Growth hormone improves clinical status in prepubertal children with cystic fibrosis: results of a randomized controlled trial.

OBJECTIVES: We conducted a 1-year randomized controlled trial to test the hypothesis that growth hormone (GH) improves the clinical status of children with cystic fibrosis. STUDY DESIGN: Nineteen prepubertal children were randomized to control (NonTX, n = 9) or to daily injections of GH (0.3 mg/kg/wk) (GHTX, n = 10) for 1 year. Every 3 months height, weight, and lean tissue mass were measured. Caloric intake, resting energy expenditure, pulmonary function, and respiratory muscle strength were measured every 6 months, as were total number of hospitalizations and courses of outpatient intravenous antibiotics. RESULTS: The GHTX group had significantly greater height, height velocity (NonTX = 3.8 +/- 1.4 cm/y, GHTX = 8.1 +/- 2.4 cm/y; P =.002), weight, weight velocity (NonTX = 2.1 +/- 0.9 kg/y, GHTX = 4.5 +/- 1.1 kg/y; P =.004), and change in lean tissue mass (NonTX = 2.1 +/- 1.6 kg, GHTX = 4.7 +/- 1.7 kg; P =.01) analyzed by the Student t test. The GHTX group had significant improvement in delta forced vital capacity compared with the year before study, and respiratory muscle strength improved. The number of hospitalizations and outpatient intravenous antibiotic courses significantly decreased in the GHTX group but did not change in the NonTX group. No subject had development of cystic fibrosis-related diabetes. CONCLUSIONS: Results of the first randomized controlled trial of GH treatment in cystic fibrosis indicate that GH improves growth and clinical status.

Mechanisms of insulin resistance in cystic fibrosis.

Cystic fibrosis (CF) is associated with a high incidence of diabetes. Studies evaluating causes of CF-related diabetes (CFRD) have consistently documented decreased insulin secretion. In patients with CFRD, insulin sensitivity has been documented to be decreased, but controversy exists in patients with normal or impaired glucose tolerance (IGT). We undertook this study 1) to reexplore insulin sensitivity in patients with IGT and 2) to evaluate potential mechanisms of insulin resistance in CF, including GLUT-4 translocation, elevation of serum cytokines, and free fatty acid (FFA) levels. We recruited nine CF subjects with impaired glucose tolerance (IGTCF) and nine age-, gender-, and body mass index-matched control volunteers. Each underwent a hyperinsulinemic euglycemic clamp (200 mU. m(-2). min(-1)) to measure insulin sensitivity. A muscle biopsy was obtained at maximal insulin stimulation for measure of GLUT-4 translocation with sucrose gradients. An oral glucose tolerance test and National Institutes of Health (NIH) clinical status scores were measured in all volunteers. We also measured tumor necrosis factor (TNF)-alpha levels and FFA in all subjects. Additionally, we report the results of TNF-alpha and FFA in 32 CF patients previously studied by our group. Results were that glucose disposal rate (GDR) was significantly lower in the CFIGT subjects than in controls, indicative of impaired insulin action. GLUT-4 translocation was impaired in CF and correlated with GDR. TNF-alpha levels were higher in all CF subjects than in controls and correlated with GDR. There was no difference in FFA between CF and control subjects. Modified NIH clinical status scores were inversely correlated with GDR and TNF-alpha levels. We conclude that IGTCF patients have decreased peripheral insulin sensitivity. Mechanisms include elevation of TNF-alpha and impaired translocation of GLUT-4.

Growth hormone decreases protein catabolism in children with cystic fibrosis.

Despite aggressive nutritional therapy, low body weight and protein catabolism are common problems in children with cystic fibrosis. Previous studies by our group and others have demonstrated improvement in both height and weight in children with cystic fibrosis who were treated with human recombinant GH, and our group has recently documented improved clinical status and lean tissue mass as well. The purpose of this report is to summarize our findings of the effect of GH on whole body protein kinetics in cystic fibrosis and to relate these findings to changes in TNF-alpha levels. We conducted a 1-yr study of 19 prepubertal children with cystic fibrosis (age 7-12 yr, all <94% of ideal body weight). Ten children were randomly assigned to take daily injections of GH (0.3 mg/kg.wk), and nine were randomly assigned to be controls. Baseline results from the subjects with cystic fibrosis were compared with results obtained from nine age- and gender-matched healthy children. Whole body protein turnover was measured at baseline and every 6 months using the stable isotope [1-(13)C]leucine and mass spectrometric analysis. Leucine rate of appearance, a measure of protein catabolism, was similar in both cystic fibrosis subgroups at baseline and was significantly higher than in the control children without cystic fibrosis. Treatment with GH resulted in a significantly lower leucine rate of appearance, as well as significantly lower leucine oxidation. The rate of protein synthesis, as calculated from these numbers, actually decreased in the cystic fibrosis subgroup. TNF-alpha levels were higher in both cystic fibrosis subgroups than in controls and correlated with leucine rate of appearance. The results of this study suggest that one reason GH improves body weight and lean tissue mass is due to improved whole body protein catabolism and improved efficiency of whole body protein kinetics.

Normal bone mineral density in cystic fibrosis.

BACKGROUND: Osteoporosis has been reported as a complication of cystic fibrosis (CF). AIMS: To measure bone mineral density (BMD) in non-acutely ill adults and bone mineral content (BMC) in children with CF. METHODS: We analysed data from 28 adults and 13 children with CF. Corticosteroid use was minimal for the year prior to study in both groups. Dual x ray absorptiometry was used to measure total body and regional bone mineral density in adults. In children, whole body BMC was measured. Lean tissue mass (LTM) was also measured in all subjects. There were two control groups: A (matched for LTM and height, in addition to age and gender); and B (matched for age and gender only). RESULTS: There was no difference in whole body or regional BMD density between adult CF patients and control A subjects. Both whole body and regional BMD were significantly lower in adult CF patients than in control B subjects. Total body BMD was correlated with body mass index, LTM, and percent fat in both CF and control subjects. There was no significant correlation between total body BMD or regional BMD and either NIH clinical status scores, or pulmonary function tests in adults. There was no difference in total body BMC between CF children and control A subjects. Total body BMC was significantly lower in CF children than in control B subjects. There was no correlation between pulmonary function results and BMC in children. CONCLUSION: Osteopenia and osteoporosis in CF may be caused more by malnutrition and chronic use of intravenous or oral corticosteroids than by a CF related inherent defect in BMD. Appropriate "normal" data should be selected when determining whether or not osteoporosis is present in a CF patient.

Hepatic insulin resistance and defects in substrate utilization in cystic fibrosis.

Patients with cystic fibrosis (CF)-related diabetes (CFRD) have clinical features of both type 1 and type 2 diabetes. Past studies have documented peripheral insulin resistance in CF, and some studies have noted high hepatic glucose production (HGP) in CF patients. We hypothesized that patients with CF, similar to patients with type 2 diabetes, have hepatic insulin resistance. Cystic fibrosis is a catabolic condition, yet the etiology of catabolism is poorly understood. De novo lipogenesis is energy wasteful and precludes ketogenesis. Patients with CFRD rarely develop ketogenesis, despite insulin deficiency. We speculated that CF patients have de novo lipogenesis, and therefore evaluated substrate utilization in CF. Using [6,6-2H2]glucose and a three-step hyperinsulinemic-euglycemic clamp, we measured HGP in 29 adult CF subjects and 18 control volunteers. Using indirect calorimetry, we measured lipid oxidation, oxidative glucose metabolism, and resting energy expenditure at baseline and at high levels of insulin. All subjects were characterized by oral glucose tolerance testing (OGTT) and National Diabetes Data Group criteria. The CF subjects had increased HGP when compared with control subjects (CF, 3.5+/-0.6; control, 2.5+/-0.5 mg x kg(-1) x h(-1); P = 0.002). Baseline HGP correlated with glucose levels obtained 2 h after a glucose load given for OGTT (r = 0.69, P = 0.001). Suppression of HGP by insulin was significantly less in all CF subgroups than in control subjects at peripheral insulin levels of 16 and 29 microU/ml. At peripheral insulin levels of 100 microU/ml and 198 microU/ml, there was no difference in insulin suppression of HGP between CF and control subjects. At baseline, there was no significant difference between control and CF subjects for glucose or lipid oxidation. During maximum insulin stimulation, there was a greater tendency for nonoxidative glucose metabolism in all CF subjects. The CF subjects with abnormal glucose tolerance also had de novo lipogenesis. Our results indicate that CF patients have several defects in substrate utilization, including de novo lipogenesis. Furthermore, these results suggest that high hepatic glucose production and hepatic insulin resistance contribute to the high incidence of abnormal glucose tolerance in CF.

Pharmacokinetics of ibuprofen in patients with cystic fibrosis.

STUDY OBJECTIVES: To determine the pharmacokinetic disposition of high doses of ibuprofen in patients with cystic fibrosis (CF), and to evaluate the reliability of intrapatient dosage adjustments to achieve recommended peak ibuprofen plasma concentrations. DESIGN: First-order absorption, one-compartment model was fit to serial ibuprofen concentration-time data obtained from patients with CF and receiving high doses of ibuprofen 20-30 mg/kg. SETTING: Medical school-affiliated teaching hospital. PATIENTS: Ninety-eight patients with CF (53 males, 45 females; mean age 12.5 yrs). MEASUREMENTS AND MAIN RESULTS: The time to achieve apparent maximum ibuprofen concentration (Tmax) ranged from 1-3 hours, with maximum concentrations ranging from 21-150 microg/ml (mean 83 microg/ml). Apparent ibuprofen clearance (Cl/F) was significantly correlated with age (r2 = 0.43, p<0.0001) and measures of body size (body surface area [BSA] r2 = 0.50, p<0.0001). The Cl/F ranged from 21.1-114.7 ml/min/m2 (mean 45.5 ml/min/m2), a 5-fold difference. The Cl/F normalized to body weight decreased with increasing age (p=0.0009), but when normalized to BSA, there was no age-related change (p=0.65). Apparent volume of distribution was significantly correlated with age (r2 = 0.69, p<0.0001) and measures of body size (BSA r2 = 0.79, p<0.0001). Fourteen patients had ibuprofen dosage adjustments. The Cl/F was not different among doses; however, Tmax differed by an average of 1.25 hours (range 0-2 hrs). CONCLUSION: The substantial variability in ibuprofen disposition and clearance we report is greater than previously described. Individualized dosages and therapeutic drug monitoring may be required to ensure plasma concentrations considered necessary to prevent pulmonary deterioration in patients with CF.

Serum leptin and IGF-I levels in cystic fibrosis.

The role of leptin in states of negative energy balance such as cystic fibrosis (CF) has not been explored. We hypothesized that leptin levels in patients with CF would be low due to correlation with body weight. Despite the importance of IGF-I in normal growth and anabolism, there are few data on IGF-I in CF. We studied 27 CF patients (25+/-5 yrs, 57+/-9 kg, 10M/17F) and 12 control subjects (25+/-4 yrs, 57+/-9 kg, 6M/6F). Each subject underwent analysis of lean body mass (LBM) and percent body fat by dual-energy x-ray absorptiometry (DEXA). Serum leptin and IGF-I levels were measured by radioimmunoassay. Serum leptin levels were similar both in CF and in controls (CF=5.3+/-4.1 ng/ml, C=4.4+/-3.6ng/ml; p=0.3), and there was no difference in percent body fat between the two groups (CF=26+/-13%, C=21+/-7%; p=0.3). Leptin levels were significantly lower in CF males than females corresponding to lower fat levels in males in both CF and controls. Leptin levels were positively correlated with percent body fat both in CF and controls (CF: r=0.8; p=0.01, CONTROL: r=0.8; p =0.2). Serum IGF-I levels were significantly lower in CF patients than in controls (CF=1.13+/-0.41 ng/ml, C=6.72+/-3.62 ng/ml; p=<0.01). We conclude that the physiological regulation of leptin is maintained in relation to body fat even in chronic illness and that the negative energy balance in CF is not caused by high leptin levels.

Proteolysis associated with insulin resistance in cystic fibrosis.

OBJECTIVE: We hypothesized that patients with cystic fibrosis (CF) have higher rates of protein breakdown than normal volunteers and that the infusion of insulin would result in less suppression of proteolysis. Methods. Using [1-C]leucine and a three-step hyperinsulinemic euglycemic clamp, we measured rates of leucine appearance in 29 adult CF patients and 18 matched-control volunteers. The CF patients were characterized by oral glucose tolerance testing and clinical status scoring. RESULTS: The CF patients had significantly increased proteolysis when compared with that of controls (CF, 123 +/- 28 micromol/kg/h; controls, 71 +/- 15 micromol/kg/h) and rates of proteolysis were significantly different between CF patients with impaired glucose tolerance and diabetes and those CF patients with normal glucose tolerance. Suppression of proteolysis by insulin was less in all CF subgroups than in the controls at peripheral insulin levels of 16 and 29 microU/mL. At peripheral insulin levels of 100 microU/mL, there was no difference in insulin suppression of proteolysis between CF patients and controls. Importantly, basal rates of proteolysis had an inverse relationship with clinical status in CF patients (r = -.76). CONCLUSIONS: Our findings indicate that proteolysis is higher in adult CF patients than in controls and that CF patients exhibit resistance to the anabolic effects of insulin on proteolysis. Most significantly, our findings indicate that basal rates of proteolysis inversely correlate with clinical status in CF.

Self-management of cystic fibrosis: short-term outcomes of the Cystic Fibrosis Family Education Program.

This study tested the efficacy of the Cystic Fibrosis Family Education Program, a cystic fibrosis self-management program, on improving participants' knowledge, self-efficacy, self-management behavior, health, and quality of life. A quasi-experimental pretest-posttest nonequivalent comparison group design was employed. Participants made up 104 patient-primary caregiver dyads from the intervention site cystic fibrosis center and 95 from the usual care comparison center. The intervention, a self-paced print curriculum based on social cognitive theory, targeted behavioral capability, self-efficacy, and outcome expectations and was implemented as an integral part of medical care. Parents, early childhood, middle childhood, and adolescents received separate materials on respiratory, nutrition and malabsorption, communication, and coping issues. Significant intervention effects were found on the knowledge scores for caregivers, adolescents, and children; caregiver and adolescent total self-management scores; Child Behavior Checklist total score; one parent coping scale score; the modified NIH score; NIH pulmonary factor 1; and the Brasfield total score. Significant interaction effects were evident in the self-efficacy scores for caregivers and children.

Insulin resistance is associated with decreased clinical status in cystic fibrosis.

Patients with cystic fibrosis (CF) frequently have impaired glucose tolerance and progression to diabetes (DM) with clinical features of both insulin-dependent and non-insulin-dependent diabetes. One feature of non-insulin-dependent DM is decreased insulin sensitivity, also known as insulin resistance. The goal of this study was to determine whether patients with CF exhibit insulin resistance and to determine the potential effect of insulin resistance on clinical status. We also sought to determine whether insulin resistance is associated with a specific CF genotype. We studied 18 patients with CF (8 with normal glucose tolerance, 5 with impaired glucose tolerance, 5 with DM), and 20 lean control subjects matched for age, weight, and sex. All control subjects had normal glucose tolerance. The clinical status for each CF patients was determined according to a modified National Institutes of Health scoring system. Each subject underwent a three-step hyperinsulinemic euglycemic clamp (insulin doses of 10, 40, 120 mU/m2 per minute). Results from the 120 mU/m2 per minute infusion defined maximal glucose disposal rate (defined in milligrams per kilogram body weight per minute) at steady state with peripheral insulin levels 195 +/- 20 mU/ml. Subjects with CF demonstrated insulin resistance (control subjects = 13.6 +/- 1.1, patients with CF = 10.2 +/- 1.6 mg/kg per minute; p = 0.003). When each subgroup was compared separately with control subjects, all subgroups were statistically insulin resistant (glucose disposal rate, patients with CF and normal glucose tolerance = 10.8; those with impaired glucose tolerance = 8.4; those with DM = 10.1 mg/kg per minute), and the patients with CF with impaired glucose tolerance were the most insulin resistant. When plotted versus glucose disposal rate, a striking positive correlation between worsened clinical status and insulin resistance (r = 0.85) is demonstrated. Furthermore, there is no correlation between insulin resistance and fasting blood glucose, subject age, or percent ideal body weight (all r values not significant). In conclusion, patients with CF exhibit insulin resistance that is associated with worsened clinical status. We believe it is the combination of insulin resistance and decreased insulin secretion that is responsible for the high incidence of CF-related diabetes.

Pediatric lung abscess: clinical management and outcome.

Pulmonary abscess is an infrequent but significant problem in children. We retrospectively reviewed the charts of 45 children with documented lung abscesses admitted and treated at Texas Children's Hospital, Houston, over the 11-year period from January, 1982, to December, 1993, and report their presenting symptoms, bacteriology, clinical management and outcome.

Self-management of cystic fibrosis: a structural model for educational and behavioral variables.

One hundred and ninety-nine patients and their primary caregivers at two metropolitan cystic fibrosis centers participated in a clinical trial to evaluate the effectiveness of a health education program designed to help improve self-management skills for the care of CF. The baseline data from the study was used to test a structural model that hypothesized the relationship between educational, behavioral, and health status variables. Controlling for the effects of all other variables, including demographic, self-efficacy (confidence in being able to perform a behavior) was the most important educational factor predicting self-management behavior for monitoring and treating respiratory problems. Knowledge about the management of CF was only related to the ability of caretakers to apply coping skills to problems associated with CF. The more caretakers reported performing monitoring behaviors the more likely they were to report performing self-management treatment behaviors. The findings suggest that educational interventions that focus on increased knowledge alone are not likely to be effective in improving self-management behavior for CF. Based on the structural model analyses, it is recommended that educational programs for CF patients and families address increased self-efficacy and improved monitoring skills to influence the improvement of self-management treatment for CF.

Measuring clinical status in cystic fibrosis: internal validity and reliability of a modified NIH score.

We examined measurement properties of the NIH Clinical Score for Cystic Fibrosis (CF) as an index of disease status. This score is being employed as a research tool for defining study populations and as an outcome measure, yet there are no published data on its reliability or how its items contribute to the overall measure of disease status. Criteria for scoring some items in the original index lack specificity. In this study, we used a modified score to have more clearly specified criteria, while retaining the original weightings and structure. For 200 patients with CF in two centers, we analyzed the total NIH Score and its subscores for internal consistency, interrater reliability, and factor analysis. Internal consistency indicates how inter-related the items are. The pulmonary subscore and overall score had fairly high internal consistency. However, the general subscore had low internal consistency, suggesting that the items are not measuring a single element of disease status and should not be added. Factor analysis provides additional information on the underlying structure and relationships among items. Five factors (groups of items) were identified accounting for 85% of the consistent variance of 14 items. These factors were designated by items accounting for most of their variance: general pulmonary, weight, disability, psychosocial, and acute infiltrate. While inter-rater reliability for the overall index was high, individual items showed less agreement. The results indicate that most of the variability in the NIH Score is attributable to pulmonary items in the first factor. The analyses suggest a new scoring structure for the NIH Score; the general subscore items do not contribute to the reliability or account for significant variance. Therefore, they will likely require further refinement or be eliminated.

Performance objectives for the self-management of cystic fibrosis.

Performance objectives for the self-management of cystic fibrosis (CF) were developed and subjected to a two-stage content validation. A multidisciplinary team of health care professionals generated a list of 149 medical and adjustment performance objectives. Behaviors included monitoring symptoms and judging their significance, treating symptoms and communicating with health care providers about symptoms and treatment plans. In the first stage a panel of experts in the medical and behavioral aspects of CF rated each behavior. In general, the eleven panelists rated the 149 behaviors as somewhat important or important (mean 2.6, S.D. 0.17, on a 3-point scale). In the second stage, 84 of 155 CF center directors rated all behaviors as somewhat important or important (mean 2.9, S.D. 0.23). Specific behaviors related to medical regimens were more consistently rated as important than were those related to psychosocial adjustment. The performance objectives provide a framework for developing and evaluating health education programs for the self-management of CF in order to promote optimum health and adjustment.

Pharmacokinetics of cefepime in cystic fibrosis patients.

The purposes of this study were to determine and compare the single- and multiple-dose pharmacokinetics of cefepime in patients with and without cystic fibrosis. Twelve patients with cystic fibrosis hospitalized for treatment of acute pulmonary exacerbations were studied. In addition, pharmacokinetic data for seven of the patients with cystic fibrosis were compared with those for seven age-matched control patients. The cefepime dose was 50 mg/kg of body weight (maximum, 2 g) administered as a 30-min intravenous infusion every 8 h for a minimum of 8 days. Serial plasma and urine samples, obtained after the first and last doses, were analyzed for cefepime content by a validated high-pressure liquid chromatographic assay. By standard noncompartmental analysis, the pharmacokinetic parameters ascertained were area under the concentration in plasma-time curve, elimination half-life, total body clearance, renal clearance, and volume of distribution at steady state. In addition, the maximum concentration in plasma was recorded. Mean (+/- standard deviation) results of the first dose analysis in patients with cystic fibrosis were as follows: maximum concentration in plasma, 142.6 (+/- 26.07) micrograms/ml; area under the concentration in plasma-time curve, 265.3 (+/- 114.31) micrograms.h/ml; elimination half-life, 1.8 (+/- 0.53) h; total body clearance, 127.2 (+/- 50.94) ml/min; renal clearance, 91.1 (+/- 38.86) ml/min/kg; volume of distribution at steady state, 14.1 (+/- 4.31) liters. Analysis for the last dose in patients with cystic fibrosis did not vary appreciably from these values, nor did those from the controls. Thus, it appears that the first-dose pharmacokinetics of cefepime are predictive of those at steady state. In order to consistently exceed the MIC for Pseudomonas aeruginosa for the entire dosing interval in patients with cystic fibrosis, a higher dose and/or different dosing interval compared with those used in this study may be necessary.

Toxicity of colistin in cystic fibrosis patients.

Pulmonary exacerbations of cystic fibrosis associated with strains of Pseudomonas aeruginosa that are resistant to multiple antibiotics are becoming increasingly common. The search for treatment alternatives continues and may include the reexamination of older antibiotics. Colistin sulfate is a polypeptide antibiotic with good activity against P. aeruginosa. Although its use was largely discontinued in the early 1970s because of reports of frequent renal and neurologic toxicity, intravenous colistin is often prescribed at our institution for patients with P. aeruginosa resistant to multiple-drug therapy. We prospectively monitored 19 patients during 21 courses of colistin therapy to identify the character and incidence of this agent's toxicity. Only one case of renal toxicity occurred. Six cases of neurotoxicity occurred, which were characterized by perioral paresthesia, ataxia, or both. The rate of intolerable renal adverse effects secondary to colistin therapy was appreciably lower among these patients than that reported previously for other patients. It appears that intravenous colistin can be considered for cystic fibrosis patients with strains of P. aeruginosa that are resistant to more commonly used antibiotics.

The development of psychiatric symptomatology in patients with cystic fibrosis.

Psychiatric symptomatology was compared in 61 cystic fibrosis patients, ages 8 to 15 years, and 36 cystic fibrosis patients, ages 16 to 40 years. When the prevalence of psychiatric symptomatology was compared in the two groups, a developmental pattern emerged: Symptoms of depression and anxiety were more frequent in the older group, while symptoms associated with eating disorders were more frequent in the younger group. Although duration of illness was longer and severity of illness was greater in the older group, these factors were largely unrelated to psychiatric symptomatology in either group. It is hypothesized that younger patients may express psychological distress through less direct means than older patients.

Development of a health education program to promote the self-management of cystic fibrosis.

The creative challenge of health education for chronic illnesses is the translation of theory-based intervention methods into practical strategies that can be organized into a logical series of learning activities to influence changes in environmental, cognitive, or behavioral factors. A case example describing the development and implementation of a comprehensive health-education intervention for the self-management of cystic fibrosis (CF) is presented. The design of intervention strategies began with an assessment of the educational needs for self-management of CF, followed by specification and validation of particular self-management behaviors. Behavioral and learning objectives then were formulated for each of the self-management behaviors. Constructs from social learning theory considered to be important influences on specified self-management behaviors in CF were identified. Taking into consideration the learning needs of the target population and the practical constraints of the system for providing health care, various intervention methods then were devised based on social learning theory. Lastly, the intervention methods chosen were translated into strategies organized into a series of practical learning activities for CF patients and their families. The process described here should prove useful to others who are planning and developing comprehensive health education programs for self-management of chronic illnesses.