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Biomedical subjects

W W Koo

Publications and source records attributed to W W Koo.

70 records · Page 4Linked to original sources
PubMed1982

Skeletal changes in preterm infants.

The skeletal changes in 19 very low birthweight infants (less than 1500 g) were observed from birth to 10 weeks, by means of clinical, biochemical, and radiological techniques. All infants were receiving a supplement of 800 IU vitamin D a day from age 2 weeks. None of the infants showed any specific physical sign of rickets during the period of study. Six infants showed radiological evidence of skeletal demineralisation; 1 of these had severe changes of rickets and 1 had both rickets and fractures. These 6 infants were of shorter gestational periods and lower birthweights than the infants not showing radiological changes. They tended to have more clinical problems and to reach a predetermined volume of feeds (160 ml/kg a day) later than the unaffected infants. Serum alkaline phosphatase values were significantly higher at 5 weeks in the infants with abnormal radiographs than in those without. There were no significant differences between the two groups in relation to serum calcium, inorganic phosphate, 25 hydroxyvitamin D, and immunoreactive parathyroid hormone. The pathogenesis of the skeletal lesions of very low birthweight infants remains unknown.

25-Hydroxyvitamin D 2↗
PubMed1982

Breast milk sodium.

Sodium content was analysed from 360 breast milk samples of 45 mothers who delivered at term and from 206 samples of 22 mothers who delivered preterm in the first 4 weeks postpartum. The sodium content was consistently higher in the milk from mothers of preterm infants. In both groups, the sodium content of the breast milk decreased rapidly for the first 3 days, and then more slowly. After the first week, the daily variation of sodium concentration in the breast milk was minimal. There was no significant statistical difference in the sodium content of breast milk before compared with after feeding nor was there any difference in sodium content from either breast.

Female↗
PubMedDate not supplied

Aluminum in parenteral nutrition solution--sources and possible alternatives.

The extent of aluminum (Al) contamination in parenteral nutrition (PN) solutions for infants is not known. Aluminum was measured in 136 samples from various commercially available components that are used with PN. Results showed Al content varied widely among different components. The same chemical may have a different Al content depending on the manufacturer. However, Al contents were similar among lots from the same manufacturer for the same chemical. Aluminum contamination was arbitrarily classified as high (greater than 500 micrograms Al/liter), intermediate (51-500 micrograms Al/liter) or low (less than or equal to 50 micrograms Al/liter). The high group included most calcium and phosphorus containing salts, 1 multivitamin preparation, folic acid, ascorbic acid and concentrated (25%) albumin. The intermediate group included sodium lactate, potassium phosphates, zinc and chromium chloride, multitrace metal preparation, and 5% plasma protein. The low group included amino acids, sterile water and dextrose water, chloride salts of sodium, potassium, calcium, copper and chromium, sodium phosphates, magnesium sulphate, zinc sulphate, vitamin B12, vitamin K1, 1 multivitamin preparation, soybean oil emulsion and heparinized (2 U/ml) saline. PN solutions made from high Al components may contain up to 300 micrograms Al/liter. Calcium gluconate contributed greater than 80% of the total Al load from PN. Lowering of Al content in calcium gluconate in addition to use of specific low Al components offers the opportunity to significantly lower the Al concentration of the final PN solution and theoretically may achieve an Al content as low as 12 micrograms/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMedDate not supplied

Vitamin D requirement in infants receiving parenteral nutrition.

The adequacy of low dose vitamin D (25 IU/dl) parenteral nutrition (PN) solution was studied in 18 infants. All infants had surgical indications for PN. The birth weights were 2810 +/- 135 g and gestational ages 37.4 +/- 0.5 wk (mean +/- SEM). Duration of study ranged from 5 to 175 days. Thirteen infants were studied for up to 6 weeks and five infants for 71 to 175 days. Results showed that studied infants maintained growth along normal percentiles for weight, length, and head circumference. Vitamin D status as indicated by serum 25 hydroxyvitamin D (25 OHD) rose from 15 +/- 1.9 ng/ml to 26 +/- 2.8 ng/ml, mean +/- SEM (p less than 0.001) after 9 days, and remained normal up to 6 months. Five infants with biochemical liver dysfunction also had normal serum 25 OHD concentrations, indicating the hepatic 25 hydroxylation process was not severely impaired. Serum total and ionized calcium, phosphorus, and vitamin D-binding protein concentrations were normal. Serum magnesium was mildly elevated in five infants (2.6 to 3 mg/dl) on one occasion and resolved spontaneously. Serum alkaline phosphatase (AP) concentrations rose above baseline values in 12 of 17 infants, but remained within normal range (less than 400 IU/liter at 30 degrees C). Another infant with markedly elevated AP values died from liver dysfunction. Radiographs of the forearms were normal except for marked demineralization in one infant in spite of normal 25 OHD concentrations. We conclude that 25 IU vitamin D/dl of nutrient infusate is adequate to maintain normal vitamin D status, as indicated by normal serum 25 OHD concentrations in infants receiving PN for as long as 6 months.

Alkaline Phosphatase↗
PubMedDate not supplied

Aluminum contamination of infant formulas.

This study aims to determine the extent of aluminum (Al) contamination in whole milk, milk formulas, and other nutrient products commonly used for infants. Similar products from different manufacturers and different lots were measured for Al using electrothermal atomic absorption technique. Aluminum measurements were made directly from the samples or after reconstitution or dilution with Al-free water. Aluminum content was lowest (less than 50 micrograms/liter) in human milk, whole cow milk, and products that appear to require minimal manufacture processing and have few additives such as skim milk, cow milk with 2% fat, bottled glucose water, and sterile water. Highest Al levels (up to 2346 micrograms/liter) were found in highly processed and modified formulas including soy formula, preterm infant formula, and formulas for specific metabolic disorders. Aluminum content of humanized cow milk formula and bottled glucose-electrolyte solution were between the two ranges and usually less than 400 micrograms/liter. There were no significant differences in Al content of similar products from different manufacturers. Liquid formula stored in glass bottles has highest Al content compared to that stored in steel cans or powder preparation of the same product (p less than 0.05). Thus there are marked differences in Al loading depending on the type of formula, whether it is a powder or liquid preparation and the type of storage container. We speculate that raw materials such as soybean, additives such as calcium and phosphorus, manufacturing processes and storage containers are potential sources of contamination of infant formulas.

Aluminum↗
PubMedDate not supplied

Response of preterm infants to aluminum in parenteral nutrition.

Twenty-five preterm infants with birth weights (BW) 540 to 2280 g (20 with birth weight less than 1500 g) and gestational ages 24 to 37 weeks, were studied to determine the response to 2 levels of aluminum (Al) loading from currently unavoidable contamination of various components of parenteral nutrition (PN) solution. High Al loading group (H) received solutions with measured Al content of 306 +/- 16 micrograms/liter and low A1 loading group (L) received solutions with 144 +/- 16 micrograms A1/liter. Urine Al:Creatinine (Al:Cr) ratios (micrograms:mg) became elevated and significantly higher in H (1.6 +/- 0.38 vs 0.5 +/- 0.1, p less than 0.05) at the third sampling point (mean 19 days). Serum Al concentrations were highest at onset in both groups and stabilized with study but remained consistently higher than the normal median of 18 micrograms/liter. Calculated urine Al excretion were consistently low and were 34 +/- 6% vs 28 +/- 5% in the H and L groups, respectively. One infant in the L group who died 39 days after termination of above study showed the presence of A1 in bone trabeculae and the presence of excessive unmineralized osteoid along the trabeculae. We conclude that small preterm infants are able to increase urine Al excretion with increased Al load. However urine Al excretion is incomplete with bone deposition of Al and persistently elevated serum Al concentrations.

Aluminum↗
PubMedDate not supplied

Pharmacokinetics of ampicillin during parenteral nutrition.

Seven healthy volunteers (four males, 20-28 years) were studied to determine the effect of parenteral nutrition (PN) on ampicillin clearance. Each volunteer received intravenous infusions of 1 liter of PN (3.75% amino acid and 10% dextrose) alternating with 1 liter of 10% dextrose (containing all additives as PN except for calcium and phosphorus); and a meal containing similar fluid volume, caloric, protein, and sodium content as the PN solution. Ampicillin (250 mg) was given intravenously 2 hr after commencement of each intravenous solution and 4 hr after the meal. During PN infusion, the mean (+/- SE) glomerular filtration rate (GFR) as indicated by creatinine clearance was 125 +/- 18 ml/min; ampicillin pharmacokinetic data included area under the serum ampicillin concentration-time curve of 899 +/- 118 micrograms min/ml, terminal elimination half life of 37 +/- 4.3 min, volume of distribution at steady state of 11.9 +/- 1.6 liter, total body clearance of 4.7 +/- 0.6 ml/min/kg, renal clearance of 3.8 +/- 0.5 ml/min/kg, and 82 +/- 6.7% of the ampicillin administered was excreted in urine over 10 hr. The results were not significantly altered by different nutrient regimens or the order of infusion of intravenous solutions. We conclude that the use of PN is unlikely to affect the pharmacokinetics of ampicillin provided the renal functions including GFR, remain unchanged.

Adult↗
PubMedDate not supplied

Osmotic load from glucose polymers.

Glucose polymer is a carbohydrate source with variable chain lengths of glucose units which may result in variable osmolality. The osmolality of two commercial glucose polymers was measured in reconstituted powder infant formulas, and the change in osmolality of infant milk formulas at the same increases in energy density (67 kcal/dL to 81 and 97 kcal/dL) from the use of additional milk powder or glucose polymers was compared. All samples were prepared from powders (to nearest 0.1 mg), and osmolality was measured by freezing point depression. For both glucose polymers the within-batch variability of the measured osmolality was less than 3.5%, and between-batch variability of the measured osmolality was less than 9.6%. The measured osmolality varies linearly with energy density (p less than 0.001) and was highest in infant formula reconstituted from milk powder alone. However, there exist significant differences in the measured osmolality between different glucose polymer preparations. At high energy densities (greater than or equal to 97 kcal/dL), infant milk formulas prepared with milk powder alone or with the addition of certain glucose polymer preparation may have high osmolality (greater than or equal to 450 mosm/kg) and theoretically predispose the infant to complications of hyperosmotic feeds.

Glucose↗
PubMedDate not supplied

Parenteral nutrition-related bone disease.

Parenteral nutrition (PN)-related bone disease remains a problem in patients of all ages. Understanding of the pathogenesis of PN-related bone disease is complicated by the effect of underlying illnesses, therapeutic interventions, and pre-existing nutrition deficiencies before the initiation of PN therapy. Interrelation of various nutrients, for example, calcium, phosphorus, and vitamin D, in their effects on bone mineralization, demands simultaneous assessment of the role of multiple nutrients and increases the difficulty in defining the role of a single nutrient in the development of bone disease. However, recent reports indicate that there exist a number of factors important in the development of PN-related bone disease and some factors such as increased mineral requirement are unique to growing infants whereas other factors such as aluminum toxicity may be common to both adult and pediatric populations. Nonnutritional factors, including chronic use of potent loop diuretics and altered acid-base status, can affect urine mineral loss, cell metabolism, and bone mineralization, particularly in small, preterm infants. Current evidence indicates that the cause of PN-related bone disease is multifactorial, and the prevention of PN-related bone disease awaits better delineation of the exact sequence of pathogenic events.

Aluminum↗
PubMedDate not supplied

Fractures and rickets in very low birth weight infants: conservative management and outcome.

Fractures and rickets (F/R) often occur in very low birth weight (VLBW less than 1500 g) infants who are acutely ill. However, there are no prospective longitudinal studies of the clinical course of F/R in these infants. In a prospective study of 78 VLBW infants during the first year after birth, radiographic evidence of healing and remodeling of F/R was noted in affected infants (n = 25) concurrent with increased enteral intake and physical growth, and regardless of whether specific orthopedic treatment was initiated. Skeletal maturation as indicated by the development of ossification centers at the wrists was directly related to weight gain, and was similar to term infants by 1 year. No infant had skeletal deformities on follow-up examination. We suggest that VLBW infants with F/R can be managed "conservatively," with emphasis on nutritional intake to achieve weight gain.

Bone Development↗
PubMedDate not supplied

Parenteral nutrition for infants: effect of high versus low calcium and phosphorus content.

Calcium (Ca) and phosphorus (P) homeostasis were determined in 18 infants (birth weight, 2,810 +/- 135 g; gestational age, 37.4 +/- 0.5 weeks; mean +/- SEM) who received high or low Ca and P content (Ca, P) parenteral nutrition (PN) with a fixed, low dose of vitamin D (25 IU/dl). Nine infants were randomized into low (standard) Ca, P (20 mg Ca and 15.5 mg P/dl) and nine into high Ca, P (60-80 mg Ca and 46.5-62 mg P/dl) PN, and then were studied for up to 6 weeks. The high Ca, P group had stable serum 1,25 dihydroxyvitamin D [1,25(OH)2D], which consistently remained within the normal range (less than 116 pg/ml). Tubular reabsorption of phosphorus (TRP) also was stable and remained consistently less than 90%. The low Ca, P group had elevated and higher 1,25(OH)2D (p = 0.03) than the high Ca, P group. The mean serum 1,25(OH)2D concentration rose from 32 to 112, 115, and 133 pg/ml over a period of 6 weeks. TRP also was higher (p = 0.02) and remained consistently greater than 90%. There were no significant differences between groups in serum parathyroid hormone, calcitonin, Ca, Mg, P, alkaline phosphatase, vitamin D binding protein, and 25 hydroxyvitamin D concentrations; urine Ca/creatinine and Mg/creatinine ratios, and fractional excretion of sodium (Na). Thus, a "high" Ca (60 mg/dl) and P (46.5 mg/dl) content in PN solutions can result in stable serum 1,25(OH)2D and TRP, presumably reflecting minimal stress to Ca and P homeostatic mechanisms without further increase in urinary Ca excretion.

Calcium↗