An evaluation of the perioperative efficacy of selective β1-blockade in coronary surgery:Studies with a Late Preoperative Dose of Metoprolol

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Abstract
The plasma concentration of metoprolol was measured hourly following an oral dose on two consecutive days—the day before, and the day of, coronary surgery. No significant difference was found between the two sampling days, though there was a tendency to lower concentrations during and after extracorporeal circulation. After a median dose of 50 mg the peak concentration (reached on average after 1.5 h) was 545±70 nmol/l on the first day and 388±57 on the day of surgery. The respective elimination rates from plasma, expressed as half-life, were 3.4±0.21 and 3.5±0.19 hours (NS). On the day of surgery the heart rate rose during the second half of the observation period, peaking above 130 beats/min. Heart rate was inversely correlated to metoprolol concentration in plasma with coefficient -0.68 before induction of anesthesia and -0.77 two hours after termination of extracorporeal circulation. The perioperative efficacy of β-blockade following a late preoperative oral dose of the agent thus appeared to be reduced and inadequate.