• mixed venous oxygen saturation, acid bases, hemodynamics [ Time Frame: intraoperative period ] [ Designated as safety issue: No ]
  

• Wound infection and length of hospital stay [ Time Frame: during the hospital admission ] [ Designated as safety issue: No ]
  

This is a randomized, prospective controlled trial in patients (ASA I-III) undergoing open abdominal surgical procedures in a single center. This study will be done in two phases. The first phase is designed to evaluate and prove the safety of restricted fluid regimens in maintaining tissue perfusion using a central venous oximetric catheter and arterial blood gas analysis. In the second phase of the study, we plan to mimic the usual clinical practice without the central venous oximetric catheter and arterial lines (invasive monitors) and the postoperative total morbidity will be compared between the liberal and restricted fluid regimens.

In the first phase of the study, 90 patients coming in for open bowel surgery will be randomized to three groups using a random number generator. All patients will receive a standard bowel prep regimen (Go-Lyte-half a liter the night before surgery). Group A will receive current standard of care (liberal fluid therapy), Group B and C will receive restricted fluid regimens. All patients will receive 500 cc of intravenous fluids (lactated ringers in Group A and B, 6% hetastarch in Group C) in the preoperative holding area to correct preoperative fluid deficits due to fasting and bowel preparation. Patients younger than 18 years, ASA IV or V, pregnant patients, those with coagulopathy, renal insufficiency, unstable angina, unstable congestive heart failure, and those with contraindication to central venous pressure catheter insertion will be excluded from the study.

After instituting anesthesia monitors, patients will be anesthetized with a standard anesthetic regimen. An arterial line and a central venous catheter with oximetric capability will be inserted in all three groups. A baseline blood gas will be drawn to note the base excess, lactate levels and the hematocrit at the start of surgery. Parameters like heart rate, blood pressure, central venous pressure, mixed venous oxygen saturation and arterial oxygen saturation and urine output will be continuously monitored. Both the regimens will be started in the operating room and continued into the postoperative period until they resume their oral intake. Patients in the liberal group will receive (10ml/kg/hr) the current standard of care for bowel surgery whereas those in the restricted group will receive 4ml/kg/hour. Post induction hemodynamic instability will be treated with ephedrine and phenylephrine at the discretion of the anesthesiologist in charge.

Intraoperative treatment of tachycardia, hypotension in both the groups will be treated using a standard fluid regimen algorithm (appendix A). All patients will receive the same postoperative fluid regimens as the current standard of care. Postoperative morbidity evaluation (appendix B) will be done at patient's discharge from the hospital. The data entry will be prospectively done during their hospital stay. The accuracy of the data will be checked by one of the study investigators.