Bispectral index (BIS) monitoring of ICU patients on continuous infusion of sedatives and paralytics reduces sedative drug utilization and cost

Abstract

The awareness of the diagnostic difficulty and the documented high mortality risk of perioperative myocardial infarction (PMI) has led to the wide use of work up to rule out PMI after major noncardiac operations. This has caused stable postoperative patients to be kept in monitored hospital beds for extended periods of time and to be subjected to additional tests. We hypothesized that the mortality of PMI is high and, therefore, the wide use of postoperative work up to identify these patients is justifiable. We performed the following study to prove our hypothesis. All patients in the recovery room after major noncardiac operations who underwent work up to rule out PMI were identified and followed. The PMI work up included care in an electronically monitored unit, physical assessment, continuous ECG monitoring, and three 12-lead electrocardiograms and cardiac enzymes obtained at six to eight hour intervals. Data collection included patient demographics; preoperative cardiac risk factors; incidence of intraoperative hypotension, hemorrhage and ECG changes; type of anesthesia and operative procedures and their durations; postoperative ECG and cardiac enzyme results; the incidence of PMI and patient outcome. Two hundred patients were studied; 85 males and 115 females. Their mean age was 62.9 years. Preexisting conditions included hypertension in 162 patients, peripheral arterial disease in 102, diabetes mellitus in 97, angina in 30, previous myocardial infarction in 41, and smoking in 107. Of 200 patients, 164 had an abnormal preoperative ECG. Vascular operations were performed in 104 patients, nonvascular abdominal operations in 48, and other operations in the remaining 48. Intraoperatively, hypotension occurred in 29 patients, blood loss of >500 ml in 25 and ECG changes in 10. There were no deaths. PMI occurred in 5/200 (2.5%) patients. Four had undergone vascular operations and one had had an abdominal operation. The mean age of the patients with PMI was 64.2 years. The duration of operation and blood loss were similar to those of patients without PMI. None of these patients developed cardiac failure or cardiogenic shock and none of them died. Conclusion: The incidence of PMI among patients undergoing noncardiac surgery is low and its mortality is negligible. Physicians should become more selective in the use of monitored beds and in the ordering of a work up to rule out PMI. Aims: To study the relationship between myocardial release of cTnI and myocardial cell death as assessed by the amount of apoptosis and necrosis after cardiac surgery. Methods: Eighteen young pigs were operated on with standardized cardiopulmonary bypass (CPB). Release of cTnI in the cardiac lymph (CL), coronary sinus (CS), and arterial blood (A) was related to postoperative myocardial cell death by both necrosis and apoptosis. Apoptotic cells were detected by a TUNEL detection kit. Necrotic cells were counted by light microscopy. Results: In all animals, cTnI was significantly released and reached peak values observed simultaneously in A (cTnI, 20.1±2.6 ng/ml) (mean ±SEM), CS (19.5±3.2 ng/ml) and CL (5202±2500 ng/ml). Percentage of total myocardial cell death was 3.1±0.5%, including 1.2±0.35% necrosis and 1.9±0.5% apoptosis. cTnI release during and after CPB did not correlate with the degree of myocardial apop-tosis or necrosis. Conclusion: Cardiac operations with CPB are related to myocardial cell damage including myocardial cell death due to both necrosis and apoptosis. As the loss of cTnI is not related to the amount of cell death, our results suggest that increased cardiac myocyte membrane permeability more than cell death is responsible for intraoperative and postoperative cTnI release. It is common to evaluate patients with acute myocardial infarction (AMI) according to the Forrester classification. A high PCWP value is a good predictor of pulmonary congestion although there is no documented correlation between PCWP and the degree of pulmonary congestion in patients with normal PCWP. In this study, we sought to investigate the correlation between (1) PCWP and tho-racic fluid contents (TFC) as an indicator of pulmonary congestion, (2) PCWP and cardiac index (CI) and (3) CI and TFC in patients with AMI with PCWP values <18mmHg. The thoracic electrical bioimpedance (TEB) method was used to measure TFC and CI. CI was also measured by the thermodilution (TD) method. Thirty-six patients with a diagnosis of AMI were included. Patients were monitored with the TEB device (BioZ System, CardioDynamics International Co, USA) and the pulmonary artery (PA) catheter, in addition to conventional monitoring. We measured CI by means of TEB and ther-modilution (TD) methods (CI-TEB and CI-TD, respectively) and compared values obtained from each patient with those two methods. We also measured PCWP with the PA catheter, and TFC values as an indicator of pulmonary congestion with the TEB device. The correlation between PCWP and CI, PCWP and TFC, CI and TFC were also examined. Patients were 29 males and 7 females and age was 65±11 years (mean ±SD). All the patients had AMI in the left ventricle. CI-TEB and CI-TD were positively correlated (r 2 =0.75). CI-TD was inversely correlated with PCWP (r 2 =0.22). TFC was weakly correlated with PCWP (r 2 =0.26). Neither CI-TEB nor CI-TD had significant correlation with TFC (r 2 =0.01 and 0.02, respectively). In this study, we confirmed that TEB method might be clinically useful for CI measurement in patients with AMI. PCWP was negatively correlated with CI-TD indicating that decreased CI in our patient group was not due to sys-temic dehydration but to decreased cardiac contractility. The weak correlation between PCWP and TFC means that the tendency of pulmonary water retention exists with an increasing PCWP even in patients with normal PCWP. The clinical importance of this increase in TFC is not clear. TFC values had no significant correlation with CI values. This means that the degree of pulmonary congestion is unpredictable from CI provided that PCWP remains normal. This is consistent with the Forrester classification.