|Description of the Critically Ill
H1N1 patient with acute pneumonitis
Stephen E. Lapinsky, Toronto
- July 3, 2009
This description is based on limited data,
largely derived from clinical experience, published data, unpublished data
from review of Mexican cases, and descriptions from WHO teleconference
calls. Although several patient groups have been described (eg. COPD/asthma
exacerbation, mild respiratory illness), this report describes the patient
with acute pneumonitis.
- Patients may include younger, previously well adults, as well as the
immunocompromised patient and pregnant women.
- Obesity appears to be a risk factor for respiratory failure
- Relatively rapid onset of disease, with a short duration from
hospital admission to respiratory failure. This may depend on delay in
presenting to hospital.
- Negative initial nasopharyngeal swabs have been reported, with
diagnosis subsequently made on viral analysis of sputum, ET aspirate, or
- Chest X-ray demonstrates bilateral patchy airspace disease, with
- Autopsy reports have described diffuse alveolar damage, pulmonary
hemorrhage as well as multiple pulmonary emboli
- Patients have been very difficult to ventilate, with marked
hypoxemia. Alternative forms of ventilation are often required,
including APRV, HFO and iNO administration. ECMO has been used
- One group has reported patients to have little response of hypoxemia
to PEEP, with a response to aggressive diuresis.
- Septic shock is uncommon, although many patients have required
inotropic support and renal failure may occur.
- Improvement in pulmonary function has been slow, with many patients
requiring ventilatory support for 3 weeks or more.
- Persistent viral excretion may occur despite treatment with
antiviral agents, requiring prolonged therapy.
- Antiviral treatment has included oseltamivir PO and zanamavir by
inhalation and IV.
- Secondary bacterial infection has not been common
- No significant reports of the use/effect of steroids.
- Death has occurred predominantly due to respiratory failure with
progressive hypoxemia, unlike conventional ARDS.
- Mortality of patients requiring mechanical ventilation is in the
range of 30 - 40%.