Mediastinal Bleeding After Cardiopulmonary Bypass in Pediatric Patients

Background. The purpose of our review was to develop simple clinical recommendations to reduce the need for allogeneic blood transfusions in children undergoing cardiac operations.

Methods. The literature on hemostasis as it relates to children, cardiac disease in children, and pediatric heart surgery was reviewed. We also reexamined the efficacy of several strategies in this patient population: on-site monitoring of coagulation, transfusion of fresh whole blood, and administration of desmopressin, ε-aminocaproic acid, or aprotinin.

Results. Children with heart disease may present with preoperative thrombocytopenia, reduced platelet aggregation, and a decreased level of von Willebrand factor. Infants less than 6 months of age show a significant dilution of coagulation factors and decreased platelet counts during cardiopulmonary bypass. Fresh whole blood reduces blood loss in children younger than 2 years undergoing complex operations. Desmopressin does not reduce bleeding, whereas on-site monitoring, synthetic antifibrinolytics, and aprotinin require further evaluation in pediatric cardiac surgical patients.

Conclusions. The use of fresh whole blood to reduce blood loss in children younger than 2 years undergoing complex heart operations is recommended. Therapy for excessive bleeding after cardiopulmonary bypass will vary according to the patient's age, platelet count, and activated partial thromboplastin and prothrombin times.     

Treatment of Excessive Mediastinal Bleeding After Cardiopulmonary Bypass

Background. Excessive mediastinal bleeding after cardiopulmonary bypass is one of the most frequently reported complications of cardiac operations. Appropriate treatment requires a rapid and effective diagnostic work-up, based on the knowledge of the pathophysiology induced by cardiopulmonary bypass.

Methods. Possible causes, diagnostic methods available, and therapeutic approaches are reviewed in the light of the literature published on excessive bleeding after cardiac operations.

Results. When bleeding is massive (>250 to 300 mL/h for the first 2 hours, >150 mL/h thereafter), immediate surgical reexploration is mandatory. When bleeding is less important (50 to 150 mL/h), the decision to reoperate should be based on the presence of hemodynamic compromise or a suspected surgical cause. Otherwise, coagulation testing should allow the correction of hemostatic defects as appropriate with protamine, platelet concentrates, fresh frozen plasma, desmopressin, or antifibrinolytics. Hypothermia and hypotension should be corrected and a trial of positive end-expiratory pressure may be considered if diffuse mediastinal oozing (especially from the bed of the mammary artery) is suspected.

Conclusions. A protocol is suggested to guide treatment, taking into account the rapidity of blood loss and the suspected underlying cause.     

Blood coagulation and autologous blood transfusion in cardiac surgery

Study Objective: To review the basic pathophysiology of altered coagulation associated with cardiopulmonary bypass and autologous blood transfusion in cardiac surgery.

Design: Review of rational use of heparin, mechanisms and treatment of coagulation disorders, and autologous blood transfusion.

Setting: Cardiac surgery in community and academic hospitals.

Patients: Adult cardiac surgical patients.

Main Results: Heparin is most commonly used for anticoagulation during cardiopulmonary bypass. Although activated clotting time is widely used to assess heparin-induced anticoagulation, the minimum time to prevent clotting during cardiopulmonary bypass remains unclear. Activated clotting time is affected by many factors other than heparin, such as antithrombin III, blood temperature, platelet count, and age. The rational use of activated clotting time still must be defined.

The frequency of abnormal bleeding after cardiopulmonary bypass is significant. Although inadequate surgical hemostasis is the most frequent cause of bleeding, altered coagulation often is present. A decreased number of functional platelets is one of the important causes of bleeding diathesis. Platelet dysfunction is induced by perioperative medication such as aspirin. Cardiopulmonary bypass decreases functional platelets by degranulation, fragmentation, and loss of fibrinogen receptors. Medications such as prostacyclin and iloprost may be useful to protect these platelets. Desmopressin increases factor VIII:C and von Willebrand's factor, leading to a decrease in bleeding time. Desmopressin may be useful to decrease blood loss in repeat cardiac operations, complex cardiac surgery, and abnormal postoperative bleeding.

Patients undergoing coronary artery bypass grafting immediately after streptokinase infusion also are at risk for abnormal bleeding. Transfusion of fresh frozen plasma and cryoprecipitate may be necessary.

Autologous blood transfusion is cost-effective and the safest way to avoid or decrease homologous blood transfusion. Predonation, intraoperative salvage, and postoperative salvage are encouraged. Erthroprotein may be useful in increasing the amount of predonation red cells.

Conclusions: Coagulation disorders in cardiac surgery are caused by many factors, such as heparin, platelet dysfunction, and fibronolysis. Rational use of blood component therapy and medications such as heparin, protamine, and desmorpessin are mandatory. Autologous blood transfusions is very useful in decreasing or obviating the use of homologous blood transfusion.     

Heparin-induced platelet dysfunction and cardiopulmonary bypass

Background. Cardiopulmonary bypass is associated with impaired platelet macroaggregation. Heparin contributes to platelet dysfunction before extracorporeal circulation. In vitro heparinization of whole blood does not impair macroaggregation. Heparin releases several endothelial proteins; thus heparin may inhibit macroaggregation indirectly.

Methods. Patients undergoing operations using cardiopulmonary bypass and ABO blood group compatible volunteers were studied. Whole blood impedance aggregometry assessed macroaggregation in response to collagen (0.6 μg ml⁻¹) in blood diluted either with normal saline or with platelet poor plasma, obtained from patients at different stages of cardiopulmonary bypass.

Results. Before heparinization, blood diluted with its own platelet poor plasma recorded an impedance change of 13.0 (4.7 to 15.6) Ohms. Platelet poor plasma obtained after heparinization or during extracorporeal circulation reduced this response to 3.7 (1.1 to 8.4) and 2.0 (1.1 to 3.3) Ohms, respectively (both p < 0.0001 versus pre-heparin; n = 13). Macroaggregation in blood from volunteers was similarly inhibited by patients’ platelet poor plasma (n = 30). The macroaggregatory response in blood sampled after heparinization for cardiopulmonary bypass, decreased gradually from 11.4 (8.2 to 15.9) Ohms immediately after sampling to 1.7 (1.4 to 4.1) Ohms 2 hours later (p < 0.0001; n = 11).

Conclusions. In vivo heparinization induces plasma changes that inhibit platelet macroaggregation. This is an indirect, delayed inhibition that is transferable in vitro to normal platelets.     

Late complications of tissue glues in aortic surgery

Background. Tissue glues are used in cardiothoracic surgery as an adjunct to operative procedures where tissues are frail, as in aortic dissection, or where added hemostasis is required. This study was undertaken to review the use of tissue glue in our institution over a 5.5-year period. The aim of the study was to identify any potentially glue-related complications.

Methods. A review of tissue glue use for the period from January 1993 to September 1998 was performed and pre-, intra-, and postoperative parameters were collected. After some unusual surgical findings, of special interest was a range of pathology found at late reoperation.

Results. A total of 67 cases of tissue glue use were identified, with the majority of operations for type A dissection (76%). There were two intraoperative deaths. Twenty-seven of 65 patients (41%) required 29 further open chest operations; of these, 17 were for acute problems of bleeding or tamponade. Twelve patients (18%) underwent late reoperations months to years later. Nine of these patients, concentrated in two operative groups (7 patients with aortic valve resuspension and 2 patients who had undergone “switch” operations for transposition of great vessels), displayed complications related to the application of gelatin-resorcinol-formaldehyde (GRF) tissue glue.

Conclusions. Indications for tissue glues in cardiothoracic surgery must be carefully considered. We have reviewed our use of some tissue glues in acute type A aortic dissections and in pediatric cardiac patients and have discontinued the use of GRF glues because of unsatisfactory long-term complications.     

Natural and synthetic antifibrinolytics in cardiac surgery

In an effort to reduce morbidity associated with transfusion of blood products, the use of antifibrinolytics to decrease bleeding and transfusions after cardiopulmonary bypass (CPB) is receiving widespread attention. The predominant haemostatic defect induced by CPB and, therefore, the mechanisms by which natural (aprotinin) or synthetic antifibrinolytics (sigma-amino-caproic acid, tranexamic acid) exert their effects have been difficult to define. Nonetheless, all three substances appear to be effective in the treatment or in the prevention of excessive bleeding associated with cardiac surgery. However, the administration of these drugs should not attempt to replace meticulous surgical and anaesthetic care. In particular, the importance of an appropriate transfusion practice cannot be overemphasized. The efficient use of these, sometimes expensive, drugs must take into account not only the initial cost, but also the short- and long-term economic consequences for the health care provider of using, or not using, a given medication. Unfortunately, the comprehensive data on which authoritative conclusions may be reached are not yet available. Pending availability of these data, the present use of antifibrinolytics at the Montreal Heart Institute is the following: (1) patients undergoing elective primary myocardial revascularization or valve surgery do not receive prophylactic antifibrinolytics; (2) patients undergoing repeat myocardial revascularization, repeat valve surgery, or primary or repeat combined procedures, receive prophylactic sigma-aminocaproic acid; (3) sigma-aminocaproic acid may be used to treat excessive chest drainage in the postoperative period; (4) the prophylactic and the therapeutic uses of low doses of aprotinin are currently under investigation.     

Impaired distensibility of neoaorta after arterial switch procedure

Background. Although the arterial switch operation has become the standard surgical procedure for treatment of complete transposition, postoperative problems have not been fully appreciated. One such problem may be the postoperative function of great arteries that are manipulated radically.

Methods. The diameters at four levels of the aorta were measured in 36 patients who had undergone arterial switch operation and the distensibilities were calculated. The data were compared with that of age-matched controls.

Results. At the level of the Valsalva sinus, aortic diameters after one-staged and two-staged operations were 137.0% ± 21.3%N and 152.4% ± 17.7%N of the normal aorta, respectively. The distensibilities at the Valsalva sinus in patients after one-staged and two-staged operations were 1.2 ± 0.7 and 1.5 ± 0.8 cm² · dyn⁻¹ · 10⁻⁶, and at the supraaortic ridge were 2.5 ± 1.5 and 1.9 ± 1.5 cm² · dyn⁻¹ · 10⁻⁶, respectively.

Conclusions. In patients after arterial switch procedure, the distensibility of the base of aorta is decreased. Long-term follow-up is necessary to clarify the influence of the “stiffness” of the base of aorta.     

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery

Background. Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products.

Methods. One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded.

Results. The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 ± 9 × 10³/mm³ vs 137 ± 8 × 10³/mm³; p < 0.01). This was paralleled by a reduction in β-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed.

Conclusions. The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.     

Laboratory Evaluation of Hemostasis Before Cardiac Operations

Background. Several opinions prevail on the necessity and on the choice of laboratory coagulation tests to perform before cardiac operations. This review aims at providing simple and clinically relevant recommendations.

Methods. The literature on preoperative coagulation testing was reexamined, taking into account the low prevalence of unknown and unsuspected hemorrhagic disease, and the risk of false positive results.

Results. Carefully controlled, randomized trials are lacking but it seems appropriate to perform a few inexpensive tests (platelet count, activated partial thromboplastin time, and prothrombin time), mainly to obtain baseline values for patients who are about to undergo a major hemostatic challenge. A more complete coagulation profile (eg, bleeding time, fibrinogen concentration, thrombin time) should be considered in patients who present with a history of bleeding.

Conclusions. A careful medical history is the key element to detect a bleeding disorder. Only a very limited coagulation profile should be obtained in asymptomatic patients before cardiac operations.     

Perioperative Therapie mit Thrombozytenaggregationshemmern

Antiplatelet therapy is used to prevent thromboembolic complications in patients with artherothrombotic disease. In clinical routine an assessment of the risk of perioperative bleeding must be weighed against the risk of thromboembolic complications in the event of discontinuation of antiplatelet agents. The indications as well as the timepoint for the termination of antiplatelet therapy are important issues to consider. The premature interruption of oral antiplatelet therapy with recovery of platelet function may lead to recurrence of thromboembolic events. Especially patients with intracoronary stents are at threat when the dual platelet therapy is interrupted before complete endothelialization of the stent.     

Platelet activation,aggregation, and life span in calves implanted with axial flow ventricular assist devices

Background. A variety of rotary blood pumps are under development worldwide to serve as chronic ventricular assist devices (VADs). Historically VADs have been associated with thrombotic and thromboembolic complications, yet the ability to evaluate the thrombotic process in preclinical device testing has been limited.

Methods. We have developed and applied flow cytometric assays for activated platelets, platelet microaggregates, and platelet life span and consumption to calves implanted with an axial flow VAD and calves undergoing a sham surgical procedure.

Results. Surgical sham calves had significant increases in circulating activated platelets (p < 0.05) that resolved within 17 days, and no increases in circulating platelet microaggregates. Calves with uneventful VAD implant periods had early transient elevations in platelet microaggregates and prolonged elevations in activated platelets that did not recover to preoperative values during the study. Daily platelet consumption in VAD implanted calves was increased by 20% ± 3%. Calves with thrombotic deposition within the VAD and elevated thromboembolism observed at autopsy experienced increases in circulating activated platelets and microaggregates at the end of the implant period when VAD flow decreased.

Conclusions. This study demonstrates the ability of flow cytometry-based platelet assays to differentiate VAD implant operations from VAD support, and suggests differences that exist between uneventful VAD support and support with complications. These techniques should have value in evaluating other cardiovascular devices undergoing preclinical testing and provide insight into the temporal impact of these devices on the hemostatic system.     

Meta-analysis of COL1A1 Sp1 polymorphism in relation to bone mineral density and osteoporotic fracture

Genetic factors play an important role in the pathogenesis of osteoporosis and several candidate gene polymorphisms have been implicated in the regulation of this process. One of the most widely studied is the Sp1 binding site polymorphism in the COL1A1 gene. This polymorphism has been associated with BMD and osteoporotic fracture in several studies, but the data from different studies have been conflicting. Here we have attempted to clarify the association between COL1A1 Sp1 alleles, BMD, and osteoporotic fracture by conducting a meta-analysis of 26 published studies including 7849 participants. Under a fixed effects model, BMD values at the lumbar spine (6800 subjects) were significantly lower in the “Ss” genotype group when compared with “SS” homozygotes (standardized mean DIFFERENCE = 0.131 [95% CI, 0.06,0.16], P = 0.00005) but the difference was not significant for the “ss” comparison (0.09 [−0.03,0.21], P = 0.13). At the femoral neck (6750 subjects) BMD values were lower in the “Ss” genotype (0.14 [0.08,0.19], P < 0.00001) and lower still in the “ss” genotype group (0.19 [0.07,0.31], P = 0.001). Similar results were found when the data were analyzed under a random effects model. Analysis of fracture data (6961 subjects) showed an increased odds ratio for any fracture in “Ss” subjects (1.26 [95% CI 1.09,1.46], P = 0.002) and an even greater increase in “ss” subjects (1.78 [1.30,2.43], P = 0.0003). Subgroup analysis showed that increased risk was largely attributable to vertebral fracture where the odds ratio was 1.37 [1.15,1.64] for “Ss” (P = 0.0004) and 2.48 [1.69,3.65] for “ss” (P < 0.00001). The risk of nonvertebral fracture was not increased in relation to the COL1A1 genotype, although power to detect an effect was limited by the fact that fewer studies had analyzed nonvertebral fracture. We conclude that the COL1A1 Sp1 alleles are associated with a modest reduction in BMD and a significant increase in risk of osteoporotic fracture, particularly vertebral fracture.     

Hemorragia,hemostasia y trombosis en cirugía

Surgery is a leading cause of major hemorrhage as well as of thrombosis unless patients are administered appropriate antithrombotic prophylaxis after their thrombo-hemorrhagic risk has been stratified. Therefore, thorough preoperative evaluation is essential to minimize surgical complications. In cases of incoercible bleeding, drugs such as desmopressin, synthetic antifibrinolytics or recombinant factor VII can be administered. To prevent postoperative thrombosis, low molecular weight heparins or pentasaccharide have been shown to significantly reduce the incidence of thromboembolism.     

Extension of the “Elephant Trunk” Technique in Complex Aortic Pathology: The “Bidirectional” Option

Background. The “elephant trunk” technique, using a free-floating vascular prosthesis, was originally described to facilitate a subsequent operation on the downstream aorta. We developed an additional refinement of this technique, called the “bidirectional elephant trunk.” This option may represent an interesting tool in more complex aortic operations, especially when the descending aorta has to be replaced first in patients with concomitant pathology of the ascending aorta or of the aortic arch.

Methods. The initial operation is performed through a left thoracotomy. The proximal elephant trunk is created by invaginating the future aortic arch graft into the descending aortic graft. The proximal anastomosis between the doubled graft and the proximal descending aorta is performed first. During construction of the distal anastomosis, a distal elephant trunk may be inserted likewise. If the aortic arch and ascending aorta have to be replaced later, this second step is performed through a median sternotomy. The free-floating arch graft is pulled out of the proximal descending aorta with a nerve hook, unfolded, and used for total arch replacement.

Results. This technique was used successfully in 3 patients without mortality. No major complications were observed excepted persistent hoarseness in a patient with preoperative paresis of the recurrent nerve. No perfusion problems due to the unfolding of the free-floating graft occurred during the second operation.

Conclusions. The bidirectional elephant trunk technique is an interesting option that may be suitable for patients presenting with a complex pathology of the whole thoracic aorta when the descending segment has to be replaced first.     

Reduction in Requirements for Allogeneic Blood Products: Nonpharmacologic Methods

Background. Various strategies have been proposed to decrease bleeding and allogeneic transfusion requirements during and after cardiac operations. This article attempts to document the usefulness, or lack thereof, of the nonpharmacologic methods available in clinical practice.

Methods. Blood conservation methods were reviewed in chronologic order, as they become available to patients during the perisurgical period. The literature in support of or against each strategy was reexamined critically.

Results. Avoidance of preoperative anemia and adherence to published guidelines for the practice of transfusion are of paramount importance. Intraoperatively, tolerance of low hemoglobin concentrations and use of autologous blood (predonated or harvested before bypass) will reduce allogeneic transfusions. The usefulness of plateletpheresis and retransfusion of shed mediastinal fluid remains controversial. Intraoperatively and postoperatively, maintenance of normothermia contributes to improved hemostasis.

Conclusions. Several approaches have been shown to be effective. An efficient combination of methods can reduce, and sometimes abolish, the need for allogeneic blood products after cardiac operations, inasmuch as all those involved in the care of cardiac surgical patients adhere thoughtfully to existing transfusion guidelines.     

Preoperative Clinical Assessment of Hemostatic Function in Patients Scheduled for a Cardiac Operation

Background. Bleeding during and after cardiac operations is usually attributed to inadequate surgical hemostasis or cardiopulmonary bypass-induced disorders of hemostasis. Patient-related factors often are neglected.

Methods. Articles published between 1976 and 1996 on the preoperative assessment of surgical patients were reviewed to determine the clinical elements most likely to predict increased perioperative blood requirements.

Results. Preoperative assessment is based on a carefully conducted interview (history of bruising, petechiae, recent or excessive bleeding after operation, chronic drug therapy) and physical examination. A standardized questionnaire to enhance the reliability of the assessment is presented. Thus, patients at high risk of being transfused can be identified early on and may be enrolled in various programs designed to decrease bleeding and the need for allogeneic blood transfusions.

Conclusions. Clinical assessment of hemostatic function before cardiac operations is both effective and efficient. It obviates the need for routine laboratory testing and favors the introduction of blood conservation strategies early on during the process of care.     

Glucose Level and Myocardial Recovery After Warm Arrest

Background. During induced cold ischemia for cardiac operations, increasing glucose concentration is not thought to enhance myocardial protection and may detrimentally affect recovery. However, during “warm aerobic” arrest, increased glucose availability as substrate could enhance postischemic metabolic and functional recovery, as during and after ischemia, myocytes shift preference for substrate from fatty acids to glucose. Unfortunately, hyperglycemia may also increase patient susceptibility to neurologic injury.

Methods. This experiment was designed to study the optimal dose of glucose and its effect on function during warm arrest. Isolated, retrograde-perfused rabbit hearts received multidose cardioplegia containing increasing concentrations of glucose, from 0 to 88 mmol/L, and underwent 120 minutes of “warm” 34°C global ischemia. Osmolarities were adjusted equivalently.

Results. After 34°C ischemia, hearts treated with 5 to 88 mmol/L glucose showed significantly better functional recovery than those treated with 0 to 1 mmol/L glucose. However, the addition of 22 mmol/L glucose demonstrated optimal recovery with no further incremental enhancement with more glucose. Additional hearts receiving 0 or 22 mmol/L glucose had high-energy phosphates, lactate, CO₂, and pH measured. The 22 mmol/L glucose hearts demonstrated active metabolism and significantly better recovery of high-energy phosphate levels than controls.

Conclusions. Increasing glucose level modestly during warm arrest enhanced recovery, but profound hyperglycemia did not incrementally improve this effect, mandating a cautious use of glucose.     

Silent Aspiration After Coronary Artery Bypass Grafting

Background. “Silent” aspiration was recognized to be a more frequent complication at this hospital in patients who have had coronary artery bypass grafting than in the general surgical population.

Methods. A case-control retrospective study covering a 4.5-year period was conducted to determine risk factors for pharyngeal dysfunction resulting in silent aspiration.

Results. Significant predictors of silent aspiration were age, history of cerebral vascular disease, insulin-dependent diabetes mellitus, myocardial infarction, and chronic obstructive pulmonary disease. Intraaortic balloon pump and number of units of fresh-frozen plasma were the only independent intraoperative factors associated with silent aspiration in a model using continuous variables directly. Cold fibrillation was used in 7 of 53 study cases but no control patients, so it could not be modeled. Postoperative complications occurring with greater frequency included neurologic complications, adverse pulmonary outcomes, repeat surgical interventions, infection, and death. Using an Aspiration Risk Profile developed from the retrospective study, in a detailed prospective study of 10 patients, 3 of 4 patients with postoperative dysphagia had objective evidence of stroke.

Conclusions. These findings suggest that postoperative coronary artery bypass graft dysphagia may be the result of intraoperative cerebral injury, and that careful postoperative clinical evaluation of coronary artery bypass graft patients with risk factors may result in early diagnosis of pharyngeal dysfunction with the goals of preventing silent aspiration and reducing morbidity, mortality, and hospital cost.     

Laparoscopic renal-adrenal surgery in patients on oral anticoagulant therapy

PURPOSE: Patients requiring chronic anticoagulation are theoretically at increased risk for hemorrhage or thromboembolism perioperatively. Experience with laparoscopic renal/adrenal surgery in patients on chronic warfarin is limited. We assessed hemorrhagic/thromboembolic complications in this group of patients. MATERIALS AND METHODS: The records of 787 patients undergoing laparoscopic renal/adrenal surgery were retrospectively reviewed. A total of 25 patients on chronic oral anticoagulation with warfarin were identified. The indications for warfarin therapy as well as perioperative management were reviewed. Clinical parameters, including operative time, estimated blood loss, hemorrhagic/thromboembolic complications and transfusions, were documented and compared with those in patients not receiving chronic anticoagulation. RESULTS: Atrial fibrillation (56% of cases) and a prosthetic mitral valve (28%) were the most frequent indications for chronic anticoagulation. Bridging anticoagulation with unfractionated heparin was the most frequent management method (68% of cases). Patients with anticoagulation were older (p <0.001) and hospitalized longer (<0.001) than those without anticoagulation. Operative time, estimated blood loss and the conversion rate were not significantly different between the groups. However patients on chronic warfarin significantly more often required transfusion (24% vs 5.2%, p <0.005) and had more postoperative bleeding episodes (8% vs 0.9%, p <0.05) than patients not on chronic anticoagulation. No thromboembolic events occurred in the anticoagulated group, while 3 occurred in the nonanticoagulated group (p = 1). CONCLUSIONS: Laparoscopic renal/adrenal surgery in patients requiring chronic anticoagulation therapy can be performed safely. The risk of intraoperative bleeding is not increased, although the incidence of postoperative bleeding as well as transfusions is higher.     

Recovery following outpatient anesthesia: Use of enflurane versus propofol

Study Objective: To compare the intraoperative conditions and postoperative recovery of patients following the use of either propofol-nitrous oxide (N₂O) or enfurane-N₂O for maintenance of outpatient anesthesia.

Design: Randomized, single-blind study.

Setting: University hospital outpatient surgery center.

Patients: 61 ASA physical status I and II, healthy female outpatients undergoing laparoscopic surgery.

Interventions: Patients were randomly assigned to one of three anesthetic regimes. Group 1 (control) received thiopental sodium 4 mg/kg intravenously (IV), followed by 0.5% to 1.5% enfurane and 67% N₂0 in oxygen (O₂). Group 2 received propofol 2 mg/kg IV, followed by 0.5% to 1.5% enfurane and 67% N₂O in O₂. Group 3 received propofol 2 mg/kg IV, followed by propofol 50 to 160 μg/kg/min IV and 67% N₂O in O₂. All patients received succinylcholine 1 mglkg IV to facilitate tracheal intubation and atracurium 10 to 20 mg IV to provide adequate relaxation during the maintenance period.

Measurements and Main Results: Recovery from anesthesia was assessed by a research nurse who was unaware of the anesthetic technique used. The mean ± SD time to eye opening was significantly longer in the thiopental-enflurane-N₂O group (Group 1) than in the propofol-propofol-N₂0 group (Group 3) (6.1 ± 2.5 minutes vs. 3.5 ± 2.8 minutes, respectively). In addition, the mean time to respond to verbal commands was significantly shorter in the propofol induction groups compared with the thiopental induction group. However, the use of enfurane versus propofol for maintenance of anesthesia did not significantly prolong the time from arrival in the recovery room to sitting, tolerating oral fluids, walking, or being judged “fit for discharge.” There were no differences among the three groups with respect to postoperative pain or analgesic requirements. Finally, patients who received enfurane for maintenance of anesthesia had a significantly higher frequency of nausea and vomiting than the propofol maintenance group.

Conclusion: Induction of anesthesia with propofol is associated with a more rapid emergence from anesthesia than induction with thiopental. Maintenance of anesthesia with enfurane did not prolong recovery compared with maintenance with propofol, but enfurane was associated with increased frequency of postoperative nausea and vomiting.