Processed electroencephalography: impact of patient age and surgical position on intraoperative processed electroencephalogram monitoring of burst-suppression.

We previously reported that processed EEG underestimated the amount of burst suppression compared to off-line visual analysis. We performed a follow-up study to evaluate the reasons for the discordance. Forty-five patients were monitored intraoperatively with processed EEG. A computer algorithm was used to convert the SedLine® (machine)-generated burst suppression ratio into a raw duration of burst suppression. The reference standard was a precise off-line measurement by two neurologists. We measured other potential variables that may affect machine accuracy such as age, surgery position, and EEG artifacts. Overall, the median duration of bust suppression for all study subjects was 15.4 min (Inter-quartile Range [IQR] = 1.0-20.1) for the machine vs. 16.1 min (IQR = 0.3-19.7) for the neurologists' assessment; the 95% limits of agreement fall within - 4.86 to 5.04 s for individual 30-s epochs. EEG artifacts did not affect the concordance between the two methods. For patients in prone surgical position, the machine estimates had significantly lower overall sensitivity (0.86 vs. 0.97; p = 0.038) and significantly wider limits of agreement ([- 4.24, 3.82] seconds vs. [- 1.36, 1.13] seconds, p = 0.001) than patients in supine position. Machine readings for younger patients (age < 65 years) had higher sensitivity (0.96 vs 0.92; p = 0.021) and specificity (0.99 vs 0.88; p = 0.007) for older patients. The duration of burst suppression estimated by the machine generally had good agreement compared with neurologists' estimation using a more precise off-line measurement. Factors that affected the concordance included patient age and position during surgery, but not EEG artifacts.

Hedgehog signaling in the airway epithelium of patients with chronic obstructive pulmonary disease.

Genome-wide association studies have linked gene variants of the receptor patched homolog 1 (PTCH1) with chronic obstructive pulmonary disease (COPD). However, its biological role in the disease is unclear. Our objective was to determine the expression pattern and biological role of PTCH1 in the lungs of patients with COPD. Airway epithelial-specific PTCH1 protein expression and epithelial morphology were assessed in lung tissues of control and COPD patients. PTCH1 mRNA expression was measured in bronchial epithelial cells obtained from individuals with and without COPD. The effects of PTCH1 siRNA knockdown on epithelial repair and mucous expression were evaluated using human epithelial cell lines. Ptch1+/- mice were used to assess the effect of decreased PTCH1 on mucous expression and airway epithelial phenotypes. Airway epithelial-specific PTCH1 protein expression was significantly increased in subjects with COPD compared to controls, and its expression was associated with total airway epithelial cell count and thickness. PTCH1 knockdown attenuated wound closure and mucous expression in airway epithelial cell lines. Ptch1+/- mice had reduced mucous expression compared to wildtype mice following mucous induction. PTCH1 protein is up-regulated in COPD airway epithelium and may upregulate mucous expression. PTCH1 provides a novel target to reduce chronic bronchitis in COPD patients.

Burst-suppression ratio underestimates absolute duration of electroencephalogram suppression compared with visual analysis of intraoperative electroencephalogram.

BACKGROUND: Machine-generated indices based on quantitative electroencephalography (EEG), such as the patient state index (PSI™) and burst-suppression ratio (BSR), are increasingly being used to monitor intraoperative depth of anaesthesia in the endeavour to improve postoperative neurological outcomes, such as postoperative delirium (POD). However, the accuracy of the BSR compared with direct visualization of the EEG trace with regard to the prediction of POD has not been evaluated previously. METHODS: Forty-one consecutive patients undergoing non-cardiac, non-intracranial surgery with general anaesthesia wore a SedLine ® monitor during surgery and were assessed after surgery for the presence of delirium with the Confusion Assessment Method. The intraoperative EEG was scanned for absolute minutes of EEG suppression and correlated with the incidence of POD. The BSR and PSI™ were compared between patients with and without POD. RESULTS: Visual analysis of the EEG by neurologists and the SedLine ® -generated BSR provided a significantly different distribution of estimated minutes of EEG suppression ( P =0.037). The Sedline ® system markedly underestimated the amount of EEG suppression. The number of minutes of suppression assessed by visual analysis of the EEG was significantly associated with POD ( P =0.039), whereas the minutes based on the BSR generated by SedLine ® were not associated with POD ( P =0.275). CONCLUSIONS: Our findings suggest that SedLine ® (machine)-generated indices might underestimate the minutes of EEG suppression, thereby reducing the sensitivity for detecting patients at risk for POD. Thus, the monitoring of machine-generated BSR and PSI™ might benefit from the addition of a visual tracing of the EEG to achieve a more accurate and real-time guidance of anaesthesia depth monitoring and the ultimate goal, to reduce the risk of POD.

Protocol for the Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) study: a pragmatic, randomised clinical trial.

INTRODUCTION: Postoperative delirium, arbitrarily defined as occurring within 5 days of surgery, affects up to 50% of patients older than 60 after a major operation. This geriatric syndrome is associated with longer intensive care unit and hospital stay, readmission, persistent cognitive deterioration and mortality. No effective preventive methods have been identified, but preliminary evidence suggests that EEG monitoring during general anaesthesia, by facilitating reduced anaesthetic exposure and EEG suppression, might decrease incident postoperative delirium. This study hypothesises that EEG-guidance of anaesthetic administration prevents postoperative delirium and downstream sequelae, including falls and decreased quality of life. METHODS AND ANALYSIS: This is a 1232 patient, block-randomised, double-blinded, comparative effectiveness trial. Patients older than 60, undergoing volatile agent-based general anaesthesia for major surgery, are eligible. Patients are randomised to 1 of 2 anaesthetic approaches. One group receives general anaesthesia with clinicians blinded to EEG monitoring. The other group receives EEG-guidance of anaesthetic agent administration. The outcomes of postoperative delirium (≤5 days), falls at 1 and 12 months and health-related quality of life at 1 and 12 months will be compared between groups. Postoperative delirium is assessed with the confusion assessment method, falls with ProFaNE consensus questions and quality of life with the Veteran's RAND 12-item Health Survey. The intention-to-treat principle will be followed for all analyses. Differences between groups will be presented with 95% CIs and will be considered statistically significant at a two-sided p<0.05. ETHICS AND DISSEMINATION: Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) is approved by the ethics board at Washington University. Recruitment began in January 2015. Dissemination plans include presentations at scientific conferences, scientific publications, internet-based educational materials and mass media. TRIAL REGISTRATION NUMBER: NCT02241655; Pre-results.

Impact of intraoperative hypotension and blood pressure fluctuations on early postoperative delirium after non-cardiac surgery.

INTRODUCTION: Postoperative delirium is common in older patients. Despite its prognostic significance, the pathophysiology is incompletely understood. Although many risk factors have been identified, no reversible factors, particularly ones potentially modifiable by anaesthetic management, have been identified. The goal of this prospective cohort study was to investigate whether intraoperative hypotension was associated with postoperative delirium in older patients undergoing major non-cardiac surgery. METHODS: Study subjects were patients >65 years of age, undergoing major non-cardiac surgery, who were enrolled in an ongoing prospective observational study of the pathophysiology of postoperative delirium. Intraoperative blood pressure was measured and predefined criteria were used to define hypotension. Delirium was measured by the Confusion Assessment Method on the first two postoperative days. Data were analysed using t-tests, two-sample proportion tests and ordered logistic regression multivariable models, including correction for multiple comparisons. RESULTS: Data from 594 patients with a mean age of 73.6 years (sd 6.2) were studied. Of these 178 (30%) developed delirium on day 1 and 176 (30%) on day 2. Patients developing delirium were older, more often female, had lower preoperative cognitive scores, and underwent longer operations. Relative hypotension (decreases by 20, 30, or 40%) or absolute hypotension [mean arterial pressure (MAP)<50 mm Hg] were not significantly associated with postoperative delirium, nor was the duration of hypotension (MAP<50 mm Hg). Conversely, intraoperative blood pressure variance was significantly associated with postoperative delirium. DISCUSSION: These results showed that increased blood pressure fluctuation, not absolute or relative hypotension, was predictive of postoperative delirium.

IL-22-producing CD4+ cells are depleted in actively inflamed colitis tissue.

T helper type (Th17) cytokines such as interleukin (IL)-17A and IL-22 are important in maintaining mucosal barrier function and may be important in the pathogenesis of inflammatory bowel diseases (IBDs). Here, we analyzed cells from the colon of IBD patients and show that Crohn's disease (CD) patients had significantly elevated numbers of IL-17+, CD4+ cells compared with healthy controls and ulcerative colitis (UC) patients, but these numbers did not vary based on the inflammatory status of the mucosa. By contrast, UC patients had significantly reduced numbers of IL-22+ cells in actively inflamed tissues compared with both normal tissue and healthy controls. There was a selective increase in mono-IL-17-producing cells from the mucosa of UC patients with active inflammation together with increased expression of transforming growth factor (TGF)-ß and c-Maf. Increasing concentrations of TGF-ß in lamina propria mononuclear cell cultures significantly depleted Th22 cells, whereas anti-TGF-ß antibodies increased IL-22 production. When mucosal microbiota was examined, depletion of Th22 cells in actively inflamed tissue was associated with reduced populations of Clostridiales and increased populations of Proteobacteria. These results suggest that increased TGF-ß during active inflammation in UC may lead to the loss of Th22 cells in the human intestinal mucosa.

Pilot clinical trial of gabapentin to decrease postoperative delirium in older patients.

In this randomized pilot clinical trial, the authors tested the hypothesis that using gabapentin as an add-on agent in the treatment of postoperative pain reduces the occurrence of postoperative delirium. Postoperative delirium occurred in 5/12 patients (42%) who received placebo vs 0/9 patients who received gabapentin, p = 0.045. The reduction in delirium appears to be secondary to the opioid-sparing effect of gabapentin.

Nitrous oxide does not change the incidence of postoperative delirium or cognitive decline in elderly surgical patients.

BACKGROUND: Postoperative delirium and cognitive decline are common in elderly surgical patients after non-cardiac surgery. Despite this prevalence and clinical importance, no specific aetiological factor has been identified for postoperative delirium and cognitive decline. In experimental setting in a rat model, nitrous oxide (N(2)O) produces neurotoxic effect at high concentrations and in an age-dependent manner. Whether this neurotoxic response may be observed clinically has not been previously determined. We hypothesized that in the elderly patients undergoing non-cardiac surgery, exposure to N(2)O resulted in an increased incidence of postoperative delirium than would be expected for patients not receiving N(2)O. METHODS: Patients who were >or=65 yr of age, undergoing non-cardiac surgery and requiring general anaesthesia were randomized to receive an inhalational agent and either N(2)O with oxygen or oxygen alone. A structured interview was conducted before operation and for the first two postoperative days to determine the presence of delirium using the Confusion Assessment Method. RESULTS: A total of 228 patients were studied with a mean (range) age of 73.9 (65-95) yr. After operation, 43.8% of patients developed delirium. By multivariate logistic regression, age [odds ratio (OR) 1.07; 95% confidence interval (CI) 1.02-1.26], dependence on performing one or more independent activities of daily living (OR 1.54; 95% CI 1.01-2.35), use of patient-controlled analgesia for postoperative pain control (OR 3.75; 95% CI 1.27-11.01) and postoperative use of benzodiazepine (OR 2.29; 95% CI 1.21-4.36) were independently associated with an increased risk for postoperative delirium. In contrast, the use of N(2)O had no association with postoperative delirium. CONCLUSIONS: Exposure to N(2)O resulted in an equal incidence of postoperative delirium when compared with no exposure to N(2)O.

Relative importance of preoperative health status versus intraoperative factors in predicting postoperative adverse outcomes in geriatric surgical patients.

OBJECTIVES: To determine the prevalence and predictors of adverse postoperative outcomes in older surgical patients undergoing noncardiac surgery. DESIGN: Prospective cohort study of consecutive patients undergoing noncardiac surgery in 1997. SETTING: A medical school-affiliated teaching community hospital. PARTICIPANTS: Patients age 70 and older undergoing noncardiac surgery. Patients presenting for surgery requiring only local anesthesia or monitored anesthesia care were excluded. MEASUREMENTS: Potential pre- and intra-operative risk factors were measured and evaluated for their association with the occurrence of predefined in-hospital postoperative adverse outcomes. Univariate predictors of postoperative outcomes were first measured using the chi-square or Fisher's exact tests followed by multivariate logistic regression. Odds ratios (OR) with 95% confidence interval (CI), and two-sided P-values were reported. RESULTS: Five hundred forty-four consecutive patients were studied. Overall, 21% of patients developed one or more postoperative adverse outcomes and 3.7% died during the in-hospital postoperative period. Of all the adverse outcomes, cardiovascular complications (10.3%) were the leading cause of morbidity, followed by neurological (7.7%) and pulmonary complications (5.5%). By multivariate logistic regression analysis, American Society of Anesthesiologists (ASA) classification (OR = 2.7, CI = 1.6-4.4), emergency surgery (OR = 2.0, CI = 1.1-3.4), and intraoperative tachycardia (OR = 3.8, CI = 1.9-7.6) were the most important predictors of postoperative adverse outcomes. Of all the preoperative physical symptoms and signs, decreased functional status (OR = 3.0, CI = 1.4-6.4) and clinical signs of congestive heart failure (OR = 2.1, CI = 1.1-5.1) were the two most important predictors of postoperative adverse neurological and cardiac outcomes, respectively. The median hospital stay was 4 days. The patients who developed postoperative adverse outcomes had significantly longer median hospital stays (9 days) than those without complications (3 days), (P < .0001). CONCLUSION: Our study demonstrates that the postoperative mortality rate in geriatric surgical patients undergoing noncardiac surgery is low. Despite the prevalence of preoperative chronic medical conditions, most patients do well postoperatively. The ASA classification (a reflection of the severity of preoperative comorbidities), emergency surgery, and intraoperative tachycardia increase the odds of developing any postoperative adverse events. Future studies aimed at modifying some of the potentially reversible risk factors, such as preoperative heart function and intraoperative heart rate are warranted.

The prevalence and predictors of the use of alternative medicine in presurgical patients in five California hospitals.

UNLABELLED: We measured the prevalence and predictors of the use of alternative medicine supplements in surgical patients by way of a self-administered questionnaire in consecutive patients > or = 18 yr old awaiting elective noncardiac surgery at five San Francisco Bay Area Hospitals. A total of 2560 patients completed the study survey (60% response rate). Of these patients, 39.2% admitted to using some form of alternative medicine supplements, of which herbal medicine was the most common type (67.6%). Of those who admitted to taking alternative medicine supplements, 44.4% did not consult with their primary physicians, and 56.4% did not inform the anesthesiologists before surgery regarding their use of these products; 53% of the patients ceased the use of these products before surgery. Multivariate logistic regression analysis revealed the following variables to be associated with the preoperative use of herbal medicine: female sex (odds radio [OR] 1.42, confidence interval [CI] 1.17-1.72), age 35-49 yr (OR 1.25, CI 1.02-1.53), higher income levels (OR 1.85, CI 1.50-2.27), Caucasian race (OR 1.34, CI 1.07-1.67), higher level of education (OR 1.35, CI 1.10-1.65), problems with sleep (OR 1.32, CI 1.05-1.66), problems with joints or back (OR 1.27, CI 1.04-1.56), allergies (OR 1.48, CI 1.21-1.82), problems with addiction (OR 1.90, CI 1.25-2.89), and a history of general surgery (OR 1.25, CI 1.03-1.52). In contrast, diabetes mellitus (OR 0.55, CI 0.36-0.86) and the use of antithrombotic medications (OR 0.57, CI 0.38-0.87) were associated with decreased odds of the use of herbal medicines. We concluded that the use of alternative medicine supplements by surgical patients is prevalent. Documentation of the use of these products is critical to determine the potential of drug or anesthetic interactions in the perioperative period. IMPLICATIONS: The use of alternative medicine supplements by presurgical patients is prevalent. Documentation of the use of these products is critical to determine the potential of drug or anesthetic interactions in the perioperative period.

The prevalence and predictive value of abnormal preoperative laboratory tests in elderly surgical patients.

UNLABELLED: Because data to determine which preoperative laboratory tests are important in elderly surgical patients are limited, we performed a prospective cohort study to evaluate the prevalence and predictive value of abnormal preoperative laboratory tests in consecutive patients > or =70 yr old who were undergoing noncardiac surgery. Patients presenting for surgery requiring only local anesthesia or monitored anesthesia care were excluded. Preoperative risk factors and laboratory test results were measured and evaluated for their association with the occurrence of predefined in-hospital postoperative adverse outcomes. In 544 patients, the prevalence of preoperative electrolytes and platelet count abnormalities (<115 x10(9)/L) was small (0.5%-5%), and abnormal creatinine (>1.5 mg/dL), hemoglobin (<10 g/dL), and glucose (>200 mg/dL) values were 12%, 10%, and 7%, respectively. Univariate predictors for adverse outcome of abnormal sodium and creatinine were not as predictive as ASA classification and surgical risk. By multivariate logistic regression, only ASA classification (>II) (odds ratio [OR], 2.55; 95% confidence interval [CI], 1.56-4.19; P < 0.001) and surgical risk (OR, 3.48; 95% CI, 2.31-5.23; P < 0.001) were significant independent predictors of postoperative adverse outcomes. The prevalence of abnormal preoperative electrolyte values and thrombocytopenia was small and had low predictive values. Although more prevalent, abnormal hemoglobin, creatinine, and glucose values were also not predictive of postoperative adverse outcomes. Routine preoperative testing for hemoglobin, creatinine, glucose, and electrolytes on the basis of age alone may not be indicated in geriatric patients. Rather, selective laboratory testing, as indicated by history and physical examination, which will determine patient's comorbidities and surgical risk, seems to be indicated. IMPLICATIONS: The prevalence of abnormal preoperative electrolyte values and thrombocytopenia was small and had low predictive values. Although more prevalent, abnormal hemoglobin, creatinine, and glucose values were also not predictive of postoperative adverse outcomes. Routine preoperative testing for hemoglobin, creatinine, glucose, and electrolytes on the basis of age alone may not be indicated in geriatric patients. Rather, selective laboratory testing, as indicated by history and physical examination, which will determine patient's comorbidities and surgical risk, seems to be indicated.

Electrocardiographic ST-segment changes during acute, severe isovolemic hemodilution in humans.

BACKGROUND: Controversy exists regarding the lowest blood hemoglobin concentration that can be safely tolerated. The authors studied healthy resting humans to test the hypothesis that acute isovolemic reduction of blood hemoglobin concentration to 5 g/dl would produce an imbalance in myocardial oxygen supply and demand, resulting in myocardial ischemia. METHODS: Fifty-five conscious healthy human volunteers were studied. Isovolemic removal of aliquots of blood reduced blood hemoglobin concentration from 12.8 +/- 1.2 to 5.2 +/- 0.5 g/dl (mean +/- SD). Removed blood was replaced simultaneously with intravenous fluids to maintain constant isovolemia. Hemodynamics and arterial oxygen content (Cao2) were measured before and after removal of each aliquot of blood. Electrocardiographic (ECG) changes were monitored continuously using a Holter ECG recorder for detection of myocardial ischemia. RESULTS: During hemodilution, transient, reversible ST-segment depression developed in three subjects as seen on the electrocardiogram during hemodilution. These changes occurred at hemoglobin concentrations of 5-7 g/dl while the subjects were asymptomatic. Two of three subjects with ECG changes had significantly higher heart rates than those without ECG changes at the same hemoglobin concentrations. When evaluating the entire study period, the subjects who had ECG ST-segment changes had significantly higher maximum heart rates than those without ECG changes, despite having similar baseline values. CONCLUSION: With acute reduction of hemoglobin concentration to 5 g/dl, ECG ST-segment changes developed in 3 of 55 healthy conscious adults and were suggestive of, but not conclusive for, myocardial ischemia. The higher heart rates that developed during hemodilution may have contributed to the development of an imbalance between myocardial supply and demand resulting in ECG evidence of myocardial ischemia. However, these ECG changes appear to be benign because they were reversible and not accompanied by symptoms.

Predicting adverse postoperative outcomes in patients aged 80 years or older.

OBJECTIVE: The identification of reversible factors that are associated with postoperative morbidity in geriatric surgical patients is critical to improving perioperative outcomes in such patients. Our study aimed to compare the relative importance of intraoperative versus preoperative factors in predicting adverse postoperative outcomes in geriatric patients. DESIGN: Retrospective cohort study of consecutive patients undergoing noncardiac surgery in 1995. SETTING: Two University of California, San Francisco, teaching hospitals--Moffitt/Long and Mount Zion medical centers. PARTICIPANTS: All men and women 80 years of age or older undergoing noncardiac surgery. MEASUREMENTS: Medical records of all patients were reviewed to measure predefined pre- and intraoperative risk factors and postoperative outcomes. Predictors of postoperative outcomes were identified by multivariate logistic regression analyses. RESULTS: Three hundred sixty-seven patients were studied. The most prevalent preoperative risk factors were a history of hypertension and coronary artery, pulmonary, and neurologic diseases. Postoperative in-hospital mortality rate was 4.6%, and 25% of patients developed adverse postoperative outcomes, of which neurological and cardiovascular complications were the leading causes of morbidity (15% and 12%, respectively). By multivariate logistic regression, a history of neurological disease (odds ratio [OR] 4.0, 95% confidence interval [CI] 2.3 - 6.9, P = .0001), congestive heart failure (OR 2.7, 95% CI 1.4 - 5.3, P = .004), and a history of arrhythmia (OR 2.3, 95% CI 1.2 - 4.3, P = .01) increased the odds of adverse postoperative events. The only intraoperative event shown to be predictive of postoperative complications was the use of vasoactive agents (OR 8.0, 95% CI 1.6 - 40.5, P = .009). CONCLUSIONS: In this group of geriatric surgical patients, the overall postoperative in-hospital mortality rate was 4.6%, and 25% of the patients developed adverse postoperative outcomes involving either the neurological, cardiovascular, or pulmonary systems. Intraoperative events appeared to be less important than preoperative comorbidities in predicting adverse postoperative outcomes.

Effects of dobutamine on hemodynamics and left ventricular performance after cardiopulmonary bypass in cardiac surgical patients.

BACKGROUND: Dobutamine is commonly used to improve ventricular performance after cardiopulmonary bypass. The authors determined the effect of dobutamine on hemodynamics and left ventricular performance immediately after cardiopulmonary bypass in patients undergoing coronary artery bypass graft surgery. METHODS: One hundred patients received sequential 3-min infusions of dobutamine at 0-40 microg x kg(-1) x min(-1) immediately after cardiopulmonary bypass. Ten additional patients who received no dobutamine served as controls. Hemodynamics and left ventricular performance (fractional area change by transesophageal echocardiography, stroke volume index, and thermodilution cardiac index) were measured. Mixed-effects modeling accounted for repeated-measures data and interindividual differences and allowed for potential effects of covariates. RESULTS: Heart rate increased in a dose-dependent manner. The slope of HR versus dobutamine dose was steeper in individuals in whom peak dobutamine dose was not reached compared with that in the remaining individuals; slope decreased 2.71 +/- 0.68% per year of age. Dobutamine affected blood pressure minimally, but slightly decreased pulmonary capillary wedge pressure and central venous pressure. Systemic vascular resistance initially increased with dobutamine 10 microg x kg(-1) x min(-1) and remained constant with larger doses. Dobutamine produced a dose-dependent increase in left ventricular performance, primarily by increasing heart rate, because stroke volume index decreased with dobutamine dose. CONCLUSION: Our results suggest that the response to graded dobutamine infusion in the post-cardiopulmonary bypass period differs from that previously reported. After cardiopulmonary bypass, the dominant mechanism by which dobutamine improves left ventricular performance is by increasing heart rate. Dobutamine affects blood pressure minimally.

Automated electrocardiograph ST segment trending monitors: accuracy in detecting myocardial ischemia.

UNLABELLED: Continuous automated ST segment trending devices (ST trending monitors) are included in most new operating room electrocardiography (ECG) monitors to facilitate ischemia detection, but their efficacy is not well validated. Therefore, we compared their accuracy with that of Holter ECG recorders in detecting ST segment changes (both analyzed offline) in 94 patients undergoing coronary artery bypass graft surgery. Holter ECG tapes were analyzed using standard criteria for determining ECG ischemic episodes, which were compared with those measured by the ST trending monitors. Overall, 42 ischemic episodes were detected by using the Holter monitor in 30 patients. Of the 42 episodes, 38 (90%) were also detected by the ST trending monitors. Sixteen episodes of ST segment deviation were detected by the ST trending monitors, but not by the Holter. The sensitivity of the three ST trending monitors in detecting ischemia was 75%, 78%, and 60% for the Marquette (Milwaukee, WI), Hewlett Packard (Andover, MA), and Datex (Helsinki, Finland) monitors, respectively, with a specificity of 89%, 71%, and 69% relative to the Holter. Compared with the HP and Datex monitors, the Marquette monitor has the best agreement with the Holter (K 0.64). Conditions in which ST trending monitors may be inaccurate were identified and included the appearance of small R-wave amplitude, drifting baseline, and during periods of conduction abnormalities and pacing. We conclude that ST trending monitors have only moderate sensitivity and specificity (< 75% overall) in accurately detecting ECG ST segment changes compared with Holter ECG recordings. Therefore, sole reliance on ST trending monitors for the detection of myocardial ischemia may be insufficient. IMPLICATIONS: Using Holter recordings as the reference standard for detection of intraoperative ischemia, ST trending monitors were found to have overall sensitivity and specificity of 74% and 73%, respectively. Several conditions contribute to the inaccuracy of ST trend monitoring, and additional modification of their performance is necessary to achieve better agreement with the Holter analysis.

Dissociation between haemodynamics and sympathetic activation during anaesthetic induction with desfluranes.

PURPOSE: To compare the simultaneous haemodynamic effects, sympathetic activation and cardiac risks associated with desflurane used in a balanced technique, with those of isoflurane anaesthesia. METHODS: A prospective, randomized, open label study was conducted at a University medical centre. Forty patients undergoing major non-cardiac surgery were randomized to receive either desflurane or isoflurane as the primary anaesthetic agent. After premedication, fentanyl and thiopentone were administered i.v.. Anaesthesia was increased up to 1.0 MACET in O2 via controlled mask ventilation and maintained at 1.0 MAC before tracheal intubation. Maintenance consisted of N2O, O2 and desflurane or isoflurane for 10 min. During the study, HR and arterial BP were continuously measured, as were ECG ST-segments and ventricular dysrhythmias using a 3-channel Holter ECG recorder. Left ventricular global and regional function were measured using precordial echocardiography. Serial plasma catecholamine concentrations were measured. RESULTS: For both groups, HR was maintained without increases over baseline values while systolic BP showed a progressive decrease during induction. Use of beta blockade during induction was higher in the desflurane (7/20 = 35%) than in the isoflurane group (1/20 = 5%), P = 0.04. The plasma norepinephrine concentrations progressively increased in the desflurane group but not in the isoflurane group. Four patients in the desflurane and three in the isoflurane group developed transient worsening of regional function but no change in mean left ventricular ejection fraction area and no ECG ischaemia occurred during anaesthetic induction. CONCLUSIONS: Desflurane differs from isoflurane in that sympathetic stimulation persisted despite blunting of potential hyperdynamic haemodynamic responses by narcotic and beta blockade. However, this sympathetic activation did not appear to increase cardiac risks.