To guide future practice, perinatal trials should be much larger, simpler and less fragile with close to 100% ascertainment of mortality and other key outcomes

The Australian Placental Transfusion Study (APTS) randomised 1,634 fetuses to delayed (≥60 s) versus immediate (≤10 s) clamping of the umbilical cord. Systematic reviews with meta-analyses, including this and similar trials, show that delaying clamping in preterm infants reduces mortality and need for blood transfusions. Amongst 1,531 infants in APTS followed up at two years, aiming to delay clamping for 60 s or more reduced the relative risk of the primary composite outcome of death or disability by 17% (p = 0.01). However, this result is fragile because nominal statistical significance (p < 0.05) would be abolished by only 2 patients switching from a non-event to an event, and the primary composite outcome was missing in 112 patients (7%). To achieve more robust evidence, any future trials should emulate the large, simple trials co-ordinated from Oxford which reliably identified moderate, incremental improvements in mortality in tens of thousands of participants, with <1% missing data. Those who fund, regulate, and conduct trials that aim to change practice should repay the trust of those who consent to participate by doing everything possible to minimise missing data for key outcomes.

Normalising comparative effectiveness trials as clinical practice

There is a lack of high-quality evidence underpinning many contemporary clinical practice guidelines embedded in the healthcare systems, leading to treatment uncertainty and practice variation in most medical disciplines. Comparative effectiveness trials (CETs) represent a diverse range of research that focuses on optimising health outcomes by comparing currently approved interventions to generate high-quality evidence to inform decision makers. Yet, despite their ability to produce real-world evidence that addresses the key priorities of patients and health systems, many implementation challenges exist within the healthcare environment.

This manuscript aims to highlight common barriers to conducting CETs and describes potential solutions to normalise their conduct as part of a learning healthcare system.

Resuscitating preterm infants with 100% oxygen is associated with higher oxidative stress than room air

AIM

The starting fraction of inspired oxygen for preterm resuscitation is a matter of debate, and the use of room air in full-term asphyxiated infants reduces oxidative stress. This study compared oxidative stress in preterm infants randomised for resuscitation with either 100% oxygen or room air titrated to internationally recommended levels of preductal oxygen saturations.

METHODS

Blood was collected at birth, two and 12 hours of age from 119 infants <32 weeks of gestation randomised to resuscitation with either 100% oxygen (n = 60) or room air (n = 59). Oxidative stress markers, including advanced oxidative protein products (AOPP) and isoprostanes (IsoP), were measured with high-performance liquid chromatography and mass spectrometry.

RESULTS

Significantly higher levels of AOPP were found at 12 hours in the 100% oxygen group (p < 0.05). Increases between two- and 12-hour AOPP (p = 0.004) and IsoP (p = 0.032) concentrations were significantly higher in the 100% oxygen group.

CONCLUSION

Initial resuscitation with room air versus 100% oxygen was associated with lower protein oxidation at 12 hour and a lower magnitude of increase in AOPP and IsoP levels between two and 12 hours of life. Correlations with clinical outcomes will be vital to optimise the use of oxygen in preterm resuscitation.

Relationship between probable nosocomial bacteraemia and organisational and structural factors in UK neonatal intensive care units

OBJECTIVES

To assess the relationship between organisational and structural factors of UK neonatal intensive care units (NICUs) with risk adjusted probable nosocomial bacteraemia.

DESIGN OF STUDY

A prospective observational study of infants concurrently admitted to 54 randomly selected UK NICUs between March 1998 and April 1999.

RESULTS

Of the 13 334 infants admitted, 402 (2.97%) had probable nosocomial bacteraemia. The median unit level percentage of infants with probable nosocomial bacteraemia was 2.48% (minimum 0%, maximum 9%). The risk adjusted odds of probable nosocomial bacteraemia were increased by 1.13 (95% CI 1.07 to 1.20) for each additional level 1 cot per hand washbasin and decreased by 0.53 (95% CI 0.35 to 0.79) in infants admitted to units with an NICU infection control nurse compared with units without. There was no relation with an increase in the floor space of the unit per cot (odds ratio 0.99 (95% CI 0.98 to 1.00) per m(2)) or with the quality of hand washing signs (odds ratio 1.04 (95% CI 0.93 to 1.16) per increase in quality score).

CONCLUSIONS

There is widespread variation in rates of probable nosocomial bacteraemia in UK NICUs. Probable nosocomial bacteraemia is reduced in units with a dedicated infection control nurse and with the presence of more hand washbasins. Further research is required to identify methods to eliminate nosocomial bacteraemia.

ORACLE--antibiotics for preterm prelabour rupture of the membranes: short-term and long-term outcomes

Preterm prelabour rupture of the foetal membranes (pPROM) is the most common antecedent of preterm birth and can lead to death, neonatal disease and long-term disability. Previous small trials of antibiotics for pPROM suggested some health benefits for the neonate, but the results were inconclusive. A large, randomized, multicentre trial was undertaken to try to resolve this issue. In total, 4826 women with pPROM were randomized to one of four treatments: 325 mg co-amoxiclav plus 250 mg erythromycin, co-amoxiclav plus erythromycin placebo, erythromycin plus co-amoxiclav placebo, or co-amoxiclav placebo plus erythromycin placebo, four times daily for 10 d or until delivery. The primary outcome measure was a composite of neonatal death, chronic lung disease or major cerebral abnormality on ultrasonography before discharge from hospital. The analysis was undertaken by intention to treat. Indications of short-term respiratory function, chronic lung disease and major neonatal cerebral abnormality were reduced with the prescription of erythromycin. In contrast, the use of co-amoxiclav was associated with a significant increase in the occurrence of neonatal necrotizing enterocolitis.

CONCLUSION

Prophylactic antibiotics can play a role in preterm prelabour rupture of the membranes in reducing infant morbidity.

Hospital mortality in relation to staff workload: a 4-year study in an adult intensive-care unit

BACKGROUND

Few studies have examined mortality rates in relation to the workload of hospital staff. We investigated this issue in one adult intensive-care unit (ICU) in the UK.

METHODS

We measured ICU workload per shift during each patient's stay for all admissions between 1992 and 1995 that met criteria for adjustment of mortality risk by the APACHE II equation (n=1050). APACHE II data were validated by one observer. Measures of workload in each patient's stay included occupancy, total ICU nursing requirement as defined by the UK Intensive Care Society, and the ratio of occupied to appropriately staffed beds. Over the period, staffing was appropriate for between 4.1 and 5.3 occupied beds (1.3 nurses per patient).

FINDINGS

There were 337 deaths, 49 more (95% CI 34-65) than predicted by the APACHE II equation. Median occupancy was 5.8 beds, and median nursing requirement was 1.6 per patient. On multiple logistic regression analysis, adjusted mortality was more than two times higher (odds ratio 3.1 [1.9-5.0]) in patients exposed to high than in those exposed to low ICU workload, defined by average nursing requirement per occupied bed and peak occupancy; the unadjusted odds ratio for this comparison was 4.0 (2.6-6.2). After exclusion of measures of nursing requirement, adjusted mortality increased with the ratio of occupied to appropriately staffed beds during each patient's stay. All logistic regression models fitted the data satisfactorily.

INTERPRETATION

Variations in mortality may be partly explained by excess ICU workload. This methodology may have implications for planning and clinical governance.

A cost analysis of neonatal care in the UK: results from a multicentre study. ECSURF Study Group

BACKGROUND

A number of papers have recently been published examining the magnitude of scale economies in neonatal care and the level of activity at which these become attainable. Although these agree there is scope for economies in the production of neonatal care, they debate the extent to which such economies are attainable and how they might best be detected. A major multicentre study of neonatal units in the United Kingdom has produced costing and activity data allowing these issues to be explored afresh.

METHODS

A postal questionnaire was used to determine neonatal cost and activity levels in 57 UK neonatal units. Costs for the financial year 1990-1991 related to clinical staffing, support (such as pathology) and overheads (such as heat, light, power and administrative overheads). Activity related to the total number of care days provided and the number of these that were intensive in nature. All data were scrutinized to ensure consistent definitions. A multivariate regression analysis was used to investigate the relationship between costs and activity.

RESULTS

A double-log function relating variations in total costs to total days, case-mix and an interaction term provided the best fit to the data. The analysis suggests that significant economies of scale are possible within the observed range of provision of intensive care.

CONCLUSIONS

Significant economies of scale may be attainable. Nevertheless, these results should be carefully interpreted. In particular, the costs of neonatal care should not be examined in isolation but in relation to outcomes. In certain instances, units of inefficient scale but acceptable outcome may be defensible on grounds of ease of access.

Risk adjustment for quality improvement

We can learn what is achievable with current technologies by comparing our neonatal intensive care unit outcomes with others. Because neonatal intensive care units may vary with respect to their case-mix, risk adjustment is essential to making fair comparisons in any research that does not equalize risks through randomization. Risk adjustment first requires strict definition of each specific outcome. Then each risk factor is measured and weighted accordingly. Severity of illness scores are a special form of risk adjustment. The leading newborn illness severity scores rely on physiology-based items from bedside vital signs and laboratory tests. The mechanics of score development are discussed including item selection, definition, collection, and potential biases. The process of weighting risk factors usually involves building multivariate models. Issues of derivation, validation, discrimination, calibration, and reliability affect the utility of all scores. Once a comparison is appropriately risk-adjusted, there are important cautions about interpretation, including the source of the reference (benchmark) population, sample size, and biases from incomplete risk adjustment. Nonetheless, these findings can spur quality improvement efforts that can lead to dramatic, system-wide improvements in outcomes.

Neonatal risk scoring systems. Can they predict mortality and morbidity?

Physiology-based illness severity scores are proving their value through a wide variety of practical applications. The theoretical disadvantages noted in Table 1 have not turned out to be major problems, whereas the advantages have been quite real. Numerous studies have reported insightful comparisons between treatment groups, between NICUs, between countries, between eras, and over the course of care. Many institutions have implemented routine collection of physiology-based newborn scores. The answer to the question posed in the title is yes; neonatal risk scoring systems can predict some mortality and some morbidity. However, it is clear that this function is much less important than their application as a means of improving quality and cost. Future development will depend on commercially viable applications.

Annual league tables of mortality in neonatal intensive care units: longitudinal study. International Neonatal Network and the Scottish Neonatal Consultants and Nurses Collaborative Study Group

OBJECTIVE

To assess whether crude league tables of mortality and league tables of risk adjusted mortality accurately reflect the performance of hospitals.

DESIGN

Longitudinal study of mortality occurring in hospital.

SETTING

9 neonatal intensive care units in the United Kingdom.

SUBJECTS

2671 very low birth weight or preterm infants admitted to neonatal intensive care units between 1988 and 1994.

MAIN OUTCOME MEASURES

Crude hospital mortality and hospital mortality adjusted using the clinical risk index for babies (CRIB) score.

RESULTS

Hospitals had wide and overlapping confidence intervals when ranked by mortality in annual league tables; this made it impossible to discriminate between hospitals reliably. In most years there was no significant difference between hospitals, only random variation. The apparent performance of individual hospitals fluctuated substantially from year to year.

CONCLUSIONS

Annual league tables are not reliable indicators of performance or best practice; they do not reflect consistent differences between hospitals. Any action prompted by the annual league tables would have been equally likely to have been beneficial, detrimental, or irrelevant. Mortality should be compared between groups of hospitals using specific criteria-such as differences in the volume of patients, staffing policy, training of staff, or aspects of clinical practice-after adjusting for risk. This will produce more reliable estimates with narrower confidence intervals, and more reliable and rapid conclusions.

Predicting outcome in very low birthweight infants using an objective measure of illness severity and cranial ultrasound scanning

AIM

To investigate the feasibility of developing an objective tool for predicting death and severe disability using routinely available data, including an objective measure of illness severity, in very low birthweight babies.

METHOD

A cohort study of 297 premature babies surviving the first three days of life was made. Predictive variables considered included birthweight, gestation, 3 day cranial ultrasound appearances and 3 day CRIB (clinical risk index for babies) score. Models were developed using regression techniques and positive predictive values (PPV) and likelihood ratios (LR) were calculated.

RESULTS

On univariate analysis, birthweight, gestation, 3 day CRIB score and 3 day cranial ultrasound appearances were each associated with death. On multivariate analysis, 3 day CRIB score and 3 day cranial ultrasound appearances remained independently associated. A 3 day CRIB score > 4 along with intraventricular haemorrhage (IVH) grade 3 or 4 was associated with a PPV of 64% and an LR of 9.8 (95% confidence limits 3.5, 27.9). Only 3 day CRIB score and 3 day cranial ultrasound appearances were associated with severe disability on univariate analysis. Both remained independently associated on multivariate analysis. A 3 day CRIB score > 4 along with an IVH grade of 3 or 4 was associated with a PPV of 60% and an LR of 24.2 (95% CI 4.4, 133.3).

CONCLUSION

Incorporating objective measures of illness severity may improve current prediction of death and disability in premature infants.

Measurement properties of the Clinical Risk Index for Babies--reliabilty, validity beyond the first 12 hours, and responsiveness over 7 days

OBJECTIVES

Clinical Risk Index for Babies (CRIB) is a simple instrument used to measure clinical risk and illness severity in very low birth-weight infants. We assessed its reliability, validity beyond the first 12 hrs after birth, and responsiveness to individual change in condition after 7 days.

DESIGN

Cohort study.

SETTING

Three tertiary and three nontertiary UK hospitals.

PATIENTS

Three hundred ninety-eight infants whose birth weight was <1501 g or who were born before a 31-wk gestation period.

INTERVENTIONS

Inter- and intrarater reliability of data extraction were assessed by Pearson and intraclass correlation. To validate CRIB, we tested the correlation between clinical risk and illness severity with the risk of: a) death; b) prolonged treatment with supplemental oxygen; and c) disability at 2 yrs. Logistic regression models were fitted to assess validity and responsiveness.

MEASUREMENTS AND MAIN RESULTS

Reliability coefficients ranged from 0.76 (95% confidence interval, 0.71 to 0.81) to 0.97 (0.94 to 1.00). Throughout the first week, CRIB correlated with the risk of death (p < .001), prolonged treatment with oxygen (p < .001), and disability (p < .001 to p = .033). Improved condition, represented by a reduction in CRIB within the first week, was independently associated with lower risks of each adverse outcome, p < .05.

CONCLUSIONS

During the first week, CRIB was reliable, valid, and responsive. These properties support the use of CRIB in the stratification of infants by risk and illness severity in cohort studies, and they also indicate that CRIB may have the potential to be used in other ways in the future.

What do doctors record in the medical notes following discussion with the parents of sick premature infants?

In a retrospective review of medical notes we determined: (1) how often doctors record discussions with the parents of very low birth weight (VLBW) infants during the neonatal period; (2) what details of any discussion they actually record and; (3) if they are more likely to record discussion with the parents of sicker infants. A random sample (30%) of all VLBW infants admitted between 1989 and 1993 to a regional NICU was reviewed, n = 87. No discussion was documented in 47 cases, one of whom died, 24 had a single episode of discussion recorded and 16 had two or more episodes recorded. Specific discussion about prognosis was only recorded in the notes of 27 babies. Discussion was more likely to be documented in sicker infants as measured by CRIB (clinical risk index for babies) score, t = -3.9, P < 0.001.

CONCLUSION

A record of discussion between medical staff and parents is found in the medical notes of less than half of all VLBW infants. These findings may have practical, ethical and legal implications.

Randomised controlled trial of respiratory system compliance measurements in mechanically ventilated neonates

AIM

To determine whether outcomes of neonatal mechanical ventilation could be improved by regular pulmonary function testing.

METHODS

Two hundred and forty five neonates, without immediately life threatening congenital malformations, were mechanically ventilated in the newborn period. Infants were randomly allocated to conventional clinical management (control group) or conventional management supplemented by regular measurements of static respiratory system compliance, using the single breath technique, with standardised management advice based on the results.

RESULTS

Fifty five (45%) infants in each group experienced one or more adverse outcomes. The median (quartile) durations of ventilation and oxygen supplementation were 5 (2-12) and 6 (2-34) days for the control group, and 4 (2-9) and 6 (3-36) days for the experimental group (not significant). On post-hoc secondary analysis, control group survivors were ventilated for 1269 days with a median (quartile) of 5 (2-13) days, and experimental group survivors were ventilated for 775 days with a median (quartile) duration of 3 (2-8) days (p = 0.03).

CONCLUSIONS

Although primary analysis did not show any substantial benefit associated with regular measurement of static respiratory system compliance, this may reflect a type II error, and a moderate benefit has not been excluded. Larger studies are required to establish the value of on-line monitoring techniques now available with neonatal ventilators.

CRIB (clinical risk index for babies) in relation to nosocomial bacteraemia in very low birthweight or preterm infants

Positive blood cultures in very low birthweight or preterm infants usually reflect bacteraemia, septicaemia, or failure of asepsis during sampling and lead to increased costs and length of stay. Rates of nosocomial, or hospital acquired, bacteraemia may therefore be important indicators of neonatal unit performance, if comparisons are adjusted for differences in initial risk. In a preliminary study the risk of nosocomial bacteraemia was related to initial clinical risk and illness severity measured by the clinical risk index for babies (CRIB). Nosocomial bacteraemia was defined as clinically suspected infection with culture of bacteria in blood more than 48 hours after birth. One or more episodes of nosocomial bacteraemia were identified retrospectively in 36 of 143 (25%) infants in a regional neonatal unit between 1992 and 1994. Biologically plausible models were developed using regression analysis techniques. After correcting for period at risk, nosocomial bacteraemia was independently associated with gestation at birth and CRIB. Death was independently associated with CRIB, but not with nosocomial bacteraemia. CRIB may contribute, with other explanatory variables, to more comprehensive predictive models of death and nosocomial infection. These may facilitate future risk adjusted comparative studies between groups of neonatal units.

Phagocyte chemiluminescence in pre-term infants

Intact phagocyte function is a pre-requisite for successful defence against infection, but paradoxically, these cells may also play a major role in the pathogenesis of the infant respiratory distress syndrome. Phagocyte function is known to be deficient in pre-term infants, who are at risk of infection as a result, but these infants are also at risk of respiratory distress syndrome as a result of surfactant deficiency. Despite this, few longitudinal studies of phagocyte function have been performed in pre-term infants. We have used lucigenin-enhanced chemiluminescence to examine the respiratory burst of mixed samples containing polymorphonuclear leucocytes and monocytes of 100 pre-term infants at 48- to 72-h intervals during their admission to a neonatal care unit. Increased polymorphonuclear leucocyte chemiluminescence was associated with respiratory distress syndrome and the use of intermittent positive pressure ventilation. Multiple linear regression analysis revealed a slight, but significant depression of chemiluminescence in association with the use of gentamicin and penicillin when stronger influencing factors such as the presence of respiratory distress syndrome were taken into consideration. Measurement of phagocyte function by sensitive luminescence assays requires very little blood and may be useful in pre-term infants to follow the severity of respiratory distress syndrome. However, it is probable that other factors such as antioxidant capacity also have an important influence on the degree of tissue damage.

Life-threatening inadvertent positive end-expiratory pressure

Inadvertent positive end-expiratory pressure (PEEP) is a potential cause of lung overdistension and impaired gas exchange in ventilated infants. It can be extremely difficult to diagnose clinically and if unrecognized can be life-threatening. Measurement of lung function can lead to the recognition of inadvertent PEEP, allowing appropriate ventilator adjustment with immediate substantial improvement in clinical state. Lung function measurements can help to optimize ventilation and may improve clinical outcome.

Antibiotic effects on phagocyte chemiluminescence in vitro

Phagocytes are an essential defence against infection. Since drugs which affect their function may alter the outcome of infections, we have studied the effect of nine antibiotics on phagocyte function in vitro. The effects of antibiotics on the respiratory burst function of phagocytes from healthy adult donors were investigated using lucigenin-enhanced chemiluminescence in response to serum-opsonised zymosan. Aminoglycosides showed dose-dependent suppression of polymorphonuclear leucocyte chemiluminescence, except streptomycin which caused enhancement. Erythromycin caused profound suppression of chemiluminescence from both polymorphonuclear leucocytes and monocytes. Benzylpenicillin and the cephalosporins caused variable suppression of phagocyte chemiluminescence: cefotaxime increased monocyte chemiluminescence in some experiments. None of the drugs produced suppression at clinically relevant plasma concentrations, but erythromycin and some other drugs are preferentially concentrated in phagocytes to levels which suppress their oxidative metabolism in vitro. It is therefore possible that some antibiotics alter phagocyte function: ex vivo studies of phagocyte function in patients taking antibiotics would be valuable.

Reliability of clinical assessments of respiratory system compliance (Crs) made by junior doctors

OBJECTIVE

To assess the reliability of estimates of static respiratory system compliance (Crs) made by junior hospital doctors caring for ventilated newborn infants.

DESIGN

A prospective comparison of junior doctors' estimates of Crs to the Crs measured immediately afterwards.

SETTING

A regional neonatal intensive care nursery in Edinburgh, Scotland.

PATIENTS

46 ventilated newborn infants.

MEASUREMENTS AND RESULTS

Crs was estimated by three grades of junior doctor (Senior House Officer, Registrar and Research Fellow) using two different methods, (i) based on visual assessment of tidal volume in relation to inflation pressure (optical Crs) and (ii) directly using a visual analogue scale (analogue Crs). The Crs was then measured immediately afterwards using the single breath passive expiratory flow technique. The differences between the estimates and the measurements were calculated for each grade of observer and plotted against the corresponding measurements. The relationship between estimates and measurements was also expressed in terms of the coefficients of determination r2 calculated by least squares regression. With both methods of estimation observers tended to overestimate the Crs of infants with lower measured Crs and underestimate that of infants with higher measured Crs with many estimates differing from the measurements by more than 50%. Values of r2 ranged from 0.086 to 0.481 indicating a weak relationship between the estimates and the measurements.

CONCLUSIONS

Junior doctors' estimates of Crs were unreliable and did not represent a useful method of assessing respiratory function. The clinical use of compliance measurements merits wider evaluation.

Static respiratory compliance in the newborn. I: A clinical and prognostic index for mechanically ventilated infants

Accurate measures of the severity of respiratory disease are important, both clinically and epidemiologically. The apparent prognostic value of static respiratory system compliance (Crs) on the first day and mean appropriate fractional inspired oxygen (FIO2) in the first 12 hours of life were compared in 48 infants who received mechanical ventilation in a regional neonatal unit. Their median (range) gestation was 30 (25-41) weeks and they were representative of all 140 newborn infants born to residents of a geographically defined area who received mechanical ventilation over a 30 month period. Using the best cut off value (< or = 0.6 ml/cm H2O/m corrected for body length), static Crs predicted hospital death with 98% accuracy, 80% sensitivity, and 100% specificity. Using the best cut off value (> 0.60), mean FIO2 in the first 12 hours predicted hospital death with 81% accuracy, 80% sensitivity, and 81% specificity. Static Crs appeared to be a more accurate measure of respiratory function and disease severity than mean FIO2, perhaps because static Crs is less dependent on ventilator management than routine indices based on blood gases. Static Crs now merits wider evaluation, both as an aid to routine clinical management and as a prognostic index in comparative studies.

Static respiratory compliance in the newborn. II: Its potential for improving the selection of infants for early surfactant treatment

Static respiratory system compliance (Crs) and lecithin/sphingomyelin (L/S) ratios in tracheal aspirates were estimated in two independent groups of mechanically ventilated infants. Crs was measured rapidly at the cotside using a passive expiratory flow technique and L/S ratios were estimated in the laboratory by high performance liquid chromatography. In the reference group of 22 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 100% and a negative predictive value of 92%. In the validation group of 23 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 94% and a negative predictive value of 83%. Measurement of static Crs is a rapid, non-invasive technique which may usefully supplement current methods of selecting infants at high risk of respiratory distress syndrome.

Static respiratory compliance in the newborn. III: Early changes after exogenous surfactant treatment

Static respiratory system compliance (Crs) was measured by a single breath passive expiratory flow technique in 73 newborn infants treated with exogenous surfactant. The first 39 received Curosurf, a natural porcine surfactant. The other 34 received Exosurf Neonatal, a synthetic surfactant. All had a diagnosis of respiratory distress syndrome with an arterial/alveolar oxygen ratio < 0.22. Static Crs and arterial blood gases were measured shortly before, and at three and 12 hours after the first dose of surfactant. In 32 infants treated with Curosurf with initial static Crs < 1.8 ml/cm H2O/m body length, which is consistent with surfactant deficiency, static Crs improved by 18% at three hours and by 39% at 12 hours along with a median reduction in fractional inspired oxygen (FIO2) at three hours by 0.32. In 26 infants treated with Exosurf with initial Crs < 1.8 ml/cm H2O/m, Crs did not improve three and 12 hours after treatment and oxygenation improved less than after Curosurf, with a median reduction in FIO2 at three hours of 0.11. Fifteen of the 73 (21%) infants had initial static Crs of > or = 1.8 ml/cm H2O/m, not consistent with surfactant deficiency. Thirteen of these 15 infants showed a fall in static Crs after surfactant treatment, raising the question whether exogenous surfactant did them more harm than good. Initial static Crs and surfactant type both appear to determine the early response to the first dose of surfactant. Only a considerably larger, randomised study can show which surfactant is more effective in reducing adverse clinical outcome.

Artificial versus natural surfactant--can we base clinical practice on a firm scientific footing?

Now that surfactant is in widespread use, clinical trials are beginning to address the critical question of whether the choice of surfactant really matters in terms of major morbidity and mortality. The trials reported so far focus on the effects of artificial and natural surfactant on acute gas exchange and duration of oxygen or ventilation therapy. Although the number of infants recruited to comparative trials of different surfactants is increasing, we are still a long way from being able reliably to answer the question 'Which type of surfactant should we use and under what circumstances?' In understanding the uncertainty in this field it is pertinent to consider the interrelationships between three levels of research for any new therapy in clinical science. At the first level animal studies or case reports suggest potential clinical benefits. At the second, more focused physiological studies and trials address questions of mechanism. At the third, definitive randomised trials compare major adverse clinical outcomes in human patients. Only studies conducted at this third level can finally establish clinical practice on a firm scientific footing. In this review, a preliminary meta-analysis of 801 patients recruited in three trials of artificial (Exosurf) versus natural (Survanta) surfactant shows no clear advantage for either surfactant but does not rule out moderate differences in major adverse outcomes. To establish reliably whether such differences exist will require large multicentre clinical trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicentre randomised trial comparing high and low dose surfactant regimens for the treatment of respiratory distress syndrome (the Curosurf 4 trial)

A randomised trial was conducted in 82 centres using the porcine surfactant extract, Curosurf, to compare two regimens of multiple doses to treat infants with respiratory distress syndrome and arterial to alveolar oxygen tension ratio < 0.22. Infants were randomly allocated to a low dosage group (100 mg/kg initially, with two further doses at 12 and 24 hours to a maximum cumulative total of 300 mg/kg; n = 1069) or a high dosage group (200 mg/kg initially with up to four further doses of 100 mg/kg to a maximum cumulative total of 600 mg/kg; n = 1099). There was no difference between those allocated low and high dosage in the rates of death or oxygen dependency at 28 days (51.1% v 50.8%; difference -0.3%, 95% confidence interval (CI) -4.6% to 3.9%), death before discharge (25.0% v 23.5%; difference -1.5%, 95% CI -5.1% to 2.2%), and death or oxygen dependency at the expected date of delivery (32.2% v 31.0%; difference -1.2%, 95% CI -5.2% to 2.7%). For 14 predefined secondary measures of clinical outcome there were no significant differences between the groups but the comparison of duration of supplemental oxygen > 40% did attain significance; 48.4% of babies in the low dose group needed > 40% oxygen after three days compared with 42.6% of those in the high dose group. The total amount of surfactant administered in the low dose regimen (mean 242 mg phospholipid/kg) was probably enough to replace the entire pulmonary surfactant pool. Adopting the low dose regimen would lead to considerable cost savings, with no clinically significant loss in efficacy.

Is neonatal inspired gas humidity accurately controlled by humidifier temperature?

OBJECTIVE

To investigate: a) the relationship between humidifier temperature and inspired gas humidity and b) the effect of insulating the inspiratory tube on "rainout" (condensate).

DESIGN

Observational study.

SETTING

Regional neonatal unit in a university hospital.

PATIENTS

Forty-eight infants receiving assisted ventilation, of whom 31 infants were nursed in incubators and 17 under radiant heaters.

MEASUREMENTS AND MAIN RESULTS

Despite always maintaining humidifier temperature greater than 34.7 degrees C, inspired gas humidity decreased below the American National Standards Institution minimum of 30 mg H2O/L on 35 of 479 occasions. At a humidifier temperature of 36 degrees C, inspired gas humidity varied between 17 and 43 mg H2O/L. In incubators set at a temperature of 34.1 +/- 1.3 (SD) degrees C, inspired gas humidity was linearly related to humidifier temperature, but with wide scatter (p less than .001, r2 = .28). In cooler incubators set at 32.9 +/- 1.8 degrees C, inspired gas humidity varied inversely with humidifier temperature. This variation was attributed to condensate due to inspired gas cooling within the incubator. Insulation of the inspiratory tubing reduced condensate by only 15%.

CONCLUSIONS

Inspired gas humidity cannot be predicted reliably from humidifier temperature. Accurate control will require a new generation of humidifiers that measure inspired gas humidity.

Trisomy 21 in transient myeloproliferative disorder

Transient leukemia in phenotypically normal children is rare. A newborn child in whom fever and tachypnea developed at age 2 days had a white blood cell count of 20.1 x 10(9)/L and many abnormal blast cells. Chromosome analysis of spontaneously dividing cells from the blood showed these to have trisomy 21, and 80% of cells in the marrow were also trisomic. No trisomic cells were present in skin fibroblast cultures. At age 6 months, at which time the blood film appeared normal, trisomic cells were no longer present.

Low inspired gas temperature and respiratory complications in very low birth weight infants

We analyzed 3705 measurements of inspired gas temperature in the first 96 hours of life, with concurrent measurements of ventilator variables and arterial oxygen tension, to determine any relationship to respiratory sequelae in 149 infants assisted by artificial ventilation. All management was with one type of ventilator (model IV100B, Sechrist Industries Inc., Anaheim, Calif.) and one type of humidifier (model MR 500, Fisher and Paykel, Auckland, New Zealand), and infants were placed under radiant heaters. Outcome for infants weighing greater than or equal to 1500 gm at birth was no different at low (less than or equal to 36.5 degrees C) versus high (greater than 36.5 degrees C) values of mean inspired gas temperature during the first 96 hours. However, infants weighing less than 1500 gm at birth had less respiratory morbidity at the higher temperatures; there was a reduction in the incidence of pneumothorax from 43% at low to 13% at high temperatures (p = 0.006) and a reduction in the severity of chronic lung disease, measured as mean Fio2 at 29 days in survivors, from 37.2% at low to 27.5% at high temperatures (p = 0.001). Clinical evaluation of the humidifier, as it was used in this study, suggested that temperature settings less than 36.5 degrees C were associated with inspired gas humidity between 28 and 36 mg H2O/L. For any humidifier, there may be a critical threshold for inspired gas humidity below which the risk of respiratory complications in very low birth weight babies is increased. This hypothesis requires rigorous scrutiny by controlled trial. In future studies, direct measurements of inspired gas humidity are needed to make a precise estimate of the optimal level.

Evidence of inadequate humidification of inspired gas during artificial ventilation of newborn babies in the British Isles

Data on routine humidifier settings used in respiratory support for newborn babies were obtained from 242 neonatal units in the British Isles. For each of the most commonly used humidifiers inspired gas humidity was measured under routine clinical conditions with an electronic hygrometer. Most endotracheally intubated babies breathe inspired gas of well below physiological humidity (44 mg H2O/l) and many below the minimum recommended for adults by the British Standards Institution (33 mg H2O/l). Inadequate humidification could contribute to several complications of artificial ventilation in newborn babies by inhibiting mucociliary clearance.

Inadequate humidification of respiratory gases during mechanical ventilation of the newborn

Proximal airway humidity was measured during mechanical ventilation in 14 infants using an electronic hygrometer. Values below recommended minimum humidity of adult inspired gas were recorded on 251 of 396 occasions. Inadequate humidification, largely due to inadequate proximal airway temperature, is commoner than recognised in infants receiving mechanical ventilation.

Lack of association between barotrauma and air leak in hyaline membrane disease

A retrospective analysis of 632 infants with hyaline membrane disease admitted to this regional intensive care nursery between 1 July 1974 and 31 December 1982 showed that 387 (61%) received mechanical ventilation. The ventilator pressures at the time the first air leak was detected were available from the records of 120 of 154 (78%) of the infants who sustained pulmonary air leak. There was a significant downward trend in both peak and end expiratory pressure used during the study period. The downward trend in peak pressure persisted when inborn and outborn infants, boys and girls, and infants more than 27, and 23 to 27 weeks' gestation were examined separately. Despite these trends there was no reduction in the incidence of pulmonary air leak in any group. These data do not support the hypothesis, implicit in the term barotrauma, that a reduction in ventilator pressures decreases the risk of air leak.

Failure to thrive owing to inappropriate diet free of gluten and cows' milk

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Iatrogenic hyponatraemia of the newborn due to maternal fluid overload: a prospective study

Over five weeks 136 out of 246 deliveries were studied. Maternal plasma sodium concentrations were normal at admission. At delivery no significant difference was found between maternal and infant cord plasma sodium concentrations. Twenty-four of the 41 mothers who had received only oral fluids during labour had infants whose cord plasma sodium concentrations were normal. Of the 95 mothers who had been given intravenous fluids, however, only 14 infants with normal plasma sodium concentrations, 31 had a concentrations of 130 mmol (mEq)/1 or less and nine of these had a concentration of 125 mmol/1 or less. There was a highly significant inverse relation between cord plasma sodium concentration and rate of fluid administration, suggesting that hyponatraemia was due to intravenous treatment with predominantly sodium-free solutions. Endogenous antidiuretic activity probably increases during labour, and synthetic oxytocin in large doses has been shown to have an antidiuretic effect. The dose used in this study did not appear to have such an effect. Glucose solutions are often used as a vehicle for oxytocin; 83% of all fluid intake in this study was 5% or 10% glucose in water. Fluid balance in labour should be supervised closely, and oxytocin should be given in a more concentrated solution.