Nerve blocks can cut opioid use after cardiac surgery

HN Summary

• A St. Michael’s Hospital-led clinical trial found that continuous nerve blocks significantly reduced opioid use after open-heart surgery.

• Patients receiving the nerve blocks required fewer opioids and were less likely to need high doses during recovery.

• The findings could help make opioid-sparing pain management a standard part of cardiac surgery worldwide.

A clinical trial led by St. Michael’s Hospital researchers found that using nerve blocks, an anesthesia technique to numb targeted areas of the body, significantly reduced opioid use after cardiac surgery – findings the authors say could reshape how the potentially addictive drugs are used after open-heart surgery.

EPOCH-CardioLink-10, a large randomized controlled trial on opioid sparing approach in cardiac surgery, was led by St. Michael’s and conducted at hospitals across four Canadian provinces. The trial enrolled 318 adults undergoing cardiac surgery between 2023 and 2025. All patients had a median sternotomy, that involves splitting the breastbone which is later wired closed to heal. Participants were randomly assigned to receive continuous nerve blocks delivering either a local anaesthetic, ropivacaine, or a placebo for two days after surgery.

Their findings, published earlier this month in The Lancet Regional Health-Americas, showed that within the first 72 hours – a key window for recovery – on average, patients who received the anesthetic used 20.7 fewer morphine milligram equivalents (MME) – a standard measure of opioid use. They were also nearly half as likely to need very high doses of opioids: 12.9 per cent required at least 200 MME, compared with 23 per cent of patients who received the placebo.

The challenge of cutting opioids in cardiac surgeries

Cardiac surgery has been slower than other specialties to move away from using opioids for pain management because of the intensity of the procedures.

For example, with coronary artery bypass surgery, commonly known as a heart bypass, significant pain is caused by a median sternotomy for the heart to be laid bare for surgeons to create new paths for the blood to reach the heart muscle. 

“Modern day cardiac surgery was originally made possible with the use of high-dose morphine based anesthesia that provided stable heart function and blood pressure and allowed surgeons to do the kinds of surgery they needed to do,” says Dr. Mazer.  

Part of the reason cardiac surgeries have lagged in opioid-sparing approaches is also technical. The anesthetic gases that keep patients unconscious can lower blood pressure significantly. To keep blood pressure and heart rate steady during surgery, cardiac surgery teams have relied less on those gases and more on opioids and other drugs. Since it is hard to avoid opioid use during the operation itself, the St. Michael’s team set out to reduce them sharply afterward, for postoperative pain, proving that nerve blocks can reshape post-operative pain management.

To cut opioid use in the recovery window, the team adapted a technique from pediatric medicine. In standard practice, some nerve blocks are placed in a patient’s back while they are sitting up, which is not feasible for cardiac surgery. The parasternal approach the team borrowed can be done with the patient lying down after the chest is closed, delivering anesthetic beside the breastbone to block the nerves that carry pain signals from that area. Rather than administering a single injection that wears off within hours, thin catheters were threaded into each side of the chest and local anesthetic was run continuously for two days, much like an epidural during childbirth.

The human cost of opioids

Amid a global opioid crisis, the drugs that enable life-saving cardiac surgeries are now a growing cause for concern, driven by both illegal and prescription opioid use.

Last year, an average of 16 people lost their lives each day in the country due to opioid toxicity, according to the Public Health Agency of Canada. While comprehensive Canadian data on the link between cardiac surgery and opioid addiction doesn’t exist, a study conducted in the United States found that one in ten patients can develop persistent opioid use after cardiac surgery. 

For surgical patients, the risks come in two forms. In the days after surgery, opioids bring side effects that cardiac surgery teams have long accepted as part of recovery – drowsiness, nausea, vomiting, and delirium in older patients. The longer-term concern is dependence, and the path to it may begin in those first days.

“If you can control pain well at the time of surgery, whether it’s cardiac or orthopedic surgery, the risk of developing a chronic pain situation is reduced,” says Dr. Mazer. He is careful to note that EPOCH CardioLink-10 was not designed to test that idea directly, but it points to why controlling pain in the critical early window, with less reliance on opioids, could matter well beyond the hospital stay.

“We often see patients who started opioids after a major surgery or trauma, and years later, they’re still relying on them to manage chronic pain,” says Dr. Alli. “What begins as appropriate pain treatment can evolve into long-term use that’s very challenging to reverse.”

A surprisingly smooth recovery

Ernest Koehl, age 75, learned of the EPOCH CardioLink-10 clinical trial during a pre-operative meeting for his scheduled coronary bypass, when the anesthesiologist mentioned it in passing. His wife, who had had a nerve block for her ankle surgery, was a strong proponent and encouraged Koehl to sign up.

This was Koehl’s first major operation, and his expectations were shaped by what others had told him. He says, “We’ve known people who have gone through open heart surgery, and all they wanted to do was die the first day after, because the pain was so intense.”

His own experience was vastly different. “My recovery was amazing. When I woke up from surgery, I didn’t have the massive pain I was anticipating,” Koehl says.

Koehl woke lucid and alert. When a resident came by to check his mental facilities, he answered so sharply the doctor joked, calling him a show-off.

Koehl received only 15 per cent of the average opioid dose required for pain management following the procedure, “When I was discharged, all I went home with was extra-strength Tylenol. That was it.”

“From my perspective, the nerve block is a game changer,” he says. “If you can give people this pain relief after surgery, the recovery is huge.”

Zehra Goawala works in communications at Unity Health.

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