Onset time and haemodynamic response after thiopental vs. propofol in the elderly: a randomized trial

BACKGROUND: The induction dose of hypnotic agents should be reduced in the elderly, but it is not well studied whether thiopental or propofol should be preferred in this group of patients. The aim of this study was to compare onset time, hypnosis level and the haemodynamic response after thiopental vs. propofol for induction of anaesthesia. Our primary hypothesis was that in the elderly, thiopental had a shorter onset time than propofol, defined as time to bispectral index (BIS) <50. METHODS: In this randomized and double-blinded study, we included 78 patients. Patients were eligible, if they were scheduled for elective surgery with general anaesthesia and aged 60 or older. Patients received alfentanil 10 μg/kg and either thiopental 2.5 mg/kg or propofol 1.0 mg/kg, and depth of anaesthesia was determined with BIS the following 120 s along with clinical assessment of anaesthetic depth. The primary endpoint was the time from start of injection of the hypnotic to a BIS value below 50. RESULTS: Time to BIS <50 was significantly shorter in patients receiving thiopental, where onset time was 52 s (median value) compared with 65 s in the propofol group (P=0.01). Mean arterial pressure decreased 25.6 mmHg in the propofol group and 15.6 mmHg in the thiopental group (P=0.003) within 120 s. Heart rate decreased 9.1 b.p.m. within 120 s in the patients receiving propofol compared with a decrease of 5.1 b.p.m. in patients receiving thiopental (P=0.04). CONCLUSION: Thiopental was found to have a faster onset than propofol in elderly surgical patients.