Evaluation of two different fluids regimens on central venous-to-arterial Carbon Dioxide difference (pCO gap) - a randomized controlled trial

Purpose
The purpose of this study was to evaluate whether crystalloid or colloid solutions could adequately optimize the patient cardiac output and thus improving systemic and microcirculatory blood flow during major orthopedic surgery.
Methods
Eighty-two (ASA) I–III patients were included in this prospective single-center randomized, controlled clinical trial. They were randomized into groups treated with either intra-operative crystalloid (lactated ringer) or colloid (6% hydroxyethyl starch, HES 130/0.4). Demographic data, Hemodynamic variables, pC gap, central venous oxygen saturation and lactate levels were recorded every hour during surgery and until discharge from the Post-Anesthesia Care Unit (PACU). Infused volumes of crystalloids and HES, number of infused PRBCS and estimated intraoperative blood loss were recorded blindly for all patients.
Results
pCO gap was significantly lower in colloid group than crystalloid group toward the end of surgery and at PACU admission with values less than 5 mmHg while pCO gap was >5 mmHg at 5 hr and at PACU in the crystalloid group. In crystalloid vs colloid group, pCO gap was 4.97 vs 4.52 (P 0.023), 5.09 vs 4.057 (0.011) and 5.27 vs 4.88 (0.011) at 4 hr, 5 hr and at PACU respectively. At 5 hr patients received colloid had significantly lower mean pCO gap by 0.517 mmHg, average pCO gap among patients receiving crystalloid therapy was 5.09 mmHg and 4.57 mmHg in patients with colloids therapy.
Conclusion
Intraoperative fluid resuscitation using colloids is associated with more stable hemodynamics and better tissue perfusion as guided by lower pCO gap when compared to crystalloids.