Objective:
The aim of the study is to determine the appropriate level of anaesthesia for elderly patients when using Narcotrend for maintaining anaesthesia during surgery.

Material and methods:
A total of 135 elderly patients with intestinal tumours were randomly divided into 3 groups: A, B and C (during the surgery, the anaesthesia levels were maintained at D0, D2, and E1, respectively). Heart rate (HR) and Mean arterial pressure (MAP) were monitored at the following time points: T1 – before anaesthesia, T2 – before intubation, T3 – after intubation, T4 – during surgery, T5 – at the end of surgery, and T6 – at extubation. Additionally, cognitive function was evaluated through MMSE scores before and after the surgery.

Results:
Compared with T1, group A showed a significant acceleration in HR at T3, T5 and T6. However, no significant fluctuations in HR were observed in Group B and Group C. Furthermore, in T2 and T4, the MAP of all groups decreased, and the change was most significant in group C. After the surgery, the MMSE scores of Group B and Group C were higher. However, compared with group C, the dosage of anaesthetic drugs in group B was lower and the extubation time was shorter.

Conclusions:
Compared with D0, maintaining the anaesthesia level at D2 or E1 may be able to reduce the risk of postoperative cognitive dysfunction in elderly patients. Furthermore, compared to E1, the D2 level is more likely to maintain haemodynamic stability.