RESUMO
Preoperative fasting is essential to prevent aspiration and associated complications. However, quite often patients end up fasting for 12 h or more due to changes in the operating room schedules, delays, and postponements. Preoperative fasting may lead to a fluid deficit, which may contribute to perioperative discomfort and morbidity. We report a case of 44-year-old female posted for total mastectomy with axillary clearance for carcinoma breast, with prolonged fasting where preoperative R wave amplitude variation along with associated changes in the plethysmograph was noticed on the monitor. 500 milliliters of lactated ringer solution was administered before induction of anesthesia, by the time R wave amplitude variation decreased. Variations in plethysmography became normal after 1 L of fluid administration after induction of anesthesia. Gross R wave amplitude variation is not a very common finding and may predict severe hypovolemia in preoperative area in prolonged fasting patients.