Midazolam as Adjunct to High‐Dose Fentanyl Anaesthesia for Coronary Artery Bypass Grafting Operation

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Abstract
The usefulness of midazolam as an adjunct during high-dose fentanyl anesthesia was studied by following the changes in the hemodynamics and total body oxygenation after an i.v. injection of 0.075 mg/kg and 0.15 mg/kg of midazolam during the induction of fentanyl (75 .mu.g/kg)-O2 anesthesia for a coronary artery bypass operation. These responses were then compared to the changes seen in patients receiving the same fentanyl anesthesia without the midazolam. A rapid decline after the midazolam injection was seen in the mean systemic arterial pressure (24-32%), the lowest individual value was 45 mm Hg (6.0 kPa [kiloposcal]) and in the systolic and diastolic pulmonary arterial pressures (29-33% and 30-31%) in 1-3 min. As measured 10 min after the midazolam injection, a decrease from the baseline was seen in the stroke index (25-30%), in the left ventricular stroke work index (46-42%) and in the right ventricular stroke work index (48-61%). These hemodynamic variables remained on a lower level throughout the study period (40 min) in the midazolam patients as compared to the controls. The tissue oxygenation seemed to be sufficient in all groups during the study period. An i.v. injection of a relatively low dose of midazolam during the induction of high-dose fentanyl anesthesia seems to be followed by rapidly increased venous pooling and a moderately to severely decreased systemic arterial pressure. Midazolam cannot be recommended as an adjunct during high-dose fentanyl anesthesia.