Dilution kinetics of H(2)18O for the measurement of total body water in preterm babies in the first week after birth

The aim of this study was to determine the kinetics of H(2)18O equilibration and elimination in preterm babies for the estimation of total body water. Thirteen, clinically stable, preterm babies of less than 32 weeks' gestation were studied in the first week after birth. Blood and urine samples were obtained for baseline measurement of 18O:16O ratio and 1 ml/kg of 10% H(2)18O (0.1 g/kg isotope) administered orally. Eleven blood samples were obtained over the next six hours and between one and four over the next 18 hours. During the same 24 hour period between three and eight urine samples were also obtained. The dilution space at zero time (volume of distribution or total body water) was estimated using double exponential curve fitting using all available points, from single samples and from linear regression on the log data using two or three samples. Equilibration time was variable and showed a significant correlation with percentage change in body weight from birth. For blood samples, the median time to equilibrium was 81 minutes (range 2 to 191). A plateau phase was not detected, with H(2)18O enrichment declining after the point of maximum enrichment. The median volume of distribution at time 0, based on double exponential curve fit analysis, was 859 ml/kg (range 755 to 995). The volume of distribution, estimated from linear regression on the log data using two serum samples obtained at three and six hours, approximated most closely to that based on exponential curve fit analysis with a median difference of -4 ml/kg (range -41 to 73). It was concluded that in most situations blood sampling at three and six hours may be acceptable. However, as equilibration time is variable and influenced by the state of expansion or depletion of body water compartments, when studying overhydration states, multiple sampling is advised in order to be certain that the elimination phase has been reached.

Changes in plasma cortisol and catecholamine concentrations in response to massage in preterm infants

The biochemical and clinical response to massage in preterm infants was assessed. Eleven stable infants, of 29 weeks' median gestational age, median birth weight 980 g, and median postnatal age 20 days, were studied. Blood samples were obtained for the determination of adrenaline, noradrenaline, and cortisol 45 minutes before the start of massage and approximately one hour after completion of massage. Cortisol, but not catecholamine, concentrations decreased consistently after massage (median difference -35.8 nmol/l; 95% confidence interval -0.5 to -94.0, Wilcoxon matched pairs). There was a slight decrease in skin temperature (median difference -0.36 degrees C, 95% confidence interval -0.09 to -0.65) but there was no change in oxygenation or oxygen requirement. This study has shown that it is possible to detect an objective hormonal change following a supposedly 'non-therapeutic' intervention in preterm infants. The development of such methods of assessment are likely to be of particular relevance in the extremely immature or ill neonate in whom behavioural evaluation cannot play more than a limited part.

Atrial natriuretic peptide, cyclic guanosine monophosphate and sodium excretion during postnatal adaptation in male infants below 34 weeks gestation with severe respiratory distress syndrome

The role of atrial natriuretic peptide (ANP), in the perinatal period, is at present unclear. In adults urinary cyclic guanosine monophosphate (cGMP) is considered an index of the biological activity of plasma ANP. The aim of this study was to determine the relationship between plasma ANP, cGMP excretion (cGMPex) and sodium excretion (Naex) in preterm infants in the first days after birth. Sequential, 4 hourly, measurements of plasma ANP, cGMPex and Naex were made in 12 male neonates of median gestational age 27 weeks (range 25-33) and median birth weight 0.981 kg (range 0.635-2.029) over a median period of 5.2 days (range 2.3-10). The ratios of cGMPex to ANP and of Naex to cGMPex were each plotted against postnatal age. The ratio of cGMPex to ANP increased ten fold in the first 3-4 days after birth but then remained relatively constant; the ratio of Naex to cGMPex showed a steady increase from birth. We conclude that, in extremely immature infants, renal sodium loss in response to cGMP increases rapidly during the first 10 days after birth. In addition, after 3-4 days from birth, plasma ANP ia associated with a constant proportionate rate of cGMP excretion though, as the plateau ratio of cGMPex to ANP varied widely between babies, cGMPex cannot be used to predict plasma ANP in cross sectional studies. These changes may reflect postnatal adaptation and/or maturation of both ANP receptors and cGMP mediated cascades. In the immediate postnatal period, plasma ANP may also have a non-renal role.

The effect of polycythemia and hypoxia on urinary N-acetyl-beta-D-glucosaminidase activity in newborns

Urinary N-acetyl-beta-D-glucosaminidase activity was assayed in fullterm and preterm polycythemic neonates, in preterm infants with hypoxia, and in healthy newborns. There were no significant differences between fullterm and preterm babies or between appropriate for gestational age and small for gestational age neonates in the normal group. N-acetyl-beta-D-glucosaminidase excretion on the first day of life was significantly raised in polycythemic newborns (P less than 0.01). Fourteen days after partial plasma exchange the enzyme activity returned to normal. N-acetyl-beta-D-glucosaminidase activities in preterm babies with respiratory distress syndrome were significantly (P less than 0.01) raised on the 1st, 2nd, 4th days and fell sharply to the 14th day. N-acetyl-beta-D-glucosaminidase isoenzyme studies revealed that urine samples taken from preterm babies with respiratory distress syndrome in the first week after birth contained increased amounts of intermediate and B isoenzyme forms while there was a concomitant reduction in the amount of the A form present.

Urinary creatinine excretion and estimation of muscle mass in infants of 25-34 weeks gestation

The urinary excretion rate of creatinine was measured over 89 days in 31 infants of gestational ages 25-34 weeks in the first week of life. Creatinine excretion was shown to have a significant positive correlation with weight and postconceptional age. Creatinine excretion factored by body weight was also positively correlated with weight and postconceptional age. Pooled analysis of published data together with our own, confirms that this correlation is important. Muscle mass was estimated from creatinine excretion rate. A regression equation was derived predicting muscle mass from birth-weight and gestational age. Muscle mass increases from 12% of birthweight at 25 weeks gestation to 19% at 34 weeks and 24% at 40 weeks. This is in agreement with classic dissection studies which showed muscle mass to be 25% of body weight at term.

The influence of postnatal respiratory adaptation on sodium handling in preterm neonates

The relationship between sodium handling and alveolar-arterial oxygen gradient (AaDO2) was studied in 26 preterm babies requiring ventilation from birth. The difference between sodium intake and urinary sodium excretion was determined in sequential, four hourly periods throughout the course of the respiratory illness. Sodium retention changed from positive (mean 1.42 mmol kg-1 day-1) during the phase of deteriorating respiratory function to negative (mean - 1.99 mmol kg-1 day-1) during improving respiratory function. This difference is highly significant (P less than 0.001). A temporal relationship is also shown, in the form of individual time plots of AaDO2 and sodium retention for each baby; changes in sodium handling parallel changes in AaDO2. The diuresis that accompanies improving respiratory function is characterised as a natriuresis, with free water clearance remaining unchanged before and after the point of improvement. We suggest that a primary change in sodium handling, triggered by postnatal respiratory adaptation, may initiate the contraction in extracellular fluid volume that characterises early postnatal existence.

Phototherapy and the use of heat shields in very low birthweight infants

The irradiance produced by phototherapy units in use on a neonatal unit was measured. The phototherapy tubes were found to decline at a variable rate. Heat shields used to decrease heat and evaporative losses in the very low birthweight infant reduce irradiance and may appreciably limit the effectiveness of phototherapy.

Congenital non-chylous pleural effusion with Down's syndrome

The association of Down's syndrome with congenital non-chylous pleural effusion is described in a preterm infant.

Outbreak of cephalosporin resistant Enterobacter cloacae infection in a neonatal intensive care unit

Enterobacter cloacae resistant to third generation cephalosporins emerged rapidly during an outbreak of serious infections due to this organism in a neonatal intensive care unit where ampicillin and gentamicin were used as first line antibiotic treatment. Organisms resistant to cephalosporins were isolated from 12 infants, six of whom developed systemic infection. Two infants died. Isolates of E. cloacae from four of five infants treated with cefotaxime showed a loss of sensitivity to this antibiotic during treatment, but in the three infants who survived sensitive organisms were again isolated after treatment had stopped. Stopping treatment with the cephalosporins, closure of the unit to new admissions, and strict cohorting of colonised infants resulted in a prompt end to the outbreak. This outbreak suggests that the routine use of third generation cephalosporins for suspected sepsis may be inappropriate in the presence of a large reservoir of organisms with the potential for rapidly developing resistance. Routine bacteriological surveillance, however, might permit their use on a rotational basis.

Interdonor incompatibility due to anti-Kell antibody undetectable by automated antibody screening

A unit of whole donor blood, the plasma of which contained anti-Kell antibody, was transfused into a Kell-negative patient who had received a unit of Kell-positive blood 4 weeks previously. A haemolytic transfusion reaction ensued. The antibody had gone undetected in routine automated screening of the donor blood. Automated antibody detection techniques do not offer reliable detection of anti-Kell antibodies.

Monoclonal antibody-based immunoassay for type A Clostridium botulinum toxin is comparable to the mouse bioassay

A monoclonal antibody (BA11) has been produced against Clostridium botulinum type A neurotoxin by the fusion of myeloma cells (P3 NS1/1-Ag4-1) with spleen cells from BALB/c mice immunized with botulinum type A neurotoxoid. The antibody bound specifically to botulinum type A neurotoxin, showing no cross-reactivity with types B and E botulinum toxins or with any of several other bacterial toxins tested. The monoclonal antibody did not bind to botulinum type A neurotoxin which had been denatured with sodium dodecyl sulfate and bound only weakly to each of the separated heavy and light subunits of the neurotoxin, suggesting a conformational requirement for the antigenic determinant of the antibody. A sensitive immunoassay for C. botulinum type A toxin with monoclonal antibody BA11 in conjunction with an enzyme amplication system has been developed which allows detection of 5 to 10 mouse 50% lethal doses ml-1 of purified neurotoxin. The assay was equally sensitive when applied to the detection of crude toxin in food stuffs; the average value for the minimum level of detectable toxin in extracts of tinned salmon or corned beef was 9 +/- 3.1 mouse 50% lethal doses ml-1.

Phototherapy for neonatal hyperbilirubinaemia: the importance of dose

The management of neonatal jaundice can be made much easier using simple methods that increase the radiant energy in the range 420 to 480 nm. Two groups of infants being treated for physiological jaundice during a period of 6 months were compared. The first group received treatment from two unmodified phototherapy units and the second from two units in which the horizontal frames housing the tube lights were lowered, thus providing a higher 'dose' of phototherapy. Measurements of irradiance from the four units were compared. An improvement in treatment was noted in the group receiving the higher dose with a decrease in duration of treatment and a greater rate of fall in the level of serum bilirubin. A dose response relationship was thus confirmed. Comparisons between previous studies are hindered by failure to recognise the varying contribution of background irradiance, the use of radiometers with differing spectral responses, and the use of different units for expressing results. Failure to appreciate the importance of dose must largely be responsible for the present wide variability in the effectiveness of phototherapy.

Congenital generalised fibromatosis

A case of congenital generalised fibromatosis is described. The need to avoid unnecessary treatments is stressed.