Prevention of hypophosphatemia after burn injury with a protocol for continuous, preemptive repletion

Hypophosphatemia in critically ill adults and children - A systematic review

BACKGROUND & AIMS

Phosphate is the main intracellular anion essential for numerous biological processes. Symptoms of hypophosphatemia are non-specific, yet potentially life-threatening. This systematic review process was initiated to gain a global insight into hypophosphatemia, associated morbidity and treatments.

METHODS

A systematic review was conducted (PROSPERO CRD42020163191). Nine clinically relevant questions were generated, seven for adult and two for pediatric critically ill patients, and prevalence of hypophosphatemia was assessed in both groups. We identified trials through systematic searches of Medline, EMBASE, Scopus, Cochrane Central Register of Controlled Trials, CINAHL, and Web of Science. Quality assessment was performed using the Cochrane risk of bias tool for randomized controlled trials and the Newcastle-Ottawa Scale for observational studies.

RESULTS

For all research questions, we identified 2727 titles in total, assessed 399 full texts, and retained 82 full texts for evidence synthesis, with 20 of them identified for several research questions. Only 3 randomized controlled trials were identified with two of them published only in abstract form, as well as 28 prospective and 31 retrospective studies, and 20 case reports. Relevant risk of bias regarding selection and comparability was identified for most of the studies. No meta-analysis could be performed. The prevalence of hypophosphatemia varied substantially in critically ill adults and children, but no study assessed consecutive admissions to intensive care. In both critically ill adults and children, several studies report that hypophosphatemia is associated with worse outcome (prolonged length of stay and the need for respiratory support, and higher mortality). However, there was insufficient evidence regarding the optimal threshold upon which hypophosphatemia becomes critical and requires treatment. We found no studies regarding the optimal frequency of phosphate measurements, and regarding the time window to correct hypophosphatemia. In adults, nutrient restriction on top of phosphate repletion in patients with refeeding syndrome may improve survival, although evidence is weak.

CONCLUSIONS

Evidence on the definition, outcome and treatment of clinically relevant hypophosphatemia in critically ill adults and children is scarce and does not allow answering clinically relevant questions. High quality clinical research is crucial for the development of respective guidelines.

Incidence and Clinical Outcome of Hypophosphatemia in Pediatric Burn Patients

The objective of this study is to investigate the factors associated with serum phosphate concentrations in severely burned children and whether hypophosphatemia is associated with outcome. Seventy-eight children with a total body surface area of 24% (6.0-68.5) were retrospectively analyzed for serum phosphate concentrations during the first 10 days of stay in the intensive care unit (ICU). The method of generalized estimating equations was used to evaluate the effect of the exposure variables for serum phosphate concentrations during the study period. Outcome variables were the probability of ICU discharge at 30 days and time on mechanical ventilation. Potential explanatory variables for clinical outcome were hypophosphatemia (serum phosphate <3.8 mg/dL for children <2 years and <3.5 mg/dL for older children), age, sex, percent total body surface area burn, inhalation injury, and severe sepsis and/or septic shock. Competing-risk analysis was applied to calculate the probability of ICU discharge at 30 days, and death was assumed as the competing event. The rate of hypophosphatemia was 79.5%. Serum phosphate concentrations were associated with C-reactive protein (coefficient: -0.63; 95% confidence interval [CI]: -0.96 to -0.30; P = .001). Hypophosphatemia was independently associated with a 68% decrease in the probability of ICU discharge at 30 days (subhazard ratio: -0.32; 95% CI: 0.20, 0.53; P = .001) and an increase of 2.9 days in mechanical ventilation (coefficient: 2.91; 95% CI: 1.16, 4.66; P = .001). Serum phosphate concentrations in pediatric burn patients are associated with the magnitude of inflammatory response. Hypophosphatemia is associated with decreased probability of ICU discharge and increased time on mechanical ventilation.

Hyperphosphatemia is associated with high mortality in severe burns

Introduction

Phosphate level is often deranged during acute illness, regardless of the presence of kidney injury or not. A few studies described that hypophosphatemia may associated with outcome in patients admitted to the burn unit, but the literatures for hyperphosphatemia is limited. Our study aims to evaluate if hyperphosphatemia, one of the sign of severe tissue damage or kidney injury, will associate with mortality of patients with severe burns.

Materials and methods

The study was a post hoc analysis of prospectively collected data from patients admitted to the burn unit between September 2006 and December 2011. Patients were stratified into normophosphatemic or hyperphosphatemic group by baseline plasma phosphate level. The primary endpoint is 90-day mortality.

Results

Total 301 patients were included (hyperphosphatemia: n = 52; normophosphatemia: n = 249). The hyperphosphatemic group had lower Glasgow Coma Scale, mean arterial blood pressure, hemoglobin level, albumin, and higher TBSA of burns, APACHE II score, ABSI score, Acute kidney injury (AKI), and creatinine. The 90-day mortality was higher in the hyperphosphatemic group than in the normal group (53.8% vs 18.1%, P < .001) and this difference was still significant when adjusting for several confounding factors (hazard ratio, 2.05; 95% CI, 1.17–3.59). Multivariable Cox analysis showed risk factors of mortality included TBSA of burns, hyperphosphatemia, reduced urine output, and APACHE II score.

Conclusions

Our study found in addition to TBSA of burns and inhalation injury, baseline hyperphosphatemia in patients with severe burns is also associated with higher mortality.

Interactions of Phosphate Metabolism With Serious Injury, Including Burns

Approximately 85% of the body's phosphate pool resides within the skeleton. The remaining 15% is stored as high-energy phosphates or in its free form, where it acts as a substrate for adenosine triphosphate (ATP) production. Accordingly, phosphate plays a crucial role in energy metabolism. Trauma and critical illness result in a hypermetabolic state in which energy expenditure increases. The impact of trauma and critical illness on the body's phosphate stores and phosphate-dependent metabolic reactions is poorly understood. We had previously observed that after severe burn trauma, increased energy expenditure is temporally related to a marked reduction in serum concentrations of both parathyroid hormone and fibroblast growth factor 23, both of which have phosphaturic effects. The aim of this article is to describe as far as is known the similarities and differences in phosphate metabolism in different types of injury and to infer what these differences tell us about possible signaling pathways that may link increased phosphate utilization and phosphate retention. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.