Hubungan Indeks Massa Bebas Lemak Praoperasi dengan Skor Intake-Feeling Nauseated, Emesis, Exam, Duration (I-FEED) dan Lama Rawat Inap Pasien Pascalaparatomi Elektif Di RSUPN Dr Cipto Mangunkusumo = Association of Preoperative Fat-Free Mass Index with Intake-Feeling Nauseated, Emesis, Exam, Duration (I-FEED) Score and Postoperative Length of Hospital Stay in Elective Laparotomy Patients at Dr. Cipto Mangunkusumo Hospital