Randomized trial of normal saline versus 5% albumin for the treatment of neonatal hypotension

OBJECTIVES

This study was designed to assess the comparative efficacy of normal saline (NS) and 5% albumin (ALB) for treatment of hypotension in the acutely ill newborn.

STUDY DESIGN

Newborn infants who were < 24 hours old and were admitted to the Holden Neonatal Intensive Care Unit at the University of Michigan were randomized to receive one of the two solutions for volume expansion. Hypotension was defined as a sustained (> or =30 minutes) mean arterial pressure (MAP) of < 30 mmHg for infants weighing < or =2500 g, or a MAP of < 40 mmHg for those weighing > 2500 g. The short-term outcome measure was the resolution of hypotension defined as a MAP over the minimum limits set for birthweight sustained for > or =30 minutes.

RESULTS

In total 41 infants met criteria and were entered. Of these, 21 infants received ALB and 20 received NS. Successful treatment was seen in 17/21 (81%) of infants in the ALB group and 17/20 (85%) of infants in the NS group. There was no statistically significant difference in response to treatment (p=0.30). In addition, there was no statistically significant difference in the magnitude of change in MAP between the two (p=0.41).

CONCLUSIONS

NS was shown to be as effective as ALB for the correction of acute hypotension in the newborn infant. Given comparable efficacy of NS, along with its relatively low cost and availability, it should be considered the initial treatment of choice in this setting.

Invasive and noninvasive neonatal mechanical ventilation

Neonatal respiratory failure consists of several different disease entities, with different pathophysiologies. During the past 30 years technological advances have drastically altered both the diagnostic and therapeutic approaches to newborns requiring mechanical assistance. Treatments have become both patient- and disease-specific. The clinician has numerous choices among the noninvasive and invasive ventilatory treatments that are currently in use. This article reviews the pathophysiology of respiratory failure in the newborn and the available methods to treat it, including continuous positive airway pressure, conventional and high-frequency mechanical ventilation, extracorporeal membrane oxygenation, and styles of ventilation and monitoring.

Usefulness of the minute ventilation test in predicting successful extubation in newborn infants: a randomized controlled trial

OBJECTIVE

We performed a prospective, randomized clinical trial to compare the usefulness of the minute ventilation test (MVT) with clinical judgement in predicting readiness for extubation in preterm newborns with respiratory distress syndrome requiring surfactant therapy and mechanical ventilation.

STUDY DESIGN

A total of 42 preterm infants with respiratory distress syndrome were randomized when they reached preselected ventilator settings. The primary outcome measure was the time from study entry to extubation, provided the infant remained extubated for at least 24 hours.

RESULTS

Infants evaluated by the MVT were extubated in a significantly shorter period of time (mean of 8 hours) than those evaluated clinically (mean of 36 hours). The extubation failure rate was similar in the two groups.

CONCLUSION

The MVT is an easily performed objective measure that can be used to predict readiness for extubation in preterm infants. In this study, it significantly shortened the time for extubation and was not associated with a higher rate of reintubation.

Newer techniques of mechanical ventilation: an overview

The introduction of newer, state-of-the-art, microprocessor controlled ventilator systems provides clinicians with opportunities to apply a number of advanced ventilatory modalities which were not previously available for treating newborns. Some of these techniques will need further scientific evaluation in controlled trials, but this should not preclude their use in clinical settings, as their safety has already been proved by "standard setters" for use in neonates. There is a firm physiological rationale for their use, and individual centres have already acquired substantial experience in the application of these modalities. The trend towards increasing sophistication and greater versatility is likely to continue, and clinicians involved in the care of sick newborn infants must keep abreast of these developments.

Weaning newborns from mechanical ventilation

While there is a relative consensus as to whether mechanical ventilation should be initiated, the management of babies during recovery from respiratory failure remains largely subjective and is predominantly determined by institutional or individual practices or preferences. This can lead to babies either being left on the ventilator too long, or extubated too hastily, thus requiring repeated re-intubation. The current scientific literature fails to provide a uniform view of the most appropriate way to wean babies from mechanical ventilation. This might stem from a lack of understanding of the relative merits of the different techniques of discontinuing mechanical ventilation, given the availability of a variety of primary ventilatory modes which were not available to a neonatal population before, and limited research into the pathophysiological mechanisms responsible for an unsuccessful extubation. The purpose of this paper is to review the physiological, mechanical, and clinical principles of weaning, and to highlight areas still in need of investigation.

Mechanisms of ventilator-induced lung injury in premature infants

Mechanical ventilation in premature infants may injure the lungs or exacerbate the pre-existing condition that led to the need for mechanical ventilation. Ventilator-induced lung injury (VILI) may be associated with alveolar structural damage, pulmonary oedema, inflammation, and fibrosis. This injury is not uniform and is associated with surfactant dysfunction. Recovery from VILI includes clearance of pulmonary oedema and alveolar structural repair. Mechanisms of VILI include high airway pressure (barotrauma), large gas volumes (volutrauma), alveolar collapse and re-expansion (atelectotrauma), and increased inflammation (biotrauma). Injury to the lung may lead to other organ dysfunction. The premature lung is more susceptible to VILI, and lung injury may exacerbate the disturbance of lung development that occurs after birth. Therapies targeting specific processes in lung injury, and which complement the protective ventilator management strategies to avoid atelectotrauma and lung overdistension are an area of active research.

Relationship of neonatal endotracheal tube size and airway resistance

BACKGROUND

Infants receiving mechanical ventilation require narrow-lumen, small-diameter endotracheal tubes.

OBJECTIVE

Compare the resistances of endotracheal tubes used in the neonatal intensive care unit.

METHODS

Endotracheal tubes of internal diameter 2.5, 3.0, 3.5, and 4.0 mm were tested with a standard neonatal ventilator and a test lung. An endotracheal tube of each diameter was cut to 12 cm and connected to a flow transducer at one end and the test lung at the other. Serial measurements of resistance were made at various flows (6, 8, 10, and 12 L/min) and ventilator rates (30-90 breaths/min) encompassing the ranges of clinical practice. Analysis of variance was performed for each tube size, comparing resistance to flows and ventilator rates.

RESULTS

Resistance was significantly higher with the 2.5 mm tube than with the others. There was also a consistent trend, in all the tube sizes, towards higher resistance as flow was increased.

CONCLUSIONS

The higher resistance of the 2.5 mm tube may be detrimental to extremely low birthweight infants kept on mechanical support merely "to grow." The higher resistance may increase the work of breathing and thus increase caloric expenditure and impede growth.

A multicenter, randomized, controlled trial comparing Surfaxin (Lucinactant) lavage with standard care for treatment of meconium aspiration syndrome

OBJECTIVE

Infants with meconium aspiration syndrome (MAS) have marked surfactant dysfunction. Airways and alveoli of affected neonates contain meconium, inflammatory cells, inflammatory mediators, edema fluid, protein, and other debris. The objective of this study was to compare treatment with bronchoalveolar lavage using dilute Surfaxin with standard therapy in a population of newborn infants with MAS.

METHODS

Inclusion criteria were 1) gestational age > or =35 weeks, 2) enrollment within 72 hours of birth, 3) diagnosis of MAS, 4) need for mechanical ventilation, and 5) an oxygenation index > or =8 and < or =25. Subjects were randomized to either lavage with Surfaxin or standard care (2:1 proportion). In lavaged infants, a volume of 8 mL/kg dilute Surfaxin (2.5 mg/mL) was instilled into each lung over approximately 20 seconds followed by suctioning after 5 ventilator breaths. The procedure was repeated twice. The third and final lavage was with a more concentrated solution (10 mg/mL) of Surfaxin.

RESULTS

Twenty-two infants were enrolled (15 Surfaxin and 7 control). Demographic characteristics were similar. There were trends (not significant) for Surfaxin-lavaged infants to be weaned from mechanical ventilation earlier (mean of 6.3 vs 9.9 days, respectively), as well as to have a more rapid decline in their oxygenation indexes compared with control infants, the latter difference persisting for the 96-hour-long study period. The therapy was safe and generally well tolerated by the infants.

CONCLUSIONS

Dilute Surfaxin lavage seems to be a safe and potentially effective therapy in the treatment of MAS. Data from this investigation support future prospective, controlled clinical trials of bronchoalveolar lavage with Surfaxin in neonates with MAS.

Volume-controlled ventilation. Variations on a theme

Development of sophisticated transducers and microprocessor-based ventilators now enables the performance of volume-controlled ventilation of newborn infants. Volume-controlled modes include standard intermittent or synchronized intermittent mandatory ventilation; assist-control ventilation; and hybrid modes, such as pressure-support ventilation, pressure-regulated volume-control ventilation, volume-assured pressure support, and volume guarantee. This article describes the concepts and clinical applications of these ventilatory modes.

Newer modes of mechanical ventilation for the neonate

For decades, the overwhelming majority of infants requiring mechanical ventilation for respiratory failure were treated with standard time-cycled, pressure-limited intermittent mandatory ventilation. Technologic advances in the 1990s brought forth sophisticated transducers and microprocessor-based mechanical ventilators that enabled implementation of many newer modes of mechanical ventilation. Some of these are volume-targeted rather than pressure-targeted, and many allow an element of patient control of the ventilator, including initiation and termination of inspiration and control of flow. Some modes are even hybrids, combining the best features of both pressure-targeted and volume-targeted modes. This article reviews the principles and salient clinical features of the newer ventilatory modes for newborns with respiratory failure.

Congenital choanal atresia in siblings

Choanal atresia is a relatively rare anomaly of the upper airway, which can result in significant respiratory distress in the newborn. It is often associated with other anomalies and has only rarely been reported in siblings. We report its isolated occurrence in two siblings.

Spontaneous minute ventilation predicts readiness for extubation in mechanically ventilated preterm infants

OBJECTIVE

We designed an observational study to test the hypothesis that a comparison of two methods of minute ventilation, spontaneously generated with mechanically generated, would be a useful predictor of readiness for extubation in preterm infants, weighing <2000 gm, who require mechanical ventilation for >24 hours.

STUDY DESIGN

This observational study of 35 infants weighing < or = 2000 gm evaluated the comparison of spontaneously generated minute ventilation with mechanically generated minute ventilation to successfully predict readiness for extubation. After reaching entry criteria, infants were extubated if their spontaneously generated minute ventilation (while receiving endotracheal CPAP) was > or = 50% of the mechanically generated minute ventilation during assist/control ventilation.

RESULTS

Of the 35 infants who had a successful trial and were extubated, 30 (86%) remained extubated for at least 24 hours. Of the five infants who failed extubation, four developed apnea and one developed stridor. Thus, a spontaneous minute ventilation of > or = 50% of mechanically generated minute ventilation predicted readiness for extubation in 86% of the patients in this observation.

CONCLUSION

A spontaneously generated minute ventilation that is > or = 50% of the mechanically generated minute ventilation is an objective predictor of the readiness for extubation in low birth weight infants who have been weaned to modest ventilatory support.

Controversies in patient-triggered ventilation

Patient-triggered ventilation is a relatively recent development in neonatal mechanical ventilation. Advances in microprocessor-based technology, transducers, and monitoring have enabled patient-driven ventilator control and synchronization of mechanical ventilation with patient effort. The novelty of the newer ventilatory techniques has generated several controversies that remain to be resolved. Among these are signal detection and transduction, the optimal ventilatory modes, and weaning during patient-triggered ventilation.

Randomised trial of volume controlled versus time cycled, pressure limited ventilation in preterm infants with respiratory distress syndrome

Fifty preterm infants weighing 1200 g or more with clinical and radiographic evidence of respiratory distress syndrome, requiring both mechanical ventilation and exogenous surfactant replacement, were randomly allocated to receive either volume controlled ventilation or time cycled, pressure limited ventilation. Tidal volume delivery in each group was deliberately controlled at 5-8 ml/kg so that the only difference between the two groups was the ventilatory modality, the manner in which tidal volume was delivered. The rest of the ventilatory management and clinical care was done according to protocol. The two modes of ventilation were compared by determining the time required to achieve pre-determined success criteria, based on either the alveolar-arterial oxygen gradient or the mean airway pressure as a standard against which the speed of weaning could be objectively assessed. Infants randomised to volume controlled ventilation met success criteria sooner and had a shorter duration of mechanical ventilation. These babies also had a significantly lower incidence of intraventricular haemorrhages and abnormal periventricular echodensities on ultrasound scans. Volume controlled ventilation seems to be both safe and effective in this group of patients.

Prospective evaluation of two dosing equations for theophylline in premature infants

STUDY OBJECTIVES

To evaluate prospectively the ability of two equations that we previously derived to predict maintenance theophylline dosages that provide a serum theophylline concentration (STC) of 8 micrograms/ml, the midtherapeutic range for treating apnea of prematurity; and to determine the number of further dosage adjustments and STC determinations required to achieve the target concentration in infants in whom it was not achieved initially.

DESIGN

Prospective study.

SETTING

A 37-bed neonatal intensive care unit.

PATIENTS

Fifty-four infants 27-34 weeks' gestational age requiring intravenous hydrous aminophylline.

INTERVENTIONS

Patients received a loading dose of 6 mg/kg intravenous aminophylline, followed by a maintenance dosage calculated using one of the two derived equations. The basis for equation selection was the gestational age of the patient.

MEASUREMENTS AND MAIN RESULTS

Patients were stratified into two age groups: 27-30 weeks' gestational age (34 infants) and 31-34 weeks' gestational age (20 infants). The overall success rate for both equations in achieving the target concentration was 74%. When infants were stratified by gestational age, those dosed by Equation 1 had a 76% success rate and those dosed by Equation 2 had a 65% success rate. Overall, 14 of 54 infants received an average of 1.2 dosage adjustments. This represents more than a 50% reduction in the number of adjustments made before introduction of these equations.

CONCLUSIONS

The ability of our previously derived equations to produce an STC within the midtherapeutic range for treating apnea of prematurity was demonstrated in the majority of patients studied (74%). Further, the number of subsequent dosage adjustments required to attain the target STC in infants who had failed to achieve this STC initially was significantly less than using older, more traditional regimens.

Accuracy and reliability of dosing equations to individualize theophylline treatment of apnea of prematurity

Apnea of prematurity is associated with high morbidity and mortality. Treatment generally includes supplemental oxygen and theophylline or caffeine. The half-life of theophylline is prolonged in newborns because of their immature cytochrome P-450 system, and there is considerable variation in the drug's metabolism in infants. We compared the accuracy, precision, and reliability of two equations that use postnatal age (PNA) to determine a maintenance dosage of theophylline with a standard maintenance dosage (SMD) that produced a steady-state serum theophylline concentration (STC) of 8 micrograms/ml for apnea of prematurity in 46 infants less than 34 weeks' gestational age (GA) and less than 36 weeks' postconceptional age (PCA). The two equations were mg/kg/day = [(0.2 x PNA in wks) + 5], and mg/kg/day = [(0.3 x PNA in wks) + 8]. Their reliability to predict the SMD was determined by correlation analysis. The precision and accuracy with which they predicted SMD were determined and analyzed by chi 2. The SMD did not correlate with the maintenance dosages calculated by equations 1 and 2 (r = 0.296 and 0.296, p > 0.05 in both cases). Multiple linear regression of SMD versus GA, PNA, and PCA was not significant (r = 0.33, p = 0.32). After stratifying data based on GA and performing correlation analysis of SMD versus PNA, a weak but significant correlation (r = 0.42, p = 0.517) was found for infants with GA between 31 and 34 weeks. Poor correlation was found between SMD versus PNA for infants 27-30 weeks' GA. Two new equations of the best fit line were generated using the same data.(ABSTRACT TRUNCATED AT 250 WORDS)