Urinary acute kidney injury biomarkers in very low-birth-weight infants on indomethacin for patent ductus arteriosus.

BACKGROUND: Serum creatinine (SCr)- or urine output-based definitions of acute kidney injury (AKI) have important limitations in neonates. This study evaluates the diagnostic value of urinary biomarkers in very low-birth-weight (VLBW) infants receiving indomethacin for closure of a patent ductus arteriosus (PDA). METHODS: Prospective cohort study in 14 indomethacin-treated VLBW infants and 18 VLBW infants without indomethacin as controls. Urinary biomarkers were measured before, during, and after indomethacin administration. RESULTS: Indomethacin therapy was associated with significantly higher SCr concentrations at 36, 84, and 120 h compared to controls. At 36 h, three indomethacin-treated patients met the criteria for neonatal modified Kidney Disease: Improving Global Outcomes (KDIGO) AKI. The product of urinary tissue inhibitor of metalloproteinase-2 and insulin-like growth factor-binding protein 7 ([TIMP-2]•[IGFBP7]) was significantly elevated in the AKI subgroup at 12 h (P < 0.05), hence 24 h earlier than the increase in SCr. Urinary neutrophil gelatinase-associated lipocalin (NGAL) and calprotectin were significantly increased in the indomethacin group at 12 h (P < 0.05), irrespective of fulfillment of the AKI criteria. Urinary kidney injury molecule-1 (KIM-1) was not significantly altered. CONCLUSION: While urinary [TIMP-2]•[IGFBP7] proves valuable for the early diagnosis of neonatal modified KDIGO-defined AKI, elevated urinary NGAL and calprotectin concentrations in indomethacin-treated VLBW infants not fulfilling the AKI criteria may indicate subclinical kidney injury.

Urinary Neutrophil Gelatinase-associated Lipocalin in the evaluation of Patent Ductus Arteriosus and AKI in Very Preterm Neonates: a cohort study.

BACKGROUND: A patent ductus arteriosus (PDA) is frequently found in very preterm neonates and is associated with increased risk of morbidity and mortality. A shunt across a PDA can result in an unfavorable distribution of the cardiac output and may in turn result in poor renal perfusion. Urinary Neutrophil Gelatinase-associated Lipocalin (U-NGAL) is a marker of renal ischemia and may add to the evaluation of PDA. Our primary aim was to investigate if U-NGAL is associated with PDA in very preterm neonates. Secondary, to investigate whether U-NGAL and PDA are associated with AKI and renal dysfunction evaluated by fractional excretion of sodium (FENa) and urine albumin in a cohort of very preterm neonates. METHODS: A cohort of 146 neonates born at a gestational age less than 32 weeks were consecutively examined with echocardiography for PDA and serum sodium, and urine albumin and sodium were measured on postnatal day 3 and U-NGAL and serum creatinine day 3 and 6. AKI was defined according to modified neonatal Acute Kidney Injury Network (AKIN) criteria. The association between U-NGAL and PDA was investigated. And secondly we investigated if PDA and U-NGAL was associated with AKI and renal dysfunction. RESULTS: U-NGAL was not associated with a PDA day 3 when adjusted for gestational age and gender. A PDA day 3 was not associated with AKI when adjusted for gestational age and gender; however, it was associated with urine albumin. U-NGAL was not associated with AKI, but was found to be associated with urine albumin and FENa. CONCLUSIONS: Based on our study U-NGAL is not considered useful as a diagnostic marker to identify very preterm neonates with a PDA causing hemodynamic changes resulting in early renal morbidity. The interpretation of NGAL in preterm neonates remains to be fully elucidated.

Antioxidants and Biomarkers of Oxidative Stress in Preterm Infants with Symptomatic Patent Ductus Arteriosus.

OBJECTIVE: Immature antioxidant and oxygen-sensing mechanisms are involved in the pathogenesis of the patent ductus arteriosus (PDA). We conducted a prospective, observational, pilot study to test the hypothesis that antioxidant activity is low at birth in preterm infants at risk for symptomatic PDA. STUDY DESIGN: Blood and urine samples were collected within 24 to 48 hours of life in 53 preterm infants (≤32 weeks' gestation) who developed early PDA symptoms and in 30 term (≥37 weeks' gestation) control infants. Thirty preterm infants developed hemodynamically significant PDA (hsPDA) and required pharmacologic treatment and/or PDA ligation. For these infants, blood and urine samples were also collected at 24 hours posttreatment. Samples were analyzed for biomarkers of antioxidant activity, oxidative stress, and lipid peroxidation. RESULTS: At 24 to 48 hours after birth, plasma superoxide dismutase (SOD), urinary catalase, and plasma and urinary 8-isoPGF2α were significantly lower in preterm infants who developed hsPDA. Plasma 8-isoPGF2α levels rebounded post-PDA treatment, while urinary prostaglandin E2, plasma and urinary thromboxane B2, and plasma SOD declined. CONCLUSION: The antioxidant status is low in preterm infants at risk for developing hsPDA. SOD may be a key antioxidant regulating functional ductus arteriosus closure. Therefore, low levels may result in persistence of a hsPDA.

Elevated urinary NT-proBNP after pharmacological closure of patent ductus arteriosus in very low birth weight infants.

BACKGROUND: Hemodynamically significant patent ductus arteriosus (hsPDA) complicates the clinical course of preterm infants and contributes to increased morbidity and mortality. NT-proBNP is indicative of the effects of hsPDA on clinical and cardiac status of patients. AIMS: The aim of this study was to evaluate the value of urinary NT-proBNP and NT-proBNP/creatinine ratio in follow-up of hsPDA. STUDY DESIGN: Urinary NT-proBNP and NT-proBNP/creatinine ratio (UNBCR) were measured and correlated with the presence of hsPDA. Measurements were performed in 92 neonates on postnatal days 14 and 28 by ELISA methodology. Of 92 neonates, 22 required therapeutic interventions. RESULTS: Infants treated for hsPDA showed significant higher levels of urinary NT-proBNP and UNBCR on postnatal day 14 whereas similar results were determined on postnatal day 28. Cut-off level of NT-proBNP was 567pg/mL with a sensitivity of 79% and a specificity of 71%. CONCLUSION: Our data showed that NT-proBNP and UNBCR levels as non-invasive and powerful methods in preterm infants may help clinicians to determine the effects of hsPDA on clinical and cardiac status of the patients even with first measurement on day 14.

Urinary NT-proBNP, NGAL, and H-FABP may predict hemodynamic relevance of patent ductus arteriosus in very low birth weight infants.

BACKGROUND: Hemodynamically significant patent ductus arteriosus (hsPDA) is the most common functional cardiovascular disease in preterm infants. The necessity to treat hsPDA can neither be derived solely from clinical nor from echocardiographic criteria. OBJECTIVE: The aim of this study was to establish non-invasive parameters which can differentiate hsPDA from non-hsPDA. METHODS: Urinary protein levels of NT-proBNP, NGAL, and H-FABP were measured and correlated with the necessity of therapy for PDA. In 37 neonates (<1,500 g), urinary protein concentrations were tested on days 0, 2, and 7 by ELISA methodology. Of 37 infants, 12 required therapeutic interventions according to current treatment standards. RESULTS: Infants receiving an intervention for PDA showed significantly higher levels of pro-BNP, NGAL, and H-FABP at all time points except for NT-proBNP on day 0. Infants requiring a second or third course of ibuprofen had significantly higher levels of H-FABP and NGAL. In all samples, the concentration of the three proteins correlated positively with each other. CONCLUSIONS: The present study shows that measurement of urinary proteins is a powerful and non-invasive method to quantify the effect of PDA on systemic perfusion in preterm infants. Furthermore, NGAL and H-FABP may be used to indicate the necessity of pharmacological or surgical treatment of PDA.

Isoprostane levels in urine of preterm newborns treated with ibuprofen for patent ductus arteriosus closure.

Patent ductus arteriosus (PDA) is the most common cardiovascular abnormality of the preterm infant usually treated with ibuprofen (IBU). PDA is strictly related to oxidative stress (OS) in neonates. This study tests the hypothesis that OS occurs in neonates with PDA and that IBU treatment reduces OS. Forty-three preterm babies with gestational age (GA) <33 weeks were studied prospectively. Three urine samples were collected: at time 0 (before starting treatment), time 1 (after pharmacological PDA closure), and time 2 (7 days after the end of treatment) in all patients. OS was studied by measuring urinary isoprostane (IPs) levels. The results showed significant changes in urinary IP levels from time 0 to time 2 (Kruskal-Wallis, p=0.047). Time trend showed a significant decrease in IPs from time 0 to time 1 after IBU therapy (p=0.0067). This decrease was followed by an increase in IPs levels 7 days after treatment. IBU therapy for PDA closure reduced the risk of OS related to free-radical (FR) generation. This antioxidant effect of IBU may be beneficial in preterm babies with PDA who are at high risk for OS.

Urinary aquaporin-2 excretion during ibuprofen or indomethacin treatment in preterm infants with patent ductus arteriosus.

AIM: Water channel AQP2 is the target for vasopressin (AVP) and a major determinant of urinary concentrating capacity. In mature kidneys, prostaglandins counteract the effect of AVP on AQP2 expression at functional sites. We investigated whether disturbances in water homeostasis in infants with patent ductus arteriosus (PDA) treated with prostaglandin inhibitors can be attributed to activation of AQP2. METHODS: In 53 infants with symptomatic PDA (gestational age 24-33 weeks), 30 receiving ibuprofen and 23 indomethacin starting at 2-15 days of life, clinical and biochemical data were collected before treatment and after each dose of the drugs. Urinary AQP2 was determined by dot immunoblotting. RESULTS: Urinary AQP2 level and osmolality were decreased in both groups. Urinary osmolality was overall low and correlated inversely with fluid uptake. In ibuprofen group, there was no correlation of AQP2 level with urinary osmolality. CONCLUSION: There was no AQP2 upregulation in the infants. The low urinary osmolality and dissociation between urinary osmolality and urinary AQP2 level indicate that the fluid retention sometimes observed in PDA infants treated with prostaglandin inhibitors is not caused by increased levels of functional AQP2. Thus, knowledge about the renal physiology of the adult cannot always be transferred to the infant kidney.

Urinary ET-1, AVP and sodium in premature infants treated with indomethacin and ibuprofen for patent ductus arteriosus.

The relative potency and interrelationship between vasoactive and natriuretic mediators are thought to be important in the transition from fetal to neonatal life. The relationship between urinary vasoactive factors and sodium excretion has not been adequately addressed in premature infants receiving indomethacin and ibuprofen for therapy of patent ductus arteriosus. Excretion rates of AVP, ET-1 and sodium were measured in premature infants with RDS receiving indomethacin or ibuprofen. Forty-four RDS premature infants (<34-week gestation) with PDA received either ibuprofen (n=22) in an initial dose of 10 mg/kg followed by two doses of 5 mg/kg each after 24 and 48 h or 3 doses at 12-h intervals of indomethacin (n=24), 0.2 mg/kg, infused continuously over a period of 15 min. Urinary ET-1, AVP and sodium excretion were measured before and after treatment. Indomethacin treatment caused a significant decrease in urinary ET-1 and AVP excretion (UET-1/Ucr 0.14+/-0.01 vs. 0.10+/-0.05 fenton/mmol; P<0.05; 24.42+/-6.18 vs. 12.63+/-3.06 pg/mmol; P<0.05, respectively), along with a significant reduction in urinary sodium (92.1+/-36.1 vs. 64.8+/-35.6 mmol/l; P<0.01), fractional excretion of sodium (6.8+/-37.1 vs. 4.5+/-37.1%; P<0.01) and urinary osmolality (276.2+/-103.9 vs. 226.4+/-60.3 mOsmol/kg; P<0.05). Ibuprofen treatment caused a significant decrease in urinary AVP (UAVP/Ucr 24.5+/-3.4 vs. 16.3+/-2.04 pg/mmol; P<0.01), along with a significant decrease in urinary sodium (78.0+/-8.4 vs. 57.0+/-8.0 mmol/l; P<0.05) and in fractional excretion of sodium (7.5+/-1.3 vs. 3.9+/-3.0%; P<0.05), while it did not modify urinary ET-1 excretion. The association of renal ET-1 and AVP activity with sodium excretion in premature infants treated with indomethacin and ibuprofen supports the hypothesis that these factors may play a role in the physiologic changes in sodium excretion.

Furosemide does not prevent indomethacin-induced renal side effects in preterm infants.

OBJECTIVE: To determine whether furosemide could prevent renal side effects of indomethacin (INN, indometacin) used for the pharmacologic closure of the patent ductus arteriosus (PDA) in preterm infants. METHODS: Thirty-six preterm infants with birth weights < 1750 gm affected by hemodynamically significant PDA were randomly assigned to one of two study groups. Group 1 consisted of 18 infants treated with three doses of indomethacin (0.20 mg/kg every 12 hours); each dose was followed by a dose of furosemide (1 mg/kg). Group 2 consisted of 18 infants treated only with the same doses of indomethacin. Body weight, urine output, glomerular filtration rate (GFR), fractional excretion of sodium (FENa+) and potassium (FEK+), and osmolal and free water clearance were evaluated in both groups before, during, and after treatment. RESULTS: The body weight trend, serum sodium, chloride and potassium concentrations, plasmatic and urinary osmolality were similar during the treatment in both the groups. A significant reduction of urine output (p < 0.01) was detected in group 2 but not in group 1. A significant increase of blood urea nitrogen and serum creatinine was detected at the end of treatment in group 1 compared with group 2. During the treatment, a significantly higher GFR (p < 0.05) was found in group 2 than in group 1. FENa+ and FEK+ were significantly higher (p < 0.05 and p < 0.001, respectively) in group 1 than in group 2 during and after the treatment. The osmolol clearance and free water clearance were significantly higher during and after treatment (p < 0.01 and p < 0.001, respectively) in group 1 than in group 2. CONCLUSIONS: Our findings show that furosemide cannot prevent the indomethacin-induced renal failure, but it does not have any negative influence on its therapeutic effectiveness.

Urinary excretion of mefenamic acid and its metabolites including their esterglucuronides in preterm infants undergoing mefenamic acid therapy.

Urinary excretion of mefenamic acid (MA) and its two oxidative metabolites, M-I (3'-hydroxymethyl derivative) and M-II (3'-carboxyl derivative), and their glucuronides was investigated in preterm infants undergoing MA therapy. MA was given orally at a dose of 2 mg/kg and the dose was repeated every 24 h a maximum of three times. Urine was collected for up to 5 d after the last dose, and MA and the metabolites were determined by a newly developed HPLC. The cumulative amounts of MA and the metabolites excreted in the urine varied from 7 to 46% of the total dose administered, and were less than those reported in adults and children. Significant correlation was observed between the plasma half-life of MA and the cumulative amount of MA and the metabolites excreted in the urine. These results suggest that long plasma half-lives of MA observed in preterm infants are due mainly to low activity of drug metabolizing enzyme(s). In an infant who received the two regimens of MA therapy about 2 weeks apart, the plasma half-life of MA was shortened and the urinary excretion of the MA metabolites including their glucuronides was greatly increased during this period. It is suggested that the activities of both cytochrome P-450(s) and glucuronyltransferase(s) related to MA metabolism rapidly increased during the first month of the infant's life.

Aminoglycoside treatment and renal prostaglandin excretion in premature infants.

During prospective studies of indomethacin treatment of symptomatic patent ductus arteriosus, the question arose whether aminoglycosides alter renal prostaglandin metabolism. Adopting the matched-pair method, we retrospectively analyzed creatinine clearances, urine output and renal PGE2 and PGF2 alpha excretion in preterm infants with and without aminoglycosides. No consistent differences of any of these parameters within the matched pairs could be demonstrated. Indomethacin induced comparable reductions of creatinine clearances in patients with and without aminoglycoside pretreatment. Discrepancies with animal studies and clinical implications of these results are discussed.

Urinary excretion rates of 6-keto-PGF1 alpha in preterm infants recovering from respiratory distress with and without patent ductus arteriosus.

Patency of the ductus arteriosus in preterm infants is mediated by vasodilating prostanoids; however, reliable methods to monitor prostanoid activity or production in preterm infants are lacking. We measured the excretion rates of major and characteristic urinary metabolites of prostacyclin (PGI2), PGE1, and PGE2, 6-keto-PGF1 alpha, and 7 alpha-hydroxy-5,11-diketotetranorprostane-1,16-dioic acid (PGE-M), respectively. Besides these parameters which reflect total body prostanoid turnover and production, the urinary levels of PGE2 and PGF2 alpha, the primary prostaglandins, were measured as an index of renal prostanoid synthesis. There were four study groups. One contained 11 thriving preterm infants; a second, six preterm infants with respiratory distress syndrome (RDS); a third, 30 preterm infants with RDS and patent ductus arteriosus (PDA); and a fourth, nine fullterm infants. All infants with RDS required artificial ventilation. There were no significant differences in PGE-M, PGE2, and PGF2 alpha excretion rates among the various groups; however, a significant increase of the 6-keto-PGF1 alpha excretion rates was observed in the groups of infants with RDS and with and without PDA (P less than 0.01 and P less than 0.02, respectively). Spontaneous (n = 2) or indomethacin-induced (n = 6) closure of PDA was associated with weaning from the respirator and a concomitant drop into the normal and subnormal range of the excretion rates of 6-keto-PGF1 alpha (P less than 0.01) and PGE-M (P less than 0.02).

Indomethacin treatment for symptomatic patent ductus arteriosus: a double-blind control study.

A double-blind control study was designed to determine the efficacy and safety of indomethacin treatment of patients with symptomatic patent ductus arteriosus. Infants with severe respiratory distress syndrome and symptomatic patent ductus arteriosus were eligible for the prospective study if the ratio of left atrial/aortic root diameter remained greater than or equal to 1.3:1 following a 24-hour period of medical management. Thirty-nine eligible infants were randomly assigned to the control or indomethacin group and given 0.2 mg/kg of enteral indomethacin or placebo in a double-blind manner. Second and third doses were administered at 24-hour intervals in phase 1 (17 patients), and at eight-hour intervals in phase 2 (22 patients). The 75% patent ductus arteriosus closure rate with indomethacin treatment in phase 1 was not statistically significant due to a 44% spontaneous closure rate in the control group. In phase 2, however, 85% of the indomethacin group demonstrated patent ductus arteriosus closure vs only 11% in the matched control group (P less than .01). Although no indomethacin side effects occurred in phase 1, in phase 2 indomethacin administration was associated with minimal, but statistically significant, transient impaired renal function and, in three infants (23%), mild upper gastrointestinal bleeding. In summary, enteral administration of three 0.2 mg/kg indomethacin doses at eight-hour intervals thus appears to be a safe and effective alternative to surgical closure.

Urinary excretion of prostaglandin E following the administration of furosemide and indomethacin to sick low-birth-weight infants.

Urinary excretion of prostaglandin E was measured in seven sick low-birth-weight infants. Four had severe hyaline membrane disease and one had chronic bronchopulmonary dysplasia; all received furosemide. Two infants had patent ductus arteriosus and received indomethacin. Following administration of furosemide, urine volume and the excretion rates of sodium and calcium were significantly increased; such changes were not seen following the administration of indomethacin. Prostaglandin E excretion rate was increased from 0.4 +/- 0.04 to 1.3 +/- 0.2 ng/mg Cr (mean +/- SEM) following administration of furosemide, but decreased in two patients following administration of indomethacin. The present results demonstrate that furosemide enhances urinary excretion of prostaglandin E by mechanisms which may reflect an increase in prostaglandin synthesis, a decrease in prostaglandin renal metabolism, or both. Indomethacin, which is a prostaglandin synthetase inhibitor, decreases the urinary excretion of prostaglandin E. These observations suggest that furosemide therapy in patients receiving indomethacin may be ineffective.