Depth of Anaesthesia and Postoperative Cognitive Decline in Patients Undergoing Heart Surgery

This study has been completed.
Information provided by (Responsible Party):
King's College Hospital NHS Trust Identifier:
First received: December 4, 2012
Last updated: May 13, 2015
Last verified: December 2012

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).

Condition Intervention
Cardiac Bypass Surgery in Adult Patients 65 Years and Older
Postoperative Cognitive Dysfunction
Postoperative Delirium
Other: Targeted intra-operative depth of anaesthesia

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, 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

Resource links provided by NLM:

Further study details as provided by King's College Hospital NHS Trust:

Primary Outcome Measures:
  • Incidence of postoperative cognitive decline after bypass surgery [ Time Frame: Six weeks after bypass surgery ] [ Designated as safety issue: No ]

Secondary Outcome Measures:
  • Incidence of postoperative cognitive decline 5 days and 1 year after bypass surgery [ Time Frame: Five days and one year postoperatively ] [ Designated as safety issue: No ]
  • 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 ] [ Designated as safety issue: No ]
  • Postoperative Delirium [ Time Frame: 3-5 days postoperatively ] [ Designated as safety issue: No ]
  • Postoperative central nervous system and myocardial biochemical markers [ Time Frame: up to 48 hours postoperatively ]

Enrollment: 88
Study Start Date: January 2011
Study Completion Date: February 2015
Primary Completion Date: April 2014 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
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.


Ages Eligible for Study:   65 Years and older
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • patients undergoing elective coronary artery bypass graft surgery
  • patients at 65 years of age and older

Exclusion Criteria:

  • diseases of the central nervous system including dementia
  • inadequate knowledge of English
  • a current or past psychiatric illness
  • current use of tranquilizers or antidepressants
  • severe visual, auditory, or motor handicap
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Please refer to this study by its identifier: NCT01743456

United Kingdom
King's College Hospital NHS Foundation Trust
London, Denmark Hill, United Kingdom, SE5 9RS
Sponsors and Collaborators
King's College Hospital NHS Trust
Principal Investigator: David Green, FRCA, MBA King's College Hospital NHS Trust
  More Information

Responsible Party: King's College Hospital NHS Trust Identifier: NCT01743456     History of Changes
Other Study ID Numbers: KHC11-001
Study First Received: December 4, 2012
Last Updated: May 13, 2015
Health Authority: United Kingdom: National Research Ethics Service

Keywords provided by King's College Hospital NHS Trust:
Postoperative cognitive dysfunction
Coronary artery bypass graft surgery
Postoperative cognitive improvement
Postoperative delirium

Additional relevant MeSH terms:
Cognition Disorders
Delirium, Dementia, Amnestic, Cognitive Disorders
Mental Disorders
Central Nervous System Agents
Central Nervous System Depressants
Pharmacologic Actions
Physiological Effects of Drugs
Therapeutic Uses processed this record on November 24, 2015