CO₂ Adsorption Investigation on an Innovative Nanocomposite Material with Hierarchical Porosity

A NaX nanozeolite-geopolymer monolith, with hierarchical porosity, has been produced by a one-pot hydrothermal synthesis using metakaolin as alluminosilicate source and a sodium silicate solution as activator. Its final composition, reported in terms of oxides, is 1.3-Na₂O-3.0SiO₂-1Al₂O₃-12H₂O. Its microstructural and chemical features and CO₂ adsorption performance have been investigated. The microstructure of the composite is characterized by NaX zeolite nanocrystals glued by the geopolymeric binder to form a complex three-dimensional network of pores. Overall porosity resulted ~23.5%, whereas compressive strength is 16±0.7 MPa. Monolith showed BET surface area of 350 m²/g, a micropore surface area of 280 m²/g and a mesopore volume, due to the geopolymeric binder, of 0.09 cm³/g. Its CO₂ adsorption capacity has been measured at the temperatures of 7, 25 and 42 °C up to 15 bar using an optimized Sievert-type (volumetric) apparatus. All the adsorption data were evaluated by Toth/Langmuir isotherm model and commercial pure NaX zeolite was used as reference. CO₂ adsorption isotherms show a maximum uptake value around 21 wt% at (~7 °C) that decrease to 18 wt% at high temperature (~42 °C) passing through 19 wt% at room temperature (~25 °C). The homogeneity grade of the surface, as obtained using Toth analysis performed on the adsorption isotherm, is close to t ≅ 0.40, lower than the 0.61 obtained for pure commercial NaX zeolite, as a consequence of the binder formation. Monolith exhibits a notably higher K values and quicker saturation with respect to reference that can be ascribed to the presence of mesoporosity that provides an easier and faster transport of CO₂ in the NaX nanozeolite framework. The produced composite is a potential solid adsorbent candidate in industrial process.

Nanostructured Catalysts for Dry-Reforming of Methane

The manuscript deals on the main progress achieved by global scientific research on the development of nanostructured catalysts for dry-reforming reaction. The importance to have a global vision on this topic is strictly related to the most currently and important challenges in the sustainable energy production. In fact, dry-reforming is one of the few known processes in which greenhouse gases are utilized as reactants (methane and carbon dioxide) to produce syngas. Syngas represents the basis for liquid fuel production by Fischer-Tropsch process. In this broad and current context, the catalyst development plays a pivotal role due to its great influence on efficiency, and therefore on the costs, of the whole process. Several are the aspects to consider during the catalyst design: role of metal, interaction between metal and support, role of promoters and resistance to the coke deactivation. These issues, as well as the thermodynamics of the process, are the main aspects of which this review speaks about.

Lymphocyte Functions in the Rat Spleen at Various Times after Urethan Administration

The effect of urethan on various spleen-lymphocyte functions was studied in the rat for 45 days after administration of the carcinogen. For 3 days following the last injection of urethan, the total cell number and LPS reactivity were greatly reduced. Certain reactivities, probably T-cell dependent functions, such as responsiveness to the in vitro mitogenic effect of PHA, Con A, and primary stimulation by histocompatibility alloantigens in the one-way reaction, were selectively enriched during the first 2 days. Thereafter several dissociations of these lymphocyte functions can be observed: i.e., various intervals succeed during which one function may be enriched and other(s) diminished. It seems that the kinetics of enrichment, decay and recovery of the T-cell subsets involved in the reactions investigated follow a distinctive profile for each one of them. It is suggested, as a working hypothesis, that the unbalanced situations derived from the time-course discordance of the quantitative changes in the various lymphocyte functions may allow, or even enhance, tumor development.

Patient and physician perceptions of treatment of moderate-to-severe chronic pain with oral opioids

OBJECTIVE

To study physician and patient perceptions of moderate-to-severe chronic pain and its management with oral opioids.

METHODS

Two separate surveys were developed and administered to one of two respective study groups: patients and physicians. All study participants recruited from a pool of individuals who had previously agreed to participate in market research. Survey questions addressed the impact of various factors (e.g., quality of life indicators, potential for opioid addiction, side-effects) on pain management decision making, patient satisfaction and compliance. Responses for the first 500 patients and 275 physicians to respond were assessed using descriptive statistics.

RESULTS

On average, patients were 53 years of age, white (89%), and female (71%). The majority of patients (80%) had been taking oral opioids longer than 6 months. Physicians reported that 45% of their patients received schedule II opioids, with 27% having severe chronic pain. Patients indicated the most common activities interfered with by chronic pain were exercising (76% of patients), working outside the home (67%), and job responsibilities (60%). When developing a treatment approach physicians considered patients' sleeping (91%), walking (86%), maintaining an independent lifestyle (84%), and job responsibilities (83%). Patients and physicians both rated the ability to relieve pain and the duration of relief as the most important factors when considering opioid therapy. The majority (63%) of patients reported experiencing opioid side effects. When physicians discontinued opioids due to side effects, the most frequent reason was nausea (78%) for immediate-release opioids, and constipation (64%) for extended-release formulations.

CONCLUSION

The ability to relieve pain and the duration of that pain relief are the most important factors for both patients and physicians when selecting an opioid. A high percentage of patients surveyed experienced side effects related to their treatment, which may impact adherence and overall treatment effectiveness. Study results should be assessed within study limitations including responder and selection biases, physicians responded about their patients, who were not the same patients surveyed, and the fact that the survey instruments were not formally validated. Further research is warranted to address these limitations.

Vaginal twin delivery: a survey and review of location, anesthesia coverage and interventions

BACKGROUND

Twin pregnancies are associated with increased perinatal morbidity and mortality. No consensus exists whether vaginal twin delivery should take place in the labor room or operating room, or whether anesthesiologists should be present. We surveyed members of the California Society of Anesthesiologists (CSA) to review management of vaginal twin delivery, and examined anesthetic intervention retrospectively at our institution.

METHODS

230 CSA members were asked to complete an online survey on location of vaginal twin delivery in their institution and whether they were required to be present throughout. We then retrospectively reviewed charts of vaginal twin deliveries at our institution over a 36-month period to analyze frequency and type of anesthetic intervention.

RESULTS

The online survey response rate was 58%; 64% of responders reported that vaginal twin deliveries were performed in the operating room and 55% that an anesthesiologist was present. There was a strong association between anesthesiologist's presence and delivery in the operating room (OR 7; 95% CI 3-20). We reviewed 81 charts of women who underwent vaginal twin delivery. The median (range) time that the anesthesiologist was present for each delivery was 60 (20-380) min. Of women undergoing vaginal twin delivery, 27% required anesthetic intervention during the second stage of labor with 6% having emergency cesarean delivery.

CONCLUSION

There is a lack of consensus regarding the appropriate location for vaginal twin delivery and the role of anesthesiologists. A significant percentage of women undergoing vaginal twin delivery in our institution received anesthetic intervention in the immediate delivery period.

Ketorolac in the Era of Cyclo-Oxygenase-2 Selective Nonsteroidal Anti-Inflammatory Drugs: A Systematic Review of Efficacy, Side Effects, and Regulatory Issues

OBJECTIVE

The recent introduction of oral COX-2 selective NSAIDs with potential for perioperative use, and the ongoing development of intravenous formulations, stimulated a systemic review of efficacy, side effects, and regulatory issues related to ketorolac for management of postoperative analgesia.

DESIGN

To examine the opioid dose sparing effect of ketorolac, we compiled published, randomized controlled trials of ketorolac versus placebo, with opioids given for breakthrough pain, published in English-language journals from 1986-2001. Odds ratios were computed to assess whether the use of ketorolac reduced the incidence of opioid side effects or improved the quality of analgesia.

RESULTS

Depending on the type of surgery, ketorolac reduced opioid dose by a mean of 36% (range 0% to 73%). Seventy percent of patients in control groups experienced moderate-severe pain 1 hour postoperatively, while 36% of the control patients had moderate to severe pain 24 hours postoperatively. Analgesia was improved in patients receiving ketorolac in combination with opioids. However, we did not find a concomitant reduction in opioid side effects (e.g., nausea, vomiting). This may be due to studies having inadequate (to small) sample sizes to detect differences in the incidence of opioid related side effects. The risk for adverse events with ketorolac increases with high doses, with prolonged therapy (>5 days), or invulnerable patients (e.g. the elderly). The incidence of serious adverse events has declined since dosage guidelines were revised.

CONCLUSIONS

Ketorolac should be administered at the lowest dose necessary. Analgesics that provide effective analgesia with minimal adverse effects are needed.

Hospital profitability per hour of operating room time can vary among surgeons

The operating margins (i.e., profits) of hospitals are decreasing. An important aspect of a hospital's finances is the profitability of individual surgical cases, which is measured by contribution margin. We sought to determine the extent to which contribution margin per hour of operating room (OR) time can vary among surgeons. We retrospectively analyzed 2848 elective cases performed by 94 surgeons at the Stanford University School of Medicine. For each case, we subtracted variable costs from the total payment to the hospital to compute contribution margin. We found moderate variability in contribution margin per hour of OR time among surgeons, relative to the variability in contribution margins per OR hour among each surgeon's cases (Cohen's f equaled 0.29, 95% lower confidence interval bound 0.27). Contribution margin per OR hour was negative for 26% of the cases. These results have implications for hospitals for which OR utilization is extensive, and for which elective cases are only scheduled if they can be completed during regularly scheduled hours. To increase or achieve profitability, managers need to increase the hours of lucrative cases, rather than encourage surgeons to do more and more cases. Whether the variability in contribution margin among surgeons should be used to more optimally (profitably) allocate OR time depends on the scheduling objectives of the surgical suite.

Variation in practice patterns of anesthesiologists in California for prophylaxis of postoperative nausea and vomiting

STUDY OBJECTIVE

To assess the responses to a survey asking anesthesiologists to report their clinical practice patterns for postoperative nausea and vomiting (PONV) prophylaxis. These practice patterns data may be useful for understanding how to optimize the decision to provide PONV prophylaxis.

DESIGN

A written questionnaire with three detailed clinical scenarios with differing levels of a priori risk of PONV (a low-risk patient, a medium-risk patient, and a high-risk patient) was mailed to 454 anesthesiologists.

SETTING

Survey was completed by anesthesiologists (n = 240) in 3 university and 3 community practices in California.

MEASUREMENTS

Type and number of pharmacological and nonpharmacological interventions for PONV prophylaxis were recorded. To assess the variability in the responses (by the a priori risk of patient), we counted the number of different regimens that would be necessary to account for 80% of the responses.

MAIN RESULTS

For the 240 respondents, we found that 1, 9, and 11 different pharmacological prophylaxis regimens were required to account for 80% of the variability in practice patterns for the low-, medium-, and high-risk patients, respectively. For the low-risk patient, 19% of practitioners would use pharmacological prophylaxis, and 37% would use nonpharmacological prophylaxis. For the medium-risk patient, 61% would use nonpharmacological prophylaxis and 67% of practitioners would use multidrug prophylaxis: 45% of patients would receive a 5HT(3) antagonist, 35% would receive metoclopramide, and 16% would receive droperidol. For the high-risk patient, 94% of practitioners would administer a 5HT(3) antagonist, whereas 84% would use multi-drug prophylaxis.

CONCLUSIONS

We found a wide range of PONV prophylaxis management patterns. This variation in clinical practice may reflect uncertainty about the efficacy of available interventions, or differences in practitioners' clinical judgment and beliefs about how to treat PONV. Some therapies with proven benefit for PONV may be underused. Our results may be useful for designing studies aimed at determining the impact on PONV rates when physicians develop and implement guidelines for PONV prophylaxis.

Cost-effectiveness of a trial of labor after previous cesarean

OBJECTIVE

To determine the cost-effective method of delivery, from society's perspective, in patients who have had a previous cesarean.

METHODS

We completed an incremental cost-effectiveness analysis of a trial of labor relative to cesarean using a computerized model for a hypothetical 30-year old parturient. The model incorporated data from peer-reviewed studies, actual hospital costs, and utilities to quantify health-related quality of life. A threshold of $50,000 per quality-adjusted life-years was used to define cost-effective.

RESULTS

The model was most sensitive to the probability of successful vaginal delivery. If the probability of successful vaginal birth after cesarean (VBAC) was less than 0.65, elective repeat cesarean was both less costly and more effective than a trial of labor. Between 0.65 and 0.74, elective repeat cesarean was cost-effective (the cost-effectiveness ratio was less than $50,000 per quality-adjusted life-years), because, although it cost more than VBAC, it was offset by improved outcomes. Between 0.74 and 0.76, trial of labor was cost-effective. If the probability of successful vaginal delivery exceeded 0.76, trial of labor became less costly and more effective. Costs associated with a moderately morbid neonatal outcome, as well as the probabilities of infant morbidity occurring, heavily impacted our results.

CONCLUSION

The cost-effectiveness of VBAC depends on the likelihood of successful trial of labor. Our modeling suggests that a trial of labor is cost-effective if the probability of successful vaginal delivery is greater than 0.74. Improved algorithms are needed to more precisely estimate the likelihood that a patient with a previous cesarean will have a successful vaginal delivery.

The impact on revenue of increasing patient volume at surgical suites with relatively high operating room utilization

We previously studied hospitals in the United States of America that are losing money despite limiting the hours that operating room (OR) staff are available to care for patients undergoing elective surgery. These hospitals routinely keep utilization relatively high to maximize revenue. We tested, using discrete-event computer simulation, whether increasing patient volume while being reimbursed less for each additional patient can reliably achieve an increase in revenue when initial adjusted OR utilization is 90%. We found that increasing the volume of referred patients by the amount expected to fill the surgical suite (100%/90%) would increase utilization by <1% for a hospital surgical suite (with longer duration cases) and 4% for an ambulatory surgery suite (with short cases). The increase in patient volume would result in longer patient waiting times for surgery and more patients leaving the surgical queue. With a 15% reduction in payment for the new patients, the increase in volume may not increase revenue and can even decrease the contribution margin for the hospital surgical suite. The implication is that for hospitals with a relatively high OR utilization, signing discounted contracts to increase patient volume by the amount expected to "fill" the OR can have the net effect of decreasing the contribution margin (i.e., profitability).

IMPLICATIONS

Hospitals may try to attract new surgical volume by offering discounted rates. For hospitals with a relatively high operating room utilization (e.g., 90%), computer simulations predict that increasing patient volume by the amount expected to "fill" the operating room can have the net effect of decreasing contribution margin (i.e., profitability).

Optimal number of beds and occupancy to minimize staffing costs in an obstetrical unit?

PURPOSE

We describe how the science of analyzing patient arrival and discharge data can be used to determine the optimal number of staffed OB beds to minimize labour costs.

METHODS

The number of staffed beds represents a balance between having as few staffed beds as possible to care properly for parturients vs having enough capacity to assure available staff for new admissions. The times of admission and discharge of patients from the OB unit can be used to calculate an average census. From this average census, and the properties of the Poisson distribution, the optimal number of staffed beds can be estimated. This calculation requires specification of the risk of having all in-house and on-call staff caring for patients, such that additional staff are unavailable should another parturient arrive. As an example, patient admission and discharge times were obtained for 777 successive patients cared for at an obstetrical unit. The numbers of patients present in the OB unit each two-hour period were calculated and analyzed statistically.

PRINCIPAL FINDINGS

There was variation in the average census among hours of the day and days of the week. Poisson distributions fit the data for each of four periods throughout the week. Simply benchmarking the current average occupancy and comparing it to a desired occupancy would have been inadequate as this neglected consideration of the risk of being unable to appropriately care for an additional patient.

CONCLUSIONS

The optimal number of beds and occupancy of an OB unit to minimize staffing costs can be determined using straightforward statistical methods.

What is the relative frequency of uncommon ambulatory surgery procedures performed in the United States with an anesthesia provider?

Between 1994 and 1996, the National Center for Health Statistics used sophisticated sampling methods to measure the number and types of ambulatory surgery cases performed in the United States. We reanalyzed raw data obtained from this National Survey of Ambulatory Surgery to select cases with an anesthesia provider and here report characteristics of these 228,332 cases (e.g., patient age, anesthetic type). The goal of our study was to estimate what percentage of cases, of a specified surgical procedure or combination of procedures, may have been performed less than once per year per facility. Previous studies suggest the most important source of scheduling inaccuracy can be the absence of recently performed cases on which to base predictions of case duration. We found that 36% +/- 1% (SE) of all cases in the United States were a type of procedure or combination of procedures that occurred <6984 times per year (the number of surgery facilities performing ambulatory surgery in the United States). Approximately one third of all ambulatory cases were of a procedure or combination of procedures that may have been performed as infrequently as once per year per facility. This could impair the effectiveness of predicting the durations of ambulatory cases by using historical case-duration data.

IMPLICATIONS

Approximately one third of all ambulatory cases were a procedure or combination of procedures possibly performed as infrequently as once per year per facility. This could impair the effectiveness of predicting the durations of ambulatory cases by using historical case-duration data.

Quantitative description of the workload associated with airway management procedures

STUDY OBJECTIVES

To measure the workload associated with specific airway management tasks.

SETTING AND INTERVENTION

Written survey instrument.

PATIENTS

166 Stanford University and 75 University of California, San Diego, anesthesia providers.

MEASUREMENTS AND MAIN RESULTS

Subjects were asked to use a seven-point Likert-type scale to rate the level of perceived workload associated with different airway management tasks with respect to the physical effort, mental effort, and psychological stress they require to perform in the typical clinical setting. The 126 subjects completing questionnaires (overall 52% response rate) consisted of 43% faculty, 26% residents, 23% community practitioners, and 8% certified registered nurse-anesthetists (CRNAs). Faculty physicians generally scored lower workload measures than residents, whereas community practitioners had the highest workload scores. Overall, workload ratings were lowest for laryngeal mask airway (LMA) insertion and highest for awake fiberoptic intubation. Airway procedures performed on sleeping patients received lower workload ratings than comparable procedures performed on awake patients. Direct visualization procedures received lower workload ratings than fiberoptically guided procedures.

CONCLUSIONS

These kinds of data may permit more objective consideration of the nonmonetary costs of technical anesthesia procedures. The potential clinical benefits of the use of more complex airway management techniques may be partially offset by the impact of increased workload on other clinical demands.

A retrospective examination of regional plus general anesthesia in children undergoing open heart surgery

The use of regional anesthesia in combination with general anesthesia for children undergoing cardiac surgery is receiving increasing attention from clinicians. The addition of regional anesthesia may improve clinical outcomes and decrease costs as a result of the reduced need for postoperative mechanical ventilation. The goal of this retrospective chart review was to evaluate whether spinal anesthesia (SAB) or epidural anesthesia (EPID) in combination with general anesthesia was associated with circulatory stability, satisfactory postoperative sedation/analgesia, and a low incidence of adverse effects. The medical records of 50 consecutive children having open heart surgery with SAB or EPID and general anesthesia between September 1996 and December 1997 were reviewed. We found no significant differences in the incidence of clinically significant changes in vital signs, oxygen desaturation, hypercarbia, or vomiting. Patients in the SAB group received significantly more sedative/analgesic interventions than those in the EPID group.

Effect of compensation and patient scheduling on OR labor costs

To determine whether to accept a contract to provide additional surgical cases, OR managers must determine the incremental costs of caring for the new patients. The expected profitability of the contract can be computed by subtracting the incremental costs from the revenue. For surgical procedures, the incremental costs of OR labor significantly depend on how employees are paid (e.g., part-time versus full-time). If a surgical suite employs full-time staff members, incremental labor costs also are affected by how the day and time of patients' cases are selected (e.g., whether new cases are scheduled weeks in advance by the surgeon and the patient, or are performed on short notice based on the discretion of the surgical suite). This article explains how to estimate the incremental costs of staffing an OR for a case and discusses the use of internet-based online exchanges to match demand for OR time for additional cases to available unused OR capacity in variety of surgical suites.

Scheduling surgical cases into overflow block time- computer simulation of the effects of scheduling strategies on operating room labor costs

"Overflow" block time is operating room (OR) time for a surgical group's cases that cannot be completed in the regular block time allocated to each surgeon in the surgical group. Having such overflow block time increases OR utilization. The optimal way to schedule patients into a surgical group's overflow block time is unknown. In this study, we developed a scheduling strategy that balances the OR manager's need to reduce staffing costs and the needs of patients and surgeons for flexibility in choosing the dates and times of cases. We used computer simulation to evaluate our scheduling strategy. Surgeons and patients (i) can schedule the case into any overflow block within 2 wk; (ii) can only schedule the case into a "first case of the day" start time more than 2 wk in the future if there is not enough open time for the case within 2 wk; (iii) must schedule the case to be done within 4 wk; and (iv) are encouraged to perform the case on the earliest possible date. Staffing costs were lowest when the OR manager did not incorporate surgeon and patient preferences when scheduling cases into overflow block time. The strategy we developed provides surgeons and patients with some flexibility in scheduling, while only increasing OR staffing costs slightly over the minimum achieved when the OR manager controls scheduling.

IMPLICATIONS

The strategy we developed provides surgeons and patients with some flexibility in scheduling, while increasing OR staffing costs only slightly over the minimum achieved when the OR manager controls scheduling. Staffing costs were lowest when the operating room (OR) manager did not incorporate surgeon and patient preferences when scheduling cases into overflow block time.

Analgesia for labor pain: a cost model

BACKGROUND

Epidural analgesia and intravenous analgesia with opioids are two techniques for the relief of labor pain. The goal of this study was to develop a cost-identification model to quantify the costs (from society's perspective) of epidural analgesia compared with intravenous analgesia for labor pain. Because there is no valid method to assign a dollar value to differing levels of analgesia, the cost of each technique can be compared with the analgesic benefit (patient pain scores) of each technique.

METHODS

The authors created a cost model for epidural and intravenous analgesia by reviewing the literature to determine the rates of associated clinical outcomes (benefit of each technique to produce analgesia) and complications (e.g., postdural puncture headache). The authors then analyzed data from their institution's cost-accounting system to determine the hospital cost for parturients admitted for delivery, estimated the cost of each complication, and performed a sensitivity analysis to evaluate the cost impact of changing key variables. A secondary analysis was performed assuming that the cost of nursing was fixed (did not change depending on the number of nursing interventions).

RESULTS

If the cesarean section rate equals 20% for both intravenous and epidural analgesia, the additional expected cost per patient to society of epidural analgesia of labor pain ranges from $259 (assuming nursing costs in the labor and delivery suite do not vary with the number of nursing interventions) to $338 (assuming nursing costs do increase as the number of interventions increases) relative to the expected cost of intravenous analgesia for labor pain. This cost difference results from increased professional costs and complication costs associated with epidural analgesia.

CONCLUSIONS

Epidural analgesia is more costly than intravenous analgesia. How the cost of the anesthesiologist and nursing care is calculated affects how much more costly epidural analgesia is relative to intravenous analgesia. Published studies have determined that epidural analgesia provides relief of labor pain superior to intravenous analgesia, quantified in one study as 40 mm better on a 100-mm scale during the first stage of labor and 29 mm better during the second stage of labor. Patients, physicians, and society need to weigh the value of improved pain relief from epidural analgesia versus the increased cost of epidural analgesia.

Statistical method using operating room information system data to determine anesthetist weekend call requirements

We present a statistical method that uses data from surgical services information systems to determine the minimum number of anesthetists to be scheduled for weekend call in an operating room suite. The staffing coverage is predicted that provides for sufficient anesthetists to cover each hour of a 24-hour weekend period, while satisfying a specified risk for being understaffed. The statistical method incorporates shifts of varying start times and durations, as well as historical weekend operating room caseload data. By using this method to schedule weekend staff, an anesthesia group can assure as few anesthetists are on call as possible, and for as few hours as possible, while maintaining the level of risk of understaffing that the anesthesia group is willing to accept. An anesthesia group also can use the method to calculate its risk of being understaffed in the surgical suite based on its existing weekend staffing plan.

Which algorithm for scheduling add-on elective cases maximizes operating room utilization? Use of bin packing algorithms and fuzzy constraints in operating room management

BACKGROUND

The algorithm to schedule add-on elective cases that maximizes operating room (OR) suite utilization is unknown. The goal of this study was to use computer simulation to evaluate 10 scheduling algorithms described in the management sciences literature to determine their relative performance at scheduling as many hours of add-on elective cases as possible into open OR time.

METHODS

From a surgical services information system for two separate surgical suites, the authors collected these data: (1) hours of open OR time available for add-on cases in each OR each day and (2) duration of each add-on case. These empirical data were used in computer simulations of case scheduling to compare algorithms appropriate for "variable-sized bin packing with bounded space." "Variable size" refers to differing amounts of open time in each "bin," or OR. The end point of the simulations was OR utilization (time an OR was used divided by the time the OR was available).

RESULTS

Each day there were 0.24 +/- 0.11 and 0.28 +/- 0.23 simulated cases (mean +/- SD) scheduled to each OR in each of the two surgical suites. The algorithm that maximized OR utilization, Best Fit Descending with fuzzy constraints, achieved OR utilizations 4% larger than the algorithm with poorest performance.

CONCLUSIONS

We identified the algorithm for scheduling add-on elective cases that maximizes OR utilization for surgical suites that usually have zero or one add-on elective case in each OR. The ease of implementation of the algorithm, either manually or in an OR information system, needs to be studied.

Forecasting surgical groups' total hours of elective cases for allocation of block time: application of time series analysis to operating room management

BACKGROUND

Allocation of the correct amount of operating room (OR) "block time" can provide surgeons with access to sufficient OR time to complete their elective cases while optimally matching staffing with the elective case workload (to maximize labor productivity). To evaluate how to predict accurately total hours of elective cases performed by a surgical group using data from surgical services information systems, the authors addressed the following questions: (1) How many previous 4-week periods of data should be used to minimize error in forecasting a surgical group's total hours of elective cases? (2) Using the number of 4-week periods from question #1, can we detect trends or correlations between successive periods that could be used to improve forecasting accuracy? (3) How can results from questions #1 and #2 be used to calculate an upper prediction bound (upper limit) for the total hours of elective cases that will be completed in a future period? Prediction bounds can be used to budget staffing accurately.

METHODS

Time series analysis was performed on total hours of elective cases over 39 consecutive 4-week periods from 17 surgical groups.

RESULTS

The average of 12 consecutive periods' total hours of elective cases had an appropriate error profile. The observations within each series of 12 consecutive 4-week periods followed a normal distribution, with each observation of total hours of elective cases not correlated with the subsequent observation.

CONCLUSIONS

The average of the most recent 12 4-week periods can be used to predict surgical groups' future use of block time.

Estimating the duration of a case when the surgeon has not recently scheduled the procedure at the surgical suite

For some scheduled cases, there may be no previous cases of the same procedure type by the same surgeon for use in estimating the duration of the new case. We evaluated which of 16 different methods of analysis of other surgeons' cases of the same procedure type resulted in the most accurate prediction of the duration of the case that the surgeon had not recently scheduled. We analyzed durations for 4,955 cases, from an operating room information system, for which a surgeon had only scheduled the procedure once, and for which other surgeons had scheduled that same procedure one or more times. Using these data, we determined the difference between the actual duration of the new case and the estimated duration of the new case as calculated by each of the methods (average absolute error of 1.1 h with average case duration of 3.1 h).

IMPLICATIONS

When no recent historical time data are available for a surgeon doing a given procedure, the mean of the durations of cases of the same scheduled procedure performed by other surgeons is as accurate an estimate as more sophisticated analyses. More research is needed to improve the precision of estimates of case durations.

Relying solely on historical surgical times to estimate accurately future surgical times is unlikely to reduce the average length of time cases finish late

STUDY OBJECTIVE

To determine whether using only previous cases' surgical times for predicting accurately surgical times of future cases is likely to reduce the average length of time cases finish late (after their scheduled finish times).

DESIGN

Computer simulation.

MEASUREMENTS AND MAIN RESULTS

Data from an operating room (OR) information system for two surgical suites were analyzed. For each case performed in fiscal year 1996, we searched backward for 1 year and counted the number of previous cases that were the same type of procedure performed by the same surgeon. Then, for each suite, surgical times were fitted to a statistical model estimating the effect of the type of procedure and who the surgeon was on surgical time. The estimated "variance components" were used in Monte-Carlo computer simulations to evaluate whether a hypothetical increase in the number of previous cases available to estimate the next case's surgical time would improve scheduling accuracy. Predictions of how long newly scheduled cases should take were impaired because 36.5% +/- 0.4% (mean +/- SE) of cases at a tertiary surgical suite and 28.6% +/- 0.7% of cases at an ambulatory surgery center did not have any cases in the previous year with the same procedure type and surgeon. Computer simulation was used to generate additional hypothetical cases. Using this data, even having many previous cases on which to base predictions of future surgical times would only decrease the average length of time that cases finish late by a few minutes.

CONCLUSION

An OR manager considering using only historical surgical times to estimate future surgical times should first investigate, using data from their own surgical suite, what percentage of cases do not have historical data. Even if there are sufficient historical data to estimate future surgical times accurately, relying solely on historical times is probably an ineffective strategy to have future cases finish on time.

A strategy for deciding operating room assignments for second-shift anesthetists

We developed a relief strategy for assigning second-shift anesthetists to late-running operating rooms. The strategy relies on a statistical method which analyzes historical case durations available from surgical services information systems to estimate the expected (mean) remaining hours in cases after they have begun. We tested our relief strategy by comparing the number of hours that first-shift anesthetists would work overtime if second-shift anesthetists were assigned using our strategy versus if the anesthesia coordinator knew in advance the exact amount of time remaining in each case. Our relief strategy resulted in 3.4% to 4.9% more overtime hours for first-shift anesthetists than the theoretical minimum, as would have been obtained had perfect retrospective knowledge been available. Few additional staff hours would have been saved by supplementing our relief strategy with other methods to monitor case durations (e.g., real-time patient tracking systems or closed circuit cameras in operating rooms).

IMPLICATIONS

A relief strategy that relies only on analyzing historical case durations from an operating room information system to predict the time remaining in cases performs well at minimizing anesthetist staffing costs.

What can the postanesthesia care unit manager do to decrease costs in the postanesthesia care unit?

The economic structure of the PACU dictates whether a cost-reducing intervention (e.g., reducing the length of time patients stay in the PACU) is likely to decrease hospital costs. Cost-reducing interventions, such as changes in medical practice patterns (e.g., to reduce PACU length of stay), only impact variable costs. How PACU nurses are paid (e.g., salaried v hourly) affects which strategies to decrease PACU staffing costs will actually save money. For example, decreases in PACU labor costs resulting from increases in the number of patients that bypass the PACU vary depending on how the staff is compensated. The choice of anesthetic drugs and the elimination of low morbidity side effects of anesthesia, such as postoperative nausea, are likely to have little effect on the peak numbers of patients in a PACU and PACU staffing costs. Because the major determinant of labor productivity in the PACU is hour-to-hour and day-to-day variability in the timing of admissions from the operating room, a more even inflow of patients into the PACU could be attained by appropriate sequencing of cases in the operating room suite (e.g., have long cases scheduled at the beginning of the day). However, this mathematically proven solution may not be desirable. Surgeons, for example, may not want to lose control over the order of their cases. Guidelines for analysis of past daily peak numbers of patients are provided that will provide data to predict the minimum adequate number of nurses needed. Though many managers already do this manually on an ad hoc basis statistical methods summarized in this article may increase the accuracy.

Which clinical anesthesia outcomes are important to avoid? The perspective of patients

Healthcare quality can be improved by eliciting patient preferences and customizing care to meet the needs of the patient. The goal of this study was to quantify patients' preferences for postoperative anesthesia outcomes. One hundred one patients in the preoperative clinic completed a written survey. Patients were asked to rank (order) 10 possible postoperative outcomes from their most undesirable to their least undesirable outcome. Each outcome was described in simple language. Patients were also asked to distribute $100 among the 10 outcomes, proportionally more money being allocated to the more undesirable outcomes. The dollar allocations were used to determine the relative value of each outcome. Rankings and relative value scores correlated closely (r2 = 0.69). Patients rated from most undesirable to least undesirable (in order): vomiting, gagging on the tracheal tube, incisional pain, nausea, recall without pain, residual weakness, shivering, sore throat, and somnolence (F-test < 0.01).

IMPLICATIONS

Although there is variability in how patients rated postoperative outcomes, avoiding nausea/vomiting, incisional pain, and gagging on the endotracheal tube was a high priority for most patients. Whether clinicians can improve the quality of anesthesia by designing anesthesia regimens that most closely meet each individual patient's preferences for clinical outcomes deserves further study.

An operating room scheduling strategy to maximize the use of operating room block time: computer simulation of patient scheduling and survey of patients' preferences for surgical waiting time

Determining the appropriate amount of block time to allocate to surgeons and selecting the days on which to schedule elective cases can maximize operating room (OR) use. We used computer simulation to model OR scheduling. Inputs in the computer model included different methods to determine when a patient will have surgery (on-line bin-packing algorithms), case durations, lengths of time patients wait for surgery (2 wk is the median longest length of time that the outpatients [n = 367] surveyed considered acceptable), hours of block time each day, and number of blocks each week. For block time to be allocated to maximize OR utilization, two parameters must be specified: the method used to decide on what day a patient will have surgery and the average length of time patients wait to have surgery. OR utilization depends greatly on, and increases as, the average length of time patients wait for surgery increases.

IMPLICATIONS

Operating room utilization can be maximized by allocating block time for the elective cases based on expected total hours of elective cases, scheduling patients into the first available date provided open block time is available within 4 wk, and otherwise scheduling patients in "overflow" time outside of the block time.

Statistical method to evaluate management strategies to decrease variability in operating room utilization: application of linear statistical modeling and Monte Carlo simulation to operating room management

BACKGROUND

Operating room (OR) managers seeking to maximize labor productivity in their OR suite may attempt to reduce day-today variability in hours of OR time for which there are staff but for which there are no cases ("underutilized time"). The authors developed a method to analyze data from surgical services information systems to evaluate which management interventions can most effectively decrease variability in underutilized time.

METHODS

The method uses seven summary statistics of daily workload in a surgical suite: daily allocated hours of OR time, estimated hours of elective cases, actual hours of elective cases, estimated hours of add-on cases, actual hours of add-on cases, hours of turnover time, and hours of underutilized time. Simultaneous linear statistical equations (a structural equation model) specify the relationship among these variables. Estimated coefficients are used in Monte Carlo simulations.

RESULTS

The authors applied the analysis they developed to two OR suites: a tertiary care hospital's suite and an ambulatory surgery center. At both suites, the most effective strategy to decrease variability in underutilized OR time was to choose optimally the day on which to do each elective case so as to best fill the allocated hours. Eliminating all (1) errors in predicting how long elective or add-on cases would last, (2) variability in turnover or delays between cases, or (3) day-to-day variation in hours of add-on cases would have a small effect.

CONCLUSIONS

This method can be used for decision support to determine how to decrease variability in underutilized OR time.

Computer simulation to determine how rapid anesthetic recovery protocols to decrease the time for emergence or increase the phase I postanesthesia care unit bypass rate affect staffing of an ambulatory surgery center

Ambulatory surgery centers (ASC) are implementing new anesthetic techniques and rapid recovery protocols in the postanesthesia care unit (PACU) to achieve earlier discharge after general anesthesia. Using computer simulation, we addressed two questions. First, what is the decrease in an ASC's operating room (OR) staff if the time from which the surgery is finished to the time the patient leaves the OR is decreased? Second, what is the decrease in PACU nursing staffing if patients bypass phase I PACU (i.e., proceed from the OR directly to the phase II PACU)? The decrease in labor costs from rapid emergence or fast-tracking depends on how staff are compensated, how many ORs routinely run concurrently, and what percentage of patients undergo general anesthesia. The results show potential decreases in ASCs' labor costs ($7.39 per case) from technologies (e.g., new anesthetics or Bispectral Index [Aspect Medical Systems, Natick, MA] monitoring) to decrease emergence times or increase the phase I bypass rates.

IMPLICATIONS

Decreases in operating room and postanesthesia care unit labor costs resulting from faster emergence and phase I postanesthesia care unit bypass vary depending on the amount of routine overtime, how the staff are compensated, and how many patients are routinely anesthetized each day.

Optimal sequencing of urgent surgical cases. Scheduling cases using operating room information systems

Optimal sequencing of urgent cases (i.e., selecting which urgent case should be performed first and which second) may enhance patient safety, increase patient satisfaction with timeliness of surgery, and minimize surgeons' complaints. Before determining the optimal sequence of urgent cases, an operating room (OR) suite must identify the primary scheduling objective to be satisfied when prioritizing pending urgent cases. These scheduling objectives may include: 1) perform the cases in the sequence that minimizes the average length of time each surgeon and patient waits; 2) perform the cases in the order that they were submitted; or 3) perform the cases based on medical priority, as prioritized by an OR director, or surgeons discussing the cases among themselves. We provide mathematical structure which can be used to program a computerized surgical services information system to assist in optimizing the sequence of urgent cases. We use an example to illustrate that the optimal sequence varies depending on the scheduling objective chosen.

Which clinical anesthesia outcomes are both common and important to avoid? The perspective of a panel of expert anesthesiologists

Anesthesia groups may need to determine which clinical anesthesia outcomes to track as part of quality improvement efforts. The goal of this study was to poll a panel of expert anesthesiologists to determine which clinical anesthesia outcomes associated with routine outpatient surgery were judged to occur frequently and to be important to avoid. Outcomes scoring highly in both scales could then be prioritized for measurement and improvement in ambulatory clinical practice. A mailed survey instrument instructed panel members to rate 33 clinical anesthesia outcomes in two scales: how frequently they believe the outcomes occur and which outcomes they expect patients find important to avoid. A feedback process (Delphi process) was used to gain consensus rankings of the outcomes for each scale. Importance and frequency scores were then weighted equally to qualitatively rank order the outcomes. Of the 72 anesthesiologists, 56 (78%) completed the questionnaire. The five items with the highest combined score were (in order): incisional pain, nausea, vomiting, preoperative anxiety, and discomfort from IV insertion. To increase quality of care, reducing the incidence and severity of these outcomes should be prioritized.

IMPLICATIONS

Expert anesthesiologists reached a consensus on which low-morbidity clinical outcomes are common and important to the patient. The outcomes identified may be reasonable choices to be monitored as part of ambulatory anesthesia clinical quality improvement efforts.

Decrease in case duration required to complete an additional case during regularly scheduled hours in an operating room suite: a computer simulation study

We used Monte-Carlo computer simulation to determine whether surgical or anesthetic interventions to achieve small decreases in case duration may create enough new open operating room (OR) time to permit an additional case to be scheduled for completion in an OR suite during regular working hours. We used rules for scheduling of cases assuming that OR personnel are compensated so that the OR suite can profit financially from decreasing case duration to complete an additional case during regularly scheduled hours. The decreases in each case's duration required to create enough new open OR time to reliably (> or =95%) schedule another case were 30-39 min, 79-110 min, and 105-206 min for OR suites with 1-15 ORs and mean case durations of 1, 2, or 3 h, respectively.

IMPLICATIONS

Computer simulation shows decreasing case duration is unlikely to create sufficient operating room time to reliably permit an additional case to be scheduled for completion during working hours. Additional cases may best be added to the operating room suite schedule by optimizing case scheduling, not by decreasing the duration of all cases in the suite.

Obstetric postanesthesia care unit stays: reevaluation of discharge criteria after regional anesthesia

BACKGROUND

Obstetric patients may have long postanesthesia care unit (OB-PACU) stays after surgery because of residual regional block or other conditions. This study evaluated whether modified discharge criteria might allow for earlier discharge without compromising patient safety.

METHODS

Data were prospectively collected for 6 months for all patients (N=358) who underwent cesarean section or tubal ligation and recovered in the OB-PACU. Regional anesthesia was used in 94% of patients. The duration of anesthesia and PACU stays, the presence and treatment of events in the PACU, and the regression of neural blockade were recorded. Discharge from the OB-PACU required a 60-min minimum stay, stable vital signs, adequate analgesia, and ability to flex the knees. After completion of prospective data collection, events that kept patients in the PACU after 60 min were reevaluated as to whether patients needed to stay in the PACU for medical reasons. "Needed to stay" events included bleeding, cardiorespiratory problems, sedation, dizziness, and pain. "Safe to leave" conditions included pruritus, nausea, and residual neural blockade. The cumulative duration of OB-PACU stays not clearly justifiable for medical reasons was calculated.

RESULTS

Residual block and spinal opioid side effects accounted for the majority of "unnecessary" stays. Annually, 429 h of PACU time could have been saved using the revised criteria. Complications did not develop subsequently in any patient deemed "safe to leave."

CONCLUSIONS

In many obstetric patients, the duration of PACU stays could safely be shortened by continuing observation in a lower-acuity setting. This may result in greater flexibility and more efficient use of nursing personnel.

Computer simulation of changes in nursing productivity from early tracheal extubation of coronary artery bypass graft patients

STUDY OBJECTIVE

To determine whether the results from a clinical trial, which showed that early extubation of elective coronary artery bypass graft (CABG) patients can reduce hospital costs by more rapid discharge of patients from the intensive care unit (ICU), are likely to apply to other hospitals.

DESIGN

Discrete-event computer simulation.

MEASUREMENTS AND MAIN RESULTS

We (1) generated simulated CABG patients, (2) had them "flow" from one condition to the next according to specified rules, and (3) calculated the labor productivity of simulated nurses who would be caring for the patients. We defined nursing labor productivity as the number of patients undergoing elective CABG cared for each year per nursing full-time equivalent working 40 hours per week. Our simulations predict that the increase in nursing labor productivity achieved by early extubation of CABG patients is sensitive to the number of elective CABG cases performed each year at the hospital and the method of compensating nurses. Hospitals with an "hourly workforce" and many cases per year are predicted to achieve a greater increase in productivity from early extubation than are hospitals with a "salaried workforce" and less active volume. At hospitals with a salaried workforce, increasing the percentage of patients extubated early may have no effect on labor productivity.

CONCLUSIONS

Although "fast-tracking" protocols may offer benefits other than increasing nursing labor productivity (i.e., saving money), the results of clinical trials that demonstrate cost savings from clinical pathways that include early tracheal extubation are likely to apply only to hospitals that have similar annual CABG volume and method of compensating nurses as those in the clinical trial. To estimate the likely economic impact from early extubation protocols, a hospital should complete a simulation study with parameter values appropriate to its institution.

Hospital profitability for a surgeon's common procedures predicts the surgeon's overall profitability for the hospital

STUDY OBJECTIVE

To evaluate whether a hospital's profitability for a surgeon's common procedures predicts the surgeon's overall profitability for the hospital.

DESIGN

Observational study.

SETTING

Community and university-affiliated tertiary hospital with 21,903 surgical procedures performed per year.

PATIENTS

7,520 patients having surgery performed by one of 46 surgeons.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Financial data were obtained for all patients cared for by all the surgeons who performed at least ten cases of one of the hospital's six most common procedures. A surgeon's overall profitability for the hospital was measured using his or her contribution margin ratio (i.e., total revenue for all of the surgeon's patients divided by total variable cost for the patients). Contribution margin was calculated twice: once with all of a surgeon's patients, and second, limiting consideration to those patients who underwent one of the six common procedures. The common procedures accounted for 22 +/- 15% of the 46 surgeons' overall caseload, 29 +/- 10% of their patients' hospital costs, and 30 +/- 12% of the hospital revenue generated by the surgeons. Hospital contribution margin ratios ranged from 1.4 to 4.2. Contribution margin ratios for common procedures and contribution margin ratios for all patients were correlated (tau = 0.58, n = 46, p < 0.0001).

CONCLUSIONS

Even though most surgical cases were for uncommon procedures, a surgeon's hospital profitability on common procedures predicted the surgeon's overall financial performance. Perioperative incentive programs based on common surgical procedures (clinical pathways) are likely to accurately reflect a surgeon's financial performance on their other surgeries.