Impact of continuous hypertonic (NaCl 20%) saline solution on renal outcomes after traumatic brain injury (TBI): a post hoc analysis of the COBI trial

BACKGROUND: To evaluate if the increase in chloride intake during a continuous infusion of 20% hypertonic saline solution (HSS) is associated with an increase in the incidence of acute kidney injury (AKI) compared to standard of care in traumatic brain injury patients. METHODS: In this post hoc analysis of the COBI trial, 370 patients admitted for a moderate-to-severe TBI in the 9 participating ICUs were enrolled. The intervention consisted in a continuous infusion of HSS to maintain a blood sodium level between 150 and 155 mmol/L for at least 48 h. Patients enrolled in the control arm were treated as recommended by the latest Brain Trauma foundation guidelines. The primary outcome of this study was the occurrence of AKI within 28 days after enrollment. AKI was defined by stages 2 or 3 according to KDIGO criteria. RESULTS: After exclusion of missing data, 322 patients were included in this post hoc analysis. The patients randomized in the intervention arm received a significantly higher amount of chloride during the first 4 days (intervention group: 97.3 ± 31.6 g vs. control group: 61.3 ± 38.1 g; p < 0.001) and had higher blood chloride levels at day 4 (117.9 ± 10.7 mmol/L vs. 111.6 ± 9 mmol/L, respectively, p < 0.001). The incidence of AKI was not statistically different between the intervention and the control group (24.5% vs. 28.9%, respectively; p = 0.45). CONCLUSIONS: Despite a significant increase in chloride intake, a continuous infusion of HSS was not associated with AKI in moderate-to-severe TBI patients. Our study does not confirm the potentially detrimental effect of chloride load on kidney function in ICU patients. Trial registration: The COBI trial was registered on clinicaltrial.gov (Trial registration number: NCT03143751, date of registration: 8 May 2017). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13054-023-04311-1.