Lung Function and Organ Dysfunctions in 178 Patients Requiring Mechanical Ventilation During The 2009 Influenza A (H1N1) Pandemic

Abstract

IntroductionMost cases of the 2009 influenza A (H1N1) infection are self-limited, but occasionally the disease evolves to a severe condition needing hospitalization. Here we describe the evolution of the respiratory compromise, ventilatory management and laboratory variables of patients with diffuse viral pneumonitis caused by pandemic 2009 influenza A (H1N1) admitted to the ICU.MethodThis was a multicenter, prospective inception cohort study including adult patients with acute respiratory failure requiring mechanical ventilation (MV) admitted to 20 ICUs in Argentina between June and September of 2009 during the influenza A (H1N1) pandemic. In a standard case-report form, we collected epidemiological characteristics, results of real-time reverse-transcriptase--polymerase-chain-reaction viral diagnostic tests, oxygenation variables, acid-base status, respiratory mechanics, ventilation management and laboratory tests. Variables were recorded on ICU admission and at days 3, 7 and 10.ResultsDuring the study period 178 patients with diffuse viral pneumonitis requiring MV were admitted. They were 44 ± 15 years of age, with Acute Physiology And Chronic Health Evaluation II (APACHE II) scores of 18 ± 7, and most frequent comorbidities were obesity (26%), previous respiratory disease (24%) and immunosuppression (16%). Non-invasive ventilation (NIV) was applied in 49 (28%) patients on admission, but 94% were later intubated.Acute respiratory distress syndrome (ARDS) was present throughout the entire ICU stay in the whole group (mean PaO2/FIO2 170 ± 25). Tidal-volumes used were 7.8 to 8.1 ml/kg (ideal body weight), plateau pressures always remained < 30 cmH2O, without differences between survivors and non-survivors; and mean positive end-expiratory pressure (PEEP) levels used were between 8 to 12 cm H2O. Rescue therapies, like recruitment maneuvers (8 to 35%), prone positioning (12 to 24%) and tracheal gas insufflation (3%) were frequently applied. At all time points, pH, platelet count, lactate dehydrogenase assay (LDH) and Sequential Organ Failure Assessment (SOFA) differed significantly between survivors and non-survivors. Lack of recovery of platelet count and persistence of leukocytosis were characteristic of non-survivors. Mortality was high (46%); and length of MV was 10 (6 to 17) days.ConclusionsThese patients had severe, hypoxemic respiratory failure compatible with ARDS that persisted over time, frequently requiring rescue therapies to support oxygenation. NIV use is not warranted, given its high failure rate. Death and evolution to prolonged mechanical ventilation were common outcomes. Persistence of thrombocytopenia, acidosis and leukocytosis, and high LDH levels found in non-survivors during the course of the disease might be novel prognostic findings.

Pulmonary function in patients with pandemic H1N1

“…Another relevant data refers to the body mass index (BMI), which can be a risk factor for the development of various diseases, and also a signi icant factor to the worsening of the patient with the In luenza A virus (H1NI) (8). In the present research the data points to a high percentage, 81.81%, of patients with a BMI of ≥25kg/m².…”

“…In the more serious cases, survivors presented great bilateral pulmonary damage in 2 or more quadrants and signs of aveolar in iltrates with a substantial systemic in lammatory response, evidenced by radiography. These alterations had a great impact on oxygenation and induced severe pulmonary lesion (2,6,7,8).…”

Noninvasive mechanical ventilation in high-risk pulmonary infections: a clinical review

“…A summary of published studies on NIV in pH1N1 is shown in table 2 [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][36][37][38][39][40][41][42][43][44][45][46][47][48]. Of the 22 studies included in table 2, the majority were case series reports.…”

“…These included obesity, COPD, diabetes mellitus, asthma, immunosuppression, chronic kidney disease and heart failure [27][28][29][30]32]. The overall ICU mortality rate for critically ill cases of pH1N1 was close to 17% [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…The use of NIV as initial ventilator support for respiratory failure in the presence of SARS appears to be a reasonable option, albeit under strict infection control measures. [18][19][20][21][22][23][24][25][26][27][28][29][30]. The pH1N1 virus originated from the swine influenza (H1N1) virus circulating in North American pigs [23].…”