Intravenous phosphate repletion regimen for critically ill patients with moderate hypophosphatemia

Using a Built-in Clinical Decision Support to Improve Phosphate Repletion Practice: A Quasi-Experimental Study

BACKGROUND

Inpatient serum phosphate replacement is common, but there is great variability in replacement practice, which leads to overuse. Electronic health record (EHR) interventions with clinical decision support (CDS) can be effective tools to guide clinicians toward best clinical practices. The authors' objective was to use CDS tools to reduce overuse of hypophosphatemia corrections at a large safety-net health care system.

METHODS

The first intervention involved enhancing an existing order set for phosphate repletion by incorporating CDS to guide appropriate repletion orders based on deficit severity and simplifying ordering. The second intervention was a Best Practice Advisory (BPA) that triggered when an intravenous (IV) phosphate repletion was ordered for a patient with mild to moderate phosphate deficiency without an existing nil per os (NPO) order. The primary outcome measure was the number of patients with mild and moderate hypophosphatemia receiving IV replacement without NPO orders per 1,000 patient-days.

RESULTS

Across all hospitals, rate of IV replacement in patients with mild to moderate hypophosphatemia (1.0 to 1.9 mg/dL) without NPO orders decreased from 7.22 to 3.40 per 1,000 patient-days (53.0% reduction, p < 0.001), while the oral replacements in this population increased from 6.39 to 8.87 (38.8% increase, p < 0.001). For patients with phosphate levels ≥ 2.0, IV replacements decreased from 10.66 to 5.36 (49.8% reduction, p < 0.001), and oral replacements from decreased 19.78 to 16.69 (15.6% reduction, p < 0.01).

CONCLUSION

This intervention successfully reduced inpatient IV phosphate replacements by 53.0% in patients with mild to moderate hypophosphatemia using a two-pronged EHR intervention across a large safety-net setting.

Outcomes of patients with post-hepatectomy hypophosphatemia: A narrative review

Phosphate is an essential electrolyte for proper mineralisation of bone, buffering of urine, and diverse cellular actions. Hypophosphatemia (HP) is a clinical spectrum which range from asymptomatic to severe complications such as neuromuscular and pulmonary complications, or even death. Post-hepatectomy HP (PHH) has been reported to be 55.5%-100%. Post-hepatectomy, there is rapid uptake of phosphate and increased mitotic counts to aid in regeneration of residual liver. Concurrently, PHH may be due to increased urinary phosphorous from activation of matrix extracellular phosphoglycoprotein in the injured liver, which decreases phosphate influx into hepatocytes to sustain adenosine triphosphate synthesis. A literature review was performed on PubMed till January 2022. We included 8 studies which reported on impact of PHH on post-operative outcomes. In patients with diseased liver, PHH was reported to have either beneficial or deleterious effects on post-hepatectomy liver failure (PHLF), morbidity and/or mortality in various cohorts. In living donor hepatectomy, PHLF was higher in PHH. Benefits of correction of PHH with reduced post-operative complications have been shown. Correction of PHH should be done based on extent of PHH. Existing studies were however heterogenous; further studies should be conducted to assess PHH on post-operative outcomes with standardized phosphate replacement regimes.

Hypophosphatemia at Admission is Associated with Increased Mortality in COVID-19 Patients

Background

Electrolyte disturbances are commonly observed in patients with coronavirus disease 2019 (COVID-19) and associated with outcome in these patients. Our study was designed to examine whether hypophosphatemia is associated with mortality in COVID-19 patients.

Methods

Patients diagnosed with COVID-19 and hospitalized in Renmin Hospital of Wuhan University between January 30 and February 24, 2020 were included in this study. Patients were divided into two groups, a hypophosphatemia group and a non-hypophosphatemia group, based on a serum phosphate level of 0.8 mmol/L. Logistic regression was performed to analyze the relationship between hypophosphatemia and mortality. A locally weighted scatterplot smoothing (LOWESS) curve was plotted to show the detailed association between mortality rate and serum phosphate level. A Kaplan–Meier survival curve was drawn to compare the difference in cumulative survival between the two groups.

Results

Hypophosphatemia at admission occurred in 33 patients, with an incidence of 7.6%. The hypophosphatemia group had a significantly higher incidence of respiratory failure (54.5% vs 32.6%, p=0.013) and mortality (57.6% vs 15.2%, p<0.001). Multivariate logistic regression indicated that age (OR=1.059, p<0.001), oxygen saturation (OR=0.733, p<0.001), white blood cells (OR=1.428, p<0.001), lymphocytes (OR=0.075, p<0.001) and hypophosphatemia (OR=3.636, p=0.015) were independently associated with mortality in the included patients. The hypophosphatemia group had significantly shorter survival than the non-hypophosphatemia group (p<0.001).

Conclusion

Hypophosphatemia at admission is associated with increased mortality in COVID-19 patients. More attention and medical care should be given to COVID-19 patients with hypophosphatemia at admission.

[Prescription of phosphorus, calcium and magnesium: choice of the millimole unit to establish the equivalence of doses between oral and injectable forms]

OBJECTIVES

Information available on the packaging of drugs indicated for patients electrolytes replenishment differs from one manufacturer to another. They relate, for example, the unit chosen to express elemental electrolyte concentration. These differences constitute a risk factor for medication errors. This article proposes a clinical decision support tool which defines dose equivalences between the oral and injectable formulation galenic forms for medications providing phosphorus, calcium and magnesium and a calculated replenishment ratio.

METHODS

The amounts of elemental electrolyte were determined from the information contained on the packaging and the summaries of product characteristics. Only the specialties of our hospital drug formulary were studied. For each element, the replenishment ratio was determined from published data.

RESULTS

Equivalence tables were created for the phosphorus, calcium and magnesium between oral and injectable formulation. A clinical decision support tool was developed from these data.

CONCLUSION

The use of this tool is a first way to reduce the risk of medication errors. It remains to determine the conditions for its dissemination and evaluation. This issue raises the questions of the exclusive use of the millimole unit on packaging and for prescription, and that of the integration of this type of tool into prescription software and decision support systems.

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 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.

Hypophosphatemia in Enterally Fed Patients in the Surgical Intensive Care Unit: Common but Unrelated to Timing of Initiation or Aggressiveness of Nutrition Delivery

INTRODUCTION

Hypophosphatemia has been associated with refeeding malnourished patients, but its clinical significance is unclear. We investigated the incidence of refeeding hypophosphatemia (RH) in the surgical intensive care unit (SICU) and its association with early enteral nutrition (EN) administration and clinical outcomes.

METHODS

We performed a retrospective review of a 2-year database of patients receiving EN in the SICU. RH was defined as a post-EN phosphorus (PHOS) level decrement of >0.5 mg/dL to a nadir <2.0 mg/dL within 8 days from EN initiation. We investigated the risk factors for RH and examined its association with clinical outcomes using multivariable regression analyses.

RESULTS

In total, 213 patients comprised our analytic cohort. Eighty-three of 213 (39%) individuals experienced RH and 43 of 130 (33%) of the remaining patients experienced non-RH hypophosphatemia (nadir PHOS level <2.0 mg/dL). Overall, there was a total 59% incidence of hypophosphatemia of any cause (N = 126). Nutrition parameters did not differ between groups; most patients were initiated on EN within 48 hours of SICU admission, and timing of EN initiation was not a significant predictor for the development of RH. The median hospital length of stay (LOS) was 21 and 24 days for those with and without RH, respectively (P = .79); RH remained a nonsignificant predictor for hospital LOS in the multivariable analysis.

CONCLUSIONS

RH is common in the SICU but is not related to timing or amount of EN. Hypophosphatemia is also common in the critically ill, but regardless of etiology, it was not found to be a predictor of worse clinical outcomes.

Phosphatemic Control during Acute Renal Failure: Intermittent Hemodialysis versus Continuous Hemodiafiltration

Background

Achieving “adequacy of dialysis” includes the maintenance of normal serum phosphate concentrations and is an important therapeutic goal in the treatment of acute renal failure (ARF). It is unknown whether this goal is best achieved with intermittent or continuous renal replacement therapy.

Methods

We compared the effects of continuous veno-venous hemodiafiltration (CVVHDF) and intermittent hemodialysis (IHD) on serum phosphate concentrations using daily morning blood tests in 88 consecutive intensive care patients half of which were treated with IHD and half with CRRT.

Results

Mean patient age was 54 ± 14 years for IHD and 60 ± 14 years for CVVHDF (NS). However, patients who received CVVHDF were more critically ill (mean APACHE II scores: 24.4 ± 5.1 for IHD vs. 29.2 ± 5.7 for CVVHDF, p<0.003). Before treatment, the serum phosphate concentration was 2.04 ± 0.16 mmoll L for IHD and 1.96 ± 0.17 mmoll L for CVVHDF (NS), with abnormal values in 79.4% of IHD patients and in 64.8% of CVVHDF patients (NS). During treatment, CVVHDF induced a greater reduction in serum phosphate (p=0.02) during the first 48 hours and conferred superior subsequent control of hyperphosphatemia (achieved in 64.6% of observations during CVVHDF vs. 41.8% during IHD; p<0.0001). The serum phosphate concentration was also more likely to be within the normal range during CVVHDF (55.3% vs.36.2%; p<0.0001). There was a trend toward more frequent hypophosphatemia (9.3% vs. 5.6%; P<0.1) during CVVHDF.

Conclusions

Abnormal serum phosphate concentrations are frequent in ARF patients before and during renal replacement, however, normalization of phosphatemia is achieved more frequently with CVVHDF.

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

BACKGROUND

The purpose of this study was to assess the role of hypophosphatemia in major clinical outcomes of patients treated with low- or high-intensity continuous renal replacement therapy (CRRT).

METHODS

We performed a retrospective analysis of data collected from 492 patients. We divided patients into two CRRT groups based on treatment intensity (greater than or equal to or less than 40 mL/kg/hour of effluent generation) and measured serum phosphate level daily during CRRT.

RESULTS

We obtained a total of 1,440 phosphate measurements on days 0, 1, and 2 and identified 39 patients (7.9%), 74 patients (15.0%), and 114 patients (23.1%) with hypophosphatemia on each of these respective days. In patients treated with low-intensity CRRT, there were 23 episodes of hypophosphatemia/1,000 patient days, compared with 83 episodes/1,000 patient days in patients who received high-intensity CRRT (P < 0.01). Multiple Cox proportional hazards analysis showed that Acute Physiology and Chronic Health Evaluation (APACHE) III score, utilization of vasoactive drugs, and arterial pH on the second day of CRRT were significant predictors of mortality, while serum phosphate level was not a significant contributor to mortality.

CONCLUSION

APACHE score, use of vasoactive drugs, and arterial pH on the second CRRT day were identified as significant predictors of mortality. Hypophosphatemia might not be a major risk factor of increased mortality in patients treated with CRRT.

Refeeding Syndrome and Hypophosphatemia

Hypophosphatemia is a potentially life-threatening complication of reinstating nutrition in a malnourished patient. Refeeding syndrome is a term that refers to various metabolic abnormalities that may complicate carbohydrate administration in subnourished patient populations. Hypophosphatemia is the most well-known, and perhaps most significant, element of the refeeding syndrome and may result in sudden death, rhabdomyolysis, red cell dysfunction, and respiratory insufficiency. This review briefly examines refeeding-induced hypophosphatemia in the hospitalized patient in hopes of making clinicians more aware of this common, but often overlooked, potentially dangerous problem.

Phoxilium(®) reduces hypophosphataemia and magnesium supplementation during continuous renal replacement therapy

Background

Although associated with severe clinical complications, phosphate remains a neglected ion. Additionally, phosphate balance during continuous renal replacement therapy (CRRT) is complex and multifunctional. The present retrospective study investigated the effects of phosphate-containing CRRT fluid on phosphate homeostasis.

Methods

We retrospectively analysed 112 patients treated with CRRT at Skåne University Hospital, Sweden. The control group was treated with Hemosol^® B0 (no phosphate; n = 36) as dialysis and replacement fluid, while the study group received Phoxilium^® (phosphate; n = 76) as dialysis fluid and Hemosol^® B0 as replacement fluid.

Results

Hypophosphataemia (<0.7 mM) occurred in 15% of the treatment days in the control group compared with 7% in the study group (P = 0.027). Magnesium substitution was reduced by 40% in the study group (P < 0.001). No differences in acid–base parameters were detected between the groups.

Conclusions

In this larger cohort, we could confirm that Phoxilium^® reduced the episodes of hypophosphataemia during CRRT. A beneficial effect on magnesium balance could also be observed.

Pathophysiology, treatment, and prevention of fluid and electrolyte abnormalities during refeeding syndrome

Refeeding syndrome may occur after the reintroduction of carbohydrates in chronically malnourished or acutely hypermetabolic patients as a result of a rapid shift to glucose utilization as an energy source. Electrolyte abnormalities of phosphorus, potassium, and magnesium occur, leading to complications of various organ systems, and may result in death. Patients should be screened for risk factors of malnutrition to prevent refeeding syndrome. For those at risk, nutrition should be initiated and slowly advanced toward the patient's goal over several days. Electrolyte disturbances should be aggressively corrected.

Phosphorus and calcium: a review for the adult nutrition support clinician

Phosphorus (P) and calcium (Ca) serve vital roles in the human body and are essential components of nutrition support therapy. Regulation of P and regulation of Ca in the body are closely interrelated, and P and Ca homeostasis can be affected by several factors, including disease states, clinical condition, severity of illness, and medications. Nutrition support clinicians must understand these factors to prevent and treat P and Ca disorders in patients receiving nutrition support therapy. This review provides an overview of P and Ca for the adult nutrition support clinician, with some emphasis on the hospitalized inpatient.

Phosphate homeostasis and disorders

Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.

Hypophosphatemia during continuous veno-venous hemofiltration is associated with mortality in critically ill patients with acute kidney injury

Introduction

The primary aim of this study was to determine whether hypophosphatemia during continuous veno-venous hemofiltration (CVVH) is associated with the global outcome of critically ill patients with acute kidney injury (AKI).

Methods

760 patients diagnosed with AKI and had received CVVH therapy were retrospectively recruited. Death during the 28-day period and survival at 28 days after initiation of CVVH were used as endpoints. Demographic and clinical data including serum phosphorus levels were recorded along with clinical outcome. Hypophosphatemia was defined according to the colorimetric method as serum phosphorus levels < 0.81 mmol/L (2.5 mg/dL), and severe hypophosphatemia was defined as serum phosphorus levels < 0.32 mmol/L (1 mg/dL). The ratio of CVVH therapy days with hypophosphatemia over total CVVH therapy days was calculated to reflect the persistence of hypophosphatemia.

Results

The Cox proportional hazard survival model analysis indicated that the incidence of hypophosphatemia or even severe hypophosphatemia was not associated with 28-day mortality independently (p = 0.700). Further analysis with the sub-cohort of patients who had developed hypophosphatemia during the CVVH therapy period indicated that the mean ratio of CVVH therapy days with hypophosphatemia over total CVVH therapy days was 0.58, and the ratio independently associated with the global outcome. Compared with the patients with low ratio (< 0.58), those with high ratio (≥ 0.58) conferred a 1.451-fold increase in 28-day mortality rate (95% CI 1.103–1.910, p = 0.008).

Conclusions

Hypophosphatemia during CVVH associated with the global clinical outcome of critically ill patients with AKI. The ratio of CVVH therapy days with hypophosphatemia over total CVVH therapy days was independently associated with the 28-day mortality, and high ratio conferred higher mortality rate.

Approach to the hypophosphatemic patient

Hypophosphatemia is commonly missed due to nonspecific signs and symptoms, but it causes considerable morbidity and in some cases contributes to mortality. Three primary mechanisms of hypophosphatemia exist: increased renal excretion, decreased intestinal absorption, and shifts from the extracellular to intracellular compartments. Renal hypophosphatemia can be further divided into fibroblast growth factor 23-mediated or non-fibroblast growth factor 23-mediated causes. Proper diagnosis requires a thorough medication history, family history, physical examination, and assessment of renal tubular phosphate handling to identify the cause. During the past decade, our understanding of phosphate metabolism has grown greatly through the study of rare disorders of phosphate homeostasis. Treatment of hypophosphatemia depends on the underlying disorder and requires close biochemical monitoring. This article illustrates an approach to the hypophosphatemic patient and discusses normal phosphate metabolism.

Phosphate-containing dialysis solution prevents hypophosphatemia during continuous renal replacement therapy

BACKGROUND

hypophosphatemia occurs in up to 80% of the patients during continuous renal replacement therapy (CRRT). Phosphate supplementation is time-consuming and the phosphate level might be dangerously low before normophosphatemia is re-established. This study evaluated the possibility to prevent hypophosphatemia during CRRT treatment by using a new commercially available phosphate-containing dialysis fluid.

METHODS

forty-two heterogeneous intensive care unit patients, admitted between January 2007 and July 2008, undergoing hemodiafiltration, were treated with a new Gambro dialysis solution with 1.2 mM phosphate (Phoxilium) or with standard medical treatment (Hemosol B0). The patients were divided into three groups: group 1 (n=14) receiving standard medical treatment and intravenous phosphate supplementation as required, group 2 (n=14) receiving the phosphate solution as dialysate solution and Hemosol B0 as replacement solution and group 3 (n=14) receiving the phosphate-containing solution as both dialysate and replacement solutions.

RESULTS

standard medical treatment resulted in hypophosphatemia in 11 of 14 of the patients (group 1) compared with five of 14 in the patients receiving phosphate solution as the dialysate solution and Hemosol B0 as the replacement solution (group 2). Patients treated with the phosphate-containing dialysis solution (group 3) experienced stable serum phosphate levels throughout the study. Potassium, ionized calcium, magnesium, pH, pCO(2) and bicarbonate remained unchanged throughout the study.

CONCLUSION

the new phosphate-containing replacement and dialysis solution reduces the variability of serum phosphate levels during CRRT and eliminates the incidence of hypophosphatemia.

Treatment of hypophosphatemia in the intensive care unit: a review

Introduction

Currently no evidence-based guideline exists for the approach to hypophosphatemia in critically ill patients.

Methods

We performed a narrative review of the medical literature to identify the incidence, symptoms, and treatment of hypophosphatemia in critically ill patients. Specifically, we searched for answers to the questions whether correction of hypophosphatemia is associated with improved outcome, and whether a certain treatment strategy is superior.

Results

Incidence: hypophosphatemia is frequently encountered in the intensive care unit; and critically ill patients are at increased risk for developing hypophosphatemia due to the presence of multiple causal factors. Symptoms: hypophosphatemia may lead to a multitude of symptoms, including cardiac and respiratory failure. Treatment: hypophosphatemia is generally corrected when it is symptomatic or severe. However, although multiple studies confirm the efficacy and safety of intravenous phosphate administration, it remains uncertain when and how to correct hypophosphatemia. Outcome: in some studies, hypophosphatemia was associated with higher mortality; a paucity of randomized controlled evidence exists for whether correction of hypophosphatemia improves the outcome in critically ill patients.

Conclusions

Additional studies addressing the current approach to hypophosphatemia in critically ill patients are required. Studies should focus on the association between hypophosphatemia and morbidity and/or mortality, as well as the effect of correction of this electrolyte disorder.

Isolated C-terminal tail of FGF23 alleviates hypophosphatemia by inhibiting FGF23-FGFR-Klotho complex formation

Fibroblast growth factor (FGF) 23 inhibits renal phosphate reabsorption by activating FGF receptor (FGFR) 1c in a Klotho-dependent fashion. The phosphaturic activity of FGF23 is abrogated by proteolytic cleavage at the RXXR motif that lies at the boundary between the FGF core homology domain and the 72-residue-long C-terminal tail of FGF23. Here, we show that the soluble ectodomains of FGFR1c and Klotho are sufficient to form a ternary complex with FGF23 in vitro. The C-terminal tail of FGF23 mediates binding of FGF23 to a de novo site generated at the composite FGFR1c-Klotho interface. Consistent with this finding, the isolated 72-residue-long C-terminal tail of FGF23 impairs FGF23 signaling by competing with full-length ligand for binding to the binary FGFR-Klotho complex. Injection of the FGF23 C-terminal tail peptide into healthy rats inhibits renal phosphate excretion and induces hyperphosphatemia. In a mouse model of renal phosphate wasting attributable to high FGF23, the FGF23 C-terminal peptide reduces phosphate excretion, leading to an increase in serum phosphate concentration. Our data indicate that proteolytic cleavage at the RXXR motif abrogates FGF23 activity by a dual mechanism: by removing the binding site for the binary FGFR-Klotho complex that resides in the C-terminal region of FGF23, and by generating an endogenous inhibitor of FGF23. We propose that peptides derived from the C-terminal tail of FGF23 or peptidomimetics and small-molecule organomimetics of the C-terminal tail can be used as therapeutics to treat renal phosphate wasting.

Hypophosphatemia in critically ill children: prevalence and associated risk factors

BACKGROUND

Hypophosphatemia is a disorder with potential complications and is often unrecognized in critically ill patients.

AIMS

To identify the prevalence of hypophosphatemia and risk factors associated to this disorder in critically ill children.

METHODS

In a prospective cohort study, 82 children admitted consecutively to a pediatric intensive care unit (ICU) were monitored regarding phosphorus serum levels during the first 10 days of admission. The following variables were analyzed as independent for hypophosphatemia: age, gender, diagnosis at admission, malnutrition, phosphorus intake, clinical severity score at admission (pediatric index of mortality 2) and daily scores (Pediatric Logistic Organ Dysfunction), sepsis, use of dopamine, furosemide and steroids, starvation period, and refeeding. Children with a z score of less than -2 of expected weight for age or body mass index (National Center for Health Statistics, 2000) were considered malnourished. Variables significantly associated with hypophosphatemia by bivariate analysis (p < 0.1) were included in a multiple logistic regression model.

RESULTS

The rate of hypophosphatemia was 61% during the first 10 days of pediatric ICU stay, and 12 patients developed hypophosphatemia during the study period. Malnutrition was present in 39.1% of patients, and the sera phosphorus concentration was significantly lower in malnourished than in well-nourished children (2.6 +/- 0.7 mg/dL vs. 3.5 +/- 0.8 mg/dL, p = 0.01). The multiple logistic regression model indicated the diagnosis of acute respiratory disease (odds ratio: 3.22; confidence interval: 1.03-10.1; p = 0.04), use of dopamine (odds ratio: 8.65; confidence interval: 1.58-47.3; p = 0.01), and malnutrition (odds ratio: 3.96; confidence interval: 1.19-13.3; p = 0.02) as independent risk factors for hypophosphatemia. None of the other potential risk factors discriminated for hypophosphatemia.

CONCLUSIONS

Hypophosphatemia was common in the first 10 days of ICU hospitalization and was associated with the diagnosis of respiratory disease, use of dopamine, and malnutrition. These factors should be taken into account during clinical follow up of critically ill children, especially when these conditions are found together.

Refeeding syndrome in cancer patients

BACKGROUND

Refeeding syndrome (RFS) is a common, yet underappreciated, constellation of electrolyte derangements that typically occurs in acutely ill, malnourished hospitalised patients who are administered glucose solutions or other forms of intravenous or enteral nutrition.

DISCUSSION

The hallmark of RFS is hypophosphataemia, but hypokalaemia and hypomagnesaemia are also common. Patients with various types of malignancies are at-risk for RFS, but very little exists in the oncologic literature about this disorder.

CONCLUSIONS

As RFS can have many adverse metabolic, cardiovascular, haematologic and neurologic complications, practicing oncologist needs to be aware of the pathophysiology, risk factors and clinical manifestations to promptly recognise this important, and potentially fatal, metabolic disorder.

Implementing and assessing an evidence-based electrolyte dosing order form in the medical ICU

The purpose of this study was to evaluate the efficacy, safety, and nursing acceptability of a nursing initiated, evidence-based order form to replace potassium, magnesium, and phosphate in the MICU.

METHODS

This retrospective study compared patients receiving electrolyte replacement with the order form to matched historical control patients receiving traditional electrolyte replacement (no order form). The primary outcomes were absolute change in serum concentrations and the proportion of doses achieving normal serum concentrations. Other outcomes were adverse events as documented in the medical record and nursing acceptability as assessed by survey.

RESULTS

The 2 groups (12 in each group) were similar. The order form and control groups received 36 and 62 potassium doses, 14 and 48 magnesium doses, and 34 and 13 phosphorus doses, respectively. Doses of all three electrolytes were significantly larger with the order form. Absolute changes in potassium, magnesium, and phosphorus serum concentrations for the order form group and control group were 0.36+/-0.42 versus 0.11+/-0.43 mmol/l (p<0.01), 0.56+/-0.69 versus 0.13+/-0.40 mequiv./l (p=0.07), and 0.53+/-0.82 versus 0.66+/-0.83 mg/dl (p=0.63), respectively. Normal serum concentrations achieved for each electrolyte replacement dose in the order form group and control group were 72% versus 18% (p<0.001), 86% versus 21% (p<0.001), and 47% versus 62% (p=0.57), respectively. No adverse events occurred. The nursing survey showed satisfaction and comfort using the order form.

CONCLUSIONS

The use of the order form provided greater efficiency for replacing potassium and magnesium but not phosphorus without increasing the occurrence of adverse events. The order form was well received by nursing staff.

Hypophosphatemia: clinical consequences and management

Current evidence regarding the clinical consequences of hypophosphatemia is not straightforward. Given the potentially different implications of hypophosphatemia among various patient groups, this commentary touches on patients with low serum phosphate after acute hospitalization, those with chronic ambulatory hypophosphatemia, and those with hypophosphatemia in the setting of advanced renal disease. Finally, this commentary examines the evidence regarding how best to replete phosphorous in the hypophosphatemic patient.

Hypophosphatemia in children hospitalized within an intensive care unit

The aims of this study were to estimate the occurrence of hypophosphatemia and to identify potential risk factors and outcome measures associated with this disturbance in children admitted to a pediatric intensive care unit. Data concerning 42 children admitted consecutively to 1 pediatric intensive care unit over a 1-year period were examined. Serum phosphorus levels were measured on the third day of admission, where levels below 3.8 mg/dL were considered indicative of hypophosphatemia. Hypophosphatemia was found in 32 children (76%), and there was a significant association between this disturbance and malnutrition (P = .04). Of the potential risk factors such as sepsis, diuretic/steroid therapy, starvation (over 3 days), and Pediatric Index of Mortality, none discriminated for hypophosphatemia. There were no associations between hypophosphatemia and mortality, length of stay in the pediatric intensive care unit, or time on mechanical lung ventilation. Hypophosphatemia was a common finding in critically ill children and was associated with malnutrition.

Hypophosphatemia: an evidence-based approach to its clinical consequences and management

Optimal cellular function is dependent on maintenance of a normal serum phosphorus concentration. Serum phosphorus concentration is affected by several determinants, the most important of which is regulation of phosphorus reabsorption by the kidney. The majority of this reabsorption (80%) occurs in the proximal tubule and is mediated by an isoform of the sodium-phosphate cotransporter (NaPi-II). Parathyroid hormone, via a variety of intracellular signaling cascades leading to NaPi-IIa internalization and downregulation, is the main regulator of renal phosphate reabsorption. Shift of phosphorus from extracellular to intracellular compartments, decreased gastrointestinal absorption, and increased urinary losses, are the primary mechanisms of hypophosphatemia, which affects approximately 2% of hospitalized patients. Hypophosphatemia has been implicated as a cause of rhabdomyolysis, respiratory failure, hemolysis and left ventricular dysfunction. With the exception of ventilated patients, there is little evidence that moderate hypophosphatemia has significant clinical consequences in humans, and aggressive intravenous phosphate replacement is unnecessary. By contrast, patients with severe hypophosphatemia should be treated. Intravenous repletion may be considered, especially for patients who have clinical sequelae of hypophosphatemia.

Review of the refeeding syndrome

Refeeding syndrome describes a constellation of metabolic disturbances that occur as a result of reinstitution of nutrition to patients who are starved or severely malnourished. Patients can develop fluid and electrolyte disorders, especially hypophosphatemia, along with neurologic, pulmonary, cardiac, neuromuscular, and hematologic complications. We reviewed literature on refeeding syndrome and the associated electrolyte abnormalities, fluid disturbances, and associated complications. In addition to assessing scientific literature, we also considered clinical experience and judgment in developing recommendations for prevention and treatment of refeeding syndrome. The most important steps are to identify patients at risk for developing refeeding syndrome, institute nutrition support cautiously, and correct and supplement electrolyte and vitamin deficiencies to avoid refeeding syndrome. We provide suggestions for the prevention of refeeding syndrome and suggestions for treatment of electrolyte disturbances and complications in patients who develop refeeding syndrome, according to evidence in the literature, the pathophysiology of refeeding syndrome, and clinical experience and judgment.

Treatment of electrolyte disorders in adult patients in the intensive care unit

PURPOSE

The treatment of electrolyte disorders in adult patients in the intensive care unit (ICU), including guidelines for correcting specific electrolyte disorders, is reviewed.

SUMMARY

Electrolytes are involved in many metabolic and homeostatic functions. Electrolyte disorders are common in adult patients in the ICU and have been associated with increased morbidity and mortality, as has the improper treatment of electrolyte disorders. A limited number of prospective, randomized, controlled studies have been conducted evaluating the optimal treatment of electrolyte disorders. Recommendations for treatment of electrolyte disorders in adult patients in the ICU are provided based on these studies, as well as case reports, expert opinion, and clinical experience. The etiologies of and treatments for hyponatremia hypotonic and hypernatremia (hypovolemic, isovolemic, and hypervolemic), hypokalemia and hyperkalemia, hypophosphatemia and hyperphosphatemia, hypocalcemia and hypercalcemia, and hypomagnesemia and hypermagnesemia are discussed, and equations for determining the proper dosages for adult patients in the ICU are provided. Treatment is often empirical, based on published literature, expert recommendations, and the patient's response to the initial treatment. Actual electrolyte correction requires individual adjustment based on the patient's clinical condition and response to therapy. Clinicians should be knowledgeable about electrolyte homeostasis and the underlying pathophysiology of electrolyte disorders in order to provide the optimal therapy to patients.

CONCLUSION

Treatment of electrolyte disorders is often empirical, based on published literature, expert opinion and recommendations, and patient's response to the initial treatment. Clinicians should be knowledgeable about electrolyte homeostasis and the underlying pathophysiology of electrolyte disorders to provide optimal therapy for patients.

Hypophosphatemia: an update on its etiology and treatment

Phosphate plays a key role in several biological processes. In recent years, new insights have been obtained into the regulation of the phosphate metabolism, including a growing amount of evidence suggesting that factors other than parathyroid hormone (PTH) and vitamin D are involved in maintaining the phosphate balance. A new class of phosphate-regulating factors, the so-called "phosphatonins," have been shown to be important in phosphate-wasting diseases. However, the role of the phosphatonins in the normal human homeostasis remains to be established. The incidence of hypophosphatemia in selected patient series can be more than 20%, with clinical sequelae ranging from mild to life threatening. Only when combined with phosphate depletion does hypophosphatemia become clinically significant. The factors that are involved in the phosphate homeostasis, the pathophysiology, the relevance in patient care, the clinical manifestations, and an appropriate management of phosphate depletion are discussed in this review.

Management of the Patient With Refeeding Syndrome

Refeeding syndrome is a metabolic complication that can occur when nutrition is reintroduced for patients who are severely malnourished. This syndrome can occur with any form of nutrition (oral, enteral, or parenteral), and it is fatal if not recognized and treated properly. This article discusses the body's adaptation to starvation, the pathophysiology and risk factors of refeeding syndrome, and the pharmacologic treatment of complications that threaten the lives of patients who experience this disorder. Additionally, this article discusses standards of care to ensure the early recognition of patients at risk for refeeding syndrome and the nursing considerations that can be implemented to prevent it.

Metabolic, Electrolytes, and Nutritional Concerns in Critical Illness

This article discusses metabolic, electrolyte, and nutritional concerns in critical illness.

Protocol-driven vs. physician-driven electrolyte replacement in adult critically ill patients

BACKGROUND

The intensive care unit is a dynamic environment, where high numbers of patients cared for by health care workers of different experiences and backgrounds might result in great variability in patient care. Protocol-driven interventions may facilitate timely and uniform care of common problems, like electrolyte disturbances. We prospectively compared protocol-driven (PRD) vs. physician-driven (PHD) electrolyte replacement in adult critically ill patients.

PATIENTS AND METHODS

In the first month of the two-month study, potassium, magnesium, and phosphate levels were checked by a physician before ordering replacement (PHD replacement period). Over the second month, ICU nurses proceeded with replacement according to the protocol (PRD replacement period). We collected demographic data, admission diagnosis, number of potassium, magnesium, and phosphate levels done per day, number of low levels per day, number of replacements per day, time between availability of results to ordering replacement, time to starting replacement, post-replacement levels, serum creatinine, replacement dose, arrhythmias and replacement route.

RESULTS

During the PHD replacement period, 43 patients meeting the inclusion criteria were admitted to the ICU, while 44 were admitted during the PRD month. The mean time (minutes) from identifying results to replacement of potassium, phosphate and magnesium was significantly longer with PHD replacement compared with PRD replacement (161, 187, and 189 minutes vs. 19, 26, and 19 minutes) (P<0.0001). The number of replacements needed and not given was also significantly lower in the PRD replacement period compared with the PHD replacement period (2, 4, and 0 compared with 9, 6 and 0) (P<0.05). No patients had high post-replacement serum concentrations of potassium, phosphate or magnesium.

CONCLUSIONS

This study shows that a protocol-driven replacement strategy for potassium, magnesium and phosphate is more efficient and as safe as a physician-driven replacement strategy.

Phosphate addition to hemodiafiltration solutions during continuous renal replacement therapy

OBJECTIVE

Hypophosphatemia often occurs during continuous renal replacement therapy (CRRT). The addition of phosphate to dialysate and replacement solutions facilitates phosphate handling, but the risk of precipitation with calcium within these solutions has not been addressed.

DESIGN AND SETTING

Experimental study with a retrospective observational study in a medico-surgical intensive care unit.

METHODS AND PATIENTS

We tested the addition of phosphate to calcium-rich lactate- and bicarbonate-based solutions (Hemosol LG2 and Hemosol B0) used in CRRT to see whether precipitation occurs. Two milliliters of potassium phosphate added to 5-l bags gives a physiological phosphate concentration of 1.2 mmol/l. In addition, calcium and phosphate homeostasis was retrospectively evaluated in 20 consecutive CRRT patients where potassium phosphate had been added to these solutions.

MEASUREMENTS AND RESULTS

Total and ionized calcium, phosphate, pH, PCO(2) and bicarbonate remained essentially unchanged 5 h after the addition of 2 ml of potassium phosphate to 5-l Hemosol solutions. Visual inspection did not reveal any precipitate. Of the 20 patients studied, 14 received more than 24 h of phosphate supplementation to dialysate and replacement solutions. Phosphate remained stable throughout CRRT despite phosphate intake from nutrition in 11 cases. No adverse event was noted on potassium, calcium, pH and bicarbonate homeostasis.

CONCLUSIONS

The addition of phosphate to Hemosol solutions does not precipitate with the calcium within these solutions. This practical method effectively prevents hypophosphatemia in CRRT patients.

Refeeding syndrome in patients with gastrointestinal fistula

OBJECTIVE

Although refeeding syndrome has been well documented in starved patients, obese patients, those with anorexia nervosa, malnourished elderly individuals, and certain postoperative patients, little is known about the presence and the importance of refeeding syndrome in patients with gastrointestinal fistula and insufficient nutrition support over the long term. The objective of this study was to estimate the morbidity of this syndrome in these patients, to assess the safety and efficacy of our graduated refeeding regimen, and to emphasize the importance of this syndrome.

METHODS

One hundred fifty-eight patients with gastrointestinal fistula during the past 2 y were reviewed.

RESULTS

Fifteen of these patients were diagnosed as having refeeding syndrome. They were started on the refeeding procedure according to our regimen, and changes in their serum levels of electrolytes were recorded. The symptoms and signs they presented were noted. All patients were successfully advanced to full nutrition support. During the refeeding procedure, patients presented with weakness, paralysis of limbs, slight dyspnea, paresthesia, tachycardia, edema, and diarrhea. Serum phosphorus concentration decreased in all patients within 24 h of refeeding, reaching a mean nadir after 3.3 +/- 1.5 d and another 6.1 +/- 2.1 d to return to above 0.70 mM/L upon phosphorus supplementation. Three patients treated with growth hormone presented more severe hypophosphatemia (<0.20 mM/L) than the others.

CONCLUSIONS

1) Refeeding syndrome occurs commonly in patients with malnutrition secondary to gastrointestinal fistula. 2) Alterations in phosphate metabolism are central to the refeeding syndrome. 3) Supplementation with electrolytes (including especially phosphate) and vitamins is the focal point of the treatment of this syndrome. 4) Growth hormone treatment may aggravate hypophosphatemia.

Treatment of hypophosphatemia using a protocol based on patient weight and serum phosphorus level in a surgical intensive care unit

BACKGROUND

Hypophosphatemia may cause organ derangements in the surgical intensive care unit. The purpose of this study was to determine the impact of a repletion protocol for hypophosphatemia based on admission weight and phosphorus level.

STUDY DESIGN

All patients who presented to an 18-bed surgical intensive care unit with a serum phosphorus level of 2.2 mg/dL or less or who received phosphorus supplementation despite having normal levels were identified. In the preintervention phase between January and June 2001, 137 patients were retrospectively identified who met these criteria. A protocol was then designed giving a single intravenous dose of phosphorus based on weight and serum phosphorus. Repletion was given with sodium or potassium phosphorus based on presupplementation levels. After protocol implementation 141 patients met these criteria between September 2001 and February 2002, and treatment and postrepletion levels were followed prospectively.

RESULTS

A total of 47 patients were repleted before the intervention with adequate followup and 22 (47%) attained a normal level. Supplementation success was 53% in moderate hypophosphatemia (2.2 mg/dL or less) and 27% in severe hypophosphatemia (less than 1.5 mg/dL). After protocol implementation, 111 patients were repleted with 84 (76%) correcting to a normal level (p = 0.002 compared with retrospective patients). Success was 78% in moderate hypophosphatemia and 62% in severe hypophosphatemia. Inappropriate supplementation of normal phosphorus levels decreased from 51 to 16 patients after protocol implementation.

CONCLUSIONS

A protocol based on weight and serum levels successfully treated both moderate and severe hypophosphatemia in the majority of critically ill patients. Protocol implementation also decreased unnecessary supplementation of normal phosphorus levels.

Refeeding Syndrome

Patients admitted to inpatient rehabilitation units commonly have underlying medical disorders and are at risk for poor oral intake and malnutrition, which may be compounded by dysphagia and anorexia. The refeeding syndrome is an underappreciated but clinically important entity characterized by acute electrolyte abnormalities, fluid retention, and dysfunction of various organ systems, which can result in significant morbidity and, occasionally, death. Reinstitution of nutrition by any route in a undernourished patient may lead to acute electrolyte shifts and fluid retention, which are hallmarks of the refeeding syndrome. As such, this article briefly summarizes the clinical manifestations and treatment of refeeding syndrome as it relates to patients admitted to the inpatient rehabilitation unit.

Hypophosphatemia in critically ill children

The purpose of this paper is to review clinical studies on hypophosphatemia in pediatric intensive care unit patients with a view to verifying prevalence and risk factors associated with this disorder. We searched the computerized bibliographic databases Medline, Embase, Cochrane Library, and LILACS to identify eligible studies. Search terms included critically ill, pediatric intensive care, trauma, sepsis, infectious diseases, malnutrition, inflammatory response, surgery, starvation, respiratory failure, diuretic, steroid, antiacid therapy, mechanical ventilation. The search period covered those clinical trials published from January 1990 to January 2004. Studies concerning endocrinological disorders, genetic syndromes, rickets, renal diseases, anorexia nervosa, alcohol abuse, and prematurity were not included in this review. Out of 27 studies retrieved, only 8 involved pediatric patients, and most of these were case reports. One clinical trial and one retrospective study were identified. The prevalence of hypophosphatemia exceeded 50%. The commonly associated factors in most patients with hypophosphatemia were refeeding syndrome, malnutrition, sepsis, trauma, and diuretic and steroid therapy. Given the high prevalence, clinical manifestations, and multiple risk factors, the early identification of this disorder in critically ill children is crucial for adequate replacement therapy and also to avoid complications.

Serum phosphate abnormalities in the emergency department

Abnormalities in serum phosphate levels are more prevalent in certain subsets of Emergency Department patients than in the general population. Patients with diabetic ketoacidosis, chronic obstructive pulmonary disease, alcoholism, malignancy, and renal failure are at increased risk. Multiple factors, including nutritional intake, medications, renal or intestinal excretion, and cellular redistribution, are potential etiologies. The clinical manifestations of mild hypophosphatemia or hyperphosphatemia are typically minor and nonspecific (myalgias, weakness, anorexia). When the imbalance is severe, critical complications may occur (tetany, seizures, coma, rhabdomyolysis, respiratory failure, ventricular tachycardia). Mild asymptomatic hypophosphatemia can be treated with oral phosphate supplementation (15 mg/kg daily) on an outpatient basis. Patients with severe or symptomatic hypophosphatemia should be treated with IV phosphate therapy (0.08-0.16 mg/kg over 6 h) and admitted for monitoring and subsequent serum electrolyte testing. Mild asymptomatic hyperphosphatemia is commonly managed in renal failure by limiting dietary intake and reducing absorption with phosphate-binding salts. Hemodialysis may be required for severe hyperphosphatemia with symptomatic hypocalcemia.

Endocrine and metabolic issues in the management of the chronically critically ill patient

The metabolic syndrome of chronic critical illness (CCI) consists of multisystem organ dysfunction resulting from the initial acute injury and chronic immune-neuroendocrine axis activation, adult kwashiorkor-like malnutrition, and prolonged immobilization with suppression of the PTH-vitamin D axis and hyper-resorptive metabolic bone disease. CCI patients can also present unique challenges in the management of diabetes mellitus, thyroid and adrenal diseases, electrolyte abnormalities and hypogonadism.

Anions and the anaesthetist

Anions are the negative components of most chemical structures and play many important physiological and pharmacological roles that are of interest to the anaesthetist. Their relevance is reviewed with a particular emphasis on the inorganic anions (halides, bicarbonate, phosphate and sulphate) and the significance and limitations of the anion gap. Organic anions (albumin, lactate) are also discussed, albeit briefly. The suitability of anions for their role in neurotransmission and acid-base balance is outlined.

Hypophosphatemia in acute-phase response syndrome patients. Preliminary data

BACKGROUND

Hypophosphatemia is common in acutely ill patients and possibly may occur in the acute-phase response syndrome (APR), secondary to hyperglycemia and shifts of extracellular phosphorus into cells.

AIM

To compare the frequency of hypophosphatemia in patients with or without APR.

METHODS

All plasma phosphorus results (n = 822) corresponding to a 6-month period were searched using an university hospital mainframe. Relevant laboratory and clinical details were also registered. All cases of alcohol withdrawal, diabetic ketoacidosis, parenteral nutrition, and chronic respiratory alkalosis and patients receiving antacids or intravenous dextrose (5%) in water at a rate higher than 50 g glucose/day were excluded. APR was defined on the basis of severe trauma or infection and at least two of the following: fever, leukopenia (WBC <5,000/mm3), or leukocytosis (WBC >9,000/mm3). Hypophosphatemia was defined as a serum phosphorus concentration <2.0 mg/dl.

RESULTS

A total of 227 patients were studied. Thirty-five (15.4%) patients fulfilled the criteria for APR. Hypophosphatemia was observed in 11.4% of the APR-positive patients, in contrast to 0.5% in the APR-negative group. Hyperglycemia was more common in APR-positive patients (60.0 vs. 36. 8%).

CONCLUSION

Our results suggest that hypophosphatemia may be attributed to increased serum glucose levels secondary to tissue injury and infection in APR-positive patients.

Severe hypophosphatemia. Pathophysiologic implications, clinical presentations, and treatment

We conducted this review to heighten the awareness and describe pathologic manifestations of hypophosphatemia. We present 3 cases of varied manifestations of hypophosphatemia where recognition was delayed. In certain settings, severe hypophosphatemia has significant morbidity and potential mortality. Appreciation of the pathophysiologic basis for organ dysfunction in severe hypophosphatemia should result in early recognition and treatment. We reviewed the English-language literature for reported cases and research studies dealing with pathophysiologic mechanisms subserving clinical manifestations. We observed that depletion of adenosine triphosphate (ATP) would explain most of the derangement noted in cellular functions. Phosphate plays a key role in the delivery of oxygen to the tissue. Lack of phosphate, therefore, leads to tissue hypoxia and hence disruption of cellular function. Severe hypophosphatemia becomes clinically significant when there is underlying phosphate depletion. Otherwise, short-term acute hypophosphatemia is not usually associated with any specific disorder. Chronic hypophosphatemia, on the other hand, results in hematologic, neuromuscular, and cardiovascular dysfunction, and unless corrected, the consequences can be grave. Most of the time hypophosphatemia results from renal loss of phosphate, diagnosed by a fractional secretion of phosphate > 5%. It is hard to provide precise estimates of how many patients are seen with hypophosphatemia annually at academic medical centers. This is complicated by use of chemistry panels that do not measure inorganic phosphate unless specifically ordered. This often leads to delay in correct diagnosis, and, therefore, additional delay in providing appropriate management. A high index of suspicion alone avoids the unnecessary withholding of treatment that can be life saving.