Intra-Abdominal Sepsis in Critically Ill Surgical Patients: The Relationship Between Cumulative Fluid Balance and Serum Sodium and Chloride Levels and In-Hospital Mortality

Radmila Popović^1,2Nada Anđelić²Gordana Jovanović^1,2Sanja Maricic Prijic^1,2Arsen Uvelin^1,2Nataša Tomić²Aleksandra Plećaš Đurić^2,3Nemanja Todorović⁴Boris Milijašević^5*Dejan Živorad Marković^6,7

• ¹Department of Anesthesiology and Perioperative Medicine, Faculty of Medicine, University of Novi Sad, Novi Sad, Vojvodina, Serbia
• ²Clinic for Anesthesia, Intensive Care and Pain Management, University Clinical Center of Vojvodina, Novi Sad, Vojvodina, Serbia
• ³Department of Nursing, Faculty of Medicine, University of Novi Sad, Novi Sad, Vojvodina, Serbia
• ⁴Department of Pharmacy, Faculty of Medicine, University of Novi Sad, Novi Sad, Vojvodina, Serbia
• ⁵Department of Pharmacology, Toxicology and Clinical Pharmacology, Faculty of Medicine, University of Novi Sad, Novi Sad, Vojvodina, Serbia
• ⁶Department of Anesthesiology, Reanimatology and Intensive Care, Clinic for Cardiac Surgery, University Clinical Centre of Serbia, Belgrade, Serbia
• ⁷Faculty of Medicine, University of Belgrade, Belgrade, Serbia

BACKGROUND AND AIM: Intra-abdominal sepsis in critically ill surgical patients has a high mortality rate. Fluid therapy is essential resuscitation measure but can lead to poor outcome due to fluid overload and increased sodium and chloride levels. This study aimed to examine the relationship between cumulative fluid balance, serum sodium and chloride levels in the intensive care unit (ICU), and in-hospital mortality in critically ill surgical patients with intra-abdominal sepsis. METHODS: The study was designed as a retrospective, observational study. Data were collected and analyzed from 100 critically ill surgical patients with intra-abdominal sepsis who were immediately subjected to surgical treatment. Postoperative care continued in the ICU for at least seven days. Data related to daily fluid enteral and parenteral intake and loss were taken from medical records. The cumulative fluid balance was calculated for the periods from days 1 to 3 and 1 to 7 of ICU treatment. RESULTS: In-hospital mortality rate was 51%. The cumulative fluid balance on the third and seventh days of ICU hospitalization was found to be positively correlated with mortality. Statistical analyses revealed significant differences in fluid balance at these time points in relation to mortality (p < 0.0005). ROC analysis confirmed the predictive power of cumulative fluid balance, with an AUC of 0.757 (cutoff: 5130 ml, sensitivity 68.6%, specificity 69.4%) on the third day and AUC of 0.856 (cutoff: 2210 ml, sensitivity 78.4%, specificity 83.7%) on the seventh day. Binary logistic regression further supported the influence of fluid balance on mortality. Sodium and chloride levels remained within the reference range but were significantly higher in patients who died. Binary logistic regression showed that abnormal sodium and chloride levels on the third and seventh days were associated with increased mortality. CONCLUSION: High values of postoperative cumulative fluid balance as well as elevated serum sodium and chloride levels during the first seven days in the ICU may be important predictors of in-hospital mortality in critically ill patients with intraabdominal sepsis who underwent emergency surgical treatment. NCT06838585 https://clinicaltrials.gov/study/NCT06838585?locStr=Novi%20Sad,%20Serbia&country=Serbia&stat e=Vojvodina&city=Novi%20Sad&cond=intra%20abdominal%20sepsis&rank=3