A patient was operated for right upper lobe resection. He was shifted to post awakening recovery after completion of surgery with vitals- BP 100/70 mm of Hg, HR - 94bpm, SPO2 100. After 2 hrs when he was assessed ,his vitals was BP 70/50 mm of Hg. HR-126 bpm ,SPO2 92 and surgical drain was filled with blood. Immediate re-exploration was planned. IV anaesthetic agent of choice -