Alphaxalone-alphadolone (Althesin), when diluted and administered as a controlled infusion, was used as a sedative for 30 patients in an intensive therapy unit. This technique allowed rapid and accurate control of the level of sedation. It had three particularly useful applications: it provided "light sleep," allowed rapid variation in the level of sedation, and enabled repeated assessment of the central nervous system. Sedation was satisfactory for 86% of the total time, and no serious complications were attributed to the use of the drug. Furthermore, though alphaxalone-alphadolone was given for periods up to 20 days there was no evidence of tachyphylaxis or delay in recovery time. The study involved 30 patients who required controlled sedation. They were all being treated in the intensive therapy unit, where continuous monitoring of vital signs could be undertaken by nurses at the bedside. The only patients excluded were those with gross hepatic failure. The technique involved a separate infusion containing alphaxalone-alphadolone, with a burette included in the infusion set and 5 ml of the drug added to 25 ml of 5% dextrose. The maximum dose of alphaxalone-alphadolone that could be given was thus 5 ml. The infusion rate was controlled by an Ivac infusion pump. Occasionally, 2 ml undiluted alphaxalone-alphadolone was given to gain initial control in very restless patients. Six levels of sedation were formulated; three with the patient awake and three with the patient asleep. The mean time spent under sedation was 93 hours (range 1·5-480 hours). One patient was continuously sedated for 20 days. The quality of sedation was determined by comparing the overall period of acceptable sedation—between levels 2 and 5—with the total infusion period. Sedation was satisfactory for 2,425 hours out of a possible total of 2,803 hours (86·5%). The mean time taken to sedate adequately the patients was 9 minutes. The mean time taken for recovery from alphaxalone-alphadolone was 12 minutes. There were no statistically significant changes in blood pressure or central venous pressure when the patients were sedated with alphaxalone-alphadolone. The initial rise in heart rate was significant. There was no clinical evidence to suggest that alphaxalone-alphadolone depressed ventilation. No side effects were sufficiently serious to justify stopping the drug. There were no complications at the site of infusion and no evidence of inflammation or phlebitis. Alphaxalone-alphadolone sedation has three particularly useful applications. Firstly, it provides light sleep. Secondly, it provides rapid variation in the level of sedation. Thirdly, it allows repeated assessment of the central nervous system. AlphAlphaxalone-alphadolone (Althesin), when diluted and administered as a controlled infusion, was used as a sedative for 30 patients in an intensive therapy unit. This technique allowed rapid and accurate control of the level of sedation. It had three particularly useful applications: it provided "light sleep," allowed rapid variation in the level of sedation, and enabled repeated assessment of the central nervous system. Sedation was satisfactory for 86% of the total time, and no serious complications were attributed to the use of the drug. Furthermore, though alphaxalone-alphadolone was given for periods up to 20 days there was no evidence of tachyphylaxis or delay in recovery time. The study involved 30 patients who required controlled sedation. They were all being treated in the intensive therapy unit, where continuous monitoring of vital signs could be undertaken by nurses at the bedside. The only patients excluded were those with gross hepatic failure. The technique involved a separate infusion containing alphaxalone-alphadolone, with a burette included in the infusion set and 5 ml of the drug added to 25 ml of 5% dextrose. The maximum dose of alphaxalone-alphadolone that could be given was thus 5 ml. The infusion rate was controlled by an Ivac infusion pump. Occasionally, 2 ml undiluted alphaxalone-alphadolone was given to gain initial control in very restless patients. Six levels of sedation were formulated; three with the patient awake and three with the patient asleep. The mean time spent under sedation was 93 hours (range 1·5-480 hours). One patient was continuously sedated for 20 days. The quality of sedation was determined by comparing the overall period of acceptable sedation—between levels 2 and 5—with the total infusion period. Sedation was satisfactory for 2,425 hours out of a possible total of 2,803 hours (86·5%). The mean time taken to sedate adequately the patients was 9 minutes. The mean time taken for recovery from alphaxalone-alphadolone was 12 minutes. There were no statistically significant changes in blood pressure or central venous pressure when the patients were sedated with alphaxalone-alphadolone. The initial rise in heart rate was significant. There was no clinical evidence to suggest that alphaxalone-alphadolone depressed ventilation. No side effects were sufficiently serious to justify stopping the drug. There were no complications at the site of infusion and no evidence of inflammation or phlebitis. Alphaxalone-alphadolone sedation has three particularly useful applications. Firstly, it provides light sleep. Secondly, it provides rapid variation in the level of sedation. Thirdly, it allows repeated assessment of the central nervous system. Alph