2009 H1N1 Influenza -- Just the Facts: Clinical Features and Epidemiology

John G. Bartlett, MD

Disclosures

November 23, 2009

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)]

Comments:

  • 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%).

Symptoms

  • Fever: 91%;

  • Myalgias: 56%;

  • Suspected bacterial infection: 32%;

  • Hypotension: 14%;

  • Altered consciousness:10%;

  • 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).

Treatment

  • 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])

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.

processing....