Drug- and nutrition-induced hypophosphatemia: mechanisms and relevance in the critically ill

Association of Hypophosphatemia during Continuous Kidney Replacement Therapy and Clinical Outcomes: A Systematic Review and Meta-Analysis

INTRODUCTION

Hypophosphatemia is a common and potentially severe complication of continuous kidney replacement therapy (CKRT), but the evidence on the correlation between hypophosphatemia occurring during CKRT and clinical outcomes remains limited.

METHODS

Electronic databases (PubMed, Embase, Web of Science, and the Cochrane database) were searched from inception to March 1, 2024. All possible studies that examined the following outcomes were included: all-cause mortality, mechanical ventilation, intensive care unit (ICU) stay, and CKRT duration.

RESULTS

A total of 8,631 patients from eight cohort studies were included. There was no statistical association between hypophosphatemia during CKRT and all-cause mortality in critically ill patients (OR 0.82, 95% CI 0.57-1.18, p = 0.28, I2 = 83%). However, hypophosphatemia was associated with longer duration of mechanical ventilation (WMD 80.30 h, 95% CI 31.37-129.22, p = 0.001, I2 = 60%). Furthermore, a longer length of ICU stay (WMD 2.76 d, 95% CI 2.50-3.02, p < 0.00001, I2 = 36%) and CKRT duration (WMD 51.51 h, 95% CI 2.69-100.34, p = 0.04, I2 = 96%) were observed in patients with hypophosphatemia.

CONCLUSIONS

The association between hypophosphatemia and mortality in patients receiving CKRT was insufficient. However, hypophosphatemia during CKRT might be associated with adverse clinical outcomes for critically ill patients.

Assessment of drug-induced electrolyte disorders in intensive care units: a multicenter observational study

Objective

Electrolyte disorder (ED) is frequently encountered critically ill patients during admission or admission to the intensive care unit (ICU). This study aimed to determine the frequency of ED encountered in ICU patients to evaluate the relationship of ED with drugs.

Methods

This prospective, multicenter study was conducted in the medical and anesthesiology ICUs of two training and research hospitals and included patients with at least one ED during admission or hospitalization in the ICUs. The relationship between ED and the drug was evaluated by calculating the logistic probabilistic method scale (LPMS) and the expert panel's evaluation. The correlation between EDs and LPMS was determined using Kendal tau. A binary logistic regression model was preferred in the analysis of factors related to ED. Statistical significance was set as p < 0.05.

Results

A total of 117 patients were included in the study. A total of 165 EDs were detected, including at least one in 88 (75.2%) patients. According to the expert panel, 61 (21.7%) of EDs were drug-related, whereas according to the LPMS, 111 (39.6%) (p < 0.001). Mortality (50% vs. 13.7%) and mechanical ventilation rates (52.2% vs. 17.2%) were significantly higher in patients with ED (p < 0.001). Patients with ED had 8.352 times higher odds of exhibiting mortality (OR: 8.352, %95 CI: 1.598-43.648, p: 0.012) and need mechanical ventilation with higher odds of 3.229 (OR: 3.229 95% CI: 0.815-12.787 p: 0.045). Patient who required enteral or parenteral feeding were associated with an increased likelihood of exhibiting ED (respectively OR: 30.057, %95 CI: 2.265-398.892, p: 0.01, OR: 5.537, %95 CI: 1.406-21.800, p: 0.014).

Conclusion

EDs are very common in the ICU. Dysnatremia was detected more commonly in other EDs. It has also been found that patients with ED are more often under mechanical ventilation, have more prolonged hospitalizations, and have higher mortality rates than patients without ED. The suitability of LPMS for assessing ED-drug relationships in the ICU context is questioned.

The Causes of Hypo- and Hyperphosphatemia in Humans

Phosphate homeostasis involves several major organs that are the skeleton, the intestine, the kidney, and parathyroid glands. Major regulators of phosphate homeostasis are parathormone, fibroblast growth factor 23, 1,25-dihydroxyvitamin D, which respond to variations of serum phosphate levels and act to increase or decrease intestinal absorption and renal tubular reabsorption, through the modulation of expression of transcellular transporters at the intestinal and/or renal tubular level. Any acquired or genetic dysfunction in these major organs or regulators may induce hypo- or hyperphosphatemia. The causes of hypo- and hyperphosphatemia are numerous. This review develops the main causes of acquired and genetic hypo- and hyperphosphatemia.

Phosphate replacement in the critically ill: potential implications for military patients

BACKGROUND

Severe hypophosphataemia in the intensive care unit (ICU) setting has been widely associated with adverse clinical outcomes across multiple organ systems, as well as increased mortality. However, the clinical significance of mild or moderate hypophosphataemia remains uncertain. This can lead to heterogeneous phosphate replacement protocols across different institutions. The aim of this study was to assess the significance of mild and moderate hypophosphataemia on clinical outcomes across several organ systems.

METHOD

All patients over a 3-week period in our ICU were retrospectively analysed with admission serum phosphate compared with subsequent clinical outcomes after admission. Low serum phosphate (0.3-1.0 mmol/L), according to local protocol, was compared with normal serum phosphate (>1.0 mmol/L).

RESULTS

Of the 72 patients admitted to intensive therapy unit during this period, 14/72 (19%) had phosphate levels deemed low (<1.0 mmol/L) and received phosphate supplementation. No significant difference was found between groups in terms of cardiac arrhythmias (p=0.55), capillary blood glucose (p=0.08) and serum lactate (p=0.32). Low phosphate (0.3-1.0 mmol/L) was not associated with increased likelihood of requiring ventilation. Platelet count was significantly lower in the low phosphate group (p=0.008).

CONCLUSION

In our study, mild and moderate hypophosphataemia was not associated with adverse clinical outcome across most organ systems analysed. Given the current evidence and results of this study, we would suggest that there is a trend towards over-replacement of phosphate, representing a potential clinical safety issue as well as clear financial implications.

Hypophosphatemia after nontraumatic intracranial hemorrhage

BACKGROUND

The aim of this study was to assess the incidence and contributing factors of hypophosphatemia and the association with poor long-term outcome after nontraumatic intracranial hemorrhage.

METHODS

This was a prospective, observational study of patients with nontraumatic intracranial hemorrhage (i.e., aneurysmal or perimesencephalic subarachnoid hemorrhage, or spontaneous intracerebral or intraventricular hemorrhage) treated in the intensive care unit (ICU) at our university hospital. Plasma phosphate concentrations were measured serially in 2-day sections during the 6 day study period. The ICU mortality was recorded, 3-month and 1-year outcomes were assessed using the Glasgow Outcome Scale.

RESULTS

One hundred patients were enrolled. The frequency of hypophosphatemia (Pi ≤ 0.65 mmol/l) was 70%. Chronic hypertension, acute hydrocephalus, and diffuse brain edema were more common in patients with hypophosphatemia compared with normophosphatemics (44% vs. 21%, P = 0.021; 59% vs. 33%, P = 0.021; and 43% vs. 13%, P = 0.004, respectively). Hypophosphatemic patients had higher maximum SOFA scores [10 (7-11) vs. 7.5 (5.75-10), P = 0.024]. Initial phosphate concentration correlated inversely with APACHE II score on admission (ρ = -0.304, P = 0.002) and SOFA score on the first ICU day (ρ = -0.269, P = 0.008). There was no difference in outcome between hypophosphatemic and normophosphatemic patients. In all five patients with severe hypophosphatemia (Pi < 0.32 mmol/l) the functional outcome was good.

CONCLUSION

Hypophosphatemia was common in this patient population. The outcome was similar between hypophosphatemic and normophosphatemic patients. Chronic hypertension, acute hydrocephalus, diffuse brain edema and higher SOFA scores were more common in patients with hypophosphatemia.

Calcium and Phosphorous in Pediatric Parenteral Nutrition

Calcium (Ca) and phosphorus (P) are essential for various systemic functions, including bone mineralization. Adequate provision of Ca and P in pediatric parenteral nutrition (PN) solutions is necessary for skeletal growth and for the prevention of metabolic bone disease. The provision of adequate doses of Ca and P in pediatric PN solutions is complicated by the increased needs in preterm and term infants, solubility limitations, and venous access. Clinicians should be aware of the evidence that supports the optimal use of Ca and P in pediatric PN solutions, including studies that have evaluated dosing and solubility. The aim of this article is to review relevant literature and practices for the use of these two minerals in pediatric PN solutions. The vitamin D endocrine system, a critical component for Ca homeostasis and bone mineralization, is discussed, as well as clinical manifestations of metabolic bone disease and methods for its prevention, assessment, and treatment in pediatric patients receiving PN.

Bone and kidney toxicity induced by nucleotide analogues in patients affected by HBV-related chronic hepatitis: a longitudinal study

OBJECTIVES

Nucleotide analogues may promote renal and bone toxicity. The aim of the present study was to evaluate markers of osteorenal toxicity in patients affected by hepatitis B virus-related chronic hepatitis treated with lamivudine plus adefovir who were switched to tenofovir.

PATIENTS AND METHODS

We evaluated 60 consecutive patients at the time of the switch of treatment and after 1, 3, 6, 9 and 12 months. The mean baseline estimated glomerular filtration rate (eGFR) was 89.3 ± 19.0 mL/min/1.73 m(2).

RESULTS

During the study period we observed a reduction in mean eGFR up to 6 months after switching to tenofovir, and this remained stable for the last two timepoints. At the end of study, the mean eGFR was 82.6 ± 21.5 mL/min/1.73 m(2), a reduction of 7.5%. The mean baseline proteinuria was 202.6 ± 237.6 mg/24 h. Microhaematuria was observed in 22.6% of patients and hypophosphataemia in 18.6%. After 1 month of tenofovir, we observed a worsening of serum phosphate and parathyroid hormone levels, haemoglobinuria and 24 h proteinuria. After 3 and 12 months of tenofovir, these data tended to recover to baseline levels. A total of 92.6% of patients at baseline had hypovitaminosis D. After supplementation with cholecalciferol, this percentage decreased significantly. We observed a reduced bone mineral density (BMD) in 52.7% of patients at baseline; this increased to 77.8% after 6 months of tenofovir, but at the last timepoint the percentage of patients with a reduced BMD had fallen to a level above the baseline.

CONCLUSIONS

In conclusion, patients exposed to lamivudine plus adefovir showed relevant osteorenal damage. The switch to tenofovir provoked a slight reduction in eGFR that stabilized after 6 months. The reduced BMD at baseline did not worsen under tenofovir treatment.

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 and its clinical implications in critically ill children: a retrospective study

PURPOSE

The aims of this study were to determine the prevalence of hypophosphatemia and to discuss the clinical implications of hypophosphatemia in critically ill children.

MATERIALS AND METHODS

A retrospective review of the medical records of children admitted to the pediatric intensive care unit from December 2006 to December 2007 was conducted.

RESULTS

In 60.2% (n = 71) of the patients, any serum phosphorous level at admission and at the third day or seventh day after admission to pediatric intensive care unit was in hypophosphatemic range. Sepsis was present in 22.9% (n = 27) of the children studied and was associated with hypophosphatemia (P = .02). Hypophosphatemia was also associated with use of furosemide (P = .04), use of steroid (P = .04), use of β(2) agonist (P = .026), and use of an H(2) blocker (P = .004). There was a significant association between hypophosphatemia and the rate to attain target caloric requirements by enteral route (P = .007). The median time to attain target caloric requirements by enteral route was 2.9 ± 1.9 (0.2-10) days in the normophosphatemic group and 4.4 ± 2.8 (0.3-12) days in the hypophosphatemic group. In the multiple regression model, solely the rate to attain the target caloric requirements by enteral route demonstrated independent association with hypophosphatemia (P = .006; β = .27; 95% confidence interval, 0.02-0.09). Significant association was found between hypophosphatemia and the duration of mechanical ventilation and between hypophosphatemia and pediatric intensive care unit length of stay (P = .02 and P = .001, respectively).

CONCLUSIONS

Critically ill pediatric patients are prone to hypophosphatemia, especially if they cannot be fed early by enteral route. Hypophosphatemia is associated with an increased duration of mechanical ventilation and increased length of stay in the pediatric intensive care unit, suggesting that active repletion might improve these parameters.

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.

Electrolyte disturbances associated with commonly prescribed medications in the intensive care unit

Electrolyte imbalances are common in critically ill patients. Although multiple disease states typically encountered in the intensive care unit may be responsible for the development of electrolyte disorders, medications may contribute to these disturbances as well. Medications can interfere with the absorption of electrolytes, alter hormonal responses affecting homeostasis, as well as directly impact organ function responsible for maintaining electrolyte balance. The focus on this review is to identify commonly prescribed medications in the intensive care unit and potential electrolyte disturbances that may occur as a result of their use. This review will also discuss the postulated mechanisms associated with these drug-induced disorders. The specific drug-induced electrolyte disorders discussed in this review involve abnormalities in sodium, potassium, calcium, phosphate, and magnesium. Clinicians encountering electrolyte disturbances should be vigilant in monitoring the patient's medications as a potential etiology. Insight into these drug-induced disorders should allow the clinician to provide optimal medical management for the critically ill patient, thus improving overall healthcare outcomes.

A multidisciplinary protocol improves electrolyte replacement and its effectiveness

BACKGROUND

We implemented a multidisciplinary electrolyte replacement protocol in a tertiary referral center surgical intensive care unit. The purpose of this study was to evaluate its efficacy.

METHODS

This was a retrospective study. The electrolyte replacement protocol was designed for the replacement of potassium, magnesium, and phosphorous and was nurse driven. Data evaluated included patient demographics and details specific to electrolyte replacement. Univariate analyses were performed by using the Student t test and the Fisher exact test. A P value of <.05 was considered significant.

RESULTS

After implementation of the protocol, overall electrolyte replacement improved from 70% to 79% (P = .03), and its overall effectiveness increased from 50% to 65% (P = .01). Individual electrolyte replacement, effectiveness, and dosing varied.

CONCLUSIONS

The implementation of a multidisciplinary electrolyte replacement protocol in a tertiary referral center surgical intensive care unit significantly improved both overall electrolyte replacement and its effectiveness.

Predisposing chronic diseases and hypophosphatemia in patients with influenza

Almost half of the hospitalized influenza patients have a chronic disease, which increases the risk for secondary bacterial infections and for adults >65 years influenza is related to high mortality risk. The impact of diabetes mellitus (DM), asthma bronchiale, cardiovascular disease (CVD) and chronic obstructive pulmonary disease (COPD) on the risk of having a low serum phosphatemia (S-P) in addition to influenza is important to investigate as this increases both morbidity and mortality and can be prevented. Hypophosphatemia could be the explanation for reduced chemo-taxis and phagocytosis, which in addition to respiratory function may increase the risk of pneumonia and sepsis. Data for this study was collected from the medical journals retrospectively for 100 patients admitted to the Department of Infectious Diseases during the study period, 1992-94, with the clinical diagnosis influenza out of which seventy-two cases were used in the calculation. Forty-seven percent of the hospitalized influenza patients had a 2.7-fold risk of suffering from DM than of any other chronic disease and an almost significantly doubled risk of having a low S-P level with a chronic disease. The prevalence of hypophosphatemia (S-P<0.70 mmol/l) was high; 13.0% of the women and 15.0% of the men; 34.0% of all patients had S-P<0.82 mmol/l. Men, in contrast to women, showed clinical signs of a secondary bacterial infection more frequently (12/41 and 6/35, respectively). Our study gives indications for an involvement of low S-P with chronic disease.

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.

Potassium and phosphorus repletion in hospitalized patients: implications for clinical practice and the potential use of healthcare information technology to improve prescribing and patient safety

OBJECTIVES

Evaluate potassium and phosphorus repletion in hospitalized patients. Assess the potential role for use of various methods, including healthcare information technology, to improve prescribing and patient safety.

RESEARCH DESIGN AND METHODS

Inpatient medication profiles were screened to identify orders for potassium and phosphorus replacement products. Electronic laboratory and medical records were used to evaluate efficacy and safety. Eligibility for oral therapy was defined by the presence of other scheduled oral medications on the medication profile. Appropriateness of prescribing was based on adherence to the hospital guidelines for repletion.

RESULTS

Overall, 134 orders for potassium in 92 patients and 36 orders for phosphorus in 27 patients were evaluated over a 3-week data collection period. Intravenous (IV) potassium was prescribed in 73% of replacement episodes (46% as single doses and 54% within large volume IV fluids), with 85% for normokalemia or mild-to-moderate cases of hypokalemia. Phosphorus orders involved single doses of IV potassium phosphate (mean 13.1 mmol) in 75% of cases. Approximately 85% of doses were for mild or moderate hypophosphatemia. Eligibility for oral therapy was evident in 74% of normokalemic or mild hypokalemic cases receiving IV potassium products and in 33% of cases receiving IV phosphorus replacement. Six cases of mild hyperkalemia were observed. No hyperphosphatemia was documented. Study limitations include use of a retrospective design, inability to discern whether some electrolyte doses were given with a preventative intent, potential overestimation of the number of patients eligible for oral repletion, and lack of data on the accessibility of the laboratory serum concentrations or the awareness of serum values to the prescribers.

CONCLUSIONS

Intravenous potassium and phosphate products are commonly prescribed for mild or moderate cases of hypokalemia or hypophosphatemia. Many patients met eligibility for oral therapy. Efforts to enhance prescriber education and implement computerized prescribing and decision support systems have the potential to improve prescribing and reduce possibilities of adverse drug events and medication errors related to potassium and phosphate administration.

Metabolic, Electrolytes, and Nutritional Concerns in Critical Illness

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

Severe electrolyte disorders following cardiac surgery: a prospective controlled observational study

Introduction

Electrolyte disorders are an important cause of ventricular and supraventricular arrhythmias as well as various other complications in the intensive care unit. Patients undergoing cardiac surgery are at risk for development of tachyarrhythmias, especially in the period during and immediately after surgical intervention. Preventing electrolyte disorders is thus an important goal of therapy in such patients. However, although levels of potassium are usually measured regularly in these patients, other electrolytes such as magnesium, phosphate and calcium are measured far less frequently. We hypothesized that patients undergoing cardiac surgical procedures might be at risk for electrolyte depletion, and we therefore conducted the present study to assess electrolyte levels in such patients.

Methods

Levels of magnesium, phosphate, potassium, calcium and sodium were measured in 500 consecutive patients undergoing various cardiac surgical procedures who required extracorporeal circulation (group 1). A total of 250 patients admitted to the intensive care unit following other major surgical procedures served as control individuals (group 2). Urine electrolyte excretion was measured in a subgroup of 50 patients in both groups.

Results

All cardiac patients received 1 l cardioplegia solution containing 16 mmol potassium and 16 mmol magnesium. In addition, intravenous potassium supplementation was greater in cardiac surgery patients (mean ± standard error: 10.2 ± 4.8 mmol/hour in cardiac surgery patients versus 1.3 ± 1.0 in control individuals; P < 0.01), and most (76% versus 2%; P < 0.01) received one or more doses of magnesium (on average 2.1 g) for clinical reasons, mostly intraoperative arrhythmia. Despite these differences in supplementation, electrolyte levels decreased significantly in cardiac surgery patients, most of whom (88% of cardiac surgery patients versus 20% of control individuals; P < 0.001) met criteria for clinical deficiency in one or more electrolytes. Electrolyte levels were as follows (mmol/l [mean ± standard error]; cardiac patients versus control individuals): phosphate 0.43 ± 0.22 versus 0.92 ± 0.32 (P < 0.001); magnesium 0.62 ± 0.24 versus 0.95 ± 0.27 (P < 0.001); calcium 1.96 ± 0.41 versus 2.12 ± 0.33 (P < 0.001); and potassium 3.6 ± 0.70 versus 3.9 ± 0.63 (P < 0.01). Magnesium levels in patients who had not received supplementation were 0.47 ± 0.16 mmol/l in group 1 and 0.95 ± 0.26 mmol/l in group 2 (P < 0.001). Urinary excretion of potassium, magnesium and phosphate was high in group 1 (data not shown), but this alone could not completely account for the observed electrolyte depletion.

Conclusion

Patients undergoing cardiac surgery with extracorporeal circulation are at high risk for electrolyte depletion, despite supplementation of some electrolytes, such as potassium. The probable mechanism is a combination of increased urinary excretion and intracellular shift induced by a combination of extracorporeal circulation and decreased body temperature during surgery (hypothermia induced diuresis). Our findings may partly explain the high risk of tachyarrhythmia in patients who have undergone cardiac surgery. Prophylactic supplementation of potassium, magnesium and phosphate should be seriously considered in all patients undergoing cardiac surgical procedures, both during surgery and in the immediate postoperative period. Levels of these electrolytes should be monitored frequently in such patients.

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.

Metabolic Bone Disease After Chronic Antacid Administration in an Infant

OBJECTIVE

To describe a case of hypophosphatemia and metabolic bone disease (MBD) due to aluminum-containing antacids.

CASE SUMMARY

An 8-month-old white boy was brought to the emergency department due to irritability and pain with movement. Upon examination, the infant was irritable, unable to bear weight, had palpable clavicular bony lesions, point tenderness of the hips, and poor head control. The infant had lost several developmental milestones over the past 4 months (eg, ability to roll over) and had decreased appetite and minimal weight gain. Skeletal survey revealed multiple rib fractures, osteoporosis, and Ricketts. Hypophosphatemia (2.3 mg/dL; normal 3.2–6.3) and an elevated serum aluminum level (14 μg/L, normal 0–9) were noted. Past medical history was positive for gastroesophageal reflux. He had been started on ranitidine and aluminum hydroxide (1/2 teaspoonful per 6-ounce bottle) at 2 months of age. The infant's formula contained elevated aluminum levels. Further investigation showed that 1/2 tablespoonful instead of 1/2 teaspoonful of antacid had been added to each 6-ounce formula bottle for the prior 6 months; only 1 month of antacid therapy had been recommended. An objective causality assessment revealed a probable adverse drug event.

DISCUSSION

Phosphate-binding substances such as aluminum-containing antacids can bind large amounts of phosphorus, causing hypophosphatemia and MBD.

CONCLUSIONS

We report this case to increase awareness of the risk of hypophosphatemia and MBD (likely aluminum related) with use of over-the-counter aluminum-containing antacids in pediatrics, as well as the hazards of prescribing doses in “spoonful” units.

Hypophosphatemia and hypomagnesemia induced by cooling in patients with severe head injury

OBJECT

Induced hypothermia in patients with severe head injury may prevent additional brain injury and improve outcome. However, this treatment is associated with severe side effects, including life-threatening cardiac tachyarrhythmias. The authors hypothesized that these arrhythmias might be caused by electrolyte disorders and therefore studied the effects of induced hypothermia on urine production and electrolyte levels in patients with severe head injury.

METHODS

Urine production, urine electrolyte excretion, and plasma levels of Mg, phosphate, K, Ca, and Na were measured in 41 patients with severe head injury. Twenty-one patients (Group I, study group) were treated using induced hypothermia and pentobarbital administration, and 20 patients (Group 2, controls) were treated with pentobarbital administration alone. In Group 1, Mg levels decreased from 0.98+/-0.15 to 0.58+/-0.13 mmol/L (mean +/- standard deviation; p < 0.01), phosphate levels from 1.09+/-0.19 to 0.51+/-0.18 mmol/L (p < 0.01), Ca levels from 2.13+/-0.25 to 1.94+/-0.14 mmol/L (p < 0.01), and K levels from 4.2+/-0.59 to 3.6+/-0.7 mmol/L (p < 0.01) during the first 6 hours of cooling. Electrolyte levels in the control Group 2 remained unchanged. Electrolyte depletion in Group I occurred despite the fact that moderate and, in some cases, substantial doses of electrolyte supplementation were given to many patients, and supplementation doses were often increased during the cooling period. Average urine production increased during the cooling period, from 219+/-70 to 485+/-209 ml/hour. When the targeted core temperature of 32 micro C was reached, urine production returned to levels that approximated precooling levels (241+/-102 ml/hour). Electrolyte levels rose in response to high-dose supplementation. In the control group, urine production and electrolyte excretion remained unchanged throughout the study period.

CONCLUSIONS

Induced hypothermia is associated with severe electrolyte depletion, which is at least partly due to increased urinary excretion through hypothermia-induced polyuria. This may be the mechanism through which induced hypothermia can lead to arrhythmias. When using this promising new treatment in patients with severe head injury, stroke, or postanoxic coma following cardiopulmonary resuscitation, prophylactic electrolyte supplementation should be considered and electrolyte levels should be monitored frequently.

Hypophosphataemia: cause of the disturbed metabolism in the metabolic syndrome

The clustering of risk factors for cardiovascular disease (CVD) and non-insulin-dependent diabetes mellitus (NIDDM) in obese patients may be attributable to a disturbed metabolism caused by hypophosphataemia. A low serum phosphate (S-P) level may be a limiting factor for glucose metabolism and may account for hyperglycaemia, with an increased risk of NIDDM and hypertension and consequent increased risk of stroke. Low S-HDL levels, known to exist in the metabolic syndrome, as well as high serum triglycerides may also have been the results of phosphate depletion. The hypothesis presents a new serious disturbance which accounts for the dyslipidaemia, hyperglycaemia and the hypertension in metabolic syndrome. The proposed causal relationship between low S-P and the clustering of risk factors is based on results from a cross-sectional study of obese patients, where low S-P was associated with high body mass index (BMI), high blood glucose (B-glu), high systolic blood pressure (SBP), high diastolic blood pressure (DBP), but low serum high density lipoprotein (S-HDL) and serum magnesium (S-Mg) levels. Knowledge from experimental and clinical studies on hypophosphataemia and/or phosphate depletion are referred to when discussing the hypothesis.

A comparison of renal phosphorus regulation in thermally injured and multiple trauma patients receiving specialized nutrition support

To compare phosphorus intake and renal phosphorus regulation between thermally injured patients and multiple trauma patients, 40 consecutive critically ill patients, 20 with thermal injury and 20 with multiple trauma, who required enteral tube feeding were evaluated. Phosphorus intakes were recorded for 14 days from the initiation of tube feeding which was started 1 to 3 days postinjury. Serum for determination of phosphorus concentrations was collected at days 1, 3, 7, and 14 of the study period. A 24-hour urine collection was obtained during the first and second weeks of nutrition support for urinary phosphorus excretion, fractional excretion of phosphorus, renal threshold phosphate concentration, and phosphorus clearance. Average total daily phosphorus intake during the 14-day study for thermally injured patients and multiple trauma patients was 0.99+/-0.26 mmol/kg/d vs 0.58+/-0.21 mmol/kg/d, respectively, p < .001. Serum phosphorus concentration on the third day of observation was significantly lower in the thermally injured group than those with multiple trauma (1.9+/-0.8 mg/dL vs 3.0+/-0.8 mg/dL, p < or = .01). A trend toward hypophosphatemia in the thermally injured group persisted by the seventh day of feeding (2.7+/-1.2 mg/dL vs 3.3+/-0.6 mg/dL, p < or = .04). Differences in urinary phosphorus excretion was not statistically significant between the thermally injured and multiple trauma groups (271+/-213 mg/d vs 171+/-181 mg/d for week 1, and 320+/-289 mg/d vs 258+/-184 mg/d for week 2, respectively). Urinary phosphorus clearance, fractional excretion of phosphorus, or renal threshold phosphate concentrations were also not significantly different between thermally injured and multiple trauma patients. During nutrition support, serum phosphorus concentrations are lower in thermally injured patients compared with multiple trauma patients despite receiving a significantly greater intake of phosphorus. Renal phosphorus regulation does not significantly contribute to the profound hypophosphatemia observed in thermally injured patients when compared with multiple trauma patients during nutrition support.

Hypomagnesemia and hypophosphatemia at admission in patients with severe head injury

OBJECTIVE

Low serum levels of electrolytes such as magnesium (Mg), potassium (K), calcium (Ca), and phosphate (P) can lead to a number of clinical problems in intensive care unit (ICU) patients, including hypertension, coronary vasoconstriction, disturbances in heart rhythm, and muscle weakness. Loss of these electrolytes can be caused, among other things, by increased urinary excretion. Cerebral injury can lead to polyuresis through a variety of mechanisms. We hypothesized that patients with cranial trauma might be at risk for electrolyte loss through increased diuresis. The objective of this study was to assess levels of Mg, P, and K at admission in patients with severe head injury.

DESIGN

We measured plasma levels of Mg, P, K, Ca, and sodium at admission in 18 consecutive patients with severe head injury admitted to our ICU (group 1). As controls, we used 19 trauma patients with two or more bone fractures but no significant cranial trauma (group 2).

SETTING

University teaching hospital.

PATIENTS

Eighteen patients with severe head injury admitted to our surgical ICU (group 1) and 19 controls (trauma patients with no significant cranial trauma; group 2).

MAIN RESULTS

Electrolyte levels at admission (group 1 vs. group 2; mean +/- SD, units: mmol/L) were as follows. Mg, 0.57 +/- 0.17 (range, 0.24-0.85) vs. 0.88 +/- 0.21 (range, 0.66-1.42 mmol/L; p < .01). P, 0.56 +/- 0.15 (range, 0.20-0.92) vs. 1.11 +/- 0.15 (range, 0.88-1.44 mmol/L; p < .01). K, 3.54 +/- 0.59 (range, 2.4-4.8) vs. 4.07 +/- 0.45 (range, 3.6-4.8 mmol/L; p < .02). Ca, 2.02 +/- 0.24 (range, 1.45-2.51) vs. 2.14 +/- 0.20 (range, 1.88-2.46; p = NS). In group 1, 12/18 patients had Mg levels <0.70 mmol/L vs. 2/19 patients in group 2 (p < .01); in group 1, 11/18 patients had P levels below 0.60 mmol vs. 0/19 patients in group 2 (p < .01). Moderate hypokalemia (K levels, <3.6 mmol/L) was present in 8/18 patients in group 1 vs. 1/19 patients in group 2 (p < .01). Severe hypokalemia (K levels, < or =3.0) was present in 4/18 patients in group 1 vs. 0/19 patients in group 2 (p < .05).

CONCLUSION

We conclude that patients with severe head injury are at high risk for the development of hypomagnesemia, hypophosphatemia, and hypokalemia. One of the causes of low electrolyte levels in these patients may be an increase in the urinary loss of various electrolytes caused by neurologic trauma. Mannitol administration may be a contributing factor. Intensivists should be aware of this potential problem. If necessary, adequate supplementation of Mg, P, K, and Ca should be initiated promptly.

High prevalence of hypophosphataemia amongst patients with infectious diseases. A retrospective study

OBJECTIVES

To describe the prevalence of hypophosphataemia amongst all patients treated during 1993 for infectious diseases. The associations between serum C-reactive protein, serum albumin and white blood cells in blood were studied amongst hypophosphataemic patients. Comparisons were made according to the severity of infection.

DESIGN

A retrospective study of the prevalence of hypophosphataemia, and a case-control study amongst a subgroup of patients.

SETTING

The Department of Infectious Diseases, University Hospital, Umeå, Sweden.

SUBJECTS

For the prevalence study all 967 patients (449 women and 518 men) treated during 1993 were included. In the case-control study, 108 cases, with serum phosphate < or =0.64 mmol L(-1), 216 age-and sex-matched controls with serum phosphate >0.82 mmol L(-1) (men) and >0.86 mmol L(-1) (women), respectively, were included.

RESULTS

In 402 of 967 patients (42%) at least one serum phosphate value was below the reference level. Hypophosphataemia was found in 573 of 1966 blood samples (29%). Severe hypophosphataemia (<0.30 mmol L(-1)) was seen in 1.2% of the patients (0.9% of blood samples). The prevalence of hypophosphataemia was higher amongst women than amongst men. In the case-control study, the serum C-reactive protein and the number of white blood cells was higher amongst the cases compared with the controls (124 vs. 94 mg L(-1) and 11.4 vs. 9.3 cells/L x10(9), respectively). The multiple logistic regression showed a 4-fold higher risk of having low serum phosphate in patients with severe infection, compared with mild infections. None of the other variables (albumin, days of hospital stay or white blood cells in blood) increased the risk for hypophosphataemia.

CONCLUSIONS

The high prevalence of low serum phosphate levels and the increased risk of having low levels in severe infections shown in this study needs further attention.

Efficacy and safety of intravenous phosphate replacement in critically ill patients

OBJECTIVE

To evaluate the efficacy and safety of intravenous potassium phosphate administered in a fixed-dose regimen in critically ill patients.

DESIGN

Prospective, unblind study.

SETTING

Surgical-medical intensive care unit (ICU).

PARTICIPANTS

Patients who developed hypophosphatemia during their ICU admission.

INTERVENTIONS

Patients with a serum phosphate concentration between 1.27 and 2.48 mg/dL (group 1) and those with a concentration of 1.24 mg/dL or less (group 2) received 15 and 30 mmol, respectively, of phosphate as a potassium salt via a central line over 3 hours.

MAIN OUTCOME MEASURES

Normalization of serum phosphate within 6 hours of infusion, the development of arrhythmias during the infusion, and the development of hypocalcemia and hyperkalemia after the infusion were evaluated. Redevelopment of hypophosphatemia and the need for further therapy were also assessed.

RESULTS

Thirty-seven episodes of hypophosphatemia were entered in this study: 27 in group 1 (17 patients) and 10 in group 2 (10 patients). The mean serum phosphate concentration increased significantly from 2.02 to 2.82 mg/dL in group 1 and from 0.83 to 2.17 mg/dL in group 2, with no change in calcium or potassium. Normalization of serum phosphate with this initial dose occurred in 81.5% of the episodes in group 1 and 30% in group 2. However, over the following 2 days, 45% of the patients in group 1 and 60% in group 2 required further phosphate supplementation. No arrhythmias occurred during the 3-hour infusion that were related to the potassium phosphate. A significant drop in total serum calcium concentrations occurred in 2 patients who were slightly hypercalcemic prior to the infusion. Serum calcium concentrations remained above normal, but this was not associated with any adverse effects.

CONCLUSIONS

The administration of potassium phosphate 15 mmol to critically ill patients with mild-to-moderate hypophosphatemia over 3 hours is both effective and safe. The administration of potassium phosphate 30 mmol to severely hypophosphatemic patients was safe but achieved normalization of serum phosphate in a minority of patients. Either a higher dose or the subsequent administration of more potassium phosphate may be required to normalize serum phosphate concentrations. Once normalization has occurred, there is a high likelihood of redevelopment of hypophosphatemia over the following 2 days and supplementation should be given accordingly.

Laboratory abnormalities in patients with bacterial pneumonia

STUDY OBJECTIVES

This study was undertaken to evaluate the laboratory abnormalities observed in patients with bacterial pneumonia as predictors of the severity of illness.

DESIGN

Retrospective analysis.

SETTING

Tertiary care hospital.

PATIENTS AND PARTICIPANTS

We studied 302 consecutive patients who were admitted to the Long Island Jewish Medical Center from January through December 1993 and treated for bacterial pneumonia. The patients were subdivided into two groups based on their serum phosphorus level either on hospital admission or 4 days before the onset of pneumonia, if this was acquired in-hospital. Hypophosphatemia (group 1) was defined as serum phosphorus level of < or = 2.4 mg/dL and normophosphatemia > 2.4 mg/dL (group 2). Three hundred randomly selected hospitalized patients treated for conditions other than pneumonia comprised the control group (group 3).

MEASUREMENTS

Groups 1 and 2 were compared with respect to laboratory data, mortality rate, and duration of hospitalization. The laboratory data of patients in group 3 were compared with those treated for bacterial pneumonia (groups 1 and 2). Stepwise multivariate logistic regression analysis was employed to identify the variables that best predicted the onset of pneumonia.

RESULTS

In groups 1 and 2, a greater (p < 0.0001) number of patients (135 of 302 patients with pneumonia, 44.7%) developed hypophosphatemia compared with patients in group 3 (31 of 300 control subjects, 10.3%). Patients with pneumonia (groups 1 and 2) had higher levels (p < 0.01) of bicarbonate compared with control subjects. Moreover, patients with pneumonia demonstrated lower levels (p < 0.01) of calcium, phosphorus, albumin, cholesterol, and alanine aminotransferase compared with control patients (group 3). Among patients with pneumonia, those with hypophosphatemia (group 1) had significantly lower levels (p < 0.05) of potassium, calcium, and albumin compared to those subjects with normophosphatemia (group 2). Furthermore, hypophosphatemic subjects manifested higher levels of glucose (p < 0.01) and creatine phosphokinase (p < 0.05) compared to their normophosphatemic counterparts. In addition, hypophosphatemic patients experienced a longer duration of hospital stay (hypophosphatemia, 24.6 +/- 2.0 days, vs normophosphatemia, 14.1 +/- 1.0, p < 0.001) and higher (p < 0.001) mortality compared to normophosphatemic subjects. The incidence of nosocomial pneumonia was higher (p < 0.0001) in hypophosphatemic patients compared to those with normophosphatemia.

CONCLUSION

We conclude that hypophosphatemia, hypocalcemia, hypokalemia, and hypoalbuminemia may be predictors of the severity of illness in patients admitted to the hospital with bacterial pneumonia.

Fatal bupropion overdose

BACKGROUND

Bupropion is a unique monocyclic antidepressant that has been known to cause seizures in high therapeutic doses and in acute overdoses. Death due to ingestion, however, is a rare occurrence.

CASE REPORT

We report a case of a 26-year-old man who ingested 23 g bupropion, developed seizures and hypoxia, and presented in cardiac arrest. The patient was resuscitated in the emergency department, but died 4 d after supportive intensive care.

CONCLUSIONS

Bupropion overdose may lead to recurrent seizures, hypoxia and death. Aggressive management of severe bupropion overdose is recommended.

Laboratory Abnormalities in Patients in the Medical Intensive Care Unit

Objective:

The goals of this article are to (1) identify the incidence of reported laboratory abnormalities in patients in the medical intensive care unit (ICU); (2) characterize the relationship between reported laboratory abnormalities and Acute Physiology and Chronic Health Evaluation III (APACHE III) score, length of stay, and mortality; and (3) evaluate therapeutic replacement in patients with electrolyte abnormalities.

Design:

Retrospective chart review of all patients admitted to the medical ICU between April 1, 1993 and June 30, 1993.

Setting:

Large teaching institution.

Participants:

Patients admitted to the medical ICU (n = 116).

Interventions:

The following data were collected: age, sex, admitting diagnosis, serum electrolyte and laboratory parameters, APACHE HI score, length of ICU stay, and mortality.

Results:

Ten individual laboratory abnormalities were found in more than 30% of all patients in the medical ICU (range 32.8–59.5%). Abnormalities in four laboratory parameters were associated with undesirable patient outcomes. Patients with hypoalbuminemia had a significantly higher APACHE HI score (p < 0.05). Hypocalcemia, hypomagnesemia, and hypoalbuminemia all were associated with an increased length of stay in the ICU (p < 0.05). Overall mortality was significantly higher in patients with alkalosis (p = 0.002). Therapeutic replacement in those with low electrolyte concentrations often was delayed or missed. Fifteen to 75% of patients who had abnormally low serum electrolyte concentrations were not treated.

Conclusions:

A high incidence of laboratory abnormalities is reported in patients admitted to the medical ICU. Several of these abnormalities are associated with undesirable outcomes such as an increased length of ICU stay in patients with hypoalbuminemia, hypocalcemia, and hypomagnesemia and increased mortality in patients with alkalosis. Therapeutic replacement of electrolytes in patients with abnormalities often was delayed or missed.