Breath pentane as a marker for lipid peroxidation and adverse outcome in preterm infants.

AIM: To test the hypothesis that complications of neonatal intensive care are related to increased oxygen derived free radical activity, using breath pentane as a marker of lipid peroxidation. METHODS: Exhaled breath was collected daily from 57 ventilated preterm infants and pentane concentration measured by gas chromatography. RESULTS: High peak pentane exhalation was significantly associated with low gestational age, mortality, intraventricular haemorrhage and retinopathy of prematurity. Peak pentane was not significantly associated with the development of chronic lung disease. CONCLUSIONS: The demonstration that pentane exhalation is related to the course of neonatal disease and its outcome is consistent with the hypothesis that lipid peroxidation is associated with these illnesses, and may contribute to their severity. If this is a causal relation, antioxidant treatments could prove useful in reducing their severity. Measurement of breath pentane might assist in the assessment of antioxidant strategies prior to more extensive clinical trials.

Does total antioxidant status relate to outcome in very preterm infants?

1. In healthy humans, a balance exists between oxygen-derived free-radical production and their removal by antioxidants. In preterm infants inadequate antioxidant defences may contribute to the pathogenesis of some of the complications of prematurity. 2. Plasma total antioxidant status and malondialdehyde concentration were measured during the first 11 days of life in 25 infants to determine whether increased lipid peroxidation is associated with low extracellular antioxidant status. In a second group of infants, total antioxidant status was quantified within 12 h of birth, and subsequently on days 4 and 10 to investigate the hypothesis that adverse neonatal outcome is associated with low antioxidant status. 3. There may be a weak negative correlation between the total antioxidant status of infants and the lipid peroxidation marker malondialdehyde in plasma (r = -0.24, P = 0.056, n = 89) during the first 11 days of life. In the second group of infants, total antioxidant status was found to be significantly related to plasma urate and bilirubin levels, but not to adverse neonatal outcomes such as chronic lung disease, intraventricular haemorrhage, retinopathy of prematurity or death. 4. If adverse neonatal outcomes are due to inadequate antioxidant defences, these are likely to be intracellular or localized rather than general extracellular deficiencies.

Comparison of urinary and plasma malondialdehyde in preterm infants.

The measurement of malondialdehyde (MDA) in biological fluids remains a popular method for the quantification of free radical damage to lipids in vivo. Several diseases of prematurity are thought to be related to oxidative injury and previous studies have found elevated MDA in plasma and urine in preterm infants. Our aim was to investigate the relationship between plasma and urinary MDA levels in preterm infants during the first week of life using a high-performance liquid chromatography (HPLC) based, thiobarbituric acid (TBA) assay with paired plasma and urine samples. We obtained 50 paired samples, and were unable to demonstrate a relationship between the two parameters after the first day of life. In 18 cases a further urine sample was collected 24 h later. There was a positive correlation (r = 0.54, P = 0.02) between plasma MDA and urinary MDA 24 h later. The finding that plasma changes in MDA are reflected in urine 24 h later validates the use of urinary MDA as a marker of whole body lipid peroxidation in populations without renal disease.

Pentane measurement in ventilated infants using a commercially available system.

The measurement of breath pentane as a marker of lipid peroxidation has recently been criticized. Problems encountered include the coelution of isoprene with pentane, contamination with exogenous pentane, and the influence of elevated oxygen concentration. The aim of this project was to investigate and evaluate the Chrompack 9001 Gas Chromatograph, using thermal desorption and cryofocussing and an Al2O3/KCl PLOT column with FID, for use in the measurement of breath pentane in ventilated preterm infants. We have clearly separated isoprene from n-pentane and used hydrocarbon free air to clear the airways and avoid contamination with exogenous pentane. Samples should be stored in Tedlar bags for a maximum of 48 h and on capped desorption tubes for no longer than 24 h. Patient variability was relatively high (mean 18%, n = 4); thus, all patients were sampled in duplicate. No correlation was found between fractional inspired oxygen concentration (FiO2) and exhaled pentane in preterm infants ventilated for respiratory distress syndrome. In conclusion, we feel that despite the pitfalls and technical difficulties, with careful attention to detail it is possible to reliably measure breath pentane in ventilated preterm infants as an index of lipid peroxidation.

Low-dose vancomycin prophylaxis reduces coagulase-negative staphylococcal bacteraemia in very low birthweight infants.

Very low birthweight (VLBW) infants undergoing neonatal intensive care are at risk of infection with coagulase-negative staphylococci (CONS). This study investigates the efficacy of twice daily, 1 h infusions of vancomycin (5 mg kg) in reducing CONS infection in VLBW infants receiving parenteral nutrition. Of 72 infants in the study, 37 were randomized to vancomycin and 35 to the control group. Clinical variables and mortality were similar in both groups. In the vancomycin group, 11 infants had one or more episodes of CONS bacteraemia compared with 17 in the control group. Two babies in the treatment group had more than one episode of CONS bacteraemia, compared with nine in the control group (P = 0.02). There were 13 episodes of CONS bacteraemia in the vancomycin group compared with 29 in the control group. When only positive blood-cultures associated with a rise in C-reactive protein were considered, there were six episodes of CONS bacteraemia in the vancomycin group compared with 18 in the control group. Similarly there were five infants with one or more CONS infections compared with 11 in controls and one with more than one episode compared with six in the control group (P = 0.05). Prophylaxis with intermittent low-dose vancomycin infusions may help reduce recurrent CONS bacteraemia in VLBW infants receiving parenteral nutrition.

Prediction of chronic neonatal lung disease on day 4 of life.

UNLABELLED: Clinical parameters, available on day 4, were collected for 204 ventilated neonates < 32 weeks gestation. Logistic regression was used to identify factors significantly and independently associated with chronic neonatal lung disease (CNLD) at 36 weeks postconception, which developed in 29% of neonates. At 36 weeks birth weight, peak inspiratory ventilator pressure and requirement for assisted ventilation on day 4 were such factors. The logistic regression equation for this association was applied to each infant resulting in a value between 0 and 1. By knowing which neonates developed CNLD, the discriminatory ability in this value was assessed. A receiver-operator characteristic curve for this value had an area under the curve of 0.97 (SE 0.03) in a unrelated population. A logistic equation value > 0.4 had a sensitivity of 90% and a specificity of 88% in predicting CNLD at 36 weeks. CONCLUSION: Use of logistic regression to identify factors independently associated with chronic drug disease at 36 weeks postconception, allowed accurate prediction of this disorder. This would allow reduction in size of randomised trials of early intervention in chronic lung disease.

Practical peritoneal dialysis--the Tenckhoff catheter in acute renal failure.

The problem of acquiring secure peritoneal access encompasses most of the history of peritoneal dialysis. We review the catheters available for children and describe a simple method of insertion of Tenckhoff catheters for acute dialysis. Two series of Tenckhoff catheters inserted in this way are presented and compared with results obtained with trocar- and guidewire-inserted catheters. Tenckhoff catheters inserted as described allow significantly longer periods of dialysis (P < 0.02) with significantly fewer problem episodes (P < 0.001). We conclude that the use of the Tenckhoff catheter for acute dialysis, when inserted in the way described, confers significant advantages over other catheters and permits secure peritoneal access.