Murray Score For Acute Lung Injury Calculator

How does this Murray score for acute lung injury calculator work?

This health tool evaluates the need for intervention in cases of severe adult respiratory failure and whether the patient should be referred for conventional ventilation or extracorporeal membrane oxygenation (ECMO).

While the main clinical triggers for using ECMO are hypoxemia and/or hypercapnoea, by using a score such as Murray – the clinician is provided with results from different pulmonary variables from the level of positive end expiratory pressure, the level of hypoxemia, the dynamic pulmonary compliance and a composite of chest x-ray.

In the Murray score calculator there are four factors taken into account, however the user can select either of them, depending on availability:

■ Hypoxemia PaO₂/FiO₂ in mmHg on 100% oxygen for at least 20 minutes. In case the result is given in kPa, it should be multiplied by 7.5 to reveal the mmHg value.

■ PEEP in cmH₂O – as the value presented on the ventilator.

■ Compliance  in ml/cmH₂O – where compliance is calculated as the ratio between tidal volume in mL and PIP– PEEP.

■ Alveolar consolidation in how many quadrants – also known as no. of quadrants with infiltration seen on chest x-ray.

Acute respiratory failure is currently treated through ventilation techniques and treatments with steroids, bronchoscopy or nitric oxide. However, despite all the best efforts, this is still a condition with high mortality rates.

Murray score interpretation

The following table presents the ranges used in the Murray lung injury score and the number of points awarded for each component.

Unlike other scores, the final result comprises of an average of the points in the factors available. This means that if the user chooses answers from 3 variables, the total number of points obtained will be divided by 3 in order to obtain the final Murray score.

Therefore the total number of points varies from 0 to 4 while the Murray score ranges from 0 to 4.

Scores equal to or above 3 (≥2.5 if rapid deterioration) are part of the criteria used in the referral to extracorporeal membrane oxygenation in acute lung injury.

Another interpretation of the score indicates that:

■ 0 - no lung injury;

■ 1.0 - 2.5 - mild to moderate lung injury;

■ ≥2.5 - severe lung injury (ARDS – Acute respiratory distress syndrome).

ECMO guidelines

The CESAR study is a multicentre randomized controlled trial that aims to reveal the differences in terms of efficacy of treatment and costs between conventional ventilator support and extracorporeal membrane oxygenation for severe lung failure.

Inclusion criteria – eligible patients should be:

■ Aged 18 to 65;

■ Diagnosed with potentially reversible respiratory failure;

■ Murray score of 3.0 or higher or uncompensated hypercapnoea with pH <7.2.

Certain exclusion criteria were also put in place for patients presenting:

■ high pressure (peak inspiratory pressure >30 cmH₂O) or high FiO₂ (>0·8) ventilation for more than 168 h (7 days);

■ signs of intracranial bleeding;

■ any other contraindication to limited heparinisation.

Several clinical health units have started offering ECMO treatments, for instance there are already 5 centers in the UK which offer assistance to patients with reversible disease presented with severe hypoxemia.

This is a technique that brings oxygen to the blood from outside the body and is often coupled with extracorporeal carbon dioxide removal.

Eligibility criteria usually include those above in the CESAR study plus:

■ Severe hypoxaemia (e.g. PaO₂/FiO₂ <13.3 kPa);

■ Inability to achieve lung protective tidal volumes and pressures (tidal volume < 6 mL/Kg predicted body weight, plateau pressure <30 cmH₂O);

■ Significant air leak/bronchopleural fistula;

■ Failure to improve with other therapies.

References

1) Murray JF, Matthay MA, Luce JM, Flick MR. (1988) An expanded definition of the adult respiratory distress syndrome. Am Rev Respir Dis; 138(3):720-3.

2) Raghavendran K, Napolitano LM. (2011) ALI and ARDS: Challenges and Advances. Crit Care Clin; 27(3): 429–437.

3) Paden ML, Conrad SA, Rycus PT, Thiagarajan RR, ELSO Registry. (2013) Extracorporeal Life Support Organization Registry Report 2012. ASAIO J; 59(3):202-10.

4) Peek GJ et al. (2009) Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial. TheLancet. Volume 374, No. 9698, p1351–1363

5) Maskara S, Sen N, Raj JP, Korah I, Antonisamy B. (2000) Correlation between lung injury score and serum albumin levels in patients at risk for developing acute lung injury. Nutrition; 16(2):91-4.