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If you get frequent migraines, have a sore lower back or suffer from arthritis or fibromyalgia you are more at risk of developing persistent pain after major surgery, experts say.

Patients with chronic pain should meet with the anesthesiologist before the procedure to discuss pre-emptive pain-control measures, says John Penning, medical director of the acute pain service for The Ottawa Hospital.

Surgeons can use a local anesthetic as well as a general one, and patients can take anti-inflammatory drugs and different kinds of pain medication before their procedure. Nerve blocks, which involve using an anesthetic to numb nerves, are also an option. So is spinal anesthesia, similar to the epidurals many women get during labour. "The fact that the patient is already in chronic pain raises the possibility that they may be more sensitive," Dr. Penning says.

In the past decade, scientists have compiled evidence that chronic pain is a disease on its own, one that involves a rewiring of the central nervous system and that can be triggered when the acute pain that comes with an injury or surgery is not adequately treated.

The theory behind using a local anesthetic or nerve blocks in addition to a general anesthetic is that they prevent the transmission of a barrage of pain signals from the part of the body a surgeon is cutting or rebuilding, and protect the central nervous system from damage.

There is evidence patients with chronic pain need the extra help, even if the operation involves areas that were previously pain-free. A study published in 2007 in the journal Anesthesiology found that women who had pain elsewhere in their bodies were more likely to develop chronic pelvic pain after a hysterectomy.

It also found that a spinal anesthetic offered some protection from post-surgical chronic pain.

Dr. Penning says doctors should screen patients before surgery to identify those with chronic pain. In the meantime, he says, patients should ask to see an anesthesiologist before major surgery, including joint replacement, shoulder repair and spinal or abdominal operations.

Barbara Fanning, 54, of Oakville, Ont., has lived with back pain since she lifted an air tank after a beach dive in the British Virgin Islands 20 years ago. She has had a couple of abdominal operations since then, and asked for nerve blocks before getting a general anesthetic.

"It made a difference," she says.

But all patients - not only those living with chronic pain - can benefit from measures to reduce pain during surgery, says Brian Kashin, medical director of the acute pain service at North York General Hospital. Alleviating pain reduces the risk that someone will go on to develop chronic pain, he says.

Using a local and a general anesthetic as well as other pain-reduction strategies is routine in some hospitals but not in others, Dr. Kashin says. So it is a good idea for patients to ask about their options.

For years, clinical trials assessing the value of pre-emptive pain treatment produced conflicting results, with some studies showing it was beneficial and others showing it wasn't.

It is challenging to devise good experiments that account for all the variables, says Dr. Kashin, who is also a lecturer in the department of anesthesiology at the University of Toronto.

Those variables include an individual's pain tolerance and susceptibility, Dr. Penning says.

Six million Canadians are living in pain, according to the PainExplained.ca campaign launched this week as part of National Pain Awareness Week.

They face a number of barriers in getting effective medical care, the Canadian Pain Society says. Many doctors and nurses don't receive adequate training in treating pain and patients can have difficulty finding a doctor willing to help them.