Content – Comparing Survival by RRT Modality in Patients With Severe Burns

Findings from numerous studies indicate that patients with burns who develop acute kidney injury (AKI) in the ICU have an increased mortality rate when compared with those who do not develop AKI, explains David M. Hill, PharmD. “Mortality is exponentially higher when AKI occurs in patients with thermal or inhalation injuries,” he adds, “with a meta-analysis of 60 years-worth of literature noting a median 80% mortality rate for patients with AKI requiring renal replacement therapy (RRT). Ideally, interventions should target early cessation of injury progression, as limiting overall injury can lead to prompter recovery and less long-term morbidity. However, much remains unknown regarding optimal treatments to detect and treat AKI, and data are mixed on the use of RRT to optimize treatment. Evidence is also conflicting on how soon to initiate RRT, preferred modality, dose, and membrane characteristics. Severe thermal and inhalation injuries carry extra concerns, as they are marked by exaggerated systemic responses. Compounding this with sepsis leads to catastrophic results for the patients. Answers are needed to best address treatment strategies to improve survival and long-term morbidity in this setting.”

 Analyzing RRT & Outcomes in Burn Centers

For a paper published in Blood Purification, Dr. Hill and colleagues conducted a subset analysis of a multicenter, observational cohort study aimed at analyzing RRT prescribing practices and patient outcomes among adults admitted to burn centers with severe burn injuries. “We compared survival based on therapy modality, prescribed therapy dose, and presence of shock or inhalation injury using Kaplan-Meier analysis,” notes Dr. Hill. Among participants, demographics and revised Baux were similar.

Compared with all other modalities, continuous venovenous hemofiltration (CVVH) had a survival rate that was greater but not significantly different (56% vs 43%). However, survival was significantly improved among the subset of patients that required vasopressors (54% vs 37%), and there was a marked divergence in survival, favoring those who were prescribed hemofiltration doses greater than 35 ml/kg/hr, says Dr. Hill. No statistically significant survival differences were found in patients with inhalation injury (38% vs 29%) or acute lung injury/acute respiratory distress syndrome (51% vs 33%), but the study was not powered to do so.

When assessing participants without regard to RRT decisions, non-survivors in the study were significantly older, had large burns, and were more likely to sustain an inhalation injury when compared with survivors, whereas survivors were significantly less likely to require vasopressors (Table). “The non-survivors in the 170 patient cohort had characteristics that were similar and supported by existing literature, making the subsequent differences found within the subset analysis of RRT modality even more remarkable,” explains Dr. Hill.

 Attenuating Further Damage & Expediting Healing

When considering future research, Dr. Hill notes that while hemofiltration is a unique modality facilitating removal of a large range of solutes, it is often limited by membranes (material and pore size) and requires adequate force (dose) to optimize clearance. “Studies are needed to determine if early interruption in disease progression using high-volume hemofiltration can improve morbidity and mortality in burn center patients with thermal or inhalation injury that develop kidney injuries. We have demonstrated the potential benefit, but also the difficulties regarding trial design, enrollment, and obtaining financial support. Renal dysfunction occurs at a substantial rate in thermal injury, or as a result of shock, and consequently carries an unacceptably high mortality rate. The potential impact of finding a solution warrants further investigation and the required personal and financial investments.”

In the meantime, with patients with severe burn injuries shown to be more likely to develop kidney issues, Dr. Hill suggests that “prompt recognition could prevent progression to serious damage and subsequent morbidity and mortality. There should be a measured focus on quickly identifying and reversing causation, such as adequate perfusion, cessation of potentially offending agents, and sepsis treatment. Patients developing AKI should be treated quickly and aggressively to attenuate further damage and expedite healing.”