The technique of weaning from tracheostomy. Criteria for weaning; practical measures to prevent failure

Use the following organized approach to determine whether a patient can be weaned from tracheostomy. Consider airway decannulation only if the original upper airway obstruction has resolved, if mechanical ventilation is no longer needed, and if airway secretions are controlled. Regard the presence of a vigorous cough and the absence of aspiration as additional portents of success. Most critically ill patients benefit from a well-planned, progressive weaning protocol. The tracheostomy button is an ideal weaning device; it maintains the stoma tract and allows the patient to breathe and clear secretions through the upper airway. Monitor the patient for up to 48 hours to ensure tolerance to decannulation.

The technique of tracheotomy and cricothyroidotomy. When to operate--and how to manage complications

Tracheotomy can relieve upper airway obstruction, improve pulmonary hygiene, and support long-term mechanical ventilation. Consider performing a tracheotomy whenever the need for more than 14 days of ventilatory support is anticipated. When emergent airway access is needed and translaryngeal intubation is not possible, consider cricothyroidotomy. For a tracheotomy, make a transverse incision 1 cm above the suprasternal notch or, for cricothyroidotomy, through the superficial cricothyroid membrane. Accidental tube displacement within 5 days of surgery is potentially tracheotomy's most lethal early complication. Many late complications can be prevented by careful management and expert nursing support.

Pleural fluid chemical analysis in parapneumonic effusions. A meta-analysis

Controversy exists regarding the clinical utility of pleural fluid pH, lactate dehydrogenase (LDH), and glucose for identifying complicated parapneumonic effusions that require drainage. In this report, we performed a meta-analysis of pertinent studies, using receiver operating characteristic (ROC) techniques, to assess the diagnostic accuracy of these tests, to determine appropriate decision thresholds, and to evaluate the quality of the primary studies. Seven primary studies reporting values for pleural fluid pH (n = 251), LDH (n = 114), or glucose (n = 135) in pneumonia patients were identified. We found that pleural fluid pH had the highest diagnostic accuracy for all patients with parapneumonic effusions as measured by the area under the ROC curve (AUC = 0.92) compared with pleural fluid glucose (AUC = 0.84) or LDH (AUC = 0.82). After excluding patients with purulent effusions, pH (AUC = 0.89) retained the highest diagnostic accuracy. Pleural fluid pH decision thresholds varied between 7.21 and 7.29 depending on cost-prevalence considerations. The quality of the primary studies was the major limitation in determining the value of pleural fluid chemical analysis. We conclude that meta-analysis of the available data refines the application of pleural fluid chemical analysis but a clearer understanding of the usefulness of these tests awaits more rigorous primary investigations.

Management of parapneumonic effusions. An analysis of physician practice patterns

OBJECTIVE

To evaluate physician practices in managing patients with parapneumonic effusions and the impact of practice patterns on clinical outcome.

DESIGN

Case series.

SETTING

Private, tertiary care medical center.

PATIENTS

Thirty-nine hospitalized patients with complicated parapneumonic effusions and a separate group of 191 patients admitted with community-acquired pneumonia.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Evaluation of physician practice patterns in managing complicated parapneumonic effusion and the impact of delaying thoracentesis (> or = 2 days after pleural fluid detection) or pleural drainage (> or = 2 days after pleural fluid criteria for drainage fulfilled) on duration of hospitalization, cost of hospitalization, and need for thoracotomy.

RESULTS

Thirty-eight of the 39 patients with complicated parapneumonic effusions underwent thoracentesis that was "delayed" (5.7 +/- 3.1 days) in 16 patients. Delays in thoracentesis were associated with longer hospitalizations (P = .02). Laboratory tests ordered on nonpurulent pleural fluid were incomplete for 16 of 38 patients. Chest tube or surgical pleural drainage was delayed (4.2 +/- 3.5 days) in 10 of 38 patients who underwent thoracentesis. Delays in initiating drainage were associated with prolonged hospitalization (P = .04). Delaying interventions accounted for a mean cost increment per patient of $8462 for delayed thoracentesis and $9332 for delayed drainage. Of the 191 patients with community-acquired pneumonia, 99 (52%) had pleural effusions but only 15 (15%) underwent thoracentesis.

CONCLUSIONS

Physicians commonly delay thoracentesis and chest tube drainage to observe parapneumonic effusions for improvement. This practice pattern is associated with longer and more costly hospitalizations.

Urinary excretion of polyamines in the adult respiratory distress syndrome

Polyamines are low molecular weight polycations that are critically important in cellular proliferation and differentiation. To investigate their potential role in acute lung injury, the polyamines spermidine, spermine, and putrescine were measured in 24-h urine collections from intubated patients with ARDS (n = 12) or congestive heart failure with cardiogenic pulmonary edema (CHF, n = 10) and in normal subjects (n = 10). Mean concentrations of putrescine were similar between groups, but spermidine concentrations in patients with ARDS (52.7 +/- 19.7 nmol/mg creatinine) were significantly higher than in normal subjects (4.9 +/- 0.7 nmol/mg), p < .05. Mean concentrations of spermine in ARDS (270.6 +/- 78.1 nmol/mg) were higher than in CHF (1.0 +/- 0.5 nmol/mg), p < .05, and normal subjects (0.3 +/- 0.1 nmol/mg), p < .05. Concentrations of putrescine increased significantly during the first 7 days of ARDS (241.5 +/- 127.1% above baseline, n = 6), p < .05. Urinary polyamine excretion did not correlate with severity of gas exchange or death. These results are the first to suggest a potential role for polyamines in the pathophysiology of ARDS.

Interventional radiology of the chest: image-guided percutaneous drainage of pleural effusions, lung abscess, and pneumothorax

Percutaneous catheter drainage of intrathoracic collections has developed as a natural extension of similar interventional radiologic procedures in the abdomen. The advent of CT and sonography, which allow detection and characterization of pleural and parenchymal collections, combined with advances in drainage catheter design and interventional techniques, have made imaging-guided management of intrathoracic collections a safe and effective alternative to traditional surgical therapy. This article begins with a review of the etiology, pathophysiology, diagnosis, and treatment of parapneumonic pleural effusion, which remains the most common indication for image-guided percutaneous drainage. Subsequent sections consider issues related to percutaneous drainage of malignant pleural effusion, lung abscess, and pneumothorax.

Intravenous eugenol causes hemorrhagic lung edema in rats: proposed oxidant mechanisms

Although eugenol, the active phenolic constituent of oil of cloves, has been implicated as a cause of noncardiogenic pulmonary edema, the mechanism of lung injury is unknown. We studied the effects of intravenous infusion of eugenol in rats and found that 4 microliters and 8 microliters of eugenol (6.52 mol/L) caused acute respiratory distress with hemorrhagic pulmonary edema. Histologic features included perivascular, interstitial, and alveolar edema with extravasation of red blood cells and neutrophils into the alveolar space and alveolar capillary trapping of neutrophils. In addition, lungs treated with eugenol had increased bronchoalveolar lavage fluid (BALF) protein content, and lung wet-to-dry weight ratios were increased in animals treated with 8 microliters eugenol. Pretreatment with intravenous superoxide dismutase (SOD) or catalase but not dimethylthiourea (DMTU) decreased BALF protein content after infusion of 4 microliters and 8 microliters of eugenol. SOD and catalase but not DMTU decreased lung wet-to-dry weight ratios in animals infused with 8 microliters of eugenol. We conclude that intravenous infusion of eugenol causes hemorrhagic pulmonary edema with intrapulmonary sequestration of neutrophils and suggest that the injury may be at least partly oxidant mediated.

Clinical efficacy of doxycycline for pleurodesis

To determine the efficacy of doxycycline as a pleural sclerosing agent, we examined the outcomes in 31 patients (aged 31 to 87 years) receiving doxycycline (500 to 1,000 mg) through a chest tube for malignant pleural effusions or persistent bronchopleural fistulae. Of the 27 patients with malignant pleural effusions, 21 patients had a complete short-term response (no fluid reaccumulation during the initial hospitalization); 5 of the 6 short-term nonresponders had partial control of effusions, with improvement in respiratory symptoms. Of the 23 patients who survived longer than 1 month, 15 patients did not have reaccumulation of fluid during follow-up. All four patients with persistent bronchopleural fistulae had resolution of their air leaks; one patient had recurrence with a partial pneumothorax. Pleural pain controllable with narcotic therapy was the only important complication. Thus, doxycycline is a suitable substitute for tetracycline as a pleural sclerosing agent.

Thromboxane contributes to pulmonary hypertension in ischemia-reperfusion lung injury

Exposure of isolated perfused rabbit lungs (IPL) to ischemia-reperfusion causes a transient increase in pulmonary arterial (PA) pressure at the onset of reperfusion. Because thromboxane A2 (TxA2) is a potent vasoconstrictor, we hypothesized that it may contribute to the ischemia-reperfusion-induced pressor response. To evaluate this hypothesis, we exposed IPL perfused with a cell-free solution to 40 min of warm ischemia followed by reperfusion and measured perfusate immunoreactive thromboxane B2 (iTxB2) and 6-ketoprostaglandin F1 alpha (i6-keto-PGF1 alpha). We observed that ischemia-reperfusion IPL compared with controls had an increase in PA pressure (40.2 +/- 4.8 vs. 9.3 +/- 0.3 mmHg, P < 0.05), lung edema (29.3 +/- 6.3 vs. -0.2 +/- 0.2 g, P < 0.05), iTxB2 perfusate levels (155 +/- 22 vs. < 50 pg/ml, P < 0.05), and i6-keto-PGF1 alpha (436 +/- 33 vs. 61 +/- 16 pg/ml, P < 0.05). In ischemia-reperfusion IPL, infusion of SQ 29548 (10(-6) M), a specific TxA2/prostaglandin H2 receptor antagonist, attenuated the PA pressor response and the degree of edema. We conclude that pulmonary hypertension associated with ischemia-reperfusion results in part from pulmonary release of TxA2. Furthermore, TxA2 directly through membrane effects or indirectly through hydrostatic mechanisms increases the severity of ischemia-reperfusion-induced lung edema.

Pleural disease in pregnancy

Pleural effusions, pneumomediastinum, and pneumothorax are known complications of pregnancy. Although reported in small series and anecdotal case reports, the serious nature of these complications and the potential for misdiagnosis during the events of labor and delivery warrant a careful review of the available literature. In this article the incidence, clinical manifestations, and, where appropriate, therapeutic options of these disorders are discussed.

Positive pressure mechanical ventilation augments left ventricular function in acute mitral regurgitation

Although inconclusively established, positive pressure ventilation may augment cardiac function in congestive cardiomyopathies. We report a patient with acute mitral regurgitation who experienced enhanced myocardial performance and resolution of large pulmonary artery v waves during mechanical ventilation. This observation supports the existence of a cardiac booster effect from positive pressure ventilation.

Platelet prevention of oxidant lung oedema is not mediated through scavenging of hydrogen peroxide

Previous studies have shown that washed human platelets attenuate oxidant oedema in isolated perfused rabbit lungs through mechanisms dependent on platelet glutathione. We hypothesized that the platelet glutathione redox cycle scavenges hydrogen peroxide in this model and thereby protects vascular endothelial cells from oxidant injury. This hypothesis was tested by asking two questions: (1) do glutathione-supplemented platelets demonstrate augmented lung protection compared with control platelets, and (2) does conjugation of platelet glutathione with 1-chloro-2,4-dinitrobenzene or inactivation of catalase with 3-amino-1,2,4-triazole decrease in vitro platelet metabolism of hydrogen peroxide? We incubated washed human platelets with reduced glutathione or glutathione monoester and observed platelet glutathione contents of 181% and 189%, respectively, compared with control values. Incubation of platelets with N-acetylcysteine did not alter platelet glutathione content. Infusion of glutathione-supplemented platelets into isolated lungs injured by purine and xanthine oxidase did not augment platelet protection compared with untreated platelets. We also found that conjugation of platelet glutathione and/or inactivation of platelet catalase did not decrease the rate constant for platelet metabolism of hydrogen peroxide. We conclude that platelets attenuate oxidant lung oedema through glutathione-dependent mechanisms other than direct scavenging of hydrogen peroxide.

Diagnostic value of pleural fluid cytology in occult Boerhaave's syndrome

When Boerhaave's syndrome presents with atypical clinical features and eludes prompt diagnosis, delays in surgical therapy increase complications and mortality. We present a patient with occult Boerhaave's syndrome who had nondiagnostic esophageal contrast studies and thoracic computed tomography. Pleural fluid cytologic analysis established the presence of esophageal rupture by detecting undigested food particles.

Vascular erosion by central venous catheters. Clinical features and outcome

We evaluated the clinical characteristics of eight patients who presented with vascular erosion from central venous catheters and reviewed the available literature. Patients typically presented with dyspnea or chest pain, unilateral or bilateral pleural effusions, and mediastinal widening one to seven days after catheter insertion. Pleural fluid appeared transudative with variable glucose concentrations (range, 174 to 588 mg/dl) that were always greater than concurrent serum values. Diagnosis was delayed 3.0 +/- 1.5 days (range, 0 to 11 days) after vascular erosion. One patient died and four patients received chest tubes. Seven of eight patients had left-sided line placement; six of these seven left-sided catheters abutted the superior vena cava wall within approximately 45 degrees of perpendicular. Results of a literature search confirm the hazards of delayed diagnosis and the importance of left-sided catheter placement as a risk factor for vascular erosion.

Bowel infarction as the initial manifestation of disseminated aspergillosis

Disseminated aspergillosis in the immunocompromised patient most commonly presents with clinically apparent pulmonary involvement and roentgenographic infiltrates. We report a patient with acute myelogenous leukemia who developed bowel infarction due to gastrointestinal invasion of Aspergillus fumigatus as the initial manifestation of widespread fungal disease.

Special critical care considerations in tracheostomy management

The tracheotomized patient undergoing mechanical ventilation presents numerous challenges to the intensive care team. During the initial phase of respiratory failure, patient instability and risks of multiorgan failure focus efforts on an array of critical care management techniques designed to reverse the underlying process and prevent complications. During the stabilization phase, issues of tracheostomy care become equally important in improving patient outcome. These topics include the proper assistance in patient communication, initiation of enteral nutrition, weaning from airway cannulation, and anticipation of adverse reactions after airway decannulation. Failure in promoting a logically conceived and carefully applied treatment plan in any of these areas frequently delays patient recovery and risks serious complications of airway compromise.

Timing of tracheotomy in ventilator-dependent patients

During the last 20 years, improved critical care techniques have enhanced the probability that the condition of patients with respiratory failure will stabilize sufficiently to allow long-term mechanical ventilation. Patients undergoing the transition to prolonged ventilatory support benefit from a timely application of tracheotomy guided by a clear understanding of its risk and benefits. Although numerous investigations since 1970 compare patient outcome from tracheotomy with that after prolonged translaryngeal intubation, limitations of study design and varying results among institutions prevent absolute recommendations for timing tracheotomy. A critical review of the available data, however, allows individualization of care and an anticipatory approach to institution of the surgical airway.

Atrial natriuretic peptide inhibits oxidant-induced increases in endothelial permeability

Chemically and enzymatically generated oxidants alter endothelial cell shape, increase macromolecular permeability across endothelial cell monolayers, and increase lung microvascular permeability. We examined the effect of ANP (atrial natriuretic peptide) on oxidant-induced injuries to bovine aortic endothelial cell monolayers and to isolated, perfused rabbit lungs. Treatment of cultured endothelial monolayers with glucose oxidase (1.4 U/ml) caused changes in cell shape characterized by a retraction of cells and the formation of numerous intercellular gaps. Glucose oxidase treatment also caused a reduction in F-actin stress fibers visualized by rhodamine-phalloidin fluorescence. Pretreatment (5 min) of the endothelial monolayers with ANP (10(-7) M) attenuated the oxidant-induced changes in cell shape and reduction in F-actin staining. In addition, ANP significantly (P less than 0.05) reduced increases in endothelial monolayer permeability to albumin resulting from glucose oxidase treatment. Oxidant-induced injury of isolated, perfused rabbit lungs produced pulmonary edema measured as an increase in lung weight. This increase in weight was significantly (P less than 0.05) inhibited by pretreatment of lungs with ANP (10(-7) M). Collectively, these results suggest that ANP may act to preserve endothelial barrier function and reduce edema formation caused by oxidant injury.

Eugenol causes oxidant-mediated edema in isolated perfused rabbit lungs

Eugenol, an extract of cloves, has been associated with pulmonary edema when inhaled from commercially available clove cigarettes. We tested the hypothesis that eugenol directly causes lung edema through oxidant-mediated mechanisms by infusing eugenol (0.1 and 1.0 mM) into isolated rabbit lungs perfused with a cell-free albumin and physiologic salt solution. We observed lung edema (1.0 mM) as demonstrated by increased lung weight gain and wet-to-dry lung weight ratios without alterations in mean pulmonary artery pressure. The oxygen metabolite scavengers catalase (1,000 U/ml) and dimethylthiourea (30 mM) attenuated lung edema. Instillation of dimethylurea, superoxide dismutase, or heat-inactivated catalase did not prevent lung edema formation. We conclude that eugenol causes lung edema in isolated lungs through oxidant-mediated mechanisms in the absence of circulating formed blood elements. Eugenol may be a valuable compound in the laboratory investigation of edemogenic disorders.