Determinants of energy expenditure in ventilated preterm infants

The purpose of this study was to determine oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure (EE) in a group of preterm ventilated infants during the first 3 weeks of life, and to determine the major factors that influence EE. Thirty-eight indirect calorimetry studies were performed in 18 ventilated infants with mean gestational age of 27.9 +/- 0.6 (SEM) weeks. The relationship of demographic factors, nutrient intake, and severity of illness assessments of EE were determined by regression analysis. Repeated measure analysis was performed for the effect of multiple studies in the same patient. Although VO2, VCO2, and EE all tended to increase over the first 3 weeks of life, there was a wide range of values. EE was best predicted by nonprotein calorie intake and postnatal age, while there was no correlation with birthweight, weight at the time of study, gestational age, protein intake, or severity of illness. Multiple regression analyses demonstrated a strong interaction between PNA and EI. In this population EE is best predicted by PNA and EI. The interactive effect between PNA and EI on EE is probably explained by the clinical practice of daily increments in substrate intake in these patients.     

Influence of increasing postnatal age on respiratory timing and reflex activity in preterm ventilated infants.

The influence of postnatal age on spontaneous respiratory time, measured both on and off continuous positive airways pressure (CPAP), and the occurrence of the Hering Breuer reflex has been investigated. Consecutive ventilated infants were recruited and only studied when making respiratory efforts during mechanical ventilation. Fifty-three infants were studied on 119 occasions, their median gestational age was 29 weeks and birthweight 1142 gms. All the infants were initially ventilated for the respiratory distress syndrome. Inspiratory and expiratory times were measured from simultaneous flow and oesophageal pressure recordings during a 20-second period of disconnection and during a similar period on 3 cmH2O CPAP. Prolongation of the inspiratory and expiratory time on CPAP compared to that measured during disconnection of more than 10% was evidence of the Hering Breuer reflex. No significant change in the inspiratory or expiratory time either on or off CPAP was noted either between days 1 to 5 or weeks 1 to 4. Both inspiratory and expiratory time tended to be longer on CPAP than during disconnection and these differences reached significance on days 1 and 2 and weeks 1 and 2. No influence of postnatal age was demonstrated on the proportion of infants in whom the Hering Breuer reflex was demonstrated. Our results suggest that, during the neonatal period, there is no influence of postnatal age on respiratory timings or reflex activity amongst ventilated infants who make spontaneous respiratory efforts during ventilation. These results have important implications regarding the optimum rate at which such infants should be ventilated.     

End-tidal CO2 as a function of tidal volume in mechanically ventilated infants

OBJECTIVE: To test the hypothesis that end-tidal CO(2) (PETCO(2)) varies with tidal volume (Vt) in preterm infants. DESIGN: Intervention study, nonrandomized trial. SETTING: Neonatal ICU, regional referral center. SUBJECTS: 29 preterm infants 790 to 2135 g in weight requiring mechanical ventilation studied on 73 occasions. INTERVENTION: Measurement of PETCO(2) during variations of Vt. MEASUREMENT: Statistical correlation of PETCO(2) to Vt. Result: PETCO(2) is minimal when Vt is either too low or too high. CONCLUSION: Vt, through its effect on dead space/Vt (Vd/Vt) ratios and arterial-alveolar CO(2) differences, has a significant effect on PETCO(2). Observation of PETCO(2) across a range of Vt can be used to select an appropriate Vt for preterm infants requiring mechanical ventilation.     

Purulence and gram-negative bacilli in tracheal aspirates of mechanically ventilated very low birth weight infants.

OBJECTIVE: Tracheal aspirates (TAs) from mechanically ventilated very low birth weight (VLBW) infants are frequently obtained during the evaluation of suspected sepsis, tracheitis, or ventilator-associated pneumonia (VAP). Purulence and bacteria in Gram stain of bronchopulmonary secretions are considered signs of respiratory infection, and medical decisions are made on the assumption that they are predictors of positive bacterial tracheal cultures (TCs). The purpose of this retrospective investigation was to establish the relationship of purulence and bacteria in TA from ventilated VLBW infants with positive TC and to identify its clinical significance. STUDY DESIGN: One hundred and seventy consecutively born VLBW infants (1996 to 1998) who remained on mechanical ventilation longer than 1 week were studied. Demographic, laboratory, and clinical data were obtained from hospital medical records. Purulence, defined by the number of polymorphonuclear leukocytes (PMNs) per low power field (LPF), was reported as light (<25 PMNs/LPF) or moderate/heavy (>or=25 PMNs/LPF) for every TA. RESULTS: Purulence was absent in 469 of 646 (72%) TA taken from 170 infants. Light purulence was present in 17% and moderate/heavy purulence in 11%. TCs were positive in 58% of non-purulent, 94% of light, and 100% of moderate/heavy purulent TA. Bacteria on Gram stain were present in 12% of non-purulent, 70% of light purulent, and 83% of moderate/heavy purulent TA. Moderate/heavy purulence in TA was predictive of a positive TC with Gram-negative bacilli (GNB) with 70% sensitivity, 100% specificity, 100% positive predictive value, and 67% negative predictive value. Purulence in TA, as well as GNB airway colonization, became more frequent as mechanical ventilation progressed and was not associated with a particular GNB species. There were 79 infants who never had purulent TA and 91 who, at some time during the hospitalization, did. At the time of first purulent TA, 65 (71%) of 91 infants were asymptomatic. Twenty-six infants (29%) had clinical deterioration for which they underwent sepsis work-up. Three had blood stream infection, 5 VAP, 5 tracheitis, and 13 respiratory complications of non-infectious etiology. Four of five VAP infants died; all others survived. CONCLUSION: In VLBW infants, purulence in TA is associated with prolonged endotracheal intubation and is temporally related to GNB airway colonization. At the time of the first purulent TA, the majority of mechanically ventilated VLBW infants are asymptomatic. Only a few symptomatic VLBW infants had nosocomial respiratory infection. Understanding the clinical significance of purulence and GNB in TA from this unique patient population is important for management and prognosis, and it may decrease concern for infection and the associated use of antibiotics.     

Factors affecting plasma bilirubin in preterm infants ventilated for respiratory distress syndrome.

OBJECTIVE: To evaluate the contribution of various factors to plasma bilirubin level in preterm infants with a birth weight of < 1500 gm in need of mechanical ventilation for respiratory distress syndrome (RDS) during their first week of life. METHODOLOGY: A total of 50 very low birth weight (< 1500 gm) preterm infants consecutively admitted to the neonatal intensive care unit were studied. Plasma bilirubin levels were determined every 8 hours for the first week of life. Data relating to daily body weight, daily fluid intake, age at onset of gavage feeds, daily caloric intake, and grade of intraventricular hemorrhage (IVH) were collected. Data relating to mechanical ventilation were collected every 4 hours as follows: fractional inspired O2, arterial PO2, arterial PCO2, and mean airway pressure. An arterial/alveolar PO2 ratio and a corrected oxygenation index were computed for the first 2 days of life. A bilirubin index (BI), defined as the ratio of peak plasma bilirubin level to birth weight1/3, was used to study the association between bilirubin and the above variables. A BI was also used as a criterion for starting and discontinuing phototherapy. Multiple linear regression analysis was used to model BI. RESULTS: IVH (p < 0.0001), age at onset of gavage feeds (p < 0.003), oxygenation index (p < 0.007), and gestational age (p < 0.05) made a significant contribution to variations in BI (37.16%, 43.71%, 48.99%, and 53.33%, respectively). CONCLUSION: Hyperbilirubinemia in ventilated preterm infants with RDS is most likely multifactorial; entities quite distinct from RDS (such as nutrition and IVH) may significantly contribute to its variation.     

Nipple shields for preterm infants: effect on milk transfer and duration of breastfeeding.

This study reports breastfeeding outcomes for 34 preterm infants whose mothers used ultrathin silicone nipple shields to increase milk transfer. Mean milk transfer was compared for 2 consecutive breastfeedings without and with the nipple shield. Total duration of breastfeeding was calculated for a maximum of 365 days. Mean milk transfer was significantly greater for feedings with the nipple shield (18.4 ml vs. 3.9 ml), with all 34 infants consuming more milk with the nipple shield in place. Mean duration of nipple shield use was 32.5 days, and mean duration of breastfeeding was 169.4 days; no association between these variables was noted. The nipple shield was used for 24.3% of the total breastfeeding experience, with no significant association between the percentage of time the shield was used and total duration of breastfeeding. These findings are the first to indicate that nipple shield use increases milk intake without decreasing total duration of breastfeeding for preterm infants.     

Breast milk supplementation for preterm infants: parental preferences and postdischarge lactation duration

Breast milk supplementation is frequently used to improve preterm infant growth and to achieve satisfactory intakes of minerals and vitamins. In the North American market there are commercial preparations: two powders and a liquid. The nutritional data available suggest these products are similar and their utilization is based on healthcare team choice. Parental perception about supplementation has not been previously evaluated although parental attitudes are known to impact on lactation success. The objectives of this paper are to determine parental preference and breastfeeding duration for very-low-birth-weight infants given commercial breast milk enrichment products. The study design is a randomized clinical trial with parental interviews. Sixty-three families with 71 infants were enrolled. Parents expressed their preference for the addition of a powder over a liquid preparation (p<0.01). Those mothers whose infants received the liquid enrichment had a shorter lactation relative to their goal, compared with the mothers of the infants who received the powder (p = 0.017). Parents prefer a powder product for breast milk supplementation and this choice positively impacts on the duration of breastfeeding for very-low-birth-weight infants.     

Effects of open vs. closed system endotracheal suctioning on cerebral blood flow velocities in mechanically ventilated extremely low birth weight infants

BACKGROUND: Endotracheal (ET) suctioning causes cardiovascular side effects and may impair cerebral hemodynamics. Subjectively, these effects are worse if patients are disconnected from the ventilator (open system suctioning, OSS) than if they remain connected to the ventilator during suctioning (closed system suctioning, CSS). It is uncertain whether the response to ET suctioning is similar in conventionally (CV) and high frequency (HF) ventilated patients. OBJECTIVES: To investigate if the mode of suctioning or of mechanical ventilation influences cerebral blood flow velocities (CBFVs) in extremely low birth weight (ELBW) infants. METHODS: Transcranial Doppler sonography in the middle cerebral artery during OSS and CSS in CV and HF ventilated ELBW infants. RESULTS: Forty-one measurements were performed in 19 infants within the first two weeks of life. Mean CBFVs decreased during suctioning from baseline 18.8 to 14.3 cm/s (-24%), increased thereafter to 24.7 cm/s (73%) and then returned to baseline (20.8 cm/s). Changes in CBFV were less pronounced in infants with higher baseline CBFVs. Heart rate decreased during ET suctioning and thereafter returned to baseline values. The alterations in CBFV and heart rate were both independent of the mode of ventilation or suctioning. CONCLUSIONS: The mode of suctioning or ventilation does not influence CBFVs in ELBW infants.     

Role of presepsin in the diagnosis of late-onset neonatal sepsis in preterm infants

Objective: One of the most challenging aspects in the management of neonates with late-onset neonatal sepsis (LOS) is to make the diagnosis. Presepsin is a novel and promising marker of sepsis. The aim of this study was to assess the role of presepsin in the diagnosis of LOS in preterm infants.

Methods: Forty-two premature newborns ≤32 weeks gestational age with a diagnosis of LOS were prospectively involved in the study. Forty gestational and postnatal age-matched infants without sepsis served as controls. Levels of presepsin, C-reactive protein, and procalcitonin were measured at enrollment and on the third and seventh days of sepsis.

Results: Initial presepsin levels in the LOS group were significantly higher than in the control group (1024?pg/mL, min–max: 295–8202; versus 530?pg/mL, min–max: 190–782; p?<?0.0001). The area under the receiver-operating curve for presepsin was 0.864. A presepsin value of 800.5?pg/mL was established as a cut-off value, with 67% sensitivity and 100% specificity. Presepsin levels gradually decreased during treatment.

Conclusion: Presepsin can be used as a reliable biomarker for LOS and treatment response in preterm infants. However, we could not demonstrate the efficacy of presepsin for the detection of disease severity or prognosis.     

Respiratory inhibition after crying and feeding hypoxemia in infants

Objective: To determine the incidence, risk factors and natural history of respiratory inhibition after crying (RIAC) and feeding hypoxemia.

Methods: We screened for RIAC and feeding hypoxemia among 393 infants with a gestational age ≥?36 weeks using pulse oximetry. Twenty-seven infants were treated in the neonatal intensive care unit.

Results: RIAC and feeding hypoxemia were observed in 95 (24.2%) and 124 (31.6%) infants, respectively. RIAC correlated with feeding hypoxemia (p?<?0.001), grade II increased echogenicity in the ganglionic eminence (p?=?0.005), dilation of the lateral ventricle (p?=?0.044), threatened premature labor (p?=?0.033) and twin gestation (p?=?0.089). Feeding hypoxemia correlated with RIAC (p?<?0.001), abnormal cranial ultrasound findings (p?<?0.001), maternal smoking during pregnancy (p?=?0.083), asymmetric intrauterine growth restriction (p?=?0.012) and twin gestation (p?=?0.067). All infants recovered from RIAC in an average of 4.5 (2.0–7.0) d. Fifteen infants recovered from feeding hypoxemia, but 10 infants needed additional assistance and monitoring by nursing until the day of discharge. The day of discharge was day 8.0 (5.0–12.4).

Conclusions: RIAC and feeding hypoxemia are observed among healthy infants, and these infants experience repeated events of prolonged hypoxemia.     

不同胎龄和日龄早产儿心功能变化

目的 探讨不同胎龄早产儿出生后心功能的变化特点及影响因素.方法 早产儿111例,根据胎龄分为28～31+6、32～33+6和34～36+6周组.以足月儿作为对照组(n=50),胎龄为37～41+6周.在生后1周内,平均(4.8±1.4)d,应用SonoSite 180 PLUS彩色多普勒超声仪测定心功能,测量指标包括主动脉瓣峰流速、肺动脉瓣峰流速、心输出量、每搏输出量、左室舒张末期容积、左室收缩末期容积、二、三尖瓣口舒张早期与舒张晚期血流充盈速度比(二尖瓣E/A、三尖瓣E/A)和心率,比较不同胎龄新生儿心功能的变化.另外162例早产儿根据心功能检查日龄分为12 h～,24 h～,72 h～和1周～28 d组,比较不同日龄早产儿心功能变化.采用多元线性回归分析探讨影响心功能的因素.结果 (1)不同胎龄新生儿心功能变化:主动脉瓣峰流速、肺动脉瓣峰流速、左室舒张末期容积、左室收缩末期容积、每搏输出量和心输出量随胎龄增加而增加;在28～31+6、32～33+6和34～36+6周组,二尖瓣E/A分别为1.13±0.17、1.14±0.18和1.13±0.18,三尖瓣E/A分别为0.90±0.16、0.90±0.13和0.90±0.15,均高于胎龄37～41+6周的足月儿(分别为1.28±0.17和1.04±0.20),差异均有统计学意义(P均＜0.05).(2)不同日龄早产儿心功能变化:72 h～和1周～28 d组肺动脉瓣峰流速分别为(79.60±11.22)cm/s和(78.86±13.64)cm/s,高于12 h～组[(72.61±8.56)cm/s];1周～28 d组心率快于其他3组,差异均有统计学意义(P均＜0.05).(3)影响心功能的因素:心输出量与体重和胎龄正相关,r分别=0.55和0.36,P均＜0.05.每搏输出量与体重和胎龄正相关,r分别=0.61和0.52,P均＜0.05.结论 早产儿随胎龄增大,左心室泵功能渐增强,左右心室舒张功能无明显变化.出生72 h后,肺动脉瓣血流速度显著加快.体重和胎龄是影响早产儿心功能的主要因素.

Abstract：

Objective To investigate the features and influence factors of cardiac function in preterm infants.Methods One hundred and eleven preterm infants were divided into three groups according to the gestational age which was 28-31+6,32-33+6 and 34-36+6 weeks respectively.Fifty term-birth infants at gestational age of 37-41+6 weeks were taken as control group.The cardiac function was examined by SonoSite 180 PLUS color Doppler ultrasonic diagnostic apparatus.The parameters of cardiac function included heart rate,peak flow rate of aorta valve orifice (AV),peak flow rate of pulmonary artery valve orifice (PV),cardiac output (CO),stroke volume (SV),left ventricular end diastolic volume (LVEDV),left ventricular end systolic volume (LVESV),the ratio of early (E) and late (A) diastolic velocities of mitral and tricuspid valves (MVE/A,TVE/A).Within one week after delivery,the cardiac function was examined,and the cardiac function of preterm infants with different gestational age were compared.Another 162 preterm infants were divided into four groups according to the time at examination as 12 h-,24 h-,72 h-and 1 week-28 d.The influence factors of cardiac function were determined by multi-factor linear regression analysis.Results The AV,PV,CO,LVEDV,LVESV and SV increased with the increasing of gestational age.MVE/A (1.13±0.17,1.14±0.18,1.13±0.18) and TVE/A (0.90±0.16,0.90±0.13,0.90±0.15) of 28-31+6,32-33+6 and 34-36+6 weeks group were higher than those of control group (1.28±0.17 and 1.04±0.20),respectively (P＜0.05).PV of 72 h-group and 1 week-28 d group were higher than that of 12 h-group [(79.60±11.22) cm/s and (78.86±13.64) cm/s vs (72.61±8.56) cm/s](P＜0.05).The heart rate of 1 week-28 d group was higher than that of other three groups (P＜0.05).Both CO and SV were positively related to body weight and gestational age (r=0.55 and 0.36,0.61and 0.52,respectively,P＜0.05).Conclusions The left ventricular pump function increases with the increasing of gestational age,while the diastolic function of left and right ventricle of preterm infants does not change significantly in the first month of life.The PV of preterm infants significantly increases 72 h after delivery.The body weight and gestational age are important influence factors of cardiac function in preterm infants.     

Cerebral NIRS patterns in late preterm and very preterm infants becoming late preterm

Background: Near Infrared Spectroscopy (NIRS) has been proposed as a useful, noninvasive monitoring technique providing reliable information about central nervous system (CNS) oximetry and function. Recently, brain damage has been reconsidered as a dynamic process evolving over the weeks of gestation. We therefore investigated NIRS cerebral pattern differences between healthy late preterm infants (LPTo) and very preterm infants becoming late preterm (LPT).

Methods: We conducted an observational study in 40 healthy late preterm infants, matched for gestational age at monitoring, of whom 20 where LPTo and 20 LPT. Clinical, diagnostic and laboratory monitoring procedures and cerebral oximetry (crSO₂) and function (cFTOE) were recorded on admission into the study.

Results: No significant differences (p?>?.05, for all) were found between groups regarding clinical, diagnostic or laboratory parameters. Higher crSO₂ and lower cFTOE (p?Conclusions: Our results, showing impaired oximetry and function of CNS in LPT, offer additional support to NIRS parameters as a useful tool for longitudinal CNS monitoring of very preterm infants becoming LPT. Future studies correlating NIRS variables and long-term neurological outcome in LPT are needed to elucidate the concept of dynamic brain damage pathogenesis.     

Evaluation of serum cortisol levels in a relatively large and mature group of ventilated and nonventilated preterm infants with respiratory distress syndrome

Severity of respiratory distress syndrome (RDS) and mechanical ventilation may affect the endogenous cortisol secretion in preterm infants. The aim of this study was to compare the serum cortisol concentrations of a relatively large and mature group of preterm infants with RDS who are ventilated or nonventilated and control preterm infants without RDS. Infants (group I) of comparable gestational ages without RDS served as controls. Infants with RDS who did not need ventilator support and surfactant therapy were considered to have mild RDS (group II). Those requiring mechanical ventilation and surfactant therapy were considered to have severe RDS (group III). Serum cortisol levels were determined after birth and on day 3 of life. The study groups consisted of 79 preterm infants with gestational ages ranging from 31 to 36 weeks, and birthweights ranging from 1086 to 1685 g. All preterm infants showed high cortisol levels after delivery regardless of respiratory distress (group I, n = 25, 34.1 +/- 10.7 microg/dL; group II, n = 23, 33.6 +/- 12.0 microg/dL; and group III, n = 31, 36.4 +/- 12.3 microg/dL). In group III, the cortisol levels (50.8 +/- 16.8 microg/dL) were higher than in group II (40.4 +/- 10.5 microg/dL) and in controls (22.0 +/- 7.2 microg/dL), and the cortisol levels of controls were lower than in group II on day 3 of life. Although the cortisol levels in severe and mild RDS infants increased significantly from their corresponding levels on day 1, they decreased in controls. The cortisol levels on day 3 of life were not significantly different in infants with poor outcome compared with infants with better outcome. Severity of RDS and mechanical ventilation were related to serum cortisol levels of preterm infants. Our study suggests that large and mature preterm infants who are ventilated and/or more severely ill release more cortisol than those less severely ill.     

Update on nutrition for preterm and full-term infants

Child health and development are contingent on sound nutrition during the neonatal period. The nutritional needs of all infants include adequate intake of fluid and energy; a balance among proteins, carbohydrates, and fats; and proper vitamin and mineral intake. Preterm infants have similar nutritional requirements but demand more frequent assessment of nutritional health and ongoing adjustment of nutritional intake throughout the neonatal period to ensure appropriate growth and development. Evidence-based nursing practice calls for an update on the specific nutritional requirements of infants, special nutritional needs of preterm infants, and the most recent changes in the composition of infant formula.     

Neuroimaging and neurodevelopmental outcomes in preterm infants

Imaging of the preterm infant brain has advanced dramatically beyond the earliest era of transillumination. Computed tomography (CT), a crucial innovation during the early 1970s, allowed noninvasive visualization of intracerebral lesions, particularly hemorrhage. The capability to document brain injury in the preterm infant led to better clarification of links to developmental outcomes. With the development of cranial ultrasound (CUS), and more recently, magnetic resonance imaging (MRI), CT is used rarely for imaging the brain of preterm infants. Despite extensive experience with neonatal neuroimaging, significant questions still remain. Substantial controversies exist pertaining to when and how neuroimaging should be performed and how images should be interpreted.