During an enterectomy, especially in an open surgery, large amounts of fluid are administered in consideration of the patient's fasted state, maintaining blood pressure during surgery and potential third space loss. However, it has recently been reported that excessive fluid administration during surgery is actually detrimental to patients' prognoses. In fact, several reports have suggested that compared to limited fluid administration, excessive fluid administration increased the length of stay or the chances of complications. Thus, goal-directed fluid optimization is required during surgery because only a proper amount of fluid (neither limited nor excessive) administration can minimize postoperative complications and enhance prognosis. In general, the amount of fluid administered is determined with regard to the patient's volume status, including a comprehensive assessment of vital signs such as the pulse rate and blood pressure, and urine volume. However, this method has limitations in that it is an inadequate indicator of the actual intravascular volume of a patient to determine and administer the proper amount of fluid. Recently, new methods of measuring volume status that are less invasive and more accurate have been introduced. These methods include stroke volume variation (SVV) that monitors changes in arterial pressure waveform amplitudes with regard to breathing patterns. This is an effective method of monitoring fluid responsiveness after placing a catheter via a radial artery puncture. The stroke output is dependent on the preload, afterload, and cardiac contractility. The cardiac output is determined by multiplying the stroke output and heart rate. SVV indicates the difference in stroke output within one breathing cycle. A direct or indirect measurement of stroke output is required, which can be performed by analyzing arterial pressure waveforms via a FloTrac Sensor (Edwards Lifesciences, USA) monitor. SVV is known to have a high fluid responsiveness even during open surgeries, yet there is practically no research data on its effect in patients' postoperative recovery and prognosis in comparison to the traditional methods of fluid administration. Therefore, the investigators will apply SVV via a FloTrac/ Vigileo™ monitor on patients undergoing bowel resection to determine whether it better assists proper fluid administration compared to the traditional method of fluid administration by examining the patients' postoperative prognosis such as bowel movement recovery and length of stay.

Inclusion Criteria:

• Patients aged 20 to 70 scheduled to undergo bowel resection open surgery below the ASA class 3

Exclusion Criteria:

• Patients with significant impairments in heart, kidney, and liver functions
• Patients with arrhythmia such as tachycardia and atrial fibrillation or patients on pacemakers
• Patients diagnosed with peripheral arterial disease or are Allen's test positive
• Patients who underwent surgery on the identical surgical area
• Patients with obesity
• Patients with blood coagulation impairments