Normal values for phrenic nerve latency in children.

Data derived from detailed studies of normal phrenic nerve latency in a large group of children are presented. They highlight the major differences between the three previously published studies of normal children. Phrenic nerve latency shows a curvilinear relationship with age, averaging 6.0 ms at 0-6 months, falling to 4.8 ms between 1 and 2 years, then rising to 6.3 ms between 10 and 18 years of age. These data represent the largest published study on normal phrenic nerve latency in children.

Voluntary universal antenatal HIV testing.

OBJECTIVES: To assess the uptake of universal voluntary named HIV testing of hospital booked antenatal women and to identify behavioural and demographic factors associated with testing. To identify the number of previously undiagnosed women detected by the new policy and to compare prevalence among those testing with that measured by unlinked anonymous monitoring. DESIGN: Self-completion questionnaire and data abstraction from structured booking forms and virology laboratory records. SETTING: Central London teaching hospital antenatal clinic. PARTICIPANTS: One thousand three hundred and seventy-four women booking with a hospital based midwife during the 49 weeks from 27 July 1993 to 1 July 1994. RESULTS: Before the introduction of the new testing policy fewer than 10 women per year had an HIV test, and during the study this rose to 41% (548/1340). In univariate analysis, caucasian and Mediterranean ethnic origin, fewer previous live births, and more than one lifetime sexual partner were associated with higher uptake of HIV testing. In a multivariate model only the number of previous live births and ethnic origin remained significantly associated with testing. Six women out of 828 (1%) who completed the question about nonprescribed drug use stated that they had injected drugs, and four of these women accepted a test. Two women, both with recognised major risk factors for HIV infection, were diagnosed HIV antibody positive (a prevalence in the tested women of 0.36%). A further three women were already known to be HIV antibody positive. During the 12 months from July 1993 seven women (0.24%) were found to be positive by unlinked anonymous testing. CONCLUSIONS: The introduction of a universal approach to antenatal HIV testing appears feasible: it increased the uptake of the test and detected previously unrecognised infections. Many women chose not to be tested, however, and cases remained undiagnosed. Further studies are required to examine different models of offering HIV testing, reasons for declining the test, and the cost-benefit of antenatal HIV screening.

Phrenic nerve stimulation at the bedside in children; equipment and validation.

There is evidence that early diagnosis of postoperative phrenic nerve damage may improve outcome, by allowing early surgical treatment, in children following cardiac surgery. This has prompted the development of a simple method for measuring phrenic nerve latency at the bedside in children. We have evaluated the reproducibility of measurements made with this system in 11 children (4 months to 13 yrs) admitted for routine surgery or cardiac catheterizations, and have assessed the various components of variability inherent in the measurement of phrenic nerve latency. The overall variability of the phrenic nerve latency with this technique (95% confidence interval) is approximately +/- 1 ms, and differences greater than this between measurements are likely to reflect a real change in phrenic nerve function. Our results indicate that the bedside technique should be a useful method of the objective assessment of phrenic nerve function in children recovering from cardiac surgery.

Early assessment of diaphragmatic dysfunction in children in the ITU: chest radiology and phrenic nerve stimulation.

Diaphragmatic dysfunction is a common postoperative complication of cardiac surgery in children, with important effects on respiratory morbidity. Its early diagnosis, followed by prompt surgical intervention, has been shown to reduce morbidity. However, the commonest method of diagnosis, based on hemi-diaphragmatic elevation on the chest radiograph, may be less accurate than direct techniques for assessing phrenic nerve function. We have compared electrophysiological and radiological diagnoses of diaphragmatic abnormality in 100 children (aged 3 days to 17.5 yrs) undergoing cardiac surgery, looking at respiratory morbidity as assessed by the duration of ventilation, the time spent on the cardiac intensive care unit (CICU), and the requirement for reintubation. Despite showing good reproducibility, radiological diagnosis was neither sensitive nor specific in identifying patients with electrophysiological phrenic nerve damage. Analysis of the measures of outcome supported the electrophysiological technique. Patients with electrophysiological evidence of damage had a longer duration of ventilation, spent longer on the CICU, and had a greater incidence of reintubation than either radiologically abnormal or "normal" patients. Chest X-rays are not a good method for diagnosing phrenic nerve damage in the early postoperative period in children. If early diagnosis is needed, then direct assessment of phrenic nerve function, such as the measurement of phrenic latency, may be a better technique.

Normal gastric antral myoelectrical activity in early onset anorexia nervosa.

Anorexia, epigastric discomfort, nausea, and vomiting may result from disordered gastric motility and emptying. These features have been found in many adults with anorexia nervosa, but have never been investigated in early onset anorexia nervosa. In 14 patients with early onset anorexia nervosa (eight of whom had upper gastrointestinal tract symptoms), six children with other eating disorders, four children with non-ulcer dyspepsia, and 10 controls matched for age and sex, the non-invasive technique of surface electrogastrography was used to measure fasting and postprandial gastric antral electrical control activity, which underlies antral motility. The electrical signal was recorded by four bipolar silver/silver chloride electrodes attached to the upper abdomen, amplified and low pass filtered at 0.33 Hz before being displayed on a polygraph, digitised at 1 Hz, and stored on the hard disk of a personal computer for later offline analysis. Patients with non-ulcer dyspepsia had gastric antral dysrhythmias. No significant difference was found in the mean (SD) dominant frequency of the antral electrical control activity between patients with early onset anorexia nervosa (2.86 (0.35) cycles/minute (cpm)), patients with other eating disorders (3.14 (0.65) cpm), and controls (3.00 (0.46) cpm). The amplitude of electrical control activity increased postprandially in all but one subject and the fasting/postprandial amplitude ratio did not significantly differ between patients with early onset anorexia nervosa and controls, though patients with longer established disease had a smaller increase in amplitude. Gastric antral electrical dysrhythmias are not a feature of early onset anorexia nervosa and therefore do not induce or perpetuate food refusal in this disorder.

Phrenic nerve damage via a right thoracotomy in older children with secundum ASD.

Phrenic nerve damage (PND) in children after cardiac operations is now recognized as being more frequent than previously thought. In a prospective study on 400 children, we previously demonstrated electrophysiologic evidence of postoperative PND in approximately 16% of patients, with one third of cases occurring in children under 18 months. In the past 18 months, 30 children have had atrial septal defect (ASD) repairs as their only operative procedure. Fourteen children had ASD repairs via a midline incision, and 16 ASD repairs were via a right thoracotomy. No PND (assessed by phrenic nerve latency) was found after a midline approach. In the right thoracotomy group, 5 children had evidence of PND (31%; p = 0.05). Four of these 5 patients were female and more than 14 years of age. The incidence of damage in this pubescent group was 80% (p < 0.05). In the older age group the duration of ventilation was not prolonged, but affected patients had symptoms of fatigue and breathlessness postoperatively. These data suggest a strong association between right thoracotomies for ASD repairs and PND, especially in the female pubescent group when a low submammary skin incision (seventh to eighth space) is used with a fifth to sixth space entry into the thoracic cavity. In conclusion, the right thoracotomy approach for ASD repair appears to be a significant risk factor for PND in older children.

Non-invasive assessment of phrenic nerve function in infants following cardiac surgery.

PND occurs more frequently following cardiac surgery than was previously thought. Electrophysiological phrenic nerve testing is a reliable early test of the nerve's function. Phrenic nerve damage, particularly in children under 18 months of age, increases the risk of respiratory morbidity. Early diagnosis enables appropriate planning and treatment.