Safety and efficacy of oral rehydration therapy until 2 h before surgery: a multicenter randomized controlled trial

J Anesth. 2012 Feb;26(1):20-7. doi: 10.1007/s00540-011-1261-x. Epub 2011 Nov 1.


Purpose: In many countries, patients are generally allowed to have clear fluids until 2-3 h before surgery. In Japan, long preoperative fasting is still common practice. To shorten the preoperative fasting period in Japan, we tested the safety and efficacy of oral rehydration therapy until 2 h before surgery.

Methods: Three hundred low-risk patients scheduled for morning surgery in six university-affiliated hospitals were randomly assigned to an oral rehydration solution (ORS) group or to a fasting group. Patients in the ORS group consumed up to 1,000 ml of ORS containing balanced glucose and electrolytes: 500 ml between 2100 the night before surgery and the time they woke up the next morning and 500 ml during the morning of surgery until 2 h before surgery. Patients in the fasting group started fasting at 2100 the night before surgery. Primary endpoints were gastric fluid volume and pH immediately after anesthesia induction. Several physiological measures of hydration and electrolytes including the fractional excretion of sodium (FENa) and the fractional excretion of urea nitrogen (FEUN) were also evaluated.

Results: Mean (SD) gastric fluid volume immediately after anesthesia induction was 15.1 (14.0) ml in the ORS group and 17.5 (23.2) ml in the fasting group (P = 0.30). The mean difference between the ORS group and fasting group was -2.5 ml. The 95% confidence interval ranged from -7.1 to +2.2 ml and did not include the noninferior limit of +8 ml. Mean (SD) gastric fluid pH was 2.1 (1.9) in the ORS group and 2.2 (2.0) in the fasting group (P = 0.59). In the ORS group, mean FENa and FEUN immediately after anesthesia induction were both significantly greater than those in the fasting group (P < 0.001 for both variables). The ORS group reported they had been less thirsty and hungry before surgery (P < 0.001, 0.01).

Conclusions: Oral rehydration therapy until 2 h before surgery is safe and feasible in the low-risk Japanese surgical population. Physicians are encouraged to use this practice to maintain the amount of water in the body and electrolytes and to improve the patient's comfort.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Fasting
  • Female
  • Fluid Therapy / adverse effects*
  • Gastric Acidity Determination
  • Humans
  • Male
  • Middle Aged
  • Preoperative Care*
  • Sodium / metabolism
  • Time Factors
  • Urea / metabolism


  • Urea
  • Sodium