Regional difference in airway epithelial response to neutrophil elastase: tracheal secretory cells discharge and recover in hamsters that develop bronchial secretory-cell metaplasia

Human neutrophil elastase (HNE) causes secretory granule discharge and conversion of many Clara cells to mucous cells in hamster bronchi. We investigated whether the trachea responds to HNE in a similar manner because of its abundance of Clara cells. By light microscopy, the tracheal epithelium of animals exposed to a single intratracheal injection of HNE was normal at 21 days, although bronchial secretory-cell metaplasia (SCM) was present. An ultrastructural differential cell count showed no increase in the proportion of granulated secretory cells in HNE-treated animals at 8 and 21 days postinjection compared to saline or untreated controls. At 2 h, the percentage of granulated secretory cells was lower and that of granulated secretory cells was higher in HNE-treated animals than in controls. The HNE-treated animals had fewer secretory granules per cell profile and more surface undulation than controls. By 1 day, the differential cell count and number of granules per cell profile were normal. Saline did not affect the differential cell count or granule number at any time. Ultrastructural study of untreated trachea disclosed the same three types of Clara cell that are found in the bronchus, but their frequencies, with one exception, are significantly different in the two regions. We conclude that HNE acts as a secretagogue in both trachea and bronchus but that an amount of enzyme sufficient to cause bronchial SCM does not induce a similar lesion in trachea. Heterogeneity of Clara cell types in hamster airways may explain the regional variation in secretory-cell modulation by HNE.     

The prevalence of alcohol-induced liver disease and hepatitis C and their interaction in a tertiary care setting.

BACKGROUND & AIMS: We examined the prevalence and clinical characteristics of alcohol-induced liver disease (ALD) in patients referred to a tertiary care center and examined the interaction between ALD and hepatitis C virus (HCV) in a longitudinal survival model. METHODS: A total of 1611 patients with chronic liver disease referred to a tertiary care center between 1994 and 2001 were analyzed. The survival of ALD, HCV, and the combination of the 2 (ALD + HCV) was compared in cirrhotic and precirrhotic patients by using Kaplan-Meier estimates. A Cox proportional hazards model was used to examine the independent effects of predictors on survival. RESULTS: ALD comprised 31% of the cohort, ALD + HCV comprised 14%, HCV comprised 22%, and the rest comprised 33%. The survival of precirrhotic patients with HCV was significantly better than the survival of those with ALD (hazard ratio, 0.27; P = 0.0006) over long-term and 1-year (hazard ratio, 0.24; P = 0.016) follow-up periods. There was no difference in survival between patients with ALD and ALD + HCV ( P = 0.62). In patients with cirrhosis, survival did not differ by cause; decompensated liver disease (hazard ratio, 1.67; P = 0.004) and continued alcohol abuse (hazard ratio, 2.19; P = 0.002) predicted worse survival in this group. CONCLUSIONS: ALD with HCV remains a prevalent cause of chronic liver disease in patients referred to a U.S. tertiary care center. In patients with ALD, the addition of HCV does not change survival, suggesting alcoholism is the driving force for mortality in patients coming to clinical attention. In patients with cirrhosis, ongoing excessive alcohol use and complications of end-stage liver disease drive mortality, irrespective of the underlying cause of chronic liver disease.     

Ultra-protective tidal volume: how low should we go?

Applying tidal volumes of less than 6 mL/kg might improve lung protection in patients with acute respiratory distress syndrome. In a recent article, Retamal and colleagues showed that such a reduction is feasible with conventional mechanical ventilation and leads to less tidal recruitment and overdistension without causing carbon dioxide retention or auto-positive end-expiratory pressure. However, whether the compensatory increase in the respiratory rate blunts the lung protection remains unestablished.Further reducing tidal volumes beyond the standard 6 mL/kg is an appealing goal in patients with acute respiratory distress syndrome (ARDS) [1]. Such reduction could decrease the tidal stretch imposed on the lung, potentially attenuating further the ventilator-induced lung injury [2]. In fact, tidal volumes of less than 6.5 mL/kg and as low as 4 mL/kg were recently associated with increased survival in patients with ARDS [3]. One of the main obstacles to such a strategy is the potential for carbon dioxide (CO₂) retention and severe acidosis. To avoid this, specialized techniques, such as high-frequency oscillatory ventilation and extracorporeal CO₂ removal, have been previously tested with mixed results [4-6].In the previous issue of Critical Care, Retamal and colleagues proposed that lower tidal volumes could be used with conventional positive-pressure ventilation without leading to CO₂ retention [1]. A reduction in tidal volume from 6 to 4 mL/kg was feasible with a decrease in the instrumental dead space and an increase in the respiratory rate. In patients with ARDS, the dead space is a marker of disease severity [7]. Consequently, very low tidal volumes can be difficult to use in practice, especially in very sick patients, because the necessary increase in respiratory rate might cause significant auto-positive end-expiratory pressure (auto-PEEP). Luckily, patients with severe ARDS also tend to have low lung compliance [8], making their lungs inflate and deflate fast. Therefore, this restrictive ventilatory pattern allows the safe use of high respiratory rates without leading to significant auto-PEEP.Retamal and colleagues [1] should be congratulated for their careful design of the ventilator protocol in the 4 mL/kg phase, which allowed an effective CO₂ elimination. The bottom line is that if one decides to use very low tidal volumes with high respiratory rates, attention to the details is invaluable. First, the removal of any dispensable dead space, including substituting an external heated humidifier by the heat-moisture exchanger, is imperative. Second, the use of volume-controlled ventilation helps to keep short inspiratory times. Peak airway pressures may increase, but the preserved expiratory time guarantees low auto-PEEP and, consequently, low plateau pressures. For safety, plateau pressures and auto-PEEP should be measured periodically. Third, in selected cases with high recruitability, the alveolar dead space can be minimized through recruitment maneuvers and higher PEEP values. Finally, the use of a short end-inspiratory pause is encouraged to improve the CO₂ elimination [9]. These measures will improve the safety and optimize the CO₂ elimination of a strategy with very low tidal volumes, even with higher-than-normal respiratory rates.However, even successfully avoiding CO₂ retention, this strategy has yet to be proven effective in terms of further lung protection. We believe that two aspects should be taken into consideration. The first is whether the strategy attenuated the mechanisms of lung injury. The authors performed computed tomography scans in all patients at tidal volumes of both 4 and 6 mL/kg and showed that the amount of cyclic recruitment-derecruitment and hyperinflation decreased after reducing the tidal volume. Although the absolute reduction was small (less than 1% of the lung weight), this finding is suggestive of decreased injury per breath. The second aspect is that an increased respiratory rate can be injurious per se [10]. It would be important to know whether the compensatory increase of the respiratory rate blunted the protective effect per breath of the tidal volume reduction.This tradeoff was emphasized recently in a model of the energy delivered by the ventilator as a surrogate for the potential lung damage [11]. Decreases in tidal volume require disproportionate increases in respiratory rate to maintain alveolar ventilation, and so more energy can be delivered to the lungs even at reduced stress and strain per breath. Though purely theoretical, this hypothesis helps reconcile our expectation of a further protective effect of very low tidal volumes with the recent findings of harmful or null effect of oscillatory high-frequency ventilation [5,6]. In these trials, it is possible that the reduction in lung injury per breath was offset by the very high respiratory rates applied.Finally, Retamal and colleagues [1] followed their patients for 5 to 30 minutes only. Since lower tidal volumes tend to promote atelectasis, especially under insufficient PEEP [12], a longer observation time perhaps would have shown an increase in atelectasis and driving pressures, opposing the benefits initially achieved.In conclusion, we are convinced that a strategy with very low tidal volumes (4 mL/kg) is feasible with conventional positive-pressure ventilation. This strategy could be used in patients with high plateau pressures or high driving pressures with standard 6 mL/kg tidal volumes, but we need more data in terms of lung protection before we can recommend this strategy to every patient with ARDS.     

Lymph node staging by means of positron emission tomography is less accurate in non-small cell lung cancer patients with enlarged lymph nodes: analysis of 1,145 lymph nodes

BACKGROUND: Despite documented superiority of integrated positron emission tomography-computerized tomography (PET-CT) over computerized tomography (CT) in lymph node staging in non-small cell lung cancer, little is known about the sensitivity, specificity and accuracy of integrated PET-CT among enlarged lymph nodes. We sought to assess if PET-CT is uniformly accurate among enlarged and non-enlarged lymph nodes. METHODS: A retrospective review of 206 consecutive patients with histologically proven non-small cell lung cancer who underwent resection and/or mediastinoscopy in our centre over 30 months period was carried out. All these patients had pre-operative staging with integrated PET-CT as an adjunct to chest CT prior to resection and/or mediastinoscopy. Diabetic patients (BM>or=8.0 mmol/l) and those who received neo-adjuvant chemotherapy were excluded. The pathological results of all these cases were reviewed and correlated with those on CT and integrated PET-CT. RESULTS: The sensitivity, specificity, accuracy, positive and negative predictive values were higher in integrated PET-CT than CT alone in all lymph nodes, whether N1 or N2. When lymph nodes were stratified by size, the sensitivity of PET-CT was significantly higher among enlarged (>1cm) than non-enlarged (1cm) should be with caution as the specificity of PET-CT is lower and its ability to detect truly negative nodes become reduced. NSCLC patients with enlarged nodes by CT criteria who are PET-CT negative may require cervical mediastinoscopy to rule out metastatic spread to these nodes. Prospective studies are warranted.     

Blood usage in lung transplantation

BACKGROUND: Few published data are available regarding perioperative blood usage in lung transplantation. STUDY DESIGN AND METHODS: The medical records of all patients undergoing lung transplantation at a university medical center in 1994 and 1995 were reviewed. RESULTS: Ninety patients underwent lung transplantation during this period. Six patients were excluded: two received a living related-donor lung, three underwent retransplantation and one underwent concomitant repair of a tetralogy of Fallot. Of the 84 evaluable patients, 59 underwent single lung transplantation and 25 double lung transplantation. Double-lung recipients used more red cells (6.4 vs. 1.7 units, p = 0.0002) and were more likely to receive red cells, platelets, plasma, or any component (92 vs. 32%, p< or =0.0001) than were single-lung recipients. Double- lung recipients were more likely to require cardiopulmonary bypass (40 vs. 12%, p = 0.003), and cardiopulmonary bypass was associated with greater transfusion requirements (p< or =0.0001). However, among patients requiring cardiopulmonary bypass, blood use did not differ between those undergoing double lung transplantation and those undergoing single lung transplantation. In the subset of patients not requiring cardiopulmonary bypass, double-lung recipients received more red cells (4.5 vs. 0.7 units, p< or =0.0001) and more plasma (2.0 vs. 0.2 units, p = 0.006). CONCLUSION: Double-lung recipients require more perioperative transfusions than single-lung recipients. The greater transfusion requirement is due to the more frequent need for cardiopulmonary bypass as well as the greater complexity of the procedure. These data are useful for developing surgical blood ordering guidelines for lung transplantation.     

Outpatient antimicrobial susceptibility: comparison with inpatient susceptibility patterns

Because specific outpatient epidemiologic data on the susceptibility of organisms are not readily available to guide empiric antibiotic therapy in the ambulatory setting, we reviewed all positive culture reports of clinical specimens (n = 935) isolated exclusively from outpatients of the Eastern Carolina Family Practice Center over a 1-year period. Eighty percent were from urine cultures, 12 percent from wound cultures, and 5 percent from sputum cultures. An antibiogram was developed that showed a pattern of bacterial resistance similar to that reported elsewhere. More than 80 percent of urinary tract infections were caused by Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. More than 50 percent of skin and soft tissue infections were caused by Staphylococcus aureus and other Staphylococcus species. Susceptibilities of these organisms were compared with those reported by the local hospital, and antimicrobial resistance patterns were similar, which suggests that the choice of empiric antibiotic therapy can follow susceptibility patterns derived from either inpatient or outpatient laboratories in areas with similar resistance patterns. Further research into the epidemiology and susceptibility of organisms isolated from outpatients is needed. Whether the susceptibility of inpatient and outpatient antimicrobial resistance found in this investigation can be extrapolated to other geographic areas remains to be determined.     

Spontaneous coronary artery dissection: a report of three cases and review of the literature.

We describe the clinical course of three patients who developed spontaneous coronary artery dissection. All patients were young women, one 9 weeks pregnant. All presented with chest pain; one died suddenly proving refractory to resuscitation, another developed unstable angina culminating in myocardial infarction, cardiogenic shock and death, and the third patient underwent coronary artery bypass grafting following diagnosis of a spontaneous coronary dissection of the left anterior descending artery at angiography. Pathological findings in the two fatal cases are reported. This condition, although rare, is a prominent cause of ischaemic coronary events in young women, when it is frequently associated with pregnancy or the puerperium. Most patients die suddenly, but a clinical spectrum is seen including stable and unstable angina, myocardial infarction and cardiogenic shock. The left anterior descending artery is most frequently affected. The classical histological finding is that of a large haematoma occupying the outer third of the media resulting in complete compression of the true lumen. The cause of spontaneous dissection remains unclear but theories of aetiology include a medial eosinophilic angiitis, pregnancy-induced degeneration of collagen in conjunction with the stresses of parturition, and rupture of the vasal vasorum. The diagnosis must be considered when a patient presents with a suggestive clinical profile. Urgent angiography should be undertaken to establish the diagnosis and consideration given to the need for coronary artery bypass grafting, which has been successfully employed in a number of patients. The uneventful long-term survival of cases treated conservatively has been reported.     

Neonatal treatment with 192 IgG-saporin produces long-term forebrain cholinergic deficits and reduces dendritic branching and spine density of neocortical pyramidal neurons

The role of basal forebrain-derived cholinergic afferents in the development of neocortex was studied in postnatal rats. Newborn rat pups received intraventricular injections of 192 IgG-saporin. Following survival periods ranging from 2 days to 6 months, the brains were processed to document the cholinergic lesion and to examine morphological consequences. Immunocytochemistry for choline acetyltransferase (ChAT) and in situ hybridization for ChAT mRNA demonstrate a loss of approximately 75% of the cholinergic neurons in the medial septum and nucleus of the diagonal band of Broca in the basal forebrain. In situ hybridization for glutamic acid decarboxylase mRNA reveals no loss of basal forebrain GABAergic neurons. Acetylcholinesterase histochemistry demonstrates a marked reduction of the cholinergic axons in neocortex. Cholinergic axons are reduced throughout the cortical layers; this reduction is more marked in medial than in lateral cortical areas. The thickness of neocortex is reduced by approximately 10%. Retrograde labeling of layer V cortico-collicular pyramidal cells reveals a reduction in cell body size and also a reduction in numbers of branches of apical dendrites. Spine densities on apical dendrites are reduced by approximately 20-25% in 192 IgG- saporin-treated cases; no change was detected in number of spines on basal dendrites. These results indicate a developmental or maintenance role for cholinergic afferents to cerebral cortical neurons.      

A gene transfer strategy for making bone marrow cells resistant to trimetrexate

Trimetrexate (TMTX) is an anticancer drug with potential advantages over the more commonly used antifolate, methotrexate (MTX); however, its use has been limited by severe myelosuppression. Retroviral vectors containing mutant dihydrofolate reductase (DHFR) genes have been used to protect bone marrow cells from MTX, suggesting a similar approach could be used for TMTX. We first screened six variants of human DHFR to determine which allowed maximal TMTX resistance in fibroblasts. A variant enzyme containing a Leu-to-Tyr mutation in the 22nd codon (L22Y) was best, allowing a 100-fold increase in resistance over controls. Murine hematopoietic progenitor cells transduced with an L22Y- containing retroviral vector also showed high-level TMTX resistance in vitro. Mice reconstituted with L22Y-transduced bone marrow cells were challenged with a 5-day course of TMTX to determine whether hematopoiesis could be protected in vivo. Transfer of the L22Y vector resulted in consistent protection from TMTX-induced neutropenia and reticulocytopenia at levels that correlated with the proviral copy number in circulating leukocytes. We conclude that the L22Y vector is highly effective in protecting hematopoiesis from TMTX toxicity and may provide a means for increasing the therapeutic utility of TMTX in certain cancers.