The week before Brian Colvin was scheduled for shoulder surgery in November, he tested positive for COVID-19. What he thought at first was a head cold had morphed into shortness of breath and chest congestion coupled with profound fatigue and loss of balance.

Now, seven months have passed and Colvin, 44, is still waiting to feel well enough for surgery. His surgeon is concerned about risking anesthesia with his ongoing respiratory problems, while Colvin worries he’ll lose his balance and fall on his shoulder before it heals.

“When I last spoke with the surgeon, he said to let him know when I’m ready,” Colvin said. “But with all the symptoms, I’ve never felt ready for surgery.”

As the number of people who have had COVID-19 grows, medical experts are trying to determine when it’s safe for them to have elective surgery. In addition to concerns about respiratory complications from anesthesia, COVID-19 may affect multiple organs and systems, and clinicians are still learning the implications for surgery. A recent study compared the mortality rate in the 30 days following surgery in patients who had a COVID-19 infection and in those who did not.

It found that waiting to undergo surgery for at least seven weeks after a COVID-19 infection reduced the risk of death to that of people who hadn’t been infected in the first place. Patients with lingering symptoms should wait even longer, the study suggested.

But, as Colvin’s experience illustrates, such guideposts may be of limited use with a virus whose effect on individual patients is so unpredictable.

“We know that COVID has lingering effects even in people who had relatively mild disease,” said Dr. Don Goldmann, a professor at Harvard Medical School who is a senior fellow and chief scientific officer emeritus at the Institute for Healthcare Improvement. “We don’t know why that is. But it’s reasonable to assume, when we decide how long we should wait before performing elective surgery, that someone’s respiratory or other systems may still be affected.”

The study, published in the journal Anaesthesia in March, examined the 30-day postoperative mortality rate of more than 140,000 patients in 116 countries who had elective or emergency surgery in October. Researchers found that patients who had surgery within two weeks of their COVID-19 diagnosis had a 4.1% adjusted mortality rate at 30 days; the rate decreased to 3.9% in those diagnosed three to four weeks before surgery, and dropped again, to 3.6%, in those who had surgery five to six weeks after their diagnosis.

Patients whose surgery occurred at least seven weeks after their COVID-19 diagnosis had a mortality rate of 1.5% 30 days after surgery, the same as for patients who were never diagnosed with the virus.

Even after seven weeks, however, patients who still had COVID-19 symptoms were more than twice as likely to die after surgery than people whose symptoms had resolved or who never had symptoms.

Some experts said seven weeks is too arbitrary a threshold for scheduling surgery for patients who have had COVID-19. In addition to patients’ recovery status from the virus, the calculus will be different for an older patient with chronic conditions who needs major heart surgery, for example, than for a generally healthy person in their 20s who needs a straightforward hernia repair.

“COVID is just one of the things to be taken into account,” said Dr. Kenneth Sharp, a member of the Board of Regents of the American College of Surgeons and vice chair of the Department of Surgery at Vanderbilt University Medical Center.

In December, the American Society of Anesthesiologists and the Anesthesia Patient Safety Foundation issued these guidelines for timing surgery for former COVID-19 patients:

• Four weeks if a patient was asymptomatic or had mild, nonrespiratory symptoms.

• Six weeks for a symptomatic patient who wasn’t hospitalized.

• Eight to 10 weeks for a symptomatic patient who has diabetes, is immunocompromised or was hospitalized.

• Twelve weeks for a patient who spent time in an intensive care unit.

Those guidelines are not definitive, according to the groups. The operation to be performed, patients’ medical conditions and the risk of delaying surgery should all be factored in.

“Long COVID” patients like Colvin who continue to have debilitating symptoms months after 12 weeks have passed require a more thorough evaluation before surgery, said Dr. Beverly Philip, president of the society.

Now that COVID has been brought to heel in many areas and vaccines are widely available, hospital operating rooms are bustling again.

At the beginning of the pandemic, surgical volumes dropped dramatically as many hospitals canceled nonessential procedures and patients avoided facilities packed with COVID-19 patients.

From March to June 2020, the number of inpatient and outpatient surgeries at U.S. hospitals was 30% lower than in the same period the year before, according to McKinsey & Company’s quarterly Health System Volumes Survey. By May 2021, surgical volumes had mostly rebounded, and were just 2% lower than their May 2019 totals, according to the May survey.

For Brian Colvin, whose right rotator cuff is torn, delaying surgery is painful and may worsen the tear. But the rest of his life is on hold, too. A sales representative for an auto parts company, he hasn’t been able to work since he got sick.