Effects of an Augmented Postoperative Fluid Protocol on Wound Healing in Cardiac Surgery Patients

• Background Cardiac surgery patients are vulnerable to hypoperfusion postoperatively and often have subcutaneous tissue oxygen tension less than 50 mm Hg. Hypovolemia most likely contributes to this hypoperfusion and may lead to impaired wound healing. • Objective To determine if a modified postoperative fluid replacement protocol would result in improved tissue oxygen tension, blood flow, and healing in cardiothoracic surgery patients. • Methods A total of 166 cardiac surgery patients, 18 to 90 years old, participated in a randomized, 2-group, repeated-measures study. The experimental group received fluid augmentation during the first 36 hours after surgery; the control group received standard postoperative replacement fluids. Subcutaneous tissue oxygen tension and temperature were measured 8, 18, and 36 hours after surgery. Tissue cellularity and accumulation of hydroxyproline were evaluated in tissue obtained from subcutaneous expanded polytetrafluoroethylene tubes. Wound complications were evaluated by using the ASEPSIS Wound Scoring System. • Results Tissue oxygen levels, tissue cellularity, and accumulation of hydroxyproline were similar in the 2 groups. A negative correlation (P = .01) existed between higher tissue oxygen values and lower (better) ASEPSIS leg wound scores. More than 80% of the patients had tissue oxygen levels of 50 mm Hg or less at each time of measure. Many values were 30 to 40 mm Hg less than the ideal for control of bacteria and healing. • Conclusions The frequency of low oxygen levels is consistent with data from earlier studies. Determination of other interventions to improve subcutaneous tissue perfusion in cardiac surgery patients is needed.