A Comparison of the Effects of Isoflurane and Sevoflurane on Cardiovascular Parameters as Measured by Magnetic Resonance Imaging in Paediatric Patients with Congenital Heart Disease

Method: After approval from the Guy’s Hospital Research Ethics Committee and written informed parental consent, ten children, younger than 10 years scheduled to undergo cardiac MRI were randomized to receive either isoflurane or sevoflurane as ‘first agent’ and then crossed over to receive the other inhalational agent. Cardiovascular parameters at MAC = 1 for both agents were observed and evaluated. Prior to anaesthetic induction, standard monitoring was applied. Anaesthesia was induced with intravenous propofol 3-5 mg/kg followed by atracurium 0.5mg/kg to facilitate endotracheal intubation. Anaesthesia was initially maintained with either one of the inhalational agents. By a technique of ‘over pressure’, a MAC = 1 for the inhalational agent was achieved and cardiac measurements on the MRI carried out. The heart rate and blood pressure were also noted. The ‘first’ inhalational agent was subsequently crossed-over to the ‘second’ agent, MAC = 1 achieved followed by another set of cardiac measurement . The MRI scans for the studies were carried out usually 20 minutes after commencing the inhalational agent. The investigator performing the MRI measurements was blinded to the type of the anaesthetic agent in use. IPPV was carried out to maintain an EtCO2 of 4 – 4.5 kpa and peak airway pressures of 15 – 20 cm of water. An air:oxygen mixture was used to maintain FiO2 50% .All patients received Hartmans solution as maintenance fluid during the procedure Analyses of the scans were performed off line by a blinded investigator after the entire study had been completed. Results: Out of ten, six patients had sevoflurane as ‘first agent’ followed by isoflurane as the ‘second agent’. The remaining four patients had isoflurane as ‘first agent’ followed by sevoflurane as ‘second agent’. Overall, mean age was 37.1 months (SD 33.3, range 5 – 108)), mean weight 12.72 kg (SD 5.4, range 5.3 – 21.7) and mean height 87.4 cm (SD 20.1, range 61.5 – 123.6). The mean values of the mean arterial pressure (MAP), cardiac index(CI) and ejection fraction (EF) on a MAC = 1 of both isoflurane (iso) and sevoflurane (sevo) are as shown in the table below: Parameter Isoflurane