Writing on his website, O'Brien said that the amputation was the result of a simple injury: a case with television equipment fell on his arm. But that incident caused what doctors later told him was "Acute Compartment Syndrome", a condition that cuts off the flow of blood to a limb and can be life-threatening.
Then, things took a turn for the worse:
The doctor recommended an emergency fasciotomy to relieve the pressure. This is a gruesome enough procedure on its own, but the he was clear that the problem was progressing rapidly and there was a clear and present threat to my limb.
It was getting real. Of course I wasn’t awake for the action but I was told later that things tanked even further once I was on the table. And 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. He later told me it all boiled down to a choice…between a life and a limb.
O'Brien is currently a science correspondent for "PBS Newshour." He worked at CNN for decades, with stints as the network's science reporter and as a host of its morning show, "American Morning."
Read his full piece here.