Theophylline prevents the hypoxemia-induced renal hemodynamic changes in rabbits

Diuretics in neonatology: a narrative review and update

Diuretics are medications that promote the excretion of water and electrolytes. They are primarily used in the management and treatment of states of inappropriate salt and water retention. Diuretics represent one of the most common classes of drugs administered to sick neonates, the more so in very low birth weight infants. Diuretic drugs, especially loop diuretics, are often administered in the neonatal intensive care unit as off-label medications. This is the case for a variety of clinical situations, in which an increase in sodium excretion is not the primary goal of treatment (transitory tachypnoea of the newborn at term, hyaline membrane disease, patent ductus arteriosus of preterm infants). Thiazides and furosemide are widely used to treat preterm infants with oxygen-dependent chronic lung disease, despite a lack of data on beneficial effect of long-term therapy on pulmonary function or clinical outcome. This article reviews the mechanism of action, indications, administration, posology, adverse effects and contraindications of diuretics in newborn infants. Based on the most recent information available in the literature, we will discuss data supporting (or questioning) the use of diuretic in specific neonatal diseases. Research priorities over this issue will be briefly presented.

The Babyccino: The Role of Caffeine in the Prevention of Acute Kidney Injury in Neonates-A Literature Review

Acute kidney injury (AKI) in neonates is associated with increased morbidity and mortality. Theophylline (a methylxanthine) has been shown to prevent neonatal AKI but is seldom used due to its unfavorable profile. Caffeine, another methylxanthine, is utilized ubiquitously to treat apnea of prematurity, but there are no randomized trials evaluating its efficacy in preventing neonatal AKI. This literature review aims to summarize the existing research pertaining to the relationship between caffeine and neonatal AKI. The review was conducted using Pubmed, Embase, Google Scholar, and Cochrane. Inclusion criteria incorporated empirical studies, being published in English, and being available electronically. All eight studies identified were included. Seven studies found caffeine-exposed premature neonates had lower rates of AKI than caffeine-unexposed neonates. Four found reduced AKI severity with caffeine exposure. One study included term neonates and did not find a difference in the AKI rate between caffeine-exposed and non-exposed babies. Limitations include exclusively observational studies, short study periods, heterogenous definitions of prematurity, and a lack of assessment of dose-effect relationships. In conclusion, premature neonates exposed to caffeine appear to have lower rates and potentially less severe AKI. Further research is needed before caffeine can be considered for use in the primary prevention of neonatal AKI.

Use of Aminophylline to Reverse Acute Kidney Injury in Pediatric Critical Care Patients

OBJECTIVE

Acute kidney injury (AKI) is a complication encountered in 18% to 51% of pediatric critical care patients admitted for treatment of other primary diagnoses and is an independent risk factor for increased morbidity and mortality. Aminophylline has shown promise as a medication to treat AKI, but published studies have shown conflicting results. Our study seeks to assess the reversal of AKI following the administration of aminophylline in critically ill pediatric patients.

METHODS

We performed a single-institution retrospective chart review of pediatric inpatients who were diagnosed with AKI and subsequently treated with non-continuous dose aminophylline between January 2016 and December 2018. Data were collected beginning 2 days prior to the initial dose of aminophylline through completion of the 5-day aminophylline course.

RESULTS

Nineteen therapies among 17 patients were included in analysis. Twelve of the therapies resulted in resolution of AKI during the study period. We observed urine output increase of 19% (p = 0.0063) on the day following initiation of aminophylline therapy in the subset of patients whose AKI resolved. Trends toward decreased serum creatinine and lower inotropic support were also noted.

CONCLUSIONS

Based on these findings, aminophylline could be considered a potentially effective medication for use as rescue therapy in critically ill children with AKI. Limitations include small study population and retrospective nature. Further research in this area with a larger study population and a randomized control trial would allow for better characterization of the efficacy of aminophylline in reversal of AKI.

Use of diuretics in the neonatal period

The use of diuretics is extremely frequent in sick neonates, the more so in very premature newborn infants. The use of diuretics in patients whose kidney function is immature necessitates a thorough knowledge of renal developmental physiology and pathophysiology. This review presents the basic aspects of body fluid homeostasis in the neonate, discusses the development of kidney function, and describes the mechanisms involved in electrolyte and water reabsorption along the nephron. Diuretics are then classified according to the site of their action on sodium reabsorption. The use of diuretics in sodium-retaining states, in oliguric states, in electrolyte disorders, and in arterial hypertension, as well as in a few specific disorders, is presented. Common and specific adverse effects are discussed. Recommended dosages for the main diuretics used in the neonatal period are given. New developments in diuretic therapy are briefly mentioned.

Aminophylline for renal protection in neonatal hypoxic-ischemic encephalopathy in the era of therapeutic hypothermia

BACKGROUND

Neonates with hypoxic-ischemic encephalopathy (HIE) frequently develop acute kidney injury (AKI). Aminophylline has been shown to reduce severe renal dysfunction in neonates after perinatal asphyxia. However, the effect of aminophylline on renal function in neonates undergoing hypothermia has not been studied.

METHODS

A single-center, retrospective chart review of neonates cooled for moderate/severe HIE who received aminophylline for AKI was conducted to assess changes in urine output (UOP) and serum creatinine (SCr). Comparisons were also made to control neonates matched for hours of life who were cooled but unexposed to aminophylline.

RESULTS

Sixteen neonates cooled for HIE received aminophylline starting at 25 ± 14 h of life. Within 12 h of starting aminophylline, UOP increased by 2.6 ± 1.9 mL/kg/h. SCr declined by 0.4 ± 0.2 mg/dL in survivors over the first 4 days. When compared to control neonates, UOP increase was greater in the aminophylline group (p < 0.001). SCr declined in survivors in both groups, although baseline SCr was higher in the aminophylline group.

CONCLUSIONS

Aminophylline use in neonates with HIE undergoing hypothermia was associated with an increase in UOP and a decline in SCr. A randomized trial will be needed to establish a potential renal protective role of aminophylline.

IMPACT

The renal protective effect of aminophylline in neonates with HIE has not yet been studied in the context of therapeutic hypothermia. Aminophylline exposure in neonates cooled for HIE was associated with increased UOP and a similar decline in SCr when compared to control infants unexposed to aminophylline. Improved renal function after receiving aminophylline in this observational cohort study suggests the need for future randomized trials to establish the potential benefit of aminophylline in the HIE population undergoing hypothermia.

Theophylline dosing and pharmacokinetics for renal protection in neonates with hypoxic-ischemic encephalopathy undergoing therapeutic hypothermia

BACKGROUND

Theophylline, a non-selective adenosine receptor antagonist, improves renal perfusion in the setting of hypoxia-ischemia and may offer therapeutic benefit in neonates with hypoxic-ischemic encephalopathy (HIE) undergoing hypothermia. We evaluated the pharmacokinetics and dose-exposure relationships of theophylline in this population to guide dosing strategies.

METHODS

A population pharmacokinetic analysis was performed in 22 neonates with HIE undergoing hypothermia who were part of a prospective study or retrospective chart review. Aminophylline (intravenous salt form of theophylline) was given per institutional standard of care for low urine output and/or rising serum creatinine (5 mg/kg intravenous (i.v.) load then 1.8 mg/kg i.v. q6h). The ability of different dosing regimens to achieve target concentrations (4-10 mg/L) associated with clinical response was examined.

RESULTS

Birth weight was a significant predictor of theophylline clearance and volume of distribution (p < 0.05). The median half-life was 39.5 h (range 27.2-50.4). An aminophylline loading dose of 7 mg/kg followed by 1.6 mg/kg q12h was predicted to achieve target concentrations in 84% of simulated neonates.

CONCLUSIONS

In neonates with HIE undergoing hypothermia, theophylline clearance was low with a 50% longer half-life compared to full-term normothermic neonates without HIE. Dosing strategies need to consider the unique pharmacokinetic needs of this population.

IMPACT

Theophylline is a potential renal-protective therapy in neonates with HIE undergoing therapeutic hypothermia; however, the pharmacokinetics and dose needs in this population are not known. Theophylline clearance was low in neonates with HIE undergoing therapeutic hypothermia with a 50% longer half-life compared to full-term normothermic neonates without HIE. As theophylline is advanced in clinical development, dosing strategies will need to consider the unique pharmacokinetic needs of neonates with HIE undergoing therapeutic hypothermia.

Peri-transplant aminophylline in pediatric kidney transplant recipients of donation after brain death: a double-blinded placebo-controlled randomized clinical trial

BACKGROUND

During kidney transplantation, the transplanted kidney undergoes ischemia reperfusion injury, with adenosine being a major mediator. This study aimed to assess whether aminophylline, an adenosine receptor antagonist, improves early graft function and reduces incidence of delayed graft function (DGF) and slow graft function (SGF).

METHODS

Single center, double-blinded, placebo-controlled randomized clinical trial. Pediatric patients admitted for renal transplantation from donation after brain death donors were randomized into a treatment arm receiving aminophylline and a placebo arm receiving normal saline infusions. Primary outcome was estimated glomerular filtration rate (eGFR) at 5 days post-transplant. Secondary outcomes were rates of DGF/SGF and urinary neutrophil gelatinase-associated lipocalin (NGAL) levels.

RESULTS

Twenty-three patients were randomized to aminophylline and 27 to placebo. There was no difference in day 5 eGFR, rate of DGF/SGF, or urine NGAL/Creatinine level between aminophylline vs. placebo arm (eGFR 67.39 ± 38.9 ml/min/1.73m² vs. 80.48 ± 52.1 ml/min/1.73m²p = 0.32; DGF/SGF 5/23 (21.7%) vs. 3/27 (11.1%) p = 0.31; urine NGAL/creatinine 300.5 ng/mg IQR 105.5-1464.5 ng/mg vs. 425.4 ng/mg IQR 140.3-1126.2 ng/mg, p = 0.95; respectively). At 12 months, there was 100% patient survival and 98% graft survival. eGFR at 12 months was similar between the two arms.

CONCLUSIONS

There was no benefit in peri-transplant aminophylline administration. Our results are limited by small sample size, since sample calculations were based on primary outcome of day 5 eGFR and low rate of DGF/SGF, which may have precluded us from demonstrating efficacy. Further clinical studies are necessary to determine any benefit of aminophylline in kidney transplant recipients, particularly from high-risk donors.

Effect of Aminophylline in Preventing Renal Dysfunction among Neonates with Prenatal Asphyxia: A Clinical Trial

BACKGROUND

As there are different views on the effects of aminophylline on neonatal renal function, we intended to observe the effects of aminophylline on renal dysfunction in neonates with prenatal asphyxia.

METHODS

This randomized trial was conducted in the Obstetrics and Gynecology Hospital, Tehran, Iran, from June 2016 to May 2017, in neonates with moderate to severe asphyxia during birth. Fifty-six neonates were divided randomly into two groups. The intervention group received one dose of 5mg/kg slow intravenous aminophylline injection and the placebo group received 2 mL/kg of intravenous 10% solution of dextrose saline during the first hour of life. They were monitored and compared for renal functional indices, electrolytes, and complications of asphyxia during the three days of life.

RESULTS

The mean of Cr (37.9 ± 8.8 vs 38.5 ± 9.4 and 20.8 ± 4.8 vs 30.1 ± 5.2 μmol/L), GFR (21.55 ± 4.7 vs 20.25 ± 4.4 and 30.8 ± 7.1 vs 20.1 ± 6.5 mL/minute/1.73 m²), Na (135.1 ± 12.4 vs134.5 ± 11.2 and 128.9 ± 11.5 vs 134.2 ± 10.9 mEq/L), and urine output (98.2 ± 25 vs 96.8 ± 23 and 148.7 ± 35 vs 108.8 ± 20 cc) were in the aminophylline treated and placebo group on the 1st and 3rd days, respectively. The mean difference of Cr (-9.3 (-8.9; -9.7) μmol/L); (P = 0.02), GFR (10.7 (10.1; 11.3) mL/minute/1.73 m²) (P = 0.009), Na (-5.3 (-5.9; -4.7) mEq/L) (P = 0.002), and urine volume (39.9 (24.9; 54.9) cc) (P = 0.001) presented statistically significant differences on the third day between the intervention and placebo group.

CONCLUSION

Aminophylline was effective in preventing renal dysfunction in neonates with asphyxia. Neonates who received aminophylline indicated a significant improvement in GFR and urine output on the first day of life.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), NCT02443389.

Theophylline and aminophylline for prevention of acute kidney injury in neonates and children: a systematic review

OBJECTIVE

To compare the efficacy and safety of theophylline or aminophylline for prevention of acute kidney injury (AKI) in neonates and children.

DESIGN

Systematic review and meta-analysis with application of Grading of Recommendations, Assessment, Development and Evaluation system.

DATA SOURCES

PubMed/MEDLINE, Embase, Google Scholar and Cochrane renal group were searched from 1970 to May 2018.

ELIGIBILITY CRITERIA

Randomised clinical trials and quasi-randomised trials comparing the efficacy and safety of prophylactic theophylline or aminophylline for prevention of AKI in neonates and children were included. The primary outcomes were: incidence of AKI, serum creatinine levels and all-cause mortality.

RESULTS

A total of nine trials were included in the qualitative synthesis. Six trials including 436 term neonates with birth asphyxia who received a single dose of theophylline were finally included in the meta-analysis. The pooled estimate showed 60% reduction in the incidence of AKI in neonates with severe birth asphyxia (RR: 0.40; 95% CI 0.3 to 0.54; heterogeneity: I²=0%) (moderate quality evidence), decrease in serum creatinine over days 2-5 (very low to low quality evidence) without significant difference in all-cause mortality (RR: 0.88; 95% CI 0.52 to 1.50; heterogeneity: I²=0%) (very low-quality evidence). A significant difference in the negative fluid balance, increase in GFR and decrease in urinary β2 microglobulin was seen in favour of theophylline.

CONCLUSION AND RELEVANCE

A single dose of prophylactic theophylline helps in prevention of AKI/severe renal dysfunction in term neonates with severe birth asphyxia (moderate quality evidence) without increasing the risk of complications and without affecting all-cause mortality (very low-quality evidence).

TRIAL REGISTRATION NUMBER

CRD 42017073600.

Incidence and Risk Factors of Early Onset Neonatal AKI

BACKGROUND AND OBJECTIVES

Neonatal AKI is associated with poor short- and long-term outcomes. The objective of this study was to describe the risk factors and outcomes of neonatal AKI in the first postnatal week.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The international retrospective observational cohort study, Assessment of Worldwide AKI Epidemiology in Neonates (AWAKEN), included neonates admitted to a neonatal intensive care unit who received at least 48 hours of intravenous fluids. Early AKI was defined by an increase in serum creatinine >0.3 mg/dl or urine output <1 ml/kg per hour on postnatal days 2-7, the neonatal modification of Kidney Disease: Improving Global Outcomes criteria. We assessed risk factors for AKI and associations of AKI with death and duration of hospitalization.

RESULTS

Twenty-one percent (449 of 2110) experienced early AKI. Early AKI was associated with higher risk of death (adjusted odds ratio, 2.8; 95% confidence interval, 1.7 to 4.7) and longer duration of hospitalization (parameter estimate: 7.3 days 95% confidence interval, 4.7 to 10.0), adjusting for neonatal and maternal factors along with medication exposures. Factors associated with a higher risk of AKI included: outborn delivery; resuscitation with epinephrine; admission diagnosis of hyperbilirubinemia, inborn errors of metabolism, or surgical need; frequent kidney function surveillance; and admission to a children's hospital. Those factors that were associated with a lower risk included multiple gestations, cesarean section, and exposures to antimicrobials, methylxanthines, diuretics, and vasopressors. Risk factors varied by gestational age strata.

CONCLUSIONS

AKI in the first postnatal week is common and associated with death and longer duration of hospitalization. The AWAKEN study demonstrates a number of specific risk factors that should serve as "red flags" for clinicians at the initiation of the neonatal intensive care unit course.

Renal Saturation and Acute Kidney Injury in Neonates with Hypoxic Ischemic Encephalopathy Undergoing Therapeutic Hypothermia

OBJECTIVE

To investigate the range of renal near-infrared spectroscopy (NIRS) measures in neonates undergoing therapeutic hypothermia for hypoxic ischemic encephalopathy (HIE) and to determine the association between renal NIRS measures and the development of acute kidney injury (AKI).

STUDY DESIGN

A retrospective chart review was conducted of neonates with moderate to severe HIE who received therapeutic hypothermia at a tertiary care center from 2014 to 2016. Neonates had routine continuous NIRS monitoring of cerebral and renal saturation (Rsat) as part of their clinical care for 72 hours of cooling and until 24 hours after rewarming. The outcome of AKI was defined by an abnormal rate of decline of serum creatinine over the first 5 days of life. Mixed effects models determined the association between renal NIRS measures and AKI over time.

RESULTS

Of 38 neonates with HIE undergoing cooling, 15 (39%) developed AKI. Rsat was lower than cerebral saturation during cooling (P < .01), but Rsat increased over time after rewarming, while renal oxygen extraction levels decreased (P < .0001). Neonates with AKI had higher Rsat levels (P < .01) compared with those without AKI after 24 hours of life. Using receiver operating characteristic curves, Rsat >75% by 24-48 hours predicted AKI with a sensitivity of 79% and specificity of 82% (area under the receiver operating characteristic curve = 0.76).

CONCLUSIONS

Throughout cooling, neonates with AKI had higher Rsat measures than those without AKI. These differences may reflect lower oxygen extraction by the injured kidney. NIRS monitoring of Rsat may identify neonates with HIE at risk of developing AKI.

Association Between Early Caffeine Citrate Administration and Risk of Acute Kidney Injury in Preterm Neonates: Results From the AWAKEN Study

Importance

Acute kidney injury (AKI) occurs commonly in preterm neonates and is associated with increased morbidity and mortality.

Objectives

To examine the association between caffeine citrate administration and AKI in preterm neonates in the first 7 days after birth and to test the hypothesis that caffeine administration would be associated with reduced incidence and severity of AKI.

Design, Setting, and Participants

This study was a secondary analysis of the Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) study, a retrospective observational cohort that enrolled neonates born from January 1 to March 31, 2014. The dates of analysis were October 2016 to December 2017. The setting was an international, multicenter cohort study of neonates admitted to 24 participating level III or IV neonatal intensive care units. Participants met the original inclusion and exclusion criteria of the AWAKEN study. Additional exclusion criteria for this study included participants greater than or equal to 33 weeks' gestation at birth, admission after age 7 days, use of theophylline in the neonatal intensive care unit, or lack of data to define AKI. There were 675 preterm neonates available for analysis.

Exposure

Administration of caffeine in the first 7 days after birth.

Main Outcomes and Measures

The primary outcome was the incidence of AKI (based on the modified neonatal Kidney Disease: Improving Global Outcomes [KDIGO] definition) in the first 7 days after birth. The hypothesis that caffeine administration would be associated with reduced AKI incidence was formulated before data analysis.

Results

The study cohort (n = 675) was 55.4% (n = 374) male, with a mean (SD) gestational age of 28.9 (2.8) weeks and a mean (SD) birth weight of 1285 (477) g. Acute kidney injury occurred in 122 neonates (18.1%) in the first 7 days after birth. Acute kidney injury occurred less frequently among neonates who received caffeine than among those who did not (50 of 447 [11.2%] vs 72 of 228 [31.6%], P < .01). After multivariable adjustment, administration of caffeine remained associated with reduced odds of developing AKI (adjusted odds ratio, 0.20; 95% CI, 0.11-0.34), indicating that for every 4.3 neonates exposed to caffeine one case of AKI was prevented. Among neonates with early AKI, those receiving caffeine were less likely to develop stage 2 or 3 AKI (adjusted odds ratio, 0.20; 95% CI, 0.12-0.34).

Conclusions and Relevance

Caffeine administration in preterm neonates is associated with reduced incidence and severity of AKI. Further studies should focus on the timing and dosage of caffeine to optimize the prevention of AKI.

The novel combination of theophylline and bambuterol as a potential treatment of hypoxemia in humans

Hypoxemia can be life-threatening, both acutely and chronically. Because hypoxemia causes vascular dysregulation that further restricts oxygen availability to tissue, it can be pharmacologically addressed. We hypothesized that theophylline can be safely combined with the β2-adrenergic vasodilator bambuterol to improve oxygen availability in hypoxemic patients. Ergogenicity and hemodynamic effects of bambuterol and theophylline were measured in rats under hypobaric and normobaric hypoxia (12% O₂). Feasibility in humans was assessed using randomized, double-blind testing of the influence of combined slow-release theophylline (300 mg) and bambuterol (20 mg) on adverse events (AEs), plasma K⁺, pulse, blood pressure, and drug interaction. Both drugs and their combination significantly improved hypoxic endurance in rats. In humans, common AEs were low K⁺ (<3.5 mmol/L; bambuterol: 12, theophylline: 4, combination: 13 episodes) and tremors (10, 0, 14 episodes). No exacerbation or serious AE occurred when drugs were combined. A drop in plasma K⁺ coincided with peak bambuterol plasma concentrations. Bambuterol increased heart rate by approximately 13 bpm. Drug interaction was present but small. We report promise, feasibility, and relative safety of combined theophylline and bambuterol as a treatment of hypoxemia in humans. Cardiac safety and blood K⁺ will be important safety endpoints when testing these drugs in hypoxemic subjects.

Comparison of Intraoperative Aminophylline Versus Furosemide in Treatment of Oliguria During Pediatric Cardiac Surgery

OBJECTIVES

To determine if intraoperative aminophylline was superior to furosemide to prevent or attenuate postoperative cardiac surgery-associated acute kidney injury.

DESIGN

Single-center, historical control, retrospective cohort study.

SETTING

PICU, university-affiliated children's hospital.

PATIENTS

Children with congenital heart disease in PICU who received furosemide or aminophylline to treat intraoperative oliguria.

INTERVENTIONS

Intraoperative oliguria was treated either with furosemide (September 2007 to February 2012) or with aminophylline (February 2012 to June 2013). The postoperative 48 hours renal outcomes of the aminophylline group were compared with the furosemide group. The primary outcomes were acute kidney injury and renal replacement therapy use at 48 hours postoperatively. Surgical complexity was accounted for by the use of Risk Adjustment for Congenital Heart Surgery-1 score.

MEASUREMENTS AND MAIN RESULTS

The study involves 69 months of observation. There were 200 cases younger than 21 years old reviewed for this study. Eighty-five cases (42.5%) developed acute kidney injury. The aminophylline group patients produced significantly more urine (mL/kg/hr) during the first 8 hours postoperatively than furosemide patients (5.1 vs 3.4 mL/kg/hr; p = 0.01). The urine output at 48 hours postoperatively was similar between the two groups. There was no difference in acute kidney injury incidence at 48 hours between the aminophylline and furosemide groups (38% vs 47%, respectively; p = 0.29). Fewer aminophylline group subjects required renal replacement therapy compared to the furosemide group subjects (n = 1 vs 7, respectively; p = 0.03). In the multi-variant predictive model, intraoperative aminophylline infusion was noted as a negative predictive factor for renal replacement therapy, but not for cardiac surgery-associated acute kidney injury.

CONCLUSION

The intraoperative use of aminophylline was more effective than furosemide in reversal of oliguria in the early postoperative period. There were less renal replacement therapy-requiring acute kidney injury in children in the aminophylline group. Future prospective studies of intraoperative aminophylline to prevent cardiac surgery-associated acute kidney injury may be warranted.

Acute Renal Failure in the Neonate

Acute renal failure (ARF) is a common disorder in high-risk neonates. ARF may be oliguric or nonoliguric, the latter having a better prognosis. Risk factors for ARF include prematurity, respiratory and vascular disorders, heart failure, congenital uropathies, and the use of nephrotoxic drugs. Chemical analysis of urine and ultrasounds help differentiate the nature and the type of ARF: prerenal, intrinsic, or postrenal. Conservative management of prerenal forms of ARF consists in carefully restoring cardiac output and controlling fluid and electrolyte balances. Early relief of obstruction is mandatory in severe postrenal forms of ARF. Renal replacement therapy is often necessary when ARF is secondary to intrinsic renal damage: peritoneal dialysis is the treatment of choice. Hemodialysis and continuous venovenous hemofiltration may be used in specific cases. Overall prognosis of ARF depends on the nature and severity of the renal injury that has led to renal failure.

Caffeine Exposure and Risk of Acute Kidney Injury in a Retrospective Cohort of Very Low Birth Weight Neonates

OBJECTIVE

To evaluate the association between caffeine exposure and acute kidney injury (AKI) in very low birth weight (VLBW; ≤1500 g) neonates.

STUDY DESIGN

We retrospectively reviewed a cohort of 140 VLBW neonates consecutively admitted to the University of Virginia's neonatal intensive care unit from March 2011 to June 2012, excluding only those admitted >2 days of age or who died at <2 days after birth. We separately analyzed a subgroup of 44 neonates who received prolonged invasive respiratory support (mechanical ventilation for first 7 days after birth). The exposure of interest was caffeine exposure in the first week after birth. The primary outcome was AKI within the first 10 days after birth according to the Kidney Disease: Improving Global Outcomes system, modified to include only serum creatinine.

RESULTS

Caffeine exposure occurred in 72.1% of all patients and 54.5% of those who received prolonged invasive respiratory support. AKI occurred less frequently in neonates who received caffeine (all patients: 17.8% vs 43.6%; P = .002; prolonged invasive respiratory support: 29.2% vs 75.0%; P = .002). Caffeine exposure was associated with decreased odds for AKI in logistic regression models adjusted for sex, birth weight, gestational age, small for gestational age status, illness severity on admission, and receipt of indomethacin, invasive ventilation, dopamine, aminoglycosides, and vancomycin (all patients: OR 0.22; 95% CI 0.07-0.75, P = .02; prolonged invasive respiratory support subgroup: OR 0.06; 95% CI 0.01-0.57, P = .02).

CONCLUSIONS

In a cohort of VLBW neonates, those exposed to caffeine were less likely to experience AKI.

Theophylline Population Pharmacokinetics and Dosing in Children Following Congenital Heart Surgery With Cardiopulmonary Bypass

Children undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) frequently develop acute kidney injury due to renal ischemia. Theophylline, which improves renal perfusion via adenosine receptor inhibition, is a potential targeted therapy. However, children undergoing cardiac surgery and CPB commonly have alterations in drug pharmacokinetics. To help understand optimal aminophylline (salt formulation of theophylline) dosing strategies in this population, a population-based pharmacokinetic model was developed using nonlinear mixed-effects modeling (NONMEM) from 71 children (median age 5 months; 90% range 1 week to 10 years) who underwent cardiac surgery requiring CPB and received aminophylline as part of a previous randomized controlled trial. A 1-compartment model with linear elimination adequately described the pharmacokinetics of theophylline. Weight scaled via allometry was a significant predictor of clearance and volume. In addition, allometric scaled clearance increased with age implemented as a power maturation function. Compared to prior reports in noncardiac children, theophylline clearance was markedly reduced across age. In the final population pharmacokinetic model, optimized empiric dosing regimens were developed via Monte Carlo simulations. Doses 50% to 75% lower than those recommended in noncardiac children were needed to achieve target serum concentrations of 5 to 10 mg/L.

Prophylactic theophylline for the prevention of severe renal dysfunction in term and post-term neonates with perinatal asphyxia: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To examine the effect of prophylactic theophylline for the prevention of severe renal dysfunction in post-asphyxiated term and post-term infants.

STUDY DESIGN

Systematic review and meta-analysis of randomized controlled trials (RCTs) comparing prophylactic theophylline vs placebo in term infants following perinatal asphyxia.

RESULT

Four RCTs involving 197 infants were included in the meta-analysis. Compared with placebo, prophylactic theophylline was associated with a significant reduction in the incidence of severe renal dysfunction (pooled relative risk) using fixed-effects model was 0.38 (95% confidence interval, 0.25 to 0.57; P<0.001).

CONCLUSION

The meta-analysis provides evidence that prophylactic theophylline significantly reduce the incidence of severe renal dysfunction. However, because of the lack of information on the long-term renal and neurodevelopmental outcome and measured theophylline levels with relation to adverse effects observed, prudence with the clinical use of prophylactic theophylline is required. Additionally, the included trials were prior to the era of therapeutic hypothermia and thus inference of renal benefit in an infant undergoing hypothermia therapy cannot be made.

Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1)

Acute kidney injury (AKI) is a common and serious problem affecting millions and causing death and disability for many. In 2012, Kidney Disease: Improving Global Outcomes completed the first ever, international, multidisciplinary, clinical practice guideline for AKI. The guideline is based on evidence review and appraisal, and covers AKI definition, risk assessment, evaluation, prevention, and treatment. In this review we summarize key aspects of the guideline including definition and staging of AKI, as well as evaluation and nondialytic management. Contrast-induced AKI and management of renal replacement therapy will be addressed in a separate review. Treatment recommendations are based on systematic reviews of relevant trials. Appraisal of the quality of the evidence and the strength of recommendations followed the Grading of Recommendations Assessment, Development and Evaluation approach. Limitations of the evidence are discussed and a detailed rationale for each recommendation is provided.

Low-dose aminophylline for the treatment of neonatal non-oliguric renal failure-case series and review of the literature

OBJECTIVE

Aminophylline is a methylxanthine with multiple physiologic actions. At low doses, aminophylline can antagonize adenosine and improve renal function via increased glomerular filtration rate. Despite its clinical use, little data exists in neonates for this indication. Therefore, the objective of this report is to describe the impact of aminophylline on renal function indices in a series of neonates with acute renal failure.

MATERIALS AND METHODS

This was a retrospective chart review of 13 neonates with acute renal failure who received aminophylline during a 15-month study period. Aminophylline was administered at 1 mg/kg intravenously or orally every twelve hours. Forty-six percent (n = 6) of the patients received a 5 mg/kg loading dose before initiation of maintenance therapy. Most patients had already received other treatments for renal failure, including diuretics and dopamine.

RESULTS

Resolution of acute renal failure (with normalization of serum creatinine and blood urea nitrogen) was documented in 10 patients (77%). Four of the thirteen patients died from complications due to their prematurity. Failure of low-dose aminophylline was observed in 3 of the 4 patients who died.

CONCLUSIONS

Low-dose aminophylline in neonates with acute renal failure is associated with an improvement in renal function indices.

Pharmacokinetics of p-Aminohippuric Acid and Inulin in Rabbits with Aristolochic Acid Nephropathy

The characteristics of aristolochic acid nephropathy (AAN) are interstitial fibrosis and atrophy of the proximal tubules, but with no change in glomeruli. To investigate the effects of AA on renal functions and the pharmacokinetics (PKs) of p-aminohippuric acid (PAH) and inulin, New Zealand white rabbits were used in this study. The plasma concentrations of PAH and inulin were determined by validated HPLC methods. After a single intravenous administration of 0.5 mg/kg aristolochic acid sodium (AANa), rabbits exhibited mild to moderate nephrotoxicity on the 7th day. Significant tubulointerstitial damage to kidney specimens was found, but there were no remarkable glomerular changes. Clearance rates of PAH and inulin both significantly decreased in AANa-treated rabbits. In addition, there was a significant correlation among the degree of tubulointerstitial changes and PK parameters of PAH after AANa administration, but no correlation was noted with the PKs of inulin. With mild to moderate AAN in rabbits, the renal plasma flow significantly decreased by 55%, and the glomerular filtration rate also significantly decreased by 85%. In conclusion, major renal lesions were found on proximal tubules after AANa administration. The PKs of PAH and inulin significantly changed, and kidney functions, including the RPF and GFR, were reduced.

Methylxanthines and the kidney

This chapter describes the effects of the natural methylxanthines caffeine and theophylline on kidney function. Theophylline in particular was used traditionally to increase urine out put until more potent diuretics became available in the middle of the last century. The mildly diuretic actions of both methylxanthines are mainly the result of inhibition of tubular fluid reabsorption along the renal proximal tubule. Based upon the use of specific adenosine receptor antagonists and the observation of a complete loss of diuresis in mice with targeted deletion of the A1AR gene, transport inhibition by methylxanthines is mediated mainly by antagonism of adenosine A1 receptors (A1AR) in the proximal tubule. Methylxanthines are weak renal vasodilators, and they act as competitive antagonists against adenosine-induced preglomerular vasoconstriction. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine. Since enhanced intrarenal adenosine levels lead to reduced glomerular filtration rate in several pathological conditions theophylline has been tested for its therapeutic potential in the renal impairment following administration of nephrotoxic substances such as radiocontrast media, cisplatin, calcineurin inhibitors or following ischemia-reperfusion injury. In experimental animals functional improvements have been observed in all of these conditions, but available clinical data in humans are insufficient to affirm a definite therapeutic efficacy of methylxanthines in the prevention of nephrotoxic or postischemic renal injury.

Targeting of adenosine receptors in ischemia-reperfusion injury

IMPORTANCE OF THE FIELD

Ischemia-reperfusion (IR) injury is a common problem after transplantation as well as myocardial infarction and stroke. IR initiates an inflammatory response leading to rapid tissue damage. Adenosine, produced in response to IR, is generally considered a protective signaling molecule and elicits its physiological responses through four distinct adenosine receptors. The short half-life, lack of specificity and rapid metabolism limits the use of adenosine as a therapeutic agent. Thus, intense research efforts have focused on the synthesis and implementation of specific adenosine receptor agonists and antagonists as potential therapeutic agents for a variety of inflammatory conditions including IR injury.

AREAS COVERED IN THIS REVIEW

Current knowledge on IR injury with a focus on lung, heart and kidney and studies that have advanced our understanding of the role of adenosine receptors and the therapeutic potential of adenosine receptor agonists and antagonists for the prevention of IR injury.

WHAT THE READER WILL GAIN

Insight into the role of adenosine receptor signaling in IR injury.

TAKE HOME MESSAGE

No therapies are currently available that specifically target IR injury; however, targeting of specific adenosine receptors may offer therapeutic strategies in this regard.

N-acetylcysteine to reduce renal failure after cardiac surgery: a systematic review and meta-analysis

PURPOSE

To assess the effect of N-acetylcysteine (NAC) on acute renal failure and important clinical outcomes after cardiac surgery.

METHODS

Two reviewers performed literature searches, using EMBASE and PubMed, of randomized controlled trials investigating the renoprotective effect of N-acetylcysteine in cardiac surgery. Treatment effects were calculated as relative risks (RR) with 95% confidence intervals (CI). Heterogeneity and publication bias were assessed using the I(2) test and funnel plots, respectively. Meta regression was performed to assess the effect of baseline renal function and the use of aprotinin on renal function.

RESULTS

Seven randomized controlled trials (RCTs) (n = 1000) were identified. No study could demonstrate, either independently or meta-analytically, an improvement in the postoperative increase in creatinine, mortality (RR 0.93, 95% CI 0.4 to 2.07), renal failure requiring renal replacement therapy (RR 1.01, 95% CI 0.49 to 2.12), myocardial infarction (RR 0.88, 95% CI 0.36 to 1.88), atrial fibrillation (RR 0.88, 95% CI 0.70 to 1.10), or stroke (RR 0.69, 95% CI 0.27 to 1.69). There was a small, though significant increase in postoperative blood loss among patients treated with NAC (weighted mean difference 119 mL 95% CI 51, 187). After meta regression neither increase in postoperative creatinine (r(2) = 0.33) nor renal replacement therapy (r(2) = 0.04) was associated with the baseline creatinine or with NAC dose (r(2) =0.04).

CONCLUSION

This analysis did not find that treatment with NAC was associated with clinical renal protection during cardiac surgery, or improvement in other clinical outcomes.

Adenosine receptors and the kidney

The autacoid, adenosine, is present in the normoxic kidney and generated in the cytosol as well as at extracellular sites. The rate of adenosine formation is enhanced when the rate of ATP hydrolysis prevails over the rate of ATP synthesis during increased tubular transport work or during oxygen deficiency. Extracellular adenosine acts on adenosine receptor subtypes (A(1), A(2A), A(2B), and A(3)) in the cell membranes to affect vascular and tubular functions. Adenosine lowers glomerular filtration rate by constricting afferent arterioles, especially in superficial nephrons, and thus lowers the salt load and transport work of the kidney consistent with the concept of metabolic control of organ function. In contrast, it leads to vasodilation in the deep cortex and the semihypoxic medulla, and exerts differential effects on NaCl transport along the tubular and collecting duct system. These vascular and tubular effects point to a prominent role of adenosine and its receptors in the intrarenal metabolic regulation of kidney function, and, together with its role in inflammatory processes, form the basis for potential therapeutic approaches in radiocontrast media-induced acute renal failure, ischemia reperfusion injury, and in patients with cardiorenal failure.

[Acute renal failure in full term neonates with perinatal asphyxia. Prospective study of 87 cases]

BACKGROUND

Renal involvement is frequent in neonates with perinatal asphyxia. It is correlated with the severity of neurological damage and seems to worsen the long-term neurological outcome.

PURPOSE

The aim of this study was to determine the incidence of renal failure after perinatal asphyxia, to precise the relationship between severity of cerebral damage and renal failure and to evaluate the place of renal damage in the short- and middle-term neurological outcome.

POPULATION AND METHODS

We conducted a prospective study including 87 full-term neonates admitted in the neonatology department of F. Hached university hospital in Sousse (Tunisia) and suffering from hypoxic ischemic encephalopathy from 1st January 2003 to 30 June 2005. Renal function was assessed by measuring plasma urea and creatinine at age 48 h. Renal failure was defined by a level of creatinine above 90 micromol/l. Neurologic examination was performed on day 7. The survivors were followed up by the same senior after discharge.

RESULTS

During the study period, 87 full-term neonates were admitted for hypoxic ischemic encephalopathy. The degree of neurological impairment was determined according to Sarnat classification: 1st stage 9 neonates (10,3%), 2nd stage 67 (77%) and 3rd stage 11(12,6%). Renal failure involved 15 neonates (17,2%) of whom 10 belonging to the 2nd stage group. Renal function outcome was favorable in all survivors with normalisation of plasma creatinine level between day 5 and day 15. Eight neonates died, of whom 3 with renal failure. Neurologic examination was abnormal in 36 out of 72 (50%) neonates without renal failure and in 9 of the 12 (75%) survivors with renal failure. Among the 12 neonates with renal failure, 7 had abnormal neurologic features at discharge. Neurologic assessment between 6 and 18 months was abnormal in 4/12 (33%) of neonates with renal failure versus 8/72(11%) of neonates without renal failure.

CONCLUSION

Transient renal failure is commonly observed in perinatal asphyxia. Renal failure is correlated with neurologic severity. Renal function assessment using creatinine plasma level seems to be correlated with neurologic outcome. However, other tools appreciating renal function, namely tubular function, should be determined earlier in order to predict neurologic outcome after hypoxic ischemic encephalopathy.

Theophylline for renal function in term neonates with perinatal asphyxia: a randomized, placebo-controlled trial

OBJECTIVE

To study whether prophylactic theophylline can reduce the incidence and/or severity of renal failure in term infants with perinatal asphyxia.

STUDY DESIGN

Term neonates with severe perinatal asphyxia were randomized to receive a single dose of either theophylline (study group, n = 40) or placebo (control group, n = 30) during the first hour of life. Daily weight, output/input ratio, 24-hour fluid intake, and urine volumes were recorded during the first 5 days of life. Those infants with asphyxial renal failure were followed up for 1 year.

RESULTS

The incidence of severe renal dysfunction was increased in the control group. Creatinine clearance was higher and excretion of beta 2 microglobulin (beta2M) was lower in the theophylline group. Conversely, the glomerular filtration rate was lower in the control group. In infants with renal failure, serum creatinine and creatinine clearance returned to normal in the neonatal period, and the increased beta2M excretion normalized by age 6 weeks.

CONCLUSIONS

A single dose of theophylline within the first hour of birth in term neonates with perinatal asphyxia results in a significant decrease in serum creatinine level and urinary excretion of beta2M, along with an increase in creatinine clearance.

Adenosine and Kidney Function

In this review we outline the unique effects of the autacoid adenosine in the kidney. Adenosine is present in the cytosol of renal cells and in the extracellular space of normoxic kidneys. Extracellular adenosine can derive from cellular adenosine release or extracellular breakdown of ATP, AMP, or cAMP. It is generated at enhanced rates when tubular NaCl reabsorption and thus transport work increase or when hypoxia is induced. Extracellular adenosine acts on adenosine receptor subtypes in the cell membranes to affect vascular and tubular functions. Adenosine lowers glomerular filtration rate (GFR) by constricting afferent arterioles, especially in superficial nephrons, and acts as a mediator of the tubuloglomerular feedback, i.e., a mechanism that coordinates GFR and tubular transport. In contrast, it leads to vasodilation in deep cortex and medulla. Moreover, adenosine tonically inhibits the renal release of renin and stimulates NaCl transport in the cortical proximal tubule but inhibits it in medullary segments including the medullary thick ascending limb. These differential effects of adenosine are subsequently analyzed in a more integrative way in the context of intrarenal metabolic regulation of kidney function, and potential pathophysiological consequences are outlined.

Diurétiques et prématuré

Diuretics are frequently used in preterm infants in various situations such as patent ductus arteriosus, respiratory distress syndrome, bronchopulmonary dysplasia or neonatal renal insufficiency. However, the beneficial effects reported in the literature are usually transient, without any obvious effect on important parameters such as duration of oxygen dependency, ventilator dependency, length of hospital stay, long-term outcome, or mortality. Moreover, these drugs may induce water-electrolyte disorders especially when used for a long-term period. Thus, we recommend a systematic analysis of the beneficial/risk ratio before any use of these drugs.

A randomised, double blind, placebo controlled trial of the effect of theophylline in prevention of vasomotor nephropathy in very preterm neonates with respiratory distress syndrome

BACKGROUND

Vasomotor nephropathy is a common renal dysfunction in very preterm neonates.

OBJECTIVE

To determine whether theophylline could prevent vasomotor nephropathy in very preterm infants with respiratory distress syndrome.

METHODS

A randomised, double blind, placebo controlled trial of 50 preterm infants of gestational age < or = 32 weeks needing assisted ventilation. Infants received an intravenous dose of theophylline (1 mg/kg) or placebo for three days. The 24 hour urine volume was measured daily. On days 2, 5, and 11, blood samples and 12 hour urine collections were analysed for electrolytes, creatinine, and urea.

RESULTS

On day 1, urine output was significantly higher in the theophylline (2.4 (0.9) ml/kg/h) than the placebo (1.6 (1.0) ml/kg/h; p = 0.023) group (values are mean (SD)). The incidence of oligoanuria was significantly lower in the theophylline treated (5%) than the placebo (33%) group. Twenty four hours after the first administration of theophylline/placebo, serum creatinine concentration was significantly lower in the theophylline (0.76 (0.23) mg/dl) than the placebo (1.0 (0.41) mg/dl; p = 0.025) group. On day 5 an increase in serum creatinine was observed in both groups. On day 11 a significant reduction in serum creatinine was observed, compared with day 5, with no difference between the two groups.

CONCLUSION

The results suggest that, in very preterm infants with respiratory distress syndrome, early theophylline administration improves renal function during the first two days of life.

Theophylline Improves Early Allograft Function in Rat Kidney Transplantation

Several previous studies have demonstrated a beneficial effect of the adenosine receptor (AdoR) antagonist theophylline in different forms of acute renal failure in laboratory animals and in humans. Therefore, we wanted to test whether theophylline can also improve impaired allograft function following ischemia reperfusion injury in experimental kidney transplantation (KT). Orthotopic transplantation of the left kidney was performed from Fisher 344 into Lewis rats. All transplanted rats received daily cyclosporine (5 mg/kg). The effect of theophylline treatment (10 mg/kg) on graft function was compared with appropriate controls on day 5 after KT by assessment of glomerular filtration rate (GFR) (inulin clearance). On day 5, GFR of allografts in control rats was 0.23 +/- 0.05 ml/min/g kidney weight (n = 10) compared with 0.50 +/- 0.09 ml/min/g in rats receiving theophylline (n = 9, p < 0.01), representing a 2-fold increase in GFR. Renal AdoR A(1) mRNA content was significantly increased in both KT groups compared with their respective control groups, whereas mRNA of AdoR A(2a), A(2b), and A(3) were found to be unchanged. Theophylline did not affect significantly interstitial infiltration of the graft by monocytes/macrophages and T-cells. Likewise, serum cytokines [interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor-alpha] and erythropoietin plasma levels were not different among the allograft groups. The present study demonstrates that theophylline remarkably improved early renal allograft function in rats undergoing KT without influencing cytokine serum patterns or tissue inflammation. Since theophylline is a commonly used medication in humans, clinical studies in patients undergoing KT are warranted.

Prophylactic theophylline to prevent renal dysfunction in newborns exposed to perinatal asphyxia--a study in a developing country

Renal damage frequently complicates perinatal asphyxia. Renal vasoconstriction due to adenosine metabolite leads to a fall in glomerular filtration rate (GFR) and filtration fraction. This might be inhibited by the nonspecific adenosine receptor antagonist, theophylline. This study was designed to determine whether theophylline could prevent and/or ameliorate renal dysfunction in term neonates with perinatal asphyxia. We randomized 40 severely asphyxiated term infants to receive intravenously a single dose of either theophylline (5 mg/kg; study group: n=20) or placebo (control group: n=20) during the first hour of life. Fluid intake, urine output, serum creatinine, creatinine clearance, GFR, urinary beta2 microglobulin (beta2 M) and sodium excretion were recorded during the first 5 days of life. The two groups were comparable. No significant difference was reported regarding mechanical ventilatory support, respiratory complications and seizures. Severe renal dysfunction was significantly higher in the control group. Serum creatinine values were less, and creatinine clearance and GFR were significantly higher in the theophylline group from the second day onwards. beta2 M excretion was significantly less in the theophylline group, while sodium excretion and hematuria showed no significant difference. Prophylactic theophylline treatment, given early after birth, has beneficial effects in reducing the renal involvement in asphyxiated full-term infants, with no significant changes in central nervous system involvement.

Chronic hypoxia up-regulates expression of adenosine A1 receptors in DDT1-MF2 cells

As the first step to understand how chronic hypoxia might regulate smooth muscle function in health and disease, we have employed an established immortalised cell model of smooth muscle, DDT1-MF2 cells, to address the hypothesis that adenosine A1 receptor density is modulated by O2 availability. Maximal specific binding (Bmax) of the selective adenosine A1 receptor antagonist, [3H]-DPCPX, to cell membranes increased 3.5-fold from 0.48 +/- 0.02 pmol/mg to 1.7 +/- 0.5 pmol/mg protein after 16 hr of hypoxia and this effect was not accompanied by any statistically significant changes in either binding affinity (0.84 +/- 0.2 nM vs. 1.2 +/- 0.3 nM) or Hill coefficient (1.1 +/- 0.1 vs. 0.99 +/- 0.03). Hypoxia-evoked increases in membrane receptor density were paralleled in intact DDT1-MF2 cells. In addition, the increase in [3H]-DPCPX binding to intact cells was inhibited by co-incubation during hypoxia with the translational inhibitor cycloheximide, the transcriptional blocker actinomycin D and the NFkappaB inhibitor sulphasalazine. Together, these data show that adenosine A1 receptor density is modulated, at least in part, by O2-dependent activation of the transcription factor NFkappaB and adds to the list of processes dynamically regulated by ambient oxygen availability. Since hypoxia is an initiating factor in acute renal failure, similar changes in transcription may account for up-regulation of adenosine A1 receptors noted previously in the renal vasculature of rats with acute renal failure.

Renal effects of adenosine A1-receptor blockade with 8-cyclopentyl-1,3-dipropylxanthine in hypoxemic newborn rabbits

The key role of intrarenal adenosine in mediating the hypoxemic acute renal insufficiency in newborn rabbits has been well demonstrated using the nonspecific adenosine antagonist theophylline. The present study was designed to define the role of adenosine A1 receptors during systemic hypoxemia by using the specific A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Renal function parameters were assessed in 31 anesthetized and mechanically ventilated newborn rabbits. In normoxia, DPCPX infusion induced a significant increase in diuresis (+44%) and GFR (+19%), despite a significant decrease in renal blood flow (RBF) (-22%) and an increase in renal vascular resistance (RVR) (+37%). In hypoxemic conditions, diuresis (-19%), GFR (-26%), and RBF (-35%) were decreased, whereas RVR increased (+33%). DPCPX administration hindered the hypoxemia-induced decrease in GFR and diuresis. However, RBF was still significantly decreased (-27%), whereas RVR increased (+22%). In all groups, the filtration fraction increased significantly. The overall results support the hypothesis that, in physiologic conditions, intrarenal adenosine plays a key role in regulating glomerular filtration in the neonatal period through preferential A1-mediated afferent vasoconstriction. During a hypoxemic stress, the A1-specific antagonist DPCPX only partially prevented the hypoxemia-induced changes, as illustrated by the elevated RVR and drop in RBF. These findings imply that the contribution of intrarenal adenosine to the acute adverse effects of hypoxemia might not be solely mediated via the A1 receptor.

The adverse renal effects of prostaglandin-synthesis inhibitors in the newborn rabbit

Nonsteroidal anti-inflammatory drugs are frequently used during pregnancy (premature labor, polyhydramnios) and the immediate postnatal period (closure of patent ductus arteriosus). This article evaluates the renal effect of 3 nonspecific COX inhibitors (aspirin, indomethacin, and ibuprofen) in newborn rabbits. Five groups of anesthetized, ventilated, normoxemic 6-day-old rabbits (n = 52) were administered intravenous aspirin (40 mg/kg), indomethacin (2 mg/kg), and ibuprofen (0.02, 0.2, 2.0 mg/kg, respectively). Renal function and hemodynamics as assessed by inulin and para-aminohippuric acid clearances were measured before and in the hour after drug administration. In all groups of animals, the nonselective COX inhibitors induced an increase in renal vascular resistance and a consequent decrease in glomerular filtration rate and renal blood flow. Urine flow rate decreased significantly in all groups, except in the group receiving the lowest dose of ibuprofen. In newborn rabbits, aspirin, indomethacin, and ibuprofen induced intense renal vasoconstriction, which resulted in impaired renal function. This observation illustrates the major renal protective role played by the vasodilatory prostaglandins during the neonatal period, when the kidney is perfused at very low perfusion pressure. We conclude that all COX inhibitors should be administered with the same caution to the preterm neonate.

Complementary effects of adenosine and angiotensin II in hypoxemia-induced renal dysfunction in the rabbit

The acute renal effects of hypoxemia and the ability of the co-administration of an angiotensin converting enzyme inhibitor (perindoprilat) and an adenosine receptor antagonist (theophylline) to prevent these effects were assessed in anesthetized and mechanically-ventilated rabbits. Renal blood flow (RBF) and glomerular filtration rate (GFR) were determined by the clearances of para-aminohippuric acid and inulin, respectively. Each animal acted as its own control. In 8 untreated rabbits, hypoxemia induced a significant drop in mean blood pressure (-12 +/- 2%), GFR (-16 +/- 3%) and RBF (-12 +/- 3%) with a concomitant increase in renal vascular resistance (RVR) (+ 18 +/- 5%), without changes in filtration fraction (FF) (-4 +/- 2%). These results suggest the occurrence of both pre- and postglomerular vasoconstriction during the hypoxemic stress. In 7 rabbits pretreated with intravenous perindoprilat (20 microg/kg), the hypoxemia-induced changes in RBF and RVR were prevented. FF decreased significantly (-18 +/- 2%), while the drop in GFR was partially blunted. These results could be explained by the inhibition of the angiotensin-mediated efferent vasoconstriction by perindoprilat. In 7 additional rabbits, co-administration of perindoprilat and theophylline (1 mg/kg) completely prevented the hypoxemia-induced changes in RBF (+ 11 +/- 3%) and GFR (+ 2 +/- 3%), while RVR decreased significantly (-14 +/- 3%). Since adenosine and angiotensin II were both shown to participate, at least in part, in the renal changes induced by hypoxemia, the beneficial effects of perindoprilat and theophylline in this model could be mediated by complementary actions of angiotensin II and adenosine on the renal vasculature.

Immunolocalisation of adenosine A(1) receptors in the rat kidney

The location of adenosine A(1) receptors in the rat kidney was investigated using immunolabelling with antibodies raised to a 15-amino-acid sequence near the C-terminus of the receptor (antibody I) and to a 14-amino-acid sequence in the second extracellular loop (antibody II). In the cortex, antibody I bound to adenosine A(1) receptors in mesangial cells and afferent arterioles, whilst antibody II bound to receptors in proximal convoluted tubules. In the medulla, both antibodies bound to receptors in collecting ducts and the papillary surface epithelium. These observations provide support for the diverse functional roles previously proposed for the adenosine A(1) receptor in the kidney. The labelling of distinct but different structures in the cortex by antibodies raised to different amino acid sequences on the A(1) receptor protein suggests that differing forms of the receptor are present in this region of the kidney.

The renal hemodynamic effects of ibuprofen in the newborn rabbit

In early childhood, nonsteroidal anti-inflammatory drugs are mainly used to either prevent or treat premature labor of the mother and patent ductus arteriosus of the newborn infant. The most frequently used prostaglandin-synthesis inhibitor is indomethacin. Fetuses exposed to indomethacin in utero have been born with renal developmental defects, and in both the unborn child and the term and premature newborn this drug may compromise renal glomerular function. The latter has in the past also been observed when i.v. indomethacin or i.v. acetylsalicylic acid (aspirin) were administered to newborn rabbits. The present experiments were designed to evaluate whether ibuprofen has less renal side effects than indomethacin, as claimed. Three groups of anesthetized, ventilated, normoxemic neonatal rabbits were infused with increasing doses of ibuprofen (0.02, 0.2, 2.0 mg/kg body weight) and the following renal parameters were measured: urine volume, urinary sodium excretion, GFR, and renal plasma flow. Renal blood flow, filtration fraction, and the renal vascular resistance were calculated according to standard formulae. Intravenous ibuprofen caused a dose-dependent, significant reduction in urine volume, GFR, and renal blood flow with a fall in filtration fraction in the animals receiving the highest dose of ibuprofen (2 mg/kg body weight). There was a very steep rise in renal vascular resistance. Urinary sodium excretion decreased. These experiments in neonatal rabbits clearly show that acute i.v. doses of ibuprofen also have significant renal hemodynamic and functional side effects, not less than seen previously with indomethacin.

Effect of severe normocapnic hypoxia on renal function in growth-restricted newborn piglets

To examine the effects of intrauterine growth restriction and acute severe oxygen deprivation on renal blood flow (RBF), renovascular resistance (RVR), and renal excretory functions in newborns, studies were conducted on 1-day-old anesthetized piglets divided into groups of normal weight (NW, n = 14) and intrauterine growth-restricted (IUGR, n = 14) animals. Physiological parameters, RBF, RVR, and urinary flow, were similar in NW and IUGR piglets, but glomerular filtration rate (GFR) and filtration fraction were significantly less in IUGR animals (P < 0.05). An induced 1-h severe hypoxia (arterial PO(2) = 19 +/- 4 mmHg) resulted in, for both groups, a pronounced metabolic acidosis, strongly reduced RBF, and increased fractional sodium excretion (FSE; P < 0.05) with a less-pronounced increase of RVR and arterial catecolamines in IUGR piglets. Of significance was a smaller decrease in RBF for IUGR piglets (P < 0.05). Early recovery showed a transient period of diuresis with increased osmotic clearance and elevated FSE in both groups (P < 0.05). However, GFR and renal O(2) delivery remained reduced in NW piglets (P < 0.05). We conclude that, in newborn IUGR piglets, RBF is maintained, although GFR is compromised. Severe hypoxemia induces similar alterations of renal excretion in newborn piglets. However, the less-pronounced RBF reduction during hypoxemia indicates an improved adaptation of newborn IUGR piglets on periods of severely disturbed oxygenation. Furthermore, newborn piglets reestablish the ability for urine concentration and adequate sodium reabsorption early after reoxygenation so that a sustained acute renal failure was prevented.

A randomized, double-blind, placebo-controlled trial of the effects of prophylactic theophylline on renal function in term neonates with perinatal asphyxia

BACKGROUND

The kidney is the most damaged organ in asphyxiated full-term infants. Experiments in rabbits and rats have shown that renal adenosine acts as a vasoconstrictive metabolite in the kidney after hypoxemia and/or ischemia, contributing to the fall in glomerular filtration rate (GFR) and filtration fraction. Vasoconstriction produced by adenosine can be inhibited by the nonspecific adenosine receptor antagonist, theophylline. Gouyon and Guignard performed studies in newborn and adult rabbits subjected to normocapnic hypoxemia. Their results clearly showed that the hypoxemia-induced drop in GFR could be avoided by the administration of low doses of theophylline.

OBJECTIVE

This study was designed to determine whether theophylline could prevent and/or ameliorate renal dysfunction in term neonates with perinatal asphyxia.

SETTING

Buenos Aires, Argentina.

STUDY DESIGN

We randomized 51 severe asphyxiated term infants to receive intravenously a single dose of either theophylline (8 mg/kg; study group: n = 24) or placebo (control group: n = 27) during the first 60 minutes of life. The 24-hour fluid intake and the urine volumes formed were recorded during the first 5 days of life. Daily volume balances (water output/input ratio and weights) were determined. Severe renal dysfunction was defined as serum creatinine elevated above 1.50 mg/dL, for at least 2 consecutive days after a fluid challenge, or rising levels of serum creatinine (.3 mg/dL/day). The GFR was estimated during the second to third days of life by endogenous creatinine clearance (mL/minute/1.73 m2) and using Schwartz's formula: GFR (mL/minute/1.73 m2) =.45 x length (cm)/plasma creatinine (mg/100 mL) during the first 5 days of life. Tubular performance was assessed as the concentration of beta2-microglobulin (beta2M) determined by enzyme immunoassay, on the first voided urine 12 hours after theophylline administration. The statistical analysis for the evaluation of the differences between the groups was performed with Student's t and chi(2) tests as appropriate.

RESULTS

During the first day of life, the 24-hour fluid balance was significantly more positive in the infants receiving placebo compared with the infants receiving theophyline. Over the next few days, the change in fluid balance favored the theophyline group. Significantly higher mean plasma values were recorded in the placebo group from the second to the fifth days of life. Severe renal dysfunction was present in 4 of 24 (17%) infants of the theophylline group and in 15 of 27 (55%) infants of the control group (relative risk:.30; 95% confidence interval:.12-.78). Mean endogenous creatinine clearance of the theophylline group was significantly increased compared with the creatinine clearance in infants receiving placebo (21.84 +/- 7.96 vs 6.42 +/- 4.16). The GFR (estimated by Schwartz's formula) was markedly decreased in the placebo group. Urinary beta2M concentrations were significantly reduced in the theophylline group (5.01 +/- 2.3 mg/L vs 11.5 +/- 7.1 mg/L). Moreover, 9 (33%) patients of the theophylline group versus 20 (63%) infants of the control group had urinary beta2M above the normal limit (<.018). There was no difference in the severity of the asphyxia between infants belonging to the theophylline and control groups in regards of Portman's score. Except for renal involvement, a similar frequency of multiorganic dysfunction, including neurologic impairment, was observed in both groups. The theophylline group achieved an average serum level of 12.7 microg/mL (range: 7.5-18.9 microg/mL) at 36 to 48 hours of live versus traces (an average serum level of .87 microg/mg) in the placebo group.

CONCLUSIONS

Our data suggest that prophylactic theophylline, given early after birth, has beneficial effects on reducing the renal dysfunction in asphyxiated full-term infants. (ABSTRACT TRUNCATED)

Differential expression of renal adenosine A(1) receptors induced by acute renal failure

The distribution of renal adenosine A(1) receptors was investigated in rats with glycerol- or mercuric chloride (HgCl(2))-induced acute renal failure. Receptors were localised by autoradiography using [(3)H]8-cyclopentyl-1,3-dipropylxanthine ([(3)H]DPCPX), a selective A(1) adenosine receptor antagonist. In saline-injected control animals, significant labelling with [(3)H]DPCPX was detected in glomeruli, the inner stripe of outer medulla, and the inner medulla. Sixteen hours following induction of glycerol-induced acute renal failure (ARF), a 34% increase in labelling in glomeruli was noted compared to saline-injected controls, and by 48 hr, glomerular labelling had increased by 200%. In addition, 48 hr following glycerol injection, significant labelling was now detected in the cortical labyrinth and medullary rays whilst, in the inner medulla, labelling had decreased by 34%. By contrast to glycerol-induced ARF, the only significant change noted 48 hr following induction of HgCl(2)-induced ARF was a 39% decrease in labelling in the inner medulla. It is concluded that glycerol-induced ARF results in differential expression of renal adenosine A(1) receptors with increased expression in the cortex and reduced expression in the inner medulla. Increased density of A(1) receptors in glomeruli may account, at least in part, for the increased renal vasoconstrictor response to adenosine and depressed glomerular filtration rate noted previously in this type of acute renal failure.

Protective effect of aminophylline on renal perfusion changes induced by high-energy shockwaves identified by Gd-DTPA-enhanced first-pass perfusion MRI

PURPOSE

The purpose of this study was to evaluate regional renal hemodynamics in a noninvasive manner using gadolinium-DPTA magnetic resonance imaging (MRI) before and after extracorporeal shockwave lithotripsy (SWL). In addition, the renoprotective effect of intravenous aminophylline was evaluated on the perfusion on kidneys undergoing SWL.

PATIENTS AND METHODS

Ten randomly selected patients were evaluated for regional renal blood flow in the cortex and medulla with Gd-DTPA MRI studies within 2 weeks before and 4 hours after SWL. Five of these patients were treated with 500 mg of intravenous aminophylline 45 minutes prior to SWL. Renal hemodynamics were assessed utilizing relative perfusion indices (PI) calculated from signal intensity-v-time curves obtained from regions of interest (ROI). The ROI choice was based on the contrast-enhanced MRI images. Relative PIs of pre-SWL and post-SWL studies were compared in the first group of patients. Relative PIs of the treated kidney were compared with those of the contralateral kidney in the second group of patients, who received aminophylline.

RESULTS

In the group not treated with aminophylline, there was no significant difference in cortical perfusion before SWL (average PI -7+/-3%). However, after lithotripsy, there was a reduction of cortical flow (average PI 31+/-12%) in the treated kidney. In the group treated with aminophylline, renal hemodynamics study after SWL revealed no significant difference in relative perfusion (average PI -8+/-6%). Relative PIs of the medulla were small for all patients, but standard errors were large, indicating a wide range of values.

CONCLUSIONS

This study helps to establish reduced cortical flow after SWL and demonstrates that aminophylline attenuated this response in the kidneys subjected to lithotripsy. It appears that aminophylline administration causes no alteration in medullary blood flow.

Effects of dopamine and aminophylline on contrast-induced acute renal failure after coronary angioplasty in patients with preexisting renal insufficiency

In phase 1 of this study, 60 patients undergoing coronary angioplasty were randomized to receive saline, dopamine, or aminophylline; the overall incidence of contrast-induced renal failure was 38%, without difference among the 3 groups. In phase 2 of this study, 72 patients with established contrast-induced renal failure were randomized to receive saline or dopamine; dopamine had a deleterious effect on the severity of renal failure, prolonging the course.

Protective effect of perindoprilat in the hypoxemia-induced renal dysfunction in the newborn rabbit

The renal effects of acute hypoxemia and the ability of perindoprilat, a potent angiotensin-converting enzyme inhibitor, to prevent these effects were assessed in 31 anesthetized and mechanically ventilated newborn (5 to 8 d of age) rabbits. Renal blood flow (RBF) and GFR were determined by the clearances of para-aminohippuric acid and inulin, respectively. Each animal acted as its own control. In eight normoxemic rabbits (group 1), the i.v. infusion of saline did not change renal and hemodynamic functions. In eight additional rabbits, acute hypoxemia (PaO2= 40 mm Hg) induced a significant decrease in mean blood pressure (-8+/-2%), RBF (-36+/-3%), and GFR (-31+/-3%) and an increase in renal vascular resistance (+50+/-12%). A third group of newborn animals (n=7) was used to determine the renal effects of perindoprilat administration (20 microg/kg) under normoxemic conditions. RBF significantly increased (+15+/-2%) and renal vascular resistance significantly decreased (-15+/-3%), whereas GFR, mean blood pressure, and filtration fraction did not change significantly. In group 4 (n=7), perindoprilat infusion completely prevented the hypoxemia-induced alterations in GFR and renal vascular resistance and partially prevented the fall in RBF. These results demonstrate that angiotensin II modulates the renal immature microcirculation and that inhibition of its formation effectively prevents the hypoxemia-induced decrease in GFR.