Augmented Renal Clearance in Neurocritical Care Patients: A Narrative Review

Augmented renal clearance (ARC), defined as a creatinine clearance exceeding 130 mL/min/1.73 m², is a recognised yet underdiagnosed phenomenon in critically ill patients that carries significant pharmacokinetic implications, particularly for renally eliminated drugs such as beta-lactam antibiotics, vancomycin, and antiepileptic agents. While ARC has been well described in burns and trauma populations, its prevalence in the neurocritical care setting is disproportionately high, ranging from 82% to 100% across studies of traumatic brain injury, subarachnoid haemorrhage, and intracerebral haemorrhage, likely reflecting the unique interplay of hyperdynamic circulation, neuroendocrine and brain-kidney interactions, cerebral perfusion pressure-targeted therapies, and osmotic interventions that characterise this population. Standard serum creatinine and estimated glomerular filtration rate equations consistently underestimate renal clearance in this context, making measured urinary creatinine clearance and validated scoring tools such as the ARCTIC score essential for accurate identification. The pharmacokinetic consequences of ARC, including subtherapeutic drug concentrations, altered volume of distribution, and accelerated drug elimination may lead to treatment failure or breakthrough clinical events, consequences that are particularly catastrophic in neurosurgical patients where adequate antimicrobial, anticoagulant, and antiepileptic drug exposure is critical. Despite convincing pharmacokinetic evidence, translation to clinical outcome data remains inconsistent, underscoring the need for individualised, pharmacokinetic/pharmacodynamic-guided dosing strategies, including optimised loading doses, prolonged or continuous infusions for beta-lactams, AUC/MIC-targeted vancomycin monitoring, and regular reassessment of antiepileptic dosing. This review summarises the pathophysiology, prevalence, evaluation, and pharmacological implications of ARC in critically ill neurosurgical patients and proposes a pragmatic bedside framework to guide individualised drug dosing in this high-risk population.