Assessment of thoracic fluid volume in polytrauma patients with different body mass indexes under standard and restrictive infusion therapy regimens

Background. Capillary-leak-driven fluid overload is a frequent complication in polytrauma, and obesity further amplifies this risk because standard body-weight– based resuscitation may overestimate the true distribution volume. Purpose – to evaluate how different body-mass-index categories and two infusionvolume calculation strategies influence thoracic fluid accumulation during the first week after injury. Materials and methods. A prospective cohort of 106 adults with polytrauma that included closed abdominal injury underwent emergency laparotomy and was divided into four groups: normal BMI (18.5 – 24.9 kg/m², n = 34), overweight (25 – 29.9 kg/m², n = 36), obese I with conventional fluid dosing (30–34.9 kg/m², actual body weight, n = 21), and obese I with restrictive dosing based on ideal body weight (IBW, n = 15). Daily intravenous volumes were 30 ml × actual weight + pathologic losses in groups 1–3 and 40 ml × IBW + losses in group 4. Thoracic fluid content (TFC) was measured by 60-kHz electrical bioimpedance on days 1, 3, 5, 7; hemoglobin levels were recorded before and 1 h after initial resuscitation. Results. On day 1 the obese-conventional group exhibited the highest TFC (7.19 ± 0.58 L) compared with normal (6.45 ± 0.49 L), overweight (6.76 ± 0.71 L), and obese-IBW patients (6.67 ± 0.53 L; P < 0.05) and maintained this excess throughout the study period. Hemoglobin fell more sharply in the obese-conventional cohort (-24.3 ± 6.3 g/L) versus the other groups (-27.9 ± 8.3 g/L in normal weight; P < 0.05), indicating greater hemodilution. Restrictive IBW-based dosing mitigated thoracic fluid accumulation to values comparable with non-obese patients despite similar injury severity scores and operative blood loss. Conclusions. Calculating infusion volumes from actual body weight in obese polytrauma patients leads to clinically significant thoracic fluid overload and greater hemodilution. A restrictive regimen using ideal body weight better preserves fluid balance and may lower the risk of pulmonary complications. Adoption of IBW-guided dosing should be considered when managing early resuscitation in this population.