the WaPo quotes an 'aide' (medical?) who was reportedly present:
http://voices.washingtonpost.com/checkpoint-washington/2010/12/holbrookes_final_words_on_the.html____ As Dr. Jehan El-Bayoumi was attending to Mr. Holbrooke in the emergency room at George Washington University Hospital, she told him to relax and asked what she could do to comfort him, according to an aide who was present. Holbrooke, who was in severe pain, said jokingly that it was hard to relax because he had to worry about the difficult situation in Afghanistan and Pakistan.
El-Bayoumi, an Egyptian-American internist who is Secretary of State Hillary Rodham Clinton's physician, replied that she would worry for him. Holbrooke responded by telling her to end the war, the aide said.
The aide said he could not be sure of Holbrooke's exact words. He emphasized Tuesday that the comment was made in painful banter, rather than as a serious exhortation about policy. Holbrooke also spoke extensively about his family and friends as he awaited surgery by Farzad Najam, a thoracic surgeon of Pakistani descent.
read:
http://voices.washingtonpost.com/checkpoint-washington/2010/12/holbrookes_final_words_on_the.html