In a blog post on his personal website Tuesday, which was verified by PBS, O'Brien recounted the Feb. 12 blow to his arm he suffered while on assignment in Asia and the medical emergency that followed.
He was diagnosed with "acute compartment syndrome," O'Brien said, in which blocked blood flow in an enclosed space in the body can cause life-threatening consequences.
Part of his arm was removed in a choice between "a life and a limb," O'Brien said, quoting his doctor. He is grateful to be alive, the PBS reporter said.
O'Brien has continued working despite the ordeal, PBS spokeswoman Anne Bell said.
The former CNN science and space correspondent covers science for "PBS NewsHour" and is a correspondent for public TV's documentary series "Frontline" and the National Science Foundation's Science Nation online magazine.
According to his blog, O'Brien was securing cases filled with camera gear on a cart as he wrapped up a reporting trip to Japan and the Philippines. One of the cases fell onto his left forearm, he wrote, adding, "It hurt, but I wasn't all '911' about it."
The arm was sore and swollen the next day but worsened on the next, Feb. 14, and he sought medical care. O'Brien did not detail where he was and PBS couldn't immediately provide the information.
At the hospital, as his pain increased and arm numbness set in, a doctor recommended an emergency procedure to relive the pressure within the limb, O'Brien wrote.
"When I lost blood pressure during the surgery due to the complications of compartment syndrome, the doctor made a real-time call and amputated my arm just above the elbow," O'Brien wrote.
He typed the blog post with one hand and help from speech recognition software, he noted, and ended it with dark humor.
"Life is all about playing the hand that is dealt you. Actually, I would love somebody to deal me another hand right about now - in more ways than one," O'Brien wrote.
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