Nosocomial enterococcal infections in children

OBJECTIVES

To identify factors that are associated with an increased risk of nosocomial enterococcal infection in children.

METHODS

A matched case-control study was conducted between January 1989 and July 1993 at the Children's National Medical Center, Washington DC. One control patient for each case was identified. Control patients did not have nosocomial enterococcal infections and were matched with cases on the basis of age and time of admission closest to the case within a three-month period. Data were collected from systematic review of patient medical records. One hundred and one study patients (cases) were matched with 101 control patients. A case was defined as a patient with enterococcal infection who met the Centers for Disease Control and Prevention criteria for nosocomial infection. Microbiology methods included isolation, identification, and antimicrobial susceptibility testing of enterococci from clinical specimens.

RESULTS

Risk factors associated with nosocomial enterococcal infections were determined by multiple conditional logistic regression analyses of the cases and controls. Factors identified were placement of a central line, gastrointestinal tract pathology, and administration of multiple antimicrobial agents. The median duration of antimicrobial therapy prior to diagnosis of nosocomial enterococcal infection was approximately 1 week.

CONCLUSION

The incidence of nosocomial enterococcal infections in children may be controlled by limiting the number of antimicrobial agents administered to hospitalized high risk patients. The importance of our findings is relevant in an era of increasing rates of antimicrobial resistance in nosocomial enterococcal infections.

The impact of prematurity: a perspective of pediatric intensive care units

OBJECTIVE

To evaluate the relative resource use of pediatric intensive care unit (PICU) patients who had been born prematurely.

DESIGN

Nonconcurrent cohort study.

SETTING

Consecutive admissions to 16 voluntary PICUs.

PATIENTS

A total of 431 formerly premature patients (FPP) and 5,319 nonpremature patients.

INTERVENTIONS

None

METHODS

Patients with a history of prematurity and a prematurity-related complication or an anatomical deformity were compared for demographic and resource requirements to a group of non-premature patients by a bivariable logistic regression analysis that controlled for age as a co-morbid factor.

RESULTS

Compared with other patients, FPP were younger (34.9 +/- 2.2 months vs. 72.4 +/- 1.0 months; p < .001), readmitted to the PICU more often during the same hospitalization (11.1% vs. 5.5%; p < .001), used more chronic technologies (ventilators, gastrostomy tubes, tracheostomy tubes, and parenteral nutrition; 30.3% vs. 5.6%; p < .001), and had longer lengths of stay (5.98 +/-0.59 days vs. 3.56 +/- 0.12 days; p = .004). FPP had significantly higher use of ventilators (45.5% vs. 35.0%; p < .007) and lower use of arterial catheters (27.8% vs. 35.9%, p = .006) and central venous catheters (16.9% vs. 20.9%, p = .026) than nonprematures. The need for other PICU resources, including vasopressors, were similar.

CONCLUSIONS

FPP used more chronic and acute care resources than patients who were not prematurely born. Continued improvements in neonatal care will influence change in many aspects of the health care system. This will also affect the delivery of care to the current patient base of the PICU.

Prognostication and certainty in the pediatric intensive care unit

OBJECTIVE

Prognostication is central to developing treatment plans and relaying information to patients, family members, and other health care providers. The degree of confidence or certainty that a health care provider has in his or her mortality risk assessment is also important, because a provider may deliver care differently depending on their assuredness in the assessment. We assessed the performance of nurse and physician mortality risk estimates with and without weighting the estimates with their respective degrees of certainty.

METHODS

Subjective mortality risk estimates from critical care attendings (n = 5), critical care fellows (n = 9), pediatric residents (n = 34), and nurses (n = 52) were prospectively collected on at least 94% of 642 eligible, consecutive admissions to a tertiary pediatric intensive care unit (PICU). A measure of certainty (continuous scale from 0 to 5) accompanied each mortality estimate. Estimates were evaluated with 2 x 2 outcome probabilities, the kappa statistic, the area under the receiver operating characteristics curve, and the Hosmer and Lemeshow goodness-of-fit chi(2) statistic. The estimates were then reevaluated after weighting predictions by their respective degree of certainty.

RESULTS

Overall, there was a significant difference in the predictive accuracy between groups. The mean mortality predictions from the attendings (6.09%) more closely approximated the true mortality rate (36 deaths, 5.61%) whereas fellows (7.87%), residents (10.00%), and nurses (16.29%) overestimated the mean overall PICU mortality. Attendings were more certain of their predictions (4.27) than the fellows (4.01), nurses (3.79), and residents (3.75). All groups discriminated well (area under receiver operating characteristics curve range, 0.86-0.93). Only PICU attendings and fellows did not significantly differ from ideal calibration (chi(2)). When mortality predictions were weighted with their respective certainties, their performance improved.

CONCLUSIONS

The level of medical training correlated with the provider's ability to predict mortality risk. The higher the level of certainty associated with the mortality prediction, the more accurate the prediction; however, high levels of certainty did not guarantee accurate predictions. Measures of certainty should be considered when assessing the performance of mortality risk estimates or other subjective outcome predictions.

Oyster metallothionein as an oxyradical scavenger: implications for hemocyte defense responses

In order to better understand the interplay between metallothionein (MT) and reactive oxygen species (ROS) in oyster hemocytes, studies of the hydrogen peroxide (H2O2) scavenging properties of MT were carried out in a cell-free system. Mammalian MT is involved in protection against oxidative stress by virtue of its ability to scavenge free radicals; therefore, the H2O2 scavenging potentials of Crassostrea virginica and rabbit MTS were compared. Oyster and rabbit MTs showed similar dose-dependent suppression of H2O2-stimulated, luminol-augmented chemiluminescence (CL); the EC50 for CL (25 microM H2O2) was approximately 1.0 microM MT for both species. The interaction of ROS with MT in hemocytes could play a role in protection of the cells and surrounding tissues from oxidants associated with antimicrobial responses. Mobilization of bound zinc from MT by hemocyte-derived ROS may produce aberrant regulatory effects on various cellular processes. The data suggest that MT may be involved in immunoregulatory pathways in oyster hemocytes as a result of its ability to scavenge antimicrobial ROS.

Teaching physicians how to break bad news: a 1-day workshop using standardized parents

OBJECTIVE

To evaluate the effectiveness of a training program using standardized parents (SPs) to improve the performance of pediatric intensive care fellows in communicating bad news to parents.

DESIGN

Self-controlled crossover design.

SETTING

Tertiary pediatric intensive care unit in a university-affiliated children's hospital.

PARTICIPANTS

Seven pediatric intensive care fellows and 4 trained volunteers (2 sets of SPs) participated in the study.

METHODS

Two case scenarios of children admitted to the intensive care unit with a near-fatal diagnosis were used for the fellow's interactions with the SPs. The SPs had received 15 hours of training in role playing, performance evaluation, and giving feedback to the physicians. At the end of the first session, SPs provided feedback to the physicians under each of the 5 following categories: communication skills, content issues, support systems, interventions, and parent perceptions. During the second session, the parent meeting was repeated with a new but similar case scenario and a different set of SPs. Both sessions were videotaped, and a rater blinded to the order of the sessions used a weighted scale based on a checklist to score changes in physician performance.

RESULTS

The performance by the fellows showed a significant mean (+/-SEM) improvement in scores of 18.1 (+/-5.2) points (P = .007) between the first and the second sessions. Ranking of session scores revealed that physician performance improved significantly during the second session (Wilcoxon signed rank test, P = .002).

CONCLUSIONS

To our knowledge this is the first study that demonstrates short-term improvement in physician performance in conveying bad news in a pediatric intensive care setting using SPs in a 1-day workshop.

Clinical applications of transiently evoked otoacoustic emissions in the pediatric population

Our objectives were 1) to determine whether transiently evoked otoacoustic emissions (TEOAEs) are affected by the status of the tympanic membrane (TM) and middle ear (ME) as determined by clinical examinations and tympanograms; 2) to determine the efficacy of TEOAEs in detecting hearing loss; and 3) to determine the relative effects of the ME status and hearing loss on TEOAEs. In a prospective observational study in a tertiary care children's hospital, 89 patients (169 ears; 9 ears eliminated from analyses) were examined by 2 attending pediatric otolaryngologists for otologic conditions and underwent audiologic evaluations including TEOAEs from August 1994 through May 1995. The main outcome measures were presence or absence of TEOAE whole reproducibility (WR) and reproducibility (R) at 2 kHz. Statistical analyses showed that of the 8 ME and TM conditions evaluated (normal, TM perforation, pressure equalization [PE] tube, TM retraction, tympanosclerosis, TM atrophy, ME effusion, surgery other than PE tube insertion), only the presence of ME effusion and normal examination findings had a significant effect on the results of WR and R at 2 kHz. Of the 6 different types of tympanograms evaluated (A, B, C, AD, As, B with large volume), type A, B, and C tympanograms had a significant effect on WR and types A and B had a significant effect on R at 2 kHz. Hearing losses > or = 25 dB hearing level (HL) at any of the 5 frequencies (0.25, 0.5, 1, 2, and 4 kHz) were well predicted by the absence of WR and R at 2 kHz. When clinical examination and impedance data were evaluated simultaneously with hearing status, hearing status had a greater effect on WR and R at 2 kHz. We conclude that type B and C tympanograms and the presence of ME effusion (which reflect abnormal ME status) have an adverse effect on TEOAEs. However, the presence of hearing loss is the most significant predictor of TEOAE results. The TEOAE WR and R at 2 kHz are effective in identifying patients with normal hearing and with hearing losses > or = 25 dB HL.

Vancomycin-resistant Enterococcus faecium colonization in children

Nosocomial vancomycin-resistant Enterococcus (VRE) infections have been described in only small numbers of pediatric patients. In none of these studies were multivariate analyses performed to assess which factors were independent risk factors in these patients. In the present cohort study of patients admitted to our hematology/oncology unit, surveillance cultures revealed a colonization rate of 24% and all isolates were identified as Enterococcus faecium. Risk factors associated with colonization with VRE identified by multiple logistic regression analysis included young age and chemotherapy with antineoplastic agents, cefotaxime, vancomycin, and ceftazidime. A molecular epidemiological tool, pulsed-field gel electrophoresis, was used to determine the relatedness of the VRE isolates detected. DNA analysis by this method identified two major clusters of VRE isolates. Young children with gastrointestinal colonization with VRE, without evidence of clinical infection, can serve as a reservoir for the spread of VRE.

Decision support issues using a physiology based score

OBJECTIVE

As physiology based assessments of mortality risk become more accurate, their potential utility in clinical decision support and resource rationing decisions increases. Before these prediction models can be used, however, their performance must be statistically evaluated and interpreted in a clinical context. We examine the issues of confidence intervals (as estimates of survival ranges) and confidence levels (as estimates of clinical certainty) by applying Pediatric Risk of Mortality III (PRISM III) in two scenarios: (1) survival prediction for individual patients and (2) resource rationing.

DESIGN

A non-concurrent cohort study.

SETTING

32 pediatric intensive care units (PICUs).

PATIENTS

10608 consecutive patients (571 deaths).

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

For the individual patient application, we investigated the observed survival rates for patients with low survival predictions and the confidence intervals associated with these predictions. For the resource rationing application, we investigated the maximum error rate of a policy which would limit therapy for patients with scores exceeding a very high threshold. For both applications, we also investigated how the confidence intervals change as the confidence levels change. The observed survival in the PRISM III groups >28, >35, and >42 were 6.3, 5.3, and 0%, with 95% upper confidence interval bounds of 10.5, 13.0, and 13.3%, respectively. Changing the confidence level altered the survival range by more than 300% in the highest risk group, indicating the importance of clinical certainty provisions in prognostic estimates. The maximum error rates for resource allocation decisions were low (e. g., 29 per 100000 at a 95% certainty level), equivalent to many of the risks of daily living. Changes in confidence level had relatively little effect on this result.

CONCLUSIONS

Predictions for an individual patient's risk of death with a high PRISM score are statistically not precise by virtue of the small number of patients in these groups and the resulting wide confidence intervals. Clinical certainty (confidence level) issues substantially influence outcome ranges for individual patients, directly affecting the utility of scores for individual patient use. However, sample sizes are sufficient for rationing decisions for many groups with higher certainty levels. Before there can be widespread acceptance of this type of decision support, physicians and families must confront what they believe is adequate certainty.

A complex translocation involving chromosomes 2, 9 and 22 in a patient with chronic myeloid leukemia

A patient with a high leukocyte count, diagnosed with chronic myeloid leukemia was referred for cytogenetic study. Peripheral blood and bone marrow cells were cultured without mitogenic stimulation. All karyotypes represented rare, varient Philadelphia chromosome with-three way translocation, i.e. t (2; 9; 22) (p13; q34; q11).

Pediatric risk of admission (PRISA): a measure of severity of illness for assessing the risk of hospitalization from the emergency department

STUDY OBJECTIVE

The development and validation of a pediatric emergency department severity of illness assessment method, using hospital admission as the primary outcome.

METHODS

A random sample of 25% of ED charts from 4 consecutive months in a university-affiliated pediatric hospital was reviewed, after exclusion of children with minor injuries and children triaged to the nonurgent clinic. Sampled data included components of the medical history, physical findings, physiologic variables, diagnoses, and ED therapies. Univariate and multivariate logistic regression analyses, with bootstrapping validation, were performed to develop a bias-corrected model estimating the probability of hospital admission.

RESULTS

Of the 2,683 ED patients whose records were reviewed, 643 (24%) were admitted to the hospital. The final model, which yielded a Pediatric Risk of Admission (PRISA) score, included the following: 3 components of the medical history, 3 chronic disease factors, 9 physiologic variables, 2 therapies, and 4 interaction terms. Overall, the number of hospital admissions was well predicted in both the 80% development and 20% validation samples. In the former, 514 admissions were predicted and 514 were observed; in the latter, 126.9 admissions were predicted and 129 were observed. The Hosmer-Lemeshow goodness-of-fit test demonstrated good agreement between observed and expected admissions in consecutive deciles of admission probability; total chi2 was 10.49 (P=.233) for the development sample and 11.85 (P=.222) for the validation sample. The areas under the receiver operating characteristic curves (+/-SE) were .86+/-.011 and .825+/-.024, respectively. As the risk of hospital admission increased, the proportions of patients using unique hospital-based resources and using ICU resources increased, and the proportion of patients dying increased.

CONCLUSION

The probability of admission to the hospital can reliably be estimated from data available during the pediatric ED stay. Applications for this method include studies of quality and efficiency of care and measurements of severity of illness.

Parental literacy level and understanding of medical information

OBJECTIVE

To ascertain the impact of literacy level on parents' understanding of medical information and ability to follow therapy prescribed for their children.

DESIGN/METHODS

A prospective cohort of parents accompanying their children for acute care. Parents were interviewed about demographic status, their child's health, and use of pediatric preventive services. The Rapid Estimate of Adult Literacy in Medicine (REALM) test was used to assess parental literacy. The same parent was interviewed 48 to 96 hours later and asked to recall the child's diagnosis, any medication prescribed, and instructions.

RESULTS

A total of 633 patients were enrolled. Follow-up was obtained in 543 patients (85.8%). Mean parental age was 32.43 years (SD = 9.07). Mean REALM score was 57.6 (SD = 10.9), corresponding to a 7th- to 8th-grade reading level, with a mean parental educational level of 13.43 years (SD = 2.09). Low REALM score was significantly correlated with young parental age and parental education. African-American race was associated with lower REALM scores. After controlling for these variables, REALM score significantly correlated with parental perception of how sick the child was, but not with use of preventive services, comprehension of diagnosis, medication name and instructions, or ability to obtain and administer prescribed medications.

CONCLUSIONS

Parental literacy level did not correlate with use of preventive services or parental understanding of or ability to follow medical instructions for their children.

Length of stay and efficiency in pediatric intensive care units

OBJECTIVE

Assessment of pediatric intensive care unit (PICU) efficiency with a length of stay prediction model and validation of this assessment by an efficiency measure based on daily use of intensive care unit-specific therapies.

DESIGN

Inception cohort study of data acquired between 1989 and 1994.

SETTING

Thirty-two PICUs, 16 selected randomly and 16 volunteering.

SUBJECTS

Consecutive admissions of 10,658 patients (466 deaths) who stayed at least 2 hours and up to 12 days in the PICU.

MEASUREMENTS

Length of stay and its prediction from a model with admission day data (PRISM III-24, diagnostic factors, mechanical ventilation). For validation 11 PICUs recorded each patient's "efficient" days, that is, days when at least one PICU-specific therapy was given. PICU efficiency was computed as either the ratio of the observed efficient days or the days accounted for by the predictor variables to the total care days, and the agreement was assessed by Spearman's rank correlation analysis.

RESULTS

The total care days provided by each PICU (n = 32) were well predicted by the length of stay model (r = 0.946). The agreement in 11 validation PICUs between therapy-based efficiency (range 0.30 to 0.67) and predictor-based efficiency (range 0.31 to 0.63) was excellent (rank correlation r = 0.936, p < 0.0001).

CONCLUSION

PICU efficiency comparisons with either method are nearly equivalent. Predictor-based efficiency has the advantage that it can be computed from admission day data only.

Cardiopulmonary resuscitation in pediatric intensive care units

OBJECTIVE

To determine the effectiveness of cardiopulmonary resuscitation (CPR) in the pediatric intensive care unit (ICU).

DESIGN

A nonconcurrent cohort study of consecutive admissions.

SETTING

Thirty-two pediatric ICUs.

PATIENTS

Consecutive admissions to 32 pediatric ICUs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pediatric ICU patients were followed for the occurrence of a cardiopulmonary arrest (external cardiac massage for at least 2 mins). Patients who were in a state of continuous cardiopulmonary arrest on admission, or who never achieved stable vital signs, were excluded from the study. A total of 205 patients, from a sample of 11,165 (1.8%) pediatric admissions, experienced a cardiopulmonary arrest. Overall, 28 (13.7%) patients survived to hospital discharge. Neither mean ages nor age distribution affected survival. Only two diagnostic categories, traumatic illness, and other etiologies, were associated with survival. None of the patients fitting this category survived (p = .0028). The durations of CPR for survivors and nonsurvivors were 22.5 +/- 10.1 and 24.8 +/- 1.9 mins, respectively (p = .015). For CPR durations of <15 mins, 15 to 30 mins, and >30 mins, the survival rates were 18.6%, 12.2%, and 5.6%, respectively (linear trend p = .022). Thirty-five (17.1%) patients had a cardiopulmonary arrest before pediatric ICU admission and another arrest in the pediatric ICU. Only two (5.7%) of these 35 patients survived to discharge. Pediatric ICU survival decreased as the number of pediatric ICU arrests increased. Patients with one arrest (n = 155), two arrests (n = 29), and more than three arrests (n = 21) experienced survival rates of 14%, 14%, and 9.5%, respectively. Severity of illness, as measured by the Pediatric Risk of Mortality III score, was a significant predictor of survival (p < .001).

CONCLUSIONS

Pediatric ICU cardiac arrest is an uncommon event. When it does occur, prehospital CPR, duration of resuscitation, traumatic etiology, and severity of illness are important factors associated with survival.

Pediatric critical care training programs have a positive effect on pediatric intensive care mortality

OBJECTIVE

Comparison of severity and diagnosis-adjusted mortality rates from pediatric intensive care units (ICUs) staffed by physicians training in pediatric critical care, as well as pediatric residents, with mortality rates from pediatric ICUs staffed with only pediatric residents.

DESIGN

Cohort study.

SETTING

Sixteen volunteer pediatric ICUs, eight with critical care fellowships, and eight without such programs.

PATIENTS

Consecutive admissions until at least 14 deaths occurred at each site.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Descriptive data and Pediatric Risk of Mortality scores were collected. Severity and diagnosis-adjusted mortality risk for each patient was computed by a predictor developed in an independent sample. The effect of fellowship programs was analyzed at the institution level by ranking the pediatric ICUs in terms of observed/predicted mortality rates, and, at the patient level, by including a training factor into the predictor model. The use of monitoring and therapeutic modalities was compared in the two types of pediatric ICUs by severity-adjusted odds ratios. There were 2,744 admissions (145 deaths) to the eight fellowship pediatric ICUs and 3,006 admissions (150 deaths) to the eight nonfellowship pediatric ICUs. Institutional characteristics were not different between the two pediatric ICU sets. The raw mortality rates were similar (fellowship 5.28%; nonfellowship 4.99%, p = .714). Institution-level analyses indicated that fellowship pediatric ICUs performed better than nonfellowship pediatric ICUs; fellowship pediatric ICUs ranked better than pediatric ICUs without such programs (Wilcoxon rank-sum test, p = .020). However, both the best and the worst ranked pediatric ICUs had fellowships. Patient-level analyses also indicated that outcome was significantly influenced by the fellowship status of the pediatric ICU. Using two different patient-level analytic approaches, the odds of dying in a fellowship pediatric ICU vs. a nonfellowship pediatric ICU were 0.592 (95% confidence interval 0.468 to 0.749, p = .0001) and 0.714 (95% confidence interval 0.529 to 0.964, p = .028). Pediatric ICUs with fellowship programs performed more (p < .05) invasive monitoring, including intra-arterial catheters and central venous pressure catheters, and more technological therapies such as mechanical ventilation.

CONCLUSIONS

Pediatric ICUs with critical care fellowship programs are generally associated with better risk-adjusted mortality rates than pediatric ICUs without such fellowship training programs. The cause for this effect requires a more in-depth study. The presence or absence of such training programs does not guarantee superior or inferior performance.

The Pediatric Risk of Mortality III--Acute Physiology Score (PRISM III-APS): a method of assessing physiologic instability for pediatric intensive care unit patients

OBJECTIVE

To develop a physiology-based measure of physiologic instability for use in pediatric patients that has an expanded scale compared with the Pediatric Risk of Mortality (PRISM) III score.

STUDY DESIGN

Data were collected from consecutive admissions to 32 pediatric ICUs (11,165 admission, 543 deaths). Patient-level data included physiologic data, outcomes, descriptive information, and diagnoses. Physiologic data included the most abnormal values in the first 24 hours of pediatric ICU stay from 27 variables. Initially, ranges of each physiologic variable were evaluated for their association with mortality. A multi-variate logistic regression analysis was used to determine the final variables and their ranges. Integer scores reflecting the relative contribution to mortality risk were assigned to the variable ranges.

RESULTS

A total of 59 ranges of 21 physiologic variables were selected. This score is called the Pediatric Risk of Mortality III--Acute Physiology Score (PRISM III-APS). Mortality increased as the PRISM III-APS score increased. Most patients have PRISM III-APS scores less than 10, and these patients have a mortality risk of less than 1%. At the other extreme, the mortality rate of the 137 patients with a PRISM III-APS score of greater than 80 was greater than 97%.

CONCLUSION

The PRISM III-APS score is an expanded measure of physiologic instability that has been validated against mortality. Compared with PRISM III, PRISM III-APS should be more sensitive to small changes in physiologic status.

Ideal timing of pediatric laryngotracheal reconstruction

OBJECTIVE

To determine whether there is an ideal age at which to perform a laryngotracheal reconstruction (LTR) in the pediatric population.

DESIGN

Prospective observational study.

SETTING

Tertiary care children's hospital.

PATIENTS

Forty-eight patients aged 48 months or younger with laryngotracheal stenosis who underwent 50 LTRs from October 1, 1986, to June 30, 1995. Patients were divided into 2 groups: group 1, aged 8 through 24 months (22 patients); group 2, aged 25 through 48 months (26 patients).

INTERVENTION

Endoscopy and LTR.

MAIN OUTCOME MEASURES

Successful decannulation.

RESULTS

Statistical analysis showed that (1) patients in group 2 had more severe degree of laryngotracheal stenosis as determined by duration of stenting with no difference in multiple sites of stenosis or type of repair required to correct laryngotracheal stenosis and (2) patients in group 2 were more likely to have successful decannulation.

CONCLUSION

Laryngotracheal reconstruction at a younger age (< 25 months) is important for a child's speech and language development as well as for eliminating the morbidity and mortality associated with a tracheotomy. However, LTR at a younger age is associated with a higher risk of failure despite lesser degree of pathology. Therefore, although we still recommend LTR at a younger age since it may be beneficial for a child's speech and language development and avoidance of tracheotomy complications, this recommendation may be at the price of LTR failure and requirement for revision procedures.

Correlation of P-glycoprotein expression and function in childhood acute leukemia: a children's cancer group study

Clinical drug resistance may be attributed to the simultaneous selection and expression of genes modulating the uptake and metabolism of chemotherapeutic agents. P-glycoprotein (P-gp) functions as a membrane-associated drug efflux pump whose increased expression results in resistance to anthracyclines, epipodophyllotoxins, vinca alkaloids, and some alkylating agents. This type of resistance occurs as both de novo and acquired resistance to therapy for leukemia. We have studied P-gp expression and function in childhood acute leukemias by developing a series of doxorubicin- and vincristine-selected CEM, T-cell lymphoblastoid cell lines that recapitulate the low levels of expression and resistance seen clinically. These cell lines have been used to develop flow cytometric assays for the semiquantitative measurements of P-gp expression with the MRK16 monoclonal antibody and P-gp function using the enhanced retention of rhodamine 123 in the presence of verapamil, a resistance modulator. Kolmogorov-Smirnov statistics, represented by the D measurement, are used to determine the difference in level of P-gp expression by comparing MRK16 staining to an IgG2a isotype control. When D is > 0.09, there is an excellent correlation (R = 0.82) between P-gp expression and function. The evaluation of 107 bone marrow specimens from 84 children with lymphoblastic or myelogenous leukemia showed a statistically significant (P = .004) increase in P-gp function at relapse. P-gp expression at relapse, however, approached but did not reach a significant level (P = .097). Using this methodology, we can identify patients with levels of P-gp expression and function that we can define clinically, as well as children with discordant multidrug resistance phenotypes. This study supports the role of P-gp-mediated drug resistance in childhood leukemia and confirms that P-gp expression and function are measurable in their leukemic blasts. These assays provide the means for the in vitro testing of resistance modulators and the monitoring of in vivo response to treatment with these agents.

PRISM III: an updated Pediatric Risk of Mortality score

OBJECTIVES

The relationship between physiologic status and mortality risk should be reevaluated as new treatment protocols, therapeutic interventions, and monitoring strategies are introduced and as patient populations change. We developed and validated a third-generation pediatric physiology-based score for mortality risk, Pediatric Risk of Mortality III (PRISM III).

DESIGN

Prospective cohort.

SETTING

There were 32 pediatric intensive care units (ICUs): 16 pediatric ICUs were randomly chosen and 16 volunteered.

PATIENTS

Consecutive admissions at each site were included until at least 11 deaths per site occurred.

MEASUREMENTS AND MAIN RESULTS

Physiologic data included the most abnormal values from the first 12 and the second 12 hrs of ICU stay. Outcomes and descriptive data were also collected. Physiologic variables where normal values change with age were stratified by age (neonate, infant, child, adolescent). The database was randomly split into development (90%) and validation (10%) sets. Variables and their ranges were chosen by computing the risk of death (odds ratios) relative to the midrange of survivors for each physiologic variable. Univariate and multivariate statistical procedures, including multiple logistic regression analysis, were used to develop the PRISM III score and mortality risk predictors. Data were collected on 11,165 admissions (543 deaths). The PRISM III score has 17 physiologic variables subdivided into 26 ranges. The variables most predictive of mortality were minimum systolic blood pressure, abnormal pupillary reflexes, and stupor/coma. Other risk factors, including two acute and two chronic diagnoses, and four additional risk factors, were used in the final predictors. The PRISM III score and the additional risk factors were applied to the first 12 hrs of stay (PRISM III-12) and the first 24 hours of stay (PRISM III-24). The Hosmer-Lemeshow chi-square goodness-of-fit evaluations demonstrated absence of significant calibration errors (p values: PRISM III-12 development = .2496; PRISM III-24 development = .1374; PRISM III-12 validation = .4168; PRISM III-24 validation = .5504). The area under the receiver operating curve and Flora's z-statistic indicated excellent discrimination and accuracy (area under the receiver operating curve - PRISM III-12 development 947 +/- 0.007; PRISM III-24 development 0.958 +/- 0.006; PRISM III-12 validation 0.941 +/- 0.021; PRISM III-24 validation 0.944 +/- 0.021; Flora's z-statistic - PRISM III-12 validation = .7479; PRISM III-24 validation = .9225), although generally, the PRISM III-24 performed better than the PRISM III-12 models. Excellent goodness-of-fit was also found for patient groups stratified by age (significance levels: PRISM III-12 = .1622; PRISM III-24 = .4137), and by diagnosis (significance levels: PRISM III-12 = .5992; PRISM III-24 = .7939).

CONCLUSIONS

PRISM III resulted in several improvements over the original PRISM. Reassessment of physiologic variables and their ranges, better age adjustment for selected variables, and additional risk factors resulted in a mortality risk model that is more accurate and discriminates better. The large number of diverse ICUs in the database indicates PRISM III is more likely to be representative of United States units.

Risk factors for nosocomial infection in critically ill children: a prospective cohort study

OBJECTIVE

To identify factors in pediatric intensive care unit (ICU) patients that are associated with an increased risk of nosocomial infections.

DESIGN

A prospective, 1-yr cohort study.

SETTING

A 16-bed pediatric ICU in a multidisciplinary, regional referral center.

SUBJECTS

All patients admitted to the pediatric ICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was the development of nosocomial infection. Out of 945 consecutive admissions, 75 patients developed 96 nosocomial infections. The most frequent infection sites were the lower respiratory tract (35%), the bloodstream (21%), and the urinary tract (21%). The most common organisms isolated were Gram-negative bacteria (53%, Gram-positive bacteria (27%), and fungi (9%). Variables significantly associated with the development of nosocomial infections included age, weight, Pediatric Risk of Mortality (PRISM) score, device utilization ratio, antimicrobial therapy, histamine-2 (H2) receptor blocker use, immune status, parenteral nutrition, and length of stay. When combined in a multivariate logistic regression model, the significant variables were operative status, PRISM score, device utilization ratio, antimicrobial therapy, parenteral nutrition, and length of stay before the onset of infection. The area under the receiver operating characteristic curve was 0.868. At a probability of 0.15, the sensitivity was 66.67%, and the specificity was 87.82%.

CONCLUSIONS

Patients at risk for developing nosocomial infection can be identified using a multivariate logistic regression model with a high degree of sensitivity and specificity. These data indicate that institutional nosocomial rates need to be adjusted for risk factors. This model could help target patients at high risk for developing nosocomial infections for preventive strategies.

The effect of gastroesophageal reflux on laryngotracheal reconstruction

OBJECTIVES

To determine the need for preoperative evaluation for gastroesophageal reflux disease (GERD) in all children undergoing laryngotracheal reconstruction (LTR) and to assess the effect of GERD on the outcome of LTR.

DESIGN

Prospective, single-blind observational study.

SETTING

Tertiary care children's hospital.

PATIENTS

Seventy-four pediatric patients with laryngotracheal stenosis who underwent LTR at the Children's National Medical Center, Washington, DC, from October 1, 1986, through August 31, 1994.

INTERVENTION

Evaluation for and treatment of GERD, LTR, endoscopy, and removal of granulation tissue.

MAIN OUTCOME MEASURES

Successful decannulation and number of endoscopies required to remove laryngeal and tracheal granulation tissue.

RESULTS

Seventy-four patients underwent 82 LTRs. The senior surgeon was blinded to the status of GERD evaluation and treatment. Four groups were identified: 37 patients (40 LTRs) with no preoperative evaluation for GERD; 10 patients (11 LTRs) with normal findings on preoperative evaluation for GERD; seven patients (nine LTRs) with abnormal findings on preoperative evaluation for GERD but who failed to receive appropriate treatment; and 20 patients (22 LTRs) with abnormal findings on preoperative evaluation for GERD who received appropriate therapy. Severity and extent of stenosis as determined by multicentricity of stenosis, type of repair, and duration of stent were similar in the four groups. The effect of GERD and its treatment on the outcome of LTR was measured by the number of endoscopies necessary for removal of granulation tissue following reconstruction and successful decannulation. Statistical analyses indicate that (1) all children do not require preoperative evaluation for GERD; (2) neither the presence of GERD nor its treatment are major factors in determining the outcome of LTR.

CONCLUSION

Preoperative evaluation for GERD and its treatment do not favorably affect the outcome of LTR.

Frequency of variable measurement in 16 pediatric intensive care units: influence on accuracy and potential for bias in severity of illness assessment

OBJECTIVES

We evaluated: a) whether the frequency of variable measurement could influence the performance of the Pediatric Risk of Mortality (PRISM) score; b) whether measurement frequency of physiologic variables varied between individual pediatric intensive care units (ICUs), and c) if so, how much of this variability could be attributed to institution-level and patient-level factors.

DESIGN

Prospective cohort.

SETTING

Sixteen pediatric ICUs, chosen for their diversity.

PATIENTS

Consecutive admissions (n = 5,415).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

First, the measurement frequency of the 14 physiologic variables in the PRISM score was included in the logistic regression model predicting mortality risk. Measurement frequency was not significant, alone or in its interaction with the PRISM score. Second, the presence or absence of measurement of each physiologic variable was included in the logistic model using indicator variables; none was significant. Finally, the contribution of the individual pediatric ICUs and patient factors in explaining the variability in the frequency of physiologic variable measurement were investigated with linear regression analysis. In this analysis, the separation of severity of illness from measurement frequency was accomplished by computing the PRISM score from the first 4 hrs and measurement frequencies from hours 5 through 24. Overall, 70.22% (r2) of the variability of measurement frequency could be explained by the factors included in the linear regression model. The individual ICUs accounted for a total of only 6.23% of the explained variability and no individual hospital accounted for > 1.44% of the variability. Other variables positively correlated with measurement frequency included the presence or absence of a pediatric intensivist, and whether the institution was a children's hospital or not. Variables negatively correlated with measurement frequency included larger ICUs and house officers assigned to the ICU.

CONCLUSIONS

Although measurement frequency is associated with unit-level factors, their contribution to the overall variability is small and unlikely to influence the accuracy or reliability of the PRISM score. It is unlikely that there are routine biases associated with differences in measurement frequency of PRISM variables within the spectrum of care practices that now exist.

Relationship of asymptomatic bacteriuria and renal scarring in children with neuropathic bladders who are practicing clean intermittent catheterization

OBJECTIVE

To determine whether untreated asymptomatic bacteriuria is associated with renal scarring in children with neuropathic bladders managed with clean intermittent catheterization (CIC).

DESIGN

Retrospective study of 207 patients aged 1 to 30 years (mean 11.9 +/- 5.5 years) treated with CIC for a mean duration of 6.6 +/- 3.9 years by the spina bifida program at Children's National Medical Center. All patients were examined for renal scarring with dimercaptosuccinic acid (DMSA) renal scans. Catheterized urine cultures were obtained annually, but bacteriuria ( > 10,000 colony-forming units of a single organism per milliliter) was treated only if the patients had symptoms or if vesicoureteral reflux (VUR) was present.

RESULTS

Of 207 children, 176 (85%) had one or more episodes of untreated asymptomatic bacteriuria and 72 (35%) had one or more febrile episodes associated with positive urine culture results. Biannual DMSA scans detected 54 new scarring episodes in 42 patients. Of newly recognized scars, 55% were preceded within 1 year by a febrile infection, 26% were detected in patients with VUR and asymptomatic bacteriuria, and 19% were detected in new patients during their initial examination. Univariate analysis revealed that new scarring was present in 35 of 176 patients with asymptomatic bacteriuria compared with 7 of 31 patients without (p = 809). Logistic regression analysis revealed that factors associated with scarring were febrile infections (adjusted odds ratio [OR] = 30.6, 95% confidence interval [CI] = 9.8 to 95.8), age more than 20 years (OR = 4.3, CI = 1.01 to 18.5), the presence of bladder trabeculation (OR = 2.7, CI = 1.0 to 7.6), and VUR (OR = 58.8, CI = 6.3 to 547.3), but asymptomatic bacteriuria was not associated with scarring.

CONCLUSION

In the absence of VUR, asymptomatic bacteriuria in patients undergoing CIC is not a significant risk factor for scarring and does not require antibiotic therapy.

Indications for echocardiography in the diagnosis of infective endocarditis in children

The role of transthoracic echocardiography as a diagnostic tool in children suspected of having infective endocarditis (IE) has not been defined. We hypothesized that echocardiography is only useful in children in whom there is high clinical suspicion of IE based on physical examination findings or persistently positive blood cultures. Echocardiographic reports and medical records of all inpatients (n = 133) from 1990 to 1992 who underwent echocardiography for suspected IE were reviewed. Fifty-nine of the 133 patients (44%) identified had either persistently positive blood cultures (n = 48), physical examination findings of IE (n = 20), or both (n = 9). The echocardiogram was positive in 7 of these patients (12%) and negative in all 74 patients without positive physical findings or positive blood cultures (p = 0.003). A new or changing precordial murmur, embolic phenomena, congestive heart failure, mechanical ventilation, and positive blood cultures were predictive of positive echocardiograms for IE by univariate analysis. The presence of fever, immune deficiency, and central lines, alone or in combination, was not predictive of a positive echocardiogram. In the absence of physical findings or persistently positive blood cultures, echocardiography is a low-yield study and is unlikely to aid in the diagnosis of IE in children.