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Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

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Although guidelines recommend the use of single-unit red blood cell (RBC) transfusions to minimize allogeneic blood exposure, clinical practice remains dominated by two-unit transfusions. This study assesses the potential impact of a single-unit transfusion policy on reducing RBC utilization. We performed a retrospective analysis of adult patients admitted to a tertiary care hospital who received one or two RBC units. In subjects transfused two units, the effect of one unit was estimated by dividing the change in haemoglobin by 2. The proportion of patients reaching a haemoglobin threshold of 70, 75, 80, 85 and 90 g L(-1) with a single RBC unit was estimated. Of 302 included patients, only 65 received a one-unit transfusion. Based on thresholds of > or = 90, > or = 80 and > or = 70 g L(-1), a single-unit transfusion would be sufficient in 42.0% (RRR = 0.54), 79.6% (RRR = 0.23) and 98.0% (RRR = 0.02) of cases, respectively. This corresponds to 0.21, 0.57 and 0.82 mean RBC units saved per patient. In the orthopaedic subpopulation, the mean RBC units saved are 0.53, 0.88 and 1.00 for the same haemoglobin targets. Adopting a policy of transfusing RBC in single-unit aliquots could significantly improve RBC utilization and decrease patient exposure to allogeneic blood.

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The effects of propofol on cerebrospinal fluid pressure, mean arterial pressure, cerebral perfusion pressure and heart rate were studied during induction, tracheal intubation and skin incision in 23 patients scheduled for elective craniotomy. Premedication consisted of midazolam 0.1 mg/kg intramuscularly and metoprolol 1 mg/kg orally. Measurements were made or derived at time zero and 0.5, 1, 1.5, 2 and 3 minutes after an induction dose of propofol 1.5 mg/kg. A continuous infusion of propofol was started at time zero at a rate of 100 mg/kg/minute. Fentanyl 2 micrograms/kg was added before tracheal intubation, application of the pin head holder and skin incision. Cerebrospinal fluid pressure and mean arterial pressure decreased significantly 2 minutes after propofol alone, by 32% and 10% respectively, while a cerebral perfusion pressure above 70 mmHg was maintained. Heart rate did not change. Propofol combined with moderate dose of fentanyl, obtunded the usual cerebrospinal fluid and arterial pressure responses to intubation and other noxious stimuli. Thus propofol seems to be a suitable intravenous anaesthetic agent for induction and maintenance in neuroanaesthesia.

Oxygen consumption (r carbon dioxide production ('(/C02). end-t~dat carbon dioxide partial pressure (PETC02), mixed venous oxygen saturation (S;'02) and haemodynamic variables were recorded every 30 rain for four hours in 1_5 patients recovering from hypothermic cardiopulmonary bypass (CPBFollowing hypothermic cardiopulmonary bypass (CPB), patients usually arrive in the Intensive Care Unit (ICU) with a nasopharyngeal temperature (NPT) of 34-36 ' C. t Sladen et al. showed that over the subsequent 8 hr patients rewarm to normothermia, with the maximal rate of rewarrning occurring 2-4 hr after admission to the ICU.2 During this period of very rapid rewarming, marked changes have been suggested in both metabolic rate and myocardial work) '4 Increases in 02 consumption (VO2) and carbon dioxide production ('i/CO2) are undesirable in post-CPB patients because they lead to increases in heart rate (HR), mean arterial pressure (MAP) and rate pressure product (RPP) s causing an increase in myocardial oxygen consumption.6 Moreover, if the extent of these metabolic changes is not recognized then both respiratory and metabolic acidosis may occur. The present study was designed to determine the extent of these metabolic changes and their haemodynamic consequences during the first four hours after CPB. We also wished to determine the effects of shivering on these variables, if these effects are significant and how best to follow their trend. MethodsFifteen patients scheduled for elective cardiac surgery were studied. Patients with symptomatic peripheral vas- CAN J ANAESTH 1988 ; 35:4 / pp332-7

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