Effects of perinatal asphyxia and myoglobinuria on development of acute, neonatal renal failure

Neonatal Life-Threatening Nonoliguric Hyperkalemia Under Therapeutic Hypothermia

To illustrate our experience with two cases of neonatal life-threatening hyperkalemia during therapeutic hypothermia (TH) despite a normal acid-base status, urine output, and preserved renal function. Clinical cases are presented from Pediatric Intensive Care Unit (PICU) admission to the onset of the hyperkalemia, with related complications and after resolution. Similar cases were not retrieved from a critical review of pertinent literature. Severe hyperkalemia pathophysiology and risk factors have been debated. Two full-term adequate for weight female neonates were admitted to PICU because of perinatal asphyxia who underwent TH. Prenatal history was completely uneventful, nor hereditary genetic conditions were reported; moreover, long-term follow-up ruled out any metabolic or renal disease. Despite an accurate evaluation of previous clinical series and literature on TH and perinatal asphyxia, these hyperkalemic episodes remain unexplained. The hypoxic-ischemic insult may affect multiple organs, mainly central nervous system, heart, lung, and kidneys; acute muscle breakdown and consequent rising of myoglobin may also have a precipitating role in acute kidney failure (AKF) and hyperkalemia. Electrolyte imbalance is a possible finding as a consequence of combined cell injury and AKF. In contrast, an isolated severe hyperkalemia is exceedingly rare in nonoliguric neonates.

The prevalence of acute kidney injury in neonates with birth asphyxia is higher in the Democratic Republic of Congo than in Western countries

AIM

There is very little data on acute kidney injury in neonates in Africa. The aim of this study was to describe the frequency of acute kidney injury and the outcome in neonates admitted to hospital for asphyxia in the Democratic Republic of Congo.

METHODS

A descriptive study was conducted in the country's capital Kinshasa. Acute kidney injury was diagnosed within three days of life when the creatinine clearance was ≤16 mL/min/1.73 m².

RESULTS

Acute kidney injury occurred in 54.3% of the 35 neonates with severe perinatal asphyxia and 31.4% of the 35 neonates with moderate perinatal asphyxia, and this rate was higher than the prevalence reported in Western countries. Prerenal acute kidney injury occurred in 12 (40%) of the 30 neonates with acute kidney injury. The frequency of oliguria was significantly higher in neonates with severe perinatal asphyxia than moderate perinatal asphyxia (73.7% vs. 45.5%), and mortality was also higher in neonates with severe rather than moderate perinatal asphyxia (57.9% vs. 36.4%).

CONCLUSION

The prevalence of acute kidney injury was higher in asphyxiated patients in the Democratic Republic of Congo than in Western countries. It was also higher in neonates with severe rather than moderate perinatal asphyxia.

Utility of urine myoglobin for the prediction of acute renal failure in patients with suspected rhabdomyolysis: a systematic review

BACKGROUND

Urine myoglobin continues to be used as a marker of rhabdomyolysis, particularly to assess risk of developing acute renal failure and evaluate treatment success. We sought to determine the predictive validity of urine myoglobin (uMb) for acute renal failure (ARF) in patients with suspected rhabdomyolysis.

METHODS

We performed a broad systemic review of the literature from January 1980 to December 2006 using the search terms myoglobin$ AND (renal OR ARF OR kidney). Only primary studies published in English where uMb measurement was related to ARF were included.

RESULTS

Of 1602 studies screened, 52 met all selection criteria. The studies covered a wide spectrum of etiologies for rhabdomyolysis, dissimilar diagnostic criteria for ARF and rhabdomyolysis, and various methods of uMb measurement and were mostly case series (n = 32). There was poor reporting on the uMb method, and 17 studies failed to provide any information about the method. The reporting of clinical criteria for ARF with respect to timing, description, performance, and interpretation also lacked adequate detail for replication. Eight studies (total 295 patients) had data for 2-by-2 tables. Sensitivity of the uMb test was 100% in 5 of the 8 studies, specificity varied widely (15% to 88%), and CIs around these measures were high. Pooling of data was not possible because of study heterogeneity.

CONCLUSIONS

There is inadequate evidence evaluating the use of uMb as a predictor of ARF in patients with suspected rhabdomyolysis.

[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.

Low adjusted serum ionized calcium concentration shortly after birth predicts poor outcome in neonatal hypoxic-ischemic encephalopathy

AIM

Hypoxic-ischemic reperfusion injury causes either necrosis or apoptosis, and the influx of ionized calcium into cells is the major cause of both types of cell death. The aim of this study was to investigate whether or not the serum ionized calcium concentration in neonates with hypoxic-ischemic encephalopathy (HIE) could be used to predict their outcome.

METHODS

Serum samples were obtained shortly after birth from 20 HIE neonates who had not urinated or received treatment with calcium. Serum ionized calcium concentrations were adjusted for pH using a correction formula. Twelve neonates without any disease were selected as a control. The results were compared between nine HIE neonates who made a full recovery, 11 who died or had neurologic deficits, and 12 normal neonates.

RESULTS

Considered together, the two HIE groups had lower serum ionized calcium concentrations (1.05 +/- 0.10 mmol/L) than the control group (1.22 +/- 0.07 mmol/L; P < 0.0001). Moreover, serum ionized calcium concentrations in the group with the poor outcome (0.99 +/- 0.07 mmol/L) were lower than those in the group that made a full recovery (1.13 +/- 0.06 mmol/L; P=0.0016).

CONCLUSIONS

The serum ionized calcium concentrations shortly after birth were significantly lower in neonates with HIE who had a poor outcome. Low concentrations may reflect multiple organ damage, particularly involving the brain.

The effects of asphyxia on renal function in fetal sheep at midgestation

To determine whether damage to the fetal kidneys plays a role in the formation of hydrops fetalis following a severe asphyxial episode, six chronically catheterised fetal sheep, at 0.6 gestation (90 days; term 150 days), were subjected to 30 min of complete umbilical cord occlusion. During the occlusion period, mean arterial pressure, heart rate and renal blood flow decreased (P < 0.001). There were falls in arterial pH and PO2 and a rise in PCO2 (P < 0.001). Urine flow rate decreased (P < 0.005), as did the excretion rates of sodium and osmoles (P < 0.05). However, by 60 min after release of occlusion, urine flow rate was similar to control values. By the end of day 1, most renal variables returned to normal. At post-mortem, 72 h after occlusion, all asphyxiated fetuses showed gross signs of hydrops. Body weight was higher (P < 0.05) due to fluid accumulation in the peritoneal (P < 0.001) and pleural cavities (P < 0.05) as well as subcutaneously (P < 0.05). Amniotic/allantoic fluid volume was increased (P < 0.05). Kidney histology was normal except for clusters of apoptotic cells in some proximal tubules. In conclusion, this severe asphyxial episode caused surprisingly little damage to the kidney and the changes in renal function were very transient. Thus renal damage was not important in the development of hydrops. Possibly, the midgestation fetal kidney has a limited capacity to increase urinary salt and water excretion in response to increased fluid delivery across the placenta.

Antibacterial-induced nephrotoxicity in the newborn

Antibacterials are the primary cause of drug-induced kidney disease in all age groups and these agents bring about renal damage by 2 main mechanisms, namely, direct and immunologically mediated. For some antibacterials (aminoglycosides and vancomycin) nephrotoxicity is very frequent but generally reversible upon discontinuation of the drug. However, the development of acute renal failure with these agents is possible and its incidence in the newborn seems to be increasing. Antibacterials are very often used in the neonatal period especially in very low birthweight neonates. The role of neonatal age in developing nephrotoxicity has still to be defined. Since the traditional laboratory parameters of nephrotoxicity are abnormal only in the presence of substantial renal damage, the identification of early non-invasive markers of the renal damage (urinary microglobulins, enzymes and growth factors) is of importance. Aminoglycosides and glycopeptides are still frequently used, either alone or in combination, despite their low therapeutic index. Numerous factors intervene in bringing about the kidney damage induced by these 2 classes of antibacterials, such as factors related to the antibacterial itself and others related to the associated pathology as well as pharmacological factors. Nephrotoxicity can be caused by the beta-lactams and related compounds. Their potential to cause nephrotoxicity decreases in the order: carbapenems > cephalosporins > penicillins > monobactams. Third generation cephalosporins are frequently used in neonates. However, they are well tolerated compounds at the renal level. The nephrotoxicity of other classes of antibacterials is not discussed either because they are only used in neonates in exceptional circumstances, for example, chloramphenicol and cotrimoxazole (trimethoprim-sulfamethoxazole) or are not associated with significant nephrotoxicity, for example macrolides, clindamicin, quinolones, rifampicin (rifampin) and metronidazole. Antibacterial-induced nephrotoxicity is an important parameter to be considered when treating the newborn and this is particularly true when use of a combination of different antibacterials and/or drugs with a nephrotoxic potential is being considered. However, other parameters, such as antibacterial spectrum, pharmacokinetics, post-antibacterial effect, clinical efficacy, general adverse effect profile and cost, must also be considered in the choice of antibacterial therapy in the neonate. Knowledge of the renal safety of antibacterials and the correct approach to therapeutic drug monitoring may be useful elements for preventing iatrogenic renal disorders.

Indices of renal tubular function in perinatal asphyxia

AIMS

To determine and compare two urinary indices of renal tubular function, N-acetyl-glucosaminidase (NAG) and beta 2-microglobulin (beta 2 M), in healthy term neonates and babies with perinatal asphyxia.

METHODS

In a prospective case-control study using asphyxiated (n = 35) and normal control (n = 55) infants, urinary NAG and beta 2 M were assayed at 24-48 hours of life, 4-6 days, and 4-6 weeks.

RESULTS

NAG and beta 2 M were significantly increased at 24-48 hours and 4-6 days in the asphyxiated infants compared with the controls. Increased NAG values reflect the degree of perinatal asphyxia more than do beta 2 M. Gentamicin also increased NAG excretion, but to a lesser extent than did perinatal asphyxia.

CONCLUSIONS

NAG (+/- beta 2 M) may be a useful marker of perinatal asphyxia. Urinary NAG concentrations correlate with the severity of perinatal asphyxia.

Urinary N-acetyl-beta-D-glucosaminidase excretion in term and preterm neonates

Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion was measured in term and preterm neonates on days 1, 4, 7, 14 and 28 of life. Urinary NAG showed a peak level on day 4 or 7 in these infants. In addition, it tended to be higher with the degree of prematurity. In sick preterms who were depressed at birth and had respiratory failure, the NAG activity was further elevated during the first 2 weeks, suggesting the presence of renal tubular injury in this period. These observations thus suggest that urinary NAG may be a sensitive measure of renal maturation or damage in neonates.

Evaluation of diagnostic criteria of acute renal failure in premature infants

A prospective study was performed to investigate the validity of renal failure index (RFI) or fractional excretion of sodium (FENa) in preterm infants. The subjects were 128 newborn infants, 72 with oliguria and 56 without renal dysfunction (control). Oliguric infants were divided into two categories: acute renal failure (ARF) and prerenal failure (PRF), according to creatinine clearance (Ccr). Furthermore, all subjects were divided into four groups according to gestation, that is, 38 infants with gestational age of 25-28 weeks (group 1), 28 with 29-30 weeks (group 2), 38 with 31-36 weeks (group 3) and 24 of > 37 weeks (group 4). As a result, differentiation between ARF and PRF was valid when the RFI or FENa was used in infants of > 29 weeks gestation (groups 2, 3 and 4). Although infants of > 31 weeks gestation (groups 3 and 4) who present with an RFI > 3 or an FENa > 3% may be diagnosed as having ARF, infants in group 2 with an RFI of > 8 or an FENa of > 6% may be diagnosed as having ARF. For the infants in group 1, the application of RFI or FENa for diagnosis of ARF may be limited because of some overlap among the groups.

Acute neonatal morbidity and long-term central nervous system sequelae of perinatal asphyxia in term infants

Twenty-eight term neonates with severe perinatal asphyxia were referred to a tertiary neonatal intensive care unit (NICU). The morbidity of asphyxia included involvement of the pulmonary (n = 24 infants), central nervous system (n = 22), renal (n = 15), cardiac (n = 14), metabolic (n = 13) and hematologic (n = 10) systems. The majority of neonates had more than three organ systems involved. Twenty-four neonates survived the neonatal course and at NICU discharge all system effects other than the central nervous system had resolved. At 5 years (60 months), 14 children had a normal neurologic examination, 9 had spastic quadriplegia and one had hemiplegia. Nine children had a McCarthy General Cognitive Index (GCI) greater than or equal to 84, 3 had a GCI between 68 and 83 and 12 scored less than 67. Neonatal seizures, renal problems, microcephaly at 3 months, and post-neonatal seizures were associated with an abnormal neurologic outcome or a GCI less than 67. A neurologic examination during the first year of life may reveal whether children with birth asphyxia will be relatively normal at age 5 years or whether they will show considerable delay.

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.

Hypoxanthine, xanthine and uridine in body fluids, indicators of ATP depletion

Measurements of hyp, xan and urd in body fluids can provide evidence of energy, ATP, depletion in the body, in organs or in cells. Such information is clinically useful in the many diseases in which cellular energy supplies cannot be maintained like perinatal asphyxia, hydrocephalus and vascular insufficiency in brain, heart, limbs, kidneys or other organs. Similar HPLC methods using reversed-phase C18 columns and quantitation by UV absorption have been employed in a variety of centres to yield almost identical results. These have been assembled in this review to form a series of reference values. The current analytical problems are reviewed. Since concentrations of hyp and xan may alter independently situations are discussed in which separate measurements rather than their summed, total oxypurine concentrations are needed. The biochemistry and physiology underlying the use of such analyses is examined to guide sampling of the appropriate body fluid at a relevant time and to avoid oversimplified interpretation of results as well as unnecessary arguments. Specifically: (1) Intracellular concentrations of hyp and xan are inversely related to adenylate energy change and therefore to the energy currency of the cell ATP. Uridine in tissues is similarly 'controlled'. (2) There is extensive evidence that large increases in hyp, xan and urd in body fluids indicate ATP depletion. (3) Small changes in hyp probably reflect alterations of ATP turnover. (4) Xanthine arises mainly from guanine and can change independently of hyp. (5) Clinically useful information is obtainable from hyp and xan concentrations in CSF, amniotic fluid, urine and plasma. Extensive clinical correlations are reviewed. At present we are in a development phase for which HPLC is ideal but the most efficient way to perform and use such analyses in routine clinical practice remains to be established.

Clinical and biochemical assessments of damage due to perinatal asphyxia: a double blind trial of a quantitative method

Using conventional criteria, a series of 26 infants was selected for intrapartum asphyxia from about 4000 deliveries over one year at a single hospital to assess the efficacy of a new biochemical method. Tissue damage was estimated from urinary excretion of hypoxanthine, an important and central intermediate in purine metabolism. The overall pattern showed agreement between the grading (by previously accepted methods) of asphyxia in the perinatal period and our new biochemical approach. The association with handicap at one year of age following asphyxia was complex. This biochemical technique could be used to exclude postasphyxial damage as a cause of clinical disturbances and to select a small group (0.1% of all births) who require further investigation for rarer disorders which may also cause long term handicap.