The effect of Trendelenburg positioning in laparoscopic colorectal surgery on intraocular pressure and cognitive function

Trendelenburg positioning is frequently used during laparoscopic surgery particularly when access to the pelvis is required. With improvements in laparoscopic skills, high risk patients and more complex procedures are now frequently being performed laparoscopically. (Improvement, 2016) The aim of this thesis is to investigate the effect of Trendelenburg positioning on intraocular pressure (IOP) and cognitive function. Chapters 2 and 4 look at the effect of Trendelenburg positioning on IOP. Perioperative vision loss occurs rarely but it is a life changing complication. A rise in IOP is a recognised risk factor for POVL. The incidence of POVL following laparoscopic colorectal surgery has been quoted as 1.24 in 10,000 cases. (Pinkney et al., 2012) Chapter 2 is an observational study during which IOP was monitored during laparoscopic colorectal surgery. This was correlated with the degree of Trendelenburg tilt used during surgery. This study revealed an increase in IOP occurred which was dependent on the degree of Trendelenburg tilt as well as the time spent in this position (Pearson’s correlation coefficient was 0.78). Patients undergoing left-sided colonic resections had a mean maximum IOP rise of 15.2mmHg. Chapter 4 is a follow-on study which looked at acetazolamide as a method of reducing the IOP rise that occurred whilst in the Trendelenburg position. This was a randomised placebo controlled cross-over healthy volunteer study. After 4 hours of Trendelenburg, the mean IOP increase was 3.17mmHg in the placebo group compared to 0.02mmHg in the acetazolamide group (P