Propofol-thiopentone admixture: recovery characteristics

We have investigated, in a prospective double-blind study, recovery from anaesthesia induced by two admixtures of propofol and thiopentone and compared it with a third group of patients who received propofol and lignocaine. Ninety unpremedicated ASA 1 or 2 patients scheduled for elective gynaecological laparoscopy as a daycase procedure were randomly allocated to receive one of three different mixtures for induction of anaesthesia as part of a standardized anaesthetic: Group P50: propofol 1% 10 ml/thiopentone 2.5% 10 ml, Group P75: propofol 1% 15 ml/thiopentone 2.5% 5 ml, Group P100: propofol 1% 20 ml/lignocaine 1% 4 ml. Recovery from anaesthesia was assessed for up to four hours post-induction by critical flicker fusion threshold and best post-box toy completion time. Comparison was made with preoperative baseline performance. There was no significant difference in postoperative recovery between the three groups with either assessment but no group returned to their mean preoperative performance levels within the first four hours post-induction. Nor was there any difference between the groups with respect to postoperative analgesia or anti-emetic administration. Utilizing the most sensitive end-point, a sample of nearly 1000 patients in each group would be required to confirm the observed difference with a power of 0.8 based on the data from this study. In comparison with lignocaine, the addition of thiopentone to propofol does not delay recovery from anaesthesia and does not increase postoperative analgesic or anti-emetic requirements.