Models of critical care delivery: physician staffing in the ICU.

Although a consensus has emerged over the value of intensive care units (ICUs) in improving both the outcome and efficiency of critical care, the optimal staffing configuration of physicians who provide this care remains controversial. The value of open ICUs, where many clinicians can admit and care for patients, versus closed ICUs, where an on-site intensivist or housestaff team (or both) provides primary care of the critically ill patient is one aspect of this controversy. The roles of the intensivist, the ICU housestaff team, and the ICU director have also been debated. This article reviews the available literature on physician staffing in critical care units and its relationship to outcome and cost-effectiveness of care.

Pneumocystis carinii glycoprotein A inhibits surfactant phospholipid secretion by rat alveolar type II cells.

Pneumocystis carinii pneumonia (PCP) remains a major cause of morbidity in AIDS. The pathogenesis of PCP is poorly understood, but evidence of surfactant abnormalities is mounting. The role of the major surface glycoprotein of P. carinii, gpA, in producing surfactant abnormalities was investigated. Rat type II pneumocytes were incubated with [3H]choline, purified gpA, and modulators. Lipid was extracted, and [3H]dipalmitoyl phosphatidylcholine (DPPC) secretion was calculated. Contaminating endotoxin had no effect on DPPC secretion. gpA inhibited basal and ATP-stimulated DPPC secretion in a dose- and time-dependent manner. An anti-gpA monoclonal antibody attenuated inhibition of DPPC secretion. Unglycosylated recombinant gpA inhibited secretion, suggesting that functional activity resides in the protein moiety of gpA. These results suggest that gpA is a specific trigger for abnormalities of surfactant lipids in PCP. This is a unique role for a microbial product in disease pathogenesis and a potentially exploitable therapeutic target.

Interleukin-8 and eicosanoid production in the lung during moderate to severe Pneumocystis carinii pneumonia in AIDS: a role of interleukin-8 in the pathogenesis of P. carinii pneumonia.

Pneumocystis carinii pneumonia (PCP) may cause severe respiratory distress. This is believed to be partly caused by the accumulation of neutrophils in the lung. Interleukin-8 (IL-8) and leukotriene B4 (LTB4) are potent neutrophil chemo-attractants and activators. Eicosanoids [i.e. prostaglandins (PG) and leukotrienes (LT)] are pro-inflammatory mediators released from arachidonic acid by action of phospholipase A2 (PLA2) and have been implicated in the host response to micro-organisms. Bronchoalveolar lavage (BAL) was performed on patients with PCP as part of a randomized study of adjuvant corticosteroids vs. placebo, in addition to standard antimicrobial therapy. Re-bronchoscopy was offered at day 10. BAL fluid was available for 26 patients who had follow-up bronchoscopy performed. At diagnosis, IL-8 levels were elevated in patients with PCP, compared to healthy controls, and correlated with relative BAL neutrophilia and P(A-a)O2. LTB4 was also elevated in PCP, but failed to correlate with either BAL neutrophilia or P(A-a)O2. PLA2 activity in patients correlated with IL-8 levels and BAL neutrophilia, but not with P(A-a)O2. A trend towards a decrease in IL-8 levels in BAL fluid was detected in the corticosteroid-treated patients from days 0-10, whereas no change was detected in the placebo group. No change in levels of LTB4, LTC4, PGE2, PGF2a and PLA2 were detected cover time in either treatment group. This study establishes a correlation between IL-8, BAL neutrophilia and P(A-a)O2, and suggests a role of IL-8 as a mediator in the pathogenesis of PCP, whereas the role of eicosanoids seems less clear.

Leukotriene B4 and interleukin-8 in human immunodeficiency virus-related pulmonary disease.

STUDY OBJECTIVE: To investigate the pathogenesis of lung injury in Pneumocystic carinii pneumonia and nonspecific interstitial pneumonitis (NIP), common pulmonary complications of human immunodeficiency virus (HIV) infection. The efficacy of corticosteroid therapy in P carinii pneumonia and the observation that bronchoalveolar lavage (BAL) neutrophilia predicts a poor prognosis support the premise that the lung injury of P carinii pneumonia is due to the host's inflammatory response to the infection. DESIGN: In vitro measurements on previously collected BAL fluid samples. SETTING: The Clinical Center of the National Institutes of Health, a research hospital and tertiary care referral center. PATIENTS: Five normal volunteers, 5 asymptomatic HIV-positive patients, 10 HIV-positive patients with NIP (5 asymptomatic and 5 with respiratory symptoms), and 19 HIV-positive patients with P carinii pneumonia. MEASUREMENTS AND RESULTS: BAL leukotriene B4 (LTB4), interleukin 8 (IL-8), and phospholipase A2 (PLA2) were measured. IL-8 and PLA2 were elevated in patients with P carinii pneumonia, and IL-8 correlated with BAL fluid absolute neutrophil count. LTB4, IL-8, and PLA2 levels were elevated in patients with NIP; LTB4 and PLA2 levels correlated with absolute neutrophil count, and IL-8 correlated with alveolar-arterial oxygen pressure difference. IL-8 was elevated in the asymptomatic HIV-positive patients, and there was a trend toward elevation of PLA2 in this group. CONCLUSION: IL-8 appears to play a role in the pathogenesis of lung injury in P carinii pneumonia and may be the principal neutrophil chemotaxin in this disease; PLA2 may also be involved in the pathogenesis of P carinii pneumonia. Both LTB4 and IL-8 may be involved in the recruitment of neutrophils and subsequent lung injury of NIP. These data suggest that there are varying mechanisms by which inflammatory cells are recruited to the lung in different HIV-related lung diseases.

Reduction of pulmonary surfactant in patients with human immunodeficiency virus infection and Pneumocystis carinii pneumonia.

We assessed qualitative and quantitative differences in surfactant lipid composition of bronchoalveolar lavage (BAL) fluid in patients with acquired immune deficiency syndrome (AIDS) and Pneumocystis carinii (PC) pneumonia. Five normal volunteers and 27 patients with human immunodeficiency virus (HIV) infection underwent BAL for evaluation of possible pulmonary infection. Bronchoalveolar lavage studies in eight patients were negative for PC organisms, and 19 were positive. Pneumocystis carinii pneumonia was graded (mild vs moderate to severe) by initial alveolar-arterial oxygen gradient. Bronchoalveolar lavage fluid was centrifuged, the lipids were extracted from the supernatant, and total lipid profiles of dephosphorylated glycerolipids were analyzed as trimethylsilylether derivatives by high temperature gas-liquid chromatography. Phospholipase A2 levels were determined using a radiolabeled E coli membrane method. Compared to the normal volunteers (109 +/- 13 micrograms/5 ml) and the PC negative group (107 +/- 13 micrograms/5 ml), total BAL lipid was reduced for both the mild PC pneumonia group (73 +/- 10 micrograms/5 ml) and the moderate to severe PC pneumonia group (46 +/- 4 micrograms/5 ml). There was a parallel reduction of diacylglycerol lipids: normal volunteers, 52 +/- 7 micrograms/5 ml; PC negative, 52 +/- 9 micrograms/5 ml; mild PC pneumonia, 35 +/- 7 micrograms/5 ml; and moderate to severe PC pneumonia, 15 +/- 2 micrograms/5 ml. Phospholipase A2 activity in moderate to severe PC pneumonia was twice that of the PC negative patients, and 30 times that for normals. The data demonstrate a marked diminution in surfactant glycerophospholipid in patients with AIDS and PC pneumonia and suggest a potential role for surfactant abnormality in the pathophysiology of this disease.

Improved diagnosis of Pneumocystis carinii infection by polymerase chain reaction on induced sputum and blood.

Detection of Pneumocystis carinii by the polymerase chain reaction (PCR) may facilitate non-invasive diagnosis of P carinii pneumonia and study of its epidemiology. We have compared the sensitivity and specificity of two PCR methods with those of conventional staining for detection of P carinii in induced sputum, bronchoalveolar lavage fluid (BAL), and blood. Of 71 sputum samples, 17 were from patients with microbiologically confirmed P carinii pneumonia. A nested PCR method correctly identified the presence of P carinii in all 17 (100% sensitive, 95% confidence interval [CI] 81-100%) and found no organisms in 50 of 54 microbiologically negative samples (93% specific, 95% CI 82-98%). PCR with a single primer pair was 71% sensitive (44-90%) and 94% specific (85-99%). The sensitivity of conventional staining methods (direct and indirect fluorescence antibody and toluidine-blue-O tests) was significantly less (38-53%) than that of nested PCR (p less than 0.05). In BAL, neither PCR method was significantly better than the conventional staining methods. P carinii was detected in BAL or sputum from 10 immunocompromised patients without microbiological evidence of P carinii pneumonia, which suggests that symptom-free carriers or subclinical infection can exist. P carinii was detected by nested PCR in blood from 2 of 3 patients with disseminated pneumocystosis but in only 1 of 11 patients with P carinii infection restricted to the lungs. Nested PCR on induced sputum is more sensitive than conventional staining methods for the diagnosis of P carinii pneumonia and provides a non-invasive method of detecting disseminated disease.

Polyamine metabolism in Pneumocystis carinii.

Alpha-difluoromethylornithine (DFMO) is being used to treat Pneumocystis carinii pneumonia despite a lack of in vitro evidence supporting its antipneumocystis activity. DFMO is a specific inhibitor of ornithine decarboxylase, the rate-limiting enzyme of polyamine biosynthesis. To investigate polyamine metabolism in P. carinii, extracts of the organism were analyzed for polyamine content and ornithine decarboxylase activity, and [3H]ornithine and [14C]arginine incorporation into polyamines during short-term culture was determined. P. carinii extracts contained putrescine and spermidine in a ratio of 0.17:1; traces of spermine were detected. Although ornithine decarboxylase activity was not detected, P. carinii incorporated ornithine and arginine into putrescine and spermidine but not into spermine, suggesting that the spermine detected derived from contaminating host cells. Uninfected rat lung incorporated ornithine minimally. Pentamidine, DFMO, and alpha-monofluoromethyldehydroornithine methyl ester inhibited ornithine incorporation by up to 86% at clinically achievable concentrations. These data provide a rationale for using polyamine synthesis antagonists in P. carinii pneumonia and a method for screening antipneumocystis drugs in vitro.

Purification and characterization of a major human Pneumocystis carinii surface antigen.

Previous studies of Pneumocystis carinii have identified the major surface antigen of rat and human isolates as proteins of 116,000 and 95,000 mol wt, respectively, that are antigenically not identical. In this study both rat and human P. carinii proteins were purified by solubilization with zymolyase followed by molecular sieve and ion exchange chromatography. The native proteins had an apparent mol wt of 290,000 or greater, based on molecular sieve studies as well as cross-linking studies. Both proteins were glycoproteins; treatment with endoglycosidase H resulted in a 9% decrease in mol wt. The carbohydrate composition of the rat P. carinii glycoprotein was distinct from the human isolate; glucose, mannose, galactose, and glucosamine occurred in approximately equimolar ratios in the human P. carinii protein, whereas glucose and mannose were the predominant sugars of the rat P. carinii protein. To evaluate humoral immune responses to the human P. carinii protein, an enzyme-linked immunosorbent assay using purified protein was developed. Some, but not all, patients who subsequently developed P. carinii pneumonia demonstrated a serum antibody response to the surface antigen. Nearly all subjects without a history of P. carinii pneumonia had no detectable antibodies. Purified P. carinii proteins will greatly facilitate the investigation of host-P. carinii interactions.

Atypical pathologic manifestations of Pneumocystis carinii pneumonia in the acquired immune deficiency syndrome. Review of 123 lung biopsies from 76 patients with emphasis on cysts, vascular invasion, vasculitis, and granulomas.

The frequency of atypical pathologic manifestations of Pneumocystis carinii pneumonia (PCP) were studied in 123 lung biopsy specimens from 76 National Institutes of Health patients with the acquired immune deficiency syndrome. The following atypical features were observed: interstitial (63%) and intraluminal (36%) fibrosis, absence of alveolar exudate (19%), numerous alveolar macrophages (9%), granulomatous inflammation (5%), hyaline membranes (4%), marked interstitial pneumonitis (3%), parenchymal cavities (2%), interstitial microcalcification (2%), minimal histologic reaction (2%), and vascular invasion with vasculitis (1%). These atypical features are discussed with emphasis on the significance of cavities, vascular invasion, vasculitis, and granulomas. Immunohistochemical staining with monoclonal antibodies to the 2G2 and 6B8 antigens of P carinii in paraffin-embedded lung biopsy specimens did not indicate any diagnostic advantage over routine methenamine silver stains. This study provides an important reminder that a wide variety of pathologic manifestations may occur in PCP in human immunodeficiency virus-infected patients and that atypical features should be sought in lung biopsies from patients at risk for PCP.

Management of tuberculous pericarditis.

The cases of 17 patients with tuberculous pericarditis were reviewed. Thirteen patients had effusive pericarditis, and 10 had surgical drainage of the effusion. No deaths were due to pericardial tamponade; this appears to be related to earlier recognition of major pericardial effusions by echocardiography. In 2 patients clinical evidence of pericardial constriction developed while they were on a regimen of therapy, and in another 2 patients, echocardiography revealed pericardial thickening after resolution of the effusion. A pericardial window is recommended for the short-term management of patients suspected of having tuberculous pericarditis with a major pericardial effusion by echocardiography. If a thickened pericardium is found during the window procedure, early pericardiectomy is strongly encouraged.

Synthesis and content of polyamines in bloodstream Trypanosma brucei.

The sensitive dansyl procedure was used to detect putrescine and spermidine, but not spermine and cadaverine, in pleomorphic Trypanosoma brucei. The polyamines were synthesized in vitro from [3H]ornithine, [14C]arginine and [14C]methionine. Proline, agmatine, and citrulline, but not glutamine, glutamic or pyroglutamic acids, stimulated spermidine formation from [4C]methionine. Putrescine and sperimidine synthesis occurred rapidly from ornithine: putrescine synthesis peaked in 0.5 h, spermidine in 1 h. Trypanosoma brucei assimilated exogenous 14C-labeled putrescine, spermidine, and spermine; spermidine and spermine were taken up 5 times as rapidly as putrescine. Polyamine syntheses may therefore be a practical target for novel trypanocies.

Polyamines in trypanosomatids.

Polyamines were determined by n-butanol extraction and thin-layer chromatography in four trypanosomatids: Trypanosoma brucei (rat infection) and cultures of Crithidia fasciculata, Leptomonas sp., and Trypanosoma mega. All had putrescine and spermidine but no detectable spermine. Putrescine and spermidine levels were quantitated for extracts of leptomonas during the normal growth cycle. Spermidine values peaked 18 h before peak cell populations. Spermidine-putrescine ratios for all organisms were related to the presumed phylogeny of the group.