- Cold hypersensitivity eg Raynaud’s, cryoglobulinema, hemoglobulinemia
- Cold urticaria (cold allergy or hypersensitivity)
- Impaired circulation
- Over regenerating nerves
- Tissues affected by tuberculosis
- Haemorrhaging tissue
- Untreated haemorrhagic disorders Areas with impaired circulation
Precautions to ice therapy include:
- People with cardiac failure
- People with hypertension
- Areas of impaired sensation that prevent people form giving accurate and timely feedback
- Infected tissues
- Damaged or at-risk skin