Prone position ventilation, recruitment maneuver and intravenous zanamivir in severe refractory hypoxemia caused by influenza A (H1N1)

Update on viral community-acquired pneumonia

A pneumonia de origem viral é uma causa prevalente de infecção respiratória em adultos imunocompetentes. Tem apresentação variada, ocasionando desde formas leves a quadros graves de insuficiência respiratória com necessidade de ventilação mecânica. Contudo, em nosso país, há poucos estudos a respeito da apresentação clínica e diagnóstico dessa infecção. Dessa forma, os autores do presente artigo têm por objetivo revisar os principais agentes virais causadores de pneumonia na comunidade e discutir as modalidades diagnósticas e terapêuticas disponíveis atualmente.

Update on viral community-acquired pneumonia

Viral pneumonia is a prevalent cause of respiratory infection in immunocompetent adults. It has varied presentation, from mild to severe respiratory failure, requiring mechanical ventilation. However, in Brazil, there have been few studies on the clinical presentation and diagnosis of this infection. Thus, the authors of the present article intend to review the main viral agents that cause community-acquired pneumonia and to discuss the currently available diagnostic and therapeutic methods.

[Recommendations of the Infectious Diseases Work Group (GTEI) of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC) and the Infections in Critically Ill Patients Study Group (GEIPC) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) for the diagnosis and treatment of influenza A/H1N1 in seriously ill adults admitted to the Intensive Care Unit]

The diagnosis of influenza A/H1N1 is mainly clinical, particularly during peak or seasonal flu outbreaks. A diagnostic test should be performed in all patients with fever and flu symptoms that require hospitalization. The respiratory sample (nasal or pharyngeal exudate or deeper sample in intubated patients) should be obtained as soon as possible, with the immediate start of empirical antiviral treatment. Molecular methods based on nucleic acid amplification techniques (RT-PCR) are the gold standard for the diagnosis of influenza A/H1N1. Immunochromatographic methods have low sensitivity; a negative result therefore does not rule out active infection. Classical culture is slow and has low sensitivity. Direct immunofluorescence offers a sensitivity of 90%, but requires a sample of high quality. Indirect methods for detecting antibodies are only of epidemiological interest. Patients with A/H1N1 flu may have relative leukopenia and elevated serum levels of LDH, CPK and CRP, but none of these variables are independently associated to the prognosis. However, plasma LDH> 1500 IU/L, and the presence of thrombocytopenia <150 x 10(9)/L, could define a patient population at risk of suffering serious complications. Antiviral administration (oseltamivir) should start early (<48 h from the onset of symptoms), with a dose of 75 mg every 12h, and with a duration of at least 7 days or until clinical improvement is observed. Early antiviral administration is associated to improved survival in critically ill patients. New antiviral drugs, especially those formulated for intravenous administration, may be the best choice in future epidemics. Patients with a high suspicion of influenza A/H1N1 infection must continue with antiviral treatment, regardless of the negative results of initial tests, unless an alternative diagnosis can be established or clinical criteria suggest a low probability of influenza. In patients with influenza A/H1N1 pneumonia, empirical antibiotic therapy should be provided due to the possibility of bacterial coinfection. A beta-lactam plus a macrolide should be administered as soon as possible. The microbiological findings and clinical or laboratory test variables may decide withdrawal or not of antibiotic treatment. Pneumococcal vaccination is recommended as a preventive measure in the population at risk of suffering severe complications. Although the use of moderate- or low-dose corticosteroids has been proposed for the treatment of influenza A/H1N1 pneumonia, the existing scientific evidence is not sufficient to recommend the use of corticosteroids in these patients. The treatment of acute respiratory distress syndrome in patients with influenza A/H1N1 must be based on the use of a protective ventilatory strategy (tidal volume <10 ml / kg and plateau pressure <35 mmHg) and positive end-expiratory pressure set to high patient lung mechanics, combined with the use of prone ventilation, muscle relaxation and recruitment maneuvers. Noninvasive mechanical ventilation cannot be considered a technique of choice in patients with acute respiratory distress syndrome, though it may be useful in experienced centers and in cases of respiratory failure associated with chronic obstructive pulmonary disease exacerbation or heart failure. Extracorporeal membrane oxygenation is a rescue technique in refractory acute respiratory distress syndrome due to influenza A/H1N1 infection. The scientific evidence is weak, however, and extracorporeal membrane oxygenation is not the technique of choice. Extracorporeal membrane oxygenation will be advisable if all other options have failed to improve oxygenation. The centralization of extracorporeal membrane oxygenation in referral hospitals is recommended. Clinical findings show 50-60% survival rates in patients treated with this technique. Cardiovascular complications of influenza A/H1N1 are common. Such problems may appear due to the deterioration of pre-existing cardiomyopathy, myocarditis, ischemic heart disease and right ventricular dysfunction. Early diagnosis and adequate monitoring allow the start of effective treatment, and in severe cases help decide the use of circulatory support systems. Influenza vaccination is recommended for all patients at risk. This indication in turn could be extended to all subjects over 6 months of age, unless contraindicated. Children should receive two doses (one per month). Immunocompromised patients and the population at risk should receive one dose and another dose annually. The frequency of adverse effects of the vaccine against A/H1N1 flu is similar to that of seasonal flu. Chemoprophylaxis must always be considered a supplement to vaccination, and is indicated in people at high risk of complications, as well in healthcare personnel who have been exposed.

Follow-up after acute respiratory distress syndrome caused by influenza a (H1N1) virus infection

BACKGROUND

There are no reports on the long-term follow-up of patients with swine-origin influenza A virus infection that progressed to acute respiratory distress syndrome.

METHODS

Four patients were prospectively followed up with pulmonary function tests and high-resolution computed tomography for six months after admission to an intensive care unit.

RESULTS

Pulmonary function test results assessed two months after admission to the intensive care unit showed reduced forced vital capacity in all patients and low diffusion capacity for carbon monoxide in two patients. At six months, pulmonary function test results were available for three patients. Two patients continued to have a restrictive pattern, and none of the patients presented with abnormal diffusion capacity for carbon monoxide. All of them had a diffuse ground-glass pattern on high-resolution computed tomography that improved after six months.

CONCLUSIONS

Despite the marked severity of lung disease at admission, patients with acute respiratory distress syndrome caused by swine-origin influenza A virus infection presented a late but substantial recovery over six months of follow-up.

Shortening ventilatory support with a protocol based on daily extubation screening and noninvasive ventilation in selected patients

BACKGROUND

Prolonged invasive mechanical ventilation and reintubation are associated with adverse outcomes and increased mortality. Daily screening to identify patients able to breathe without support is recommended to reduce the length of mechanical ventilation. Noninvasive positive-pressure ventilation has been proposed as a technique to shorten the time that patients remain on invasive ventilation.

METHODS

We conducted a before-and-after study to evaluate the efficacy of an intervention that combined daily screening with the use of noninvasive ventilation immediately after extubation in selected patients. The population consisted of patients who had been intubated for at least 2 days.

RESULTS

The baseline characteristics were similar between the groups. The intervention group had a lower length of invasive ventilation (6 [4;9] vs. 7 [4;11.5] days, p = 0.04) and total (invasive plus noninvasive) ventilator support (7 [4;11] vs. 9 [6;8], p = 0.01). Similar reintubation rates within 72 hours were observed for both groups. In addition, a lower ICU mortality was found in the intervention group (10.8% vs. 24.3%, p = 0.03), with a higher cumulative survival probability at 60 days (p = 0.05). Multivariate analysis showed that the intervention was an independent factor associated with survival (RR: 2.77; CI 1.14-6.65; p = 0.03), whereas the opposite was found for reintubation at 72 hours (RR: 0.27; CI 0.11-0.65; p = 0.01).

CONCLUSION

The intervention reduced the length of invasive ventilation and total ventilatory support without increasing the risk of reintubation and was identified as an independent factor associated with survival.