Use of guidelines and risk stratification in acute exacerbations of chronic obstructive pulmonary disease

Guidelines have been developed to simplify the antimicrobial treatment decision for patients with acute exacerbations of chronic obstructive lung disease. Approximately half of these patients will have a demonstrable bacterial infection and antibiotics have been demonstrated to shorten the clinical illness and prevent significant deterioration. Patients can be stratified by the risk of treatment failure with usual first-line antimicrobial agents. Patients presenting with worsening dyspnea, increased sputum volume and purulence should be offered antimicrobial therapy. In the presence of significant impairment of lung function (FEVI 50% predicted), frequent exacerbations, significant comorbidity, malnutrition, chronic corticosteroid administration and long duration of disease, should be treated with more aggressive therapy such as with a fluoroquinolone, amoxicillin-clavulanate, or a second or third generation cephalosporin or second generation macrolide. In the absence of these risk factors, first-line agents such as amoxicillin appear adequate. Patients with chronic suppurative airway disease (mainly bronchiectasis) should be treated with an antipseudomonal fluoroquinolone if P. aeruginosa is identified in pulmonary secretions. More prospective randomized trial are warranted to validate this approach.

Patient stratification in the management of acute bacterial exacerbation of chronic bronchitis: the role of levofloxacin 750 mg

This is the first prospective clinical trial in which patients with acute bacterial exacerbation of chronic bronchitis have been stratified by degree of underlying illness. Uncomplicated patients were randomised to levofloxacin 750 mg once daily (q.d.) for 3 days or azithromycin q.d. for 5 days. Complicated patients were randomised to levofloxacin 750 mg q.d. for 5 days or amoxicillin 875 mg/clavulanate 125 mg twice daily for 10 days. Regardless of therapy, complicated patients demonstrated lower clinical and microbiological success than uncomplicated patients. Clinical success for clinically evaluable patients was similar for levofloxacin and azithromycin (93.0 versus 90.1%, respectively), and levofloxacin and amoxicillin/clavulanate (79.2 versus 81.7%, respectively). For microbiologically evaluable patients, clinical response to levofloxacin for 3 days was superior to azithromycin for 5 days (96.3 versus 87.4%, respectively), and levofloxacin for 5 days was similar to amoxicillin/clavulanate for 10 days (81.4 versus 80.9%, respectively). Microbiological eradication was superior for levofloxacin for 3 days compared with azithromycin for 5 days (93.8 versus 82.8%, respectively), and similar for levofloxacin and amoxicillin/clavulanate for 10 days (81.4 versus 79.8%, respectively). In conclusion, levofloxacin 750 mg for 3 days was comparable to azithromycin for 5 days for uncomplicated patients with acute bacterial exacerbation of chronic bronchitis, while 5 days of 750 mg levofloxacin was comparable to 10 days of amoxicillin/clavulanate for complicated acute bacterial exacerbation of chronic bronchitis.

The chronic obstructive pulmonary disease exacerbation

Chronic obstructive pulmonary disease is the only leading cause of death with a rising prevalence. The medical and economic costs arising from acute exacerbations of COPD are therefore expected to increase over the coming years. Although exacerbations may be initiated by multiple factors, the most common identifiable associations are with bacterial and viral infections. These are associated with approximately 50% to 70% and 20% to 30% of COPD exacerbations, respectively. In addition to smoking cessation, annual influenza vaccination is the most important method for preventing exacerbations. Controlled O2 is the most important intervention for patients with acute hypoxic respiratory failure. Evidence from randomized, controlled trials justifies the use of corticosteroids, bronchodilators (but not theophylline), noninvasive positive-pressure ventilation (in selected patients), and antibiotics, particularly for severe exacerbations. Antibiotics should be chosen according to the patient's risk for treatment failure and the potential for antibiotic resistance. In the acute setting, combined treatment with beta-agonist and anticholinergic bronchodilators is reasonable but not supported by randomized controlled studies. Physicians should identify and, when possible, correct malnutrition. Chest physiotherapy has no proven role in the management of acute exacerbations.

Summary of Canadian guidelines for the initial management of community-acquired pneumonia: an evidence-based update by the Canadian Infectious Disease Society and the Canadian Thoracic Society

Community-acquired pneumonia (CAP) is a serious illness with a significant impact on individual patients and society as a whole. Over the past several years, there have been significant advances in the knowledge and understanding of the etiology of the disease, and an appreciation of problems such as mixed infections and increasing antimicrobial resistance. The development of additional fluoroquinolone agents with enhanced activity against Streptococcus pneumoniae has been important as well.It was decided that the time had come to update and modify the previous CAP guidelines, which were published in 1993. The current guidelines represent a joint effort by the Canadian Infectious Diseases Society and the Canadian Thoracic Society, and they address the etiology, diagnosis and initial management of CAP. The diagnostic section is based on the site of care, and the treatment section is organized according to whether one is dealing with outpatients, inpatients or nursing home patients.

Summary of Canadian guidelines for the initial management of community-acquired pneumonia: an evidence-based update by the Canadian Infectious Disease Society and the Canadian Thoracic Society

Community-acquired pneumonia (CAP) is a serious illness with a significant impact on individual patients and society as a whole. Over the past several years, there have been significant advances in our knowledge and understanding of the etiology of the disease, and an appreciation of problems such as mixed infections and increasing antimicrobial resistance. The development of additional fluoroquinolone agents with enhanced activity against Streptococcus pneumoniae has been important as well. It was decided that the time had come to update and modify the previous CAP guidelines, which were published in 1993. The current guidelines represent a joint effort by the Canadian Infectious Disease Society and the Canadian Thoracic Society, and they address the etiology, diagnosis and initial management of CAP. The diagnostic section is based on the site of care, and the treatment section is organized according to whether one is dealing with outpatients, inpatients or nursing home patients.

Cost-effective therapy for acute exacerbations of chronic bronchitis

Pharmacoeconomic analysis involves the measurement of a ratio determining the extra costs required to achieve an additional unit of clinical benefit. Various techniques including modeling studies, retrospective analysis of databases, "piggy-back" economic analysis of prospective randomized clinical trials, and prospective randomized pharmacoeconomic trials have been developed to aid in economic and health decisions. In acute exacerbations of chronic obstructive pulmonary disease, it is possible to identify a group of patients that are at high risk of treatment failure from routine antimicrobial therapy, hospitalization, respiratory failure, and death. The cost of therapy for this relatively small group of patients is extraordinarily high. Data from a variety of approaches have suggested that aggressive antimicrobial therapy may lead to improved outcomes in these patients. The corollary is that aggressive therapy directed toward patients with either acute bronchitis (mainly a viral infection) or exacerbations of trivial chronic obstructive lung disease leads to emergence of resistance and increased costs.

Treatment of community-acquired pneumonia in the elderly: the role of cefepime, a fourth-generation cephalosporin

In a prospective, multicentre double-blind trial, 151 patients over the age of 65 years were randomly assigned to receive either cefepime 2 g every 12 h for a minimum of 3 days and up to 14 days or ceftriaxone 1 g every 12 h for a minimum of 3 days and up to 14 days. Antibiotics were maintained until 48 h after fever had resolved; no other antibiotics were permitted. The average age in each group exceeded 77 years and significant co-morbidity was found in the majority of patients. The mean total duration of therapy was 5.8+/-2.4 days for the cefepime group and 6.7+/-2.7 days for the ceftriaxone group (P = 0.06). The clinical success rate at the end of therapy was 79.1% with cefepime and 75.4% with ceftriaxone (P = 0.62). At the end of follow-up, 91.7% of the cefepime-treated patients and 86.5% of the ceftriaxone patients had a satisfactory clinical response (P = 0.38). In 35 bacteriological evaluable patients, potential pathogens were eradicated in all but one patient receiving cefepime. Seven patients in each group died during the study period but in each case the death was unrelated to study drug. The commonest side-effect was diarrhoea (cefepime, five patients; ceftriaxone, two patients). The clinical and microbiological efficacy of cefepime is similar to that of ceftriaxone in elderly patients with community-acquired pneumonia requiring hospitalization. Cefepime is an appropriate choice for the treatment of community-acquired respiratory tract infections in the elderly.

Management of acute exacerbation of chronic bronchitis

In chronic bronchitis, a common respiratory illness marked by chronic productive cough and caused largely by cigarette smoking, bacterial exacerbations are thought to be a common cause of progressive airway damage. Common bacterial pathogens, found in 50% to 60% of episodes, include Haemophilus influenzae (the most common), as well as Haemophilus parainfluenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Bacterial resistance to antibiotics, especially beta-lactam drugs such as amoxicillin, is increasingly common in these pathogens. In this illness, clinical risk stratification based on age, history and comorbidity is an important strategy. Patients in the lowest risk group likely have viral infections and require no specific treatment. Patients in the higher risk groups require aggressive treatment to avoid treatment failure, which can lead to prolonged hospitalization and complications. Preventive therapies (smoking cessation and influenza vaccination) are worthwhile measures for these patients.

Airway infection

Bronchitis in its acute and chronic forms with recurrent acute exacerbations is one of the most common reasons for physician visits, accounting for a significant cost to the health-care system, lost work days, and increased morbidity and mortality. Smoking and recurrent lower respiratory tract infections are major risk factors for chronic bronchitis. Therefore, smoking cessation and vaccination strategies are cornerstones of management in terms of halting disease progression and reducing the frequency of infectious exacerbations. Bacterial infection is the main culprit in acute flares of the disease. Routine antimicrobial therapy fails in a significant number of patients, and therapeutic failures lead to increased costs. Several stratification schemes have been proposed to improve initial antimicrobial selection. These schemes identify patient's age, severity of underlying pulmonary dysfunction, frequency of exacerbations, and the presence of comorbid illnesses as predictors for likely pathogens and to guide antimicrobial selection. This approach may reduce the risk for treatment failure, which would have significant medical and economic implications. Improved understanding of the roles of airway inflammation and infection in the pathogenesis of progressive airway disease, in addition to future studies examining the efficacy of newer classes of antimicrobials, should guide physicians to target early and effective treatment to high-risk patients.

The value of antibiotics and the outcomes of antibiotic therapy in exacerbations of COPD

COPD is the fifth leading cause of death in the United States, and acute respiratory infections account for a significant proportion of all primary care visits. Approximately one half of all exacerbations of COPD can be attributed to bacterial infection, and antibiotic therapy has been demonstrated to improve clinical outcomes and hasten clinical and physiologic recovery. The major pathogen continues to be Haemophilus influenzae, and resistance to beta-lactam antibiotics such as ampicillin can be expected in 20 to 40% of isolated strains. Certain high-risk patients, in whom the cost of clinical treatment failure is high, can be identified by simple clinical criteria. Patients with significant cardiopulmonary comorbidity, frequent purulent exacerbations of COPD, advanced age, generalized debility, malnutrition, chronic corticosteroid administration, long duration of COPD, and severe underlying lung function tend to fail therapy with older drugs, such as ampicillin, and early relapse can be expected. Treatment directed toward resistant pathogens with potent bactericidal drugs may be expected to lead to improved clinical outcomes and overall lower costs, particularly if hospital admissions and respiratory failure can be prevented. Future studies examining the role of antibiotics should enroll these high-risk patients to determine if new therapies have significant clinical, quality-of-life, and economic advantages over older agents.

How do we achieve cost-effective options in lower respiratory tract infection therapy?

Acute bronchitis and acute exacerbations of chronic bronchitis, common illnesses encountered by general and family physicians, account for approximately 14 million physician visits per year. The pattern of antibiotic prescribing for these infections varies from country to country, but there is no clear rationale for these antimicrobial choices. A recent meta-analysis of all randomized, placebo-controlled trials of patients treated with antibiotics for acute exacerbations of chronic bronchitis concluded that a small but statistically significant improvement could be expected in antibiotic-treated patients. Haemophilus influenzae is the most commonly isolated organism from sputum in patients with acute exacerbations of chronic obstructive lung disease but other Haemophilus species, Streptococcus pneumoniae, and Moraxella catarrhalis may also be found. High-risk patients can be defined as being elderly, with significant impairment of lung function, having poor performance status with other comorbid conditions, having frequent exacerbations, and often requiring oral corticosteroid medication. Well-defined clinical trials measure efficacy of a drug but not the effectiveness in a real world situation. Future studies of new antimicrobials should examine their efficacy in patients with an increased risk of true bacterial infection.

What new antibiotics to offer in the outpatient setting

The treatment of community-acquired pneumonia is empiric. Guidelines have been developed to assist the clinician in selecting antibiotics to cover the likely pathogens. Given the difficulty of predicting an etiologic agent from patient characteristics, radiologic findings, and laboratory studies, initial regimens recommend broad-spectrum coverage. In some circumstances, two antibiotics may be required. The prevalence of resistant organisms is increasing and must be considered when prescribing treatment. Patient compliance is essential for successful therapy but diminishes with inconvenient dosing schedules and with poorly tolerated medicines. A number of novel antimicrobials have either been just launched or are in the late stages of development. Most have been developed in an attempt to address the above concerns. This article focuses on the new oral cephalosporins, macrolides, and fluoroquinolones, and discusses the place of each in the therapy of community-acquired pneumonia.

The role of fluoroquinolones in respiratory tract infections

Quinolones, because of their excellent pharmacokinetic properties, high antimicrobial activity and low incidence of side-effects, have been broadly accepted for the treatment of many infections. Because of perceived limitations against Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus there has been some reluctance to use them for respiratory tract infections. Ciprofloxacin is the drug of choice for malignant external otitis, a disease caused by Pseudomonas aeruginosa, and it has also been used successfully for the treatment of chronic otitis media where P. aeruginosa, S. aureus and Proteus mirabilis are main pathogens. Quinolones are as efficacious as the beta-lactams and cephalosporins in the treatment of acute sinusitis but most clinicians will not use quinolones for this indication. Acute bacterial exacerbations of chronic bronchitis respond to antimicrobial therapy and quinolones have been demonstrated to be at least equivalent to second- and third-generation cephalosporins, co-amoxiclav and beta-lactams. Recently published guidelines in Canada, USA and Great Britain do not recommend quinolones for the treatment of community-acquired pneumonia except for patients with life-threatening disease requiring ICU admission. A quinolone in combination with an aminoglycoside and macrolide is a regimen that can be used as initial empirical therapy until the results of microbiological investigations are available. For patients with severe hospital-acquired pneumonia, where multiply resistant aerobic Gram-negative bacilli are a consideration, a quinolone in combination with an antipseudomonal penicillin or cephalosporin has been recommended. In the absence of P. aeruginosa, monotherapy with a quinolone is at least as effective as third-generation cephalosporins or imipenem. Early switch therapy from parenteral antibiotics to oral fluoroquinolone has been demonstrated to be very successful.

Vascular endothelial growth factor expression is higher in differentiated thyroid cancer than in normal or benign thyroid

Vascular endothelial growth factor (VEGF) is an angiogenic factor, and its expression has been rarely demonstrated in thyroid tumors. We, therefore, investigated the expression of VEGF messenger RNA (mRNA) and production of VEGF protein in cell lines from human primary and metastatic follicular (FTC-133, FTC-236, and FTC-238), papillary (TPC-1), Hürthle cell (XTC-1), and medullary thyroid cancers (MTC-1.1 and MTC-2.2), and in human thyroid tissues (papillary, follicular, medullary, and Hürthle cell cancers, follicular adenomas, and Graves' thyroid tissue) by Northern blot, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) studies. All thyroid cell lines expressed a 4.2-kilobase VEGF mRNA. The VEGF mRNA levels were higher in the thyroid cancer cell lines than in primary cultures of normal thyroid cells, and higher in thyroid cancers of follicular than those of parafollicular cell origin. The VEGF mRNA levels were similar in primary and metastatic thyroid tumors. Immunohistochemical staining and Northern blot analysis of the cell lines correlated positively, thus thyroid cancer cell lines stained more intensely than normal thyroid cells and follicular tumor cells more intensely than parafollicular tumor cells. Again, no difference was noted in VEGF staining between primary and metastatic thyroid tumors. Deparafinized sections of papillary, follicular, and Hürthle cell cancers also stained much stronger than those of medullary thyroid cancers, benign, or hyperplastic (Graves' disease) thyroid tissue. Thyroid cancer cell lines (XTC-1 > TPC-1 > FTC-133 > MTC-1.1) also secreted more VEGF protein as measured by ELISA than did normal thyroid cells. VEGF secretion of cell lines derived from primary and metastatic thyroid tumors were similar. VEGF mRNA is therefore expressed, and VEGF protein is secreted by normal, hyperplastic, and neoplastic thyroid tissues. The higher levels of VEGF expression in differentiated thyroid cancers of follicular cell origin suggests a role in oncogenesis.

Acute exacerbations of chronic bronchitis

Not every patient with bronchitis needs to be treated with an antibiotic. When treatment is indicated, however, the regimen should be selected carefully. A simple four-part disease classification scheme serves as a practical aid for initial assessment of the patient and as a guideline for choosing therapy.

Critical care management of the obstetric patient

PURPOSE

To review a series of critically ill obstetric patients admitted to a general intensive care unit in a Canadian centre, to assess the spectrum of diseases, interventions required and outcome.

METHODS

A retrospective chart review was performed of obstetric patients admitted to the intensive care unit of an academic hospital with a high-risk obstetric service, during a five-year period. Data obtained included the admission diagnosis, ICU course and outcome. Daily APACHE II and TISS scores were recorded.

RESULTS

Sixty-five obstetric patients, representing 0.26% of deliveries in this hospital, were admitted to the ICU during the study period. All had received prenatal care. Admission diagnoses included obstetric (71%) and non-obstetric (29%) complications. The mean APACHE II score was 6.8 +/- 4.2 and mean TISS score was 24 +/- 8.1. Twenty-seven patients (42%) required mechanical ventilation. No maternal mortality occurred and the perinatal mortality rate was 11%.

CONCLUSIONS

A small proportion of obstetric patients develop complications requiring ICU admission. The outcome in this study was excellent, in contrast to that reported in other published studies with similar ICU admission rates. The universal availability of prenatal care may be an important factor in the outcome of this group of patients. The lack of a specific severity of illness scoring system for the pregnant patient makes comparison of case series difficult.

Hurthle Cell Carcinoma

BACKGROUND: Hurthle cell carcinoma represents approximately 3% of all differentiated thyroid cancers. The terminology is often confusing, and discrimination between Hurthle cell carcinoma and benign Hurthle cell tumors can be unclear. Thus, optimal treatment of patients with these diseases remains unsettled. METHODS: The authors reviewed published evidence on the presentation, biologic behavior, and treatment outcomes for this disease. In addition, they summarized their experience involving a series of 14 patients with Hurthle cell carcinoma. RESULTS: Hurthle cell carcinoma generally produces thyroglobulin and rarely takes up radioactive iodine. It is frequently bilateral or multifocal within the thyroid gland and often presents with local invasion. Hurthle cell carcinoma is associated with a high rate of locoregional recurrence and significant mortality. CONCLUSIONS: The authors advocate total thyroidectomy with central neck dissection as the therapy of choice for patients with Hurthle cell carcinoma.

Immunocytochemical detection of p53 in human thyroid carcinomas is associated with mutation and immortalization of cell lines

Mutations in the tumor suppressor gene p53 are the most-common mutations found in human cancers. In thyroid cancers, p53 mutations generally are found only in poorly differentiated and undifferentiated tumors and in cell lines. To determine the prevalence of p53 mutations in thyroid neoplasms and thyroid cell lines, we screened 58 thyroid tissues and 3 thyroid cell lines, p53 primers bracketing exons 4, 5/6, 7, and 8 were used to amplify genomic DNA using the PCR. Mutations were screened by denaturing gradient gel electrophoresis and confirmed by sequencing. The two papillary thyroid cancer cell lines and the follicular thyroid carcinoma cell line (positive control) had transitions (CGT->CAT) in exon 8, codon 273, resulting in the replacement of arginine with histidine. No normal thyroid tissues or primary tumors from which the cell lines were derived demonstrated exon 8 mutations, using this technique. p53 immunocytochemistry demonstrated a progression of p53 immunopositivity between synchronous and metachronous neoplasms, paralleling the neoplastic progression from a benign adenoma to primary carcinoma, regional, and distant metastasis and ultimately, the cell lines, where intense immunopositivity is noted. In addition, fluorescence in situ hybridization, using probes specific for the p53 locus, revealed the presence of 3 homologues of p53 in the follicular cell line and 2 homologues in the papillary and Hürthle cell lines. These results suggest that a point mutation present in a small number of original tumor cells and amplification of the mutant allele may be responsible for immortalizing well-differentiated thyroid cancer cells into cell lines.

Familial nonmedullary thyroid cancer. An emerging entity that warrants aggressive treatment

OBJECTIVE

To determine whether familial nonmedullary thyroid carcinoma behaves like sporadic carcinoma of follicular cell origin.

DESIGN

Retrospective review.

SETTING

University medical center.

PATIENTS

Fourteen patients were treated for familial nonmedullary thyroid carcinoma between 1980 and 1994. Thirteen families were identified, with 30 affected individuals.

INTERVENTIONS

Patients were treated with total or completion total thyroidectomy. Thirteen additional operations were performed to control recurrent disease.

MAIN OUTCOME MEASURES

Stage, recurrence, and survival. Patients were followed up for a mean of 6.5 years.

RESULTS

In our 14 patients, 13 tumors were multifocal, and six of these were bilateral. The incidences of lymph node metastasis and local invasion were both 57% (n = 8). Seven patients (50%) had recurrences during follow-up.

CONCLUSIONS

Familial nonmedullary thyroid carcinoma has a high incidence of multifocality and invasion and a high rate of local recurrence. Aggressive initial treatment and careful follow-up seem to be indicated.

Thyroid growth factors, signal transduction pathways, and oncogenes

Growth of thyroid cancer cells is stimulated by various growth factors via signal transduction pathways. TSH, EGF, IGF, and TGF-alpha stimulate and TGF-beta inhibits thyroid cell growth. TSH stimulates thyroid cells via both the adenylate cyclase-PKA and the PLC-PKC-Ca signal transduction pathways. TSH-r, ras, gsp, ret, trk, and myc are oncogenes that are activated in some thyroid neoplasms. P53 and RB are tumor suppressor genes that are inactivated in some thyroid cancers.

Immunoprecipitation isolates multiple TSH receptor forms from human thyroid tissue

Attempts to purify the thyroid-stimulating hormone receptor (TSHR) have been complicated by its susceptibility to proteolysis and its low level of expression in thyrocytes and many transfected cells. Controversy exists over its size and structure. Multiple, single-polypeptide forms of the TSHR (230, 187, and 95-100 kDa) have been recently identified in immunoblots of crude plasma membranes prepared from COS-7 cells transfected with rat or human cDNA, but the relationship of these receptor species to the TSHR in human thyroid tissue has been heretofore unknown. We have developed a technique for immunoprecipitation of the TSHR which employed IgG purified from a polyclonal rabbit antiserum to TSHR residues 352-366. We have used immunoprecipitation to isolate the previously characterized 95-100 kDa TSH-holoreceptor, 187 kDa intermediate, and 230 kDa precursor forms of the TSHR from plasma membrane prepared from transfected COS-7 cells and human thyroid tissue. The presence of all three forms was not altered by the addition of reducing agent to the sample buffer, demonstrating the single polypeptide structure of the TSHR. This is, to our knowledge, the first report of the purification from transfected COS-7 cells of these TSHR species identified previously only in immunoblots of crude plasma membrane, and the first report of the identification by any means of these TSHR forms in human thyroid tissue. The isolation of TSHR from human thyroid tissue requires confirmation by direct means, but promises to make the receptor available in a soluble form for studies of its structure and function.

Radioiodine-associated thyroid cancers

Numerous investigations document that exposure to low dose external therapeutic radiation leads to the development of benign and malignant thyroid neoplasms. There is considerable controversy, however, concerning whether radioactive iodine (131I) causes thyroid cancer. The aim of this investigation was to examine our experience and that in the literature related to this problem. From 1982 to March 1993 seven of 373 patients (1.9%) with thyroid cancer who were treated by one surgeon had a history of treatment with radioactive iodine for Graves' disease and toxic nodular goiter. Sixty-five patients have previously been reported in the literature from 1957 to present. Our patients (five women, two men) ranged in age from 26 to 80 years (mean 57 years). The interval between the exposure to the internal radiation and development of cancer ranged from 3 to 29 years (mean 11.4 years), and the mean age at the time of 131I treatment was 45 years (18-76 years). The therapeutic dose of 131I was 5 to 100 mCi (mean 25.3 mCi) in our patients. Two of our patients received 131I twice. The age of patients reported in the literature at the time of 131I treatment ranged from 7 to 74 years (mean 48 years). The mean therapeutic dose of 131I was 20.6 mCi (1.25-180.0 mCi) and the latent period was documented for a mean 8.7 years (0.25-28.0 years) in these patients. Three of 29 patients in the literature received 131I twice. Fine-needle aspiration cytology of thyroid nodules was positive for cancer in six of our patients (86%).(ABSTRACT TRUNCATED AT 250 WORDS)

Desensitization of adenylate cyclase in Chinese hamster ovary cells transfected with human thyroid-stimulating hormone receptor

Desensitization or decreased response to the same (homologous) or other stimuli (heterologous) is a well known process. Homologous desensitization to TSH has been demonstrated in normal thyroid tissue. Chinese hamster ovary cells (CHO) transfected with normal human TSH receptor (hTSHR) DNA, in contrast, have been reported not to desensitize. The purpose of our investigation was to determine whether CHO cells transfected with hTSHR desensitize in response to TSH and postreceptor stimulation. CHO cells were stably transfected with plasmid DNA containing hTSHR; nontransfected CHO cells served as the control. TSH (10 mU/ml), 5'-beta,gamma-imido-triphosphate [Gpp(NH)p; 0.1 mM], sodium fluoride (NaF; 10 mM), forskolin (10 microM), and (Bu)2cAMP (100 microM) were used to determine whether homologous or postreceptor heterologous desensitization of adenylate cyclase activity occurred in CHO-transfected cells. Intracellular cAMP accumulation was determined by RIA. Cells were incubated with TSH (to stimulate TSH receptor), Gpp(NH)p, NaF (to stimulate G-protein), forskolin (to stimulate adenylate cyclase activity), and (Bu)2cAMP (nonmetabolized cAMP analog). A second incubation was carried out with TSH (10 mU/ml). Maximal desensitization to either TSH or postreceptor stimulation was observed at 2 h. When transfected CHO cells were preexposed to TSH (10 mU/ml) for 4 h, even the smallest dose of TSH (0.001 mU/ml) caused desensitization. All substances that increased the intracellular cAMP concentration, such as TSH, Gpp(NH)p, NaF, forskolin, and (Bu)2cAMP, caused desensitization. The decrease in the cAMP response to TSH added in the second incubation was 63% less than the initial response to TSH or to postreceptor stimulation (P = 0.0001). In conclusion, desensitization of hTSHR-transfected CHO cells occurs in response to both receptor and postreceptor stimulation that increase cAMP levels. Because hTSHR transfected CHO cells desensitize, no specific thyroid factor(s) other than increased levels of cAMP is required.

Management of acute respiratory failure due to pulmonary edema with nasal positive pressure support

The management of patients with respiratory failure from cardiogenic pulmonary edema may require intubation and mechanical ventilation. This provides both ventilatory assistance as well as the beneficial hemodynamic effects of positive intrathoracic pressure. As the need for ventilation is usually short term, noninvasive ventilatory support may be adequate. We report the use of biphasic positive airway pressure by nasal mask (BiPAP system) to successfully manage two patients with respiratory failure due to pulmonary edema.

Acute reversible cardiomyopathy associated with the systemic inflammatory response syndrome

In the absence of ischemic heart disease, severe acute reversible myocardial dysfunction is uncommon, with sepsis most often being implicated in the ICU. We report a 38-year-old woman who developed profound transient myocardial depression due to nonseptic systemic inflammatory response syndrome caused by a necrotic kidney. Hemodynamic parameters and echocardiographic findings improved dramatically following nephrectomy. Other causes of acute myocardial suppression, including electrolyte abnormalities, drugs, catecholamine excess, and endocrine disease were excluded.

Community-acquired pneumonia in the elderly patient. Clinical features, epidemiology, and treatment

The relationship between age and the incidence of and mortality associated with pneumonia is complex. Age itself may not be an independent risk factor, because elderly patients also have a concomitant increase in the number of underlying risk factors for disease. The authors review the clinical features, epidemiology, and treatment of community-acquired pneumonia.

A placebo-controlled dose-finding study with bambuterol in elderly patients with asthma

A new long-acting bronchodilator prodrug, bambuterol hydrochloride, was tested in a randomized, crossover, and double-blind study in elderly asthmatic patients (aged 64 to 82 years). They received placebo and 5-mg, 10-mg, and 20-mg tablets once daily for a week at each dose. The plasma concentration of the active metabolite, terbutaline, increased linearly with the dose of drug (p < 0.001). Peak expiratory flow rate increased with dose in the morning (p < 0.001 for 10-mg and 20-mg doses) and afternoon (p < 0.05 for 10 mg; p < 0.001 for 20 mg) and was different from placebo for the 10-mg/d and 20-mg/d regimens. The use of supplemental inhaled beta 2-adrenergic agonist therapy was reduced during the night for the 10-mg (p < 0.05) and 20-mg (p < 0.01) doses in comparison to placebo. No significant effects of treatment on blood pressure and pulse were demonstrated. Tremor and palpitations were mild and related to the dose. These data suggest that treatment once daily with bambuterol hydrochloride in a dose of 10 or 20 mg improves pulmonary function and is well tolerated as bronchodilator therapy in elderly patients with asthma.

Infectious complications following isolated lung transplantation

STUDY OBJECTIVE

To ascertain the incidence, types, morbidity, and mortality of infectious episodes in isolated lung transplant recipients.

DESIGN

Retrospective chart review of patients who have undergone transplants over a six-year period in one institution.

PATIENTS

Twenty-three single and 17 double lung transplants followed up between 2 and 68 months.

RESULTS

Fifty-one episodes of infection occurred in the group with a slight predominance in the double lung transplants. The 32 episodes of bacterial infection constituted the largest group of infection and more than half of these were pneumonias. Organisms identified were predominantly Gram negative. While bacterial processes made up the bulk of infections, fatalities were rare. Viral and fungal infections were less common, but more often fatal. Of six cases of viral pneumonitis, two were fatal; two of five cases of invasive fungal infection were also fatal. Overall, six patients died of infection.

CONCLUSION

Our findings support previous reports from heart-lung centers documenting a high rate of infectious complications, particularly pneumonia, in recipients of lung grafts. In our experience, bacterial infections are the most common (two of three infections), but have the lowest mortality. Efforts should be directed toward establishing effective prophylaxis programs and early detection of infection.

The relationship of absorption characteristics and gastrointestinal side effects of oral antimicrobial agents

Normal bowel flora play an important role in preserving gastrointestinal (GI) function. They inhibit colonization by pathogenic bacteria, help in the metabolism of by-products of drugs and endogenous substances, aid in the synthesis of vitamins, and stimulate nonspecific host immune systems that protect against potential pathogens. Antimicrobial agents that are poorly absorbed from the GI tract can substantially alter the bowel flora. Narrow-spectrum antimicrobial agents are less likely to disrupt the bowel flora than broad-spectrum agents. Drugs that undergo extensive enterohepatic circulation can also disrupt normal flora. Knowledge of the extent of GI absorption, bile excretion, and spectrum of activity allows prediction of the likelihood of GI side effects. For example, clindamycin, which is relatively poorly absorbed and has significant bile secretion, is associated with a high incidence of diarrhea. The use of an antibiotic with a relatively narrow spectrum, excellent GI absorption, and minimal bile excretion should reduce the incidence of GI side effects.

The effect of rigid fixation on the survival of onlay bone grafts: an experimental study

Much attention has recently been focused on rigid fixation as a method of improving fracture healing. Whether such fixation, when applied to onlay grafting, improves graft take and volume is unknown. To examine this question, we compared survival of both endochondral and membranous grafts fixed rigidly and nonrigidly in areas of low motion (snout) and high motion (femur) in a rabbit model. Gross morphology, histologic analysis, and graft volume kinetics were evaluated. Findings demonstrate that in areas of high motion, the application of rigid fixation improves graft survival, whereas in a low-motion region, no differences in graft volume retention as a function of fixation were observed. Histologically, no differences with the method of fixation employed were seen, and similar revascularization patterns were noted. By kinetic analysis, rigid fixation appears to exert its most profound effect early in the postgraft period. Membranous bone grafts remain superior to endochondral grafts under all circumstances. From these studies, we conclude that rigid fixation is the method of choice in all circumstances where onlay bone grafts may be exposed to motion, shear, and torsional forces.

Preoperative assessment for lung transplantation

Lung transplantation has evolved from an intellectual curiosity to a viable therapeutic option in a selected number of patients with end-stage lung disease. The indications for single lung, double lung, or heart-lung transplantation at major North American transplant centers are presented, the selection criteria are discussed, and the standard preoperative evaluation is outlined. Utilizing these guidelines, a 1-year actuarial survival following each of these procedures of greater than 60% can be expected.

Long-term functional follow-up of lung transplant recipients

Transplantation is now a treatment option in patients with end-stage pulmonary and pulmonary vascular disease. This article describes the outcome of single and double lung transplants performed by the Toronto Lung Transplant Group. Specifically reported are mortality, cause of death, pulmonary physiology, arterial blood gases, and exercise performance. Where possible, these results are compared with results of heart-lung transplantation from other centers.

Results of single-lung transplantation for bilateral pulmonary fibrosis. The Toronto Lung Transplant Group

Between November 1983 and August 1989, we performed single-lung transplantation for end-stage pulmonary fibrosis in 20 patients. Nine patients (45 percent) who survived for more than one year form the basis of this report. Before surgery, the nine survivors had severe restrictive lung disease, with a mean (+/- SD) vital capacity (VC) of 43 +/- 9 percent, a forced expiratory volume in one second (FEV1) of 50 +/- 9 percent, and a single-breath diffusing capacity (DLCO) of 36 +/- 9 percent of predicted values. One year after transplantation, the patients' VC had reached 69 +/- 10 percent, FEV1 79 +/- 15 percent, and DLCO 62 +/- 16 percent of predicted values. Relative perfusion to the transplanted lung rose from 63 +/- 14 percent (three days after surgery) to 77 +/- 7 percent within three months and stayed constant or increased slightly thereafter. Before surgery, despite supplemental oxygen at flow rates varying from 1 to 9 liters per minute, none of the patients could exercise beyond stage 1/2 (2.7 km [1.7 miles] per hour, 5 percent grade) on a modified Bruce treadmill-exercise protocol. All eight patients tested one year or more after transplantation achieved at least stage 1 (2.7 km [1.7 miles] per hour, 10 percent grade), and usually a higher stage, without supplemental oxygen. Arterial oxygen tension returned to normal values in most patients (87 +/- 13 mm Hg), and supplemental oxygen, which all patients required before surgery, was no longer needed by any patient after transplantation. We conclude that in carefully selected patients with end-stage pulmonary fibrosis, single-lung transplantation is an effective treatment.

Out-patient management of patients with chronic obstructive lung disease

The treatment of chronic obstructive lung disease is multifaceted. If the patient smokes, he or she must quit. Treatment includes bronchodilator therapy, glucocorticosteroids, antibiotics for acute exacerbations, oxygen therapy for patients with chronic hypoxemia (it can also help patients with nocturnal and exercise-induced hypoxemia), and respiratory rehabilitation for motivated patients. Inhaled β-agonists and anticholinergic agents have additive effects in recommended doses, as do theophylline and β-agonists.

Airway hyperreactivity in patients undergoing lung and heart/lung transplantation

To assess airway reactivity in lung transplant patients, three heart/lung, three double lung, and eight single lung transplant patients underwent airway challenge tests. All patients were assessed by methacholine aerosol challenge and thirteen were also assessed by histamine aerosol challenge at least three months after transplant surgery. The airways of patients with bilaterally denervated lungs (heart/lung and double lung transplants) were significantly more reactive to both methacholine and histamine (p less than 0.01) than were the airways of patients with unilaterally denervated (single lung transplants) lungs. Inflammatory changes in the airway mucosal biopsies were minimal in three patients and absent in all others. These studies raise questions about the role of central innervation in the maintenance of normal airway function as well as the mechanisms of action of both methacholine and histamine in causing bronchoconstriction.

Pulmonary manifestations of tuberous sclerosis in first degree relatives

In a family with tuberous sclerosis affecting four generations a mother and daughter had the rare pulmonary manifestations of the disease. Pathologically the pulmonary disease may be the same as pulmonary lymphangioleiomyomatosis.

Clinical features of sarcoidosis in elderly patients

We reviewed 17 cases of biopsy-proven sarcoidosis occurring in patients who were 65 years of age or older at the time of diagnosis in order to determine the clinical features of sarcoidosis in this group of elderly patients. A female preponderance (76%) was noted, as well as significant respiratory and cutaneous symptoms. There were no characteristic diagnostic features of sarcoidosis in this group; therefore, we suggest that tissue biopsy is needed to exclude pulmonary diseases such as neoplasm or tuberculosis. Most elderly patients having sarcoidosis remained clinically stable during the period of follow-up and did not require therapy for sarcoidosis. We propose that sarcoidosis should be considered in the differential diagnosis of elderly patients presenting with pulmonary or multisystem disease.

Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea

We measured pharyngeal cross-sectional area and its change with alterations in lung volume in 10 subjects who snored and had obstructive sleep apnea, 6 subjects who snored and did not have obstructive sleep apnea, and 9 subjects who did not snore. Pharyngeal area was measured with use of an acoustic-reflection technique. We found that snorers with and without sleep apnea had a significantly smaller mean (+/- SE) pharyngeal cross-sectional area (4.1 +/- 0.2 and 3.7 +/- 0.9 cm2, respectively) at functional residual capacity than nonsnorers (5.4 +/- 0.5 cm2, P less than 0.025). When lung volume decreased from functional residual capacity to residual volume, both nonsnorers and snorers with sleep apnea had a decrease in pharyngeal area (from 5.4 +/- 0.5 to 4.5 +/- 0.4 cm2 and 4.1 +/- 0.2 to 3.4 +/- 0.2 cm2, respectively), whereas snorers without sleep apnea had no such decrease, suggesting that their pharynxes were less collapsible at low lung volumes. We conclude that snorers with and without sleep apnea have smaller pharyngeal cross-sectional areas than nonsnorers and that snorers with sleep apnea have a further decrease as lung volume falls.

Nalbuphine-induced pulmonary edema

We report the occurrence of acute pulmonary edema in a patient receiving therapy with nalbuphine, a synthetic narcotic analgesic. Other potential causes of acute pulmonary edema were excluded. It is likely that all opiate drugs share the propensity to produce acute pulmonary edema, and nalbuphine resembles other opiates in this regard.

Role of diffuse airway obstruction in the hypercapnia of obstructive sleep apnea

The mechanisms responsible for the development of chronic hypercapnia in patients with obstructive sleep apnea (OSA) are not well defined. Therefore, we tested the hypothesis that diffuse airway obstruction may be involved by studying 50 patients with a well-documented OSA syndrome. Seven patients had daytime hypercapnia with a mean PaCO2 of 51 +/- 2 (SEM) mm Hg, compared to a PaCO2 of 35 +/- 1 in the other 43 patients. There were no differences between the 2 groups in the number or duration of nocturnal obstructive events. In contrast, the hypercapnic patients were significantly heavier than the normocapnic patients (body weight, 189 +/- 11 versus 148 +/- 6% of ideal; p less than 0.005) and had evidence of diffuse airway obstruction, as indicated by an increased residual volume and a reduction in all expiratory flow rates. When the hypercapnic patients were compared with a weight-matched group of 9 normocapnic patients (body weight, 196 +/- 8% of ideal), there were still no differences in nocturnal obstructive events, but the differences in tests of airway mechanics persisted. Multiple regression analysis of PaCO2 against several anthropometric, respiratory physiologic, and polysomnographic variables revealed that only 2 variables (expiratory reserve volume and FEV1/FVC), both of which are influenced by airway mechanics, were significantly correlated with PaCO2 (multiple r = 0.78; p = 0.0001). The findings suggest that OSA alone does not produce daytime hypercapnia even in obese patients, and that the presence of diffuse airway obstruction is an important predisposing factor to the development of chronic CO2 retention in such patients.