A prospective evaluation of the incidence of adverse events in nurse-administered moderate sedation guided by sedation scores or Bispectral Index.

BACKGROUND: Moderate sedation is routinely performed in patients undergoing minor therapeutic and diagnostic procedures outside the operating room. The level of sedation is often monitored by sedation nurses using clinical criteria, such as sedation scores. The Bispectral Index (BIS) is derived from changes in the electroencephalograph profile that may provide an objective measure of the level of sedation. In this prospective observational study, we investigated whether using BIS values to guide sedative drug administration influences the level of sedation and the incidence of adverse events compared with using Ramsay sedation scale (RSS) only in nurse-administered moderate sedation. We hypothesized that both depth of sedation and the incidence of adverse events related to oversedation would decrease when sedation nurses used BIS values to help guide sedative drug administration. METHODS: Sedation care was provided by trained sedation nurses under the supervision of a physician performing the procedure. The sedation regimen was initiated with IV midazolam 1 to 2 mg and fentanyl 50 mcg or hydromorphone 0.2 mg. Additional small boluses of midazolam, fentanyl, or hydromorphone were administered to maintain an RSS of 2 to 3 (cooperative, oriented, and responding to verbal command). Propofol was not used. Information including patient demographics, type of procedure, medication administered, RSS, and rates of adverse events was recorded by the sedation nurses for each patient on a computer-readable form. The study was divided into 3 phases. In phase 1 (baseline, 6 months' duration), baseline data on sedation practice were prospectively collected. There was no change from standard of care for all patients except that each patient had a BIS sensor attached, but the monitor was covered and nurses were blinded to the BIS values. In phase 2 (training, 3 months), the sedation nurses received comprehensive education on the use of BIS to guide sedative drug administration, pharmacology of commonly used drugs, and methods for rescue from oversedation. The recommended BIS range for moderate sedation was 75 to 90. Adequate training of all sedation nurses on the use of BIS was documented. In phase 3 (implementation, 6 months), the BIS values were used to guide drug administration. RESULTS: Data were available on 1766 patients (999 and 767 patients in phases 1 and 3, respectively). Most of the procedures were colonoscopies, upper gastrointestinal endoscopies, examinations under anesthesia, endoscopic retrograde cholangiopancreatography, and central venous access catheter placements. No differences in the demographics between the 2 groups were observed. The RSS was inversely associated with the BIS value, r = -0.16 (95% confidence interval, -0.19 to -0.12; P < 0.00001). An RSS of 2 to 3 was maintained in 94% of patients in phase 1 and 96% of patients in phase 3 The mean (±SD) BIS values were 80.9 ± 6.8 in phase 1 and 80.4 ± 6.5 in phase 3. The number of sedation-related adverse events was lower in our sample when BIS was used, with an odds ratio of 0.41 (95% confidence interval, 0.28-0.62; P < 0.0001), and patients with restlessness had a lower BIS value than those without this symptom (P < 0.0001). No serious adverse events or deaths were reported. CONCLUSIONS: Nurse-administered moderate sedation using midazolam and fentanyl was usually associated with appropriate levels of sedation as assessed by both the RSS and BIS with an overall low incidence of adverse events. The use of BIS did not change the mean level of sedation significantly, although the number of sedation-related adverse events appears to be lower when BIS was used.

Validation of a stand-alone near-infrared spectroscopy system for monitoring cerebral autoregulation during cardiac surgery.

BACKGROUND: Individualizing arterial blood pressure (ABP) targets during cardiopulmonary bypass (CPB) based on cerebral blood flow (CBF) autoregulation monitoring may provide a more effective means for preventing cerebral hypoperfusion than the current standard of care. Autoregulation can be monitored in real time with transcranial Doppler (TCD). We have previously demonstrated that near-infrared spectroscopy (NIRS)-derived regional cerebral oxygen saturation (rS(c)O(2)) provides a clinically suitable surrogate of CBF for autoregulation monitoring. The purpose of this study was to determine the accuracy of a stand-alone "plug-and-play" investigational system for autoregulation monitoring that uses a commercially available NIRS monitor with TCD methods. METHODS: TCD monitoring of middle cerebral artery CBF velocity and NIRS monitoring were performed in 70 patients during CPB. Indices of autoregulation were computed by both a personal computer-based system and an investigational prototype NIRS-based monitor. A moving linear correlation coefficient between slow waves of ABP and CBF velocity (mean velocity index [Mx]) and between ABP and rS(c)O(2) (cerebral oximetry index [COx]) were calculated. When CBF is autoregulated, there is no correlation between CBF and ABP; when CBF is dysregulated, Mx and COx approach 1 (i.e., CBF and ABP are correlated). Linear regression and bias analysis were performed between time-averaged values of Mx and COx derived from the personal computer-based system and from COx measured with the prototype monitor. Values for Mx and COx were categorized in 5 mm Hg bins of ABP for each patient. The lower limit of CBF autoregulation was defined as the ABP where Mx incrementally increased to ≥0.4. RESULTS: There was correlation and good agreement between COx derived from the prototype monitor and Mx (r = 0.510; 95% confidence interval, 0.414-0.595; P < 0.001; bias, -0.07 ± 0.19). The correlation and bias between the personal computer-based COx and the COx from the prototype NIRS monitor were r = 0.957 (95% confidence interval, 0.945-0.966; P < 0.001 and 0.06 ± 0.06, respectively). The average ABP at the lower limit of autoregulation was 63 ± 11 mm Hg (95% prediction interval, 52-74 mm Hg). Although the mean ABP at the COx-determined lower limit of autoregulation determined with the prototype monitor was statistically different from that determined by Mx (59 ± 9 mm Hg; 95% prediction interval, 50-68 mm Hg; P = 0.026), the difference was not likely clinically meaningful. CONCLUSIONS: Monitoring CBF autoregulation with an investigational stand-alone NIRS monitor is correlated and in good agreement with TCD-based methods. The availability of such a device would allow widespread autoregulation monitoring as a means of individualizing ABP targets during CPB.

Hospital stay and mortality are increased in patients having a "triple low" of low blood pressure, low bispectral index, and low minimum alveolar concentration of volatile anesthesia.

BACKGROUND: Low mean arterial pressure (MAP) and deep hypnosis have been associated with complications and mortality. The normal response to high minimum alveolar concentration (MAC) fraction of anesthetics is hypotension and low Bispectral Index (BIS) scores. Low MAP and/or BIS at lower MAC fractions may represent anesthetic sensitivity. The authors sought to characterize the effect of the triple low state (low MAP and low BIS during a low MAC fraction) on duration of hospitalization and 30-day all-cause mortality. METHODS: Mean intraoperative MAP, BIS, and MAC were determined for 24,120 noncardiac surgery patients at the Cleveland Clinic, Cleveland, Ohio. The hazard ratios associated with combinations of MAP, BIS, and MAC values greater or less than a reference value were determined. The authors also evaluated the association between cumulative triple low minutes, and excess length-of-stay and 30-day mortality. RESULTS: Means (±SD) defining the reference, low, and high states were 87 ± 5 mmHg (MAP), 46 ± 4 (BIS), and 0.56 ± 0.11 (MAC). Triple lows were associated with prolonged length of stay (hazard ratio 1.5, 95% CI 1.3-1.7). Thirty-day mortality was doubled in double low combinations and quadrupled in the triple low group. Triple low duration ≥60 min quadrupled 30-day mortality compared with ≤15 min. Excess length of stay increased progressively from ≤15 min to ≥60 min of triple low. CONCLUSIONS: The occurrence of low MAP during low MAC fraction was a strong and highly significant predictor for mortality. When these occurrences were combined with low BIS, mortality risk was even greater. The values defining the triple low state were well within the range that many anesthesiologists tolerate routinely.

Broadly applicable risk stratification system for predicting duration of hospitalization and mortality.

BACKGROUND: Hospitals are increasingly required to publicly report outcomes, yet performance is best interpreted in the context of population and procedural risk. We sought to develop a risk-adjustment method using administrative claims data to assess both national-level and hospital-specific performance. METHODS: A total of 35,179,507 patient stay records from 2001-2006 Medicare Provider Analysis and Review (MEDPAR) files were randomly divided into development and validation sets. Risk stratification indices (RSIs) for length of stay and mortality endpoints were derived from aggregate risk associated with individual diagnostic and procedure codes. Performance of RSIs were tested prospectively on the validation database, as well as a single institution registry of 103,324 adult surgical patients, and compared with the Charlson comorbidity index, which was designed to predict 1-yr mortality. The primary outcome was the C statistic indicating the discriminatory power of alternative risk-adjustment methods for prediction of outcome measures. RESULTS: A single risk-stratification model predicted 30-day and 1-yr postdischarge mortality; separate risk-stratification models predicted length of stay and in-hospital mortality. The RSIs performed well on the national dataset (C statistics for median length of stay and 30-day mortality were 0.86 and 0.84). They performed significantly better than the Charlson comorbidity index on the Cleveland Clinic registry for all outcomes. The C statistics for the RSIs and Charlson comorbidity index were 0.89 versus 0.60 for median length of stay, 0.98 versus 0.65 for in-hospital mortality, 0.85 versus 0.76 for 30-day mortality, and 0.83 versus 0.77 for 1-yr mortality. Addition of demographic information only slightly improved performance of the RSI. CONCLUSION: RSI is a broadly applicable and robust system for assessing hospital length of stay and mortality for groups of surgical patients based solely on administrative data.

Anesthetic management and one-year mortality after noncardiac surgery.

Little is known about the effect of anesthetic management on long-term outcomes. We designed a prospective observational study of adult patients undergoing major noncardiac surgery with general anesthesia to determine if mortality in the first year after surgery is associated with demographic, preoperative clinical, surgical, or intraoperative variables. One-year mortality was 5.5% in all patients (n = 1064) and 10.3% in patients > or =65 yr old (n=243). Multivariate Cox Proportional Hazards modeling identified three variables as significant independent predictors of mortality: patient comorbidity (relative risk, 16.116; P <0.0001), cumulative deep hypnotic time (Bispectral Index <45) (relative risk=1.244/h; P=0.0121) and intraoperative systolic hypotension (relative risk=1.036/min; P=0.0125). Death during the first year after surgery is primarily associated with the natural history of preexisting conditions. However, cumulative deep hypnotic time and intraoperative hypotension were also significant, independent predictors of increased mortality. These associations suggest that intraoperative anesthetic management may affect outcomes over longer time periods than previously appreciated.

Consciousness monitoring in ventilated patients: bispectral EEG monitors arousal not delirium.

OBJECTIVE: Bispectral index (BIS) is being evaluated as a monitor of consciousness, yet it is unclear what components of consciousness (i.e., arousal vs. content of consciousness) the BIS measures. This study compared BIS levels to well-validated clinical measures of arousal and the presence or absence of delirium. DESIGN: A prospective, blinded, observational cohort study. PATIENTS: 124 mechanically ventilated, adult, medical ICU patients. MEASUREMENTS AND RESULTS: Using BIS 3.4 and BIS-XP 4.0 algorithms, BIS values were calculated immediately prior to clinical assessments. The clinical assessments included the Richmond Agitation-Sedation Scale (RASS) and presence or absence of delirium using the Confusion Assessment Method for the ICU. A total of 484 assessments were collected among 124 patients. BIS-XP values demonstrated greater correlation with RASS than BIS 3.4 ( R(2)=0.36 vs. 0.20), although considerable overlap of BIS-XP scores remained across RASS levels. Median BIS-XP values for delirious and nondelirious observations were 74 and 96, respectively, while BIS 3.4 values were 91 and 96, respectively. However, neither BIS 3.4 nor BIS-XP were significantly associated with delirium after controlling for RASS value. CONCLUSIONS: In comparison with clinical measures of arousal in mechanically ventilated patients, BIS-XP algorithm demonstrated stronger correlation with RASS levels than did BIS 3.4, yet marked overlap across different levels of arousal persist using both algorithms. After controlling for level of arousal, neither BIS-XP nor BIS 3.4 algorithms distinguished between the presence and absence of delirium.