Outcomes of Treatment in Severely Ill Patients
Australia and New Zealand Extracorporeal Membrane Oxygenation for 2009 Influenza A (H1N1) Acute Respiratory Distress Syndrome
(Australia and New Zealand Extracorporeal Membrane Oxygenation (ANZ ECMO) Influenza Investigators. Extracorporeal membrane oxygenation for 2009 influenza A (H1N1) acute respiratory distress syndrome. JAMA. 2009 Oct 12. [Epub ahead of print])
The investigators review their experience in 15 ICUs in Australia and New Zealand with 68 patients with 2009 influenza A (H1N1) infection who developed acute respiratory distress syndrome (ARDS) and required ECMO:
Patients: mean age, 34 years; children (3 children younger than 15 years of age)
Predisposing conditions: BMI > 30 (34 patients), asthma (19), diabetes (10), pregnancy or postpartum (10)
Bacterial superinfection was found in 19 patients (28%), including S pneumoniae in 10 and S aureus in 4
Severity of illness: median values for lowest PaO2: 56; highest positive end expiratory pressure (PEEP): 18 cm H2O; lowest pH: 7.2; highest FiO2: 1.0; median acute lung injury score: 3.8; highest pCO2: 69 mm Hg; highest peak airway pressure: 36 cm H2O
Course: infectious complications in 42 (62%) included respiratory tract: 42; bacteremia: 14; ECMO cannulae: 7; and non-ECMO-related: 13
Median duration of care modalities: mechanical ventilation: 25 days; hospitalization: 37 days; ICU stay: 27 days; ECMO: 10 days
Outcome: survival and ICU discharge: 48 (71%); survival and hospital discharge: 32 (47%); still in hospital: 16 (24%); died: 14 (21%) [cause of death: respiratory failure: 4; intracranial hemorrhage: 6; hemorrhage: 4; infection: 1 (some had multiple infections)]
All of the patients satisfied the CESAR criteria for ECMO (see below);
The 21% end-of-study mortality rate in this study is low compared with previous reports; the authors attribute this to the relatively young age of patients and several training and technical attributes of their consortium of ECMO sites;
On the basis of their experience, the investigators project that the ECMO needs for the United States and Europe for the 2009-2010 influenza season will be 800-1300 patients.
Rate of ECMO use for H1N1 influenza was 2.6 cases/million population in 2009 vs 0.15 cases/million for seasonal influenza in 2008.
CESAR Trial Comparing ECMO and Conventional Ventilation
A study was designed to determine the safety, efficacy, and cost-effectiveness of ECMO compared with conventional ventilation in the treatment of adults with severe acute respiratory failure. There were 120 adults with potentially reversible respiratory failure and Murray score > 3.0 or pH < 7.2. The 6-month survival was 57/90 (63%) for patients allocated to consideration of treatment by ECMO vs 41/87 (47%) for patients allocated to conventional treatment (P = .03). (Peek GJ, Mugford M, Tiruvoipati R, et al. Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial. Lancet. 2009;Sep 15 [Epub ahead of print].)
Critically Ill Patients in Canada
Kumar and colleagues present a prospective observational study of 168 patients critically ill with 2009 influenza A (H1N1) cared for in 38 adult and pediatric ICUs in Canada during April 16-August 12, 2009. All patients were evaluated by a standardized protocol.
Demographics. Mean patient age was 32 years, with 50 (30%) under 18 years of age. There were 16 nosocomial cases. Chronic preexisting conditions of the sample included:
Chronic lung disease: 69 (41%), including asthma (38 [23%]) and COPD (16 [10%]);
Obesity: 56 (33%); morbid obesity with BMI > 40: 28 (24%);
Immune suppression: 33 (20%), including chronic steroids (26 [16%]) and HIV (2 [1%]);
Neurologic disease: 26 (16%);
Cardiac disease: 25 (15%);
Pregnancy: 13 (8%);
Malignancy: 6 (4%); and
Chronic renal disease: 12 (7%).
Suspected bacterial infection: 32%;
Renal failure: 7%;
Median duration of symptoms prior to hospitalization: 4 days;
Median duration of hospitalization prior to ICU: 1 day.
Physical exam and laboratory data (day 1 of hospitalization):
Chest x-ray (bilateral infiltrates: 71%; 4-quadrant involvement: 41%; lung injury "at onset": 73%);
Vital signs (mean pulse: 119; lowest mean systolic BP: 95 mmHg; mean SOFA score: 6.8);
Lab results (mean WBC: 9400/mL; median CPK: 243).
Mechanical ventilation:136 (81%) on day 1;
Treatment for O2 failure included neuromuscular blockade in 47 (28%), inhaled nitric oxide in 23 (14%), high-frequency oscillatory ventilation in 20 (12%), ECMO in 7 (4%), and prone-position ventilation in 5 (3%);
Drugs: vasopressors or inotropes: 55 (33%); antivirals:152 (91%); antibacterials: 166 (99%); corticosteroids: 85 (51%).
(Kumar A, Zarychanski R, Pinto R, et al. Critically ill patients with 2009 influenza A(H1N1) infection in Canada. JAMA. 2009 Oct 12. [Epub ahead of print])
Medscape Infectious Diseases © 2009
Cite this: John G. Bartlett. 2009 H1N1 Influenza -- Just the Facts: Clinical Features and Epidemiology - Medscape - Sep 25, 2009.