Criteria abstracted from The Users' Guide to Medical Literature, from the Health Information Research Unit and Clinical Epidemiology and Biostatistics, McMaster University

Highlighted lines and questions below provide links to the pertinent description of criteria in The EBM User's Guide, now available at the Canadian Centres for Health Evidence

Article Reviewed:

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Fluid resuscitation with colloid or crystalloid solutions in critically ill patients: a systematic review of randomised trials

Schierhout G, Roberts I.

Br Med J 1998; 316: 961-5. [full-text]

Reviewed by Michael J. Verive, MD, Hope Children's Hospital, Oak Lawn, IL

Review posted April 19, 1999

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I. Are the results of the study valid?

A. Primary questions:

1. Did the overview address a focused clinical question?

Yes. The overview sought to determine the effect on mortality of resuscitation with colloid solutions compared with resuscitation with crystalloid solutions. Additional information on hospital stay and renal and pulmonary complications was sought in trials among surgical patients, although this was not the main focus of the overview.

2. Were the criteria used to select articles for inclusion appropriate?

Yes. An exhaustive review of the literature was made by searching the Cochrane Controlled Trials Register, Medline, Embase, and BIDS Index to Scientific and Technical Proceedings, through June, 1997, for trials "in critically ill patients (excluding neonates) who required fluid resuscitation [and] were assigned to colloid or crystalloid resuscitation protocols on the basis of random or quasi-random allocation." An additional manual search was performed on 29 international journals and proceedings of several international meetings on fluid therapy and reference lists of trials and review articles. The authors of identified trials were contacted for other published or unpublished trials as well.

B. Secondary questions:

3. Is it unlikely that important, relevant studies were missed?

Yes, it is unlikely. Although it is always possible that some studies will be missed by any search method, the comprehensive search performed for this overview made it unlikely that important, relevant studies were missed.

4. Was the validity of the included studies appraised?

To an extent. The sole assessment of validity employed was adequacy of concealment (1). Although there is no consensus regarding how rigorously systematic reviews should analyze and report trials' validity, more than one measure in this review would have been helpful.

5. Were assessments of studies reproducible?

Unable to verify. The eligibility of studies was determined by two reviewers who independently extracted the data, and resolved their disagreements by discussion. However, no kappa statistic or other measure of inter-observer variability was mentioned, making it impossible to determine the degree of observer agreement.

6. Were the results similar from study to study?

A qualified yes. Heterogeneity between trials was tested with chi-squared analysis, using p < 0.05 indicating significant heterogeneity. When there was no significant heterogeneity a fixed effects model was used to calculate summary relative risks and 95% confidence intervals for dichotomous data. Additional linear regression was used to test whether results of meta-analyses might have been the result of publication bias. Using these methods, there was no significant heterogeneity between trials, and no evidence of publication bias.

II. What are the results?

1. What are the overall results of the review?

The pooled relative risk of mortality for all patient groups was 1.19 (95% confidence interval 0.98 to 1.45). The risk of mortality with resuscitation using colloids was 24%, compared to 20% risk of mortality with resuscitation using crystalloids, giving an increase in absolute risk of mortality for resuscitation with colloids of 4% (95% CI 0% - 8%). When only trials with adequate concealment of allocation were analyzed, the increase in absolute risk of mortality for resuscitation with colloids was 7% (95% CI -1 to 15%), indicating no statistically significant increase in mortality for resuscitation with colloids, although the trend was in that direction. The overview concluded that the use of colloids for volume resuscitation in critically ill patients is not supported by the literature.

However, there are significant limitations to this systematic review. Although the authors made an attempt to compare different solutions based on colloid content and hypertonicity, the multiple types of colloid and combinations with iso- and hypertonic saline make any meaningful comparisons difficult.

2. How precise were the results?

Given the imprecise nature of assumptions that are made by systematic overviews (fixed effects, publication bias, qualification of randomization methods, inter-observer reliability/agreement, etc.), the results of the meta-analyses in this overview had sufficient precision and statistical power to support the main conclusion, i.e.,. we can be certain (with 95% confidence) that the true increase in overall mortality was between 0 and 8%.

III. Will the results help me in caring for my patients?

1. Can the results be applied to my patient care?

Possibly. Fluid resuscitation is an integral component of the management of critically ill pediatric patients. However, this overview addressed resuscitation in all patients, and did not stratify results by age. Our older pediatric patients have physiology more similar to that of adults; in these selected patients it may be possible to apply the results of this overview. Studies of fluid resuscitation in pediatric burn patients (2), and in pediatric patients with hypovolemic shock (3) have not favored either crystalloid or colloid for initial resuscitation.

As stated above, there was considerable variation in the composition of fluids used for resuscitation, as well as resuscitation algorithms, making comparisons problematic.

2. Were all clinically important outcomes considered?

A debatable "yes." As the main purpose of fluid resuscitation is to reverse the state of uncompensated shock that can result in death, the study's main objective - to determine the relative risk of mortality due to resuscitation with colloids or crystalloids - was appropriate.

However, other outcomes, such as complications and length of stay are also of great value. One understands, however, given the limitations of data extraction from multiple studies (and that not all studies even reported mortality), such an effort would be very difficult to perform through literature review alone. Prospective studies looking at all of these outcomes would produce the most useful comparison data, and are sorely needed.

3. Are the benefits worth the harms and costs?

This analysis only assessed the potential harm of using colloids for fluid resuscitation; no benefits were examined. However, if there is truly an increased mortality rate from the use of colloids, this could well outweigh any potential benefit, particularly unproven ones.

References:

1. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Dimensions of methodological quality associated with estimate of treatment effects in controlled trials. JAMA 1995;273:408-412. [abstract]
2. Cocks AJ, O'Connell A, Martin H. Crystalloids, colloids and kids: a review of paediatric burns in intensive care. Burns 1998 Dec;24(8):717-24. [abstract]
3. Thomas NJ, Carcillo JA. Hypovolemic shock in pediatric patients. New Horiz 1998 May;6(2):120-9. [abstract]

Related Reviews:

Cochrane Injuries Group Albumin Reviewers. Human albumin administration in critically ill patients: systematic review of randomised controlled trials. Br Med J 1998; 317: 235-240. [full-text]

Review, by A. Torres

Choi PT, Yip G, Quinonez LG, Cook DJ. Crystalloids vs. colloids in fluid resuscitation: a systematic review. Crit Care Med 1999; 27:200-10. [abstract]

Review, by M. Sanchez-Mendiola

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