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Chronic exposure to house-dust endotoxin may protect against allergen sensitization by enhancing type 1 immunity, according to investigators who studied 61 infants with at least three physician-documented episodes of wheezing. Investigators measured concentrations of house-dust endotoxin and allergens in the homes of these infants, who were from 9 to 24 months old. They evaluated allergen sensitization using skin-prick testing with a panel of common inhalant allergens (dust mite, cat, dog, cockroach, and mouse) and food allergens (milk, egg, and soya). To measure the potential effect of environmental endotoxin exposure on allergen sensitization, investigators compared concentrations of house-dust endotoxin in the homes of infants who tested positive and concentrations in the homes of those who tested negative. The homes of sensitized infants had significantly lower concentrations of endotoxin than the homes of infants who were not sensitized. In addition, increased house-dust endotoxin concentrations correlated with increased proportions of type 1 T-cell development in the infants' blood. Such concentrations did not correlate with increased proportions of type 2 T-cell development (Gereda JE et al: Lancet 2000; 355:1680).
Commentary: Here's another study to speculate that early protection from antigens predisposes to later allergy. I am still not sure how we know what is cause and what is effect. Could it be that allergic children are born to allergic parents and that those allergic parents are more likely to avoid dust in their homes? Maybe the genetic die is already cast before childhood exposure to allergens.
Use of antibiotics in children with gastrointestinal infections caused by Escherichia coli O157:H7 increases the risk of hemolytic-uremic syndrome (HUS), a new report shows. Investigators conducted a prospective study of children younger than 10 years who had diarrhea caused by E coli O157:H7. Ten (14%) of the total group of 71 developed HUS. Of these 10 children, five had taken antibiotics, though only nine (13%) of the 71 had been given antibiotics, at the direction of their physician. Investigators studied possible confounding factors for the association between antibiotics and development of HUS: demographics, the presence or absence of specific symptoms, the length of time from the onset of diarrhea to when the initial stool culture was obtained (a shorter interval may reflect more severe extraintestinal injury prompting earlier evaluation and greater risk for the syndrome), and initial measures of illness severity. After adjustment for the most important of these factors, antibiotic administration remained a risk factor for development of HUS (Wong CS et al: N Engl J Med 2000; 42:1930).
Commentary: Children treated with antibiotics were more than 14 times more likely to develop HUS than the other children. The authors suggest that empiric antibiotic use be avoided in children with diarrhea. If you are leaning toward treating, hold off until stool cultures identify a pathogen other than E coli O157:H7.
During professional meetings, investigators conducted an informal survey of pediatricians to find out how often they use alternating antipyretics to manage fever. Half of the 161 pediatricians who completed a 15-question written survey advised parents to alternate acetaminophen and ibuprofen. Physicians in practice for fewer than five years were significantly more likely to alternate antipyretics than physicians who were in practice longer. Though the alternation pattern varied, most often these pediatricians recommended taking acetaminophen every four hours alternating with ibuprofen every six hours.
Investigators noted that alternating acetaminophen and ibuprofen can be confusing to caregivers and may lead to incorrect dosing of either product or double dosing. The potential for dosing errors is compounded when pediatricians fail to ask parents what formulation of the antipyretic agents they have at home. In this survey, 20% of pediatricians provided advice without asking this question. Investigators also noted that evidence is lacking for the safety of combining acetaminophen and ibuprofen. In addition, there is no scientific evidence that the combination acts more quickly or has greater efficacy than either agent used alone. They advised telling parents to use a single agent to manage fever (Mayoral CE et al: Pediatrics 2000; 105:1009).
Commentary: It has been 20 years since fever phobia was described. Yet only 13% of physicians surveyed use discomfort rather than height of fever as the indication for treating fever. Old habits die hard.
Pediatricians and obstetricians underestimate both survival and freedom from handicap of preterm infants, a survey shows. A total of 362 pediatricians responded to a written, mailed questionnaire that asked them to estimate survival of infants born after 24 to 35 weeks of gestation and the percentage of survivors who could be expected to be free of a major handicap. Pediatricians significantly underestimated survival rates at each week of gestation. In addition, pediatricians and obstetricians significantly underestimated handicap-free rates of infants born at 23 through 36 weeks' gestation. At the most advanced gestational ages, estimates of both groups of physicians were progressively closer to actual rates, as determined from a summary of outcome studies based on gestational age.
Underestimation of positive outcome was associated with restriction in use of appropriate interventions. Compared with pediatricians who did not underestimate survival and freedom from handicap, those who underestimated positive outcome would less often use mechanical ventilation, cardiopulmonary resuscitation, inotropes, intravenous fluids, thermal support, and oxygen supplementation (Morse SB et al: Pediatrics 2000;105:1046).
Commentary: This study has two important points: The first is that perinatal outcomes may be better than you think. Second, the physician's estimate of a baby's odds of a good outcome changes how the doctor manages the baby. If you attend deliveries, advise mothers in premature labor, or direct care in a NICU, you need to have a good working knowledge of these outcome numbers.
Two cases of malaria reported in Suffolk County, NY. Last summer, two 11-year-old boys who spent the same week in August at the same summer camp in Suffolk County, NY, were seen by their doctors for fever, vomiting, and abdominal pain, among other symptoms. Both boys had healing maculopapular bite lesions. Examination of blood smears showed they were infected with Plasmodium vivax. Neither boy had traveled to an area with malaria or had a history of blood transfusion or organ transplantation. An extensive investigation failed to turn up any individuals in the area with malaria parasites. The probable explanation for the two cases of malaria was disclosed by routine mosquito trapping for eastern equine encephalitis by the Suffolk County Health Department during early August, when these cases of malaria would have been transmitted. Trapping from a campsite seven miles from the summer camp the boys attended yielded two types of Anopheles mosquitoes, which are competent malaria vectors. This finding, combined with the presence in the area of immigrants who could have malaria parasites in the bloodstream, suggests that the two young boys probably acquired their infections through the bite of one or more locally infected Anopheles mosquitoes (MMWR 2000;49(22):495).
Passive smoking associated with Legg-Calvé-Perthes disease (LCPD). Children exposed to passive smoke are at higher risk of developing LCPD, avascular necrosis of the femoral head, than children who are not exposed to smoke, according to a report by Spanish investigators. The study compared 90 patients with LCPD and 183 normal children, who were treated at an orthopedic clinic for disorders not related to LCPD. The children ranged in age from 2 to 14 years. Seventy-one (78.9%) of the LCPD group were passive smokers, compared with 79 of 183 (43.2%) in the control group. After controlling for age and gender, investigators determined that the risk of LCPD is more than five times higher in children exposed to passive smoke than in children who are not exposed to smoke (Garcia Mata S et al: J Pediatr Orthop 2000;20:326).
Preauricular tags tied to urinary tract anomalies. Protuberant fleshy papules located anterior to tragus or just anterior to the crus of the helix are considered of little clinical importance, though they may be associated with hearing impairment. Now a new study from Israel confirms what earlier research has suggested: Neonates with these preauricular tags are more likely than other infants to have urinary tract abnormalities.
Investigators used renal ultrasound on day 3 or 4 of life to screen 70 infants with isolated preauricular tags. A control group of 69 infants without preauricular tags also underwent urinary tract ultrasonography. In the group with isolated preauricular tags, six (8.6%) had urinary tract abnormalities: Five had hydronephrosis and one a horseshoe kidney. None of the infants in the control group had these abnormalities. All the infants with urinary tract abnormalities had normal chromosomes (Kohelet D et al: Pediatrics 2000;105:e61).
The latest American Academy of Pediatrics guidelines on feeding children advocate eliminating the bottle by 9 months of age. The strategy my office recommends to accomplish this goal has been enormously successful.
By 9 months, children have reduced their intake of formula or milk to 16 to 20 oz a day. Since a large portion of this amount is mixed with dry cereal, most babies are drinking only one or two 6-oz bottles. I instruct the parents to start the transition from bottle to cup by putting each 6-oz portion into a training cup. When the infant objects, offer bottles containing 4 oz of formula and 2 oz of water. Two days later, offer the full-strength training cup again, but alter the bottle mix to 3 oz of formula and 3 oz of water.
Each day the infant is first given the training cup before the diluted formula bottle. Every other day diminish the amount of formula in the mixture by 1 or 2 oz until the bottle is all water. Many infants will switch to the cup within the first several days. Recognizing the infant's limited awareness of long time spans was the inspiration that led to this gradual transition method.
When I teach children to swallow pills, I tell them to practice with candy first. They start by swallowing red hots, then move up to M&Ms, and finally graduate to Good & Plenty candies. By then most patients have gotten over the fear of choking on pillsespecially when I show them, side by side, how the size of the candy they swallowed compares to the size of the pills. Red hots are the same size as 10-mg Claritin tablets, M&Ms are the about the size of adult Tylenol, and Good & Plenty candies are the size of most oral antibiotics.
To help my adolescent patients swallow pills, I tell them to take a small bite of banana and chew it slightly, then place the pill in the middle of the chewed banana and swallow. The banana adds just the right bulk and consistency to hide a pill and makes swallowing it a cinch.
When testing for visual problems in young children, it is imperative to know whether the child knows how to count and read letters, especially when the family does not speak English.
I recently examined a 4-year-old girl, whose Spanish-speaking parents complained that she suffered from headaches and double vision. Through an interpreter they told me that at home she would call one pencil two pencils. She had suffered a fall several months back. When I held up one finger, she said "two." When I held up three fingers, she said "six." I discussed this finding with a neurologist and requested a CT scan. The scan showed sinusitis, which I treated with an antibiotic.
When I re-examined the child 10 days later, her headache was gone. Again I asked her to count my fingers. This time she counted two fingers as five and three fingers as four. I realized then that the little girl did not know how to count. In fact, she did not even have "one" in her vocabulary and began counting at "two." This explained why she would point at a pencil, or my one finger, and say "two." It was mere coincidence that she counted my three fingers as six when I tested her the first time.
So when you are examining very young patients for clinical signs of diplopia or other vision problems, keep in mind that things are not always what they seem.
Raghavendra Rao, MDPorterville, CA
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Julia McMillan. Journal Club. Contemporary Pediatrics 2000;8:117.