Use of urinary indexes in renal failure in the newborn

Management of acute kidney injury in children: a guide for pediatricians

Acute kidney injury (AKI; previously called acute renal failure) is characterized by a usually reversible increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to appropriately regulate fluid and electrolyte homeostasis. The incidence of AKI in children appears to be increasing and the etiology of AKI over the past decades has shifted from primary renal disease to multifactorial causes, particularly in hospitalized children. Renal failure can be divided into prerenal failure, intrinsic renal disease including vascular insults, and obstructive uropathies. The history, physical examination, and laboratory studies including a urinalysis and radiographic studies can establish the likely cause(s) of AKI. Once intrinsic renal failure has become established, management of the metabolic complications of AKI requires meticulous attention to fluid balance, electrolyte status, acid-base balance, and nutrition. Many children with AKI will need renal replacement therapy to remove endogenous and exogenous toxins and to maintain fluid, electrolyte, and acid-base balance until renal function improves. Renal replacement therapy may be provided by peritoneal dialysis (PD), intermittent hemodialysis (HD), or hemofiltration with or without a dialysis circuit. Many factors--including the age and size of the child, the cause of renal failure, the degree of metabolic derangements, blood pressure, and nutritional needs--are considered in deciding when to initiate renal replacement therapy and which modality of therapy to use. The prognosis of AKI is highly dependent on the underlying etiology of the AKI. Children who have AKI as a component of multisystem failure have a much higher mortality rate than children with intrinsic renal disease. Recovery from intrinsic renal disease is also highly dependent on the underlying etiology of the AKI. Children who have experienced AKI from any cause are at risk for late development of renal failure long after the initial insult. Such children need life-long monitoring of their renal function, blood pressure, and urinalysis.

Acute kidney injury in children

Acute kidney injury (AKI) (previously called acute renal failure) is characterized by a reversible increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to regulate fluid and electrolyte homeostasis appropriately. The incidence of AKI in children appears to be increasing, and the etiology of AKI over the past decades has shifted from primary renal disease to multifactorial causes, particularly in hospitalized children. Genetic factors may predispose some children to AKI. Renal injury can be divided into pre-renal failure, intrinsic renal disease including vascular insults, and obstructive uropathies. The pathophysiology of hypoxia/ischemia-induced AKI is not well understood, but significant progress in elucidating the cellular, biochemical and molecular events has been made over the past several years. The history, physical examination, and laboratory studies, including urinalysis and radiographic studies, can establish the likely cause(s) of AKI. Many interventions such as 'renal-dose dopamine' and diuretic therapy have been shown not to alter the course of AKI. The prognosis of AKI is highly dependent on the underlying etiology of the AKI. Children who have suffered AKI from any cause are at risk for late development of kidney disease several years after the initial insult. Therapeutic interventions in AKI have been largely disappointing, likely due to the complex nature of the pathophysiology of AKI, the fact that the serum creatinine concentration is an insensitive measure of kidney function, and because of co-morbid factors in treated patients. Improved understanding of the pathophysiology of AKI, early biomarkers of AKI, and better classification of AKI are needed for the development of successful therapeutic strategies for the treatment of AKI.

Acute renal failure in neonatal sepsis

OBJECTIVE

To evaluate the occurrence of acute renal failure (ARF) and the factors associated with it in cases of neonatal sepsis.

METHODS

The case control study was conducted in the referral neonatal intensive care unit of a tertiary teaching hospital. 200 out born neonates with sepsis admitted to the nursery from January to July 2003 were evaluated for presence of ARF (cases) or not (controls). Sepsis was diagnosed on the basis of either a positive sepsis screen (immature: total (I:T) neutrophil ratio > 0.2, micro-ESR > age in days + 2 mm or> 15 mm, CRP> 6 mg/dl, TLC< 5000 cells/mm3; 2 or more positive) or a positive blood culture in symptomatic neonates. ARF was defined as blood urea nitrogen (BUN)> 20mg/dl on two separate occasions at least 24 hours apart. Oliguria was defined as urine output < 1 ml/Kg/hr.

RESULTS

52 out of 200 (26%) neonates with sepsis had ARF; only 15% of ARF was oliguric. The mean gestation of neonates with ARF was similar to those without ARF (36.1+/-4.1 wks vs. 36.6+/-3.5 wk; p = 0.41). A significantly higher number of babies with ARF weighed less than 2500 gm as compared to those without ARF (86.5% vs 67.6%; p = 0.008). The association of meningitis, disseminated intravascular coagulation (DIC) and shock was also significantly higher in neonates with ARF (46.8% vs 26.2%, p = 0.01; 65.4% vs 20.3%, p < 0.001; 71.2% vs 27.0%, p < 0.001 respectively). Mortality in neonates who developed ARF was significantly higher (70.2% vs 25%, p < 0.001). Factors including gestational age, weight, onset of sepsis, culture positivity, associated meningitis, asphyxia, shock, prior administration of nephrotoxic drugs were subjected to univariate analysis for prediction of fatality in neonates with sepsis and ARF; only shock was found to be a significant predictor of fatality (p< 0.001). ARF had recovered in 22 out of 49 neonates in whom data was available; three patients had left against medical advice. The mean duration of recovery in these 22 neonates was 5.5 days (range 1-14 days). Presence of co-existing morbidities (perinatal asphyxia/congestive heart failure (CHF)/ necrotising enterocolitis (NEC)) or nephrotoxic drugs did not alter the frequency of recovery of ARF in septic neonates (45.5% vs 44.4%,p = 0.944; 41% vs 52%, p = 0.308 respectively).

CONCLUSION

Renal failure occurred in 26% neonates with sepsis. Although ARF in neonates has been reported to be predominantly oliguric, it was observed that ARF secondary to neonatal sepsis was predominantly non oliguric. Low birth weight was an important risk factor for the development of ARF. The mortality being three times higher in neonates with ARF demands a greater awareness of this entity among practitioners and better management of this condition.

Prediction of acute renal failure after birth asphyxia

Twenty-one babies of 34-41 weeks' gestational age with birth asphyxia (5 minute Apgar score less than or equal to 5 or umbilical artery pH less than or equal to 7.2) were studied during the first two days of life to find out whether the urinary excretion of tubular markers of renal function is of value in the early diagnosis of acute renal failure. Urinary retinol binding protein, myoglobin, and N-acetyl-beta-D-glucosaminidase (NAG), expressed as a ratio with urinary creatinine, were measured and excretion profiles repeated at 3-6 days in 15 infants and at 7-14 days in 11 infants. Plasma creatinine concentration, creatinine clearance, plasma myoglobin concentration, and fractional sodium excretion were measured where possible in asphyxiated infants. Control data were obtained from 50 healthy infants: 28 gave urine samples alone, 17 urine and blood, and five blood alone. Normal urinary values were derived from 17, 25, and three infants, respectively, for the three time periods. The number of control samples was limited for ethical reasons. Four asphyxiated infants had acute renal failure (group 1), four had tubular dysfunction without glomerular disturbance (group 2) and 13 had normal renal function (group 3). Group 1 were clearly identified by greatly increased urinary retinol binding protein (greater than 27,000 micrograms/mmol creatinine) and myoglobin (greater than 1500 micrograms/mmol creatinine) excretion measured in the first two days of life. In control infants the range of excretion of retinol binding protein within the same time period was 3 to 967 micrograms/mmol creatinine and urinary myoglobin was undetectable. Excretion of NAG failed to discriminate between groups 1 and 2. Acute renal failure occurred only in infants who had heavy myoglobinaemia. Tubular dysfunction in group 2 was transient and not accompanied by plasma electrolyte disturbances. We conclude that measurement of urinary excretion of retinol binding protein or myoglobin after birth is helpful in the early diagnosis of acute renal failure.