Indices to quantify changes in intracranial and cerebral perfusion pressure by assessing agreement between hourly and semi-continuous recordings.

OBJECTIVES: Little published data exists on whether nurse-recorded end-hour values of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are representative of continuous monitoring during the hour. There is also no standard method of quantifying the observed perturbations in cerebral hemodynamics. This study compared the level of agreement between end-hour values and computer downloaded observations of ICP and CPP at 15-min intervals. We also developed the intracranial hypertension index and the cerebral hypoperfusion index to quantify perturbations in cerebral hemodynamics. Each of these indices relates the number of abnormal observations to the total number of observations taken. METHODS: Prospective, non-interventional study. RESULTS: The bias and precision between the two methods for ICP and CPP were -0.002+/-2.6 mmHg and -1.1+/-6.2 mmHg, respectively. A strong correlation existed between the hourly mean calculated from the 15-min and the end-hour values for both ICP ( r(2)=0.95, p<0.0001) and CPP ( r(2)=0.78, p<0.001). The intracranial hypertension index was 40% from the 15-min measurements and 41% from the hourly observations ( p= NS). The cerebral hypoperfusion indices were 13.4% and 13.1% with the 15-min and end-hour values, respectively ( p= NS). CONCLUSIONS: The end-hour values of ICP and CPP are as accurate as more frequent measurements during the hour and are adequate for purposes of epidemiological research and medico-legal audit. The intracranial hypertension and cerebral hypoperfusion indices may be useful in describing cerebral hemodynamics for future interventional studies and for assessing quality in the delivery of neuro-critical care.

Can we achieve consensus on central venous catheter-related infections?

Central venous catheter-related bacteraemia is a substantial and preventable source of iatrogenic morbidity and mortality. A single episode of catheter-related bacteraemia has an estimated cost of A$50,000, with an attributable mortality between 10 and 35%. Catheter colonization is diagnosed with standard culture techniques. Diagnostic criteria for catheter-related bacteraemia include the results of cultures from the catheter tip, the peripheral blood and other possible sites of infection. The presence of clinical symptoms and subsequent defervescence may assist in making the diagnosis. This review explores the existing definitions of catheter-related infections and proposes a new and more rigorous classification with criteria for definite, probable and possible catheter-related bacteraemia. The authors hope that this classification will enhance the interpretation of the literature and the planning of new investigations. Infection rates can be reduced by appropriate site selection, adequate skin preparation, sterile technique and appropriate dressings. Decreased manipulation of administration sets, with more careful technique and less frequent set replacement, may reduce hub contamination. Infection rates increase with the duration in situ of the catheter, however are not reduced by regular scheduled catheter replacement or guide-wire exchanges. A range of antimicrobial catheter materials and coatings are under investigation, some of which are effective in reducing the rate of catheter-related bacteraemia. Chorhexidine-silver sulphadiazine and rifampicin-minocycline are the best studied combinations to date. Further developments are expected, although none are likely to be as effective as not inserting or removing the central venous catheter when it is not required.

Rhinoviruses infect the lower airways.

Rhinoviruses are the major cause of the common cold and a trigger of acute asthma exacerbations. Whether these exacerbations result from direct infection of the lower airway or from indirect mechanisms consequent on infection of the upper airway alone is currently unknown. Lower respiratory infection was investigated in vitro by exposing primary human bronchial epithelial cells to rhinoviruses and in vivo after experimental upper respiratory infection of human volunteers. Bronchial infection was confirmed by both approaches. Furthermore, rhinoviruses induced production of interleukin-6, -8, and -16 and RANTES and were cytotoxic to cultured respiratory epithelium. This evidence strongly supports a direct lower respiratory epithelial reaction as the initial event in the induction of rhinovirus-mediated asthma exacerbations. The frequency of infection and the nature of the inflammatory response observed are similar to those of the upper respiratory tract, suggesting that rhinovirus infections may be one of the most important causes of lower in addition to upper respiratory disease.

Peak expiratory flow changes during experimental rhinovirus infection.

Rhinovirus (RV) colds are associated with asthma exacerbations and experimental infections are commonly used to investigate the mechanisms involved. However, a temporal association between experimental RV infections and falls in peak expiratory flow (PEF) have not been demonstrated. PEF was measured in 22 volunteers (11 normal, five atopic, six atopic asthmatic) who developed RV serotype 16 colds after inoculation. PEF was measured twice daily for 2 weeks prior and 6 weeks after RV infection and episodes of respiratory morbidity based on changes in PEF were defined using validated criteria. Six significant reductions in PEF were temporally related to the RV infections (in two (18%) normal, one (20%) atopic, three (50%) atopic asthmatic subjects, p=0.1) and occurred 4-9 days (median 6) after inoculation. Mean+/-SEM PEF at day 6 was 87.8+/-1.8% of the predicted value in the six subjects with reductions versus 99.4+/-1.4% pred in those without (p=0.01). Symptom scores were significantly different at day 6 in the two groups (10.6+/-1.9 versus 6.8+/-1.0, p=0.03), but no differences were noted in the viral culture scores and changes in nasal albumin. In subjects with significant PEF reduction, the decrease in the provocative concentration causing a 20% fall in the forced expiratory volume in one second (FEV1) (PC20) was 1.7+/-1.3 mg x mL(-1) versus 1.2+/-1.1 mg x mL(-1) in the negative group (p=0.06). The degree of seroconversion to RV was significantly higher in the group with reduced PEF (median change dilutions 8 versus 4, p=0.02). The results of the present study suggest that rhinovirus-associated, respiratory morbidity occurs during experimental infection in some but not all normal and asthmatic subjects and also that experimental colds are a valid model for the study of rhinovirus-associated airway symptoms and asthma exacerbations.

Clinical information systems in intensive care.

OBJECTIVE: To review the requirements and functions of clinical information systems for the critical care environment. DATA SOURCES: Peer reviewed studies and articles reported from 1990-1998, identified through MEDLINE search and subsequent article references. SUMMARY OF REVIEW: Clinical information systems (CIS) utilise information technologies to improve and add value to information management, and critical care areas have provided clinical leadership in their development and implementation. Expectations for these systems are high, yet certain basic requirements must be fulfilled. Bedside charting functions of CIS are highly developed and successful. Clinical record keeping has been more challenging, particularly the requirement for electronic storage of a medico-legal record. Decision support ranges in its extent and requires further development. Successful integration with other hospital systems is highly desirable but may be made more difficult by the lack of rigorous technical standards in healthcare computing. The CIS clinical database is fundamental to the quality improvement, research and business reporting functions. The huge amount of data, the lack of common minimal and extensive data sets, and the technical challenges of software development, all combine to make this a resource expensive venture requiring on site customisation. Purchasing and implementing a CIS is costly in human and material resources. CONCLUSION: A high performance CIS is not yet available as an 'off the shelf' product. Close collaboration between the industry and clinicians is important for successful implementation. Clinical awareness of these issues will encourage product development and suitable purchasing strategies.

Lower airways inflammatory response during rhinovirus colds.

Human rhinovirus (HRV) causes the majority of common colds and possibly also asthma exacerbations. Mechanisms linking viruses to changes in airway reactivity are not defined and we hypothesized that changes in endobronchial cell populations may be implicated. Bronchial mucosal biopsies taken before, during and after experimental infections with HRV serotype 16 were examined and histamine reactivity was measured in 17 adult volunteers (6 atopic asthmatics). Biopsies were examined for mast cells, eosinophils, lymphocytes and neutrophils by immunohistochemical techniques. Increases in histamine responsiveness (PC20) were found (p = 0.048), accompanied by an increase in submucosal lymphocytes (p = 0.05). There was a significant increase in epithelial eosinophils with the cold (p = 0.042), and in asthmatics this appeared to persist into convalescence. Rhinoviral common colds are associated with a bronchial mucosal lymphocytic and eosinophilic infiltrate that may be related to changes in airway responsiveness and asthma exacerbations.

Lower airways inflammation during rhinovirus colds in normal and in asthmatic subjects.

Human rhinoviruses (HRV) cause the majority of common colds and are etiologically linked with changes in lower airways physiology and asthma exacerbations. We hypothesized that changes in bronchial mucosal inflammatory cell populations may be responsible for HRV-induced changes in airway reactivity. We examined bronchial mucosal biopsies during experimental infections with HRV serotype 16 and measured changes in histamine reactivity. Seventeen adult volunteers (six atopic asthmatics) had baseline measurements of histamine reactivity and fiberoptic bronchoscopic biopsies, followed 2 wk later by viral inoculation. Further bronchial biopsies were taken on Day 4 of the infection and 6 to 10 wk later. Mast cells, eosinophils, lymphocytes, and neutrophils were quantified by immunohistochemical techniques. Infection was documented by viral culture, seroconversion, and symptoms. An increase in histamine responsiveness during the cold (p = 0.048) was accompanied by increases in submucosal lymphocytes (p = 0.050). There was a subsequent decrease in submucosal and epithelial lymphocytes in convalescence (p = 0.028; p = 0.030). There was an increase in epithelial eosinophils with the cold (p = 0.042), and in asthmatics this appeared to persist into convalescence. A peripheral blood lymphopenia correlated with increased responsiveness (r = 0.062, p = 0.014). Rhinoviral colds are associated with a bronchial mucosal lymphocytic and eosinophilic infiltrate that may be related to changes in airway responsiveness and asthma exacerbations.

Immunohistochemical analysis of nasal biopsies during rhinovirus experimental colds.

Human rhinoviruses (HRV) are an important cause of upper respiratory tract infection and are etiologically linked with asthma exacerbations. However, the mechanisms of virus-induced inflammation are largely unknown. We examined nasal mucosal biopsies for the presence of an associated inflammatory cellular infiltrate during experimental rhinovirus infection. A group of 21 adult volunteers (10 atopic) had baseline nasal biopsies, followed 2 wk later by inoculation with HRV Serotype 16. Nasal biopsies were taken on Day 4 of the cold and again 6-10 wk later. Infection was documented by symptom scores, viral culture, and seroconversion. The biopsies were fixed in acetone and processed into glycol methacrylate resin for semithin sectioning. Mast cells, eosinophils, lymphocytes, and neutrophils were identified with appropriate monoclonal antibodies and a streptavidin-biotin horseradish peroxidase technique. There were no significant changes in the numbers of inflammatory cells present during the cold or the convalescent period compared with baseline biopsies (Wilcoxon paired, p > 0.05). There were also no differences between normal and atopic groups. We suggest that rhinoviral colds are not associated with increased inflammatory cellularity and that other mechanisms, such as increased mediator release, are responsible for coryzal symptoms.

Amplified rhinovirus colds in atopic subjects.

Evidence suggests that atopic individuals may be predisposed to more severe rhinoviral colds coupled to a worsening of existing airway disease than those with asthma. The role of atopy and IgE levels, as well as their relationship to clinical disease expression have not been defined. We hypothesized that an allergic diathesis modulates rhinoviral colds and have initiated studies of normal, atopic and asthmatic subjects employing experimental rhinoviral infection, with measurements of symptom scores, viral shedding and cultures, albumin in nasal washes and serological responses. Twenty-two subjects (11 normal, 5 atopic, 6 atopic and asthmatic) participated and were inoculated with human rhinovirus serotype 16 (HRV 16). Measurements of neutralizing antibody and viral culture were performed at screening, pre-inoculation, during the cold and at 8-10 weeks convalescence. Daily symptoms were noted, nasal washes done, IgE measured and atopy was diagnosed by skin tests. Seventeen volunteers developed clinical colds as assessed by symptom scores, virus shedding was demonstrated (with positive culture) in all subjects and a fourfold or higher seroconversion occurred in 11/22. Neutralizing HRV antibody developed unexpectedly in 10 subjects between screening and inoculation and the presence of absence of this pre-inoculation antibody determined subsequent severity of colds in normal but not in atopic subjects. Atopic antibody positive individuals developed severe clinical colds that were independent of preinoculation antibody in contrast to normal subjects who developed mild colds in the presence of a neutralizing antibody (P = 0.01). Both atopic and normal antibody negative subjects developed severe colds.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of rhinovirus infection of the nasal mucosa by oligonucleotide in situ hybridization.

Human rhinoviruses (HRVs) cause the common cold and often induce lower airway symptoms such as cough and wheezing. Although HRV infection is presumed to involve primarily ciliated epithelial cells, this has not been confirmed in vivo, and the cellular distribution and spread of infection as well as the pathogenesis of cold related nasal and chest symptoms remain speculative. We have developed in situ hybridization (ISH) to explore localization of the virus to airway tissues, employing HRV 16-derived oligonucleotide probes after sequencing part of the genome of this serotype. A reverse transcription-polymerase chain reaction was used to generate DNA from HRV 16 for sequencing; this yielded 305 nucleotide bases that showed considerable homology to other HRVs. The HRV 16 sequence was used to design oligonucleotides functioning as antisense and sense probes. These probes as well as random sequence and pathogen control oligonucleotides were applied to HRV-infected cell-clot complexes and finally to sections from six paired nasal biopsies obtained before, during, or after HRV-proven colds. Specificity of hybrids was established by the absence of signal in uninfected tissue, in cells infected with other viruses, after RNase pretreatment, and with application of control probes. Hybridization signals were observed in epithelial cells in three of six biopsies obtained during a cold, using probes to viral (+) strand; intermediate (-) strand, implying viral replication, was present in one biopsy. Evidence for infection of nonepithelial cells was inconclusive. HRVs cause productive infection of nasal epithelium during a cold and their intracellular localization may produce perturbation of inflammatory mediators and cytokine profiles.(ABSTRACT TRUNCATED AT 250 WORDS)

Methotrexate in asthma. A safety perspective.

The inflammatory process underlying bronchial asthma is well established and has prompted clinical interest in nonsteroidal anti-inflammatory forms of treatment. Although unproven, it has been suggested that effective treatment of allergic inflammation may prevent long term consequences of asthma and avert deterioration in pulmonary function. Methotrexate has potent anti-inflammatory actions, even at low doses, and was judged to be a suitable candidate drug for asthma treatment if it could demonstrate an acceptable tolerability profile. Low dose methotrexate has been investigated in both noncomparative studies and in placebo-controlled studies of severe asthma. In general, such studies have suggested that methotrexate may have steroid-sparing benefits coupled to generally mild adverse events; although adverse effects were not of a serious nature they were observed in up to one-third of patients. Rare but potentially life-threatening adverse effects involving the pulmonary, hepatic and haematological systems remain of particular concern. Methotrexate should therefore be considered as an adjunct to high dose inhaled corticosteroids in patients who require more than 10mg of prednisolone daily, and who experience severe and unacceptable steroid-related adverse effects. Treatment should only be initiated by physicians with experience in the use of the drug, and the relevant safety parameters should be closely monitored.