Franny Jongbloed

169 7 FEASIBILITY AND SAFETY OF A PREOPERATIVE DIET INTRODUCTION Reactive oxygen species (ROS) that the body produces during surgical procedures induce oxidative stress and lead to imbalances in homeostasis 1,2 . The subsequent stress response elicits hormonal, metabolic, and immunological changes that increase the risk of perioperative complications and may hamper postoperative recovery 1,3 . This risk is increased by pre-existing factors such as obesity 4 , and by perioperative factors such as ischemia-reperfusion injury (IRI) during organ transplantation 5,6 . Although treatments that decrease ROS production could reduce perioperative and postoperative complications, no effective clinical therapy is currently available. In animal studies, dietary restriction (DR) protects against ROS-induced damage. We demonstrated previously that short-term preoperative 30% DR protects against the oxidative damage induced by renal IRI in mice and improves postoperative survival and kidney function 7–9 , and similarly protects against liver IRI 10 . The beneficial effects of fasting on renal IRI are also observed in aged obese mice of both genders, suggesting that DR induces protection against ROS independent of age and gender 11 . Translating DR to humans in a clinical setting is difficult, because of the effort required by patients to voluntarily restrict their calorie intake. In addition, DR goes against the generally held beliefs that patients should be well fed before surgery to prevent malnutrition. Finally, the diet composition and duration that induce similar benefits in humans as observed in rodents is not known 12 . Studies examining the effects of a very low-calorie diet prior to bariatric surgery report contradictory effects on perioperative and postoperative outcomes, and adherence to the diet in these studies was not measured objectively 13,14 . In our previous pilot study in living kidney donors, we showed that three days of 30% DR followed by 24 h of fasting prior to kidney donation was feasible and safe, but had limited effects on outcome 15,16 . Subsequent results from murine experiments suggested that the beneficial effects were mainly due to restriction in protein intake 17 . The effect of protein restriction (PR) has not yet been investigated in a clinical setting. Therefore, our current pilot study investigated the feasibility of a preoperative diet combining DR and PR in two patient populations: living kidney donors and morbidly obese patients scheduled for laparoscopic donor nephrectomy or laparoscopic bariatric surgery, respectively. To identify objective markers of diet adherence, we measured both standard and experimental metabolic markers. Our results showed that short-term DR is feasible and represents a promising next step in investigating the effects of preoperative DR on surgery-related outcome in a clinical setting.