Isoflurane and intravenous anesthesia used for induction before coronary artery bypass grafting

Induction of anesthesia with isoflurane in combination with fentanyl, thiopentone, nitrous oxide and pancuronium was studied in nine patients scheduled for coronary artery bypass grafting. Ejection fraction (EF) of the left ventricle was monitored with a single crystal probe linked to a microcomputer, after injection of 200 MBq Tc 99m-HSA. Stroke volume index determined by thermodilution and EF were used to calculate left ventricular end-diastolic volume index (LVEDVI). The degree of ischemia was numerically scored as evaluated from the ECG (modified V5 lead). The study protocol covered seven periods from awake before induction to 5 min after intubation. EF decreased moderately during intubation (P less than 0.05). Systemic vascular resistance index (SVRI) was decreased (P less than 0.05) at all times except during intubation when it was unchanged compared to control. LVEDVI decreased during induction (P less than 0.05), while left ventricular filing pressure remained unchanged. Heart rate did not change. Systolic arterial pressure decreased from 147 mmHg (19.6 kPa) to about 100 mmHg (13.3 kPa) during induction (P less than 0.05). Two patients were given vasoconstrictors because of low arterial pressure. The mean ischemic score did not change. One patient, however, had signs of progressive ischemia. In this patient isoflurane administration was stopped after the last recording and the ECG normalized within 20 min.