Prolonged concurrent hypotension and low bispectral index ('double low') are associated with mortality, serious complications, and prolonged hospitalization after cardiac surgery.

BACKGROUND: Low bispectral index (BIS) and low mean arterial pressure (MAP) are associated with worse outcomes after surgery. We tested the hypothesis that a combination of these risk factors, a 'double low', is associated with death and major complications after cardiac surgery. METHODS: We used data from 8239 cardiac surgical patients from two US hospitals. The primary outcomes were 30-day mortality and a composite of in-hospital mortality and morbidity. We examined whether patients who had a case-averaged double low, defined as time-weighted average BIS and MAP (calculated over an entire case) below the sample mean but not in the reference group, had increased risk of the primary outcomes compared with patients whose BIS and/or MAP were at or higher than the sample mean. We also examined whether a prolonged cumulative duration of a concurrent double low (simultaneous low MAP and BIS) increased the risk of the primary outcomes. RESULTS: Case-averaged double low was not associated with increased risk of 30-day mortality {odds ratio [OR] 1.73 [95% confidence interval (CI) 0.94-3.18] vs reference; P =0.01} or the composite of in-hospital mortality and morbidity [OR 1.47 (95% CI 0.98-2.20); P =0.01] after correction for multiple outcomes. A prolonged concurrent double low was associated with 30-day mortality [OR 1.06 (95% CI 1.01-1.11) per 10-min increase; P =0.001] and the composite of in-hospital mortality and morbidity [OR 1.04 (95% CI 1.01-1.07), P =0.004]. CONCLUSIONS: A prolonged concurrent double low, but not a case-averaged double low, was associated with higher morbidity and mortality after cardiac surgery.

Intraoperative arterial blood pressure lability is associated with improved 30 day survival.

BACKGROUND: Arterial blood pressure lability, defined as rapid changes in arterial blood pressure, occurs commonly during anaesthesia. It is believed that hypertensive patients exhibit more lability during surgery and that lability is associated with poorer outcomes. Neither association has been rigorously tested. We hypothesized that hypertensive patients have more blood pressure lability and that increased lability is associated with increased 30 day mortality. METHODS: This was a retrospective single-centre study of surgical patients from July 2008 to December 2012. Intraoperative data were extracted from the electronic anaesthesia record. Lability was calculated as the modulus of the percentage change in mean arterial pressure between consecutive 5 min intervals. The number of episodes of lability >10% was tabulated. Multivariate logistic regression was performed to determine the association between lability and 30 day mortality using derivation and validation cohorts. RESULTS: Inclusion criteria were met by 52 919 subjects. Of the derivation cohort, 53% of subjects were hypertensive and 42% used an antihypertensive medication. The median number of episodes of lability >10% was 9 (interquartile range 5-14) per patient. Hypertensive subjects demonstrated more lability than normotensive patients, 10 (5-15) compared with 8 (5-12), P<0.0001. In subjects taking no antihypertensive medication, lability >10% was associated with decreased 30 day mortality, odds ratio (OR) per episode 0.95 [95% confidence interval (CI) 0.92-0.97], P<0.0001. This result was confirmed in the validation cohort, OR 0.96 (95% CI 0.93-0.99), P=0.01, and in hypertensive patients taking no antihypertensive medication, OR 0.96 (95% CI 0.93-0.99), P=0.002. Use of any antihypertensive medication class reduced this effect. CONCLUSIONS: Intraoperative arterial blood pressure lability occurs more often in hypertensive patients. Contrary to common belief, increased lability was associated with decreased 30 day mortality.

Association of intraoperative blood pressure instability with adverse outcomes after liver transplantation.

BACKGROUND: Blood pressure derangements are common in orthotopic liver transplantation (OLT), and are potentially associated with adverse outcomes if they are sustained. While this concept is often believed to be true, few have rigorously demonstrated the validity of this claim, especially in likely vulnerable OLT patients. METHODS: We retrospectively investigated 827 patients who underwent OLT to determine the magnitude of these hemodynamic associations with adverse outcomes. The median value of the mean arterial pressure (MAP) and the fractional change in the median MAP between subsequent epochs (FCM) were calculated for every 5-minute epoch intraoperatively. Epochs were classified according to prespecified ranges of MAP and fractional changes in MAP (lability) between epochs. Multivariate stepwise logistic regression was used to model associations of risk factors and epochs of intraoperative blood pressure (BP) instability with primary (30-day mortality and/or graft failure) and secondary adverse outcomes. RESULTS: Primary adverse outcomes occurred in 10.9% and 12.2% of patients for 30-day mortality and 30-day graft failure, respectively. Independent hemodynamic predictors for 30-day mortality and graft failure included sustained periods of MAP <50 mmHg and BP lability where the MAP changed >25%. All of these values were statistically significant. CONCLUSION: Although severe intraoperative hypotension and BP lability during OLT are often observed in current practice as consequences of major surgical manipulations and patient vulnerability, these are likely not benign conditions based on this retrospective analysis. Prospective trials are warranted to investigate the possibility that interventions tailored to avoidance of hypotension and BP lability may improve outcomes.

Influence of increased left ventricular myocardial mass on early and late mortality after cardiac surgery.

BACKGROUND: Increased left ventricular mass (LVM) is a well-recognized predictor of cardiovascular morbidity and mortality in epidemiological studies, but its impact on mortality after cardiac surgery is poorly defined. We hypothesized that patients with increased LVM index (LVMI) were more likely to have greater 30 day and 1 yr mortality. METHODS: With IRB approval, intraoperative transoesophageal echocardiography images of 844 cardiac surgical patients were reviewed. LVMI was calculated using the American Society of Echocardiography recommended formula. Outcome variables studied were 30 day and 1 yr mortality. RESULTS: Mortality within 30 days occurred in 28 patients (3.3%) and within 1 yr in 91 patients (10.8%). An almost linear relationship was found between increasing LVMI and the risk of mortality within 30 days of cardiac surgery. The odds ratio (OR) of dying within 30 days of surgery was 1.15 (95% confidence interval 1.01-1.31) per 20 g m(-2) increase in LVMI. This finding remained statistically significant in multivariate analysis controlling for the effects of age, weight, gender, surgery type, LV function, and functional status [OR=1.36 (1.11-1.66) per 20 g m(-2) increase]. Increased LVMI was not found to be a statistically significant predictor of 1 yr mortality. CONCLUSIONS: Increased LVMI, but not LV systolic function as measured by the fractional area of contraction (FAC) was identified as a strong independent predictor of perioperative mortality after adult cardiac surgery. The relationship between LVMI and risk of 30 day mortality was nearly linear. Furthermore, decreased FAC, and not LVMI, was a strong independent predictor of 1 yr mortality.

Implementation of a standards-based anaesthesia record compliant with the health level 7 (HL7) clinical document architecture (CDA).

With the increasing use of anaesthesia information management systems (AIMS) there is the opportunity for different institutions to aggregate and share information both nationally and internationally. Potential uses of such aggregated data include outcomes research, benchmarking and improvement in clinical practice and patient safety. However, these goals can only be achieved if data contained in records from different sources are truly comparable and there is semantic inter-operability. This paper describes the development of a standard terminology for anaesthesia and also a Domain Analysis Model and implementation guide to facilitate a standard representation of AIMS records as extensible markup language documents that are compliant with the Health Level 7 Version 3 clinical document architecture. A representation of vital signs that is compliant with the International Standards Organization 11073 standard is also discussed.

Mathematical model for describing cerebral oxygen desaturation in patients undergoing deep hypothermic circulatory arrest.

BACKGROUND: Surgical treatment for aortic arch disease requiring periods of circulatory arrest is associated with a spectrum of neurological sequelae. Cerebral oximetry can non-invasively monitor patients for cerebral ischaemia even during periods of circulatory arrest. We hypothesized that cerebral desaturation during circulatory arrest could be described by a mathematical relationship that is time-dependent. METHODS: Cerebral desaturation curves obtained from 36 patients undergoing aortic surgery with deep hypothermic circulatory arrest (DHCA) were used to create a non-linear mixed model. The model assumes that the rate of oxygen decline is greatest at the beginning before steadily transitioning to a constant. Leave-one-out cross-validation and jackknife methods were used to evaluate the validity of the predictive model. RESULTS: The average rate of cerebral desaturation during DHCA can be described as: Sct(o(2))[t]=81.4-(11.53+0.37 x t) (1-0.88 x exp (-0.17 x t)). Higher starting Sct(o(2)) values and taller patient height were also associated with a greater decline rate of Sct(o(2)). Additionally, a predictive model was derived after the functional form of a x log (b+c x delta), where delta is the degree of Sct(o(2)) decline after 15 min of DHCA. The model enables the estimation of a maximal acceptable arrest time before reaching an ischaemic threshold. Validation tests showed that, for the majority, the prediction error is no more than +/-3 min. CONCLUSIONS: We were able to create two mathematical models, which can accurately describe the rate of cerebral desaturation during circulatory arrest at 12-15 degrees C as a function of time and predict the length of arrest time until a threshold value is reached.

A survey of anesthesiologists' and nurses' attitudes toward the implementation of an Anesthesia Information Management System on a labor and delivery floor.

BACKGROUND: An anesthesia information management system (AIMS) is most frequently used in the operating room, but not on labor and delivery (L&D). The purpose of this study is to describe the implementation of an AIMS on L&D and the attitudes of practitioners (anesthesiologists and nurses) toward the system. METHODS: The anesthesiology survey focused on satisfaction with the L&D AIMS, comparison of the L&D AIMS with a handwritten anesthesia record, and comparison of the L&D AIMS with the operating room AIMS. The nursing survey focused on nursing satisfaction with the L&D AIMS and comparison of the L&D AIMS with a handwritten anesthesia record. RESULTS: Most anesthesiologists (76%) were satisfied with the L&D AIMS and 73% would not want to revert back to the paper record. However, most anesthesiologists felt the operating room AIMS was either superior or equal to the L&D AIMS. Although few nurses (4%) preferred the anesthesiologists revert back to the handwritten record overall, the nurses were neutral in their assessment of the AIMS. Most of the criticism related to the location of the system; 56% believed it was not in a convenient location and 74% thought the AIMS equipment "got in their way". CONCLUSIONS: Overall, the anesthesiologists and nurses are satisfied with the L&D AIMS and would not want to switch back to a handwritten record. We conclude that AIMS should not be limited to the operating room setting and can successfully be used in L&D.

Application of fuzzy functions for visual presentation of medical data.

While interpretation of medical data is very often an ambiguous process, computers usually display results of recommendations, provided by both human experts and computer algorithms, as concrete data. This study proposes a visual presentation of relative degrees of uncertainty along with "standard" concrete medical data. A medical parameter (mean arterial pressure) is dynamically evaluated during surgery for being too low or too high. Fuzzy membership functions are utilized to display degrees of deviation in the form of a clear and concise pie chart. Thus, in the Operating Room the anesthesiologist can be provided with an easy statistical assessment of uncertainty of existing recommendations.

Retrograde cerebral perfusion as a method of neuroprotection during thoracic aortic surgery.

Retrograde cerebral perfusion is commonly used as an adjunct to hypothermic circulatory arrest to enhance cerebral protection during thoracic aortic surgery. This review summarizes a large number of studies that demonstrate a spectrum of beneficial, neutral, and detrimental effects of retrograde cerebral perfusion in humans and experimental animal models. It remains unclear whether retrograde cerebral perfusion provides effective cerebral perfusion, metabolic support, washout of embolic material, and improved neurological and neuropsychological outcome.

Decreased endotoxin immunity is associated with greater mortality and/or prolonged hospitalization after surgery.

BACKGROUND: Patients undergoing noncardiac surgery often develop postoperative morbidity, potentially attributable to endotoxemia and the systemic inflammatory response syndrome. Endogenous antibodies to endotoxin may confer protection from endotoxin-mediated toxicity. The authors sought to determine the association of preoperative antiendotoxin immunity and death or prolonged hospitalization in a broad population of general surgical patients undergoing major surgery. METHODS: To test the hypothesis that low preoperative serum antiendotoxin core antibody (EndoCAb) concentration is an independent predictor of adverse outcome after general surgery, 1,056 patients undergoing routine noncardiac surgery were enrolled into a prospective, blinded, cohort study. Immunoglobulin M EndoCAb, immunoglobulin G EndoCAb, total inmunoglobulin M, and immunoglobulin G concentrations were measured in serum obtained preoperatively. A physiologic risk score using the established POSSUM criteria was assigned preoperatively to each patient. The primary predefined composite end point (postoperative complication) was either in-hospital death or postoperative length of stay greater than 10 days. Multivariate logistic regression was used to test the study hypothesis. RESULTS: Overall, postoperative complication occurred in 234 of the 1,056 patients (22.1%). Lower immunoglobulin M EndoCAb concentration (P = 0.006) predicted increased risk of postoperative complication independent of POSSUM physiologic risk score (P < 0.001). In contrast, total immunoglobulin M and total immunoglobulin G concentrations did not predict adverse outcome. Complications involved multiple organ systems and were generally unrelated to the type or site of surgery, consistent with the systemic inflammatory response syndrome. CONCLUSIONS: Adverse outcome after routine noncardiac surgery is common and is predicted in part by low concentrations of EndoCAb. The authors' findings suggest that endotoxemia may be a cause of postoperative morbidity after routine noncardiac surgery.

Retrograde cerebral perfusion during thoracic aortic surgery and late neuropsychological dysfunction.

OBJECTIVE: Retrograde cerebral perfusion (RCP) is commonly used in thoracic aortic surgery, ostensibly to provide metabolic support, maintain cerebral hypothermia and/or wash out particulate emboli. We tested the hypothesis that RCP would affect neuropsychological outcome in a clinical cohort. METHODS: Ninety-four patients undergoing elective thoracic aortic repairs requiring deep hypothermic circulatory arrest consented to participate in this study. These patients underwent preoperative neuropsychological evaluation and comprise the reference group. Fifty-six of these patients also underwent neuropsychological evaluation several weeks postoperatively, 12 of whom (21%) had RCP. The neuropsychological domains tested were attention, processing speed, memory, executive function, and fine motor function. A global assessment of impairment, negative neuropsychological outcome (NNO), was defined as a postoperative decrease in function in two or more neuropsychological domains for patients with at least three domains tested both pre- and postoperatively (n=48). The relationship of three potential predictors (RCP, cerebral ischemia time and patient age) to negative outcomes was analyzed using Wilcoxon two-sample tests, chi(2) tests, Mantel-Haenszel tests and multiple logistic regression. P<0.05 was considered significant. RESULTS: Memory dysfunction and NNO had strong associations with RCP. This effect remained significant when controlling separately for age and cerebral ischemia time. CONCLUSIONS: The effects of RCP are difficult to distinguish from those of age and prolonged cerebral ischemia time, because complex thoracic aortic repairs are associated with advanced age, prolonged cerebral ischemia and use of RCP. Despite this limitation, these preliminary data indicated that RCP had no beneficial effect (and most likely a negative effect) upon cognitive outcome.

Development of a decision support system to assist anesthesiologists in operating room.

The complexity of modern anesthesia procedures requires the development of decision-support systems functioning in a smart-alarm capacity. We developed computer algorithms to detect critical conditions during surgery (light anesthesia or unstable blood pressure), based on computerized anesthesia records containing hemodynamic data (heart rate, mean arterial pressure and systolic arterial pressure). Our analysis indicated that a > or = 12% change in mean arterial blood pressure (MAP), compared with the median value of MAP over the preceding 10-min interval, may be chosen as the criterion for detecting LA, with a sensitivity of 96% and a specificity of 91%. The best agreement between human and computer ratings of blood pressure lability (correlation coefficient 0.78) was achieved when we used the absolute value of the fractional change of the mean arterial pressure (magnitude of FCM) between one 2-min epoch and the next 2-min epoch. Work is under progress to develop a decision-support system to alert clinicians in the operating room environment to critical events.

Arterial blood pressure and heart rate discrepancies between handwritten and computerized anesthesia records.

UNLABELLED: Previous publications suggest that handwritten anesthesia records are less accurate when compared with computer-generated records, but these studies were limited by small sample size, unblinded study design, and unpaired statistical comparisons. Eighty-one pairs of handwritten and computer-generated neurosurgical anesthesia records were retrospectively compared by using a matched sample design. Systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate (HR) data for each 5-min interval were transcribed from handwritten records. In computerized records, the median of up to 20 values was calculated for SAP, DAP, and HR for each consecutive 5-min epoch. The peak, trough, standard deviation, median, and absolute value of the fractional rate of change between adjacent 5-min epochs were calculated for each case. Pairwise comparisons were performed by using Wilcoxon tests. For SAP, DAP, and HR, the handwritten record peak, standard deviation, and fractional rate of change were less than, and the trough and median were larger than, those in corresponding computer records (all with P: < 0.05, except DAP median and HR peak). Considering together all the recorded measurements from all cases, extreme values were recorded more frequently in computerized records than in the handwritten records. IMPLICATIONS: The discrepancies between handwritten and computerized anesthesia records suggest that some of the data in handwritten records are inaccurate. The potential for inaccuracy should be considered when handwritten records are used as source material for research, quality assurance, and medicolegal purposes.

Beneficial effects from beta-adrenergic blockade in elderly patients undergoing noncardiac surgery.

BACKGROUND: Perioperative beta-blockade has been shown to improve long-term cardiac outcome in noncardiac surgical patients. A possible mechanism for the reduced risk of perioperative myocardial infarction is the attenuation of the excitotoxic effects of catecholamine surges by beta-blockade. It was hypothesized that beta-blocker-induced alteration of the stress response was responsible for the reported improvements in cardiovascular outcome. Several variables associated with the perioperative use of beta-blockade were also evaluated. METHODS: Sixty-three patients were randomly assigned to one of three groups: group I, no atenolol; group II, pre- and postoperative atenolol; group III, intraoperative atenolol. Hormonal markers of the stress response (neuropeptide Y, epinephrine, norepinephrine, cortisol, and adrenocorticotropic hormone) were evaluated preoperatively and for 72 h after surgery. RESULTS: Perioperative beta-blockade did not significantly alter the hormonal stress response. However, the beta-blocked patients showed improved hemodynamic stability during emergence and postoperatively. They also received less fentanyl intraoperatively (27.7%, P < 0.0001), experienced faster early recovery, had lower pain scores, and required less analgesia in the postanesthesia care unit. Cardiac troponin I release was detected in 8 of 19, 4 of 20, and 5 of 20 patients in groups I, II, and III, respectively (not significant). Three patients in group I had cardiac troponin I levels consistent with myocardial infarction. CONCLUSION: Beta-blockade does not reduce the neuroendocrine stress response, suggesting that this mechanism is not responsible for the previously reported improved cardiovascular outcome. However, it confers several advantages, including decreased analgesic requirements, faster recovery from anesthesia, and improved hemodynamic stability. The release of cardiac troponin I suggests the occurrence of perioperative myocardial damage in this elderly population, which appears to be independent of the neuroendocrine stress response.

Descending thoracic and thoracoabdominal aneurysm.

The low incidence of permanent spinal cord injury in our most recent cohort (Group II) of patients suggests that serial sacrifice of intersegmental vessels, careful monitoring of spinal cord function are effective in preventing paraplegia after descending thoracic and thoracoabdominal aneurysm operations. Updated anesthetic and postoperative care minimized overall mortality risk. (Ref. 9.)

Intraoperative hemodynamic predictors of mortality, stroke, and myocardial infarction after coronary artery bypass surgery.

UNLABELLED: Evidence that intraoperative hemodynamic abnormalities influence outcome is limited. The purpose of this study was to determine whether intraoperative hemodynamic abnormalities were associated with mortality, stroke, or perioperative myocardial infarction (PMI) in a large cohort of patients undergoing coronary artery bypass grafting. Risk factors and outcomes were queried from a state-mandated cardiac surgery reporting system at two hospitals in New York, NY. Intraoperative hemodynamic abnormalities were derived from computerized anesthesia records by assessing the duration of exposure to moderate or severe extremes of hemodynamic variables. Multivariate logistic regression identified independent predictors of perioperative mortality, stroke, and PMI. Among 2149 patients, there were 50 mortalities, 51 strokes, and 85 PMIs. In the precardiopulmonary bypass (pre-CPB) period, pulmonary hypertension was a predictor of mortality (odds ratio [OR] 2.1, P = 0.029), and bradycardia and tachycardia were predictors of PMI (OR 2.9, P = 0.007 and OR 2.0, P = 0.028, respectively). During CPB, hypotension was a predictor of mortality (OR 1.3, P = 0.025). Post-CPB, tachycardia was a predictor of mortality (OR 3.1, P = 0.001), diastolic arterial hypertension was a predictor of stroke (OR 5.4, P = 0.012), and pulmonary hypertension was a predictor of PMI (OR 7.0, P < 0.001). Increased pulmonary arterial diastolic pressure post-CPB was a predictor of mortality (OR 1.2, P = 0.004), stroke (OR 3.9, P = 0.002), and PMI (OR 2.2, P = 0.001). Rapid intraoperative variations in blood pressure and heart rate were not independent predictors of these outcomes. These findings demonstrate the prognostic significance of intraoperative hemodynamic abnormalities, including data from pulmonary artery catheterization, to adverse postoperative outcomes. It is not known whether interventions to control these variables would improve outcome. IMPLICATIONS: Intraoperative hemodynamic abnormalities, including pulmonary hypertension, hypotension during cardiopulmonary bypass, and postcardiopulmonary bypass pulmonary diastolic hypertension, were independently associated with mortality, stroke, and perioperative myocardial infarction over and above the effects of other preoperative risk factors.

Object-oriented analysis and design of a health care management information system.

We have created a prototype for a universal object-oriented model of a health care system compatible with the object-oriented approach used in version 3.0 of the HL7 standard for communication messages. A set of three models has been developed: (1) the Object Model describes the hierarchical structure of objects in a system--their identity, relationships, attributes, and operations; (2) the Dynamic Model represents the sequence of operations in time as a collection of state diagrams for object classes in the system; and (3) functional Diagram represents the transformation of data within a system by means of data flow diagrams. Within these models, we have defined major object classes of health care participants and their subclasses, associations, attributes and operators, states, and behavioral scenarios. We have also defined the major processes and subprocesses. The top-down design approach allows use, reuse, and cloning of standard components.