British journal of anaesthesia
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We have evaluated the disposition of milrinone in seven patients with low cardiac output after elective cardiac surgery involving cardiopulmonary bypass. Patients received a loading dose of milrinone 50 micrograms kg-1 given over 10 min followed immediately by an infusion of 0.5 microgram kg-1 min-1, continued for a minimum of 5 h. ⋯ Concentrations greater than 100 ng ml-1 were produced in all patients within 2 min of starting the loading dose and were maintained for the duration of the infusion. Volume of distribution, clearance and terminal half-life were similar to those found in patients with chronic cardiac failure.
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We have tested a published algorithm for pharmacokinetic model controlled infusion of propofol to supplement 67% nitrous oxide for general anaesthesia in Chinese children aged 4-10 yr. Initially we studied 10 children undergoing minor procedures with spontaneous ventilation; mean duration of surgery was 38 min and mean propofol infusion rate 497 micrograms kg-1 min-1. The precision of the model was 24.8% and bias -18.5%. ⋯ The mean blood concentration required for satisfactory anaesthesia was 6.6 micrograms ml-1 (range 3-11 micrograms ml-1) and the mean blood concentration at the time of waking, which occurred 40 min after switching off the infusion, 0.86 microgram ml-1 (range 0.40-1.45 micrograms ml-1). Our patient population required different pharmacokinetic variables from those in the previous study. Recovery was slow because of the high infusion rates required to maintain satisfactory anaesthesia and large difference between the blood concentration required for anaesthesia and that at which waking occurred.
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We have assessed postoperative delirium in 24 patients undergoing thoracotomy for pulmonary malignancy throughout their stay in hospital. Arterial oxygen saturation was measured with a pulse oximeter on the night before operation and on the second night after operation. Five patients (21%) developed clinically significant postoperative delirium, and delirium occurred in all patients who had inadequate oxygenation. ⋯ When patients were delirious, the first treatment of choice was supplementary oxygen and all patients were treated successfully by this simple regimen. In two patients, supplementary treatment with zuclopenthixol 6 mg daily was necessary. We conclude that hypoxaemia may be a contributing factor in postoperative brain dysfunction, as postoperative delirium was associated with hypoxaemia and was treated successfully with supplementary oxygen.