Purpose: Decreased cardiac chronotropic response in elderly patients along with concomitant ss-blockade may suppress the autonomic responsiveness to surgical stimulation and subsequently obscure episodes of "light anesthesia".
Methods: We analyzed post hoc computerized data from our previous study evaluating the effects of perioperative atenolol administration. Bispectral index (BIS) and the performance of routine anesthetic depth indicators were analyzed in 45 patients undergoing abdominal surgery: Group I (n = 12), isoflurane/fentanyl/nitrous oxide in oxygen anesthesia; Group II (n = 16), isoflurane/fentanyl/nitrous oxide in oxygen with 10 mg atenolol intravenously prior to anesthesia; Group III (n = 17), isoflurane/fentanyl/nitrous oxide in oxygen with a maximum end-tidal isoflurane concentration of 0.4 vol.% and incremental doses of atenolol (5 mg intravenously stepwise). In all groups, blood pressure (BP) was maintained within +/- 20% of preoperatively defined baseline BP and heart rate (HR) between 50-80 beats x min(-1). BP, HR, and end-tidal isoflurane were tested for their potential to predict BIS using a previously described statistical model (P(K)).
Results: Although Group III patients received on average 39.5% less isoflurane compared with Group I patients (P = 0.006), and Groups II and III patients received on average 21% less fentanyl compared with Group I patients (P </= 0.002), similar levels of intraoperative average BIS values (53-54) were obtained for all groups. Higher BIS values were reached at emergence in atenolol-treated patients. The performance of hemodynamic variables or end-tidal isoflurane to predict BIS was moderate even at critical intraoperative events, but unaffected by atenolol.
Conclusion: Atenolol reduces anesthetic requirements but may not modify anesthetic depth indicators in elderly patients.