Sodium glycerophosphate in the treatment of neonatal hypophosphataemia

Quality improvement project in a neonatal intensive care unit reduced the prevalence and duration of hypophosphatemia with significant and sustainable results

BACKGROUND

Hypophosphatemia is associated with prolonged mechanical ventilation and may affect growth, bone mineralization, nephrocalcinosis, and mortality in preterm infants. Optimal nutrition practices may decrease risk for hypophosphatemia and improve outcome.

METHODS

A quality improvement project was established to improve parenteral and enteral phosphorus intake with the goal to decrease prevalence and duration of hypophosphatemia in the first 14 days in infants <32 weeks' gestation.

RESULTS

Among 406 preterm infants, the prevalence of moderate hypophosphatemia decreased from 44% to 19% (P < 0.01) over 4 years. The median duration of moderate hypophosphatemia decreased from 72 h (48-128) to 24 (24-53) (P < 0.01). Daily intakes of parenteral calcium and phosphorus on the fourth day of life increased from 1.5 to 2.5 mEq/kg/day (P < 0.01) and 0.6 to 1.3 mmol/kg/day (P < 0.01), respectively. The median postnatal age of first serum phosphorus concentration assessment decreased from 53 h (41-64) to 32 (24-40) (P < 0.01).

CONCLUSION

During this quality improvement project, reduced prevalence and duration of hypophosphatemia in infants <32 weeks' gestation in the first 14 days of life was achieved through the optimization of parenteral and enteral phosphorus intake and improved response to acute hypophosphatemia.

Use of sodium glycerophosphate in neonatal parenteral nutrition solutions to increase calcium and phosphate compatibility for preterm infants

BACKGROUND

Preterm infants require higher calcium and phosphate intake than term infants to facilitate adequate bone growth, but this is rarely met in parenteral nutrition (PN) solution because of the limited solubility of calcium and phosphate. This study aimed to evaluate the solubility of organic phosphate with calcium gluconate in neonatal PN solutions, simulating its clinical use.

METHODS

PN solutions were composed of calcium gluconate at 50 mEq/L and sodium glycerophosphate (NaGP) at 25 mmol/L. Another component included 1% or 4% amino acid and 10% or 20% dextrose. For comparison, PN solution composed of potassium phosphate was also evaluated. Each solution was evaluated using the following methods: visual inspection, light obscuration particle count test, and pH measurement. To simulate the clinical condition, the solution was tested after compounding, after being stored at 25 °C for 24 h, and after being stored at 2°C-8°C for 2 or 9 days and subsequently at 25 °C for 24 h.

RESULTS

There was no visual deposition in PN solution using NaGP in any of the concentrations and under any stored condition. The solution fulfilled the criteria of physical compatibility as < 25 particles/mL measuring ≥10 μm in diameter and <3 particles/mL measuring ≥25 μm in diameter. On the contrary, visual deposition was evidently noted in PN solution using potassium phosphate after its formulation, and the particle count significantly exceeded the range of physical compatibility.

CONCLUSION

NaGP and calcium gluconate have significantly good compatibility in PN solution. The use of NaGP in neonatal PN prevents calcium and phosphorus precipitation, hence increasing their supply to preterm infants in meeting their growth requirement.

New diagnostic modalities and emerging treatments for neonatal bone disease

Bone disease in the neonatal period has often been regarded as an issue affecting premature infants, or a collection of rare and ultra-rare disorders that most neonatologists will see only once or twice each year, or possibly each decade. The emergence of targeted therapies for some of these rare disorders means that neonatologists may be faced with diagnostic dilemmas that need a rapid solution in order to access management options that did not previously exist. The diagnostic modalities available to the neonatologist have not changed a great deal in recent years; blood tests and radiographs still form the mainstays with other techniques usually reserved for research studies, but rapid access to genomic testing is emergent. This paper provides an update around diagnosis and management of bone problems likely to present to the neonatologist.

[Early hypophosphataemia in at risk newborns. Frequency and magnitude]

OBJECTIVE

To determine the frequency and magnitude of neonatal hypophosphataemia (<4mg/dL) in a neonatal Intensive Care Unit and to describe risk groups.

PATIENTS AND METHODS

Retrospective study of hospitalised newborns over a 44 month period (phase 1). Retrospective study of <1,500g/<32 weeks of gestation newborns over a 6 month period (phase 2). Prospective study of <1,500g or 1,550-2,000g, and intrauterine growth restriction (IUGR) newborns. Measurements were made on the 1st, 3rd, 7th, and 14th days of life (phase 3).

RESULTS

Phase 1: 34 (2.4%) of 1,394 patients had a diagnosis of hypophosphataemia, 76% of them ≤32 weeks of gestation and <1500 grams, and 24% >32 weeks with weight<P10. Phase 2: 12 (16.4%) of 73 patients had a diagnosis of hypophosphataemia, with <2mg/dL in 5 (6.8%). Eight (75%) of those with hypophosphataemia had IUGR, and 4 (25%) weighed <1,000g. Five cases had associated hypokalaemia, and three hypercalcaemia. Phase 3: 9 (45%) of 20 patients had hypophosphataemia, all of them <1,000g or<1,200g and weight percentile <10. Thirty-three percent of samples on days 1, 3, and 7 showed hypophosphataemia, four of them <2mg/dL. There was mild hypokalaemia in 5 (55%), and mild hypercalcaemia in 2 (22%) cases. Hypophosphataemia was associated with lower enteral nutrition and higher parenteral amino acid intake in the early days of life.

CONCLUSIONS

Hypophosphataemia is common, and can be severe, in the first week of life in premature infants <1,000 grams, and newborns<1,200g with foetal malnutrition and receiving amino acids in early parenteral nutrition.

Early postnatal calcium and phosphorus metabolism in preterm infants

OBJECTIVES

Bone mineralisation in preterm infants is related to the supply of calcium (Ca) and phosphorus (P). We increased the amount of minerals in parenteral nutrition (PN) for preterm infants and evaluated postnatal Ca and P metabolism in relation to mineral and vitamin D (vitD) intake.

METHODS

Preterm infants, included on their first day of life, received standard PN, providing a maximum Ca/P intake of 3/1.92 mmol · kg(-1) · day(-1) on day 3. Ca/P content of formula was 2.5/1.6 mmol/dL, and fortified human milk was 2.4/1.95 mmol/dL. PN supplied 80 IU · kg(-1) · day(-1) vitD. Formula and fortified human milk contained 200 IU/dL of vitD. During a 5-week period, serum concentrations and urinary excretion of Ca/P were registered and related to the intake of minerals and vitD.

RESULTS

During 12 months, 79 infants (mean gestational age 29.8 ± 2.2 weeks, mean birth weight 1248 ± 371 g) were included. The recommended intake for minerals was achieved by day 5 and for vitD by 4 weeks. Infants developed hypercalcaemia, hypercalciuria, and hypophosphataemia during the first postnatal week, leading to the additional P supplementation in 49 infants. The renal tubular reabsorption of P was >95% until day 9 but decreased <70% after the second week. Alkaline phosphatase was normal at birth, increased to a maximum of 450 IU/L by day 14, and remained above the normal range for the remaining period.

CONCLUSIONS

Parenteral intake of P appeared to be too low, leading to mineral imbalances in the early postnatal period, and vitD intake was also below recommendations.

Glycerophosphate is interchangeable with inorganic phosphate in terms of safety and serum pharmacokinetics

OBJECTIVE

The primary aim of the present investigation was to determine and compare the pharmacokinetic (PK) profiles of inorganic phosphate in serum and urine after intravenous administration of sodium glycerophosphate and inorganic sodium phosphate. Additionally, study product safety profiles were evaluated.

SUBJECTS AND METHODS

In total, 27 healthy, white volunteers (17 male/10 female) were enrolled in this double-blinded, randomized, 2-sequence, crossover study and were assigned to receive an organic test drug (sodium glycerophosphate) and an inorganic reference preparation (sodium phosphate) on 2 occasions. Validated analytical methods were used, and concentrations of total inorganic phosphate in serum and urine were determined over 24 h following a single 4-hour continuous intravenous infusion of test and reference drugs at a dose of 80 mmol. Study days were separated by washout periods of 7 days. An analysis of variance, based on population means and 90% confidence intervals (CIs), was used for testing bioequivalence (BE; range 0.8-1.25) between investigational products.

RESULTS

The geometric means of the ratio of the point estimates and corresponding 90% CIs for the area under the concentration-versus-time curve of inorganic serum phosphate from 0 to 24 h (AUC(0-24)), the phosphate's maximum concentration in serum (C(max)) and the total amount of inorganic phosphate excreted in urine over 24 h corrected for individual baseline values (Ae(0-24 bc)) were estimated. The test/reference ratios for inorganic phosphate were 1.04 (CI 1.00-1.07), 0.85 (CI 0.84-0.87) and 0.84 (CI 0.77-0.92) for AUC(0-24), C(max) in serum and Ae(0-24 bc) in urine, respectively. Hence, standard BE criteria were met for AUC(0-24) and C(max) in serum, while Ae(0-24 bc) marginally failed to demonstrate BE. After drug administration, a total of 15 subjects reported the occurrence of at least 1 treatment emergent adverse event (AE). All AEs were classified as mild to moderate in severity, and the two treatment groups were equally affected. No serious AEs occurred.

CONCLUSION

The serum PK profiles of inorganic phosphate were almost superimposable following intravenous administration of equimolar doses of test and reference drugs. Thus, we conclude that the two study drugs are essentially similar in terms of serum PK profiles, safety and tolerability.

Lipids for parenteral nutrition in neonates

PURPOSE OF REVIEW

In neonatal intensive care units, the interest and scope for research in the field of intravenous lipids has significantly widened in recent years. This brief review covers the advances in this field in the last 2 years.

RECENT FINDINGS

These include a significant amount of research in evaluating safety and efficacy of novel lipid emulsions that include olive oil or fish oil. Short-term studies involving novel lipid emulsions have documented safety and benefits in terms of reduced inflammation and lipid peroxidation. Fish oil-based lipid emulsions have also been used to prevent and treat parenteral nutrition-induced cholestasis. Other areas of progress include stability studies of all-in-one parenteral nutrition mixtures including lipid emulsions for neonates.

SUMMARY

Since the first soybean oil-based lipid emulsions were introduced 50 years ago, progress has been made in understanding the composition, dose and clinical effects of parenteral lipids in neonatal patients. However there is a paucity of data in terms of definitive head-to-head trials of different novel lipid emulsions evaluating short-term as well as long-term clinically important outcomes including neurodevelopment. Future research is required to determine long-term benefits of novel lipid emulsions for neurological outcome and effects on the immune system.

Influence of the calcium concentration in the presence of organic phosphorus on the physicochemical compatibility and stability of all-in-one admixtures for neonatal use

BACKGROUND

Preterm infants need high amounts of calcium and phosphorus for bone mineralization, which is difficult to obtain with parenteral feeding due to the low solubility of these salts. The objective of this study was to evaluate the physicochemical compatibility of high concentrations of calcium associated with organic phosphate and its influence on the stability of AIO admixtures for neonatal use.

METHODS

Three TPN admixture formulas were prepared in multilayered bags. The calcium content of the admixtures was adjusted to 0, 46.5 or 93 mg/100 ml in the presence of a fixed organic phosphate concentration as well as lipids, amino acids, inorganic salts, glucose, vitamins and oligoelements at pH 5.5. Each admixture was stored at 4 degrees C, 25 degrees C or 37 degrees C and evaluated over a period of 7 days. The physicochemical stability parameters evaluated were visual aspect, pH, sterility, osmolality, peroxide formation, precipitation, and the size of lipid globules.

RESULTS

Color alterations occurred from the first day on, and reversible lipid film formation from the third day of study for the admixtures stored at 25 degrees C and 37 degrees C. According to the parameters evaluated, the admixtures were stable at 4 degrees C; and none of them presented precipitated particles due to calcium/phosphate incompatibility or lipid globules larger than 5 mum, which is the main parameter currently used to evaluate lipid emulsion stability. The admixtures maintained low peroxide levels and osmolarity was appropriate for parenteral administration.

CONCLUSION

The total calcium and calcium/phosphorus ratios studied appeared not to influence the physicochemical compatibility and stability of AIO admixtures.

Doubling Calcium and Phosphate Concentrations in Neonatal Parenteral Nutrition Solutions Using Monobasic Potassium Phosphate

BACKGROUND

Premature infants require high intakes of Ca and P to mimic fetal accretion rates. With the current phosphate salt used, adequate amounts cannot be provided due to the precipitation of Ca and P in TPN solutions.

OBJECTIVE

To compare monobasic potassium phosphate (monobasic regimen) and monobasic plus dibasic potassium phosphate (dibasic regimen) on calcium phosphate solubility in 5 amino acid products, and to determine whether solubility differences observed in these products can be explained by buffering capacity.

METHODS

TPN solutions were prepared according to standard clinical practice. The following amino acid products were used at 3% concentrations: Primene, Vamin N, TrophAmine, Aminosyn-PF, and Travasol. Dextrose 10%, standard electrolytes, heparin, vitamins and trace elements were added. Calcium (as gluconate) and phosphate (as monobasic or dibasic regimen) were added in one-to-one molar ratios from 0-45 mmol/L. Solutions were inspected macroscopically and microscopically for precipitation under three conditions: immediately, 24 h after preparation at room temperature, and 3 h later in a 37 degrees C water bath. Buffering capacity was determined for each amino acid product by titrating with standardized 0.1 M NaOH.

RESULTS

Variations in Ca:P solubility and buffer capacity exist between amino acid solutions. With Primene and Vamin no macroscopic or microscopic precipitation was detected up to 45 mmol/L using monobasic regimen, compared to 25 mmol/L using dibasic regimen with Trophamine. Buffer capacity did not account for the solubility differences observed between the five amino acid products, which were related to the pH of the final solution.

CONCLUSIONS

These data will allow clinicians to double the current concentrations of calcium and phosphate in neonatal TPN solutions using monobasic regimen. Although this is particularly relevant to situations when fluid intake is restricted, the effect of the acid load needs to be investigated in extremely low birth weight infants.

Phosphate supplementation for hypophosphataemia and parenteral nutrition

Routine detection and treatment of acute hypophosphataemia is important in intensive care unit and many other hospitalized patients, but metabolic bone disease and hypophosphataemia are still experienced as a result of parenteral nutrition. A significantly common problem that faces the compounding pharmacist when formulating parenteral nutrition regimens is the difficulty associated with the successful avoidance of calcium phosphate precipitation. Although incorporation of the normal calcium and phosphate requirements into regimens for metabolically stable adults is usually achievable, it can prove impossible in paediatric and neonatal mixtures when using the standard inorganic sources that are currently licensed for use in the UK and USA. In other countries, where organic compounds are routinely available, this problem does not exist.

Inorganic phosphorus reduces hypercalciuria during total parenteral nutrition by enhancing renal tubular calcium absorption

BACKGROUND

Increasing the inorganic phosphorus content of total parenteral nutrition (TPN) formulas has been shown to decrease TPN-induced hypercalciuria in experimental animals and humans. The mechanism of this effect, however, has been uncertain.

METHODS

By using a randomized cross-over design, seven patients on cyclic TPN were given otherwise identical formulas providing either 15 or 45 mmol/d of inorganic phosphorus. Urinary calcium excretion, serum ultrafilterable calcium, filtered calcium load, fractional calcium excretion, urinary cyclic adenosine 5'-monophosphate (cAMP), and serum levels of ionized calcium, parathyroid hormone (PTH), and vitamin D metabolites were determined at the end of each study period.

RESULTS

Urinary calcium excretion was significantly lower when the patients received the higher inorganic phosphorus formula. Increasing the inorganic phosphorus in the TPN formula did not change ultrafilterable calcium or filtered calcium load, but significantly reduced fractional calcium excretion. No differences in serum levels of ionized calcium, PTH, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, or urinary cAMP were observed between treatments.

CONCLUSIONS

These results demonstrate that increasing the inorganic phosphorus content of the TPN formula decreases urinary calcium excretion by increasing renal tubular calcium resorption. This effect is not due to alterations in the PTH-1,25-dihydroxyvitamin D axis, but likely reflects a direct action of inorganic phosphorus on the renal tubules.