Tight Glucose Control – A Meta-analysis

Benefits & Risks of Tight Glucose Control in Critically Ill Adults; A Meta-Analysis. Weiner et al. JAMA. 2008;300(8):933-944.

This meta-analysis of 28 studies of “tight glucose control” on AICU inevitably includes papers studying different protocols on different patients and hence is limited in its applicability. I’m not sure that meta-analysis serves any purpose not bettered by a brief reading of the key studies of this concept, as there is significant heterogenity within the studies and the vast majority of the numbers come from a few well known trials. The failure of any study to replicate Van de Berge’s original 30% mortality reduction now begins to suggest that the benefit of tight glucose control is at best marginal and perhaps non-existent. There is of course a potential harm from the well documented increased risk of hypoglyceamia. The meta-analysis generates an RR of 0.93 (0.85-1.03) for tight glycaemic control. They could identify no stratified group that showed a consistent mortality benefit, including medical ICU patients (as in the original study).

The accompanying editorial is more useful and summarises the problems with investigating glucose control. Namely…

  1. van den Berghe used high infusion rates of glucose in combination with insulin
  2. Nutritional protocols have not been standardised, or even reported, in many of these studies.
  3. There’s no standardisation on the reporting of glucose monitoring – so it’s difficult to determine whether an individual study hit the targets set.
  4. Only intermittent sugar readings are reported, but it may be the pattern of glucose values over a time frame is important. (It seems clear that any protocol that allows episodes of severe hypo or hyperglycaemia is likely to undo any benefit of well controlled mean values at the very least).

Where to go from here? It seems the evidence base for tight glucose control is increasingly thin.

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