Augmented renal clearance, often abbreviated ARC, describes a condition in which the kidneys filter blood at a rate well above what would be expected for a given patient. It has been recognized for more than a decade in critically ill trauma and sepsis patients, where it is usually treated as a pharmacokinetic problem: drugs that are cleared by the kidneys, particularly antibiotics, are eliminated so quickly that standard doses may fail to reach therapeutic levels in the blood. The Montreal team, led by neurosurgeon Kazunori Oda, set out to ask a different question. Rather than viewing the hyperfiltering kidney purely as a dosing challenge, they hypothesized that it might serve as a window into a broader hyperdynamic state, one that also drives the catabolic firestorm that follows severe brain injury.

The study examined intensive care unit admissions of adults with severe traumatic brain injury at a tertiary academic level I trauma center between 2015 and 2024. Because directly measured urinary creatinine clearance was not systematically available in this retrospective setting, the researchers relied on serum-creatinine-estimated creatinine clearance, calculated from routine blood work. They defined estimated augmented renal clearance, or eARC, as an estimated creatinine clearance of at least 130 milliliters per minute per 1.73 square meters of body surface area at one or more time points during the first 28 days after injury. This threshold is consistent with definitions used widely in the critical care literature, where values above 130 are generally considered supranormal.

Of the 342 admissions included in the analysis, eARC occurred in 197 patients, or 57.6 percent. That figure is striking: it means that in this population, a hyperfiltering kidney was the rule rather than the exception. The patients who developed eARC were younger, more often male, and had lower admission Glasgow Coma Scale scores, suggesting more severe impairment of consciousness at presentation. These demographic and clinical associations echo earlier work showing that young trauma patients with robust physiological reserve are the ones most likely to mount an exaggerated renal response, even as their brains bear the brunt of the injury.

The central finding of the study concerns body weight. Patients with eARC experienced a median day-28 body weight loss of 12.7 percent, compared with essentially no change, 0.0 percent, in patients without eARC, a difference that was highly statistically significant. Severe weight loss was also markedly more frequent in the eARC group. To put the magnitude in perspective, a double-digit percentage loss of body mass within a month is far beyond what would be expected from simple fluid shifts or reduced appetite; it points to substantial depletion of lean tissue and fat stores, the kind of catabolic erosion that has been associated with worse outcomes in critically ill and neurotrauma populations.

To make sure the association was not an artifact of confounding, the investigators took a rigorous approach to variable selection, guided by a directed acyclic graph, a formal framework that maps out plausible causal relationships and identifies which covariates must be adjusted for. In exploratory multivariable analysis adjusting for age and admission Glasgow Coma Scale score, eARC remained independently associated with severe day-28 weight loss. The team also ran a battery of sensitivity analyses designed to rule out alternative explanations. They incorporated calories derived from propofol, the sedative commonly infused in brain-injured patients, which is delivered in a lipid emulsion and can contribute substantial energy intake that is often overlooked in nutrition calculations.

Those sensitivity analyses proved revealing in their own right. Once propofol-derived calories were counted, total energy delivery turned out to be similar between the eARC and non-eARC groups, which weakens the argument that the weight loss simply reflected underfeeding. Likewise, serum sodium concentrations, total fluid input, urine output, and the input-minus-urine fluid balance estimate did not show clear group-level differences that could account for the observed weight-loss gap. In other words, the excess weight loss in eARC patients could not be readily explained by either a caloric deficit or by large-scale fluid and electrolyte shifts, leaving a primary metabolic or catabolic mechanism as the leading candidate.

The biological plausibility of such a mechanism is supported by a growing body of literature. Severe traumatic brain injury is known to trigger one of the most intense hypermetabolic states in medicine, with resting energy expenditure and nitrogen excretion rising sharply in the first weeks after injury. Previous observational work has linked augmented renal clearance to increased muscle catabolism and urinary nitrogen loss in trauma patients, and studies of atrial natriuretic peptide and cardiac output in brain-injured patients have suggested that the hyperdynamic circulation driving renal hyperfiltration may be part of a systemic stress response. Creatinine itself is generated from muscle, so a rapidly falling serum creatinine in a catabolic patient can inflate clearance estimates while simultaneously signaling loss of muscle mass, a coupling that the authors acknowledge as a limitation of relying on estimated rather than measured clearance.

The clinical implications, if confirmed, could be substantial. If eARC identifies a metabolically vulnerable subgroup of brain-injured patients, then a routine serum creatinine, a test drawn almost daily in every intensive care unit, could become an early warning flag prompting intensified nutritional surveillance, earlier dietitian involvement, closer monitoring of protein delivery, and perhaps pharmacokinetic dose adjustments for renally cleared drugs. The authors are careful to frame their findings as hypothesis generating. Because the study was retrospective and relied on estimated rather than measured creatinine clearance, and because body weight alone cannot distinguish fluid changes from true tissue loss, they call for prospective studies using directly measured creatinine clearance, detailed sodium and water balance assessment, and direct body composition measures such as bioelectrical impedance or imaging-based muscle quantification.

For now, the study adds an intriguing piece to the puzzle of why some brain injury patients waste away despite modern critical care. It suggests that the kidney, an organ rarely at the center of neurotrauma discussions, may be broadcasting a signal about systemic metabolic state that clinicians have been reading only through a pharmacokinetic lens. With more than half of severe traumatic brain injury patients in the cohort showing supranormal renal filtration, and with that subgroup losing on average nearly 13 percent of their body weight in a month, the case for watching the kidneys as metabolic sentinels has become considerably stronger. Whether aggressive, eARC-guided nutritional intervention can change the trajectory for these patients is the question that prospective research must now answer.

Subject of Research: Augmented renal clearance and metabolic weight loss after severe traumatic brain injury

Article Title: Serum-Creatinine-Estimated Augmented Renal Clearance is Associated with Marked Weight Loss after Severe Traumatic Brain Injury

Article References: Oda, K., Nedelcu, R., Abouassaly, M., Mourad, A. A., Grubb, K., Saluja, R. S., & Marcoux, J. (2026). Serum-Creatinine-Estimated Augmented Renal Clearance is Associated with Marked Weight Loss after Severe Traumatic Brain Injury. Neurocritical Care. https://doi.org/10.1007/s12028-026-02666-1

Image Credits: AI Generated

DOI: 10.1007/s12028-026-02666-1

Keywords: augmented renal clearance, traumatic brain injury, neurocritical care, creatinine clearance, weight loss, nutrition, catabolism, fluid balance, intensive care, hypermetabolism, neurotrauma, propofol

The research, led by Constantin L. Palm of the University of Groningen together with Niels T. B. Scholte of Erasmus MC Rotterdam and a large team of Dutch collaborators, set out to track how plasma ketone bodies evolve in the months following a heart failure hospitalization, and whether those changing levels could predict who would die or be readmitted. Rather than relying on a single blood draw, the investigators measured ketones repeatedly, up to seven times over the course of a year in their primary cohort, using nuclear magnetic resonance spectroscopy, a technique that quantifies β-hydroxybutyrate, acetoacetate and acetone simultaneously with remarkable precision. The NMR results correlated almost perfectly with mass spectrometry reference methods, with R-squared values above 0.99 for each individual ketone species.

The primary dataset came from the TRIUMPH study, an observational prospective trial that enrolled patients hospitalized for acute heart failure across fourteen centers in the Netherlands. Of the 496 patients enrolled, 467 had detectable ketone body measurements and formed the analytical population. These were seriously ill individuals: the median age was 74 years, only 37 percent were women, and a striking 82 percent were in New York Heart Association class III or IV, meaning they experienced symptoms even during minimal physical activity. Blood was collected on admission, on days two and four of the hospital stay, on the day of discharge, and at follow-up visits spanning the subsequent year, yielding a median of four serial samples per patient.

The findings were unambiguous. Patients who went on to experience the combined endpoint of death from any cause or rehospitalization for heart failure, 185 patients or 40 percent of the cohort, carried continuously higher estimated ketone body levels than those who remained event-free. Using sophisticated joint models that combine longitudinal mixed-effects regression with Cox proportional hazards analysis, the researchers calculated that each doubling of total ketone body concentration at any point during follow-up was associated with a 2.10-fold increase in the hazard of the combined endpoint, after adjustment for age, sex, disease severity, kidney function, natriuretic peptide levels and a battery of other clinical confounders. Per doubling, the hazard ratios were 1.62 for acetone and 1.62 for β-hydroxybutyrate, both statistically significant.

Perhaps the most surprising discovery was temporal. The team had expected, based on earlier work showing that ketones fall as patients recover from acute decompensation, that ketone levels would spike in the days or weeks preceding a catastrophic event, much like rising troponin precedes a myocardial infarction. Instead, the estimated ketone trajectories remained persistently elevated in high-risk patients throughout the entire follow-up period, without a dramatic pre-event surge. This pattern suggests that ketone bodies are not simply an acute marker of hemodynamic stress, as natriuretic peptides are, but rather a window into a chronic, smoldering catabolic state that distinguishes patients destined for poor outcomes long before the event itself arrives.

To guard against the possibility that the finding was an artifact of one particular cohort, the researchers turned to Bio-SHiFT, an independent study of 397 patients with chronic heart failure followed at outpatient clinics in Rotterdam and Alkmaar. These patients were younger, with a median age of 64 years, and provided up to ten repeated blood samples over a median follow-up of 2.1 years. During that time, 124 patients, or 31.2 percent, reached the composite endpoint of cardiovascular death, heart failure hospitalization, left ventricular assist device implantation or heart transplantation. Once again, ketone bodies were consistently higher in those who reached the endpoint, with a hazard ratio of 5.36 per doubling of total ketone bodies and 4.24 per doubling of acetone in the adjusted models, an even stronger signal than in the acute cohort.

The biology behind these numbers is intricate. Ketone bodies are produced by the liver during fasting, prolonged exercise or metabolic stress, and in heart failure the failing myocardium increasingly relies on them as fuel, a shift that experimental studies suggest may actually be protective. Supplementation with ketone esters has improved cardiac function in animal models and in early clinical trials, which makes the association between high endogenous ketones and poor outcomes seem paradoxical. The authors are careful to address this: elevated ketones are unlikely to cause harm directly. Rather, they appear to be a compensatory response, a metabolic distress signal broadcast by a body under sustained siege from inflammation, sympathetic overactivation and catabolic wasting.

Several mechanistic threads support this interpretation. The researchers observed that higher ketone levels correlated with worse ejection fraction, higher NT-proBNP, and a reduced likelihood of tolerating beta-blocker therapy, all hallmarks of advanced disease. They propose that inflammation-driven malabsorption creates a fasting-like state that promotes ketogenesis, while heightened activity of the hypothalamic–pituitary axis floods the circulation with catecholamines and cortisol, driving muscle breakdown and insulin resistance that further fuel ketone production. Intriguingly, acetoacetate, the ketone species most subject to rapid interconversion and spontaneous decarboxylation into acetone, showed no association with outcomes in either cohort, whereas the more stable acetone and β-hydroxybutyrate did, suggesting that acetone may best reflect net ketogenesis over time.

The clinical implications are considerable. Dynamic discrimination analysis showed that serially measured ketone bodies performed comparably to NT-proBNP, the current gold-standard prognostic biomarker, with time-dependent area under the curve values ranging from 0.76 to 0.80 in TRIUMPH and 0.77 to 0.82 in Bio-SHiFT. Because ketones capture a dimension of heart failure, chronic metabolic stress, that established biomarkers largely ignore, repeated measurements could complement rather than replace existing tools, helping clinicians identify a subset of patients living in a state of continuous catabolic strain who might benefit from intensified monitoring, metabolic interventions or targeted nutritional strategies. The authors caution that their study was observational, confined to Dutch centers, and included few women, and that the era before SGLT2 inhibitor therapy, drugs known to raise ketone levels, may limit generalizability to contemporary patients. Still, the message is clear: in heart failure, what the liver tells the blood about the body’s metabolic state, told repeatedly over time, may be one of the most honest accounts of the heart’s declining fortunes.

Subject of Research: Serial measurement of plasma ketone bodies as a prognostic biomarker for adverse outcomes in heart failure patients

Article Title: Continuously elevated plasma ketone bodies are linked to adverse outcomes in patients with heart failure

Article References: Palm, C. L., Scholte, N. T. B., Lu, L., Kamar, S. A., Bakker, B. M., Voorrips, S. N., Mahmoud, B., Connelly, M. A., Suthahar, N., de Boer, R. A., Umans, V. A., Akkerhuis, K. M., Hillege, H., Boersma, E., Kardys, I., & Westenbrink, B. D. (2026). Continuously elevated plasma ketone bodies are linked to adverse outcomes in patients with heart failure. Clinical Research in Cardiology. https://doi.org/10.1007/s00392-026-02992-6

Image Credits: AI Generated

DOI: 10.1007/s00392-026-02992-6

Keywords: heart failure, ketone bodies, biomarkers, NT-proBNP, metabolism, prognosis, TRIUMPH study, Bio-SHiFT, nuclear magnetic resonance, cardiology, catabolism, risk stratification