The influence of hypophosphatemia on outcomes of low- and high-intensity continuous renal replacement therapy in critically ill patients with acute kidney injury

Phosphate level predicts mortality in acute kidney injury patients undergoing continuous kidney replacement therapy and has a U-shaped association with mortality in patients with high disease severity: a multicenter retrospective study

BACKGROUND

This study investigated the association between serum phosphate level and mortality in acute kidney injury (AKI) patients undergoing continuous kidney replacement therapy (CKRT) and evaluated whether this association differed according to disease severity.

METHODS

Data from eight tertiary hospitals in Korea were retrospectively analyzed. The patients were classified into four groups (low, normal, high, and very high) based on their serum phosphate level at baseline. The association between serum phosphate level and mortality was then analyzed, with further subgroup analysis being conducted according to disease severity.

RESULTS

Among the 3,290 patients identified, 166, 955, 1,307, and 862 were in the low, normal, high, and very high phosphate groups, respectively. The 90-day mortality rate was 63.9% and was highest in the very high group (76.3%). Both the high and very high groups showed a significantly higher 90-day mortality rate than did the normal phosphate group (high: hazard ratio [HR], 1.35, 95% confidence interval [CI], 1.21-1.51, p < 0.001; very high: HR, 2.01, 95% CI, 1.78-2.27, p < 0.001). The low group also exhibited a higher 90-day mortality rate than did the normal group among those with high disease severity (HR, 1.47; 95% CI, 1.09-1.99; p = 0.01) but not among those with low disease severity.

CONCLUSION

High serum phosphate level predicted increased mortality in AKI patients undergoing CKRT, and low phosphate level was associated with increased mortality in patients with high disease severity. Therefore, serum phosphate levels should be carefully considered in critically ill patients with AKI.

Adult-onset hypophosphatemic osteomalacia as a cause of widespread musculoskeletal pain: A retrospective case series of single center experience

BACKGROUND

Osteomalacia (OM) is frequently confused with various musculoskeletal or other rheumatic diseases, especially in patients with adult-onset widespread musculoskeletal pain because of its low prevalence and non-specific manifestations.

AIM

To facilitate the early diagnosis and etiology-specific treatment of adult-onset hypophosphatemic OM.

METHODS

A retrospective review of medical records was performed to screen adult patients who visited a physiatry locomotive medicine clinic (spine and musculoskeletal pain clinic) primarily presenting with widespread musculoskeletal pain at a single tertiary hospital between January 2011 and December 2019. We enrolled patients with hypophosphatemia, high serum bone-specific alkaline phosphatase levels, and at least one imaging finding suggestive of OM.

RESULTS

Eight patients with adult-onset hypophosphatemic OM were included. The back was the most common site of pain. Proximal dominant symmetric muscle weakness was observed in more than half of the patients. Bone scintigraphy was the most useful imaging modality for diagnosing OM because radiotracer uptake in OM showed characteristic patterns. Six patients were diagnosed with adefovir (ADV)-induced Fanconi syndrome, and the other two patients were diagnosed with tumor-induced OM and light-chain nephropathy, respectively. After phosphorus and vitamin D supplementation and treatment for the underlying etiologies, improvements in pain, muscle strength, and gait were observed in all patients.

CONCLUSION

Mechanical pain characteristics, hypophosphatemia, and distinctive bone scintigraphy patterns are the initial diagnostic indicators of adult-onset hypophosphatemic OM. ADV-induced Fanconi syndrome is the most common etiology of hypophosphatemic OM in hepatitis B virus-endemic countries.

Lower mean phosphate independently predicts mortality in critically ill patients: Results from a prospective cohort study

PURPOSE

To evaluate lower mean phosphate as a prognostic tool in critically ill patients.

METHODS

This is a prospective single-center cohort study including adult patients (> 18 years) with a length of intensive care unit (ICU) stay of at least 24 h. Phosphatemia was evaluated within 1 h of ICU admission and once daily. Mean phosphate, calculated by the simple arithmetic mean of daily phosphate measurements, was proposed and tested. Standard severity scores were applied. Multivariate and survival analyses were performed.

RESULTS

A total of 317 patients were included, of whom 111 (35%) presented hypophosphatemia. Hypophosphatemia associated with surgical conditions, nutritional therapy, hypovitaminosis D, hyperparathyroidism, mechanical ventilation (need and duration), and ICU and hospital length of stay were evaluated. Admission APACHE II and SOFA (ICU days 1, 3, and 7) scores and ICU and in-hospital mortality were greater in the hypophosphatemia group than control group. Higher APACHE II (RR: 1.1; 95%CI: 1.01-1.2; p = 0.045) and lower mean phosphate (RR: 0.02; 95%CI: 0.001-0.09; p = 0.044) independently predicted ICU and in-hospital mortality.

CONCLUSIONS

Hypophosphatemia is frequent in the ICU, and was associated with unfavorable outcomes. This study introduces the importance of longitudinal monitoring of phosphate levels, since lower mean phosphate is an independent predictor of mortality in critically ill patients.

Relationship between serum phosphate and mortality in critically ill children receiving continuous renal replacement therapy

Purpose

We aimed to explore the relationship between serum phosphate concentration and 90-day mortality in critically ill children receiving continuous renal replacement therapy (CRRT).

Methods

Data from the medical records of children aged <13 years who received CRRT at the Pediatric Intensive Care Unit of Hunan Children's Hospital, China from January 2015 to June 2020 were retrospectively collected. Children were grouped into four categories according to the baseline phosphate concentration before CRRT and mean serum phosphate concentration during CRRT: <0.81 mmol/L (hypophosphatemia), 0.81-1.19 mmol/L, 1.2-2.4 mmol/L (normal phosphate concentration), and >2.4 mmol/L (hyperphosphatemia), with the normal phosphate group serving as the comparator group. The correlation of the serum phosphate concentration before and during CRRT with the 90-day mortality after CRRT initiation was analyzed using logistic regression.

Results

A total of 177 children were included in our study. The mean serum phosphate concentration before CRRT was 1.46 mmol/L (quartiles: 1.04, 2.20). The 90-day mortality rate was increased in children with a serum phosphate concentration >2.4 mmol/L before CRRT (adjusted odds ratio [aOR] 3.74, 95% confidence interval [CI] 1.42-9.86, P = 0.008). The mean serum phosphate concentration during CRRT was 1.2 mmol/L (quartiles: 0.91, 1.49). The 90-day mortality rate was increased in children with a mean serum phosphate concentration >2.4 mmol/L during CRRT (aOR 7.34, 95% CI 1.59-33.88, P = 0.011).

Conclusion

Hyperphosphatemia before and during CRRT predicts a higher 90-day mortality rate.

Association of Serum Phosphate Derangement With Mortality in Patients on Continuous Renal Replacement Therapy

Background:

There is limited evidence on the association of serum phosphate with mortality in patients receiving continuous renal replacement therapy (CRRT).

Objective:

To assess the association of serum phosphate with mortality in critically ill patients requiring CRRT for acute kidney injury (AKI).

Design:

A cohort study.

Setting:

A tertiary referral hospital in the United States.

Patients:

Acute kidney injury patients receiving CRRT from 2006 through 2015 in intensive care units.

Measurements:

(1) Serum phosphate before CRRT and (2) mean serum phosphate during CRRT were categorized into 3 groups; ≤2.4 (hypophosphatemia), 2.5 to 4.5 (normal serum phosphate group), and ≥4.6 (hyperphosphatemia) mg/dL.

Methods:

Multivariable logistic regression was used to assess the association between serum phosphate and 90-day mortality.

Results:

A total of 1108 patients were included in this study. Of these, 55% died within 90 days after CRRT initiation. Before CRRT, 3%, 30%, and 66% had hypophosphatemia, normophosphatemia, and hyperphosphatemia, respectively. Before CRRT, both hypophosphatemia and hyperphosphatemia were significantly associated with higher 90-day mortality with the adjusted odds ratio (OR) of 2.22 (95% confidence interval [CI]: [1.03, 4.78]) and 1.62 (95% CI: [1.21, 2.18]), respectively. During CRRT, 3%, 85%, and 12% had mean serum phosphate in hypophosphatemia, normophosphatemia, and hyperphosphatemia range. During CRRT, hyperphosphatemia was significantly associated with higher 90-day mortality with adjusted OR of 2.22 (95% CI: [1.45, 3.38]).

Limitations:

Single center, observational design, lack of information regarding causes of serum phosphate derangement.

Conclusion:

Most CRRT patients had hyperphosphatemia before CRRT initiation but maintain normal serum phosphate during CRRT. Before CRRT, hypo- and hyperphosphatemia, and during CRRT, hyperphosphatemia predicted higher mortality.

Trial registration:

Not registered.

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.

Hypophosphatemia and Outcomes in ICU: A Systematic Review and Meta-Analysis

PURPOSE

Hypophosphatemia is reported in up to 5% of hospitalized patients and ranges from 20% to 80% in critically ill patients. The consequences of hypophosphatemia for critically ill patients remain controversial. We evaluated the effect of hypophosphatemia on mortality and length of stay in intensive care unit (ICU) patients.

METHODS

MEDLINE, EMBASE, Cochrane Library (Reviews and Trials), and PubMed were searched for articles in English. The primary outcome was mortality and secondary outcome was length of stay. The quality of evidence was graded using a modified Newcastle-Ottawa Scale.

RESULTS

Our search yielded 828 articles and ultimately included 12 studies with 7626 participants in the analysis. Hypophosphatemia was associated with increased hospital length of stay (2.19 days [95% CI, 1.74-2.64]) and ICU length of stay (2.22 days [95% CI, 1.00-3.44]) but not mortality (risk ratio: 1.13 [95% CI, 0.98-1.31]; P = .09).

CONCLUSIONS

Hypophosphatemia in ICU was associated with increased hospital and ICU length of stay but not all-cause mortality. Hypophosphatemia appears to be a marker of disease severity. Limited number of available studies and varied study designs did not allow for the ascertainment of the effect of severe hypophosphatemia on patient mortality.

Early initiation renal replacement therapy for fluid management to reduce central venous pressure is more conducive to renal function recovery in patients with acute kidney injury

Background:

Acute kidney injury (AKI) is a serious complication in critically ill patients with septic shock treated in the intensive care unit. Renal replacement therapy (RRT) is a treatment for severe AKI; however, the time of initiation of RRT and factors that affect the recovery of kidney function remains unclear. This study was to explore whether early initiation of RRT treatment for fluid management to reduce central venous pressure (CVP) can help to improve patients’ kidney function recovery.

Methods:

A retrospective analysis of septic patients who had received RRT treatment was conducted. Patients received RRT either within 12 h after they met the diagnostic criteria of renal failure (early initiation) or after a delay of 48 h if renal recovery had not occurred (delayed initiation). Parameters such as patients’ renal function recovery at discharge, fluid balance, and levels of CVP were assessed.

Results:

A total of 141 patients were eligible for enrolment: 40.4% of the patients were in the early initiation group (57 of 141 patients), and 59.6% were in the delayed initiation group (84 of 141 patients). There were no significant differences in the characteristics at baseline between the two groups, and there were no differences in 28-day mortality between the two groups (χ² = 2.142, P = 0.143); however, there was a significant difference in the recovery rate of renal function between the two groups at discharge (χ² = 4.730, P < 0.001). More importantly, early initiation of RRT treatment and dehydration to reduce CVP are more conducive to the recovery of renal function in patients with AKI.

Conclusion:

Compared with those who received delayed initiation RRT, patients who received early-initiation RRT for dehydration to reduce CVP have enhanced kidney function recovery.

Hypophosphatemia in critically ill patients with acute kidney injury on renal replacement therapies

Hypophosphatemia is a common but often underestimated electrolyte derangement among intensive care unit (ICU) patients. Low phosphate levels can lead to cellular dysfunction with potentially relevant clinical manifestations (e.g., muscle weakness, respiratory failure, lethargy, confusion, arrhythmias). In critically ill patients with severe acute kidney injury (AKI) renal replacement therapies (RRTs) represent a well-known risk factor for hypophosphatemia, especially if the most intensive and prolonged modalities of RRT, such as continuous RRT or prolonged intermittent RRT, are used. Currently, no evidence-based specific guidelines are available for the treatment of hypophosphatemia in the critically ill; however, considering the potentially negative impact of hypophosphatemia on morbidity and mortality, strategies aimed at reducing its incidence and severity should be timely implemented in the ICUs. In the clinical setting of critically ill patients on RRT, the most appropriate strategy could be to anticipate the onset of RRT-related hypophosphatemia by implementing the use of phosphate-containing solutions for RRT through specifically designed protocols. The present review is aimed at summarizing the most relevant evidence concerning epidemiology, prognostic impact, prevention and treatment of hypophosphatemia in critically ill patients with AKI on RRT, with a specific focus on RRT-induced hypophosphatemia.