Comparison of Depth of Anaesthesia: PRST Score versus Bispectral Index in Patients Undergoing General Anaesthesia

Background: Accurate assessment of the depth of anaesthesia (DoA) is crucial to prevent intraoperative awareness and haemodynamic instability. The PRST (Pressure, Rate, Sweating, Tears) score is a traditional, clinical tool based on autonomic responses, while the Bispectral Index (BIS) is a processed electroencephalographic parameter. This study compared the efficacy of these two modalities in guiding anaesthesia administration.

Methods: A prospective, observational study was conducted on 60 American Society of Anesthesiologists (ASA) physical status I and II patients, aged 18–60 years, undergoing elective surgery under general anaesthesia. Patients were randomly assigned to two groups (n=30 each): Group B (anaesthesia guided by BIS, target 40-60) and Group P (anaesthesia guided by PRST score, target ≤2). Haemodynamic parameters, intraoperative anaesthetic consumption, recovery times, and incidence of awareness were recorded and compared.

Results: The two groups were comparable in demographic data. Intraoperative haemodynamics were more stable in Group B, with fewer episodes of tachycardia and hypertension (p < 0.05). The mean intraoperative propofol consumption was significantly lower in Group B (185.4 ± 32.1 mg) compared to Group P (245.7 ± 41.5 mg) (p = 0.001). Recovery was faster in Group B, with a mean extubation time of 8.2 ± 2.5 minutes versus 12.5 ± 3.8 minutes in Group P (p = 0.003). No patient in either group experienced explicit recall of intraoperative events. However, the PRST score showed a moderate correlation with BIS values (r = 0.68), but with significant inter-patient variability.

Conclusion: BIS-guided anaesthesia provided superior intraoperative haemodynamic stability, reduced anaesthetic consumption, and facilitated faster emergence compared to PRST-guided anaesthesia. While the PRST score remains a useful clinical adjunct, BIS monitoring offers a more precise and objective guide for managing the depth of anaesthesia.