Introduction: A recent bariatric surgical study demonstrated an inverse relationship of intraoperative hydration with the incidence of extended hospital length of stay (ehLOS: >1 postoperative hospital day). In that study, a post hoc analysis of the preoperative duration of Nil Per Os (NPO) past midnight revealed a significant dose-response association on the incidence of ehLOS, with the lowest incidence (10-12 %) predicted within the 2-5-h NPO interval. As NPO is associated with a state of compensatory dehydration, the objectives of this study were to prospectively examine the role of decreasing preoperative NPO intervals on the incidence of ehLOS in a similar bariatric surgical population and to establish causality of this association.
Methods: Following IRB approval, 168 bariatric surgeries were analyzed following institution of a revised oral water ad libitum policy until 2 h prior to surgery on the incidence of ehLOS. The role of duration of NPO on the incidence of ehLOS was assessed by logistic fit graphs and misclassification rates on the two groups. A statistical process control chart monitored the efficacy of the revised NPO guidelines.
Results: There were statistically significant, but not clinical, differences in the incidences of histories of anemia, gastroesophageal reflux disease, previous percutaneous cardiac intervention/percutaneous transluminal coronary artery angioplasty, or preoperative albumin levels between the two groups. There were no perioperative pulmonary aspirations of gastric contents in either group. Following reduction of the oral hydration interval to ≥2 h, a 13-15 % incidence of ehLOS was observed within the 2-5-h NPO interval with similar misclassification rates observed between the two groups.
Conclusions: Allowing bariatric patients access to ad libitum water for up to 2 h prior to surgery decreased the incidence of ehLOS. Comparison of the dose-response curves within the 2-5-h NPO intervals before and after introduction of the revised NPO guidelines was similar and confirms causality.
Keywords: Adverse events, pulmonary aspiration; Bariatric surgery, laparoscopic; Causality; Hospital length of stay; Hydration, oral; Statistical process control charts.