Tag Archives: respiratory

Acute Med, All Updates, ICU, Resus

β-2 agonists could worsen ARDS outcome

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Image: Wikipedia. I really fancy a curry now.

A previous study (BALTI-1) suggested β-2 agonists may help in ARDS by reducing extravascular lung water. A randomised trial in the UK aimed to recruit 1334 patients to compare intravenous salbutamol infused for seven days with placebo (0.9% saline). However the Data Monitoring and Ethics Committee recommended that the study stop after the second interim analysis of 273 patients because of a significant increase in mortality. It is unclear why salbutamol is harmful, and could be due to lung, cardiovascular, or other metabolic effects, such as activation of the renin-angiotensin aldosterone system affecting fluid balance.


BACKGROUND:In a previous randomised controlled phase 2 trial, intravenous infusion of salbutamol for up to 7 days in patients with acute respiratory distress syndrome (ARDS) reduced extravascular lung water and plateau airway pressure. We assessed the effects of this intervention on mortality in patients with ARDS.

METHODS:We did a multicentre, placebo-controlled, parallel-group, randomised trial at 46 UK intensive-care units between December, 2006, and March, 2010. Intubated and mechanically ventilated patients (aged ≥16 years) within 72 h of ARDS onset were randomly assigned to receive either salbutamol (15 μg/kg ideal bodyweight per h) or placebo for up to 7 days. Randomisation was done by a central telephone or web-based randomisation service with minimisation by centre, pressure of arterial oxygen to fractional inspired oxygen concentration (PaO2/FiO2) ratio, and age. All participants, caregivers, and investigators were masked to group allocation. The primary outcome was death within 28 days of randomisation. Analysis was by intention-to-treat. This trial is registered, ISRCTN38366450 and EudraCT number 2006-002647-86.

FINDINGS:We randomly assigned 162 patients to the salbutamol group and 164 to the placebo group. One patient in each group withdrew consent. Recruitment was stopped after the second interim analysis because of safety concerns. Salbutamol increased 28-day mortality (55 [34%] of 161 patients died in the salbutamol group vs 38 (23%) of 163 in the placebo group; risk ratio [RR] 1·47, 95% CI 1·03-2·08).

INTERPRETATION:Treatment with intravenous salbutamol early in the course of ARDS was poorly tolerated. Treatment is unlikely to be beneficial, and could worsen outcomes. Routine use of β-2 agonist treatment in ventilated patients with this disorder cannot be recommended.

FUNDING:UK Medical Research Council, UK Department of Health, UK Intensive Care Foundation.

Effect of intravenous β-2 agonist treatment on clinical outcomes in acute respiratory distress syndrome (BALTI-2): a multicentre, randomised controlled trial
Lancet 379(9812, 21–27 January 2012, Pages 229–235

Acute Med, All Updates, ICU, Resus, Ultrasound

Ultrasound for pneumonia

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Lung ultrasound done by a single keen individual had better test characteristics than CXR in diagnosing pneumonia as defined by discharge diagnosis.
The lung ultrasound was considered to be positive for pneumonia if it showed consolidation (including air bronchograms) or a focal interstitial syndrome (localised increased density of ‘B’ lines)


Objective The aim of this study was to evaluate the diagnostic accuracy of bedside lung ultrasound and chest radiography (CXR) in patients with suspected pneumonia compared with CT scan and final diagnosis at discharge.

Design A prospective clinical study.

Methods Lung ultrasound and CXR were performed in sequence in adult patients admitted to the emergency department (ED) for suspected pneumonia. A chest CT scan was performed during hospital stay when clinically indicated.

Results 120 patients entered the study. A discharge diagnosis of pneumonia was confirmed in 81 (67.5%). The first CXR was positive in 54/81 patients (sensitivity 67%; 95% CI 56.4% to 76.9%) and negative in 33/39 (specificity 85%; 95% CI 73.3% to 95.9%), whereas lung ultrasound was positive in 80/81 (sensitivity 98%; 95% CI 93.3% to 99.9%) and negative in 37/39 (specificity 95%; 95% CI 82.7% to 99.4%). A CT scan was performed in 30 patients (26 of which were positive for pneumonia); in this subgroup the first CXR was diagnostic for pneumonia in 18/26 cases (sensitivity 69%), whereas ultrasound was positive in 25/26 (sensitivity 96%). The feasibility of ultrasound was 100% and the examination was always performed in less than 5 min.

Conclusions Bedside chest ultrasound is a reliable tool for the diagnosis of pneumonia in the ED, probably being superior to CXR in this setting. It is likely that its wider use will allow a faster diagnosis, conducive to a more appropriate and timely therapy.

Lung ultrasound is an accurate diagnostic tool for the diagnosis of pneumonia in the emergency department
Emerg Med J. 2012 Jan;29(1):19-23

Acute Med, All Updates, ICU, Kids, PHARM, Resus

2011 Asthma Guidelines

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The British Thoracic Society / SIGN Guidelines on asthma have been updated for 2011. There don’t seem to be any modificiations to the sections on acute severe asthma which were updated in 2009 and blogged here, although the treatment algorithms seem to be presented in a slightly different format and therefore are reproduced here:

Management of acute severe asthma in adults in hospital

Management of acute asthma in children in hospital

Acute Med, All Updates, ICU, Kids, PHARM, Resus

Oxygen therapy for asthma can elevate CO2

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Patients with acute exacerbations of asthma randomised to receive high concentration oxygen therapy showed a greater rise in CO2 than those who received titrated oxygen to keep SpO2 > 93%.
This study has a few weaknesses but raises an interesting challenge to the dogma of high flow oxygen (and oxygen driven nebulisers) for all acute asthma exacerbations.
The suggested main mechanism for the elevation in CO2 is worsening ventilation/perfusion mismatching as a result of the release of hypoxic pulmonary vasoconstriction and a consequent increase in physiological dead space. The authors remind us that this has been demonstrated in other studies on asthma and acute COPD exacerbations. The authors infer that high concentration oxygen therapy may therefore potentially increase the PaCO2 across a range of respiratory conditions with abnormal gas exchange due to ventilation/perfusion mismatching
Some of the weaknesses include lack of blinding, recruiting fewer patients than planned, and changing their primary outcome variable after commencing the study (which the authors are honest about) from absolute CO2 to increase in CO2 (since it was apparent on preliminary analysis of the first few patients that presenting CO2 was the primary determinant of subsequent CO2). Furthermore, the CO2 was measured from a transcutaneous device as opposed to the true ‘gold standard’ of arterial blood gas analysis, although good reasons are given for this.
Despite some of these drawbacks this study provides us with a further reminder that oxygen is a drug with some unwanted effects and therefore its dose needs to be individualised for the patient.


Background The effect on Paco(2) of high concentration oxygen therapy when administered to patients with severe exacerbations of asthma is uncertain.

Methods 106 patients with severe exacerbations of asthma presenting to the Emergency Department were randomised to high concentration oxygen (8 l/min via medium concentration mask) or titrated oxygen (to achieve oxygen saturations between 93% and 95%) for 60 min. Patients with chronic obstructive pulmonary disease or disorders associated with hypercapnic respiratory failure were excluded. The transcutaneous partial pressure of carbon dioxide (Ptco(2)) was measured at 0, 20, 40 and 60 min. The primary outcome variable was the proportion of patients with a rise in Ptco(2) ≥4 mm Hg at 60 min.

Results The proportion of patients with a rise in Ptco(2) ≥4 mm Hg at 60 min was significantly higher in the high concentration oxygen group, 22/50 (44%) vs 10/53 (19%), RR 2.3 (95% CI 1.2 to 4.4, p<0.006). The high concentration group had a higher proportion of patients with a rise in Ptco(2) ≥8 mm Hg, 11/50 (22%) vs 3/53 (6%), RR 3.9 (95% CI 1.2 to 13.1, p=0.016). All 10 patients with a final Ptco(2) ≥45 mm Hg received high concentration oxygen therapy, and in five there was an increase in Ptco(2) ≥10 mm Hg.
Conclusion High concentration oxygen therapy causes a clinically significant increase in Ptco(2) in patients presenting with severe exacerbations of asthma. A titrated oxygen regime is recommended in the treatment of severe asthma, in which oxygen is administered only to patients with hypoxaemia, in a dose that relieves hypoxaemia without causing hyperoxaemia.

Randomised controlled trial of high concentration versus titrated oxygen therapy in severe exacerbations of asthma
Thorax. 2011 Nov;66(11):937-41

Acute Med, All Updates, PHARM, Resus

Pre-hospital CPAP for pulmonary oedema

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The physician-staffed mobile intensive care units of SAMU (Service d’Aide Médicale Urgente) in France provided the location for this randomised controlled trial of CPAP for acute cardiogenic pulmonary oedema.


STUDY OBJECTIVE: The purpose of this randomized controlled trial was to determine the immediate and delayed effects of noninvasive ventilation for patients in acute cardiogenic pulmonary edema (ACPE) in addition to aggressive usual care in a medical prehospital setting.

METHODS: Out-of-hospital patients in severe ACPE were eligible for the study. Patients were randomized to receive either usual care, including conventional optimal treatment with furosemide, oxygen, and high-dose boluses of isosorbide dinitrate plus oxygen, or conventional medications plus out-of-hospital continuous positive airway pressure (CPAP). The primary outcome was the treatment success defined as all of respiratory rate less than 25 breaths per minute and oxygen saturation of greater than 90% at the end of 1-hour study. Secondary end points included death during 30 days after inclusion. Lengths of intensive care unit and hospital stays were also recorded.

RESULTS: In total, 124 patients were enrolled into the study. The 2 groups had similar baseline characteristics. For the primary outcome analysis, 22 (35.5%) of 62 patients were considered as experiencing a treatment success in the usual care group vs 19 (31.7%) of 60 in the CPAP group (P = .65). Seven patients died within 30 days in the usual care group vs 6 in the CPAP group (P = .52). There were no statistically significant differences between the treatment groups for length of stay either in hospital or in the intensive care unit.

CONCLUSION: In the prehospital setting, in spite of its potential advantages for patients in ACPE, CPAP may not be preferred to a strict optimal intravenous treatment.

Continuous positive airway pressure for cardiogenic pulmonary edema: a randomized study
Am J Emerg Med. 2011 Sep;29(7):775-81

Acute Med, All Updates, ICU, Resus

Dexamethasone for community acquired pneumonia

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Another Dutch study has examined steroids for community acquired pneumonia, this time with the primary outcome measure being hospital length of stay, which was reduced by one day on the steroid group. Compare this study with a previous negative study of prednisolone for pneumonia.

BACKGROUND: Whether addition of corticosteroids to antibiotic treatment benefits patients with community-acquired pneumonia who are not in intensive care units is unclear. We aimed to assess effect of addition of dexamethasone on length of stay in this group, which might result in earlier resolution of pneumonia through dampening of systemic inflammation.

METHODS: In our double-blind, placebo-controlled trial, we randomly assigned adults aged 18 years or older with confirmed community-acquired pneumonia who presented to emergency departments of two teaching hospitals in the Netherlands to receive intravenous dexamethasone (5 mg once a day) or placebo for 4 days from admission. Patients were ineligible if they were immunocompromised, needed immediate transfer to an intensive-care unit, or were already receiving corticosteroids or immunosuppressive drugs. We randomly allocated patients on a one-to-one basis to treatment groups with a computerised randomisation allocation sequence in blocks of 20. The primary outcome was length of hospital stay in all enrolled patients. This study is registered with ClinicalTrials.gov, number NCT00471640.

FINDINGS: Between November, 2007, and September, 2010, we enrolled 304 patients and randomly allocated 153 to the placebo group and 151 to the dexamethasone group. 143 (47%) of 304 enrolled patients had pneumonia of pneumonia severity index class 4-5 (79 [52%] patients in the dexamethasone group and 64 [42%] controls). Median length of stay was 6·5 days (IQR 5·0-9·0) in the dexamethasone group compared with 7·5 days (5·3-11·5) in the placebo group (95% CI of difference in medians 0-2 days; p=0·0480). In-hospital mortality and severe adverse events were infrequent and rates did not differ between groups, although 67 (44%) of 151 patients in the dexamethasone group had hyperglycaemia compared with 35 (23%) of 153 controls (p<0·0001).

INTERPRETATION: Dexamethasone can reduce length of hospital stay when added to antibiotic treatment in non-immunocompromised patients with community-acquired pneumonia.

Dexamethasone and length of hospital stay in patients with community-acquired pneumonia: a randomised, double-blind, placebo-controlled trial
Lancet. 2011 Jun 11;377(9782):2023-30

Acute Med, All Updates, ICU, Resus, Ultrasound

Thrombolysis in submassive PE – still equipoise?

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The AHA has produced a comprehensive guideline on venous thromboembolic disease. Here are some excerpts pertaining to resuscitation room decision making, particularly: ‘should I thrombolyse this patient?’

Definition for massive PE: Acute PE with sustained hypotension (systolic blood pressure <90 mm Hg for at least 15 minutes or requiring inotropic support, not due to a cause other than PE, such as arrhythmia, hypovolemia, sepsis, or left ventricular [LV] dysfunction), pulselessness, or persistent profound bradycardia (heart rate <40 bpm with signs or symptoms of shock).
Definition for submassive PE: Acute PE without systemic hypotension (systolic blood pressure ≥90 mm Hg) but with either RV dysfunction or myocardial necrosis.
RV dysfunction means the presence of at least 1 of the following:

  • RV dilation (apical 4-chamber RV diameter divided by LV diameter >0.9) or RV systolic dysfunction on echocardiography
  • RV dilation (4-chamber RV diameter divided by LV diameter >0.9) on CT
  • Elevation of BNP (>90 pg/mL)
  • Elevation of N-terminal pro-BNP (>500 pg/mL); or
  • Electrocardiographic changes (new complete or incomplete right bundle-branch block, anteroseptal ST elevation or depression, or anteroseptal T-wave inversion)

Myocardial necrosis is defined as either of the following:

  • Elevation of troponin I (>0.4 ng/mL) or
    Elevation of troponin T (>0.1 ng/mL)

Odds ratio for short-term mortality for RV dysfunction on echocardiography = 2.53 (95% CI 1.17 to 5.50).
Troponin elevations had an odds ratio for mortality of 5.90 (95% CI 2.68 to 12.95).
Definition for low risk PE: those with normal RV function and no elevations in biomarkers with short-term mortality rates approaching ≈ 1%

Recommendations for Initial Anticoagulation for Acute PE

  • Therapeutic anticoagulation with subcutaneous LMWH, intravenous or subcutaneous UFH with monitoring, unmonitored weight-based subcutaneous UFH, or subcutaneous fondaparinux should be given to patients with objectively confirmed PE and no contraindications to anticoagulation (Class I; Level of Evidence A).
  • Therapeutic anticoagulation during the diagnostic workup should be given to patients with intermediate or high clinical probability of PE and no contraindications to anticoagulation (Class I; Level of Evidence C).

 
Patients treated with a fibrinolytic agent have faster restoration of lung perfusion. At 24 hours, patients treated with heparin have no substantial improvement in pulmonary blood flow, whereas patients treated with adjunctive fibrinolysis manifest a 30% to 35% reduction in total perfusion defect. However, by 7 days, blood flow improves similarly (≈65% to 70% reduction in total defect).
Thirteen placebo-controlled randomized trials of fibrinolysis for acute PE have been published, but only a subset evaluated massive PE specifically.
When Wan et al restricted their analysis to those trials with massive PE, they identified a significant reduction in recurrent PE or death from 19.0% with heparin alone to 9.4% with fibrinolysis (odds ratio 0.45, 95% CI 0.22 to 0.90).
Data from registries indicate that the short-term mortality rate directly attributable to submassive PE treated with heparin anticoagulation is probably < 3.0%. The implication is that even if adjunctive fibrinolytic therapy has extremely high efficacy, for example, a 30% relative reduction in mortality, the effect size on mortality due to submassive PE is probably < 1%. Thus, secondary adverse outcomes such as persistent RV dysfunction, chronic thromboembolic pulmonary hypertension, and impaired quality of life represent appropriate surrogate goals of treatment.
Data suggest that compared with heparin alone, heparin plus fibrinolysis yields a significant favorable change in right ventricular systolic pressure and pulmonary arterial pressure incident between the time of diagnosis and follow-up. Patients with low-risk PE have an unfavorable risk-benefit ratio with fibrinolysis. Patients with PE that causes hypotension probably do benefit from fibrinolysis. Management of submassive PE crosses the zone of equipoise, requiring the clinician to use clinical judgment.

An algorithm is proposed:

Two criteria can be used to assist in determining whether a patient is more likely to benefit from fibrinolysis: (1) Evidence of present or developing circulatory or respiratory insufficiency; or (2) evidence of moderate to severe RV injury.
Evidence of circulatory failure includes any episode of hypotension or a persistent shock index (heart rate in beats per minute divided by systolic blood pressure in millimeters of mercury) >1
The definition of respiratory insufficiency may include hypoxemia, defined as a pulse oximetry reading < 95% when the patient is breathing room air and clinical judgment that the patient appears to be in respiratory distress. Alternatively, respiratory distress can be quantified by the numeric Borg score, which assesses the severity of dyspnea from 0 to 10 (0=no dyspnea and 10=sensation of choking to death).
Evidence of moderate to severe RV injury may be derived from Doppler echocardiography that demonstrates any degree of RV hypokinesis, McConnell’s sign (a distinct regional pattern of RV dysfunction with akinesis of the mid free wall but normal motion at the apex), interventricular septal shift or bowing, or an estimated RVSP > 40 mm Hg.
Biomarker evidence of moderate to severe RV injury includes major elevation of troponin measurement or brain natriuretic peptides.
Two trials are currently ongoing that aim to assess effect of thrombolysis on patients with submassive PE: PEITHO and TOPCOAT

Recommendations for Fibrinolysis for Acute PE

  • Fibrinolysis is reasonable for patients with massive acute PE and acceptable risk of bleeding complications (Class IIa; Level of Evidence B).
  • Fibrinolysis may be considered for patients with submassive acute PE judged to have clinical evidence of adverse prognosis (new hemodynamic instability, worsening respiratory insufficiency, severe RV dysfunction, or major myocardial necrosis) and low risk of bleeding complications (Class IIb; Level of Evidence C).
  • Fibrinolysis is not recommended for patients with low-risk PE (Class III; Level of Evidence B) or submassive acute PE with minor RV dysfunction, minor myocardial necrosis, and no clinical worsening (Class III; Level of Evidence B).
  • Fibrinolysis is not recommended for undifferentiated cardiac arrest (Class III; Level of Evidence B).

Recommendations for Catheter Embolectomy and Fragmentation

  • Depending on local expertise, either catheter embolectomy and fragmentation or surgical embolectomy is reasonable for patients with massive PE and contraindications to fibrinolysis (Class IIa; Level of Evidence C).
  • Catheter embolectomy and fragmentation or surgical embolectomy is reasonable for patients with massive PE who remain unstable after receiving fibrinolysis (Class IIa; Level of Evidence C).
  • For patients with massive PE who cannot receive fibrinolysis or who remain unstable after fibrinolysis, it is reasonable to consider transfer to an institution experienced in either catheter embolectomy or surgical embolectomy if these procedures are not available locally and safe transfer can be achieved (Class IIa; Level of Evidence C).
  • Either catheter embolectomy or surgical embolectomy may be considered for patients with submassive acute PE judged to have clinical evidence of adverse prognosis (new hemodynamic instability, worsening respiratory failure, severe RV dysfunction, or major myocardial necrosis) (Class IIb; Level of Evidence C).
  • Catheter embolectomy and surgical thrombectomy are not recommended for patients with low-risk PE or submassive acute PE with minor RV dysfunction, minor myocardial necrosis, and no clinical worsening (Class III; Level of Evidence C).

 
Management of Massive and Submassive Pulmonary Embolism, Iliofemoral Deep Vein Thrombosis, and Chronic Thromboembolic Pulmonary Hypertension
Circulation. 2011 Apr 26;123(16):1788-1830 (Free Full Text)

Acute Med, All Updates, ICU, Resus

LRAs for acute asthma?

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As far as I’m concerned the jury is still out here since this small study was terminated early, more patients in the montelukast group received magnesium and / or aminophylline, and it is unclear how the groups compared with regard to other other acute therapies such as beta-agonists and steroids.

BACKGROUND: Although leukotriene receptor antagonists have an established role in the management of patients with chronic asthma, their efficacy in an acute asthma exacerbation is not fully known.
METHODS: 87 adults with acute asthma requiring hospitalisation were randomly assigned to receive either montelukast 10 mg or placebo on admission and every evening thereafter for 4 weeks (when they were reviewed as outpatients). All patients were admitted under the care of a consultant chest physician and received full care for acute asthma according to the British Thoracic Society guidelines. The primary end point was the difference in peak expiratory flow (PEF) between active and placebo treatment the morning following admission.
RESULTS: Primary end point data were analysed for 73 patients. At study entry, patients who received montelukast (n=37) had a mean (±SD) PEF of 227.6 (±56.9) l/min (47.6% predicted) and those who received placebo (n=36) had a PEF of 240.3 (±99.8) l/min (49.6% predicted). The morning after admission, patients who received montelukast achieved a PEF of 389.6 (±109.7) l/min (81.4% predicted) compared with 332.3 (±124.9) l/min (69.8% predicted) for placebo (p=0.046). The mean difference between treatment groups was 57.4 l/min (95% CI of 1.15 to 113.6 l/min or 1.95-21.2% predicted).
CONCLUSION: In acute asthma exacerbations the additional administration of oral montelukast results in a significantly higher PEF the morning after admission than that achievable with current standard treatment.

Oral montelukast in acute asthma exacerbations: a randomised, double-blind, placebo-controlled trial
Thorax. 2011 Jan;66(1):7-11

Acute Med, All Updates, ICU, Resus

Thrombolysis for PE after limb surgery

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A patient develops shock and dyspnoea on the orthopaedic ward after a total knee replacement and massive pulmonary embolism is confirmed radiologically. Would you give a fibrinolytic or is it contraindicated? Harry Wright and colleagues did, but before giving 50 mg of intravenous rtPA they applied a tourniquet (Cryocuff) to the limb to limit the proportion of the systemic thrombolytic agent that would reach the site of the surgery. The tourniquet was inflated just before the infusion and was left on for one hour. There was some oozing of blood from the postoperative wound, which settled with bandage compression. The authors state that the inflation time of one hour was sufficient for the thrombolytic agent to be largely eliminated from the circulation, since alteplase has a plasma half-life of less than five minutes, although some plasminogen activator activity does persist for up to four hours.

The patient was well at three month follow up. They suggest:

Given the success in this case, we believe that major limb surgery no longer represents a contraindication to thrombolysis.

Thrombolysis for postoperative pulmonary embolism: limiting the risk of haemorrhage
Thorax. 2011 May;66(5):452

Acute Med, All Updates, ICU

H1N1 or CAP?

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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