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The clinically acceptable limit of acute normovolemic, normothermic hemodilution, a standard procedure in scoliosis surgery, is not yet well defined. Eight ASA class I patients undergoing idiopathic scoliosis correction were administered a standard anesthetic with 100% oxygen and controlled ventilation. Hemodilution was accomplished by exchanging whole blood for 5% albumin in 0.9% saline. Blood gases, acid-base status, and circulatory variables were recorded prior to and after hemodilution, and every 30 min throughout surgery. The impact of hemodilution was judged by mixed venous oxygen saturation which was maintained at > or = 60%, while intravascular volume was maintained with the 5% albumin solution. Reinfusion of the autologous blood was completed by the end of surgery. In the eight controlled cases in which normovolemic hemodilution was studied, hemoglobin levels decreased from 10.0 +/- 1.6 g/dL to 3.0 +/- 0.8 g/dL. Mixed venous oxygen saturation decreased from 90.8% +/- 5.4% to 72.3% +/- 7.8%. Oxygen extraction ratio increased from 17.3% +/- 6.2% to 44.4% +/- 5.9%. Oxygen delivery decreased from 532.1 +/- 138.1 mL.min-1.m-2 to 260.2 +/- 57.1 mL.min-1.m-2, while global oxygen consumption did not decrease and plasma lactate did not appreciably increase. Central venous pressure increased and peripheral resistance decreased during hemodilution. Cardiac index increased, heart rate remained essentially constant, and left ventricular stroke work index did not decrease significantly. No patients suffered clinically adverse outcomes. Global oxygen transport and myocardial work can be maintained at extreme normovolemic anemia. Our evidence suggests that stages of normovolemic hemodilution more severe than previously reported may be clinically acceptable for young, healthy patients during normocarbic anesthesia.

We compared the hemodynamic response to laryngoscopy and intubation, as well as emergence and recovery times, when propofol or thiopental were used for rapid intravenous induction of anesthesia in 59 infants undergoing repair of inguinal hernia. An intravenous catheter was inserted under N2O analgesia and atropine 0.01 mg/kg was administered to all patients. Subsequent induction with propofol (3 mg/kg), thiopental (5 mg/kg), or halothane (2%) was followed with succinylcholine (2 mg/kg) and tracheal intubation. Ventilation was manually assisted during surgery, and tracheas were extubated when patients were completely awake. Infants who received propofol showed less hypertensive response to intubation than those who received thiopental or halothane. In the 1- to 6-mo age group, emergence (extubation) time was significantly longer for infants who received thiopental (10.2 +/- 1.4 min) than for those who received propofol or halothane (5.5 +/- 2.5 and 6.2 +/- 1.3 min, respectively). Infants who received thiopental induction had a higher incidence of perioperative airway complications than all others. There was no significant difference in the recovery and discharge times among the three groups. We conclude that when rapid intravenous induction is required for infants, propofol is more effective than thiopental in obtunding the hypertensive response to intubation, and in young infants (1-6 mo) it results in more prompt emergence after short surgical procedures.