Treatment of hypophosphatemia in patients receiving specialized nutrition support using a graduated dosing scheme: results from a prospective clinical trial

[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.

Guidelines for the Intravenous Management of Hypophosphatemia, Hypomagnesemia, Hypokalemia, and Hypocalcemia

Nutrition Support Consultant features issues pertinent to the clinical aspects of pharmacy nutritional support practice.

Refeeding Syndrome in the Intensive Care Unit

Nutrition Support Consultant features issues pertinent to the clinical aspects of pharmacy nutrition support practice.

A New Graduated Dosing Regimen for Phosphorus Replacement in Patients Receiving Nutrition Support

BACKGROUND

Hypophosphatemia is a common metabolic complication in patients receiving specialized nutrition support. We changed our previously reported dosing algorithm because the low dose no longer appeared to be effective at increasing serum phosphorus concentrations. The purpose of this study was to evaluate the safety and efficacy of a revised weight-based phosphorus-dosing algorithm in critically ill trauma patients receiving specialized nutrition support.

METHODS

Seventy-nine adult trauma patients with hypophosphatemia (serum phosphorus concentration < or = 0.96 mmol/L) receiving nutrition support received an IV dose of phosphorus on day 1 according to the serum concentration of phosphorus: 0.73-0.96 mmol/L (0.32 mmol/kg, low dose), 0.51-0.72 mmol/L (0.64 mmol/kg, moderate dose), and < or = 0.5 mmol/L (1 mmol/kg, high dose). The IV phosphorus bolus dose was administered at 7.5 mmol/hour. Generally, patients with a serum potassium concentration <4 mmol/L received potassium phosphate and patients with a serum potassium concentration > or = 4 mmol/L received sodium phosphate. Patients who still had hypophosphatemia on day 2 were dosed using the new dosing algorithm by the nutrition support service according to that day's serum concentration of phosphorus, or empirically by the trauma service.

RESULTS

Of the 79 patients studied, 57 were male and 22 were female with a mean age of 44.8 +/- 20.6 years. Mean Injury Severity Scores and APACHE-II scores were 27.1 +/- 11.6 and 15.2 +/- 6.8, respectively. There was no difference in baseline characteristics among the 3 dosing groups. Of the 79 patients, 34 received the low dose, 30 received the moderate dose, and 15 received the high dose of phosphorous. Mean serum phosphorous concentrations on day 2 were significantly increased in the moderate-dosed group (0.64 +/- 0.06 to 0.77 +/- 0.22 mmol/L, p < .05) and high-dosed group (0.38 +/- 0.06 to 0.93 +/- 0.32 mmol/L, p < .01), respectively, when compared with day 1. Mean serum phosphorus concentrations were normal in all 3 groups on day 3. Serum concentrations of magnesium, sodium, and potassium, as well as arterial pH, were stable across the study. Mean concentrations of ionized calcium were not significantly different in any of the 3 dosing groups across the study period.

CONCLUSIONS

This weight-based phosphorus-dosing algorithm is safe for use in critically ill patients receiving nutrition support. The moderate and severe-dose regimens effectively increase serum phosphorus concentrations.

Evaluation of an Intravenous Potassium Dosing Algorithm for Hypokalemic Critically Ill Patients

PURPOSE

The intent of this study was to evaluate the safety and efficacy of an intravenous (IV) potassium (K) dosing algorithm for hypokalemic critically ill trauma patients.

METHODS

Adult patients, admitted to the trauma intensive care unit from June 2010 to October 2012 and who received IV K therapy according to a standardized dosing algorithm, were retrospectively evaluated. Patients who received IV K during resuscitation or following initiation of nutrition therapy, IV fluids containing >20 mEq/L of potassium, or medications known to alter K homeostasis or those with an arterial pH change >0.1, diarrhea, hypomagnesemia, renal impairment, or morbid obesity were excluded.

RESULTS

In total, 715 patients were reviewed to obtain 100 evaluable patients. Serum K for patients with mild depletion (serum K, 3.5-3.9 mEq/L, n = 74) remained unchanged at 0.0 ± 0.3 mEq/L ( P = ns) following 46 ± 8 mEq. Serum K increased by 0.4 ± 0.3 mEq/L ( P = .001) following 78 ± 18 mEq during moderate depletion (serum K, 3-3.4 mEq/L). None of the patients experienced hyperkalemia (serum K, >5.2 mEq/L) postinfusion. The presence of traumatic brain injury (TBI) blunted the response to IV K for mild K depletion as only 26% had an increase in serum K compared with 55% of patients without TBI ( P = .025).

CONCLUSIONS

The Nutrition Support Service-guided IV K dosing algorithm was safe for patients with mild and moderate hypokalemia and efficacious for those with moderate hypokalemia. Further study in patients with severe hypokalemia (serum K, <3 mEq/L) is warranted.

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.

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.

A prospective examination of weight gain in hospitalized adolescents with anorexia nervosa on a recommended refeeding protocol

PURPOSE

Current refeeding recommendations for adolescents hospitalized with anorexia nervosa (AN) are conservative, starting with low calories and advancing slowly to avoid refeeding syndrome. The purpose of this study was to examine weight change and clinical outcomes in hospitalized adolescents with AN on a recommended refeeding protocol.

METHODS

Adolescents aged 13.1-20.5 years were followed during hospitalization for AN. Weight, vital signs, electrolytes, and 24-hour fluid balance were measured daily. Percent median body mass index (%MBMI) was calculated as 50th percentile BMI for age and gender. Calories were prescribed on admission and were increased every other day.

RESULTS

Thirty-five subjects with a mean (SD) age of 16.2 (1.9) years participated over 16.7 (6.4) days. Calories increased from 1,205 (289) to 2,668 (387). No subjects had refeeding syndrome; 20% had low serum phosphorus. Percent MBMI increased from 80.1 (11.5) to 84.5 (9.6); overall gain was 2.10 (1.98) kg. However, 83% of subjects initially lost weight. Mean %MBMI did not increase significantly until day 8. Higher calories prescribed at baseline were significantly associated with faster weight gain (p = .003) and shorter hospital stay (p = .030) in multivariate regression models adjusted for %MBMI and lowest heart rate on admission.

CONCLUSIONS

Hospitalized adolescents with AN demonstrated initial weight loss and slow weight gain on a recommended refeeding protocol. Higher calorie diets instituted at admission predicted faster weight gain and shorter hospital stay. These findings support the development of more aggressive feeding strategies in adolescents hospitalized with AN. Further research is needed to identify caloric and supplementation regimens to maximize weight gain safely while avoiding refeeding syndrome.

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.

Influence of traumatic brain injury on potassium and phosphorus homeostasis in critically ill multiple trauma patients

OBJECTIVE

The intent of this study was to ascertain whether multiple trauma patients with traumatic brain injury (TBI) had lower serum concentrations of potassium and phosphorus and required more aggressive supplementation than multiple trauma patients without TBI.

METHODS

Ventilator-dependent adult patients without renal impairment who were admitted to the trauma intensive care unit or neurosurgical intensive care unit and who received enteral nutrition were evaluated for the first 14 d after hospital admission. Patients were grouped according to the presence or absence of TBI. Target serum concentrations for potassium and phosphorus were 4 mEq/L and 4 mg/dL, respectively. Electrolyte repletion therapy was given according to the nutritional support service guidelines.

RESULTS

Fifty trauma patients (25 with and without TBI) were studied. Daily serum potassium concentrations were consistently lower for those with TBI (P < or = 0.001), whereas the mean net potassium intake was greater (1.3 +/- 0.5 versus 0.7 +/- 0.3 mEq x kg(-1) x d(-1), respectively, P < or = 0.001). Serial serum phosphorus concentrations were similar between groups (P = NS) except for a significantly lower serum phosphorus concentration for trauma patients with TBI on day 3 after hospital admission (2.5 +/- 0.5 versus 2.9 +/- 0.7 mg/dL, respectively, P < or = 0.05). However, the mean net phosphorus intake was significantly greater for trauma patients with TBI (0.65 +/- 0.25 versus 0.45 +/- 0.17 mmol x kg(-1) x d(-1), P < or = 0.001).

CONCLUSION

Potassium and phosphorus requirements are greater for multiple trauma patients with TBI compared with those without TBI.

Unrecognized acute phosphate nephropathy in a kidney donor with consequent poor allograft outcome

Acute phosphate nephropathy following a large phosphate load is a potentially irreversible cause of kidney failure. Here, we report on the unfavorable graft outcome in two recipients of deceased donor kidneys from a donor who had evolving acute phosphate nephropathy at the time of organ procurement. The donor, a 30-year-old with cerebral infarction, developed hypophosphatemia associated with diabetic ketoacidosis and was treated with intravenous phosphate resulting in a rise in serum phosphorus from 0.9 to 6.1 mg/dL. Renal biopsies performed on both recipients for suboptimal kidney function revealed acute tubular injury and diffuse calcium phosphate microcrystal deposits in the tubules, which were persistent in subsequent biopsies. A retrospective review of preimplantation biopsies performed on both kidneys revealed similar findings. Even though initial renal histology in both recipients was negative for BK virus, they eventually developed BK viremia with nephropathy but both had a substantive virologic response with therapy. The first patient returned to dialysis at 6 months, while the other has an estimated glomerular filtration rate of 12 mL/min, 17 months following his transplant. We conclude that unrecognized acute phosphate nephropathy in a deceased donor contributed substantially to poor graft outcome in the two recipients.

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.

Low serum total calcium concentration as a marker of low serum ionized calcium concentration in critically ill patients receiving specialized nutrition support

BACKGROUND

The intent of this study was to ascertain to what extent serum total calcium concentration (tCa) <7 mg/dL reflects hypocalcemia (defined by ionized calcium concentration [iCa] of < or = 1.12 mmol/L) in critically ill patients receiving specialized nutrition support.

METHODS

Adult patients (> or = 18 years) admitted to the trauma, surgical, medical, burn, or neurosurgical intensive care units, trauma stepdown unit, or progressive care unit and referred to the nutrition support service were retrospectively identified for potential inclusion into the study. Serum chemistries, arterial blood gas measurements, nutrition markers, and serum iCa were simultaneously obtained from each patient approximately 1 day after initiation of specialized nutrition support. Patients with a serum creatinine > or = 2 mg/dL, hyperphosphatemia (> or = 6 mg/dL), severe hypomagnesemia (< or = 1.12 mg/dL), history of metabolic bone disease, or parathyroid disease were excluded from the analysis.

RESULTS

One hundred ninety-five patients (91% who had multiple trauma, with a mean Injury Severity Score 31 +/- 13) were enrolled into the study. Specialized nutrition support was initiated 2.8 +/- 1.8 days and calcium status was studied 4.2 +/- 3.1 days after hospital admission, respectively. The majority (28 of 33, or 85%) of patients with a tCa <7 mg/dL were hypocalcemic compared with 33% (22 out of 66) of patients with a tCa of 7-7.4 mg/dL, and 11% (11 of 96) of those with a tCa of 7.5-7.9 mg/dL (p < .001).

CONCLUSIONS

Critically ill patients with a serum total calcium concentration of <7 mg/dL have a high rate of hypocalcemia (iCa < or = 1.12 mmol/L). Hypocalcemia, defined as a serum iCa of < or = 1.12 mmol/L, occurs in 85% of acutely ill patients with a serum tCa <7 mg/dL.

Treatment of moderate to severe acute hypocalcemia in critically ill trauma patients

BACKGROUND

Our recent data indicate that 21% of critically ill, adult, multiple-trauma patients receiving specialized nutrition support experience hypocalcemia. However, evidence-based methods for the treatment of moderate to severe acute hypocalcemia (ionized calcium concentration [iCa] <1 mmol/L) are lacking.

METHODS

The efficacy of an infusion of 4 g of calcium gluconate was evaluated in 20 critically ill, adult, multiple-trauma patients with moderate to severe hypocalcemia (iCa <1 mmol/L). The calcium gluconate was infused at a rate of 1 g/h in a small volume admixture. A serum iCa determination was obtained on the following day.

RESULTS

Calcium gluconate infusion significantly increased serum iCa from 0.90 +/- 0.08 mmol/L to 1.16 +/- 0.11 mmol/L (p < .001) on the following day. This dosage regimen was successful for achieving a serum iCa >1 mmol/L for 19 of 20 (95%) hypocalcemic patients and achieved a concentration >1.12 mmol/L in 14 (70%) of the patients. Two patients developed mild hypercalcemia (iCa of 1.34 mmol/L and 1.38 mmol/L) postinfusion.

CONCLUSIONS

A short-term infusion of 4 g of intravenous (IV) calcium gluconate for the treatment of moderate to severe hypocalcemia appears to be a promising regimen for critically ill, adult, multiple-trauma patients.

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.

Hepatic surgery-related hypophosphatemia

This review describes pathophysiology of post-surgical hypophosphatemia (HP), which has particularly high incidence following liver transplantation. HP remains poorly understood; and there is a lack of universally accepted guidelines for its investigation and management. The pathogenesis of HP following major liver surgery has been hypothesized as being due either to excessive utilization by regenerating liver or increased urinary losses of phosphate. This review provides evidence that excessive urinary loss rather than increased Pi uptake by the liver is the most likely mechanism, and this may be mediated by recently described phosphaturic factors, known as phosphatonins. Until recently blood Pi homeostasis had been explained solely in terms of classical hormones, i.e., vitamin D and PTH. It is however increasingly recognized that phosphatonins may play a critical role in the post-operative HP, but the exact mechanism and candidate phosphaturic factor has not yet been identified. In this review, we have described likely mechanisms and suggest candidate phosphatonins that may mediate urinary Pi loss following liver transplantation. We also discuss the biochemical consequences of cellular Pi depletion, which exposes some gaps in the utilization of established knowledge and therefore in the management of HP. The main aspects of pathophysiology of HP and cellular Pi depletion are presented to provide rational for novel biochemical investigations, which are likely to improve monitoring of HP associated metabolic stress as well as extent of severity of HP, and thereby enhance management of these patients.

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.

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.

Dose-dependent characteristics of intravenous calcium therapy for hypocalcemic critically ill trauma patients receiving specialized nutritional support

OBJECTIVE

The purpose of this investigation was to evaluate the dose-dependent characteristics of intravenous calcium gluconate therapy for hypocalcemic critically ill patients.

METHODS

The dose-dependent characteristics of 2 g versus 4 g of intravenous calcium gluconate therapy were evaluated in 25 critically ill, adult multiple trauma patients with hypocalcemia. The calcium gluconate was infused at a rate of 1 g/h for both groups. Patients weighed within 90% to 120% of ideal body weight, had normal renal function, did not receive diuretic therapy, and did not have anasarca.

RESULTS

Fifteen patients with mild hypocalcemia (serum ionized calcium concentration [iCa] 1-1.12 mmol/L) were given 2 g of calcium gluconate. Ten patients with moderate to severe hypocalcemia (iCa <1 mmol/L) were given 4 g. Each dosage group had a significant (P < or = 0.001) increase in iCa (from 1.07 +/- 0.05 to 1.17 +/- 0.05 mmol/L and from 0.92 +/- 0.08 to 1.16 +/- 0.11 mmol/L, respectively). Each dosage group retained about half of the dose in the exchangeable calcium space (P = NS between groups), but the higher dosage group retained significantly more elemental calcium overall (81 +/- 38 versus 201 +/- 50 mg, respectively, P < or = 001). Serum ionized calcium concentrations achieved a plateau without a further decline in iCa by 10 h after completion of the infusion for each dosage.

CONCLUSION

About half of the administered elemental calcium dose was retained for each dosage group, with the higher dose (4 g) resulting in significantly more elemental calcium retention in the exchangeable calcium space. An iCa determination performed about > or =10 h after the completion of the calcium gluconate infusion should be sufficient time to ensure equilibration of iCa to assess the efficacy of the therapy. This mode of calcium therapy serves as an effective means for providing calcium to the acutely hypocalcemic, critically ill, multiple trauma patient.

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 acute hypocalcemia in critically ill multiple-trauma patients

BACKGROUND

Recent data indicate that critically ill, adult multiple trauma patients receiving specialized nutrition support commonly experience hypocalcemia (ionized serum calcium [iCa] < or =1.12 mmol/L). However, validated methods for the treatment of acute hypocalcemia are lacking.

METHODS

The efficacy of a single dose of calcium gluconate using an empiric IV calcium gluconate graduated dosing regimen was evaluated in 37 patients. Patients with an iCa of 1-1.12 mmol/L (mild hypocalcemia) were provided 1-2 g of IV calcium gluconate. Patients with an iCa of <1 mmol/L (moderate to severe hypocalcemia) were given 2-4 g. The calcium gluconate was infused at a rate of 1 g/h in a small-volume admixture. Serum iCa determination was repeated on the following day.

RESULTS

One to 2 g of IV calcium gluconate was effective in normalizing iCa for 23 out of 29 patients (79%) with mild hypocalcemia and 2-4 g was effective for 3 of 8 patients (38%) with moderate to severe hypocalcemia. The individual response to calcium therapy (g/d) or when normalized to body weight (mg/kg/d) was highly variable.

CONCLUSIONS

One to 2 g of IV calcium gluconate were effective for most patients with mild hypocalcemia; however, treatment of moderate to severe hypocalcemia with 2-4 g of IV calcium gluconate was often unsuccessful. Further study with frequent serial ionized serum calcium and phosphorus determinations and electrocardiographic monitoring appears to be indicated for patients with moderate to severe hypocalcemia.

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.

Assessing the metabolic and clinical consequences of early enteral feeding in the malnourished patient

BACKGROUND

It is often thought that enteral feeding should be initiated slowly in those who are severely malnourished. This descriptive study examined the effect of an enteral feeding protocol on the typical metabolic consequences seen in refeeding syndrome.

METHODS

A retrospective chart review was conducted on 51 patients who had been placed on hospital-wide enteral feeding and electrolyte replacement protocols over a 9-month period to determine whether there were any negative clinical consequences to early feeding.

RESULTS

Goal feeding rate was achieved within 17.6 +/- 8.7 hours. Forty patients (80%) developed depletions in phosphate, magnesium, or potassium after initiation of enteral feeding, including 93% of those deemed "at risk" and 74% of those "not at risk." All patients received electrolyte replacement according to protocols, and no patients showed any negative clinical effect.

CONCLUSIONS

This study showed that malnourished patients at risk for refeeding syndrome can be fed early without observed negative clinical consequences. An electrolyte replacement protocol may be an effective means of minimizing the electrolyte imbalances associated with early feeding. It also demonstrated the significance of applying such protocols to all patients requiring enteral support, as current methods of assessing "risk"for refeeding syndrome may be inadequate.

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: effective and safe treatment with Phosphates Polyfusor

BACKGROUND

Severe hypophosphataemia associated with refeeding syndrome requires treatment with intravenous phosphate to prevent potentially life-threatening complications. However, evidence for replacement regimens is limited and current regimens are complex and replace phosphate inadequately.

AIM

To assess the effectiveness and safety of 50 mmol intravenous phosphate infusion, given as a 'Phosphates Polyfusor', for the treatment of severe hypophosphataemia in refeeding syndrome.

METHODS

Patients with refeeding syndrome and normal renal function received a Phosphates Polyfusor infusion for the treatment of severe hypophosphataemia (< 0.50 mmol/L). The outcome measures were serial serum phosphate, creatinine and calcium concentrations for 4 days following phosphate infusion and adverse events.

RESULTS

Over 2 years, 30 patients were treated. Following treatment, 37% of cases had a normal serum phosphate concentration and 73% had a serum phosphate concentration of > 0.5 mmol/L within 24 h. Ten patients required more than one Phosphates Polyfusor infusion. Within 72 h, 93% of cases had achieved a serum phosphate concentration of > or = 0.50 mmol/L. No patient developed renal failure. Three episodes of transient mild hyperphosphataemia were recorded. Four patients developed mild hypocalcaemia.

CONCLUSIONS

This is the largest published series of the use of intravenous phosphate for the treatment of severe hypophosphataemia (< 0.50 mmol/L), and is the most effective regimen described. All patients had refeeding syndrome and were managed on general wards.

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.

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.

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.