An outbreak of meticillin-resistant Staphylococcus aureus colonization in a neonatal intensive care unit: use of a case-control study to investigate and control it and lessons learnt.

AIM: To describe the investigation and management of a meticillin-resistant Staphylococcus aureus (MRSA) outbreak on a neonatal intensive care unit (NICU) and the lessons learnt. METHODS: This was an outbreak report and case-control study conducted in a 40-cot NICU in a tertiary referral hospital and included all infants colonized/infected with gentamicin-resistant MRSA. INTERVENTION: Standard infection-control measures including segregation of infants, barrier precautions, enhanced cleaning, assessment of staff practice including hand hygiene, and increased MRSA screening of infants were implemented. Continued MRSA acquisitions led to screening of all NICU staff. A case-control study was performed to assess staff contact with colonized babies and inform the management of the outbreak. FINDINGS: Eight infants were colonized with MRSA (spa type t2068), one of whom subsequently developed an MRSA bacteraemia. MRSA colonization was significantly associated with lower gestational age; lower birthweight and with being a twin. Three nurses were MRSA colonized but only one nurse (45) was colonized with MRSA spa type t2068. Multivariable logistic regression analysis identified being cared for by nurse 45 as an independent risk factor for MRSA colonization. CONCLUSIONS: Lack of accurate recording of which nurses looked after which infants (and when) made identification of the risk posed by being cared for by particular nurses difficult. If this had been clearer, it may have enabled earlier identification of the colonized nurse, avoiding subsequent cases. This study highlights the benefit of using a case-control study, which showed that most nurses had no association with colonized infants.

Pubertal growth in young adult survivors of childhood leukemia.

PURPOSE: To determine the effect of cranial irradiation (18 Gy and 24 Gy) on pubertal growth in young adult survivors of childhood acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: Final height (FH) and pubertal growth were retrospectively examined in 142 young adult survivors of childhood ALL. All were in first remission and had received either 18 or 24 Gy of cranial irradiation. Eighty-four children (48 girls) were treated with 24 Gy and 58 (35 girls) with 18 Gy. None had received either testicular or spinal irradiation. Timing and duration of puberty were studied in 110 patients. RESULTS: Significant reduction in height standard deviation score (SDS) from diagnosis to FH was seen in both sexes and in both dose groups. In girls, in both dose groups, mean age at peak height velocity (PHV) and mean age at menarche occurred significantly earlier than in the normal population. In boys, there was a normal timing of PHV. The amplitude of PHV was significantly reduced in both sexes and in both dose groups. Parameters of pubertal duration (PHV to menarche, PHV to FH, and menarche to FH) were not significantly different from normal population values. CONCLUSION: In conclusion, puberty occurred early in girls, but not in boys. Amplitude of PHV was reduced in both sexes, with no reduction in the duration of puberty. It is likely that disturbances of both timing and quality of growth during puberty contribute to the loss of standing height and body disproportion seen in these children.

The continuous glucose monitoring sensor in neonatal intensive care.

OBJECTIVE: To determine the feasibility of continuous glucose monitoring in the very low birthweight baby requiring intensive care, as these infants are known to be at high risk of abnormalities of glucose control. METHOD: Sixteen babies were studied from within 24 hours of delivery and for up to seven days. RESULTS: The subcutaneous glucose sensors were well tolerated and readings were comparable to those on near patient whole blood monitoring devices. CONCLUSION: Continuous glucose monitoring is practical in neonates, giving detailed information about glucose control.

Cranial irradiation and early puberty.

Low doses of cranial irradiation (18-24 gray) employed in the management of acute lymphoblastic leukemia may cause early or precocious puberty, predominantly in girls. To determine whether this sexual dichotomy exists at higher irradiation doses (25-47 gray), the onset of puberty was identified in 46 GH-deficient children (30 males) previously irradiated for a brain tumor not involving the hypothalamic-pituitary axis and compared with the normal pubertal standards of Marshall and Tanner. Age at irradiation was at least 2 SD below the mean age of pubertal onset in normal children. There was a significant linear association between age at irradiation and age at onset of puberty. The onset of puberty occurred at an early age in both sexes (mean, 8.51 yr in girls and 9.21 yr in boys plus 0.29 yr for every year of age at irradiation). For example, the estimated age at onset of puberty in a boy irradiated at 2 yr of age would be 9.79 yr, and that for a boy irradiated at 9 yr of age would be 11.82 yr. In the context of GH deficiency, which is usually associated with a delay in the onset of puberty, this is abnormal. At each age of irradiation, the estimated age at the onset of puberty was approximately 0.7 yr earlier in girls than boys. A similar trend was seen for bone age, which was abnormally early at the time of pubertal onset (mean, 7.39 yr in girls and 8.66 yr in boys plus 0.25 yr for every year of age at the time of irradiation). At the doses of irradiation employed in the treatment of brain tumors, radiation-induced early puberty is not restricted to girls. The clinical consequence of early puberty in the management of poor growth associated with radiation-induced GH deficiency is to foreshorten the time available for treatment with GH.

Hypoglycemia and resistance to ketoacidosis in a subject without functional insulin receptors.

Humans with congenital absence of the islets of Langerhans and mice rendered null for the insulin receptor rapidly develop severe hyperglycemia and ketoacidosis and, if untreated, die in the early neonatal period. In contrast, children with homozygous or compound heterozygous mutations of the insulin receptor gene, although hyperglycemic postprandially, survive for many months without developing ketoacidosis. Paradoxically, they often develop hypoglycemia. The rarity of the condition and the difficulties of undertaking metabolic studies in ill infants have limited the physiological information that might explain the clinical features. We studied a boy with Donohue's syndrome who represents a further example of the null phenotype, with two different and novel nonsense mutations in the alpha-subunit of the receptor. He survived for 8 months without developing ketoacidosis, and fasting hypoglycemia was a frequent problem. Despite the complete absence of insulin receptors, evidence for persistent insulin-like effects on fat and liver was seen; fasting plasma beta-hydroxybutyrate and nonesterified fatty acid levels were low, fell further during the early postprandial period, and failed to rise in response to hypoglycemia. The inverse relationships between plasma insulin and insulin-like growth factor-binding protein-1 levels were maintained, suggesting persistent hepatic effects of insulin. GH levels measured over a 6.5-h period were low throughout. Thus, the differences between congenital insulin deficiency vs. insulin receptor deficiency in humans may be explained by persistent insulinomimetic activity of the grossly elevated plasma insulin presumably being mediated through the type 1 insulin-like growth factor receptor. As GH plays a critical role in the regulation of ketogenesis during insulinopenia in humans, but not in rodents, this may contribute to the distinct phenotype of human vs. mouse insulin receptor knockouts.

Insulin, insulin-like growth factor I (IGF-I), IGF-binding protein-1, growth hormone, and feeding in the newborn.

The relationship between GH, insulin-like growth factor I (IGF-I), IGF-binding protein-1 (IGFBP-1), and insulin may be critical to the understanding of variation in early growth, especially in the small for gestational age (SGA) baby. To investigate these relationships, we have undertaken 12-h hormone profiles in 26 babies (13 SGA) at a median of 4.5 days of age. GH levels were measured every 10 min; insulin and IGFBP-1 were measured every 20 min. Mean levels of these hormones and IGF-I levels (from a single sample) were related to size at birth. The GH data were analyzed by Pulsar and time series analysis to characterize hormone pulsatility and relationship with feeds. IGF-I levels correlated with birth weight and length (r2 = 0.47; P = 0.004, and r2 = 0.5; P = 0.0005, respectively, after allowing for gestation), whereas mean GH levels were negatively related to birth size (r2 = -0.18; P = 0.04 and r2 = -0.2; P = 0.03 for weight and length, respectively). No direct relationship between mean GH levels and IGF-I was identified. IGF-I levels were higher in appropriate for gestational age (AGA; mean +/- SD, 82+/-61 ng/mL) than in SGA (34+/-22 ng/mL; P = 0.03) babies. Baseline (mean +/- SD, 25.9+/-11.9), mean (33.9+/-14.0), and peak (45.0+/-18.1 microg/L) GH levels were higher in SGA than in AGA babies [17.1+/-8.2 (P = 0.04), 22.5+/-10.4 (P = 0.03), and 30.7+/-15.4 microg/L (P = 0.04), respectively]. Mean IGFBP-1 levels were also higher in SGA than AGA babies (157.4+/-90.7 vs. 62.7+/-43.8 ng/mL; P = 0.01). A positive correlation was identified between changes in insulin and coincident pulses of GH (r = 0.147; P < 0.01), whereas there was an inverse relationship between insulin and IGFBP-1, with a lag time 120 min (r = -0.33; P < 0.0001). In conclusion, these studies indicate that the GH-IGF-I axis is closely related to feeding in the newborn. In SGA babies, low IGF-I and elevated IGFBP-1 reflect the slow growth, but elevated GH and rapid GH pulsatility may be a signal for lipolysis.

Effect of radiation on the human reproductive system.

Irradiation may have a profound effect on reproductive function. The schedule of the delivered irradiation (total dose, number of fractions, and duration) is an important determinant of the radiobiological effect on the tissues involved and varies among different tissues and organs. Irradiation to the central nervous system may affect the timing of the onset of puberty, result in hyperprolactinemia, or cause gonadotropin deficiency if the hypothalamic-pituitary axis is involved in the radiation field. Direct irradiation to the testis will, in lower doses, affect the germinal epithelium: doses of irradiation greater than 0.35 Gy cause aspermia, which may be reversible. The time taken for recovery increases with larger doses; however, with doses in excess of 2 Gy aspermia may be permanent. At higher radiation doses (> 15 Gy), Leydig cell function will also be affected. In addition to radiation dose, the vulnerability of the testis is dependent on the age at irradiation and the pubertal status of the male. In the female, the response of the ovary to the effects of irradiation varies with age as well as dose, and separation of ovarian dysfunction into hormonal and fertility effects is not clearcut. An ovarian dose of 4 Gy may cause a 30% incidence of sterility in young women, but 100% sterility in women over 40 years of age. Pelvic irradiation may also have a profound effect on the uterus, with arrested growth in the prepubertal girl, and failure of uterine expansion during pregnancy with subsequent miscarriages and premature labor.

Neonatal thyroid disorders.

Hypothyroxinaemia, which is common in the preterm infant, and thyrotoxicosis, which is rare, are important neonatal thyroid disorders. Their causes and treatment are discussed.

Effect of chemotherapy on growth.

Growth restriction has been demonstrated clearly following the treatment of childhood malignancies, even in the absence of irradiation to the hypothalamic-pituitary axis. The use of CT and spinal irradiation in the original treatment of brain tumours has a marked effect on growth. This effect is most profound in children who have received both treatments and cannot be overcome using GH therapy at conventional doses.

Growth hormone and tumour recurrence.

OBJECTIVE: To determine whether using growth hormone to treat radiation induced growth hormone deficiency causes tumour recurrence. DESIGN: Comparison of tumour recurrence rates in children treated with growth hormone for radiation induced deficiency and an untreated population. Computed tomograms from children with brain tumours were reviewed when starting growth hormone and subsequently. SETTING: North West region. PATIENTS: 207 children treated for brain tumour, 47 of whom received growth hormone and 161 children with acute lymphoblastic leukaemia 15 of whom received growth hormone. MAIN OUTCOME MEASURES: Tumour recurrence and changes in appearances on computed tomography. RESULTS: Among children with brain tumour, five (11%) who received growth hormone had recurrences compared with 42 (26%) who did not receive growth hormone. Also adjusting for other variables that might affect tumour recurrence the estimated relative risk of recurrence was 0.82 (95% confidence interval 0.28 to 2.37). The only child with acute lymphoblastic leukaemia who relapsed while taking growth hormone had relapsed previously before starting treatment. Two of the five children with brain tumours who relapsed had abnormal appearances on computed tomography when growth hormone was started. 14 other children who remained relapse free and had follow up computed tomography showed no deterioration in radiological appearance during treatment. CONCLUSIONS: In this population growth hormone did not increase the risk of tumour recurrence but continued surveillance is essential. Abnormal results on computed tomography are not a contraindication to treatment with growth hormone.

Validation of the continuous glucose monitoring sensor in preterm infants.

OBJECTIVE: Recent studies have highlighted the need for improved methods of monitoring glucose control in intensive care to reduce hyperglycaemia, without increasing the risk of hypoglycaemia. Continuous glucose monitoring is increasingly used in children with diabetes, but there are little data regarding its use in the preterm infant, particularly at extremes of glucose levels and over prolonged periods. This study aimed to assess the accuracy of the continuous glucose monitoring sensor (CGMS) across the glucose profile, and to determine whether there was any deterioration over a 7 day period. DESIGN: Prospectively collected CGMS data from the NIRTURE Trial was compared with the data obtained simultaneously using point of care glucose monitors. SETTING: An international multicentre randomised controlled trial. PATIENTS: One hundred and eighty-eight very low birth weight control infants. OUTCOME MEASURES: Optimal accuracy, performance goals (American Diabetes Association consensus), Bland Altman, Error Grid analyses and accuracy. RESULTS: The mean (SD) duration of CGMS recordings was 156.18 (29) h (6.5 days), with a total of 5207 paired glucose levels. CGMS data correlated well with point of care devices (r=0.94), with minimal bias. It met the Clarke Error Grid and Consensus Grid criteria for clinical significance. Accuracy of single readings to detect set thresholds of hypoglycaemia, or hyperglycaemia was poor. There was no deterioration over time from insertion. CONCLUSIONS: CGMS can provide information on trends in glucose control, and guidance on the need for blood glucose assessment. This highlights the potential use of CGMS in optimising glucose control in preterm infants.

Management of hyperglycaemia in the preterm infant.

In the fetus, the predominant energy supply is glucose transported across the placenta from the mother. As pregnancy progresses, the amount of glucose transported increases, with glycogen and fat stores being laid down, principally in the third trimester. In the well-term baby, there is hormonal and metabolic adaptation in the perinatal period to ensure adequate fuel supply to the brain and other vital organs after delivery, but in the preterm infant, abnormalities of glucose homeostasis are common. After initial hypoglycaemia, due to limited glycogen and fat stores, preterm babies often become hyperglycaemic because of a combination of insulin resistance and relative insulin deficiency. Hyperglycaemia is associated with increased morbidity and mortality in preterm infants, but what should be considered optimal glucose control, and how best to achieve it, has yet to be defined in these infants.

Safety of growth hormone after treatment of a childhood malignancy.

The use of growth hormone therapy in children with radiation-induced growth hormone (GH) deficiency is widely accepted, but the safety of this mitogenic hormone, particularly in children previously treated for cancer, continues to cause concern. A variety of malignant tumours have been induced in animals exposed to supraphysiological doses of GH, whereas hypophysectomised animals appear protected from carcinogen-induced neoplasms. Growth hormone and insulin-like growth factor-1 have been shown to stimulate both proliferation and transformation of normal and leukaemic human lymphocytes in vitro when used in supraphysiological doses. Despite the theoretical arguments, there is no evidence of an increased risk of tumour recurrence following GH therapy in replacement dosage in children previously treated for a malignancy.

Endocrinology of the neonate.

Endocrine disease in the neonate is uncommon, but, if it is not promptly recognised and treated, may be life-threatening or have profound long-term consequences. This article covers congenital adrenal hyperplasia, hypothyroidism, neonatal thyrotoxicosis and hypopituitarism. Other endocrine problems with which the MRCP(Paeds) candidate should be familiar are also listed.

Miller syndrome (postaxial acrofacial dysostosis): further evidence for autosomal recessive inheritance and expansion of the phenotype.

A sibship with postaxial acrofacial dysostosis syndrome (Miller syndrome) is reported. In addition to the characteristic facial and limb defects, previously undescribed anomalies, including midgut malrotation, gastric volvulus, and renal anomalies, are recorded.

Growth and puberty after growth hormone treatment after irradiation for brain tumours.

The impact of treatment with either cranial or craniospinal irradiation with or without cytotoxic chemotherapy for a brain tumour distant from the hypothalamic-pituitary axis was assessed in 29 children who had reached final height. All had received growth hormone treatment for radiation induced growth hormone deficiency. Final height, segmental growth during puberty, and duration of puberty were studied. Both craniospinal irradiation and the use of chemotherapy resulted in a significant and equal reduction in final height; this effect in those children who received both craniospinal irradiation and chemotherapy was additive. The degree of height loss was related to the age at irradiation, the most profound effect on final height occurring in the youngest at irradiation. The mean duration of puberty from G2-G4/B2-B4 (1.97 years) was not significantly different from the duration of puberty in normal children. Growth hormone increases growth velocity in children with radiation induced growth hormone deficiency but their final height is significantly less than their mid-parental height. The use of spinal irradiation and chemotherapy in the original treatment of brain tumours has a marked effect on growth which is not overcome with the use of growth hormone treatment in current doses. Early puberty of normal duration contributes to poor growth.