Central neuroaxial blockade improves case-mix adjusted mortality of the critically ill surgical patient

Full text

Introduction

Central neuroaxial blockade is known to provide good postoperative analgesia, hastens the return of gut function and may attenuate the `stress response' to surgery [1]. However, there may be haemodynamic instability in critically ill patients. Despite improvements in many physiological parameters, there is little published evidence of improvement in outcome following surgery with such a block. Comparison of mortality outcome in intensive care units must take into account differences in the case-mix of patients in order to be meaningful. We investigated the effect of neuroaxial blockade on mortality standardised for case-mix using the APACHE 2 prognostic indicator(SMR) [2].

Methods

205 adult patients admitted to the ICU for >8 h following major abdominal surgery were categorised according to whether they had received neuroaxial blockade (block: 91; no-block 113) in a retrospective contemporaneous cohort-controlled design. APACHE 2 scores, calculated risk of death, types of surgery, ICU lengths of stay and hospital length of stay were collected from the ICU database, and SMRs were calculated for each group. Demographic data was assessed using ANOVA and SMR by Poisson distribution.

Results

There was a significant improvement in SMR in the block group (P<0.01). The APACHE 2 scores and calculated risks of death were significantly lower in this group. Both hospital and ICU length of stay were significantly shorter in the block group. There were significant differences in the type of surgery performed between the two groups (Table).

Conclusions

Within the methodological restrictions of the non-randomised design this study demonstrated an improvement in outcome in critically ill patients who receive neuroaxial blockade. The use of SMR as the primary end-point ensures a meaningful comparison of the groups despite the obvious difference in severity of illness between the groups as it allows outcome comparison for critically ill patients against a previously defined standard.

Table