In high-risk patients undergoing brain surgery, our study shows that the use of GDFR was associated with a decrease in fluid volumes, less postoperative complications, and a shorter ICU length of stay.
Many studies have investigated the value of goal-directed fluid therapy in patients undergoing major abdominal, vascular, and orthopedic surgeries [3–6]. Conflicting results have been reported, but recent meta-analysis [3–6] has suggested an overall reduction in postoperative morbidity around 25–50%, associated with a 1–2-day reduction in hospital length of stay. As far as we know, this is the first study investigating the effects of a goal-directed fluid strategy in patients undergoing brain surgery. The main objective of goal-directed strategies is to rationalize the way fluid is administered during the perioperative period [10]. A U-shaped relationship has been described between the perioperative fluid volume and postoperative complications [1]. Patients who do not receive enough fluid may develop complications related to hypovolemia, such as acute renal failure, myocardial injury, and cerebral ischemia. On the other hand, patients receiving too much fluid may develop complications associated with fluid overload, such as tissue edema, which may be responsible for prolonged mechanical ventilation and delayed wound healing [11].
For specific surgical procedures, such as pneumonectomy, liver resection, and neurosurgery, the temptation has always been to keep patients as dry as possible to prevent pulmonary edema, surgical bleeding, and brain swelling, respectively. However, blinded or uncontrolled fluid restriction may expose patients to hypovolemia-related complications [1, 12]. We hypothesized that advanced hemodynamic measurements may be useful to prevent both insufficient and excessive fluid management and improve postoperative outcome. We therefore designed an intraoperative fluid management protocol where minimal fluid maintenance with a crystalloid solution (fluid restriction) was combined with the administration of fluid boluses only in case of severe hypovolemia defined by the association of a low cardiac index with a high SVV. The SVV has been shown to be useful to predict fluid responsiveness in many different settings [13]. Pending limitations are respected [9]; SVV >10–13% identifies fluid responder patients with high sensitivity and specificity [13]. We decided to use a higher cutoff value to keep our patients on the “dry” side, but we also decided to allow fluid boluses when SVV was >15% to prevent excessive fluid restriction and hypovolemia-related complications. Goal-directed fluid strategies have the advantage to rationalize the way patients are treated [10]. However, we believe that fluid management protocols must be adapted to clinical and surgical situations. The use of high SVV target values (around 18–20%) has recently been proposed in patients undergoing liver resection to limit surgical bleeding as much as possible [14]. We thought it might be wise to adopt a similar strategy in neurosurgical patients to minimize cerebral edema. With our GDFR protocol, patients received less crystalloid and colloid than the control group, but did not develop more often hypovolemia-related complications such as acute kidney and myocardial injury.
Our study also showed a significant reduction in ICU costs with GDFR, which is logical when considering the observed reduction in ICU length of stay, likely related to the lower number of patients who developed complications (Table 3). Sadique et al. [15] recently reported the financial results of the large UK Optimise trial and showed that patients treated with goal-directed fluid therapy were on average £400 less expensive to treat than control patients. In patients undergoing head and neck surgery in the USA, in whom ICU length of stay was significantly reduced when using goal-directed fluid therapy, Hand et al. [16] recently reported savings exceeding $3000 per patient. Surgical and anesthesia costs in China are not comparable to those observed in the UK or in the USA. However, as suggested by previous studies [17, 18] our financial findings confirm that the improvement in postoperative outcome may offset the costs associated with the implementation of goal-directed fluid therapy.
Our study has several limitations. First, this is a single-center study where we compared a GDFR strategy to standard hemodynamic management at West China Hospital in Chengdu, Sichuan. We also focused on high-risk patients (ASA III & IV). Thus, our results may not be extrapolated to other institutions having different anesthesia and surgical practices, as well as to low-risk (ASA I & II) neurosurgical patients. Three patients had a brain abscess and did not require emergency surgery. Thus, they were considered as elective patients and enrolled in our study. We acknowledge their specificity but confirm that similar results were observed after excluding them from the analysis. Although based on physiological rational, the 15% cutoff value used for SVV was arbitrary and other studies would be useful to investigate whether better results could be observed when using lower (e.g., 13%) or higher (e.g., 18%) cutoff values. Also, we cannot draw any conclusion regarding the superiority of our original GDFR strategy over a more classical goal-directed fluid strategy (e.g., stroke volume optimization) or over fluid restriction alone. The reliability of the FloTrac/Vigileo system to measure cardiac output has been questioned when compared to clinical reference techniques such as pulmonary thermodilution and echocardiography [19]. Of note, most limitations have been described in patients with septic shock receiving vasopressors, or during liver transplantation [20]. Recent meta-analysis of validation studies suggests that both accuracy and precision are comparable to those observed with other continuous cardiac output monitoring techniques currently available on the market [21]. And many studies have demonstrated that FloTrac-derived SVV is an accurate predictor of fluid responsiveness; pending limitations are respected [20].
