Jeffrey C. Sigl

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 ≥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.

The effect of the interaction of propofol and alfentanil on recall, loss of consciousness, and the bispectral index

The Bispectral Index (BIS) correlates well with the level of consciousness with single anesthetic drugs.We studied the effect of the interaction of propofol with alfentanil on propofol concentration and BIS associated with 50% probability of loss of consciousness and lack of recall (Cp50 and BIS50,

Recovery of consciousness after thiopental or propofol : Bispectral index and the isolated forearm technique

Background Currently, there exists no effective monitor that can predict the probability of a patient being conscious during general anesthesia. The electroencephalogram‐derived bispectral index (BIS) is a promising new method to assess anesthetic adequacy. This study used the BIS to predict the probability of recovery of consciousness after a single bolus induction dose of propofol or thiopental. Methods Twenty unpremedicated surgical patients were anesthetized with 4 mg/kg thiopental and 20 patients with 2 mg/kg propofol. The BIS was monitored throughout the study. After induction, before administration of neuromuscular blocking agent, a tourniquet was applied to one arm and inflated above the systolic blood pressure. This allowed preservation of the ability to move the hand after neuromuscular blocking agent onset. Patients were then prompted to squeeze the investigators hand every 30 s, until they responded to the request. At the time of response, anesthesia was reinduced and the study terminated. Results The BIS at loss of consciousness and recovery of a response was not statistically different between propofol and thiopental. No patient with a BIS less than 58 was conscious. In both groups, a BIS of less than 65 signified a less than 5% probability of return of consciousness within 50 s. Conclusion The BIS can be used to predict probability of recovery of consciousness after a single injection of either thiopental or propofol.

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.

The Effect of Bispectral Index Monitoring on Anesthetic Use and Recovery in Children Anesthetized with Sevoflurane in Nitrous Oxide

The utility of bispectral index (BIS) monitoring to guide anesthetic administration has been demonstrated in adults. This prospective, randomized observer-blinded study was designed to evaluate the effect of BIS monitoring on anesthetic use and recovery characteristics in pediatric patients. After data collection in 38 historical controls, 202 patients age 0–18 yr were randomized into one of two groups: standard practice (SP) and BIS guided (BIS). Patients age 0–3 yr undergoing inguinal hernia repair (IH) and patients age 3–18 yr undergoing tonsillectomy and/or adenoidectomy (TA) were selected. All patients were anesthetized with sevoflurane in 60% N2O/O2. Hernia patients also received a caudal epidural anesthetic before surgery. In the BIS group, anesthetic delivery was adjusted in an effort to achieve a target BIS of 45–60 during maintenance and 60–70 during the last 15 min of the procedure. BIS was recorded throughout surgery in all patients, but data were unavailable to the anesthesiologist in the SP group. In the TA patients, BIS monitoring was associated with a significant reduction in end-tidal sevoflurane concentration during maintenance (2.4 ± 0.6%, SP and 1.8 ± 0.4% BIS, mean ± sd) and during the last 15 min of the procedure (2.1 ± 0.7, SP and 1.6 ± 0.6, BIS). There was a 25%–40% decrease in measured recovery times. In the patients 0–6 mo of age undergoing IH, sevoflurane concentrations during maintenance (2.0 ± 0.4% SP, 0.9 ± 0.8 BIS), during the last 15 min (1.6 ± 0.4% SP, 0.6 ± 0.6% BIS), and at the end of the procedure (1.1 ± 0.6% SP, 0.3 ± 0.3% BIS) were smaller in the BIS group. Emergence and recovery measures were unaffected by BIS titration. In the children 6 mo-3 yr of age, there were no significant differences between the SP and BIS groups in anesthetic use or recovery measures.

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.

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.