**10. Summary**

270 Perioperative Considerations in Cardiac Surgery

improvements manifest by an increase in cardiac index and reduction in SVR. No statistically significant difference was noted in the requirement of inotropic or vasoconstrictor support during the six hours of T3 therapy following surgery. The incidence

Bennett-Guerro et al randomised 211 patients undergoing CABG surgery62 believed to be at higher risk of requiring post-operative inotropic support (LVEF < 40%, age > 65 years or cardiac re-operation) to receive either T3, dopamine (as a positive control) or placebo. T3 treatment dose was again a 0.8g kg-1 bolus at AXC removal followed by an infusion of 0.12g kg-1.h-1 for six hours, weaned over the next five hours. The dopamine group received 5g.kg-1.min-1 for six hours, weaned over the next six hours. The post-operative low T3 state was prevented with T3 administration, however, this study failed to demonstrate any significant difference in post-operative haemodynamic performance or inotrope

In a third study of patients undergoing CABG, Mullis-Jansson et al randomised 170 patients to receive either T3 1g kg-1 at AXC removal followed by an infusion of 1g.kg-1 for six hours. In this trial, T3 therapy was demonstrated to have a significant haemodynamic benefit with an increase in cardiac index in the 12 hours following removal of the AXC but with no significant reduction in the SVR. The requirement for post-operative inotropic and post-operative mechanical circulatory support was also reduced in patients receiving T3 therapy. Post-operative myocardial injury as measured by biochemical markers and electrocardiographic criteria (assessed by an independent blinded cardiologist) was also

In a randomised trial of metabolic and hormonal therapy in patients undergoing first-time isolated CABG patients receiving T3 were demonstrated to have improved haemodynamic performance, reduced inotrope requirements and release of troponin I was significantly reduced for those patients administered T3 51. T3 therapy was administered as per the

In addition to the studies investigating peri-operative intravenous supplementation, the potential benefits of pre-operative oral administration of T3 have been investigated. Sirlak et al64 attempted to optimise TH levels in patients undergoing CABG with reduced LVEF (<30%). In this study, patients (n= 80) were randomised to receive either oral T3 therapy 125µg per day for seven days prior to surgery and from the first post-operative day until time of discharge or placebo therapy. At anaesthetic induction patients in the T3 treatment group were demonstrated to have significantly higher levels of serum fT3 and significantly reduced serum levels of TSH and T4. Although both groups had reductions in serum fT3 associated with surgery and institution of CPB, the magnitude of the effect was reduced in patients receiving oral T3 and with post-operative re-institution of T3 a more rapid return to baseline levels was noted. Although no benefit was seen in terms of improvement in haemodynamic performance at baseline between the groups, T3 treated patients had a significant increase in both cardiac index and mixed venous oxygen saturations in the first 24 hours when compared with the placebo group. In addition, inotrope requirements, requirement for mechanical circulatory support and intensive care unit length of stay were

Kaptein and colleagues performed a meta-analysis to investigate the effects of TH therapy on post-operative NTIS in adults, They analysed 14 randomised controlled trials (13 of which were in patients undergoing cardiac surgery)45. Patients were divided into low and high dose intravenous T3 groups and oral T3 groups. Patients in the high dose group tended

of post-operative atrial fibrillation was significantly reduced in the T3 group61.

requirements for patients receiving T3 therapy.

reduced for patients receiving T3 therapy63.

reduced for the T3 group64.

protocol originally set out in the trial by Klemperer et al13.

The NTIS is a common occurrence following cardiac surgery in both paediatric and adult populations. Supplementation with T3 leads to supra-normal T3 levels and has been shown in a number of studies to


As yet none of these trials has demonstrated a major benefit in terms of a significant reduction in post-operative morbidities and mortality and further work is required to ascertain the optimal dose and timing of administration to maximise the potential benefits of T3 therapy in the post-operative cardiac surgical patient.
