A Prospective Randomized Pilot Study of Near-Infrared Spectroscopy-Directed Restricted Fluid Therapy versus Standard Fluid Therapy in Patients Undergoing Elective Colorectal Surgery

Abstract

There are substantial data supporting the concept that algorithms that effectively limit fluid volumes to patients undergoing elective surgery, particularly intraoperatively, significantly reduce perioperative morbidity. We hypothesized that intraoperative fluid limitation could be safely accomplished when guided by near-infrared spectroscopy (NIRS) monitoring, and that this fluid restriction regimen would result in a reduction in postoperative morbidity when compared with standard monitoring and fluid therapy. The intent of this pilot study was to demonstrate the feasibility and ease of conduct of this study protocol before expanding to the multicenter pivotal trial. We performed a prospective, (2:1) randomized, pilot study at two centers. A total enrollment of 24 fully evaluable patients undergoing elective open colorectal surgery (16 restricted, 8 standard) was planned. After providing informed consent, patients were randomized to standard fluid resuscitation (500 LR induction bolus, then LR 7 mL/kg/h X 1 h, then 5 mL/kg/h) or restricted fluid resuscitation (no induction bolus, then LR 2 mL/kg/h). Subsequent fluid bolus infusions were guided by physiologic parameters (systolic blood pressure < 90 mm Hg, heart rate > 100 bpm, or oliguria) in the standard group, and by tissue oxygen saturation from NIRS (tissue oxygen saturation (StO₂) < 75%, or 20% below baseline; or the same physiologic parameters) in the restricted group. Primary endpoints were major postoperative complications. A total of 27 patients were randomized (18 restricted, 9 standard). Age, gender, ethnicity, past medical history, and body mass index were similar. American Society of Anesthesiologists class was somewhat higher in the restricted group (American Society of Anesthesiologists class 3 in 77% of restricted vs 44% of standard patients; P = 0.194). Median total intraoperative fluids were less in the restricted group (1300 mL) when compared with the standard group (3014 mL) (P = 0.021). Total fluids for the hospitalization were also statistically significantly decreased in the restricted group. Complications occurred in about two-thirds of patients, and complication rates were not statistically different between groups (1.6/restricted patient vs 2.1/standard patient; P = 0.333). Primary indications for boluses (n = 93) given to study patients were: hypotension (69%); oliguria (15%); and tachycardia (14%), with multiple indications per bolus. In only two instances did the StO₂ drop to less than 75 per cent, or decrease by 20 per cent from baseline in the 3 minutes before bolus as an indication for fluid administration. Patients undergoing elective colorectal surgery with a fluid restricted strategy had only rare episodes of decreased StO₂, suggesting that adequate tissue perfusion was maintained in this group. As a result, NIRS monitoring did not significantly influence intraoperative fluid management of patients undergoing colorectal surgery.