Neonatal apnea, bradycardia, or desaturation: does it matter?

A novel sleep oximetry scoring tool for pediatric laryngomalacia

OBJECTIVE

Despite being a more accessible and less resource intensive modality than polysomnography, the utility of sleep oximetry (SO) in pediatric laryngomalacia (LM) is not well understood or validated. We aimed to retrospectively evaluate the utility of overnight home based SO in children with LM by developing and internally validating the Modified Laryngomalacia Oximetry Score (MLOS) scoring system to triage severity and guide clinical decision making.

METHODS

We evaluated pediatric patients with a diagnosis of LM at our tertiary referral centre. Data from initial and post-treatment SO including mean oxygen saturation (spO2) nadir and mean oxygen desaturation index (ODI) were aggregated. The MLOS ranging from I-VI (inconclusive to severe) was created by two otolaryngologists to incorporate bradycardia associated desaturation events during SO. Corresponding McGill Oximetry Score (MOS) was also determined.

RESULTS

172 patients were included in final analysis. The average age was 9.2 ± 14.3 months. 98 (57%) of patients were identified as Thompson severity score 1, and 87 (50.6%) of patients underwent supraglottoplasty. The surgical cohort had a significantly higher MLOS and MOS scores of 4 and 2 respectively, and higher mean ODI and spO2 nadir metrics. When evaluating post-supraglottoplasty SO tracings, all parameters improved significantly, including median MLOS score from 4 to 1. Only the mean ODI improved in the non-surgical cohort. Patients with Thompson severity score 2/3 had significantly higher MLOS.

CONCLUSION

We present a simple scoring system based on overnight SO, the MLOS, to help triage severity of pediatric LM and guide decision-making. MLOS is associated with worse clinical severity and a need for surgery, and shows significant improvement after surgery.

Impact of inflammation on developing respiratory control networks: rhythm generation, chemoreception and plasticity

The respiratory control network in the central nervous system undergoes critical developmental events early in life to ensure adequate breathing at birth. There are at least three "critical windows" in development of respiratory control networks: 1) in utero, 2) newborn (postnatal day 0-4 in rodents), and 3) neonatal (P10-13 in rodents, 2-4 months in humans). During these critical windows, developmental processes required for normal maturation of the respiratory control network occur, thereby increasing vulnerability of the network to insults, such as inflammation. Early life inflammation (induced by LPS, chronic intermittent hypoxia, sustained hypoxia, or neonatal maternal separation) acutely impairs respiratory rhythm generation, chemoreception and increases neonatal risk of mortality. These early life impairments are also greater in young males, suggesting sex-specific impairments in respiratory control. Further, neonatal inflammation has a lasting impact on respiratory control by impairing adult respiratory plasticity. This review focuses on how inflammation alters respiratory rhythm generation, chemoreception and plasticity during each of the three critical windows. We also highlight the need for additional mechanistic studies and increased investigation into how glia (such as microglia and astrocytes) play a role in impaired respiratory control after inflammation. Understanding how inflammation during critical windows of development disrupt respiratory control networks is essential for developing better treatments for vulnerable neonates and preventing adult ventilatory control disorders.

Amplitude-integrated electroencephalography shows that doxapram influences the brain activity of preterm infants

AIM

The aim of this study was to measure the brain activity of preterm infants treated with caffeine citrate and doxapram for preterm apnoea, using amplitude-integrated electroencephalography (aEEG), to identify any adverse effects on cerebral function.

METHODS

We analysed the aEEG tracings of 13 preterm infants <30 weeks of gestation before, during and after doxapram treatment, with regard to background activity (percentages of continuous and discontinuous patterns), occurrence of sleep-wake cycling and appearance of electrographic seizure activity. They were also compared with 61 controls without doxapram treatment.

RESULTS

During doxapram treatment, aEEG tracings showed an increase in continuous background activity (19 ± 30% before treatment, 38 ± 35% during treatment) and a decrease in discontinuous patterns. In addition, they showed more frequent electrographic seizure activity (0% before treatment, 15 ± 37% during treatment) and less frequent sleep-wake cycling (92 ± 27% before treatment, 85 ± 37% during treatment) could be observed. These results were confirmed when compared to the control group.

CONCLUSION

Doxapram treatment influences aEEG in preterm infants, showing higher percentages of continuous activity as well as more electrographic seizure activity and less sleep-wake cycling. It should, therefore, be used with caution in very preterm infants.

Low oxygen saturation target range is associated with increased incidence of intermittent hypoxemia

OBJECTIVE

To test the hypothesis that preterm infants randomized to a low vs high O(2) saturation target range have a higher incidence of intermittent hypoxemia.

STUDY DESIGN

A subcohort of 115 preterm infants with high resolution pulse oximetry enrolled in the Surfactant, Positive Pressure, and Oxygenation Randomized Trial were randomized to low (85%-89%) or high (91%-95%) O(2) saturation target ranges. Oxygen saturation was monitored until 36 weeks postmenstrual age or until the infant was breathing room air without respiratory support for ≥72 hours.

RESULTS

The low target O(2) saturation group had a higher rate of intermittent hypoxemia (≤80% for ≥10 seconds and ≤3 minutes) prior to 12 days and beyond 57 days of life (P < .05). The duration shortened (P < .0001) and the severity increased (P < .0001) with increasing postnatal age with no differences between target saturation groups. The higher rate of intermittent hypoxemia events in the low target group was associated with a time interval between events of <1 minute.

CONCLUSION

A low O(2) saturation target was associated with an increased rate of intermittent hypoxemia events that was dependent on postnatal age. The duration and severity of events was comparable between target groups. Further investigation is needed to assess the role of intermittent hypoxemia and their timing on neonatal morbidity.

Methylxanthine treatment for apnoea in preterm infants

BACKGROUND

Recurrent apnoea is common in preterm infants, particularly at very early gestational ages. These episodes of ineffective breathing can lead to hypoxaemia and bradycardia that may be severe enough to require the use of positive pressure ventilation. Methylxanthines (such as caffeine, theophylline or aminophylline) have been used to stimulate breathing and reduce apnoea and its consequences.

OBJECTIVES

To determine the effects of methylxanthine treatment on the incidence of apnoea and the use of intermittent positive pressure ventilation (IPPV) and other clinically important outcomes in preterm infants with recurrent apnoea.

SEARCH STRATEGY

Searches were made of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2010), the Oxford Database of Perinatal Trials, MEDLINE (1966 to June 2010), EMBASE (1982 to June 2010), previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching mainly in the English language.

SELECTION CRITERIA

All trials utilizing random or quasi-random patient allocation in which methylxanthine (theophylline, caffeine or aminophylline) as treatment for apnoea was compared with placebo or no treatment for apnoea in preterm infants were included.

DATA COLLECTION AND ANALYSIS

Methodological quality was assessed independently by the review authors. Data were extracted independently by the review authors. Analysis was done in accordance with the recommendations of the Cochrane Neonatal Review Group.

MAIN RESULTS

Six trials reported on the effect of methylxanthine in the treatment of apnoea (three trials of theophylline and three trials of caffeine). Five trials that enrolled a total of 192 preterm infants with apnoea evaluated short term outcomes; in these studies, methylxanthine therapy led to a reduction in apnoea and use of IPPV in the first two to seven days. The post-hoc analysis of the large CAP Trial comparing caffeine to control in a subgroup of infants being treated for apnoea reported significantly reduced rates of PDA ligation; postmenstrual age at last oxygen treatment, last endotracheal tube use, last positive pressure ventilation; and reduced chronic lung disease at 36 weeks.

AUTHORS' CONCLUSIONS

Methylxanthine is effective in reducing the number of apnoeic attacks and the use of mechanical ventilation in the two to seven days after starting treatment. Caffeine is also associated with better longer term outcomes. In view of its lower toxicity, caffeine would be the preferred drug for the treatment of apnoea.

Car seat safety for high-risk infants

Most neonates discharged from the hospital are able to go home in a standard car safety seat. Some infants, though, require special devices to ensure their safe travel. NICU nurses must have the knowledge and skills to comfortably and competently give vital information to parents preparing to take their infant home. This article is intended to increase awareness among NICU nurses of the potential dangers babies face when placed in a car seat. It provides a basic overview of car seat safety for infants being discharged home from an NICU and includes references for those who seek further information on this topic.

Asystole and Severe Bradycardia in Preterm Infants

Transient episodes of apnea and bradycardia are common in preterm infants. Pronounced asystole or sinus arrest, however, is relatively rare and the clinical significance of such events is unknown.

OBJECTIVE

The purpose of our study was to: (1) evaluate the prevalence of severe bradycardic and asystolic events in infants studied with polygraphic cardiorespiratory monitoring, (2) characterize these events, and (3) correlate the events with other clinical findings.

METHODS

A total of 583 studies were performed in 454 preterm infants at a post-conceptional age 37.4 +/- 2.5 (range 34-42 weeks). Asystolic pauses were defined as no QRS complex for >or=3 s consistent with a heart rate <20 beats per minute (bpm). Severe bradycardia was defined as no QRS for >or=2 s consistent with a heart rate of 21-30 bpm.

RESULTS

Eight infants (29.5 +/- 3.9 weeks' gestational age, birth weight 1,283 +/- 445 g) met the criteria of having had at least 1 asystolic event (heart rate <or=20 bpm). These infants had a total of 32 episodes of bradycardia <or=30 bpm, of which 22 episodes were classified as asystole. During the asystolic episodes, the P-R interval remained unchanged in 21 of 22 episodes and prolonged in 1. One patient had non-sustained ventricular tachycardia before resumption of normal sinus rhythm. All asystolic events were associated with apnea (mean duration of 17.7 +/- 9.4 s) and O(2) saturations fell by 10 +/- 6%. A pH probe study was available in 9 of 22 asystolic events and 6 of 10 severe bradycardic events. Gastroesophageal reflux was temporally related to only one asystolic and two bradycardic events. Clinical follow-up of these infants at a mean age of 14 months (range 1-46) reveals no symptomatic sequelae; although 1 infant died from multisystem failure associated with multiple congenital anomalies.

CONCLUSIONS

Asystolic pauses occur in 1.8% of a selected population of preterm infants who have been experiencing cardiorespiratory events, are related to respiratory pauses, and appear to have a benign long-term outcome, although future study should incorporate long-term neurodevelopmental outcome.

Laryngeal oedema in neonatal apnoea and bradycardia syndrome (a pilot study)

PURPOSE

Some preterm infants in general good health continue to present recurrent apnoeas, bradycardias and desaturations (ABD) despite usual treatments. These events may lead to transitory brain hypoxia and to further neurological injury. The purpose of this study has been to evaluate the role of laryngeal oedema in this symptomatology and to assess corticoid treatment.

METHOD

Twelve preterm babies born at a median age of 28.5 weeks (range: 26-35 weeks) already showed signs of ABD at a median age of life of 28.5 days (range: 9-80 days). Fiberoptic laryngeal endoscopy was performed on these babies at a median postconceptional age of 34 weeks (range: 31-38 weeks) to detect a possible involvement of the larynx in their ABD.

RESULTS

Each patient presented a severe laryngeal oedema compatible with potential obstructive breathing. Half of the cohort (n=6) received inhaled corticosteroids initiated with a short oral dexamethasone treatment for 3 to 5 days (group 1). All the babies improved. The other half (n=6) received only an inhaled topic corticosteroid treatment (group 2). Four of the six babies improved and two needed oral dexamethasone. Laryngoscopic endoscopy was carried out after 1 week of treatment. The picture corresponded with clinical improvement. Recurrence of ABD occurred in 3/12 (25%) of the babies after stopping dexamethasone. No immediate side effects of the procedure or the treatment were observed.

CONCLUSION

Laryngeal oedema may be a cause of ABD in preterm newborns. It may arise from oesophageal reflux and/or presence of the feeding tube. It can be diagnosed by atraumatic fiberoptic fibroscopy and successfully treated with corticosteroids.

Olfactory stimulation prevents apnea in premature newborns

OBJECTIVE

Methylxanthines and doxapram are currently used to treat apnea of prematurity but are not fully effective and often present undesirable side effects. The present study examines whether exposure to an odor known to modulate the infant's respiratory rate could reduce the frequency of apneic spells.

METHOD

Fourteen preterm newborns born at 24 to 28 gestational weeks presenting recurrent apnea despite caffeine and doxapram therapy were exposed to a pleasant odor diffused during 24 hours in the incubator. Efficiency of the olfactory treatment was judged by comparing frequency and severity of apneas occurring during the day of odorization with that observed the day before (baseline) and the day after (posttreatment control). Apnea was defined as any complete cessation of breathing movements for >20 seconds, or less if associated with hypoxia or bradycardia.

RESULTS

Concerning all types of apneas, a diminution of 36% was observed and seen in 12 of 14 infants. Apneas without bradycardia were reduced (44%) during the day with odorization, and this diminution affected all the infants. The frequency of apnea with moderate bradycardia (heart rate between 70 and 90 beats per minute) was maintained while the frequency of apnea associated with severe bradycardia (heart rate <70 beats per minute) decreased strongly (45%) and affected all the infants. No side effects were observed.

CONCLUSION

The introduction of a pleasant odor in the incubator is of therapeutic value in the treatment of apneas unresponsive to caffeine and doxapram.

Cardiorespiratory events detected by home memory monitoring and one-year neurodevelopmental outcome

OBJECTIVE

To determine if infants with cardiorespiratory events detected by home memory monitoring during early infancy have decreased neurodevelopmental performance.

STUDY DESIGN

Infants (n = 256) enrolled in the Collaborative Home Infant Monitoring Evaluation also completed the Bayley Scales of Infant Development II at 92 weeks' postconceptional age. Infants were classified as having 0, 1 to 4, or 5+ cardiorespiratory events. Events were defined as apnea >or=20 seconds or heart rate <60 to 80 bpm or <50 to 60 bpm, for >or=5 to 15 seconds, depending on age.

RESULTS

For term infants, having 0, 1 to 4, and 5+ cardiorespiratory events was associated with unadjusted mean Mental Developmental Index (MDI) values (+/-SD) of 103.6 (10.6), 104.2 (10.7), and 97.7 (10.9), respectively, and mean Psychomotor Developmental Index (PDI) values of 109.5 (16.6), 105.8 (16.5), and 100.2 (17.4). For preterm infants, having 0, 1 to 4, and 5+ cardiorespiratory events was associated with unadjusted mean MDI values of 100.4 (10.3), 96.8 (11.5), and 95.8 (10.6), respectively, and mean PDI values of 91.7 (19.2), 93.8 (15.5), and 94.4 (17.7). The adjusted difference in mean MDI scores with 5+ events compared with 0 events was 5.6 points lower in term infants ( P = .03) and 4.9 points lower in preterm infants ( P = .04).

CONCLUSIONS

Having 5+ conventional events is associated with lower adjusted mean differences in MDI in term and preterm infants.

Clinical correlates, natural history and outcome of neonatal apnoea

Apnoea is common in the newborn period and especially in preterm newborns. Bradycardia and desaturation of oxyhaemoglobin typically occur with apnoea. These abnormalities reflect an immature cardiorespiratory system and resolution of this immaturity can be expected within a predictable time frame. Infants who have apnoea in the newborn period are thought not to be at higher risk for sudden infant death syndrome (SIDS). Whether apnoea episodes are associated with a higher incidence of long-term handicap for these infants is not yet clear.

The mismatch between evidence and practice. Common therapies in search of evidence

Many therapies in neonatology persist without supportive evidence: some common therapies may actually be harmful. Evidence-based medicine is the "conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients". The best available evidence, however, is not always sound or valid evidence. Sometimes, when faced with a collection of reports that do not constitute good evidence, attempts to choose the best evidence become pointless; in this case, a statement of no good evidence is preferable. There is a continuing problem with the place of usual practice in the hierarchy of evidence; usual practice generates experience with a particular practice but no reliable information regarding how the practice compares with alternative strategies. Although clinical and institutional inertia combined with a litigious practice environment tend to uphold current practice, the field of neonatology is ripe with examples of established therapies that were subsequently shown to be harmful. It is important to focus on important long-term outcomes and as much on the possibility of harm as on the chance of benefit, especially for new therapies, before they become routine practice. In the face of inadequate evidence, it is particularly important to avoid the temptation to institute treatment guidelines that inhibit further research. Patients are better served by guidelines that recommend only strategies that are supported by strong evidence and recommend further research when the evidence is inadequate.

Episodic neonatal hypoxia evokes executive dysfunction and regionally specific alterations in markers of dopamine signaling

Perinatal ischemic-anoxic and prolonged anoxic insults lead to impaired dopaminergic signaling and are hypothesized to contribute, at least in part, to the pathogenesis of disorders of minimal brain dysfunction such as attention-deficit hyperactivity disorder. We hypothesized that subtle intermittent hypoxic insults, occurring during a period of critical brain development, are also pathogenic to dopaminergic signaling, thereby contributing to behavioral and executive dysfunction. Between postnatal days 7 and 11, rat pups were exposed to either 20-s bursts of isocapnic hypoxic gas, compressed air, or were left undisturbed with the dam. On postnatal days 23 pups were instrumented with electroencephalographic/electromyographic electrodes and sleep-wake architecture was characterized. Locomotor activity was assessed between postnatal days 35 and 38, learning, and working memory evaluated between postnatal days 53 and 64. Rats were killed on postnatal day 80 and tyrosine hydroxylase, vesicular monoamine transporter, dopamine transporter, and dopamine D1 receptors were quantified in the prefrontal cortex, primary sensorimotor cortex, and precommissural striatum by Western blot analyses. Post-hypoxic pups spent less time awake and more time in rapid-eye-movement sleep during the lights-on phase of the circadian cycle, were hyperlocomotive, and expressed impaired working memory. Striatal expression of vesicular monoamine transporter and D1 receptor proteins were increased in post-hypoxic rats, consistent with depressed dopaminergic signaling. These observations lead to the intriguing hypothesis that intermittent hypoxia occurring during a period of critical brain development evokes behavioral and neurochemical alterations that are long lasting, and consistent with disorders of minimal brain dysfunction.

Effects of theophylline on the pattern of spontaneous breathing in preterm infants less than 1000 g of birth weight

Proportional assist ventilation (PAV) amplifies the ventilatory effect of the spontaneous respiratory effort and therefore allows analysis of drug-induced changes in the spontaneous breathing pattern of subjects who depend on mechanical ventilatory assistance. We hypothesized that theophylline will reduce the number and duration of respiratory pauses and apneic events in infants less than 1000 g of birth weight on PAV. Twelve infants were studied: median birth weight was 773 g; gestational age 26.0 weeks and postnatal age 9 days. Measurements were obtained over a 2-h period before and after 5 mg/kg of intravenous theophylline. A respiratory pause was defined as cessation of breathing for at least the duration of three preceeding breaths. The total number of respiratory pauses and the number of apneas followed by either cardiac slowing (decrease in heart rate more than 10%) or bradycardia decreased significantly. Minute ventilation increased due to a rise in tidal volume from 5.6+/-1.3 to 6.1+/-1.2 ml/kg (p=0.004). The duration of respiratory pauses, the respiratory rate, and the number of apneas followed by desaturation did not change significantly. We conclude that theophylline stimulates spontaneous breathing in infants less than 1000 g, reduces the number of apneas, and increases minute volume by increasing the tidal volumes.

[Nasal continuous positive airway pressure in preterm infants: comparison of two low-resistance models]

OBJECTIVE

To compare the safety and efficacy of two low expiratory resistance models of nasal continuous positive airway pressure (n-CPAP) in preterm infants.

MATERIAL AND METHODS

A 1-year prospective trial was performed in the Neonatal Intensive Care Unit of La Fe Hospital to compare the Infant Flow (IF) and Medijet (MJ) devices. All preterm infants requiring n-CPAP for respiratory distress at birth (group I), infants weighting less than 1500 g requiring postextubation (group II) and those with apnea-bradycardia syndrome (ABS) (group III) were included. The patients were randomly assigned to IF or MJ.

RESULTS

A total of 125 patients received 226 treatments (IF: n 5 126: MJ: n 5 110). The mean gestational age was 29.4 weeks and the mean birth weight was 1340 g.Efficacy. In group I (n 5 73) no difference were found between systems and 6 hours' after initiation of n-CPAP decreases in FiO2, CO2 and respiratory effort were similar. The need for intubation was also similar (IF: 34.6 %; MJ: 24.1 %). In group II (n 5 73) the need for reintubation at 48 hours was similar with both treatments (IF:19 %; MJ: 8 %). In group III (n 5 80) resolution of ABS was similar after 24 hours of n-CPAP (IF: 46 %; MJ: 58 %). The need for intubation was also similar (IF: 26 %; MJ: 10 %).Complications. Air leaks occurred in six preterm infants (IF: 4; MJ: 2). Severe abdominal distension occurred in 5 % with both systems. Five infants had significant nasal lesions (IF: 1; MJ: 4).

CONCLUSIONS

The efficacy and safety of both systems was similar in the variables studied and no significant differences were found.

Relation of sleep state to hypoxemic episodes in ventilated extremely-low-birth-weight infants

OBJECTIVE

To determine whether hypoxemic episodes in ventilated extremely-low-birth-weight infants correlate with specific behavioral states.

STUDY DESIGN

Three-hour video-electroencephalography-polysomnography was performed on 13 ventilated extremely-low-birth-weight infants with mean postconceptional age of 28.3 weeks. The electroencephalogram was scored for discontinuity. Rapid eye movements, body, head, and limb movements were scored from synchronized video. Sleep states were defined from electroencephalography, rapid eye movements, and movement criteria. Nonparametric statistics were used to test for differences in the proportion of time hypoxemic (oxygen saturation </=85%) between behavioral states.

RESULTS

The proportions of time hypoxemic were 0.6% during quiet sleep, 4.4% during active sleep, 10.7% during indeterminate sleep, and 16.7% during arousal. There was a significant overall difference between the states (P =.004) and a significant difference between active sleep and indeterminate sleep in a pairwise comparison (P =.001).

CONCLUSIONS

Higher proportions of hypoxemia were found during indeterminate sleep and arousal compared with active sleep and quiet sleep. We speculate that motor activity during sleep disruption could prevent effective mechanical delivery of ventilator breaths and contribute to episodes of hypoxemia. Our results suggest that strategies promoting uninterrupted sleep cycling analogous to the intrauterine state could improve ventilatory stability.

Apnea at discharge and gastro-esophageal reflux in the preterm infant

OBJECTIVE

To determine the relationship between respiratory patterns and acid gastro-esophageal reflux (g-e reflux) prior to discharge of the formerly preterm infant.

STUDY DESIGN

Forty-five infants of <32 weeks' gestation were studied at an average postmenstrual age of 37.2 weeks (SD 3.5). Following informed parental consent, a 12-hour multichannel recording including esophageal pH was obtained. Apneas of greater than 10 seconds were recorded, as well as the occurrence of bradycardia or desaturation.

RESULTS

Acid g-e reflux (pH <4.0) occurred at least once in all of the infants; prevalence was between <1% and 41% of the 12-hour record (median 4.6%, interquartile range 0.5% to 9%). The number of reflux episodes ranged from 1 to 143 (median 23). The number of apneas (>10 seconds duration) ranged from 0 to 71, median 6. There was no correlation between apnea frequency or severity and reflux frequency or duration. There was no difference in apnea frequencies between the 5 minutes after the start of a reflux episode and the 5 minutes prior to each episode.

CONCLUSION

Acid g-e reflux in the formerly preterm infant at discharge is frequent and may be prolonged; there is no association between reflux and apnea.

Cardiorespiratory events in preterm infants referred for apnea monitoring studies

BACKGROUND

Episodes of apnea, desaturation, and bradycardia are common in preterm infants. Such infants who have persistent cardiorespiratory events detected by clinical bedside monitoring often are referred for overnight apnea monitoring studies.

OBJECTIVE

To characterize apnea, bradycardia, and desaturation events in infants referred for an overnight apnea monitoring study and compare them with corresponding events in control infants of similar age and weight with no bedside monitor alarms.

METHODS

Twelve-hour bedside apnea monitoring studies were performed on 68 preterm infants before hospital discharge. This population included 35 infants who were referred by their attending physicians because of persistent bedside monitor alarms (referral group) and 33 infants who had no documented cardiorespiratory events for at least 2 days before the study (control group). Each study monitored respiration via respiratory inductance plethysmography, oxygen saturation (Sao2), and heart rate. Events were defined as meeting 1 of the following criteria: apnea > or =20 seconds, bradycardia < or =80 beats per minute, or Sao2 < or =80%.

RESULTS

The incidence of apnea > or =20 seconds was low, with no significant difference between infant groups. Referral infants exhibited a higher occurrence of desaturation episodes (20 +/- 6 vs 6 +/- 3 episodes/12-hour study) and a higher occurrence of bradycardia episodes (4.3 +/- 0.8 vs 1.1 +/- 0.3 episodes/12-hour study) than controls. These episodes of desaturation and bradycardia were always preceded by a respiratory pause, which was shorter in the referral infants (10.0 +/- 0.4 seconds vs 12.0 +/- 1.0 seconds). Baseline Sao2 was lower in referrals than controls (95 +/- 1% vs 98 +/- 1%), and the incidence of periodic breathing was significantly higher.

CONCLUSIONS

Infants referred for apnea monitoring studies because of persistent bedside monitor alarms have very infrequent prolonged apnea but a higher frequency of desaturation and bradycardia in response to short respiratory pauses than infants without persistent bedside monitor alarms. Referral infants also exhibit a lower baseline Sao2. These abnormalities in oxygenation and cardiorespiratory control may be markers for subtle residual lung disease or functional central nervous system abnormalities.

Caffeine citrate: a review of its use in apnoea of prematurity

Apnoea of prematurity is a common condition in neonates born at less than 37 weeks' gestational age; it affects approximately 90% of premature neonates weighing under 1000 g at birth, and 25% of infants with a birthweight of less than 2500 g. Caffeine, a methylxanthine which occurs naturally in many plants, has been used for over 20 years to treat apnoea of prematurity. In a recent double-blind, placebo-controlled trial, apnoea was eliminated or reduced by at least 50% in significantly more neonates receiving caffeine citrate as first-line treatment than those receiving placebo. In a nonblind trial, caffeine citrate was more effective at reducing apnoeic episodes when compared with neonates receiving no treatment. Caffeine as first-line treatment demonstrated similar efficacy to theophylline or aminophylline (theophylline ethylenediamine) in 4 small randomised studies. Caffeine citrate was generally well tolerated in short term clinical trials, with very few adverse events reported. Caffeine was associated with fewer adverse events than theophylline in randomised trials. No differences in the incidence of individual adverse events were reported between caffeine citrate and placebo in a double-blind, randomised trial. Long term tolerability data are not yet available.

CONCLUSIONS

Caffeine citrate was generally well tolerated by neonates in clinical trials and it decreased the incidence of apnoea of prematurity compared with placebo. It has demonstrated similar efficacy to theophylline, but is generally better tolerated and has a wider therapeutic index. Caffeine citrate should, therefore, be considered the drug of choice when pharmacological treatment of apnoea of prematurity is required.

Risks and benefits of therapies for apnoea in premature infants

Apnoea in infants can result from a wide range of causes, and requires thorough evaluation before deciding on appropriate treatment. Continuous monitoring of premature infants with apnoea is mandatory in order to define the pathophysiology and type of apnoea; selection of treatment involves careful assessment of aetiology, as well as efficacy and tolerability in each individual case. The objective of treatment is to prevent the deleterious consequences of apnoeas that last >20 seconds and/or are associated with bradycardia, cyanosis or pallor, and occur more often than once an hour over a 12-hour period. Apnoea management involves both pharmacological and nonpharmacological treatment. We suggest methylxanthines as first-line therapy for idiopathic apnoeas; evidence suggests that caffeine is better tolerated and as efficacious as theophylline (since it is particularly efficacious against the 'central' component of idiopathic apnoea of prematurity). If treatment fails, additional measures such as doxapram may be appropriate when hypoventilation is present, or nasal continuous positive airway pressure when upper airway instability or obstructive apnoeas are predominant. Apnoea prophylaxis is an additional reason to advocate prenatal maturation with betamethasone. Weaning from treatment is attempted 4 to 5 days after complete resolution of apnoea, beginning with the last treatment introduced. Monitoring should be maintained for 4 to 5 days to detect any relapse of recurrent and severe apnoeas, which would lead to the resumption of the most recently withdrawn treatment.

Methylxanthine treatment for apnea in preterm infants

BACKGROUND

Recurrent apnea is common in preterm infants, particularly at very early gestational ages. These episodes of loss of effective breathing can lead to hypoxemia and bradycardia which may be severe enough to require resuscitation including use of positive pressure ventilation. Methylxanthines have been used to stimulate breathing and prevent apnea and its consequences.

OBJECTIVES

The objective of this review is to determine if methylxanthine treatment in preterm infants with recurrent apnea leads to a clinically important reduction in apnea and use of intermittent positive pressure ventilation (IPPV), without clinically important side effects.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts of conferences and symposia proceedings, expert informants, journal handsearching mainly in the English language.

SELECTION CRITERIA

All trials utilising random or quasi-random patient allocation, in which methylxanthine (theophylline or caffeine) was compared with placebo or no treatment for apnea in preterm infants, were included.

DATA COLLECTION AND ANALYSIS

Methodological quality was assessed independently by the two authors. Data were extracted independently by the two authors. Treatment effects were expressed as relative risk (RR) and risk difference (RD) and their 95% confidence intervals, using a fixed effect model. For significant results, the inverse of the risk difference (1/RD) was used to calculate the number needed to treat (NNT).

MAIN RESULTS

The results of four trials which enrolled a total of 110 preterm infants with apnea indicate that methylxanthine therapy leads to a reduction in apnea and use of IPPV in the first 2 - 7 days. There are insufficient data to evaluate side effects and no data to examine effects within different gestational age groups. There are no trial data which examine long term effects.

REVIEWER'S CONCLUSIONS

Methylxanthines are effective in reducing the number of apneic attacks and the use of mechanical ventilation in the two to seven days after starting treatment. In view of its lower toxicity, caffeine would be the preferred drug. Although the safety of methylxanthine therapy has been suggested in cohort studies, there are no trial data on longterm outcome. In order to indicate which infants are likely to benefit from treatment, there is a need for stratification by gestation and/or other risk factors in future studies. In any future studies the longer term effects of treatment on growth and development should be evaluated.

Monitoring of heart and respiratory rates in newborn infants using a new photoplethysmographic technique

OBJECTIVE

A new photoplethysmographic (PPG) device for respiratory and heart rate monitoring has been evaluated in the neonatal care units at the University Children's Hospital of Uppsala, Sweden. The purpose of this study was to compare this new device with more established techniques, i.e., transthoracic impedance plethysmography (TTI) for monitoring of respiratory rate and ECG for heart rate monitoring.

METHODS

Data were acquired continuously for 8-hours in each of 6 neonates. The signals were analysed for periods of 30 seconds, in which the heart and respiratory signals from the PPG device were compared with the ECG and the impedance plethysmogram.

RESULTS

The ECG recordings were of high quality in 77% of the analysed periods. In these periods, excluding periods (6%) disturbed by offset-adjustement of the PPG signal, the PPG heart signal included 1.1% (+/- 0.7% SD) false negative beats and 0.9% (+/- 0.6%) false positive beats. In periods with an impedance signal of high quality (29% of total time), the part of the PPG signal synchronous with respiration included 2.7% (+/- 1.1%) false negative breaths and 1.5% (+/- 0.4%) false positive breaths. Here, 2% of the periods were discarded because of offset-adjustment. From the periods of low signal quality, two other conclusions were drawn: 1) The impedance signal contains more power in the respiratory range than the corresponding PPG respiratory signal. 2) The breaths are easier to identify in the PPG respiratory signal than in the impedance signal (subjective measure).

CONCLUSIONS

Electrode and motion artefacts seem to disturb the ECG signals and, particularly, the impedance signals. During periods of high quality ECG and impedance signals, the new optical device produces signals of equal quality to these traditional methods, and is in some cases even better. The new device is non-invasive and has a small optical probe. These factors indicate further advantages of the photoplethysmographic method.