Meta Analysis Fluid resuscitation with colloid or crystalloid
This review may be edited
Summary
Posted By:	Gordon S. Doig
E-Mail:	Gordon.Doig@EvidenceBased.net
Posted Date:	March 6th, 2001
Title:	Fluid resuscitation with colloid or crystalloid
Authors:	Gill Schierhout and Ian Roberts.
Reference:	BMJ 1998;316:961-4
Link:	Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract:	Objective: To determine the effect on mortality of resuscitation with colloid solutions compared with resuscitation with crystalloids. Design: Systematic review of randomised controlled trials of resuscitation with colloids compared with crystalloids for volume replacement of critically ill patients; analysis stratified according to patient type and quality of allocation concealment. Subjects: 37 randomised controlled trials were eligible, of which 26 unconfounded trials compared colloids with crystalloids (n=1622). (The 10 trials that compared colloid in hypertonic crystalloid with isotonic crystalloid (n=1422) and one trial that compared colloid in isotonic crystalloid with hypertonic crystalloid (n=38) are described in the longer version on our website www.bmj.com). Main outcome measures: Mortality from all causes at end of follow up for each trial. Results: Resuscitation with colloids was associated with an increased absolute risk of mortality of 4% (95% confidence interval 0% to 8%), or four extra deaths for every 100 patients resuscitated. The summary effect measure shifted towards increased mortality with colloids when only trials with adequate concealment of allocation were included. There was no evidence for differences in effect among patients with different types of injury that required fluid resuscitation. Conclusions: This systematic review does not support the continued use of colloids for volume replacement in critically ill patients.
Are the Results Valid?
1. Did the overview address a focused clinical question?
	Yes. The authors sought to address the question of 'the effect on mortality of resuscitation with colloid solutions compared with resuscitation with crystalloids'.
2. Were the criteria used to select articles for inclusion appropriate?
	Yes. All randomized trials in critically ill patients were included.
3. Is it unlikely that important, relevant studies were missed?
	Yes. The computerized search was extensive and included Medline, EMBASE, the Cochrane Trials Registry combinded with hand searches of reference lists and contacting authors. It is unlikely trials were missed.
4. Was the validity of the included studies appraised?
	Yes. The studies were graded for quality of allocation concealment. No other methodological criteria were graded.
5. Were assessments of studies reproducible?
	Unsure. The reviewers report that inclusion criteria were determined by each person but they do not report the results or agreement (kappa) on the results.
6. Were the results similar from study to study?
	Yes. There appears to be no statistical heterogeneity.
What are the Results?
1. What are the overall results of the overview?
	There are many different statistical methods available for performing a meta-analysis and the Mantel-Haenszel approach is the most popular fixed effects model for a number of reasons, first and formost being that the calculation of a summary Odds Ratio using the M-H method is very stable and robust. In their statistical methods section, the authors report using the M-H approach to calculate the relative risks (actually Odds Ratios). The reported overall RR was 1.19 (0.98-1.45). Technically, this finding is not 'statistically significant'. I re-inputed the data and computed the overall Odds Ratio using SAS version 6.12 and came up with an OR of 1.202(.98-1.46). This is associated with a p-value of 0.064. The major claim of 'statistical significance' was made based on a calculation of 'an absolute risk of mortality for resuscitation with colloids of 4% (0%-8%)'[p962, last paragraph]. The statistical methods section does not report which methodology was used to calculate absolute risk differences and I am unaware that the M-H method can be used to do this. I was unable to reproduce these results.
2. How precise were the results?
	See above.
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care
	Yes. This is a useful summary of trials on colliods vs. crystalloids and serves to make us aware that there is still controversy in their usage. It emphasizes the poor quality of trials perfromed in the 'surgery' literature and begs for better trials in this area. It does not provide clear cut results in any particular indication, once again emphasizing the need for better studies.
2. Were all clinically important outcomes considered?
	Yes. Mortality is probably the appropriate outcome, but length of stay should be considered too. In the trauma literature, quality of life is extremely important to consider and this was not addressed.
3. Are the benefits worth the harms and costs?
	Unsure. We must remember that upfront costs of colliods are greater BUT we have no information on 'downstream' costs. Fully costed outcomes trials would be needed to resolve this issue.
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