Determinants of visual evoked potentials in preterm infants

The latency and amplitude of N1, the first negative peak of single flash visual evoked cortical potentials (VEP) were evaluated in 86 preterm infants (25-34 weeks of gestation), investigated during the first day of life. All infants were regarded stable at the time of investigation and none had experienced severe asphyxia. Both the VEP latency and amplitude were inversely related to gestational age. When latency was corrected for age it was longer in boys than in girls. Age corrected VEP amplitude was inversely related to head circumference, umbilical cord pH and EEG activity. There was no difference between VEP parameters in asymmetrically growth retardated infants compared to those with normal growth. Administration of dexamethasone to the mother before delivery, mode of delivery, presence of hyaline membrane disease, mode of assisted ventilation or imminent development of periintraventricular haemorrhage did not affect the VEP.     

Identification of sensory neural hearing loss in very preterm infants by brainstem auditory evoked potentials.

Brainstem auditory evoked potentials were recorded in 117 newborn infants of less than 33 weeks of gestation. The potentials were absent in 10 infants (bilaterally in eight and unilaterally in two) and present in 107. By 1 year of age nine of the 10 infants with absent brainstem auditory evoked potentials were shown to have sensory neural hearing loss and required hearing aids: the remaining infant had secretory otitis media. None of the 107 infants whose auditory evoked potentials were present were found to have sensory neural hearing loss but 13 had secretory otitis media. Measurement of brainstem auditory evoked potentials is an accurate method of identifying sensory neural hearing loss in very preterm infants.     

Somatosensory evoked potentials in neonatal jaundice

Somatosensory evoked potentials (SEPs) were studied in jaundiced and normal neonates on the day the highest bilirubin values were reached, 2-3 days later, and at five weeks. During the first week three groups were formed according to peak bilirubin values: A: greater than or equal to 250 mumol/l (n = 20), B: 125-250 mumol/l (n = 6), C: less than 125 mumol/l or no jaundice (n = 19). At five weeks 10 infants of group A were reinvestigated, together with 17 controls. Cervical (N13) and scalp SEPs (N19) were recorded with a variable number of stimuli. The SEPs of group B and C did not differ from each other. In group A the N13 peak latencies were within the range of group C at the first investigation, but prolonged at the second and third. The cortical components were prolonged at the first investigation, improved but still prolonged at the second, while the N19 peak latency was still prolonged at the third investigation. The central conduction time (CCT) correlated positively with the bilirubin level. Since a rapid decrease in the N19 amplitude was found for all groups from 25 to 100 stimuli, recordings should be done with a low number of stimuli (less than 100). Our findings indicate that both the periferal and the central components of the SEPs in the neonatal period are delayed by jaundice and that full recovery is not obtained at five weeks. The non-invasive SEP technique can be used as a daily monitor of the effect of bilirubin on the CNS.     

Cortical visual evoked potentials in very low birthweight premature infants

OBJECTIVES: To compare the age of onset of the pattern orientation reversal visual evoked potential (OR-VEP) in a group of very low birthweight (VLBW) premature infants with term infants matched for postconceptual age at testing. The OR-VEP measure is used as an indicator of visual cortical functioning because of the specificity of cortical neurones in showing sensitivity to changes of slant or orientation. DESIGN: Results are given for 24 VLBW infants, born at 24-32 weeks gestation weighing less than 1500 g, and 31 infants born at term. The steady state evoked potential to a grating pattern reversing in orientation (between 45 degrees and 135 degrees) at 4 reversals/second and 8 reversals/second was recorded. RESULTS: The VLBW infants with normal neonatal ultrasound results (and normal neurological outcome at 3 years of age) showed a significant OR-VEP with a similar postnatal time course to the term infants. Four premature infants, showing appreciable abnormalities on ultrasound examination, did not show normal onset of the OR-VEP, and all had an abnormal neurological outcome. CONCLUSIONS: This result can be taken to indicate that the onset of cortical function is similar in healthy preterm infants to term infants. The visual development of the premature infants was neither accelerated nor delayed as a result of their extra visual experience. The OR-VEP can be used as a prognostic indicator of early brain development alongside other neurological measures. It may also be a very early indicator of later neurological outcome.     

Vitamin C supplementation in very preterm infants: a randomised controlled trial

OBJECTIVE: To determine whether regulating vitamin C (ascorbic acid: AA) intake to achieve higher or lower plasma concentrations was associated with improved clinical outcome. DESIGN: A double blind, randomised controlled trial. SETTING: Neonatal intensive care unit at Christchurch Women's Hospital. PATIENTS: Infants with birth weight <1500 g or gestation <32 weeks, admitted to the unit within 48 hours of birth. INTERVENTION: Infants were randomised to one of three protocols with regard to AA supplementation for the first 28 days of life: group LL received low supplementation throughout; group LH received low until day 10 and then high: group HH received high throughout. MAIN OUTCOME MEASURES: Primary outcome measures were oxygen requirement at 28 days and 36 weeks postmenstrual age, total days supplemental oxygen, and retinopathy of prematurity. AA concentrations were measured at study entry (day 2), and days 10, 21, and 28. RESULTS: A total of 119 infants were enrolled over 24 months (mean gestation 28.4 weeks; birth weight 1161 g). Six infants died, and these had significantly higher AA concentrations before randomisation than surviving infants (116 micromol/l (95% confidence interval 90 to 142) v 51 micromol/l (45 to 58), p<0.0001). There were no significant differences in primary outcomes between the groups. However, the proportion of surviving infants with an oxygen requirement at 36 weeks postmenstrual age in group HH (19%) was half that in group LL (41%) (p=0.06). CONCLUSIONS: In a randomised controlled trial, no significant benefits or harmful effects were associated with treatment allocation to higher or lower AA supplementation throughout the first 28 days of life.     

Erythropoietin in very preterm infants

Three neonates (a male and two females of gestational ages 27, 27 and 29 weeks with birthweight 985,660 and 1130 g), born to parents who are Jehovah's Witnesses, were admitted to our neonatal intensive care unit over a 2 month period in 1992. Human recombinant erythropoietin (rHuEpo, 200 u/kg sc. on alternate days for 6-8 weeks) was started early in conjunction with strict control of blood sampling in an attempt to avoid the need for blood transfusion. The lowest haemoglobin recorded was 95 g/L at 35 days of age in the first infant. The amount of blood withdrawn for sampling was 21.4 mL, 20.7 mL and 5.5 mL, respectively. All were discharged near their expected birthdate, never having received a blood transfusion in the Nursery. It is possible to manage sick, very preterm, very low birthweight neonates in a neonatal intensive care setting without the use of blood transfusions by the early use of rHuEpo in conjunction with strict control of blood sampling.     

Effect of aminophylline on brain stem auditory evoked potentials in preterm infants.

To determine the neurophysiological effects of aminophylline on apnoea of prematurity, the brain stem auditory evoked potentials (BAEPs) of 30 apnoeic infants and 34 age matched controls were evaluated and compared. After six days of treatment with aminophylline, the brain stem conduction time (interpeak latency of I-V) in apnoeic infants decreased compared with controls of a similar postconceptional age. The mean latencies of the peaks and interpeaks of all waves except wave I were significantly lower in the apnoeic infants after than before receiving aminophylline. No significant differences were found in the latencies of BAEPs between the apnoeic infants who responded and those who did not respond to aminophylline treatment, however. These results suggest that aminophylline may enhance conduction along central auditory pathways and stimulate the regulatory effect on the respiratory centre of the brain stem.     

早产儿在不同刺激速率下的脑干听觉诱发电位变化

目的：早产儿的脑干功能发育与足月儿是否存在差异,国外的研究报道并不一致,该文通过分析不同刺激速率下的脑干听觉诱发电位,比较早产儿与足月儿的脑干功能发育状态及增加刺激速率在检测脑干功能中的作用。方法：早产儿组30例,无围生期及新生儿期合并症;足月儿组38例,为健康足月儿。两组于胎龄37～42周时进行脑干听觉诱发电位检查,声刺激速率为21.1次/s、51.1次/s和91.1次/s,分析Ⅰ,Ⅲ,Ⅴ波的潜伏期和振幅,ⅠⅢ,ⅢⅤ,ⅠⅤ峰间期以及ⅢⅤ/ⅠⅢ峰间期比值。结果：在60dBnHL刺激强度下,随刺激速率增加,两组中Ⅰ,Ⅲ,Ⅴ各波的潜伏期及峰间期均逐渐延长,振幅逐渐下降,潜伏期及峰间期与刺激速率成正相关(P<0.01),振幅与速率成负相关(P<0.01)。两组比较,各频率ⅠⅤ峰间期均无差异,但随刺激速率增高,早产儿组ⅠⅢ峰间期相对缩短(P<0.05)、ⅢⅤ峰间期相对延长(P<0.01),ⅢⅤ/ⅠⅢ峰间期比值增大(P<0.001)。两组振幅无明显差别。结论：早产儿脑干听觉通路的近外周部分较近中枢部分提前发育;提高刺激速率有助于发现更多的神经生理变化,提高脑干听觉诱发电位的诊断价值。     

先天性马蹄内翻足患儿的体感觉诱发电位以及神经电图检测

目的通过对神经电图以及体感觉诱发电位测定外周向中枢传导的异常并寻找神经病变的位点，探讨先天性马蹄内翻足（CCF）神经电生理异常与马蹄足畸形的关系。方法应用Nicolet公司VikingⅣ肌电图诱发电位仪对手术前的CCF婴幼）L（2000年10月～2003年12月）48例（63个病足）和对照组（9个正常足）进行检测。检测包括下肢胫神经、腓总神经、腓肠神经及H反射。体感觉诱发电位分别于胭窝、腰4、颈7以及头部左右中央进行记录。结果63足中神经电生理异常的有48足（76．2％）。体感觉诱发电位检测显示39个病足（61．9％）存在异常，其中腰．以下异常24足，神经电图检测显示34个病足结果异常（54．0％），H反射异常20足（31．7％）。三度畸形22足全部存在神经电生理异常，二度畸形39足中26足存在异常。结论76．2％先天性马蹄足患儿存在不同类型及不同程度的神经电生理异常，此异常多存在于脊髓腰4以下节段。通过体感觉诱发电位和神经电图检测显示，神经电生理异常与CCF畸形严重程度相关。     

The role of cortical evoked responses in predicting neuromotor outcome in very preterm infants

To explore the role of posterior tibial somatosensory evoked potentials (SSEP) and flash visual evoked potentials (VEP) in the early prediction of functional brain injury, 93 infants of less than 32 weeks gestation at birth were studied. Neuromotor outcome was defined by clinical examination at the age of 2 years. SSEP, VEP and cerebral ultrasound were compared as predictors of neuromotor outcome. Posterior tibial SSEP were the most accurate single method of predicting neuromotor abnormalities with a 83% positive predictive power for cerebral palsy and a 100% predictive power for abnormal neurology, compared to 17% and 40% for cerebral ultrasound and 38% and 85% for VEP respectively. When SSEP and VEP results were concordant, the positive predictive power for cerebral palsy and abnormal neurology was 100%. Our results suggest that posterior tibial SSEP and VEP are accurate tools in the prediction of outcome in very preterm infants.     

Somatosensory evoked potentials in children with severe head trauma

We evaluated the predictive value of somatosensory evoked potentials (SEP) in a series of children with severe traumatic brain injury (TBI). The prospective clinical investigation was performed in a Level I paediatric trauma centre. We included 26 consecutive comatose paediatric patients aged from 1 month to 17 years (median age 11 years) following severe TBI (initial Glasgow Coma Score (GCS) 8 or below). Besides SEP recordings, the intracranial pressure and the results of an initial cranial CT scan were filed. The Glasgow Outcome Scale (GOS) was used to assess outcome at discharge. Thirteen children had normal SEP measurements, three patients had abnormal SEP recordings and a cortical response was bilaterally absent in ten children. Out of 26 children, 10 died whereas two remained in a persistent vegetative state. Only one child suffered from significant neurological deficits (GOS 3) at discharge. Seven patients survived with a GOS of 4 and six children survived without neurological impairment (GOS 5). Normal SEP indicated a favourable outcome in most children but did not rule out the occurrence of death, while absence of SEP was related to unfavourable outcome in all cases. Conclusion: Measurement of somatosensory evoked potentials provides valuable data for determining the prognosis at early coma stages. Our data show that an unfavourable outcome can be predicted with higher precision than a favourable outcome.     

Enteral yeast-selenium supplementation in preterm infants

AIM—To study the bioavailability of selenium enriched yeast in preterm infants living in a low selenium area (Hungary).
METHODS—Thirty six preterm infants were randomly assigned to two groups at birth with respect to selenium supplementation. In the supplemented group (n=18) infants received 4.8 mg of selenium enriched yeast containing 5 µg selenium daily.
RESULTS—In the supplemented group the serum selenium concentration increased from 36.1(±12.8) µg/l to 43.5 (7.9) µg/l and in the non-supplemented group it decreased from 34.4 (20.4) µg/l to 26.1 (16.6) µg/l from birth in two weeks. No complications or side effects as a result of supplementation were observed.
CONCLUSIONS—Selenium enriched yeast is a safe and an effective form of short term enteral selenium supplementation for preterm infants.

     

Rehospitalization of very preterm infants

Rehospitalization rates of very preterm infants because of reasons that are related to neonatal morbidity states can be decreased with further improvement of neonatal intensive care provided.

Conclusion: Analysis of rehospitalization data should be included in follow-up programmes as a contribution to the development of strategies to improve neonatal care and the ultimate outcome for very-low-birthweight infants.     

Thyroid function in very preterm infants

Indices of thyroid function were measured in 108 infants born at 23-31 weeks gestation, after birth, at 24 and 72 h, and at 1, 3, 4, 5 and 6 weeks of age. This group was characterised by low serum thyroxine (T4), normal thyroid stimulating hormone (TSH), low-normal thyroid binding globulin (TBG), low free thyroxine index (FTI) and low triiodothyronine (T3). The incidence of hypothyroxinaemia defined as a serum T4 value of less than 65 nmol/l was 58% after birth, increasing to 84% at 1 week, after which there was progressive reduction to 36% by 6 weeks of age. Mean T4 values were inversely proportional to gestational age during this study period. Infants of 23-28 weeks gestation had significantly lower T4, TBG, FTI and T3 values compared to those of 29-31 weeks gestation. Infants who had hyaline membrane disease (HMD) had significantly lower T4 and FTI values compared to those without HMD for up to 3 weeks of age. Similar differences were found between deaths and survivors in the first week after birth. This study suggests that there is increasing delay in maturation of the hypothalamic-pituitary-thyroid axis control with increasing prematurity. In addition, the data suggest that infants who were extremely preterm or those with HMD had worse and more persistent abnormalities of thyroid function secondary to their illness and metabolic stress. The significance of our findings, in particular that of prolonged hypothyroxinaemia, is uncertain. The role of thyroid replacement therapy in these very preterm infants therefore need to be assessed with a randomised clinical trial.     

Visual evoked potentials and dietary long chain polyunsaturated fatty acids in preterm infants.

The influence of dietary long chain polyunsaturated fatty acid (LCP) supply, and especially of docosahexaenoic acid (DHA), on evoked potential maturation, was studied in 58 healthy preterm infants using flash visual evoked potentials (VEPs), flash electroretinography (ERG), and brainstem acoustic evoked potentials (BAEPs) at 52 weeks of postconceptional age. At the same time, the fatty acid composition of red blood cell membranes was examined. The infants were fed on breast milk (n = 12), a preterm formula supplemented with LCP (PF-LCP) (n = 21), or a traditional preterm formula (PF) (n = 25). In the breast milk and PF-LCP groups the morphology and latencies of the waves that reflect the visual projecting system were similar; in the PF group the morphology was quite different and the wave latencies were significantly longer. This could mean that the maturation pattern of VEPs in preterm infants who did not receive LCP was slower. Moreover, a higher level of erythrocyte LCP, especially DHA, was found in breast milk and PF-LCP groups compared with the PF group. ERG and BAEP recordings were the same in all three groups. These results suggest that a well balanced LCP supplement in preterm formulas can positively influence the maturation of visual evoked potentials in preterm infants when breast milk is not available.     

Improvement in auditory and visual evoked potentials in jaundiced preterm infants after exchange transfusion.

Two preterm infants with peak serum bilirubin concentrations of 270 mumol/l and 200 mumol/l, respectively showed improvement in the wave peak latencies of the auditory and visual evoked potentials after exchange transfusion. The implications of this observation and the use of evoked potential recording in neonatal jaundice are discussed.     

Adrenal function in sick very preterm infants

Some very preterm neonates admitted to the neonatal intensive care unit show circulatory and respiratory problems that improve after administration of steroids. It is unclear whether these symptoms could be caused by adrenal insufficiency. The objective of our study was to investigate the cortisol levels and the cortisol release from the adrenals after ACTH in very preterm infants with and without severe illness and to find whether a relation exists between adrenal function and outcome. An ACTH test (0.5 microg) was performed on d 4 in 21 very preterm infants (gestational age, 25.6-29.6 wk; birth weight, 485-1265 g). Baseline cortisol and 17-hydroxyprogesterone (17OHP) levels and the cortisol levels 30, 60, and 120 min after ACTH administration were measured. The Score for Neonatal Acute Physiology was used to measure illness severity. All infants showed an increase in cortisol levels after ACTH, but the cortisol levels were significantly lower in the ventilated more severely ill infants. After adjusting for birth weight and gestational age, the mean baseline cortisol levels and cortisol/17OHP ratios were significantly lower and the 17OHP levels significantly higher in the ventilated infants compared with the nonventilated infants. Patients with an adverse outcome had significantly lower baseline cortisol/17OHP ratios and 60-min cortisol levels during ACTH testing (p = 0.002 and p = 0.03, respectively). These data suggest an insufficient adrenal response to stress in sick ventilated very preterm infants with gestational ages younger than 30 wk compared with nonventilated less sick preterm infants. Further studies are required to investigate whether supplementation with physiologic doses of hydrocortisone may benefit the outcome.     

Recurrent wheezing in very preterm infants.

AIMS: To document the prevalence of, and identify risk factors for, recurrent wheezing treated with bronchodilators in the first year of life. METHODS: Parental history and neonatal data were collected prospectively in a regional cohort of very preterm infants (< 33 weeks). Data on maternal smoking, siblings at home, breast feeding, respiratory symptoms, and hospital re-admissions were documented at 12 months. RESULTS: Outcome data were available for 525/560 (95%) of survivors. The incidence of recurrent wheeze was 76/525 (14.5%) in very preterm infants and 20/657 (3%) in a cohort of term newborns. Significant risk factors for recurrent wheeze in very preterm infants were parental history of asthma, maternal smoking, siblings at home, neonatal oxygen supplementation at 28 days, 36, and 40 weeks of gestation. CONCLUSIONS: Wheezing respiratory illnesses are common in very preterm infants. The factors involved are similar to those in more mature infants, with the addition of immaturity and neonatal lung injury.     

Human milk supplementation for preterm infants

Nutrition support of the premature infant must be designed to compensate for metabolic and gastrointestinal immaturity, immunologic compromise, and associated medical conditions. The beneficial effects of human milk extend to the feeding of premature infants. However, nutritional concerns arise because the quantity of nutrients in human milk may not meet the great nutrient needs of the premature infant born weighing less than 1500 g. Human milk fortifiers are available to provide optimum nutrition. This review summarizes the benefits and limitations of human milk for the premature infant.