Anesthesia awareness and the bispectral index.

BACKGROUND: Awareness during anesthesia is a serious complication with potential long-term psychological consequences. Use of the bispectral index (BIS), developed from a processed electroencephalogram, has been reported to decrease the incidence of anesthesia awareness when the BIS value is maintained below 60. In this trial, we sought to determine whether a BIS-based protocol is better than a protocol based on a measurement of end-tidal anesthetic gas (ETAG) for decreasing anesthesia awareness in patients at high risk for this complication. METHODS: We randomly assigned 2000 patients to BIS-guided anesthesia (target BIS range, 40 to 60) or ETAG-guided anesthesia (target ETAG range, 0.7 to 1.3 minimum alveolar concentration [MAC]). Postoperatively, patients were assessed for anesthesia awareness at three intervals (0 to 24 hours, 24 to 72 hours, and 30 days after extubation). RESULTS: We assessed 967 and 974 patients from the BIS and ETAG groups, respectively. Two cases of definite anesthesia awareness occurred in each group (absolute difference, 0%; 95% confidence interval [CI], -0.56 to 0.57%). The BIS value was greater than 60 in one case of definite anesthesia awareness, and the ETAG concentrations were less than 0.7 MAC in three cases. For all patients, the mean (+/-SD) time-averaged ETAG concentration was 0.81+/-0.25 MAC in the BIS group and 0.82+/-0.23 MAC in the ETAG group (P=0.10; 95% CI for the difference between the BIS and ETAG groups, -0.04 to 0.01 MAC). CONCLUSIONS: We did not reproduce the results of previous studies that reported a lower incidence of anesthesia awareness with BIS monitoring, and the use of the BIS protocol was not associated with reduced administration of volatile anesthetic gases. Anesthesia awareness occurred even when BIS values and ETAG concentrations were within the target ranges. Our findings do not support routine BIS monitoring as part of standard practice. (ClinicalTrials.gov number, NCT00281489 [ClinicalTrials.gov].).

Coronary artery bypass graft surgery--care globalization: the impact of national care on fatal and nonfatal outcome.

OBJECTIVE: In an international, prospective, observational study, we contrasted adverse vascular outcomes among four countries and then assessed practice pattern differences that may have contributed to these outcomes. METHODS: A total of 5065 patients undergoing coronary artery bypass graft surgery were analyzed at 70 international medical centers, and from this pool, 3180 patients from the 4 highest enrolling countries were selected. Fatal and nonfatal postoperative ischemic complications related to the heart, brain, kidney, and gastrointestinal tract were assessed by blinded investigators. RESULTS: In-hospital mortality was 1.5% (9/619) in the United Kingdom, 2.0% (9/444) in Canada, 2.7% (34/1283) in the United States, and 3.8% (32/834) in Germany (P = .03). The rates of the composite outcome (morbidity and mortality) were 12% in the United Kingdom, 16% in Canada, 18% in the United States, and 24% in Germany (P < .001). After adjustment for difference in case-mix (using the European System for Cardiac Operative Risk Evaluation) and practice, country was not an independent predictor for mortality. However, there was an independent effect of country on composite outcome. The practices that were associated with adverse outcomes were the intraoperative use of aprotinin, intraoperative transfusion of fresh-frozen plasma or platelets, lack of use of early postoperative aspirin, and use of postoperative heparin. CONCLUSIONS: Significant between-country differences in perioperative outcome exist and appear to be related to hematologic practices, including administration of antifibrinolytics, fresh-frozen plasma, platelets, heparin, and aspirin. Understanding the mechanisms for these observations and selection of practices associated with improved outcomes may result in significant patient benefit.

Case report: inferior vena-cava right atrial anastomotic stenosis after bicaval orthotopic heart transplantation.

PURPOSE: This case report describes the occurrence of acute postoperative liver and renal failure after bicaval orthotopic heart transplantation (OHT) due to stenosis of the inferior vena cava (IVC)-right atrial (RA) anastomosis. We also discuss the role of measuring femoral venous pressure and transesophageal echocardiography (TEE) in establishing the diagnosis. CLINICAL FEATURES: A 42-yr-old female patient with idiopathic dilated cardiomyopathy underwent an OHT, using the bicaval anastomotic technique. During the first 12 hr postoperatively she developed unexplained kidney and liver failure. Her left and right ventricular functions were excellent and the right and left sided filling pressures were normal. The femoral pressure was elevated while the RA pressure was normal. An emergent TEE showed colour-flow and Doppler characteristics consistent with IVC-RA anastomotic stenosis. Emergent surgical re-exploration was undertaken; a hemostatic suture was found at the RA cannulation site that had caused the constriction of the IVC-RA anastomosis. CONCLUSIONS: Acute liver and renal failure after OHT can have multiple causes including ischemia due to a low flow state. This case demonstrates the importance of doing a detailed intraoperative TEE after OHT, and the importance of repeating the intraoperative examination after any hemostatic sutures are placed. Femoral venous pressure monitoring can be a useful diagnostic tool in detecting IVC-RA stenosis.

Intrapatient reproducibility of the BISxp monitor.

BACKGROUND: The Bispectral Index (BIS) reportedly reflects anesthetic depth. It is recommended that anesthetic agents should be titrated to maintain the BIS between 40 and 60 arbitrary BIS units during anesthesia. For anesthesia providers to follow this recommendation, the monitor should be predictably affected by different anesthetic agents and have good interpatient and intrapatient reproducibility. The authors hypothesized that when two BISxp devices (Aspect Medical Systems, Newton, MA) are placed concurrently on the same patient, their readings are concordant throughout the anesthetic period. METHODS: Simultaneous BIS recordings from two BISxp monitors were obtained during anesthesia at 5-s intervals from 12 participants. RESULTS: In total 22,860 concurrent paired BIS readings were obtained. For 10.7% of the time, there were sustained periods of 30 s or greater where the readings suggested a different depth of anesthesia. For 6% of the time, there were sustained periods of 30 s or greater where the readings differed by 10 or more arbitrary BIS units. The regression coefficient (R) for the two devices was 0.65 (range, 0.35-0.92). There was zero bias between the devices, and the 95% limits of agreement ranged between -18 and +17. CONCLUSION: A conflicting anesthetic management was suggested by the simultaneous BIS readings 10.7% of the time. These results suggest that BISxp does not always provide a reproducible single number. Anesthesia providers should not rely exclusively on the BIS reading when assessing depth of anesthesia.

Guidelines and alternatives for neuraxial anesthesia and venous thromboembolism prophylaxis in major orthopedic surgery.

Neuraxial anesthesia during major orthopedic surgery, combined with venous thromboembolism prophylaxis, is generally safe and well tolerated, with potential benefits over general anesthesia. The risk of spinal/epidural hematoma, a rare but very serious complication, can be minimized by careful patient selection and attention to anesthetic technique. This risk is further reduced with the use of peripheral nerve blocks in place of neuraxial anesthesia.