Fan Y, Zhang AM, Xiao YB et al. Warm versus cold cardioplegia for heart surgery:a meta-analysis. Eur J Cardio-thoracic Surg Apr 2010: 912-19.
In a nutshell
This is a meta-analysis of 41 RCTs (published 1992-2005) comparing warm (32-37oC) and lukewarm (28-30oC) blood cardioplegia (CP) with cold (4-15oC) blood or crystalloid CP. It involved 5879 patients (2944 warm/lukewarm blood, 2007 cold blood, and 928 cold crystalloid CP). Most of the studies were conducted in the setting of CABG surgery. No significant difference was found in in-hospital mortality, MI, low cardiac output syndrome, IABP use, or postoperative atrial fibrillation. There was also no significant difference in the incidence of stroke. However, subgroup analysis showed that more strokes occurred in patients receiving warm blood CP compared with cold crystalloid CP. Warm CP was associated with significantly improved postoperative
cardiac index (CI). The cardiac troponin concentration at day 0, day 1, and peak value, as well as peak CK-MB, after heart surgery were lower in warm CP than in the cold CP group.
Second opinion
Myocardial (MC) protection during heart surgery aims to preserve MC function while providing a bloodless and motionless field. This is achieved by decreasing MC oxygen (O2) demand. Electro-mechanical arrest alone decreases O2 requirement by 90% with only slight further decrease attributed to lowering MC temperature to 11oC. Cold CP, on the other hand, might inhibit MC enzymes and delay metabolic and functional recovery after surgery. This meta-analysis has found an improvement of CI and a lower release of cardiac enzymes (indicating less MC damage). However, this was not translated into in-hospital outcome improvement. The lack of follow-up in the analysed RCTs failed to show the impact of decreased MC damage on the long-term outcome. CP temperature is not the only factor affecting MC protection and surgeons who use cold CP may modify it to include warm CP (warm induction or hot shot). Other factors that might influence the outcome include antegrade versus retrograde delivery, intermittent versus continuous, composition and volume of CP; and the type of surgical procedure.
The verdict
- Various improvements in CP techniques have contributed greatly to the significant advances in cardiac surgery.
- Both warm and cold CP are effective and safe, with better haemodynamic performance and less cardiac myocyte injury associated with warm CP.
- Ongoing studies will likely lead to the incorporation of additional cardio-protective techniques.
Mohammed Komber
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Graham Cooper
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