Traditionally patients are “NPO after midnight” to reduce the risk of aspiration of gastric contents at induction of anesthesia. This results in a long period without hydration or nutrition, especially for cases booked later the following day. Oral intake of clear fluids up to 2 hours before surgery does not increase the risk of aspiration in healthy adults undergoing elective surgery (1) and may decrease anxiety, hunger and thirst while waiting for surgery (2). Anesthesia Society guidelines from multiple countries consistently recommended a 6 hour fast for solids and a 2 hour fast for clear fluids except in for patients with dysphagia, obstruction or gastroparesis.
For more information, see Chapter 4: Preoperative Fasting and Carbohydrate Treatment in The SAGES / ERAS® Society Manual of Enhanced Recovery Programs for Gastrointestinal Surgery
References:
1. Brady M, Kinn S, Stuart P. Preoperative fasting for adults to prevent perioperative complications. Cochrane Database Syst Rev. 2003;(4):CD004423.
2. Hausel J, Nygren J, Lagerkranser M, Hellström PM, Hammarqvist F, Almström C, Lindh A, Thorell A, Ljungqvist O. A carbohydrate-rich drink reduces preoperative discomfort in elective surgery patients. Anesth Analg. 2001 Nov;93(5):1344-50.