The association between preoperative Mini-Cog© score and postoperative delirium (POD): a retrospective cohort study

Background

The onset of delirium after major surgery is associated with worse in-hospital outcomes for major surgical patients. Best practice recommends assessing surgical patients for delirium risk factors and this includes screening for cognitive impairment. The Mini-Cog© is a short instrument which has been shown to predict postoperative delirium (POD) and other complications in elderly patients undergoing major elective surgery. The primary aim of this study was to ascertain whether a positive preoperative Mini-Cog© is associated with postoperative delirium in elective colorectal surgery patients at high-risk of mortality due to age or comorbidity. Secondary outcomes were 90-day mortality and length of stay.

Methods

This is a retrospective analysis of data gathered prospectively between October 2015 and December 2017. Baseline data were collected at a preoperative screening clinic, and postoperative data during daily ward rounds by the Perioperative Medicine team at The York Hospital.

Results

Three hundred nineteen patients were included in the final analysis, of which 52 (16%) were found to be cognitively impaired on the Mini-Cog©. Older patients (median difference 10 years, p < 0.001) and patients with cognitive impairment (OR 3.04, 95%CI 1.15 to 8.03, p = 0.019) were more likely to develop postoperative delirium in univariate analysis; however, cognitive impairment (OR 0.492, 95%CI 0.177 to 1.368, p = 0.174) loses its significance when controlled for by confounding factors in a logistic regression model. Cognitive impairment (OR 4.65, 95%CI 1.36 to 15.9, p = 0.02), frailty (OR 7.28, 95%CI 1.92 to 27.58, p = 0.009), American Society of Anesthesiologists (ASA) grade (OR 5.95, 95%CI 1.54 to 22.94, p = 0.006) and age (median difference 10 years, p = 0.002) were significantly associated with 90-day mortality in univariate analysis. Sex was the only factor significantly associated with length of stay in the multiple regression model, with males having a 3-day longer average length of stay than females (OR = 2.94, 95%CI 0.10–5.78).

Conclusions

Mini-Cog© is not independently associated with post-operative delirium in high-risk elective colorectal surgery patients in this cohort. Mini-Cog© shows promise as a possible predictor of 90-day mortality. Larger studies exploring preoperative cognitive status and postoperative confusion and mortality could improve risk-stratification for surgery and allocation of resources to those patients at higher risk.

Crystalloid or colloid for goal-directed fluid therapy in colorectal surgery

BACKGROUND

Goal-directed fluid therapy has been shown to improve outcomes after colorectal surgery, but the optimal type of i.v. fluid to use is yet to be established. Theoretical advantages of using hydroxyethyl starch (HES) for goal-directed therapy include a reduction in the total volume of fluid required, resulting in less tissue oedema. Recent work has demonstrated that new generations of HES have a good safety profile, but their routine use in the perioperative setting has not been demonstrated to confer outcome benefit.

METHODS

We randomly assigned 202 medium to high-risk patients undergoing elective colorectal surgery to receive either balanced 6% HES (130/0.4, Volulyte) or balanced crystalloid (Hartmann's solution) as haemodynamic optimization fluid. The primary outcome measure was the incidence of gastrointestinal (GI) morbidity on postoperative day 5. Secondary outcome measures included the incidence of postoperative complications, hospital length of stay, and the effect of trial fluids on coagulation and inflammation.

RESULTS

No difference was seen in the number of patients who suffered GI morbidity on postoperative day 5 [30% in the HES group vs 32% in the crystalloid group; adjusted odds ratio=0.96 (0.52-1.77)]. Subjects in the crystalloid group received more fluid [median (inter-quartile ranges) 3175 (2000-3700) vs 1875 (1500-3000) ml, P<0.001] and had a higher 24 h fluid balance [+4226 (3251-5779) vs +3610 (2443-4519) ml, P<0.001]. No difference in the incidence of postoperative complications was seen between the groups.

CONCLUSIONS

Goal-directed fluid therapy is possible with either crystalloid or HES. There is no evidence of a benefit in using HES over crystalloid, despite its use resulting in a lower 24 h fluid balance.