A scoring system composed of clinical, radiological, and laboratory variables purports to distinguish H1N1 influenza virus infection from community acquired pneumonia1. An accompanying editorial2 suggests that while further validation is required, the most useful application of the score might be in those with a score of 0 or 1 (out of 5), in whom the the high negative predictive value might safely avoid inpatient isolation and neuraminidase inhibitor treatment in the under-65s.
Background Early identification of patients with H1N1 influenza-related pneumonia is desirable for the early instigation of antiviral agents. A study was undertaken to investigate whether adults admitted to hospital with H1N1 influenza-related pneumonia could be distinguished clinically from patients with non-H1N1 community-acquired pneumonia (CAP).
Methods Between May 2009 and January 2010, clinical and epidemiological data of patients with confirmed H1N1 influenza infection admitted to 75 hospitals in the UK were collected by the Influenza Clinical Information Network (FLU-CIN). Adults with H1N1 influenza-related pneumonia were identified and compared with a prospective study cohort of adults with CAP hospitalised between September 2008 and June 2010, excluding those admitted during the period of the pandemic.
Results Of 1046 adults with confirmed H1N1 influenza infection in the FLU-CIN cohort, 254 (25%) had H1N1 influenza-related pneumonia on admission to hospital. In-hospital mortality of these patients was 11.4% compared with 14.0% in patients with inter-pandemic CAP (n=648). A multivariate logistic regression model was generated by assigning one point for each of five clinical criteria: age ≤65 years, mental orientation, temperature ≥38°C, leucocyte count ≤12×10(9)/l and bilateral radiographic consolidation. A score of 4 or 5 predicted H1N1 influenza-related pneumonia with a positive likelihood ratio of 9.0. A score of 0 or 1 had a positive likelihood ratio of 75.7 for excluding it.
Conclusion There are substantial clinical differences between H1N1 influenza-related pneumonia and inter-pandemic CAP. A model based on five simple clinical criteria enables the early identification of adults admitted with H1N1 influenza-related pneumonia.
1. Clinical and laboratory features distinguishing pandemic H1N1 influenza-related pneumonia from interpandemic community-acquired pneumonia in adults
Thorax. 2011 March; 66(3): 247–252 Free Full Text
2. Predicting the unpredictable: is it possible clinically to separate H1N1 from non-H1N1 community-acquired pneumonia?
Thorax. 2011 Mar;66(3):187-8
H1N1 Update 16 December 2010 sent from the UK Intensive Care Society
As many of you will already be aware, the predicted second wave of swine flu seems to becoming a reality. The HPA have received information that there has been a rise in the number of confirmed H1N1 cases and has restarted regular teleconferences to discuss the current situation and to disseminate the latest advice and information. The initial teleconference was held last Friday and the first question asked was how many cases have units seen. Although the total numbers were not high, the fact that there are confirmed cases throughout the UK gave support to the decision that hospitals should prepare for an increase in the numbers.
Subsequent updates have confirmed that the case numbers are rising and although not all patients admitted to ICUs with a suspected diagnosis of H1N1 have required mechanical ventilation or had H1N1 confirmed. As of Wednesday this week the numbers of H1N1 related ICU cases had risen to 140. An additional concern is that the number of cases with probable H1N1 referred for ECMO is now 13 and this has resulted in a policy that there should be support for all the centers in the UK who can provide ECMO.
It is still too early to predict what the level escalation is going to be required, but there are real concerns that the combination of adverse weather conditions, the current financial restrictions in the NHS, and an H1N1 peak could place ICUs in a more seriously challenging situation than occurred in the previous outbreak.
For this reason, it is recommended that clinicians should once again have a low threshold for considering the possibility of H1N1 in patients who are referred to intensive care. Trusts should reconvene regular meetings to plan for any necessary expansion of critical care services. It is important that staff have up to date training in the use of personal protection equipment. One of the most important points learned from the first outbreak was that early antiviral therapy can reduce the need for mechanical ventilation and it is recommended that any patients admitted to hospital with a history and symptoms suggestive of an influenza-like illness should be given antiviral therapy.
The following points were made in the HPA–led teleconference on 10 December:
- be vigilant: have a low threshold for considering the diagnosis.
- start antivirals whenever there is a suspicion of flu (oseltamivir 75or 150 mg bd po).
- In patients with resistance or not tolerating NG medication, there is an IV preparation which is currently undergoing clinical trial. GSK produces it (zanamavir) and may provide it on patient-name compassionate grounds.
- Use ARDSnet ventilation especially for those with normal lung compliance.
- Consider HFO for those with poor compliance
- Fluid restrict patients
- Consider referral for ECMO early if conventional ventilation is failing. ECMO beds are occupied almost all occupied by ‘flu patients and elective surgery has been curtailed to accomodate them. Surge funding has been agreed for extra ECMO. In cases where conventional ventilation is failing and there are no other options, patients should be referred to Glenfield before seven days of MV.
- HPA adviced has not changed with respect to infection control measures; these can be found here:http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/@ps/documents/digitalasset/dh_110899.pdf
- The RCoA site still has an adult practice note from last year which will be updated
- The HPA link to seasonal flu can be found here:http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/SeasonalInfluenza/Guidelines/
- There will be advice re pregnant women after discussion with the RCOG
- In some cases, URT specimens may be negative in severe cases and LRT samples may be needed for the diagnosis.
- Point of care testing may have inadequate sensitivity for this strain of H1N1
The current rate is 21.5/100,000.
We aim to provide updates on the ICS website and copy of this document is available to download via http://www.ics.ac.uk/ under ‘Latest News – H1N1 Latest News’.
Update by the Executive Committee of the Intensive Care Society.
Sent from the email of:
Head of Secretariat
A case report describes the improvement of a critically ill patient with H1N1 ‘flu after the administration of N-acetylcysteine in a dose similar to that used to treat paracetamol (acetaminophen) overdose.
Influenza virus induces reactive oxygen species that activate nuclear factor kappa B to produce cytokines. High-dose N-acetylcysteine, an antioxidant, is thought to reduce the production of this cytokine storm which contributes to the lethality of influenza. More studies are clearly needed.
High-Dose N-Acetylcysteine Therapy for Novel H1N1 Influenza Pneumonia
Ann Intern Med. 2010 May 18;152(10):687-8
The World Health Organisation has published updated guidelines on drug treatment of Influenza A(H1N1)2009 and other influenza viruses. Their recommendations are summarised in this table:
Full text of the guidelines is available here
WHO Guidelines for Pharmacological Management of Pandemic Influenza A(H1N1) 2009 and other Influenza Viruses
Guidance on infection control measures is available from the CDC website
A Canadian study in which 446 nurses were randomised to wear one or the other showed a standard surgical mask to be non-inferior to a N95 mask in preventing flu infection in the health workers.
Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers
JAMA. 2009 Nov 4;302(17):1865-71