Effect of bispectral index monitoring on postoperative delirium in elderly patients with moderate or severe hypertension undergoing total knee arthroplasty surgery

Abstract

Objective To investigate the effect of BIS-guided intravenous anesthesia on postoperative delirium (POD) in elderly patients with moderate or severe hypertension undergoing total knee arthroplasty surgery. Methods Eighty patients with moderate or severe hypertension, aged 63-80 years old, ASA Ⅱ or Ⅲ, NYHA Ⅰor Ⅱ, with preoperative Mini-Mental State Examination (MMSE) score≥23 scheduled for total knee arthroplasty surgery were enrolled in this study. The patients were randomly assigned to two groups with 40 patients per group: experience anesthesia group (group E) and BIS monitoring group (group B). The group B adjusted the depth of anesthesia according to intraoperative BIS value while experience anesthesia group anesthesia was adjusted according to traditional clinical signs and hemodynamic parameters. The hemodynamic parameters were recorded at time before anesthesia induction (T0), 3 min after induction (T1), at time before using tourniquet (T2), 30 min after tourniquet use (T3), before tourniquet release(T4) and after tourniquet release (T5). Observing the respiratory recovery time, eye opening time, extubation time, PACU residence time, the dosage of propofol, the dosage of vasoactive agent and the anesthesia related complication. POD was assessed within 3 d after operation using the confusion assessment method (CAM). Results The SBP at the time of T1, T2 in group E were (112±9) mmHg (1 mmHg=0.133 kPa) and (103±7) mmHg while those values in group B were (119±11) mmHg and (108±9) mmHg respectively. The DBP at the time of T1 in group E was (66±7) mmHg while value in group B was (72±10) mmHg. Compared with group E, the SBP at the time of T1, T2 and DBP at the time of T1 in group B were higher than those values in group E (all P<0.05). The dosage of propofol in group B [(322±49) mg] was lower than the dosage of group E[(366±52) mg]. The time of respiratory recovery [(4.3±1.5) min], time of eye opening [(5.7±1.4) min], extubation time [(10.5±2.5) min] and PACU residence time [(32±5) min] in group B were shorter than those values in group E[(5.6±2.1), (7.4±2.1), (12.1±2.5), (35±6) min]. Moreover, the overall incidence of POD in group B (20.0%) was significantly lower than that of group E (45.0%) (P<0.05) . Conclusions BIS monitoring reduces the amount of anesthetics used in elderly patients with moderate or severe hypertension undergoing total knee arthroplasty surgery. It leads to less incidence of POD three days after operation. Key words: Bispectral index; Depth of anesthesia; Aged; Hypertension; Total knee arthroplasty; Postoperative delirium