ROSWELL, Ga. — It was 1 in the morning, and the orthopedic surgeon on call was preparing to operate on a woman whose foot had been shattered in a car wreck, after hours of tending to other patients. The woman’s husband, Jeff Anderson, asked him, “Are you too tired to do this?”

“He looked me straight in the eye — very quiet guy — and said, ‘I was born to do this,’” Mr. Anderson recalled.

The surgeon that night more than 20 years ago was Representative Tom Price of Georgia, President-elect Donald J. Trump’s nominee for secretary of health and human services, the cabinet official who will lead the new administration’s efforts to dismantle the Affordable Care Act.

Since then, the assuredness that defined Mr. Price as a surgeon has carried into his political career. He has always listened politely to other viewpoints but never swerved from his policy mission to protect his former profession from what he views as heavy-handed government intrusion.

Many who knew Mr. Price as a doctor here in Atlanta’s affluent northern suburbs praise his commitment to his patients. But his legislative record shows that over eight years in the Georgia Senate and 12 years in Congress, he has advocated at least as much for physician groups and health care companies — seeking to limit damages in malpractice cases, for instance, and voting against legislation that would have required the government to negotiate lower drug prices for Medicare beneficiaries.

Mr. Price has routinely argued that patients are the driving force behind his efforts. Still, his positions have often coincided with the financial interests of groups whose donations have helped advance his political career.

Doctors themselves are sharply divided over his nomination, and some are particularly galled by Mr. Price’s enmity for the Affordable Care Act and opposition to abortion rights. Some of his positions even clash with those of Mr. Trump, who wants to pressure pharmaceutical companies on drug prices, for example, and has pledged to largely leave Medicare alone.

If confirmed, Mr. Price, 62, will soon have far more power to influence the nation’s vast health care system than he ever did as a lawmaker. One of his first tasks would be to help Mr. Trump and Republicans in Congress determine how to eviscerate and replace the health law, a goal he has held since the law’s passage in 2010. But as leader of the agency that oversees Medicare, Medicaid, the Food and Drug Administration and the Centers for Disease Control and Prevention, Mr. Price would also hold considerable regulatory power, with the ability to influence everything from how applications to market new drugs are reviewed to how doctors are compensated for treating elderly and poor patients.

As Mr. Price prepares for two confirmation hearings — the first of which is scheduled for Wednesday — his past efforts on behalf of health-related companies, which have donated generously to his campaigns, are under scrutiny. So, too, is Mr. Price’s history of trading in biomedical, pharmaceutical and health insurance stocks while serving on the health subcommittee of the House Ways and Means Committee. Democrats have called for investigations into whether he traded stock based on information he gleaned as a congressman.

Last year, Mr. Price bought stock in a company that makes orthopedic implants shortly before introducing legislation that could have protected the company, Zimmer Biomet, from financial losses due to a new federal regulation. The regulation sought to rein in spending on joint replacements for Medicare patients; Mr. Price’s legislation would have delayed its implementation. After he introduced it, Zimmer’s political action committee contributed to his re-election campaign; the string of events was first reported Monday by CNN.

Phillip J. Blando, a spokesman for the Trump transition team, said Mr. Price “had no knowledge or input into the purchase” of the Zimmer stock, which he said was made by a broker. Asked why Mr. Price had not directed his broker to avoid buying health-related stocks while he wrote and voted on health legislation, Mr. Blando said, “We know that other members of Congress, including Democrats, have holdings in health care stocks and vote on health-related legislation.”

In a letter to an ethics lawyer at the Department of Health and Human Services last week Mr. Price said he would divest himself of holdings in 43 health-related and other stocks to avoid conflicts of interest. Noting that the Office of Government Ethics had completed an “exhaustive review” of Mr. Price’s financial holdings, Mr. Blando said last week that Mr. Price “takes his obligation to uphold the public trust very seriously.”

Although not among the billionaires whom Mr. Trump has tapped for his cabinet, Mr. Price has profited from medicine, both as a doctor and as an active investor in health care-related companies including Aetna, Bristol-Myers Squibb and Zimmer Biomet, which makes artificial joints and other medical devices. He has an estimated net worth of $13.6 million, according to the Center for Responsive Politics, with assets that include real estate. He has also been an effective fund-raiser: Even in his first run for office in 1996, his war chest of $173,000, much of which came from doctors and medical companies, led his poorly financed Democratic opponent to call him “Dr. Dollar.”

A brisk, hyper-focused workaholic who relishes the granular details of legislative proposals and process, Mr. Price expressed concern last year about Mr. Trump’s grasp of the issues. Taking questions from a student group at Emory University, he said he had voted for Marco Rubio in the Republican primary and called Mr. Trump an “empty policy vessel” who was “dangerous for politics and the economy,” according to the student newspaper.

Mr. Price, who declined to be interviewed, was engaged in a number of pitched partisan battles even before coming to Washington in 2005. In the Georgia Legislature, he voted against a new state flag that minimized the Confederate battle cross and supported a constitutional amendment banning same-sex marriage. In Congress, he has taken stances seen as antithetical to public health, opposing regulating tobacco as a drug and favoring legislation that would make it easier to sell bullets that can pierce armor.

He has also written a fairly detailed plan for replacing the Affordable Care Act. It would repeal the law’s expansion of Medicaid and provide tax credits to help with the cost of coverage based on age instead of income, with older people getting higher credits.

Mr. Price grew up in Dearborn, Mich., the son and grandson of doctors who heavily influenced his career choice. He has publicly recalled making house calls with his grandfather, who practiced medicine into his 90s. After medical school at the University of Michigan, he moved to Georgia, completing his residency at Emory and setting up practice in Roswell, a relatively affluent, conservative suburb of Atlanta.

In the 1990s, his practice, Compass Orthopedics, was among seven in the Atlanta area that merged into a large group that became known as Resurgens Orthopaedics. It became the largest orthopedic practice in Georgia, and now has 100 doctors and 1,000 employees spread over 21 locations.

Dr. Steven B. Wertheim, another founding partner of Resurgens, said one goal of the consolidation was to gain bargaining power with insurance companies and to provide M.R.I.s, physical therapy and even certain outpatient operations in-house rather than referring patients to other providers or operating at hospitals. More leverage with insurers often allows doctors to extract higher rates.

“His overall gist was, ‘Look, if all we did was practice good medicine, we’d be broke by tomorrow,’” Dr. Wertheim said of Mr. Price. “He understood the need to run a business.”

As a physician, Mr. Price was constantly frustrated by having to seek insurance companies’ approval for his patients to get an expensive diagnostic test or physical therapy — a common complaint among specialists. Similarly, he resented when federal health regulators intervened in something he and his partners thought they were already doing well, like using electronic medical records.

“Those are the things that drove him crazy,” Dr. Wertheim said.

His resentment of government intervention in medicine drove Mr. Price to become involved in the Medical Association of Georgia early in his career, and his work there led him to run for office in 1995, when the House seat in his district opened up. But by 2002, as his legislative duties increased, he traded his suburban practice for a job at Grady Memorial Hospital, a vast, chaotic, aging complex, just a few blocks from the State Capitol.

For the next two years, Mr. Price was the medical director of Grady’s orthopedic clinic, seeing a vastly different population than the well-off, privately insured patients he was used to. Most of Grady’s patients are poor and black, and many lack any form of insurance. Long waits for care are the norm, and trauma, including gunshot wounds, is a big part of the caseload.