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We have studied the effect of ingestion of unlimited clear fluids by adolescents up to 3 h before anaesthesia to determine the effect this fluid ingestion would have on thirst, hunger and gastric contents at induction of anaesthesia. We studied prospectively 152 adolescents (ages 13-19 yr) undergoing elective surgery. Fifty percent of the patients had nothing by mouth after midnight. The other 50% were instructed to ingest unlimited clear fluids up to 3 h before surgery. On arrival in the operating room, subjects were asked to assess thirst and hunger with a linear analogue scale of 0-10 (0 corresponding to no thirst or no hunger). After induction of anaesthesia, gastric contents were aspirated via a 16-French gauge orogastric tube. Gastric fluid volume (GV) was measured with a syringe and gastric pH (GpH) was assessed with Merck pH strips. GV, GpH and subject hunger were unaffected by ingestion of clear fluids. Subject thirst was reduced by clear fluids. It is concluded that unlimited clear fluid ingestion by healthy adolescents up to 3 h before operation decreases thirst and does not affect gastric contents.

To determine the effect on gastric contents of unlimited clear fluid ingestion by children up to two and a half hours and then up to two hours before elective surgery, 228 healthy children (ages two to twelve years) were prospectively studied. During Phase I of this study subjects ingested unrestricted volumes and types of clear fluids up to three hours (control group) or two and a half hours before surgery. After establishment of adequate anaesthesia, gastric fluids were aspirated via an orogastric tube. Gastric volume was measured with a syringe and gastric pH was determined. After determining that there was no adverse effect associated with reducing a clear fluid fast to two and a half hours, Phase II of the study was begun. The methods for Phase II were unchanged except that unlimited clear fluids were permitted up to three hours (control group) or two hours preoperatively. In both Phase I and II, gastric volume and gastric pH were unaffected by reducing the fast to less than three hours. It is concluded that ingestion of unlimited clear fluids up to two hours before elective surgery does not affect gastric contents of healthy children.

This prospective, randomized, single-blind study of 121 healthy children aged 2 to 12 yr investigated the effect of clear fluids on gastric contents. Gastric fluid volume and pH were measured immediately following the induction of general anaesthesia and were not significantly affected by the ingestion of unlimited clear fluids up to three hours preoperatively. After a prolonged fast (mean fast 14 hr), gastric fluid volume was 0.39 +/- 0.37 ml.kg-1 and gastric pH was 1.7 +/- 0.4; after unlimited clear fluids (203 +/- 109 ml) up to three hours before surgery gastric fluid volume was 0.34 +/- 0.28 ml.kg-1 and gastric pH was 1.8 +/- 0.7 (mean +/- SD). Gastric fluid volume (ml.kg-1) increased in both the control and study groups as age increased, P less than 0.005. It is concluded that drinking clear fluid up to three hours before scheduled surgery does not have a measurable effect on gastric volume and pH of healthy children of ages 2 to 12 yr.