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

Correlation between Apgar score and urinary uric acid to creatinine ratio in perinatal asphyxia

A randomized case control hospital based study was conducted over 12 months time on 31 asphyxiated and 31 normal newborn to see whether urinary uric acid can be used as a marker of perinatal asphyxia and can be correlated with the clinical diagnosis by Apgar score. Uric acid and creatinine were estimated in spot urine within 24 hours after birth in both cases and controls. A ratio between concentrations of uric acid to creatinine was estimated and compared between cases and controls. It was found that the ratios were significantly higher in cases than controls (3.1± 1.3 vs 0.96± 0.54; P < 0.001) and among asphyxia patients, a significant negative linear correlation was found between the uric acid to creatinine ratio and the Apgar score (r = -0.857, P < 0.001). So urinary uric acid to creatinine ratio can be used as an additional non-invasive dispace, easy and at the same time early biochemical marker of birth asphyxia which biochemically supports the clinical diagnosis and severity grading of asphyxia by Apgar score.

Purine metabolism of uric acid urolithiasis induced in newborn piglets

To clarify the relationship between uric acid urolithiasis and purine catabolites in newborn piglets, the incidence of uric acid urolithiasis and the plasma concentrations of xanthine, hypoxanthine, uric acid and allantoin were examined in 32 piglets. The newborn piglets were divided into two groups: normal (over 1.2 kg, n = 18, group N) and low body weight (below 0.9 kg, n = 14, group L). The animals in both groups were given water (non-nutrition, n = 11, treatment W), artificial milk (normal nutrition, n = 12, treatment M), or a combination of water and allopurinol (prophylactic treatment for the urolithiasis, n = 9, treatment A), during the first 60-hr of birth. At necropsy, the incidence of urolithiasis was higher in the piglets that received treatment W than those in the treatment M or A in both the N and L groups. In group L, the plasma xanthine, hypoxanthine and uric acid concentrations were markedly increased in the piglets that underwent treatment W compared with the treatment M. In both the N and L groups, the plasma allantoin concentration was higher in the treatment W piglets as compared with the treatment M piglets. These results suggested that the occurrence of uric acid urolithiasis in the newborn piglets is attributable to increased purine catabolites due to a starvational condition after birth.

Value of the urinary uric acid to creatinine ratio in term infants with perinatal asphyxia

The diagnosis of perinatal asphyxia is often inexact and present techniques for assessing its severity are unsatisfactory. The purpose of this study was to describe prospectively the value of the urinary uric acid to creatinine (UA/Cr) ratio in showing increased uric acid excretion in early spot urine samples for the identification of perinatal asphyxia, and to assess the relationship between the urinary UA/Cr ratio and the severity of hypoxic-ischemic encephalopathy. Twenty-seven fullterm infants with perinatal asphyxia were compared with 40 healthy controls. The UA/Cr ratio was higher in the asphyxiated group when compared with controls (2.11 +/- 0.83 vs 0.72 +/- 0.39 P < 0.001). Furthermore, there was a correlation between the UA/Cr ratio and the severity of the encephalopathy (r = 0.84; P < 0.001). The UA/Cr ratio was found to be a good, simple screening test for the early assessment of perinatal asphyxia.

The importance of the measurement of ATP depletion and subsequent cell damage with an estimate of size and nature of the market for a practicable method: a review designed for technology transfer

ATP is the energy currency of cells. ATP depletion is a central process in pathogenesis, in particular ischaemia, hypoxia and hypoglycaemia. ATP depletion in cells can be indirectly measured from the increased concentrations of extracellular hypoxanthine, a central intermediate in the metabolism of ATP. Cell damage secondary to ATP depletion can also be measured from extracellular hypoxanthine. The relevant biochemistry and physiology is briefly reviewed. Since market size is needed for investment decisions that would allow technology transfer, the numbers of hypoxanthine analyses that are clinically justified from the extensive published evidence are calculated per million population from UK, Norwegian and other evidence. The concentration of oxygen in blood is measured to estimate whether mitochondrial oxidative phosphorylation is adequate. Measurements of bicarbonate are used to estimate anaerobic glycolysis. Since the indirect estimation of ATP depletion is a major objective of blood gas and acid-base analyses, the number of such analyses per million population provides a good estimate of potential market size for a more direct method of estimating ATP depletion. A method is required for the rapid, dispersed emergency analyses needed clinically. Routes for method development are indicated. Competition, risks, acceptability, consumer motivation and timetables are indicated for the development phase. There are medicolegal pressures, especially in the USA, for the proposed advances to be widely used.

Plasma hypoxanthine reacts more abruptly to changes in oxygenation than base deficit and uric acid in newborn piglets

Previously, high postmortem concentrations of hypoxanthine have been found in vitreous humor of children dying from sudden infant death syndrome (SIDS). We wanted to investigate further the accumulation of hypoxanthine in vitreous humor during hypoxia. Twenty-four piglets aged 9-15 days were exposed to continuous hypoxemia (180 min 11% O2, n = 6), long interval intermittent hypoxemia (60 min 11% O2, 20 min room air, n = 7) or short interval intermittent hypoxemia (10 min 9% O2, 10 min room air with (n = 6) or without (n = 5) superimposed ligation of both carotid arteries). The increase in vitreous humor Hyp was four-fold higher (p < 0.01) with ligation of the carotid arteries (14 +/- 2.4 to 38 +/- 8.9 mumol/l) than without ligation (15 +/- 2.8 to 21 +/- 5.9 mumol/l). During continuous hypoxemia, plasma Hyp (r = 0.85), Xa (r = 0.89) uric acid (UA) (r = 0.85), and base deficit (BD) (r = 0.78) increased almost linearly (p < 0.001). Plasma Hyp responded more abruptly to changes in oxygenation than base deficit (BD) and UA. Ligation of the carotid arteries had a strong impact on Hyp accumulation in vitreous humor, suggesting that vitreous humor Hyp is not merely a filtration product of plasma Hyp, but reflects local hypoxia/ischemia in the eye.

Is post-hypoxic-ischemic cell damage associated with excessive ATP consumption rather than a failure of ATP production?

Secondary cell damage after ATP depletion due to hypoxia or ischemia is clinically important because it correlates with residual effects; post-hypoxic-ischemic fits can be associated with later cerebral palsy. The mechanisms involved in delayed secondary cell damage are not clear, possibly because extensive relevant evidence is often fragmented. However, a sequence of changes can be suggested; this cross-linked sequence is tentatively outlined in this review. The outline suggests explanations for otherwise ill-understood clinical disturbances such as the loss of inhibitory control in damaged cells and the well documented reduction of cellular ATP. Loss of control may be due to reduced synthesis of control proteins and the reduced ATP concentration may be due to increased energy consumption.

Effects of hypoxia on urinary organic acid and hypoxanthine excretion in fetal sheep

Severe birth asphyxia leads to a transient organic aciduria and increased hypoxanthine excretion. To investigate its origin and timing, we analyzed urine from 12 late gestation fetal sheep in utero subjected to moderately severe isocapnic hypoxia for 1 h. In six fetuses the carotid sinus nerves were cut to determine whether reflex peripheral vasoconstriction contributed to the changes in excretion. After a control period of 1 h, maternal inspired oxygen was reduced for 1 h so that fetal arterial oxygen tension fell significantly from 2.86 +/- 0.12 kPa (mean +/- SEM) to 1.55 +/- 0.04 kPa. The ewes were returned to normoxia, and monitoring was continued for 1 h. Fetal heart rate, arterial blood pressure, and femoral arterial blood flow (intact fetuses only) were recorded, and arterial pH, blood gases, and lactate were measured. Urine collected via a bladder catheter was analyzed for organic acids and hypoxanthine with gas chromatography-mass spectrometry. In intact fetuses, hypoxia increased excretion of hypoxanthine and several organic acids, notably lactic acid and intermediates of valine catabolism. Changes were apparent by 15 min, significant by 45 min, and maximal after reoxygenation. In denervated fetuses, there were small, significant, increases in organic acids and hypoxanthine by 45 min of hypoxia, but there was no surge in excretion posthypoxia. Hypoxia caused a large, significant, fall in femoral arterial blood flow in intact fetuses. We conclude that the extent of the reflex peripheral vasoconstriction, particularly in skeletal muscle, determines the amount of organic acid and hypoxanthine excretion and may explain similar biochemical disturbances after birth asphyxia. Urinary lactic acid measurement has a potential value for grading birth asphyxia.

Introduction to the age-related diagnosis (ARD) index: an age at presentation related index for diagnostic use

Development and, therefore, age is important in paediatrics. Diagnostically useful data from this journal has been related to age and organized to form an age-related diagnostic (ARD) index. The ARD index is designed for non-expert clinical and laboratory workers to use in the early phases of diagnosis and as an addition to existing diagnostic schemes. Entry to the index is from the age at clinical presentation. Each entry is a sequence starting with clinical and laboratory presentations, clinical course, laboratory key investigations and finally diagnosis with volume and page numbers of the original article, the primary source. Within age groups, entries are grouped by diagnoses with the commonest diagnosis first; this has the effect of roughly but not precisely grouping similar clinical and laboratory findings.

Mixed venous oxygen saturation in the newborn. Can we and should we measure it?

Conventional measurements of oxygenation used in the critical care of sick newborn infants are limited to arterial blood. This approach fails to describe fully the physiological economy of oxygen in terms of supply (systemic oxygen transport), demand (oxygen consumption), or functional reserve (mixed venous oxygen content). The relationship between supply and demand can be described by the fractional oxygen uptake, which can be determined from arterial (SaO2) and mixed venous (Sv-O2) oxygen saturations. Fractional oxygen uptake = (SaO2 - Sv-O2)/SaO2. Review of the literature shows that conventional methods of continuous monitoring of arterial oxygen tension or content have had little measurable effect on the incidence of retinopathy of prematurity or on the survival of low birthweight infants. In hypoxic states, oxygen can be almost completely extracted by the tissues. However, a critical value for fractional oxygen extraction can be recognised which reflects a critical value for systemic oxygen transport. While the pulmonary artery is the ideal site for the measurement of mixed venous oxygen content, blood sampled from the mid-lateral site of the right atrium is higher in mean oxygen saturation by only 0.7 (SE 0.1) vol.%, indicating that the effect of incomplete mixing is very small. The difference in oxygen saturation between right atrium and pulmonary artery remains variable, and this may reflect either true variation of central venous saturation or instrument error. Because of this, central venous oxygen saturation may be of limited use for the measurement of oxygen consumption, cardiac output or fractional oxygen extraction. The level of central venous oxygen saturation as a direct measure of blood oxygen reserve is worthy of further examination.(ABSTRACT TRUNCATED AT 250 WORDS)