The effect of preoperative exercise and training on postoperative outcome

The overall aim of this thesis was to investigate the effect of preoperative exercise and training on postoperative outcome. Poor cardiorespiratory fitness has been associated with poor postoperative outcome including increased length of hospital stay and postoperative complications. Thus, increasing cardiorespiratory capacity prior to surgery via preoperative exercise training could potentially alter postoperative outcome. High intensity exercise training (HIIT) has been demonstrated to be an efficient training intervention to increase cardiorespiratory capacity in as little as 2 weeks. It was hypothesised that chronic preoperative exercise training (i.e. 2 weeks HIIT) would improve postoperative outcome measures (i.e. length of stay, complications and mortality) in urology cancer resection patients in comparison to a usual-care-only group (UC). Thirty-five urology cancer resection patients voluntarily enrolled into the study, of these thirty completed the study (15 UC, 15 EXP). There was a significant increase in length of stay (LOS) in the EXP group in comparison to the UC group (4.0 ±6.0 versus 3.0 ±1.5 days, P=0.03), respectively. However, after accounting for covariates (surgical severity, number of operations) LOS was not significantly different between groups (5.8 ±0.8 versus 5.0 ±0.8 days; P=0.24) for UC and EXP patients, respectively). There were no significant differences between groups for postoperative complications on days 1-8 post-surgery (P>0.05), despite significant differences between groups for VO2peak change data (-2.2 ±0.8 ml.kg-1.min-1 versus +1.3 ±0.8ml.kg-1.min-1; Eta2:0.24; P=0.02) for UC and EXP patients). Overall, two weeks preoperative HIIT does not appear to alter postoperative outcome in urology cancer resection patients.

The effect of two weeks preoperative HIIT was investigated in colorectal cancer resection patients. It was hypothesised that chronic preoperative exercise training (i.e. 2 weeks HIIT) would improve postoperative outcome measures (i.e. LOS, complications and mortality) in colorectal cancer resection patients in comparison to the UC group. Twenty-one colorectal patients voluntarily enrolled into the study and completed the study (12 UC, 9 EXP). There were no significant differences between groups for LOS, (7.0 ±8.5 versus 6.0 ±2.0 days, Eta2:0.04; P=0.38) for UC and EXP patients, respectively). The Cox Regression hazard ratio was 1.55, suggesting that there was a 55% increased likelihood of being discharged on any given postoperative time point in the EXP group when compared to the UC group (95% CI: 0.25 to 1.65; P=0.36). There were no significant differences between groups for postoperative complications for days 1-10 post-surgery (P>0.05). Though, there was a moderate to large effect size for a reduction in postoperative complications on the 2nd (Eta2: 0.09), 4th and 8th postoperative day (Eta2: 0.07), in favour of the EXP group. There were no significant differences between groups for cardiorespiratory measures (i.e. AT, VO2peak) (P0.05). Thus, 2 hours hypoxia (O2: 14.5%) did not appear to significantly alter salivary stress markers. Therefore, the role of the cross-stressor adaptation hypothesis in exercise induced cardioprotection is unclear.

The overall conclusion of this thesis is that preoperative exercise appears to improve postoperative outcome measures in AAA patients. However, the benefits of preoperative exercise training on postoperative outcome in colorectal and urology patients is equivocal. Though, there was a group effect on postoperative complications on days 2, 4 and 8 post-surgery in colorectal patients, in favour of the EXP group. Lastly, an acute bout of exercise did not appear to attenuate the stress response to a subsequent stressor.