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Fluid Management in ALI

Citation/s: The National Heart, Lung and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. Comparison of Two Fluid-Management Strategies in Acute Lung Injury. NEJM 2006; 354:2564-2575
Lead author: H P Weiderman

Three-part Clinical Question: In patients with acute lung injury for less than 48 hours does a restrictive fluid strategy improve mortality compared to a liberal fluid strategy.

Search Terms: ALI, ARDS, Therapy

The Study: Non-blinded randomised controlled trial with intention-to-treat.

The Study Patients: ALI defined as PaO₂/FiO₂ <300mmHg, receiving positive pressure ventilation via a tracheal tube. They all had a pulmonary artery catheter or central venous catheter or there was an intention was to insert one. Exclusion criteria: These included - PAC after onset of ALI, ALI for >48hrs, severe lung disease, physician refusal. Of the 11,512 patients screened 10,511 were excluded (21% already had a PAC, 16% physician refusal, 14% had chronic lung disease.

The mean time from admission to ICU to protocol initiation was approximately 40hrs. At that time patients were in, on average, a 2.6 litre positive balance from admission.
 

Control group (N = 498; 497 analysed): (N=498, 497 analysed). Patients were ventilated according to the ARDS Network Protocol, and weaned also by protocol. Based on haemodynamic variables measured by PAC or CVC, interventions were by a protocol allowing liberal use of fluid. The mean (+/-SE) fluid balance in the first 7 days in this group was 6992+/-552 ml.
 

Experimental group (N = 503; 503 analysed): (N=503, 503 analysed). As for the control group except the protocol delivered conservative fluid management (see paper). The mean (+/-SE) fluid balance in the first 7 days in this group was -136 +/- 491ml.

The Evidence:

Comments:
Metabolic alkalosis and electrolyte imbalances were more common in the conservative group (p=0.001). Most of these events were not serious (3/42 in the conservative fluid group) and the incidence was low.

EBM questions:

1) Do the methods allow the adequate testing of the hypothesis? Yes.
2) Do the statistical tests correctly test the results to allow differentiation of statistically significant result? Yes.
3) Are conclusions valid in light of results? Yes, the conclusions are that mortality at 60 days is unchanged with a conservative fluid regimen, but that ICU stay was shorter and a shorter duration of ventilation was required.
4) Did results get omitted, and why? No.
5) Did they suggest areas of further research? No

6) Did they make any recommendations based on the results and were they appropriate? Yes. The authors suggested that these results supported the use of a conservative fluid strategy in these patients. This seems appropriate in similar patients to those included in the trial (see below).
7) Is this study relevant to my clinical practice? Yes, this intervention appears to make a clinically significant difference, and can be easily implemented. However when assessing applicability to our own patients we must consider the large number of excluded patients. The findings of this study are applicable to ICU patients, without chronic lung disease, who have been well resuscitated in the initial stages of their ICU stay (without a PAC).

 8) What level of evidence does this study represent? 1⁺⁺
9) What grade of recommendation can I make on this result alone? A
10) What grade of recommendation can I make when this study is considered along with
other available evidence? A
11) Should I change my practice because of these results? You should consider changing your practice. This is a well conducted randomised controlled trial with low risk of bias. Although it does not demonstrate a reduction in mortality it does demonstrate a reduce ICU stay and reduced duration of ventilation in the treatment group. These are probably clinically important outcomes and this treatment seems inexpensive, comparatively free from side effects and relatively easy to implement. This with the caveat of the point made in 6.
12) Should I audit my current practice because of these results? Yes, with respect to fluid balance in ALI / ARDS patients, adverse effects of treatment and outcomes.

 

Appraised by: P Hersey , Aberdeen Royal Infirmary, Aberdeen, Scotland; 18 August 2006
Email: phersey@nhs.net

Kill or Update By: August 2009

Reviewed & edited by BC & CC

Citation: EBM Critical Appraisals. Scottish Intensive Care Society EBM Group. 2006. Hersey P. The National Heart, Lung and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. Comparison of Two Fluid-Management Strategies in Acute Lung Injury. NEJM 2006; 354:1-12

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