Non-invasive cardiac output monitoring with electrical velocimetry after cardiac surgery in infants.

INTRODUCTION: Low cardiac output following cardiac surgery is a major determinant of outcome that may be improved by early detection, yet there are no widely accepted methods for its measurement in young children. We evaluated the feasibility of the routine use of electrical velocimetry, a non-invasive technique providing continuous measurement of cardiac output, in infants in the early postoperative period. METHODS: With ethical approval and parental consent, infants undergoing cardiac surgery were recruited. The ICON electrical velocimetry monitor was attached on admission to the intensive care unit (ICU) and remained for up to 24h. RESULTS: A total of 15 infants were recruited, median age 3 months (interquartile range (IQR) 0.5-7.5) and weight 4.8kg (IQR 3.9-7.1), undergoing various operations. Cardiac index had a weak correlation with arterial lactate (r=-0.24, p=0.02) and no correlation with blood pressure, central venous pressure or arteriovenous oxygen difference. Data were recorded for a median of 19h (range 5-24), with lead detachment or movement artefact the most common causes of data loss. There was marked minute-to-minute variability, with 25% of consecutive measurements having >5% variability. CONCLUSION: Cardiac index measured by electrical velocimetry in infants in the early postoperative period is impaired by frequent data loss and marked intrapatient variability. Our feasibility study suggests that it is unsuitable for use as a routine monitoring tool in the setting of postsurgical ICU care.

Does direct admission from an emergency department with on-site neurosurgical services facilitate time critical surgical intervention following a traumatic brain injury in children?

OBJECTIVES: To compare the proportion of trauma craniotomies performed within 4 hours of presentation to emergency departments (ED) with and without on-site neurosurgery. DESIGN: A retrospective cohort analysis of data collected prospectively between January 2005 and April 2010 from patients with traumatic brain injury who were admitted to the paediatric intensive care unit (PICU) following traumatic brain injury. METHODS: Times for admission to ED, PICU and theatre were obtained through analysis of prospectively collected data management systems. Emergency department admission to neurosurgical theatre lag time was calculated using Microsoft Excel. Statistical analysis was performed using R (version 2.11.0). Subjects. Fifty-seven cases were identified. Twenty patients were admitted directly from ED to an on-site neurosurgical unit. The remaining 37 were transferred from regional EDs. RESULTS: Thirty-one craniotomies were performed. Thirteen in-patients admitted directly to hospital with neurosurgery on site. Eighteen in patients admitted at the local hospital and then transferred to the neurosurgical unit. Thirteen of Thirty-one (42%) craniotomies were performed within 4 hours. In the on-site group 10 of 13 (77%) craniotomies were performed within 4 hours compared to 3 of 18 (17%) in those transferred from regional ED (p = 0.001232) (Fisher exact test). Eleven patients were transferred directly from ED to neurosurgical theatre for emergency craniotomies. Within this subgroup, seven patients came from the cohort of admissions to a hospital with on-site neurosurgery. The remaining four patients were transferred from regional ED. There were eight extradural haematomas, one subdural haematoma and two intraparenchymal haemorrhages. The mean time from ED presentation to theatre was 1.68 hours and 5.46 hours for the on-site and regional transfer groups, respectively. There were no mortalities. CONCLUSIONS: Forty-two per cent of trauma craniotomies are performed within 4 hours. However, presentation to an ED with on-site neurosurgical services significantly facilitates time critical surgery in children following a traumatic brain injury.

Differential effects in cells exposed to ultra-short, high intensity electric fields: cell survival, DNA damage, and cell cycle analysis.

High power, nanosecond pulsed electric field (nsPEF) effects have been focused on bacterial decontamination, but the impact on mammalian cells is now being revealed. During nsPEF applications, electrical pulses of 10, 60 or 300 ns durations were applied to cells using electric field amplitudes as high as 300 kV/cm. Because of the ultra-short pulse durations, the energy transferred to cells is negligible, and only non-thermal effects are observed. We investigated the genotoxicity of nsPEF on adherent and non-adherent cell lines including 10 human lines and one mouse cell line with different origin and growth characteristics. We present data examining the effects of nsPEF exposure on cell survival assessed by clonogenic formation or live cell count; DNA damage determined by the comet assay and chromosome aberrations; and cell cycle parameters by measuring the mitotic indices of exposed cells. Using each of these indicators, we observed differential effects among cell types with non-adherent cells being more sensitive to the genotoxic effects of nsPEF exposures than adherent cells. Non-adherent cultures showed a rapid decrease in cell viability (90%), induction of DNA damage, and a decrease in the number of cells reaching mitosis after one 60 ns pulse with an electric field intensity of 60 kV/cm. These effects were not observed in cells grown as adherent cultures, with the exception of the mouse 3T3 cell line, which showed survival characteristics similar to non-adherent cultures. These data suggest that nsPEF genotoxicity may be cell type specific, and therefore have potential applications in the selective removal of one cell type from another, for example, in diseased states.

Changes in the profile of paediatric intensive care associated with centralisation.

OBJECTIVES: To compare intensive care admissions from a defined population of children in 1991 and 1999, during a period of organisational change and centralisation of paediatric intensive care. DESIGN: Two 12-month population-based audits were compared. Data were collected from hospitals in Birmingham and the surrounding districts. Denominator data were obtained from the Office for National Statistics. The place and rate of intensive care admission, the use of mechanical ventilation at admission, mortality and length of stay were compared. SETTING: Hospitals in the West Midlands. PARTICIPANTS: All children (<15 yrs) living in Birmingham who received intensive care during the study periods. MEASUREMENTS AND RESULTS: The number of Birmingham resident children admitted for intensive care increased from 277 to 510 (p<0.0001) i.e. from 1.3 to 2.3 admissions per 1,000 children per year. The proportion of admissions to the principal paediatric intensive care unit increased from 60% to 90% (p<0.0001) in association with its expansion from 6 to 18 beds. Length of ICU stay decreased from 103 to 74 h (difference 29 h, 95%CI, 4.78-54.2 h, p=0.0117). Child mortality fell over this period by 34 deaths per 100,000 children (95%CI 16-51, p<0.0001). The proportion of children requiring mechanical ventilation at admission to intensive care was unchanged. CONCLUSIONS: Centralisation by expansion of the lead centre was associated with a large increase in the numbers of children receiving intensive care consistent with an unmet need for paediatric intensive care in 1991, which may still exist. Centralisation of paediatric intensive care may have contributed to the fall in child mortality over this time period.

Calibration of the paediatric index of mortality in UK paediatric intensive care units.

AIM: To test a paediatric intensive care mortality prediction model for UK use. METHOD: Prospective collection of data from consecutive admissions to five UK paediatric intensive care units (PICUs), representing a broad cross section of paediatric intensive care activity. A total of 7253 admissions were analysed using tests of the discrimination and calibration of the logistic regression equation. RESULTS: The model discriminated and calibrated well. The area under the ROC plot was 0.84 (95% CI 0.819 to 0.853). The standardised mortality ratio was 0.87 (95% CI 0.81 to 0.94). There was remarkable concordance in the performance of the paediatric index of mortality (PIM) within each PICU, and in the performance of the PICUs as assessed by PIM. Variation in the proportion of admissions that were ventilated or transported from another hospital did not affect the results. CONCLUSION: We recommend that UK PICUs use PIM for their routine audit needs. PIM is not affected by the standard of therapy after admission to PICU, the information needed to calculate PIM is easy to collect, and the model is free.