Respiratory water loss and oxygen consumption in newborn infants during phototherapy

Respiratory water loss was measured together with oxygen consumption (VO2) and carbon dioxide production (VCO2) in 11 full-term and eight preterm infants (mean gestational age 34 weeks, range 31-36 weeks) before and during 1 h of phototherapy. The method for determination of respiratory water loss, VO2 and VCO2 was based on an open flow-through system with a mass spectrometer for measurement of gas concentrations. All infants were studied naked in an incubator with an ambient relative humidity of 50% and with a controlled environment with respect to temperature and air velocity. The infants were calm during the measurements. Before phototherapy, in term infants respiratory water loss was 4.4 (SD 0.7) mg/kg min and VO2 5.9 (0.9) ml/kg min and in preterm infants respiratory water loss was 4.7 (0.8) mg/kg min and VO2 6.1 (0.8) ml/kg min. No significant difference was found between values obtained during or after 1 h of phototherapy and those obtained before.     

Long-term variation in oxygen consumption rate in preterm infants

An investigation was made of long-term variation in oxygen consumption rate (VO2) in preterm infants. Four subjects (gestational age 27-34 weeks, postnatal age 17-38 days, weight at study 1.1-2.6 kg) were studied for 5 days each using open-circuit, indirect calorimetry. The mean VO2 for each subject (11.0-11.5 litres/kg/day) was within the reported range. However, the between-subject coefficient of variation during the study (2.1%) was smaller than the mean between-measurement coefficient of variation for daily VO2 (3.8%, range 1.7-6.3%). In addition, the between-measurement coefficient of variation was increased further for measurement intervals of less than 24 h (reaching a mean of 8.3% for 1-hour periods), and a relationship between measurement duration and the precision of estimating VO2 over 3 or 5 days is described. Thus, even 24-hour measurements of VO2 in these preterm infants were less representative of the individual's VO2 over 3 days than the group mean estimate. This finding is of relevance to future studies in this area, particularly those in which short-term measurements of energy expenditure are combined with a nutrient balance study to determine the composition of weight gain, because even small errors in the estimate of total energy expenditure can lead to unacceptably large errors in calculated energy deposition.     

早产儿中性粒细胞活性氧代谢的研究

目的：该研究通过对于不同胎龄新生儿中性粒细胞活性氧代谢水平的检测研究,以了解新生儿中性粒细胞功能发育成熟的过程,并探讨早产儿对于细菌高易感性的部分原因。方法：选择早产儿35例,分为胎龄32周以下和33～36周两组,并选择足月新生儿23例作为对照组。在新生儿出生后取脐静脉血进行体外实验,分别以金黄色葡萄球菌和大肠杆菌刺激诱导呼吸爆发后用超氧阴离子特异性探针氢化溴乙非锭进行细胞内染色,通过流式细胞仪检测中性粒细胞超氧阴离子阳性细胞比率和产生水平;同时对两组不同胎龄早产儿细菌感染实际发生情况进行比较。结果：胎龄32周以下早产儿超氧阴离子阳性中性粒细胞比率与胎龄32周以上早产儿和足月新生儿相比差异有显著性,呈明显低下状态［金黄色葡萄球菌:（79.4±8.6）% vs （89±6.1）% vs （91.3±3.8）%,F＝18.05,P＜0.01;大肠杆菌: （78.2±7.8）% vs （89.3±5.3）% vs （92±4.1）%,F＝28.3, P＜0.01)］;而且阳性率和早产儿胎龄大小密切相关(y＝2.66 x ,P＜0.01);但3组不同胎龄的新生儿活性氧代谢阳性细胞超氧阴离子产生水平之间的差异无显著性。临床观察发现小胎龄早产儿组全身性细菌感染实际发生率高于大胎龄组早产儿。结论：新生儿中性粒细胞细菌诱导活性氧代谢的总体能力直接和新生儿成熟度相关,在胎龄小于32周早产儿中处于明显低下状态,并随着胎龄的增加逐渐成熟。早产儿中性粒细胞活性氧代谢水平的总体低下是导致早产儿细菌感染高易感性的重要原因之一。［中国当代儿科杂志,2007,9（4）：355-357］     

Transcutaneous oxygen tension during nonnutritive sucking in preterm infants

The effects of nonnutritive sucking on transcutaneous oxygen tension, heart rate, and respiratory rate were studied sequentially in 14 sleeping preterm infants breathing room air. Transcutaneous oxygen tension increased during nonnutritive sucking in infants between 32 and 35 weeks postconceptional age, but not in those between 36 and 39 weeks. This response was not associated with a change in respiratory rate or sleep state, although heart rate tended to increase. These data offer further support for the beneficial effects of nonnutritive sucking in preterm infants.     

Respiratory management of extremely preterm infants

Lindner's study of respiratory management of extremely preterm infants, while not providing a definitive answer, demonstrates that many of the smallest infants can be managed in and beyond the delivery room without intubation and without apparent increased early mortality. Conclusion: These novel techniques deserve further evaluation.     

Alterations in cerebral blood flow and oxygen consumption during prolonged hypocarbia

The effect of prolonged (2 h) hypocarbia on cerebral blood flow, oxygen delivery, extraction, and consumption was studied in eight, 1- to 4-day-old piglets. Hyperventilation to PaCO2 less than 20 mm Hg acutely (30 min) decreased cerebral blood flow and oxygen consumption. Cerebral oxygen consumption was subsequently restored via increases in cerebral blood flow and thus, cerebral oxygen delivery. Cerebral oxygen extraction rose from a normocarbic baseline of 50 to 75% with acute hypocarbia and was maintained at this level. The percent decrease in blood flow to the cerebrum was greater than that to other brain regions during hypocarbia.     

Skin bilirubin measurement during phototherapy in preterm and term newborn infants

Background

The few existing studies evaluating the reliability of transcutaneous bilirubin monitoring during phototherapy gave controversial results.

Aims

To evaluate the accuracy of transcutaneous bilirubin measurement in a large population of newborn infants, during phototherapy.

Study design and methods

Total serum bilirubin and transcutaneous bilirubin on patched and unpatched skin areas were simultaneously measured in newborn infants undergoing phototherapy. Transcutaneous measurements were performed with a multiwavelength transcutaneous bilirubinometer (Respironics BiliCheck™). The Passing-Bablok regression and the Bland-Altman plot were used to estimate the relationship between serum and transcutaneous bilirubin.

Results

We studied 364 newborn infants with a mean (SD) gestational age of 34.6 (3) weeks and a mean birth weight of 2371 (805) grams. Total serum bilirubin, patched transcutaneous bilirubin and unpatched transcutaneous bilirubin were similar before phototherapy. After 52 (33) hours of phototherapy, the difference between serum bilirubin and patched transcutaneous bilirubin was 0.2 (3.1) mg/dL (not significant) while the difference between serum bilirubin and unpatched transcutaneous bilirubin was 3.2 (3.0) mg/dL (p < 0.001). Statistical analysis showed a good agreement between serum bilirubin and patched transcutaneous bilirubin, while unpatched transcutaneous bilirubin underestimates serum levels. The difference between patched and unpatched values was significantly lower in preterm than in term infants (2.8 mg/dL vs. 3.6 mg/dL; p < 0.001).

Conclusion

BiliCheck can be safely used for the evaluation of bilirubin levels in newborn infants under phototherapy. Its reliability on patched skin of the forehead is high enough to consistently reduce blood draws and to ascertain when to discontinue phototherapy. Because of the individual variance, any clinical decision has to be taken on the basis of the transcutaneous bilirubin trend more than on a single value.     

Factors affecting the measurement of energy expenditure during energy balance studies in preterm infants

Our objective was to examine factors that affect the accuracy of energy expenditure measurements (EE), when using flow-through indirect calorimetry (IC), to determine the minimum length of time needed to measure 24- and 48-h EE and to compare cross-over and parallel designs as methods of investigation during energy balance collections (EB) in preterm infants. A baby doll manikin was used to determine equilibration times and to compare VCO(2) and VO(2) as measured by flow meter and indirect calorimetry under different study conditions, one of which simulated an EB. "Continuous" EE was measured to determine the minimum length of time needed to accurately reflect 24- and 48-h EE and to compare parallel and cross-over studies as methods of study design in a group of "normal" enterally fed preterm infants. The mean (+/-SD) errors between flow meter and indirect calorimetry determinations for VCO(2) and VO(2) were -1.9 +/- 2.5 and -1.8 +/- 4.3% under conditions that simulated an EB. Cumulative 6-h EE accurately predicted 24- and 48-h EE. Expressed in absolute terms (kcal/d), EE did not change on a day-to-day basis but did increase over the 2-wk study period. Expressed on body weight basis (kcal/kg/d), EE did not change on a day-to-day or week-to-week basis. The variance in EE due to biologic variability; i.e. the parallel design, was approximately 6 times greater than that due to age, weight, and weight gain; i.e. the cross-over design. Indirect calorimetry, therefore, accurately measures EE in conditions simulating an energy balance collection. Six-hour EE determinations are valid estimate of EE during a 48-h balance collection, while cross-over studies may be the preferred method of study design during short-term studies of EE in preterm infants.     

Transcutaneous bilirubin measurement in preterm infants]

Transcutaneous bilirubinometry is an effective screening tool for neonatal jaundice in full-term babies. But its accuracy is not shown yet in preterm infants. METHODOLOGY: We carried out a prospective study in a neonatal intensive care unit. The study included 47 preterm infants. From birth, a transcutaneous bilirubin measurement (BTc) using the BiliCheck was made on the forehead of each newborn every 8 h. Blood sampling for determination of total serum bilirubin (BS) was combined with BTc: 1) if value of BTc was higher than limits values for phototherapy; 2) on the second day of life and 3) 4 hours after cessation of phototherapy. RESULTS: Mean gestational age was 30 week and mean birth weight was 1419 g. We studied 151 pairs of BTc and BS. Mean values obtained by BTc and BS were respectively 160.6+/-50 mumol/L and 190.6+/-61.4 mumol/L. A significant correlation between BTc and BS was found. But the limits of agreement were very wide. The negative predictive value (NPV) of BTc was above 90% in each group of gestational age. DISCUSSION: The need for phototherapy cannot be determined by BTc in preterm infants. But the BTc is reliable when its value is under the limits for phototherapy. CONCLUSION: With a very high incidence of neonatal jaundice (87%) in our cohort, a value of BTc under the limits for phototherapy has a good NPV in preterm infants.     

Postnatal urinary conductance measurement in preterm infants

The aim of this study was to determine whether serial urinary conductance measurements can be used to estimate reliably the end of the transition period of negative sodium balance in preterm infants. The relationship between urine conductance, measured by a conductance meter, and urine sodium concentration was determined in 109 pooled samples of urine obtained from 14 preterm infants during the transitional period of fluid balance. It was shown by linear regression analysis that urine sodium concentration (mmol l -1 ) = 0.78 ×urine conductance -1.25. Urine sodium concentrations derived from the above formula were concordant with urine sodium measured directly when used to calculate daily sodium balance in all 14 infants.

Conclusion: Urine conductance can be accurately measured at the cotside by neonatal nurses and used to identify the timing of the postnatal transition from negative to positive sodium balance in preterm infants. These findings can help in making decisions on the introduction of postnatal sodium administration to preterm infants.     

Postdischarge formula consumption in infants born preterm.

In 31 infants born preterm and formula fed ad libitum, all milk intake was weighed from hospital discharge to nine months post-term. Mean daily milk intake was high, reaching 230 g/kg before four weeks post-term and was still over 150 g/kg beyond six months. Five of the 31 infants (16%) consumed 300-350 g/kg; 50% 'voluntarily' consumed more than upper recommended limits for energy intake and 35% did so for protein intake.     

Click-evoked oto-acoustic emission measurement in preterm infants

Click-evoked oto-acoustic emissions (CEOAE) are acoustic responses produced by the inner ear, reflecting functional auditory integrity. We studied both the success rate of the CEOAE method and the CEOAE presence in preterm infants during their stay at the Neonatal Intensive Care Unit (NICU), by analysis of the results of longitudinal CEOAE measurements in 19 preterm infants. The CEOAE method proved to be feasible in the majority of the population under study; the CEOAE measurement failed in 8% of the total of 226 attempts. Within the range of 30–40 weeks post-conceptional age (PCA) the CEOAE presence increased from about 50% to 80%. These results show the possible clinical application of CEOAE in a NICU for the monitoring of cochlear function during treatment of preterm infants. Conclusion Bedside CEOAE measurement in preterm infants in a NICU is feasible at a PCA as low as 30 weeks. Received: 4 November 1997 and in revised form: 3 February 1998 / Accepted: 3 March 1998     

早产儿呼吸窘迫综合征的呼吸支持策略及研究进展

新生儿呼吸窘迫综合征（respiratory distress syndrome,RDS）多见于早产儿,胎龄越小,发病率越高。近年的大规模随机对照研究突出了产房内开始的持续气道正压通气（continuous positive airway pressure,CPAP）在RDS防治中的重要作用,对于生后有自主呼吸的早产儿,产房内应用CPAP优于气管插管,而顶防性应用肺表面活性物质（pulmonary surfactant,PS）不再具有优势。2013版欧洲新生儿RDS防治指南推荐有患RDS风险的早产儿生后均应立即接受CPAP支持,初设呼气末正压至少6cmH2O（1cmn20=0．098kPa）;对于患RDS的早产儿,最理想的处理是生后CPAP以及早期解救性PS应用。而需要气管插管的早产儿应尽早接受PS替代治疗。不能耐受CPAP的患儿更换通气模式为无创正压通气可能降低拔管失败率。目前有多种策略来缩短机械通气时间并增加无创通气的成功率。患RDS的极早产儿应常规接受咖啡因治疗以提高撤机成功率,并降低支气管肺发育不良的发生率。生后1～2周后仍不能脱离呼吸机者,需接受小剂量递减地塞米松治疗,但应避免生后1周内应用地塞米松以及较大剂量应用。