POCD in patients receiving total knee replacement under deep vs light anesthesia: A randomized controlled trial

Area of Science:

• Anesthesiology
• Geriatric Medicine
• Neuroscience

Background:

• Postoperative cognitive dysfunction (POCD) is a growing concern in elderly patients, with increasing evidence linking it to the depth of general anesthesia.
• Previous studies have been limited by confounding factors such as varying levels of analgesia, making it difficult to isolate the effect of anesthesia depth.

Purpose of the Study:

• To compare the incidence of POCD in elderly patients undergoing total knee replacement under light versus deep general anesthesia, while maintaining comparable analgesia through nerve blocks.
• To investigate the impact of anesthesia depth on cognitive recovery and other perioperative outcomes.

Main Methods:

• A randomized controlled trial involving elderly patients (≥60 years) undergoing elective total knee replacement.
• Patients were assigned to either a light anesthesia group (BIS 40-50, LOBIS) or a deep anesthesia group (BIS 55-65, HIBIS).
• All patients received ultrasound-guided femoral and sciatic nerve blocks for analgesia. Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA) at baseline and at 1, 3, and 7 days post-surgery. POCD was defined using a Z score of >1.96.

Main Results:

• POCD occurred in 20% of patients in the LOBIS group compared to 3.3% in the HIBIS group (p=0.04).
• The diagnosis of POCD was primarily observed on postoperative day 1, with no cases detected at later assessments.
• Extubation time and recovery of directional ability were significantly shorter in the HIBIS group compared to the LOBIS group (p < 0.001 for both).

Conclusions:

• Lighter general anesthesia, when combined with effective nerve block analgesia, significantly reduces the incidence of POCD in elderly patients undergoing total knee replacement.
• Anesthesia depth is a modifiable factor that can be optimized to improve cognitive outcomes in the perioperative period for elderly surgical patients.