James W. Leatherman

Alveolar Hemorrhage Syndromes: Diffuse Microvascular Lung Hemorrhage in Immune and Idiopathic Disorders

We have reviewed the alveolar hemorrhage (AH) syndromes, defined as immune or idiopathic disorders associated with diffuse microvascular hemorrhage into the acinar portion of the lung. The disorders that are most often associated with AH include antibasement membrane antibodies (ABMA) disease, idiopathic pulmonary hemosiderosis, systemic lupus erythematosus, systemic vasculitides, and idiopathic rapidly progressive glomerulonephritis. An approach to the recognition, diagnosis, and treatment of the AH syndromes has been outlined and several illustrative case studies have been presented. Recognition of AH is not usually difficult, but does require a high index of suspicion, since many disease processes may give rise to hemoptysis with infiltrates on chest roentgenogram. Recognition of AH is aided by careful clinical and laboratory assessment for evidence of extrapulmonary disease; simple hematologic studies such as sequential hemoglobins and iron studies; and measurement of carbon monoxide uptake by the lungs. Early recognition of AH may decrease the likelihood of respiratory failure and end-stage renal disease. The specific etiology of AH is usually determined by clinical examination, serologic assay for ABMA, and percutaneous renal biopsy by immunofluorescence. Open-lung biopsy is required in a minority of cases. High-dose pulse methylprednisolone appears to effectively control AH of diverse etiology. Combined plasma exchange and immunosuppression controls AH in ABMA disease and is the treatment of choice in this disorder. Cyclophosphamide is used for Wegeners granulomatosis, and sometimes in systemic necrotizing vasculitis, in an attempt to prevent irreversible damage to the kidneys.

Lung T Cells in Hypersensitivity Pneumonitis

Monoclonal antibodies OKT3 (all T cells), OKT4 (T-helper/inducer), and OKT8 (T-suppressor/cytotoxic) were used to determine surface phenotypes of bronchoalveolar lavage and peripheral blood lymphocytes in patients with chronic hypersensitivity pneumonitis. Similar studies were done in asymptomatic pigeon breeders, patients with sarcoidosis, and nonsmoking controls. Increased numbers of lavage T cells were found in patients with hypersensitivity pneumonitis and sarcoidosis and in asymptomatic pigeon breeders. The predominant T-cell subset in patients with hypersensitivity pneumonitis and in asymptomatic pigeon breeders was T8 +; in contrast, the predominant subset in those with sarcoidosis was T4 +. Peripheral blood T-cell subsets were normal in all groups. Thus, most lung T lymphocytes in chronic hypersensitivity pneumonitis belong to the T8 + subset; the local cellular immune response in hypersensitivity pneumonitis and sarcoidosis are different; and the pattern of alveolitis, as determined by bronchoalveolar lavage, is not the sole determinant of lung impairment after exposure to hypersensitivity pneumonitis antigens.

Effect of prolongation of expiratory time on dynamic hyperinflation in mechanically ventilated patients with severe asthma

Objective:To assess the effect of a decrease in respiratory rate on dynamic hyperinflation, as determined by changes in plateau airway pressure, in patients with status asthmaticus whose baseline minute ventilation approximated 10 L/min. Design:Observational descriptive study. Setting: Medical intensive care unit. Patients:Twelve patients with severe asthma mechanically ventilated in the assist control mode with a tidal volume of 613 ± 100 mL and an inspiratory flow rate of 79 ± 4 L/min. Interventions:A decrease in respiratory rate from 18 to 12 and 6 breaths/min. Measurements and Main Results:Plateau airway pressure decreased by approximately 2 cm H2O (25.4 ± 2.8 vs. 23.3 ± 2.6 cm H2O, p < .01) when respiratory rate was decreased from 18 to 12 breaths/min (increase in expiratory time 1.7 secs) and by a similar amount (23.3 ± 2.6 vs. 21.3 ± 2.9 cm H2O, p < .01) when respiratory rate was decreased from 12 to 6 breaths/min (increase in expiratory time 5 secs). Peak airway pressure was similar at the three respiratory rates (66.8 ± 8.7 vs. 66.4 ± 9.5 vs. 67.8 ± 11.1 cm H2O at 18, 12, and 6 breaths/min, respectively). End-expiratory flow rates (n = 7) were 61.4 ± 12.6, 38.6 ± 4.5, and 23.1 ± 5.8 mL/sec at respiratory rates of 18, 12, and 6 breaths/min, respectively. Conclusions:Prolongation of expiratory time decreases dynamic hyperinflation in patients with status asthmaticus, as evidenced by a reduction in plateau airway pressure, but the magnitude of this effect is relatively modest when baseline minute ventilation is ≤10 L/min, because of the low end-expiratory flow rates. Since flow progressively decreases throughout expiration, the reduction in dynamic hyperinflation resulting from a given prolongation of expiratory time will depend on the baseline respiratory rate (i.e., less reduction in dynamic hyperinflation at a lower respiratory rate). Changes in peak airway pressure may not always reflect the changes in dynamic hyperinflation that result from prolongation of expiratory time.

Diffuse intrapulmonary hemorrhage and glomerulonephritis unrelated to anti-glomerular basement membrane antibody

Nine patients with diffuse intrapulmonary hemorrhage and glomerulonephritis not due to anti-glomerular basement membrane (anti-GBM) antibody are described and similar previously reported cases are reviewed. Eight patients were seen during a four-year interval and represented 47 percent of the cases of pulmonary hemorrhage and glomerulonephritis seen during this period. Diagnoses included systemic vasculitis of unspecified type in two patients with seropositive rhematoid arthritis, idiopathic crescentic glomerulonephritis with negative immunofluorescence in two, Wegeners granulomatosis in two, and polyarteritis nodosa, Henoch-Schönlein purpura, and mixed connective tissue disease in one each. Differentiation from anti-GBM antibody-mediated pulmonary hemorrhage and glomerulonephritis by clinical evaluation alone was frequently difficult, emphasizing the importance of both immunopathologic studies and evaluation of serum for anti-GBM antibody in all patients with pulmonary hemorrhage and glomerulonephritis. In eight of nine patients, significant episodes of pulmonary hemorrhage improved markedly within 24 to 72 hours following initiation of high-dose corticosteroid therapy. In contrast, renal function did not improve in the majority of patients.

Point-of-care ultrasound to estimate central venous pressure: A comparison of three techniques

Objective:To determine the most accurate predictor of central venous pressure among three point-of-care venous ultrasound techniques. Design:Cross-sectional study. Setting:Medical ICU in an academic medical center. Patients:Convenience sample of 67 spontaneously breathing patients who had an intrathoracic central venous catheter to allow measurement of central venous pressure. Intervention:Measurement of the internal jugular vein height to width ratio (aspect ratio), the inferior vena cava diameter, and the percent collapse of the inferior vena cava with inspiration (collapsibility index) by ultrasound. Measurements and Main Results:Complete data for analysis were available in 65 patients, as the inferior vena cava could not be visualized in two patients. A central venous pressure of 10 mm Hg was chosen a priori as a clinically significant cutoff. The range of central venous pressure values was 1–23 mm Hg with a median value of 7 mm Hg. The maximal inferior vena cava diameter correlated moderately with central venous pressure (R2 = 0.58), whereas the inferior vena cava collapsibility index and the internal jugular vein aspect ratio showed poor correlation (R2 = 0.16 and 0.21, respectively). The area under the receiver operating characteristics curve (area under the curve) to discriminate a low central venous pressure (< 10 mm Hg) was 0.91 for inferior vena cava diameter (95% confidence interval 0.84–0.98), which was significantly higher than the internal jugular vein aspect ratio (area under the curve 0.76; 95% confidence interval 0.65–0.89) or the inferior vena cava collapsibility index (area under the curve 0.66; 95% confidence interval 0.51–0.80) (p = 0.0001). An inferior vena cava diameter < 2 cm predicted a central venous pressure < 10 mm Hg with a sensitivity of 85% (95% confidence interval 69% to 94%), specificity of 81% (95% confidence interval 60% to 93%), and positive predictive value of 87% (95% confidence interval 71% to 95%). Inferior vena cava collapsibility index was not an independent predictor of central venous pressure after adjusting for inferior vena cava diameter in a multiple linear regression model. Conclusion:Among spontaneously breathing patients largely without vasopressor support, the maximal inferior vena cava diameter is a more robust estimate of central venous pressure than the inferior vena cava collapsibility index or the internal jugular vein aspect ratio.

Interpretation of the pulmonary artery occlusion pressure in mechanically ventilated patients with large respiratory excursions in intrathoracic pressure

Objective: To assess the reliability of the pulmonary artery occlusion pressure (Ppao) when respiratory excursions in intrathoracic pressure are prominent.Design: We studied 24 critically ill patients who had 15 mmHg or more of respiratory excursion in their Ppao tracing. Large respiratory excursions resulted from respiratory muscle activity that persisted despite sedation and mechanical ventilation in the assist-control mode. From the Ppao tracing, the end-expiratory and mid-point values were recorded; the latter was measured halfway between end-expiration and the nadir due to inspiratory triggering. The Ppao was then re-measured after administration of a non-depolarizing muscle relaxant.Setting: Medical intensive care unit of a university-affiliated teaching hospital.Measurements and results: The difference between the pre-relaxation end-expiratory Ppao and the relaxed Ppao was larger than the difference between the pre-relaxation mid-point Ppao and the relaxed Ppao (11 ± 5 vs 3 ± 3 mmHg, p<0.01). In 21 of 24 (88 %) cases, the relaxed Ppao was more closely approximated by the mid-point Ppao than by the end-expiratory Ppao. The difference between the end-expiratory Ppao and the relaxed Ppao increased as the amount of respiratory excursion increased (r=0,51; p<0.01).Conclusions: In mechanically ventilated patients whose respiratory muscles produce large excursions in the Ppao, the end-expiratory Ppao is often much higher than the Ppao measured after muscle relaxation. The pre-relaxation mid-point Ppao and the relaxed Ppao are usually similar, but this may not be true in individual patients. In this setting, the Ppao measured after muscle relaxation probably provides the most clinically reliable estimate of left heart filling pressure.

Neuromuscular disorders in the intensive care unit

Neuromuscular disorders encountered in the ICU can be categorized as muscular diseases that lead to ICU admission and those that are acquired in the ICU. This article discusses three neuromuscular disorders can lead to ICU admission and have a putative immune-mediated pathogenesis: the Guillian-Barré syndrome, myasthenia gravis, and dermatomyositis/polymyositis. It also reviews critical care polyneuropathy and ICU acquired myopathy, two disorders that, alone or in combination, are responsible for nearly all cases of severe ICU acquired muscle weakness.

Overestimation of pulmonary artery occlusion pressure in pulmonary hypertension due to partial occlusion

ObjectiveTo evaluate partial occlusion in patients with pulmonary hypertension with regard to a) the degree to which it leads to overestimation of pulmonary artery occlusion pressure (Ppao) and b) identification of factors that could enhance its recognition. DesignObservational descriptive study. SettingMedical intensive care unit. PatientsFourteen patients with pulmonary hypertension and an increased pulmonary artery diastolic pressure (Ppad) − Ppao gradient (≥10 mm Hg). InterventionsNone. Measurements and Main ResultsThe Ppao was recorded during partial occlusion (partial Ppao) and after catheter repositioning to obtain a lower, more accurate value (best Ppao). The error due to partial occlusion, defined as the difference between the partial Ppao and the best Ppao, was 13 ± 5 mm Hg (range, 6–21 mm Hg). The previously widened Ppad − Ppao gradient invariably narrowed during partial occlusion and then increased by 13 ± 5 mm Hg (range, 5–23) during the best Ppao measurement. There was a moderate correlation between the error due to partial occlusion (partial Ppao − best Ppao) and both the mean pulmonary artery pressure (r = .77, p < .01) and the Ppad − Ppao gradient (r = .79, p < .01). ConclusionsPartial occlusion in patients with pulmonary hypertension may lead to significant overestimation of the Ppao and should be suspected when there is a substantial increase in the Ppao without a concomitant increase in the Ppad, as reflected by a marked narrowing of a previously widened Ppad − Ppao gradient.

High Prevalence of Hyperamylasemia in Patients with Acidemia

Excerpt A diagnosis of acute pancreatitis usually depends on the finding of elevated serum amylase activity. Although a low-grade elevation of serum amylase is a relatively non-specific finding, mo...

Lack of Benefit of Heliox During Mechanical Ventilation of Subjects With Severe Air-Flow Obstruction

BACKGROUND: The value of heliox (helium-oxygen mixture) for patients with severe air-flow obstruction is uncertain. The purpose of this study was to determine whether heliox could reduce the degree of hyperinflation and hypercapnia in mechanically ventilated patients with severe air-flow obstruction. METHODS: This was a single-center, prospective observational study conducted in a medical ICU of an academic medical center. We assessed the impact of heliox (65–70% helium, 30–35% oxygen) on airway pressures and arterial blood gases of 13 subjects undergoing mechanical ventilation for severe asthma (n = 8) or exacerbation of COPD (n = 5). RESULTS: As compared with ventilation with air-O2, heliox resulted in a reduction in peak airway pressure (54.1 ± 12.6 cm H2O vs 47.9 ± 10.8 cm H2O, P < .001) and PaCO2 (64.3 ± 14.9 mm Hg vs 62.3 + 15.1 mm Hg, P = .01). In contrast, there was no change in plateau pressure (25.3 ± 5.5 cm H2O vs 25.8 ± 5.6 cm H2O, P = .14) or total PEEP (13.4 ± 3.8 cm H2O vs 13.3 ± 4.1 cm H2O, P = .79) in response to heliox. CONCLUSIONS: In mechanically ventilated subjects with severe air-flow obstruction, administration of heliox had no effect on indices of dynamic hyperinflation (plateau pressure and total PEEP) and resulted in only a small reduction in PaCO2.