He was fatigued and he was under the influence of the poison. The cool air spread the poison all over his body and the son of Pandu (Bhima) became senseless.
शीतं वातं समासाद्य श्रान्तो मदविमोहितः। विषेण च परीताङ्गो निश्चेष्टः पाण्डुनन्दनः॥