Evaluation of diagnostic criteria of acute renal failure in premature infants

Acute Kidney Injury: Diagnosis and Management

Pediatric medicine is growing in complexity and an increasing number of children with co-morbidities are exposed to potential renal damage. Initially ill-defined and thought to be mostly a transient phenomenon in children, acute kidney injury (AKI) has now emerged as a complex clinical syndrome independently associated with increased mortality and morbidity, including the development of chronic renal sequelae. Recent advances in molecular nephrology have better elucidated the early phase of AKI, where evidence of renal tissue damage is associated with adverse outcomes even without decrease in glomerular filtration rate, illustrating the flaws of the old paradigm based solely on an insensitive filtration marker, the serum creatinine. Prevention, prompt evaluation and early interventions are of essence to decrease AKI incidence and severity. Emerging data reveal that AKI is commonly encountered in hospitalized children, especially critically ill ones, hence the importance for all clinicians to be able to identify high risk patients, recognize AKI early and be comfortable with the initial medical management. In recent years, significant advances have been made in AKI definition and prediction, allowing early preventive measures in high risk children that are now proven to reduce AKI incidence. This review covers recent advances in the diagnosis, risk stratification, prevention and management of AKI in children.

Acute kidney injury in a single neonatal intensive care unit in Turkey

BACKGROUND

Although advances in perinatal medicine have increased the survival rates of critically ill neonates, acute kidney injury (AKI) is still one of the major causes of mortality and morbidity in neonatal intensive care units. This study aimed to determine the prevalence of AKI and analyze demographic data and risk factors associated with the mortality or morbidity.

METHODS

Of 1992 neonates hospitalized between January 2009 and January 2011, 168 with AKI were reviewed in the study. The diagnosis of AKI was based on plasma creatinine level >1.5 mg/dL, which persists for more than 24 hours or increases more than 0.3 mg/dL per day after the first 48 hours of birth while showing normal maternal renal function.

RESULTS

The prevalence of AKI was 8.4%. The common cause of AKI was respiratory distress syndrome, followed by sepsis, asphyxia, dehydration, congenital anomalies of the urinary tract, congenital heart disease, and medication. The prevalence of AKI in neonates with birth weight lower than 1500 g was about three-fold higher than in those with birth weight higher than 1500 g (P<0.05). Pregnancy-induced hypertension, preterm prolonged rupture of membranes, and administration of antenatal corticosteroid were associated with increased risk of AKI (P<0.05). Umbilical vein catheterization, mechanical ventilation and ibuprofen therapy for patent ductus arteriosus closure were found to be associated with AKI (P<0.05). The overall mortality rate was 23.8%. Multivariate analysis revealed that birth weight less than 1500 g, mechanical ventilation, bronchopulmonary dysplasia, anuria, and dialysis were the risk factors for the mortality of infants with AKI.

CONCLUSIONS

Prenatal factors and medical devices were significantly associated with AKI. Early detection of risk factors can reduce the mortality of AKI patients.

Toward the optimal clinical use of the fraction excretion of solutes in oliguric azotemia

While the fractional excretion of solutes have long been considered excellent research tools to investigate tubular physiology, their clinical use has become common over the last 40 years in the diagnoses of many disorders; however, none have reached the clinical utility of the fractional excretion of sodium in the ability to distinguish pre-renal azotemia from acute tubular necrosis. Nevertheless, there are many drugs and medical conditions that interfere with that utility and recently other solutes, including urea, uric acid and lithium, have been recently investigated to improve the diagnostic ability in clinical situations where the fractional excretion of sodium is known to be unreliable. We review the tubular physiology of these solutes and show how the differences in tubular physiology might be exploited to develop a strategy for their optimal clinical use.

Acute renal failure in neonates

Acute renal failure (ARF) is a common condition seen in neonatal intensive care units. It is broadly classified into prerenal, intrinsic renal and post renal failure. There is no consensus on the definition of neonatal ARF. Of utmost importance is to differentiate prerenal from intrinsic renal failure. The most common causes of neonatal ARF are hypovolemia, hypotension and, hypoxia. Among several indices that are available for differentiating prerenal failure from intrinsic renal failure, fractional excretion of sodium is the preferred index. Diagnostic fluid challenge with or without frusemide is a bed side method for differentiating prerenal failure from intrinsic renal failure. Babies with ARF have to be monitored for several metabolic derangements like hyponatremia, hyperkalemia, hypocalcemia, and acidosis and have to be managed accordingly. Fluid balance should be precise in order to avoid fluid overload. It is difficult to provide adequate calories due to fluid restriction. Dialysis has to be instituted to preempt complications. Peritoneal dialysis is the easiest and safest modality. These babies need long term follow up as they are prone for long term complications.

Water and electrolyte metabolism of the micropremie

There are five problem schemas presented in this article that indicate potential contradictions in therapeutic goals: (1) shock and edema presenting upon premature birth; (2) the hyperosmolar state, problematic in patients less than 750 g birth weight; (3) the respiratory distress syndrome and respiratory failure, often complicated by patent ductus arteriosus; (4) bronchopulmonary dysplasia, resulting from prematurity and mechanical ventilation; and (5) late onset of hyponatremia, sometimes accompanied by growth failure in the recovering premature. These five problems considered together comprise a developmental continuum of illness and recovery, where appropriate fluid management has recently been demonstrated to benefit outcomes greatly. Clinicians over the past decade have encountered all of the fluid and electrolyte nightmares. Although there are many different formulations for treating each of these scenarios, recommending one approach for all patients is likely to be incorrect much of the time.

Characterization of renal tubular damage in preterm infants with renal failure

This study attempts to clarify the characteristics of renal tubular damage in preterm infants with renal failure. Sixty-one neonates (17 term and 44 preterm infants) were divided into three groups: 15 infants with intrinsic renal failure (IRF), five term and 10 preterm; 19 with pre-renal renal failure (PRF), five term and 14 preterm; and 27 without renal dysfunction (control), seven term and 20 preterm. Urine was collected for an 8 h period on the 2nd or 3rd day of life to determine the following parameters: creatinine clearance (Ccr), fractional excretion of sodium (FENa), urinary N-acetyl-beta-D-glucosaminidase (NAG) index and endothelin-1 (ET-1) excretion. Parameters of renal tubular function and/or renal tubular damage such as FENa, NAG index and ET-1 excretion were considered as a useful marker to differentiate IRF from PRF in preterm infants. However, these parameters were significantly elevated in preterm infants with PRF. These findings led us to make the following speculations: (i) renal tubular damage may easily occur in preterm infants; and (ii) there still remains difficulty in differentiation between IRF and PRF using Ccr instead of the fluid challenge test.