Scope and impact of early and late preterm infants admitted to the PICU with respiratory illness.

OBJECTIVE: To determine the clinical course and outcomes of children born early preterm (EPT, <32 weeks), late preterm (LPT, 32 to 35 weeks), and full term (FT, >or=36 weeks) who were subsequently admitted to the pediatric intensive care unit (PICU) with respiratory illness. STUDY DESIGN: Retrospective chart review of patients <2 years old admitted to a tertiary PICU with respiratory illness. RESULTS: Two hundred seventy-one patients met inclusion criteria: 17.3% were EPT, 12.2% were LPT, and 70.5% were FT. Lower respiratory tract infection was the most common diagnosis (55%) for all groups. Median PICU length of stay was longer for EPT (6.3 days) and LPT infants (7.1 days) compared with FT infants (3.7 days; P < .03 for both comparisons). EPT and LPT infants had longer hospital stays (median, 11.7 and 13.8 days, respectively) compared with FT infants (median, 7.1 days; P < .03 and P = .004, respectively). Median hospital charges were also greater for EPT ($85 151) and LPT ($83 576) groups compared with FT group ($55 122; P < .01 and P < .02, respectively). CONCLUSIONS: EPT and LPT infants comprise a considerable proportion of PICU admissions for respiratory illness and have greater resource utilization than FT infants.

Vitamin D Levels in Premature Children Admitted to the Hospital with Viral Respiratory Infection.

Children born preterm are at risk of hospital admission for respiratory infection in the first years of life. Vitamin D deficiency has been associated with increased risk of developing lower respiratory tract infection (LRTI). We assessed vitamin D levels in children born preterm admitted to the hospital ward or pediatric intensive care unit (PICU) with viral LRTI. A prospective observational cohort study was conducted over 3 years that enrolled 87 children <3 years of age, born <37 weeks of gestation. Children were enrolled in the ward and PICU if they had a diagnosis of LRTI with confirmed viral testing. Children seen in the outpatient clinic for well-child care were enrolled as study controls. Vitamin D and cathelicidin levels were measured and associations between vitamin D, cathelicidin, and admission sites were tested. Vitamin D levels were lower in children admitted to the PICU when compared to controls (28 ng/mL versus 36 ng/mL; P < 0.03) but were not different between children admitted to the ward or PICU. Overall, vitamin D levels were lower in children born late preterm (≥34 weeks, LPT) when compared to those born early preterm (<34 weeks, EPT), (28 ng/mL versus 34 ng/mL; P = 0.016), and EPT children were more likely to receive multivitamin supplementation before admission. Vitamin D levels in children born prematurely, admitted to the PICU, were lower than in controls. Overall levels were lower in LPT infants and this group did not receive multivitamin supplementation as much as those considered EPT. Prior research has shown associations between low vitamin D levels and respiratory disease. To our knowledge, this is the first study showing an association between low vitamin D levels and severity of respiratory disease, specifically in preterm children. Further, we found that late preterm children have lower levels of vitamin D and less frequent multivitamin supplementation.

The role of vitamin D in prevention and treatment of infection.

Vitamin D is well known for its classic role in the maintenance of bone mineral density. However, vitamin D also has an important "non-classic" influence on the body's immune system by modulating the innate and adaptive immune system, influencing the production of important endogenous antimicrobial peptides such as cathelicidin, and regulating the inflammatory cascade. Multiple epidemiological studies in adults and children have demonstrated that vitamin D deficiency is associated with increased risk and greater severity of infection, particularly of the respiratory tract. Although the exact mechanisms by which vitamin D may improve immune responses to infection continue to be evaluated, vitamin D supplementation trials of prevention and adjunct therapy for infection are underway. Given its influence on the immune system and inflammatory cascade, vitamin D may have an important future role in the prevention and treatment of infection.

A comparison of characteristics and outcomes in severe human metapneumovirus and respiratory syncytial virus infections in children treated in an intensive care unit.

BACKGROUND: Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are among the leading causes of respiratory tract infections requiring admission to the pediatric intensive care unit (PICU). We evaluated the risk factors, clinical courses and outcomes of severe HMPV disease relative to severe RSV in children admitted to the PICU. METHODS: Retrospective chart review of children ≤18 years old admitted to a tertiary PICU between October 2008 through July 2010 with acute respiratory tract infection and positive direct antigen stain or polymerase chain reaction for RSV or HMPV. RESULTS: One hundred thirty-three patients met inclusion criteria: 107 (80.5%) with RSV and 26 (19.5%) with HMPV. HMPV-infected patients were older than RSV children (3.4 vs. 1.5 years, P = 0.002) and more likely to have congenital heart disease (34.6% vs. 10.3%, P = 0.002). Although HMPV children required longer duration of mechanical ventilation (11 vs. 7 days, P = 0.01), there were no other differences in hospital course. HMPV patients were more likely to be discharged receiving inhaled steroids (53.8% vs. 30.8%, P = 0.03), but there were no differences in other outcome assessments. CONCLUSIONS: Children admitted to the PICU with HMPV are significantly older and more likely to have congenital heart disease than those with RSV. The course of illness was similar between the 2 groups, but HMPV-infected children were more likely to be discharged with inhaled steroid therapy.

Nicotine decreases agrin signaling and acetylcholine receptor clustering in C2C12 myotube culture.

The clustering of acetylcholine receptors (AChRs) in skeletal muscle fibers is a critical event in neuromuscular synaptogenesis. AChRs in concert with other molecules form postsynaptic scaffolds in response to agrin released from motor neurons as motor neurons near skeletal muscle fibers in development. Agrin drives an intracellular signaling pathway that precedes AChR clustering and includes the tyrosine phosphorylation of AChRs. In C2C12 myotube culture, agrin application stimulates the agrin signaling pathway and AChR clustering. Previous studies have determined that the frequency of spontaneous AChR clustering is decreased and AChRs are partially inactivated when bound by the acetylcholine agonist nicotine. We hypothesized that nicotine interferes with AChR clustering and consequent postsynaptic scaffold formation. In the present study, C2C12 myoblasts were cultured with growth medium to stimulate proliferation and then differentiation medium to stimulate fusion into myotubes. They were bathed in a physiologically relevant concentration of nicotine and then subject to agrin treatment after myotube formation. Our results demonstrate that nicotine decreases agrin-induced tyrosine phosphorylation of AChRs and decreases the frequency of spontaneous as well as agrin-induced AChR clustering. We conclude that nicotine interferes with postsynaptic scaffold formation by preventing the tyrosine phosphorylation of AChRs, an agrin signaling event that precedes AChR clustering.