Early childhood neurodevelopment in very low birth weight infants with predischarge apnea

Monitoring and management of brain hemodynamics and oxygenation

While cardiorespiratory monitoring is standard for newborns in the NICU, monitoring of brain hemodynamics and oxygenation is usually sporadic and targeted to newborns with suspected or confirmed neurologic disorders. This is unfortunate, since critically ill newborns, both preterm and term-born, are at high risk of brain injury and would benefit from improved techniques for continuous monitoring of brain hemodynamics and oxygenation, in addition to monitoring of systemic hemodynamics and oxygenation. Near-infrared spectroscopy (NIRS) and, to a lesser extent, Doppler ultrasound are techniques that have been used in research and increasingly for clinical purposes to measure and monitor brain hemodynamics and oxygenation in newborns. NIRS monitoring can be useful for detection of diverse pathologic conditions that occur frequently in very preterm newborns and in selected populations of term newborns at risk for brain injury related to disturbances of systemic hemodynamics. This chapter reviews the current state of the art with regard to brain-monitoring techniques and the research directed at this important area, and it concludes with suggestions for the use of currently available tools to manage newborns at high risk of neurologic injury from disturbances in brain hemodynamics and oxygenation.

The impact of preterm birth <37 weeks on parents and families: a cross-sectional study in the 2 years after discharge from the neonatal intensive care unit

BACKGROUND

Little is known about the quality of life of parents and families of preterm infants after discharge from the neonatal intensive care unit (NICU). Our aims were (1) to describe the impact of preterm birth on parents and families and (2) and to identify potentially modifiable determinants of parent and family impact.

METHODS

We surveyed 196 parents of preterm infants <24 months corrected age in 3 specialty clinics (82% response rate). Primary outcomes were: (1) the Impact on Family Scale total score; and (2) the Infant Toddler Quality of Life parent emotion and (3) time limitations scores. Potentially modifiable factors were use of community-based services, financial burdens, and health-related social problems. We estimated associations of potentially modifiable factors with outcomes, adjusting for socio-demographic and infant characteristics using linear regression.

RESULTS

Median (inter-quartile range) infant gestational age was 28 (26-31) weeks. Higher Impact on Family scores (indicating worse effects on family functioning) were associated with taking ≥3 unpaid hours/week off from work, increased debt, financial worry, unsafe home environment and social isolation. Lower parent emotion scores (indicating greater impact on the parent) were also associated with social isolation and unpaid time off from work. Lower parent time limitations scores were associated with social isolation, unpaid time off from work, financial worry, and an unsafe home environment. In contrast, higher parent time limitations scores (indicating less impact) were associated with enrollment in early intervention and Medicaid.

CONCLUSIONS

Interventions to reduce social isolation, lessen financial burden, improve home safety, and increase enrollment in early intervention and Medicaid all have the potential to lessen the impact of preterm birth on parents and families.

Clinical associations of immature breathing in preterm infants: part 1-central apnea

BACKGROUND

Apnea of prematurity (AOP) is nearly universal among very preterm infants, but neither the apnea burden nor its clinical associations have been systematically studied in a large consecutive cohort.

METHODS

We analyzed continuous bedside monitor chest impedance and electrocardiographic waveforms and oxygen saturation data collected on all neonatal intensive care unit (NICU) patients <35 wk gestation from 2009 to 2014 (n = 1,211; >50 infant-years of data). Apneas, with bradycardia and desaturation (ABDs), defined as central apnea ≥10 s associated with both bradycardia <100 bpm and oxygen desaturation <80%, were identified using a validated automated algorithm.

RESULTS

Number and duration of apnea events decreased with increasing gestational age (GA) and postmenstrual age (PMA). ABDs were more frequent in infants <31 wk GA at birth but were not more frequent in those with severe retinopathy of prematurity (ROP), bronchopulmonary dysplasia (BPD), or severe intraventricular hemorrhage (IVH) after accounting for GA. In the day before diagnosis of late-onset septicemia and necrotizing enterocolitis, ABD events were increased in some infants. Many infants continued to experience short ABD events in the week prior to discharge home.

CONCLUSION

Frequency of apnea events is a function of GA and PMA in infants born preterm, and increased apnea is associated with acute but not with chronic pathologic conditions.

Unbound unconjugated hyperbilirubinemia is associated with central apnea in premature infants

OBJECTIVE

To evaluate whether jaundice, indexed by unbound bilirubin (UB), is associated with central apnea in premature infants.

STUDY DESIGN

A prospective observational study was performed with 27-33 weeks' gestational age infants who were not requiring either mechanical ventilation or noninvasive ventilation with continuous positive airway pressure beyond 24 hours after birth. Infants with congenital infections, chromosomal disorders, craniofacial anomalies, and/or family history of hearing loss were excluded. Total serum bilirubin and UB were measured twice daily during the first postnatal week and then when clinically indicated. Central apnea was evaluated by visual inspection of continuous, electronic cardiorespiratory recordings until 2 weeks of age.

RESULTS

One hundred infants were subdivided into 2 groups via median peak UB level: the high UB group (greater than median) and low UB group (less than median). The high UB group had an increased frequency of apnea events during the first 2 weeks compared with infants in the low UB group. After we controlled for confounders, the high UB group had more events of apnea during the first 2 postnatal weeks compared with the low UB group (incidence rate ratio: 1.9, 95% CI 1.2-3.2).

CONCLUSIONS

Our findings suggest that jaundice, as indexed by UB, is associated with central apnea in premature infants.

Current definitions for neonatal apnoea: are they evidence based?

Apnoea is defined as cessation of breathing with implicit pathophysiology. This review considers definitions of neonatal apnoea currently available and explores the evidence to support their use. For preterm and term infants, apnoea definitions appear arbitrary, are not supported by guidelines and vary from study to study. Although most alarms on infant breathing monitors are set to alert after a respiratory pause >20s duration is detected, this time period is the equivalent of 17 missed breaths in a preterm infant. Apnoea is likely to be better defined by associated consequence than by pause duration alone in this age group; however, the degree of change in heart rate or oxygen saturation that defines a respiratory pause as pathological is yet to be defined. Further research is required to determine the characteristics that differentiate respiratory events of clinical consequence from normal respiratory variability in term and preterm infants.

Monitoring apnea of prematurity: validity of nursing documentation and bedside cardiorespiratory monitor

OBJECTIVE

To compare apnea events recorded by bedside cardiorespiratory monitor and nursing documentation with those detected by visual inspection of continuous electronic cardiorespiratory waveform.

METHODS

In a prospective observational study, 20 nonventilated infants of 28 to 33 weeks' gestational age were monitored for apnea during the first 2 postnatal weeks. Apnea was defined as a respiratory pause > 20 seconds or > 15 seconds if associated with a heart rate < 80/min or oxygen saturation < 85%. True apnea was defined as one for which visual inspection of continuous electronic cardiorespiratory waveform on the central monitor verified apnea.

RESULTS

The number of apnea episodes recorded by nursing documentation and bedside monitors were 207 and 418, respectively. Only 7.7% of apnea events recorded by nursing documentation were confirmed as true apnea compared with 50.4% of apnea recorded by bedside monitors and the difference was statistically significant. Of true apnea (n = 211) episodes recorded on central monitors, 99% were recorded by bedside monitors but only 7.6% of apnea occurrences were recorded by nursing personnel.

CONCLUSIONS

Nursing documentation does not provide accurate monitoring of apnea. Although bedside monitors have better sensitivity and specificity than nursing documentation, future research should be directed to improve the specificity of bedside monitoring.

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.

Longitudinal assessment of hemoglobin oxygen saturation in preterm and term infants in the first six months of life

OBJECTIVE

To report longitudinal home recordings of hemoglobin O(2) saturation by pulse oximetry (Spo(2)) during unperturbed sleep in preterm and term infants.

STUDY DESIGN

We recorded continuous pulse oximetry during the first 3 minutes of each hour of monitor use (nonevent epochs) for 103 preterm infants born at <1750 g and ≤ 34 weeks postmenstrual age (PMA), and 99 healthy term infants.

RESULTS

Median baseline Spo(2) was approximately 98% for both the preterm and term groups. Episodes of intermittent hypoxemia occurred in 74% of preterm and 62% of term infants. Among infants with intermittent hypoxemia, the number of seconds/hour of monitoring <90% Spo(2) was initially significantly greater in the preterm than the term group and declined with age at a similar rate in both groups. The 75(th) to 95(th) percentiles for seconds/hour of Spo(2) <90% in preterm infants were highest at 36 weeks PMA and progressively decreased until 44 weeks PMA, after which time they did not differ from term infants.

CONCLUSIONS

Clinically inapparent intermittent hypoxemia occurs in epochs unperturbed by and temporally unrelated to apnea or bradycardia events, especially in preterm infants at 36 to 44 weeks PMA.

A model investigation of the impact of ventilation-perfusion mismatch on oxygenation during apnea in preterm infants

Ventilation-perfusion (V/Q) mismatch is a prominent feature of preterm infants and adults with lung disease. V/Q mismatch is known to cause arterial hypoxemia under steady-state conditions, and has been proposed as the cause of rapid arterial oxygen desaturation during apnea. However, there is little evidence to support a role for V/Q mismatch in the dynamic changes in arterial oxygenation that occur during apnea. Using a mathematical model, we quantified the effect of V/Q mismatch on the rate of desaturation during apnea to ascertain whether it could lead to rates of up to 10%s(-1) as observed in preterm infants. We used a lung-body model for the preterm infant that incorporated 50 parallel alveolar-capillary units that were ventilated and perfused with the severity of V/Q mismatch (sigma) defined conventionally according to sigma=S.D. of the distribution of V/Q ratios. Average desaturation rate 10s from apnea onset was strongly elevated with worsening V/Q mismatch as a result of an earlier desaturation of low V/Q units compared with high V/Q units. However, V/Q mismatch had little impact after apnea onset, with peak desaturation rate only substantially increased if mismatching caused a lowered resting arterial O(2) saturation. In conclusion, V/Q mismatch causes a more immediate onset of desaturation during apnea, and therefore places preterm infants and adults with lung disease at risk of hypoxemic dips. However, V/Q mismatch does not accelerate desaturation rate beyond apnea onset and cannot, therefore, explain the rapid desaturation observed during recurrent apnea in preterm infants.

Intermittent hypoxia in supine versus side position in term neonates

Supine sleeping, recommended to prevent sudden infant death, should be started in the delivery hospital, but meets concern that neonates may exhibit more intermittent hypoxia in this position. We aimed to demonstrate that intermittent hypoxia is equally rare in supine and side position. We enrolled 609 term neonates in a crossover study. Pulse oximeter saturation (Spo2) was recorded throughout; feeding periods were excluded. The rate of desaturation events to <80%/h was the primary study variable. Four hundred seventy-six recordings fulfilled study criteria. Mean duration of recording was 4.8 h in side and 4.9 h in supine position (SD 0.8 for both). There was a mean of 0.11 desaturation events per hour in supine and 0.05 per hour in side position. Of the 118 infants with desaturation events, more had such events only in supine position (64 vs. 31 infants). For supine compared with side position, the adjusted odds ratio for at least one desaturation event was 2.0 (95% confidence interval 1.3-3.1). The lowest Spo2 value reached during these events was 56% in supine and 53% in side position. These neonates had more desaturation events while sleeping supine. We speculate, however, that this positional effect likely is too small to affect outcome.

Comparison of enrollment in interventional therapies between late-preterm and very preterm infants at 12 months' corrected age

OBJECTIVE

To determine the requirement for therapeutic services of late-preterm infants (34 to 36 weeks' gestation) and morbidities associated with their developmental delays compared with their very preterm (<32 weeks' gestation) counterparts.

METHODS

We used a retrospective cohort study of former preterm children admitted to the neonatal unit who were evaluated at the Regional Neonatal Follow-up Program of Westchester Medical Center in New York at 12 +/- 2 months' corrected age from January 2005 through October 2006. Logistic regression was used to compare odds ratios between late-preterm and very preterm children who qualified for early intervention services. Antenatal, demographic, and neonatal factors were compared between subgroups.

RESULTS

Of the 497 preterm infants evaluated at the Regional Neonatal Follow-up Program, 127 met inclusion criteria (77 very preterm and 50 late-preterm infants). Of the late-preterm infants, 30% qualified for and received early intervention services, 28% physical therapy, 16% occupational therapy, 10% speech therapy, and 6% special education. In the very preterm subgroup, 70% qualified for and received early intervention services, 66% physical therapy, 32% occupational therapy, 32% speech therapy, and 21% special education. Very preterm children were more likely to be enrolled in therapies than their late-preterm counterparts. However, when adjusting for neonatal comorbidities of prematurity, there was no difference in enrollment in early intervention services between the very preterm and late-preterm infants.

CONCLUSIONS

After controlling for comorbidities of prematurity, we found that late-preterm infants requiring admission to the neonatal unit have the same risk as very preterm infants of requiring interventional therapies. This would indicate that it is not only the degree of prematurity but also the morbidities experienced in the neonatal period in conjunction with the period of rapid brain growth that have a profound influence on neurodevelopmental outcomes. This should be considered when planning their hospital discharge and follow-up.

Hyperbilirubinemia diminishes respiratory drive in a rat pup model

Although apnea is common in premature babies, there is a paucity of information concerning the pathophysiologic basis of these episodes and their relationship to other perinatal conditions such as hyperbilirubinemia. Unconjugated hyperbilirubinemia in premature infants, even in moderately high levels, may cause encephalopathy affecting brainstem functions and has been linked to increased incidence of apnea in these infants. Thus, there is a need to clarify mechanisms by which bilirubin may alter respiratory control and induce apnea of prematurity. In this study, bilirubin or placebo was infused i.v. in 9-d-old rat pups (n = 36). Serum hyperbilirubinemia peaked in the first hours after bilirubin infusion. Twenty-four hours after bilirubin infusion, respiration was recorded by plethysmography at rest and under hypercapnic and hypoxic conditions. In treated pups, minute ventilation in room air was significantly reduced, hyperventilatory response to CO2 was blunted, and hypoxic ventilatory depression was increased, compared with placebo-injected rat pups. Brainstem bilirubin deposition and immunoreactivity to bilirubin was detected in the brainstem on histologic analysis. We speculate that high serum bilirubin levels may cause prolonged inhibition of brainstem autonomic function and that this could underlie the exacerbation of apnea noted in premature babies who have experienced jaundice.

Factors influencing apnea and bradycardia of prematurity - implications for neurodevelopment

BACKGROUND

Apnea and bradycardia of prematurity (ABP) are possible risks towards damage of the developing brain.

OBJECTIVES

To characterize the influence of neonatal factors on ABP and to determine the relationship of ABP to neurodevelopmental outcome.

METHODS

ABP was described in very low birth weight infants (n = 83) using the frequency and severity of ABP episodes with a clinical score considering heart rate, oxygenation, duration and interventions performed during each episode. Neonatal factors were analyzed for their relationship to ABP using regression analysis. Neurodevelopment was investigated using the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI) of the Bayley Scales of Infant Development II at a corrected age of 13 months. Power of ABP parameters to predict outcome was assessed by logistic regression analysis.

RESULTS

ABP typically started within the first week after birth. Spontaneous resolution occurred at a postmenstrual age (PMA) of 36.0 +/- 2.2 (31.1-44.1) weeks. A delayed resolution (>36 weeks PMA) and a higher average daily ABP score during a defined developmental period (31-37 weeks PMA) were associated with a higher incidence of unfavorable outcome (MDI or PDI <69 or death).

CONCLUSION

ABP is an age-specific phenomenon. However, more severe courses than expected for PMA or the resolution at a later PMA indicated an increased risk of neurodevelopmental disturbances at a corrected age of 13 months.

Quality-of-care indicators for the neurodevelopmental follow-up of very low birth weight children: results of an expert panel process

OBJECTIVE

To develop a set of quality indicators for the neurodevelopmental follow-up care of very low birth weight (VLBW; <1500 g) children.

METHODS

We reviewed the scientific literature on predictors of neurodevelopmental outcomes for VLBW children and the clinical practice guidelines relevant to their care after hospital discharge. An expert panel with members nominated by the American Academy of Pediatrics, the National Institute of Child Health and Human Development, the Vermont Oxford Network, and the California Children's Service was convened. We used a modified Delphi method to evaluate and select the quality-of-care indicators.

RESULTS

The panel recommended a total of 70 indicators in 5 postdischarge follow-up areas: general care; physical health; vision, hearing, speech, and language; developmental and behavioral assessment; and psychosocial issues. Of these, 58 (83%) indicators were in preventive care, 5 (7%) were in acute care, and 7 (10%) were in chronic care.

CONCLUSION

The quality indicators cover follow-up care for VLBW infants with various medical conditions. Given the elevated rates of long-term neurodevelopmental disabilities and the potential impact of poor health care, this new set of indicators provides an opportunity to assess and monitor the quality of follow-up care with the ultimate aim of improving the quality of care for this high-risk population.

A primer on Apnea of prematurity

Apnea, the cessation of respiratory airflow, can begin in many preterm infants in the first week of life and can last until the day of discharge or beyond. This article provides an overview of the complex anatomic, physiological, and developmental mechanisms related to immaturity of both the central nervous system and musculature of the pulmonary system, that contribute to apnea of prematurity. Apnea of prematurity is a diagnosis of exclusion; an array of other conditions and stimuli can also cause apnea, including infections, pulmonary disease, and intracranial pathology. The standard clinical management of apnea, including cutaneous stimulation, methylxanthine therapy, and continuous positive airway pressure or ventilatory support, are discussed as well as newer investigational therapies, such as olfactory stimulation. Emerging evidence on the long-term neurodevelopmental impact of apnea is reviewed. Nursing measures to prevent and manage apnea are reviewed with an emphasis on parent education and preparation for discharge. Apnea resolves in most preterm infants as they approach term corrected gestational age; however, if it does not, options include continued hospitalization or, for infants with stable apnea, discharge with a home apnea monitor.

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.

Apnea is associated with neurodevelopmental impairment in very low birth weight infants

OBJECTIVE

To determine whether apnea in preterm infants is associated with abnormal neurodevelopmental outcome.

METHODS

We determined the number of days that apnea and bradycardia spells were noted by the nursing staff, during the initial hospitalization of 175 preterm infants of less than <1250 g birth weight or <32 weeks gestation who had been enrolled in the follow-up program of the Royal Victoria Hospital. Multiple logistic and multiple linear regression models were constructed to determine the relationships between apnea days and neurodevelopmental impairment at 3 years of age, after correcting for gestation, sex, intrauterine growth restriction, intraventricular hemorrhage, periventricular leukomalacia, pre- and postnatal steroids, and maternal education.

RESULTS

A total of 41 infants had neurodevelopmental impairment (Bayley MDI or PDI <70, cerebral palsy or blindness). By multiple logistic regression, an increasing number of days on which at least one apnea occurred, "total apnea days", and male sex were significantly associated with increasing probability of neurodevelopmental impairment, p<0.01, the sum of days of assisted ventilation and apnea days occurring after extubation was also associated with impairment in a separate regression model, p<0.001. Lower MDI at 3 years was significantly associated with postnatal steroid use, p=0.004. Lower PDI was associated with increasing apnea days, male sex, and postnatal steroid use, p<0.001. Functional impairment (a score on any one of the four dimensions of the Vineland scale <70), found in 17% of the infants, was associated with increasing apnea days, p<0.05. Caffeine treatment was not independently associated with any outcome.

CONCLUSION

An increasing number of days that apnea was recorded during hospitalization was associated with a worse outcome. Among the potential explanations for this finding is the possibility that multiple recurrent hypoxic and bradycardic spells may cause brain injury.

Doxapram 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. Doxapram has been used to stimulate breathing and so prevent apnea and its consequences.

OBJECTIVES

In preterm infants with recurrent apnea, does treatment with Doxapram lead to a clinically important reduction in apnea and use of intermittent positive airways pressure (IPPV), without clinically important side effects?

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal trials, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), MEDLINE from 1966 - June 2004, EMBASE from 1980 - June 2001, CINAHL from 1982- June 2004. Text words 'doxapram', 'apnea or apnoea' and the MeSH term 'infant, premature' were used. Previous reviews including cross references, abstracts from conferences and symposia proceedings were also examined. Abstracts of the Society for Pediatric Research were searched from 1996 - 2004 inclusive.

SELECTION CRITERIA

All trials utilising random or quasi-random patient allocation, in which doxapram was used for the treatment of apnea in preterm infants were included.

DATA COLLECTION AND ANALYSIS

Each author evaluated the papers for quality and inclusion criteria. Independent data extraction was carried out.

MAIN RESULTS

Only one trial, which randomized 11 infants to intravenous doxapram and 10 infants to placebo, was found. There were fewer treatment failures after 48 hours in the group of preterm infants treated with doxapram (4/11) compared with the group treated with placebo (8/10). The wide confidence intervals made this result non-significant [RR 0.45 (0.20, 1.05)]. Only one infant, who was from the placebo group, was given IPPV. Of the seven responders by 48 hours in the group of 11 who received doxapram, five failed to respond between 48 hours and seven days after commencement of therapy. This gives a late failure rate of 9/11, similar to the short term failure rate in the placebo group of 8/10. It is not possible to evaluate the late responses of all those in the placebo group since they crossed over to a treatment arm.

REVIEWERS' CONCLUSIONS

Although intravenous Doxapram might reduce apnea within the first 48 hours of treatment, there are insufficient data to evaluate the precision of this result or to assess potential adverse effects. No long term outcomes have been measured. Further studies are needed to determine the role of this treatment in clinical practice.

Carnitine supplementation for preterm infants with recurrent apnea

BACKGROUND

Apnea of prematurity is a common problem in preterm infants in the neonatal intensive care setting (NICU), often delaying their discharge home or transfer to a step down unit. Premature infants are at increased risk of carnitine deficiency. Carnitine supplementation has been used for both prevention and treatment of apnea.

OBJECTIVES

To determine whether treatment with carnitine will reduce the frequency of apnea, the duration of ventilation and the duration of hospital stay in preterm infants with recurrent apnea.

SEARCH STRATEGY

Computerised searches were carried out by two reviewers independently. Searches were made of MEDLINE (1966 to May 2004), EMBASE (1980 to May 2004), CINAHL (1982-2004 June 2004,1st week), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2004), abstracts of annual meetings of the Society for Pediatric Research (1995-2004), and contacts were made with the subject experts.

SELECTION CRITERIA

Only randomized or quasi-randomized treatment trials of preterm infants with a diagnosis of recurrent apnea of prematurity were considered. Trials were included if they involved treatment with carnitine compared to placebo or no treatment, and measured at least one of the following outcomes: failure of resolution of apneas, the duration of ventilation and the duration of hospital stay.

DATA COLLECTION AND ANALYSIS

Two reviewers evaluated the papers for inclusion criteria and quality. Corresponding authors were contacted for further information where needed.

MAIN RESULTS

No eligible trials were identified.

REVIEWERS' CONCLUSIONS

Despite the plausible rationale for the treatment of apnea of prematurity with carnitine, there are insufficient data to support its use for this indication. Further studies are needed to determine the role of this treatment in clinical practice.

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.

Neonatal cardiorespiratory monitoring techniques

Episodes of apnoea, desaturation and bradycardia are a common occurrence in preterm infants and are known to persist after hospital discharge. These events are typically detected by clinical bedside monitoring, but the type and number of events depend on alarm settings, the inclusion of continuous pulse oximetry and the mode of respiratory monitoring used. The long term effects of cardiorespiratory events remain controversial; however, some studies have suggested an association between prolonged apnoea and morbidity such as impaired neurodevelopmental outcome. Common clinical practice requires an event-free period before hospital discharge, although the specific length of time varies between institutions. Therefore, with the current demand to shorten hospital stay, the possible persistence of cardiorespiratory events after hospital discharge and the potential consequences of these events, cardiorespiratory monitoring remains a subject of considerable interest. Since cardiorespiratory event detection is dependent on the mode of monitoring used, this chapter will focus on both the respiratory patterns and types of cardiorespiratory events that occur in the infant population and the modalities of cardiorespiratory monitoring currently available to detect these events.

Role of carnitine supplementation in apnea of prematurity: a systematic review

OBJECTIVE

To determine the role of carnitine supplementation in premature infants on apnea of prematurity, length of ventilation and duration of hospital stay.

METHODS

Two reviewers independently conducted a literature search for relevant studies. No language restrictions were applied. Decisions to include studies for the review, and methodological quality of the included studies were assessed in duplicate based on predetermined criteria.

RESULTS

Three studies met the selection criteria (reproducibility-kappa 0.76+/-SE 0.122). One study was later excluded. Both included studies were randomized double-blind placebo control prevention trials among babies <1500 g of weight. There was no difference among the groups for outcomes of bedside nurse recorded frequency of apnea episodes, continuous objective recording of apnea, length of ventilation (WMD -3.24 days, 95% CI -8.39, 1.92) or length of hospital stay (WMD -5.4 days, 95% CI -15.53, 4.72).

CONCLUSION

Present evidence does not support the regular use of carnitine for the prevention of apnea of prematurity.

Preterm infants' behavioural indicators of oxygen decline during bottle feeding

BACKGROUND

During the time when preterm infants' oral feeding skills are developing they often experience physiological instability and need assistance from caregivers to maintain adequate oxygenation. Assisting infants to maintain optimal oxygenation during oral feeding requires an understanding of how they express and aim to self-regulate their oxygen status.

AIM

The purpose of this study was to identify potential behavioural indicators of declining oxygenation during preterm infant early bottle-feeding.

METHOD

The design was explorative. Data were collected from a secondary analysis of 20 videotapes of preterm infant bottle feedings which included concurrent oxygen saturation data. In this analysis infant behaviours and quality of breathing were coded and compared across three periods: high oxygen saturation, immediately preceding an oxygen desaturation event, and during an oxygen desaturation event.

FINDINGS

Infants gave limited behavioural indicators of declining oxygenation. Immediately prior to a desaturation event, they had an increase in eye flutter and were typically sucking and apnoeic. During a desaturation event, they typically relaxed their arms/hands and stopped sucking.

CONCLUSIONS

Reliance on preterm infant behavioural cues will be insufficient for detection of oxygen desaturation during oral feeding. Attention to changes in breath sounds and to the pattern of sucking are potentially important intervention strategies for the prevention of and appropriate response to oxygen decline during feeding. Sucking pauses may be a time when preterm infants aim to regulate their breathing pattern and thereby increase oxygenation. Interventions that focus on detection and minimization of apnoea during feeding, and which aim to protect infant sucking pauses, may reduce the number and severity of desaturation events preterm infants experience during bottle feeding.

Treatment of apnea of prematurity

In the last decade, knowledge regarding the neurodevelopment and functional aspects of the respiratory centers during postnatal maturation has increased substantially. However, an increase in such knowledge has not provided a basis for change in practice. The diagnosis of apnea of prematurity (AOP) is one of exclusion. All causes of secondary apnea must be ruled out before initiating treatment for AOP. Treatment will depend on the etiology as well as effectiveness and tolerability of the treatment by the patient. The primary goal of any treatment of AOP is to prevent the frequency of apnea lasting >20 seconds, and/or those that are shorter, but associated with cyanosis and bradycardia. The clinical management of AOP is not much different today than it was two decades ago, with pharmacologic and nonpharmacologic treatment options remaining the mainstay of therapy. Methylxanthines are still the most widely used pharmacologic agents. Due to the wider therapeutic index of caffeine and ease of once daily administration, it should be the preferred agent. Doxapram, or nonpharmacologic treatment measures such as nasal continuous positive airway pressure, may be considered in infants who are unresponsive to methylxanthine treatment alone. Treatment should be continued until there is complete resolution of apnea, and for some time thereafter. The choice of method for weaning treatment remains one of individual physician preference. Discharge from hospital after apnea requires close monitoring and some infants will require home apnea monitors. The decision to provide a home apnea monitor should be individualized for each patient, depending on the effectiveness of treatment and clinical response.

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.

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.

Prophylactic doxapram for the prevention of morbidity and mortality in preterm infants undergoing endotracheal extubation

BACKGROUND

When preterm infants have been given intermittent positive pressure ventilation (IPPV) for respiratory failure, weaning from support and tracheal extubation may be difficult. A significant contributing factor is thought to be the relatively poor respiratory effort and tendency to develop hypoventilation and apnea, particularly in very preterm infants. Doxapram stimulates breathing and appears to act via stimulation of both the peripheral chemoreceptors and the central nervous system. This effect might increase the chance of successful tracheal extubation.

OBJECTIVES

In preterm infants being weaned from IPPV and in whom endotracheal extubation is planned, does treatment with doxapram reduce the use of intubation and IPPV, or reduce other morbidity, without clinically important side effects? In this regard, how does doxapram compare with standard treatment or with an alternative treatment such as methylxanthine or CPAP? Subgroup analyses were prespecified according to birth weight and/or gestational age, use of co-interventions (methylxanthines or nasal CPAP), and route of administration (intravenous or oral).

SEARCH STRATEGY

The standard search strategy of the Neonatal Review Group as outlined in the Cochrane Library was used. This included searches of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register, MEDLINE and EMBASE.

SELECTION CRITERIA

Eligible studies included published trials utilising random or quasi-random patient allocation in which preterm or low birth weight infants being weaned from IPPV were given doxapram compared with standard care or other treatments, to facilitate weaning from IPPV and endotracheal extubation. Trials were independently assessed by the authors before inclusion.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Collaboration and its Neonatal Review Group were used. Each author extracted data separately; the results were compared and any differences resolved. The data were synthesized using the standard method of Neonatal Review Group with use of relative risk and risk difference.

MAIN RESULTS

Two trials involving a total of 85 infants compared doxapram and placebo. In both the individual trials and the meta-analyses there were no significant differences between the doxapram and placebo groups in any of the outcomes (failed extubation, death before discharge, respiratory failure, duration of IPPV, side effects, oxygen at 28 days or oxygen at discharge). There was a trend towards an increase in side effects (hypertension or irritability leading to cessation of treatment) in the doxapram group [summary RR 3.21 (0.53, 19.43). In one of these two trials (Huon 1998) an 'alarming rise in blood pressure' occurred in five infants in the doxapram group and none of the controls, although in only one was treatment withdrawn. One additional trial involving only eight infants compared doxapram with aminophylline, but there were insufficient data for meaningful analysis.

REVIEWER'S CONCLUSIONS

The evidence does not support the routine use of doxapram to assist endotracheal extubation in preterm infants who are eligible for methylxanthine and/or CPAP. The results should be interpreted with caution because the small number of infants studied does not allow reliable assessment of the benefits and harms of doxapram. Further trials are required to evaluate the benefits and harms of doxapram compared with no treatment or with other treatments, such as methylxanthines or CPAP, to evaluate whether it is more effective in infants not responding to these other treatments, and to assess whether the drug is effective when given orally.