A Ukrainian surgeon had to operate using only his headlamp after blackouts caused by Russian missiles hit Lviv.
He said the time between the power outage and the generator turning on "could have cost the patient his life."
Russia continues to strike Ukraine's power grid, leaving a quarter of the city without power.
Dr. Oleh Duda was in the middle of a complicated and dangerous surgery when the lights in the operating room went out.
The cancer surgeon who works at a hospital in Lviv, Ukraine told the Associated Press that he heard explosions nearby when he was operating on a patient.
Moments after the noise, a blackout consumed the hospital, including the operating room where the patient was open on the table.
Duda couldn't stop what he was doing, the AP reported, leaving his only choice to carry on with the operation using only the headlamp on his head for light.
Fortunately, the AP reported, the hospital had a generator that kicked in three minutes later.
"These fateful minutes could have cost the patient his life," Duda told The Associated Press.
The blackout during the November 15 surgery was not confined to the hospital in Lviv. It was the result of another Russian missile strike on Ukraine's power grid, the AP reported. The strike damaged nearly half of the country's energy facilities.
Duda told the AP the explosions were so close to the hospital that "the walls were shaking." Doctors and patients had to take shelter in the hospital's basement, a routine that occurs every time the air raid siren sounds.
The strikes have continued since, with a November 23 strike leaving more in Ukraine without power, water, and public transportation, the AP reported.
According to the World Health Organization, a quarter of the people living in Ukraine - roughly 10 million people - were without power after the November 23 strike. Power and water have since been restored, according to the Kyiv Independent.
The healthcare system in Ukraine has taken a major hit because of the damage: surgeries are being postponed, patient records are unavailable due to internet outages, and paramedics are relying on flashlights to examine patients in their powerless apartments, according to the AP.
In the Lviv hospital, which mainly specializes in cancer, only 10 of the day's 40 scheduled surgeries were performed on November 15, the AP reported.
Just last week, surgeons at Kyiv's Heart Institute had to continue operating on a child's heart amid a blackout, according to a video posted to the organization's Facebook page.
"Rejoice, Russians, a child is on the table and during an operation the lights have gone completely off," Dr. Boris Todurov, director of the institute, said in the video, according to the AP. "We will now turn on the generator - unfortunately, it will take a few minutes."
The AP reported instances of broken medical machinery and generators in hospitals across Ukraine and stories of doctors and nurses carrying wounded patients to operating rooms when elevators are not working due to blackouts.
The World Health Organization said in a statement last week that "this winter will be life-threatening for millions of people in Ukraine" calling the upcoming season a "formidable test for the Ukrainian health system and the Ukrainian people."
"Ukraine's health system is facing its darkest days in the war so far," the WHO said. "Having endured more than 700 attacks, it is now also a victim of the energy crisis. It is being squeezed from all sides and the ultimate casualty is the patient."