Fluid management is complex and variable. Some studies tend to support restrictive fluid management, but the controversy over fluid management has never ceased. Zhang et al. enrolled 301 patients for a retrospective study, and the results showed that higher postoperative fluid balance appeared to be associated with morbidity after PD, systemic inflammatory response syndrome (SIRS), acute respiratory distress syndrome (ARDS), bleeding, and heart failure (17). However, Meyhoff et al. performed an international, randomized trial among adult patients with septic shock in the ICU and found that intravenous fluid restriction did not decrease mortality at 90 days compared with standard intravenous fluid therapy (18).
The relationship between intraoperative fluid balance and the specific abdominal complication of POPF is also ambiguous. Some studies have demonstrated that the incidence of POPF in the high fluid volume group was higher than that in the low fluid volume group during PD, and intraoperative fluid excess was also considered a risk factor for POPF (19–23). Nevertheless, in 2017, a meta-analysis evaluated the relationship between the perioperative fluid balance and postoperative complications of PD (including POPF), and no significant correlation was found (24). Similarly, a meta-analysis published in 2018 demonstrated that intraoperative fluid balance did not affect the occurrence of POPF (25). Interestingly, a retrospective cohort study showed that intraoperative fluid balance did not affect the incidence of POPF, but the higher cumulative fluid balance per body weight (FBPBW) at postoperative day 3 was an independent risk factor for CR-POPF (26). Other studies have also demonstrated that patients with a high postoperative fluid balance presented a higher incidence of POPF (27–29). Although the related mechanisms have not been thoroughly studied, there are some plausible claims. Trauma of the pancreatic surface in the PD procedure and leakage of a pancreatic-enteric anastomosis are the main reasons for POPF (12). Fluid overload could cause pancreatic parenchyma and intestinal edema, increase the distance between capillaries and cells, impair gas exchange, and then lead to dysfunction or disruption of the pancreatojejunostomy (30, 31).
The study consecutively enrolled 567 patients who underwent PD surgery, and they were divided into four groups by the quartiles of intraoperative fluid balance to explore any difference in POPF between the four groups. Then, intraoperative fluid balance was regarded as a continuous variable, and we used restricted cubic splines to analyze whether a dose‒response relationship existed between intraoperative fluid balance and POPF. Finally, the relationship was found to be statistically insignificant. In addition, we did not find an association between intraoperative fluid balance and BL, DEG, or PPH. Identically, Braga et al. grouped patients undergoing PD according to whether they received a comprehensive ERAS protocol or standard perioperative care. A comprehensive ERAS protocol contained many items, such as a lack of bowel preparation and shortening of the preoperative fasting period, and the intravenous fluid infusion rate was lower in the ERAS group. The results showed that the incidence of POPF was similar in the two groups, as were BL, DGE, and PPH (32).
Sex, BMI, fasting blood glucose level, pancreatic texture, pancreatic duct, pancreatojejunostomy anastomosis technique, and tumor location were related risk factors for POPF. Our study found that BMI ≥ 25kg/m2, preoperative hypoglycemia (blood glucose ≤ 6 mmol/L), long surgery time, and lesion not located in the pancreas were risk factors for POPF. Preoperative hypoglycemia, lesions not located in the pancreas, and BMI might lead to a softer pancreas, thereby influencing the occurrence of POPF (7–10). In addition, when the operation was complicated and difficult, the surgery took longer, and there was a tendency to develop related postoperative complications. As the most critical complication of PD, the treatment and prevention of POPF have been the main concerns for pancreatic surgeons. Besides early identification of related risk factors for POPF, other contemporary mitigation strategies include the use of abdominal drains, prophylactic somatostatin analogues, modified anastomotic techniques, and anastomotic stents (33). Recently, a study showed that coronary artery stent (CAS) positioning in PJ anastomosis could be a novel mitigation strategy in the prevention of POPF (34).
The definition of POPF is relatively uniform in many studies, but the calculation of perioperative fluid balance or fluid management varies. There is no uniform standard for the definition of perioperative fluid balance or fluid management, especially for the cutoff values, which can vary (20–23), and this makes it difficult to integrate and summarize the results of current clinical studies. Relevant research results should be treated with caution. Many anesthesiologists still use the conventional infusion regimen described in textbooks when formulating plans before major surgery. Our definition of fluid balance was based on that. However, the conventional infusion regimen took the patient’s perioperative physiological needs and the third space fluid loss into account; patients were thought to be relatively hypovolemic and therefore required relatively more aggressive fluid replacement. This explains why many patients received a negative intraoperative balance in our study. Our definition of intraoperative fluid balance consisted of the surgery time and patient weight, which helped to reduce the impact of the surgery time and patient weight on intraoperative fluid balance. The intraoperative RBC and colloid infusion in Q3 and Q4 was higher than that in Q1 and Q2. However, intraoperative fluid balance was an integrated variable, and it was difficult for us to explain whether the intraoperative RBC and colloid infusion affected the incidence of POPF. Moreover, we did not consider the difference in the volume effect of crystalloids and colloids when calculating the intraoperative fluid balance.
Many anesthesiologists formulate the intraoperative fluid management plans in advance based on the patient’s physiological needs. In fact, the intraoperative fluid management is affected by many factors, such as intraoperative bleeding, patient cardiovascular function, depth of anesthesia, and use of vasoactive drugs in a major surgery such as PD. Therefore, many anesthesiologists often use invasive monitoring methods in combination with other hemodynamic parameters to evaluate the patient's volume status and adjust their fluid management plan in a timely manner. As a result, the concept of goal-directed fluid therapy (GDFT) may be the most reasonable fluid management strategy available.
Limitation
The present study had some limitations. First, this study analyzed the association between intraoperative fluid balance and the incidence of POPF but did not further analyze the effect of intraoperative fluid balance on the severity of POPF. Second, it was a retrospective analysis in which our data lacked some variables involved in the operation. Confounding factors such as pancreatic texture and pancreatic duct played an influential role in whether pancreatic fistula occurred. Third, all the patients were treated at a single center. To validate the effect of intraoperative fluid balance on POPF, a multicenter study with a larger number of patients is needed in the future.