Nerve cooler that makes op recovery less painful

COOLING skin with an ice cube for two minutes beforehand eases the pain of a local anaesthetic injection, a study shows.

Researchers at Isfahan University of Medical Sciences in Iran recruited 108 A&E patients needing local anaesthetic for treatment to cuts on their arms.

Half had an ice cube held against their skin first, while the rest did not.

Results in the Archives of Academic Emergency Medicine showed that pain scores in the ice-cube patients were roughly half those registered in the non-ice group, due to numbing of nerves that transmit pain signals to the brain.

ATINY implant that cools down nerves inside the body could banish pain after surgery. The device is placed near the site of the operation at the end of a procedure, where it cools the nerves from around the normal body temperature of 37c down to 10c.

The idea is that this stops them sending pain signals to the brain, in much the same way as applying ice to an injury can numb the discomfort.

After a few weeks, when the patient has recovered and pain relief is no longer required, the implant — which looks like a long strip of soft plastic around 5 mm long and no thicker than a piece of paper — simply dissolves harmlessly inside the body and is expelled as waste.

Scientists from Northwestern University in the U.S. — who developed the implant — predict it will help to reduce the use of powerful and potentially addictive opioid painkillers by patients who are recovering from major surgery, such as back operations.

These medicines, including morphine, oxycodone and tramadol, are very effective at easing acute pain and are very commonly prescribed after major operations or medical procedures.

But if they are taken for more than a few weeks, there is a chance the patient can become dependent on them, as the drugs trigger the release of endorphins — the brain’s feel-good chemicals.

Some studies suggest up to 53 per cent of opioids dished out in the UK for chronic pain (lasting longer than 12 weeks) are unnecessary, as patients are unlikely to get better on them and could become addicted.

When the implant is inserted at the surgical site, one end is wrapped around the nearby nerves that would carry the pain signals to the brain.

The other end of the strip protrudes slightly through the surgical wound and is connected to a small hand-held pump, which the patient would use to adjust the level of pain relief.

At the push of a button on the pump, a coolant liquid called perfluoropentane is pumped through a tiny channel that runs from the pump end of the strip to the other end, to where it is wrapped around the nerves.

Through a second channel running parallel to the first, a gas called dry nitrogen is pumped the same way.

When the two meet in a chamber at the nerve end of the strip, a reaction occurs that causes the coolant to evaporate.

As it does, it chills the nerve down to as far as 10c. Cooling nerves in this way disrupts the transmission of pain messages to the brain.

As the implant eventually breaks down, the coolant is flushed out of the body without causing any harmful or lasting effects.

So far, the implant has only been tested in mice. But the results, published earlier this month in the journal Science, suggested it significantly reduced signs of pain when the mice were exposed to a slight injury in their paws, compared with when the cooling implant was not used.

Scientists plan to test the device for a range of pain-related conditions, not just post-surgical pain, in further animal studies before attempting trials in humans.

Dr Michael Platt, a retired consultant in pain medicine for St Mary’s Hospital, London, said the implant was ‘a really good idea’.

He added: ‘It’s potentially very exciting because although it chills the nerve, it doesn’t destroy it like some other forms of cooling pain relief do — such as cryotherapy (which uses liquid nitrogen to freeze nerves).’