Depth of Anaesthesia and Postoperative Cognitive Decline in Patients Undergoing Heart Surgery
Post-Operative Cognitive Decline (POCD) is common after cardiac surgery and associated with increased morbidity and mortality. The pathophysiology of POCD is only poorly understood. Causes include hypoperfusion, microemboli and the systemic inflammatory response, which result in a reduction of cerebral oxygen delivery.
Cerebral oxygenation can be monitored non-invasively by measuring frontal lobe oxygen saturation (rSO2).
The bispectral index (BIS) of the electroencephalogram is widely known to measure depth of anaesthesia, and there is a high correlation between BIS, a dimensionless calculated number between 0 and 100, and clinical criteria of sedation. With BIS below 60 recall is extremely low.
The investigators demonstrated recently that inappropriately high levels of anaesthesia may be associated with poorer long-term outcomes in cognition after non-cardiac surgery (Ballard et al. 2012). Whether optimisation of the depth of anaesthesia and cerebral oxygenation has an effect on postoperative cognitive function in patients undergoing cardiac surgery is unknown.
The investigators hypothesize that the incidence of POCD in elderly patients (> 65 years old) at 6 weeks is less with mildly deep anaesthesia (BIS 50 +- 10) and optimised rSO2 (interventions when rSO2 drops below 15% of baseline reading) when compared with current practice (BIS blinded anaesthesia, reflecting moderately to highly deep anaesthesia and blinded rSO2 measurements).
|Cardiac Bypass Surgery in Adult Patients 65 Years and Older Postoperative Cognitive Dysfunction Postoperative Delirium||Other: Targeted intra-operative depth of anaesthesia|
|Study Design:||Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
|Official Title:||Effect of Depth of Anaesthesia on Postoperative Cognitive Decline in Patients Undergoing Coronary Artery Bypass Graft Surgery - a Prospectively Randomized Controlled Study|
- Incidence of postoperative cognitive decline after bypass surgery [ Time Frame: Six weeks after bypass surgery ]
- Incidence of postoperative cognitive decline 5 days and 1 year after bypass surgery [ Time Frame: Five days and one year postoperatively ]
- Difference in degree of postoperative cognitive decline at 5 days, 6 weeks or 1 year after bypass surgery [ Time Frame: 5days, 6 weeks or 1 year postoperatively ]
- Postoperative Delirium [ Time Frame: 3-5 days postoperatively ]
- Postoperative central nervous system and myocardial biochemical markers [ Time Frame: up to 48 hours postoperatively ]
|Study Start Date:||January 2011|
|Study Completion Date:||February 2015|
|Primary Completion Date:||April 2014 (Final data collection date for primary outcome measure)|
|No Intervention: Current practice (BIS and rSO2 blinded)|
|Experimental: Targeted intra-operative depth of anaesthesia||
Other: Targeted intra-operative depth of anaesthesia
The intervention group receives isoflurane at a concentration that results in a BIS value between 40-60 intra-operatively.
Please refer to this study by its ClinicalTrials.gov identifier: NCT01743456
|King's College Hospital NHS Foundation Trust|
|London, Denmark Hill, United Kingdom, SE5 9RS|
|Principal Investigator:||David Green, FRCA, MBA||King's College Hospital NHS Trust|