Tachycardia and hypertension due to surgical and tourniquet pain often occur suddenly during general anesthesia for total knee arthroplasty. We evaluated the dose-related effects of landiolol on an abrupt tachycardic response in this clinical setting, since this agent is able to suppress the cardiovascular responses associated with sympathetic stimulation.
After approval by the local ethical committee and informed consent, 114 patients, aged 51-89 yr, undergoing total knee arthroplasty under general anesthesia were enrolled in this study. Following general anesthesia induction with fentanyl 1-2 μg/kg, propofol 1.5-2 mg/kg and 5% sevoflurane, a laryngeal mask airway was inserted, and anesthesia was maintained with 1% sevoflurane, droperidol 5 mg and 50% N₂O in oxygen. Thereafter, supplemental fentanyl 0.5-1 μg/kg was injected repeatedly to keep the end-tidal CO₂ tension of 30-45 mmHg, and spontaneous respiratory rate of 10-25 breaths/min. When a tachycardic response(defined as heart rate of more than 90 beats/min for more than 3 minutes) was observed, landiolol or normal saline(as a time control group) was randomly infused continuously at a rate of 40 or 80 μg/kg/min, or of 0.24 mL/kg/h, respectively, until the end of surgery or tourniquet deflation. Hemodynamic and respiratory variables were recorded at 1-5 minute intervals. Data were analyzed by analysis of variance or Student's t-test with Bonferroni's correction for comparisons among groups or within each group, with p<0.05 being significant.
Tachycardic responses developed in 50 of 114 patients(44%) studied. There were no significant differences in demographic data among patients who received landiolol 40 μg/kg/min(n＝24), landiolol 80 μg/kg/min(n＝20), and saline(n＝6). Heart rate decreased at 1 minute after the start of landiolol infusion and remained below pre-administration values(p<0.05) in patients receiving landiolol 40 and 80 μg/kg/min, while heart rate unchanged in control patients. Mean blood pressure remained unchanged as compared with pre-infusion values in all groups. When compared with the control group, heart rate was lower 5 and 4 minutes after the start of landiolol infusion(p<0.05) in patients given landiolol of 40 and 80 μg/kg/min, respectively.
These data show that landiolol infusion at a rate of 80 μg/kg/min provided more rapid suppression of an abrupt tachycardia in patients undergoing total knee arthroplasty under general anesthesia. The prompt treatment of tachycardia by landiolol seems appropriate, particularly for the older patients who are likely to have occult ischemic heart disease.