[Hyperchloremic acidosis druing plasma volume replacement]. / Acidose hyperchlorémique lors du remplissage vasculaire.

OBJECTIVES: Review of the physiological and clinical consequences of hyperchloraemic acidosis observed during plasma volume replacement using crystalloids and colloids. DATA SOURCES: Data were searched in the Medline database after 1990 using the following key words: metabolic acidosis, crystalloids, colloids, albumin, gelatin, hydroxyethyl starch. DATA EXTRACTION: Publications before 1990 were selected for their historical value. Most of articles published after 1990 and all types including case report were accepted. DATA SYNTHESIS: Large volume infusion of isotonic solution can cause hyperchloraemic acidosis. Colloid plasma substitutes using saline solvent may be responsible for the same kind of acidosis with acidaemia. The anion gap is not modified in this case because of chloride increase. Physiological mechanism may be described using the Henderson-Hasselbach equation or the strong ion difference decrease (Stewart concept). Excessive chloride infusion is a major factor in this acid-base disorder and the term hyperchloraemic acidosis should be preferred to dilutional acidosis. When perioperative acidosis occurs, careful and complete analysis of acid-base disturbance should be made. The association of a normal anion gap, normal lactatemia, hyperchloraemia and acidaemia does not need specific treatment. Acidosis corrects spontaneously and slowly following chloride normalization. But any factor that may increase acidosis should be avoided. CONCLUSION: The use of balanced solution like lactated-Ringer solution instead of isotonic saline solution for fluid resuscitation, except for specific contra-indication as intracranial hypertension, may avoid hyperchloraemic acidosis. Potential risk of this acidosis led to the conception of a new colloid using balanced crystalloids solution as the solvent (Hextend).

A study of platelet functions with a new analyzer using high shear stress (PFA 100) in patients undergoing coronary artery bypass graft.

Platelet dysfunction can be a major factor in excessive bleeding following cardiopulmonary bypass (CBP). A rapid, specific and sensitive method to identify platelet dysfunction would be a useful tool for identifying patients at an increased risk of bleeding. The ability of PFA100, an in vitro bleeding test, to predict increased bleeding risk linked to platelet dysfunction was tested in 146 patients undergoing primary coronary artery bypass graft. Blood samples were taken the day before surgery, and 15 min and 5 h after heparin neutralization. The preoperative closure times (CT), i.e. the time required for platelets in citrated whole blood to occlude an aperture cut into a membrane coated with collagen plus either epinephrine (CTEPI) or adenosine diphosphate (CTADP) were longer in blood-group-O patients than in patients with other groups. The 15 min postoperative values were significantly longer from preoperative values essentially owing to CBP-induced hemodilution. Interestingly, 5 h after CBP, a significant reduction in CT values probably reflected platelet hyperaggregability. No correlation was found between calculated blood loss (CBL) and either preoperative or postoperative PFA values.

Continuous infusion of remifentanil and target-controlled infusion of propofol for patients undergoing cardiac surgery: a new approach for scheduled early extubation.

OBJECTIVE: To assess hemodynamic stability, postoperative pain management, and the control and timing of early extubation of a total intravenous anesthetic technique using propofol target-controlled infusion (TCI) and remifentanil in cardiac surgery. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Fifty patients scheduled for elective cardiac surgery. INTERVENTIONS: Premedication consisted of oral midazolam, 0.1 mg/kg. Anesthesia was induced with propofol TCI at a target concentration of 1.5 to 2 microg/mL; remifentanil, 1 microg/kg; and rocuronium. Anesthesia was maintained with propofol at the same target concentration and remifentanil titrated between 0.25 and 1 microg/kg/min. Thirty minutes before the end of surgery, a 0.1-mg/kg bolus of morphine was administered intravenously. Postoperative sedation was achieved by maintaining the propofol infusion until the patient was deemed ready for extubation. Postoperative pain relief was evaluated using a visual analog scale. The intervals between arrival in the intensive care unit, spontaneous ventilation, and extubation were recorded. MEASUREMENTS AND MAIN RESULTS: Included in this study were 36 men and 14 women (American Society of Anesthesiologist = III; New York Heart Association = II) scheduled for cardiac surgery. All patients remained hemodynamically stable throughout the perioperative period. Thirty-seven patients were successfully extubated during the first 4 postoperative hours. Spontaneous breathing was achieved at a mean interval of 15+/-5 minutes after propofol discontinuation. The mean interval to extubation was 163+/-45 minutes after arrival in the intensive care unit. Extubation was performed 48+/-12 minutes after patients were considered ready to awaken. During spontaneous ventilation, 36 patients received additional boluses of morphine (mean, 2.5+/-1 mg). Subsequently, all patients achieved a visual analog scale less than 40 mm. CONCLUSION: The combination of remifentanil and propofol TCI resulted in hemodynamic stability and good postoperative analgesia. This technique allows physicians to schedule the time of extubation in patients undergoing cardiac anesthesia.

Randomized trial of diaspirin cross-linked hemoglobin solution as an alternative to blood transfusion after cardiac surgery. The DCLHb Cardiac Surgery Trial Collaborative Group.

BACKGROUND: Risks associated with transfusion of allogeneic blood have prompted development of methods to avoid or reduce blood transfusions. New oxygen-carrying compounds such as diaspirin cross-linked hemoglobin (DCLHb) could enable more patients to avoid allogeneic blood transfusion. METHODS: The efficacy, safety, hemodynamic effects, and plasma persistence of DCLHb were investigated in a randomized, active-control, single-blind, multicenter study in post-cardiac bypass surgery patients. Of 1,956 screened patients, 209 were determined to require a blood transfusion and met the inclusion criteria during the 24-h post-cardiac bypass period. These patients were randomized to receive up to three 250-ml infusions of DCLHb (n = 104) or three units of packed erythrocytes (pRBCs; n = 105). Further transfusions of pRBCs or whole blood were permitted, if indicated. Primary efficacy end points were the avoidance of blood transfusion through hospital discharge or 7 days postsurgery, whichever came first, and a reduction in the number of units of pRBCs transfused during this same time period. Various laboratory, physiologic, and hemodynamic parameters were monitored to define the safety and pharmacologic effect of DCLHb in this patient population. RESULTS: During the period from the end of cardiopulmonary bypass surgery through postoperative day 7 or hospital discharge, 20 of 104 (19%) DCLHb recipients did not receive a transfusion of pRBCs compared with 100% of control patients (P < 0.05). The overall number of pRBCs administered during the 7-day postoperative period was not significantly different. Mortality was similar between the DCLHb (6 of 104 patients) and the control (8 of 105 patients) groups. Hypertension, jaundice/hyperbilirubinemia, increased serum glutamic oxalo-acetic transaminase, abnormal urine, and hematuria were reported more frequently in the DCLHb group, and there was one case of renal failure in each group. The hemodynamic effects of DCLHb included a consistent and slightly greater increase in systemic and pulmonary vascular resistance with associated increases in systemic and pulmonary arterial pressures compared with pRBC. Cardiac output values decreased more in the DCLHb group patients after the first administration than the control group patients. At 24 h postinfusion, the plasma hemoglobin level was less than one half the maximal level for any amount of DCLHb infused. CONCLUSIONS: Administration of DCLHb allowed a significant number (19%) of cardiac surgery patients to avoid exposure to erythrocytes postoperatively.

Does aprotinin modify the effects of ischaemia-reperfusion on the myocardial performance of a blood perfused isolated rabbit heart?

Aprotinin has been reported to influence positively or negatively the process of ischaemia-reperfusion. However, it is a complex drug acting on platelets, neutrophils and coagulation, which may also have a direct effect by inhibiting intracellular proteases and free radical generation. The goal of this study was to determine the direct effects of aprotinin on the myocardial performances of an isolated blood perfused rabbit heart preparation after normothermic global ischaemia. Two groups of 10 hearts were studied. The control group (ischaemia) underwent 30 min of global normothermic ischaemia. In the aprotinin group, (aprotinin) 200 KUI mL-1 of aprotinin was added to the perfusate before ischaemia. Measurements were obtained at base-line, 10, 30 and 60 min after reperfusion. Normothermic ischaemia significantly decreased myocardial performance in both groups. After 60 min reperfusion, myocardial contractility significantly recovered in the aprotinin group compared with the ischaemia group. Aprotinin contributes significantly by limiting the consequences of ischaemia on myocardial performances. This effect may be due to a direct action of the drug because leucocytes and plasma proteins were removed in this preparation.

Comparison of the acute hemodynamic effects of hypertonic or colloid infusions immediately after mitral valve repair.

OBJECTIVE: To determine the acute hemodynamic effect of hypertonic saline and/or colloid solutions as volume resuscitation in postoperative mitral valve repair patients. DESIGN: Prospective, randomized trial. SETTING: Postoperative cardiac intensive care unit of Broussais Hospital. PATIENTS: Twenty-six patients who underwent mitral valve repair were prospectively studied. Two patients were excluded during the study. INTERVENTIONS: During the immediate postoperative period, when wedge pressure decreases to <8 mm Hg, patients were randomly assigned to receive 250 mL of either hypertonic saline 7.2%-hydroxyethyl starch 6% (molecular weight, 200,000; hydroxyethylation ratio, 0.5) solution (HS-HES group), hypertonic saline 7.2% solution (HS group), or hydroxyethyl starch 6% solution (HES group). The infusion was completed within 15 mins. No additional volume was infused throughout the study. MEASUREMENTS AND MAIN RESULTS: Standard hemodynamic measurements and echocardiographic data demonstrated that HS-HES and HS induced a higher increase in left ventricular end-diastolic area than HES. In the HS-HES and HS groups, systemic vascular resistances decreased significantly and end-systolic area tended to decrease. In the HES group, systemic vascular resistances did not change and end-systolic area tended to increase. Accordingly, ejection fraction increased significantly by 21% and 18% with HS-HES (from 50.5 +/- 5.5 to 61.2 +/- 4.8) and HS (from 49.7 +/- 3.6 to 58.8 +/- 3.3), respectively, and did not change with HES. A major increase in cardiac index was observed after hypertonic solutions infusion, from 2.9 +/- 0.3 to 4.1 +/- 0.4 L/min/m2 in the HS-HES group and from 2.7 +/- 0.3 to 3.8 +/- 0.4 L/min/m2 in the HS group. Then, cardiac index progressively returned to baseline values within the 3 hrs after the infusion. No significant difference was observed between HS-HES and HS. In these groups, plasma sodium increased significantly after the infusion and remained higher than baseline values throughout the study. Adverse events were observed only with hypertonic solution administration: hypotensive episodes, sudden increases in pulmonary capillary wedge pressure, and ventricular arrhythmias. These side effects are likely attributable to a too-high dose and/or rate of infusion. All patients included in the study were discharged from the hospital before the 10th postoperative day. CONCLUSION: We conclude that in patients who have undergone mitral valve repair, postoperative infusion of hypertonic saline solutions increases left ventricular preload and left ventricular ejection fraction. The use of these hypertonic solutions may be of interest in patients with valvular cardiomyopathy. A titrated dose and a low rate of infusion may substantially improve the safety.

An international view of hydroxyethyl starches.

Hydroxyethyl starch (HES) is one of the most frequently used plasma substitutes. A variety of different HES solutions exist worldwide, which differ greatly in their pharmacological properties. HES is classified according to its manufactured or in vitro molecular weight (MW) into high MW (450-480 kDa), medium MW (200 kDa), and low MW (70 kDa) starch preparations. However, this is not sufficient, because as HES is metabolized in vivo, its MW changes, and it is the in vivo MW which is responsible for the therapeutic and adverse effects of each HES. The rate of metabolization depends mainly on the degree of hydroxyethyl substitution (ranging from 0.4 to 0.7), and the C2/C6 ratio of hydroxyethylation. A high degree of substitution and a high C2/C6 ratio lead to a slow metabolization of HES, resulting in a large in vivo MW. Slowly degradable high MW HES 450/0.7 and medium MW HES 200/0.62 have a high in vivo MW and are eliminated slowly via the kidneys. As a result, these starches have a relatively long-lasting volume effect. When infusing higher volumes (>1500 ml) are infused, large molecules accumulate in the plasma. This can result in bleeding complications due to decreased factor VIII/von Willebrand factor, platelet function defects, incorporation into fibrin clots, and an unfavorable effect on rheological parameters. Rapidly degradable medium MW HES 200/0.5 or low MW HES 70/0.5 are quickly split in vivo into smaller, more favorable molecule sizes, resulting in faster renal elimination, shorter volume effect, and fewer adverse effects on coagulation and rheological parameters. For historical and marketing reasons, only slowly degradable, high MW HES (480/0.7) is available in the United States. In Europe, a large variety of HES solutions are available, dominated by medium MW, easily degradable HES (200/0.5). Because of increasing international competition and the availability of newly developed starches, it is important to be aware of the pharmacological properties of HES and the advantages and disadvantages of the individual preparations.

Continuous infusion versus bolus administration of sufentanil and midazolam for mitral valve surgery.

OBJECTIVE: In the present study, the authors compared continuous infusion to bolus administration of sufentanil and midazolam in patients undergoing mitral valve surgery. The purpose of the study was to evaluate the hemodynamic variability, total dose, effective plasma drug concentrations, and simplicity of the two anesthetic techniques. DESIGN: Prospective, randomized study. SETTING: University hospital. PARTICIPANTS: Thirty patients scheduled for elective mitral valve surgery. INTERVENTIONS: Induction of anesthesia was similar in both groups and consisted of sufentanil, up to 2 microg/kg, and midazolam, 0.05 to 0.15 mg/kg, followed by atracurium, 0.5 mg/kg. Anesthesia was maintained in the bolus group with predetermined boluses of sufentanil, 2 microg/kg, and midazolam, 0.03 mg/kg. Boluses were not administered if blood pressure was within 20% of baseline. The continuous-infusion group received sufentanil, 3.6 microg/kg/h, and midazolam, 0.08 mg/kg/h, started immediately after induction. The infusion rate was reduced to sufentanil, 1.8 microg/kg/h, and midazolam, 0.04 mg/kg/h, after sternotomy and was discontinued at skin closure. Atracurium was infused at a rate of 0.5 mg/kg/h up to sternal closure in both groups. No inhalation agents were used. MEASUREMENTS AND MAIN RESULTS: Hemodynamic variability between the groups was not significant. Total sufentanil dose was 773 +/- 186 microg in the continuous-infusion group and 610 +/- 184 microg in the bolus group (p = 0.01). Total midazolam dose was 14.4 +/- 3 mg and 11.2 +/- 3 mg in the continuous-infusion and bolus groups, respectively. There were 3.46 (range, 0 to 7) additional bolus injections in the bolus group and 0.31 (range, 0 to 1) in the continuous-infusion group (p < 0.001). Plasma sufentanil concentrations at extubation were similar in both groups (0.5 ng/mL). Plasma midazolam concentrations at extubation in the bolus group (17 +/- 6.7 ng/mL) were similar to those in the continuous-infusion group (23 +/- 5 ng/mL). CONCLUSION: The simplicity of the continuous infusion is a major advantage. This technique provides hemodynamically safe and stable conditions similar to those of bolus administration.

Blood substitutes. Haemoglobin therapeutics in clinical practice.

Early approaches to the development of oxygen carriers involved the use of stroma-free hemoglobin solutions. These solutions did not require blood typing or crossmatching and could be stored for long periods. In addition, a variety of methods have been developed in chemically modifying and stabilizing the hemoglobin molecule. Several hemoglobin therapeutics are now in clinical trials as temporary alternatives to blood or as therapeutic agents for ischemia. The various hemoglobin products under development are derived from three principal sources: human, bovine and genetically engineered hemoglobin. Diaspirin cross-linked hemoglobin (DCLHb), administered at doses ranging from approximately 20-1000 ml, has been investigated in a number of clinical trials in patients undergoing orthopedic, abdominal aortic repair, major abdominal surgery, cardiac surgery and in critically ill patients with septic shock. In several studies, DCLHb was effective in avoiding the transfusion. However, Baxter Healthcare Corporation (Chicago, Illinois, USA) stopped the development of DCLHb after two unsuccessful trials in trauma patients. Bovine polymerized hemoglobin has also been extensively studied. Several phase II and phase III trials have been performed with this product in hemorrhagic surgery, cardiac surgery and vascular surgery, but data have not yet been published. Hemoglobin therapeutics could provide an important new option as an alternative to blood transfusion. Furthermore, they may be able to provide an immediate on-site replacement for traumatic blood loss, prevent global ischemia and organ failure, treat focal ischemia, and provide effective hemodynamic support for septic shock-induced hypotension.

[Dynamic left intraventricular obstruction after reconstructive mitral valve surgery]. / Obstruction dynamique intraventriculaire gauche après chirurgie réparatrice valvulaire mitrale.

A 71-years-old patient, undergoing mitral valve repair for degenerative valvulopathy and correction of pectus excavatus experienced a cardiogenic shock after weaning from cardiopulmonary bypass. The shock occurred after calcium chloride administration and was unresponsive to inotropic drugs. Transoesophageal echocardiography showed left ventricular outflow tract obstruction due to systolic anterior motion (SAM) of the mitral valve. Discontinuation of inotropic drugs and volume expansion restored the haemodynamic status. By its haemodynamic effects calcium chloride can cause left ventricular outflow tract obstruction, recognized by transoesophageal echocardiography.

[A new hydroxyethyl starch for volume replacement: Elohes 6%]. / Un nuevo hidroxietilalmidón para la reposición volémica: el Elohes 6%.

Various consensus groups convened in recent years to discuss plasma volume expansion solutions have suggested limiting the use of human albumin because of its high cost and have favored synthetic crystalloids or colloids for most clinical settings. Dextrans are colloids that are not widely used in most Europeans countries. Gelatins, in spite of the fact that unlimited amounts can be used, produce only moderate volume expansion and can trigger allergic reactions. The availability in Spain of hydroxyethylstarches (HES), a new type of colloid, may significantly change volume replacement strategy. HES are modified natural polymers. Three types, with different initial molecular weights, are used in Europe: high molecular weight HES, whose use in increasingly rare; low molecular weight HES (Expafusin), whose effect is short-lived; and medium molecular weight HES (Elohes, Fresenius-Laboratories Mein), which have recently been registered in Spain. Studies have shown that Elohes 6% (6% HES 200/0.62) provides volume expansion comparable to that of human albumin in clinical settings (cardiac surgery, shock, burns, etc.). The side effects of HES are usually minor. The frequency of anaphylactoid reactions is low, similar to that associated with human albumin. The effects on coagulation depend on molecular weight and duration of HES administration. Only in studies of hemodilution lasting 10 days with 6% HES 200/0.62 has VIII/von Willebrand complex been shown to decrease. If the recommended daily dose of this HES is respected, however, coagulation disorders are minimal. The effect of HES on kidney function is at present a subject of controversy. Thus, thanks to its prolonged effect on volume and few side effects, medium molecular weight HES colloids are the ones most often recommended for use in anesthesia and postoperative intensive care.

[Hydroxethyl starch: effects on hemostasis]. / Hydroxyéthylamidons: effets sur l'hémostase.

HES are high-polymeric glucose compounds obtained via hydrolysis and subsequent hydroxyethylation from the highly-branched amylopectin contained in maize. Initially, the HES were only characterized by their in vitro molecular weight (Mw), without consideration of the in vivo hydrolysis by alpha-amylase. The degree of substitution and the molar substitution ratio quantify the hydroxyethylation. The glucose units can be substituted at carbon 2, 3 and 6 leading to various substitution patterns. This pattern is described with the C2/C6 hydroxyethylation ratio. The higher the degree of substitution and the C2/C6 ratio, the less the starch is metabolized. The in vitro Mw, the degree of substitution and the C2/C6 ratio are the main determinants of the in vivo Mw which is clinically relevant. Haemorrhagic complications that occur after infusing larger volumes of HES can be avoided with a starch of low in vivo Mw. This is not only due to a lesser effect on the coagulation system which prevents an acquired type I von Willebrand syndrome, but also to a smaller decrease in platelet volume, since platelet volume and platelet function are positively correlated. In addition, HES with low in vivo Mw has significantly better rheological effects than HES with a high in vivo Mw, as high Mw macromolecules affect plasma viscosity negatively. Furthermore high Mw HES macromolecules lead to a distinctive decrease in fibronectin concentration that reflects saturation of the reticuloendothelial system. Another advantage of low in vivo Mw HES is its rather short half-life. Patients with an increased bleeding risk, microcirculatory disturbance or affected RES should receive HES with low in vivo Mw. In the future, HES should be mainly characterized by the in vivo and not the in vitro Mw.

Comparative study of different biological glues in an experimental model of surgical bleeding in anesthetized rats: platelet-rich and -poor plasma-based glue with and without aprotinin versus commercial fibrinogen-based glue.

The use of fibrin glue in cardiovascular surgery has been associated with decreased operative time, effective control of localized bleeding, and reduced postoperative blood loss. All preparations of fibrin glue mimic the final common pathway of the coagulation cascade in which fibrinogen is converted to fibrin in the presence of thrombin and calcium. The goal of the study was to compare five different types of fibrin glue, with or without aprotinin, on a surgical bleeding model in the rat. In 70 anesthetized Wistar rats, after laparotomy, a 3 cm liver incision was performed. After randomization, seven groups were studied. In the first group, Biocol was used as a pinpoint application to the bleeding site. Four groups received a fibrin glue obtained from a single human donor plasma using Cell Saver V (Haemonetics). The sealant was applied as a two-component system. The first component of the glue was either platelet-rich-plasma (PRP) or platelet-poor-plasma (PPP). The second component consisted of a mixture of 0.5 ml CaCl 10% with 1000 U of human thrombin, with or without 400KUI of aprotinin (AP). The last two groups, control and aprotinin were treated using saline solution or topical aprotinin respectively. Hemoglobin and hematocrit were measured before surgery and 30 min after application of the glue. The decrease in hemoglobin (Hb) and hematocrit (Hct) was the primary efficacy variable. Before surgery, there was no difference regarding Hb and Hct values between groups. Thirty min after the application of the glue, the decrease in hemoglobin expressed as percent of the control values is only significantly lower in the Biocol group when compared to control. No significant difference was observed with the other groups in comparison to control. The commercial fibrin glue (Biocol) is more efficient than other preparations. This efficacy is likely due to a higher fibrinogen concentration.

[Assessment of cardiovascular perioperative risk in non-cardiac surgery]. / Evaluation du risque cardiovasculaire périopératoire en chirurgie non cardiaque.

Patients with cardiovascular disease undergoing non cardiac surgery are exposed to three cardiac risks: myocardial infarction, heart failure and death. To estimate cardiac risk, clinical predictors of perioperative cardiovascular risk are classified as major, intermediate and minor and non cardiac surgery is stratified in high risk (greater than 5%), intermediate (from 1 to 5%), minor (lower than 1%) procedures. Efficient perioperative assessment of cardiac patients is obtained by teamwork and usually, indications for further cardiac investigations are the same as those in the nonoperative setting. An simplified algorithm, easier to use than original algorithm given in the guidelines of the American college of cardiology and the American heart association, may be helpful for the indication of further investigations. Five questions must be answered before using algorithm: is it an emergency surgical procedure?, was a coronary revascularization required in the past five years? has the patient had a coronary evaluation in the past two years?, are there identified clinical predictors of cardiac risk?, is it major or minor surgery? Three tests evaluate the preoperative cardiac risk: exercise testing, dipyridamole thallium scintigraphy, dobutamine stress echocardiography. Their accuracy is similar, their negative predictive value is high, their positive predictive value is low. These guidelines may be helpful to indicate further cardiac investigations which will have an impact on patient's treatment, monitoring during or after surgery and outcome.

Early extubation after mitral valve surgery: a target-controlled infusion of propofol and low-dose sufentanil.

OBJECTIVE: In the current study, the use of a target-controlled infusion of low-dose propofol was combined with a continuous infusion of sufentanil for patients undergoing mitral valve surgery. The purpose of the study was to evaluate the hemodynamic stability, the time to awakening and spontaneous ventilation, and the feasibility in an early extubation setting of a total intravenous anesthetic technique. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Fifteen patients scheduled for elective mitral valve surgery. INTERVENTIONS: Induction of anesthesia consisted of sufentanil (1 microgram/kg), propofol (1 microgram/mL) target plasma concentration achieved over 3 minutes, and atracurium (0.5 mg/kg). The propofol target-controlled infusion was maintained at 1 microgram/mL throughout surgery and stopped at skin closure. A continuous infusion of sufentanil at 1.8 micrograms/kg/hr was started after induction and reduced to 0.9 microgram/kg/hr at the start of cardiopulmonary bypass and stopped at the end of bypass. Atracurium was infused at a rate of 0.5 mg/kg/hr up to sternal closure. No inhalation agents were used. MEASUREMENTS AND MAIN RESULTS: Hemodynamic data were within normal limits. Six patients (40%) responded to verbal commands within 15 minutes postoperatively, 10 (67%) within the first hour, and all patients recovered within 2 hours. Four patients (27%) resumed spontaneous ventilation within the first 15 postoperative minutes. The time to successful spontaneous ventilation was 169 +/- 42 minutes. Spontaneous ventilation was associated with a 21% increase in cardiac index. Total sufentanil dose was 328 +/- 28 micrograms (4.6 +/- 0.2 microgram/kg), whereas total propofol dose was 862 +/- 44 mg (13.1 +/- 1.2 mg/kg). No patient required reintubation. CONCLUSION: The simplicity of the method with only one change in infusion rate is a major advantage. The technique permits predictable recovery and return to spontaneous ventilation in all patients. Its use in patients entering early extubation protocols is appealing for its reproducibility, simplicity, and safety.