Elisabeth U. Dexter

Both Bias and Lack of Knowledge Influence Organizational Focus on First Case of the Day Starts

BACKGROUND: The economic costs of reducing first case delays are often high, because efforts need to be applied to multiple operating rooms (ORs) simultaneously. Nevertheless, delays in starting first cases of the day are a common topic in OR committee meetings. METHODS: We added three scientific questions to a 24 question online, anonymous survey performed before the implementation of a new OR information system. The 57 respondents cared sufficiently about OR management at the United States teaching hospital to complete all questions. RESULTS: The survey revealed reasons why personnel may focus on the small reductions in nonoperative time achievable by reducing tardiness in first cases of the day. (A) Respondents lacked knowledge about principles in reducing over-utilized OR time to increase OR efficiency, based on their answering the relevant question correctly at a rate no different from guessing at random. Those results differed from prior findings of responses at a rate worse than random, resulting from a bias on the day of surgery of making decisions that increase clinical work per unit time. (B) Most respondents falsely believed that a 10 min delay at the start of the day causes subsequent cases to start at least 10 min late (P < 0.0001 versus random chance)

Treatment advances for medically inoperable non-small-cell lung cancer: emphasis on prospective trials

Advances in technology have changed the treatment of patients with early stage non-small-cell lung cancer who are not healthy enough for standard surgical resection. Previously, patients with severe underlying cardiopulmonary dysfunction were often dissuaded from pursuing definitive therapy, even though most patients died from their lung cancer and not as a result of comorbid medical illness. Recent advances in the technology to treat early stage disease have led to new-found enthusiasm for treating and studying high-risk patients. This Review focuses on the management of these patients, including use of conformal radiotherapy, stereotactic body radiation therapy, sublobar resection, intraoperative brachytherapy, and radiofrequency ablation. Ongoing challenges are presented and prospective data are emphasised.

Systematic review of general thoracic surgery articles to identify predictors of operating room case durations.

BACKGROUND: Previous studies of operating room (OR) information systems data over the past two decades have shown how to predict case durations using the combination of scheduled procedure(s), individual surgeon and assistant(s), and type of anesthetic(s). We hypothesized that the accuracy of case duration prediction could be improved by the use of other electronic medical record data (e.g., patient weight or surgeon notes using standardized vocabularies). METHODS: General thoracic surgery was used as a model specialty because much of its workload is elective (scheduled) and many of its cases are long. PubMed was searched for thoracic surgery papers reporting operative time, surgical time, etc. The systematic literature review identified 48 papers reporting statistically significant differences in perioperative times. RESULTS: There were multiple reports of differences in OR times based on the procedure(s), perioperative team including primary surgeon, and type of anesthetic, in that sequence of importance. All such detail may not be known when the case is originally scheduled and thus may require an updated duration the day before surgery. Although the use of these categorical data from OR systems can result in few historical data for estimating each case’s duration, bias and imprecision of case duration estimates are unlikely to be affected. There was a report of a difference in case duration based on additional information. However, the incidence of the procedure for the diagnosis was so uncommon as to be unlikely to affect OR management. CONCLUSIONS: Matching findings of prior studies using OR information system data, multiple case series show that it is important to rely on the precise procedure(s), surgical team, and type of anesthetic when estimating case durations. OR information systems need to incorporate the statistical methods designed for small numbers of prior surgical cases. Future research should focus on the most effective methods to update the prediction of each case’s duration as these data become available. The case series did not reveal additional data which could be cost-effectively integrated with OR information systems data to improve the accuracy of predicted durations for general thoracic surgery cases.

Negative Pressure Transients with Mechanical Heart-Valve Closure: Correlation between In Vitro and In Vivo Results

AbstractNegative pressure transients (NPT) recorded in a single closing event of mechanical valves in the mitral position in an in vitro setup are compared with data recorded in the left atrium in vivo with the valves implanted in the mitral position in an animal model. The loading at valve closure (dP/dt_CL) computed from the in vivo ventricular pressure recording (ranging from 700 to 2300 mm Hg/s) agreed with the magnitudes predicted in our earlier in vitro experiments (750-3000 mm Hg/s). The NPT signals and the corresponding power spectral density plots from the in vivo data were in qualitative agreement with those recorded in vitro. The NPT magnitudes were found to be below the vapor pressure for blood in mechanical valves with rigid occluders suggesting a potential for the valve to cavitate in vivo. Our in vivo results also suggest that the valves with flexible occluders are less likely to cavitate. The correlation of the in vitro and in vivo data also suggests that the flexibility of valve housing used in the in vitro studies is not an important factor in the dynamics of mechanical valve closure in vivo.

Statistical grand rounds: Importance of appropriately modeling procedure and duration in logistic regression studies of perioperative morbidity and mortality.

Multiple logistic regression studies frequently are performed with duration (e.g., operative time) included as an independent variable. We use narrative review of the statistical literature to highlight that when the association between duration and outcome is presumptively significant, the procedure itself (e.g., video-assisted thoracoscopic lobectomy or thoracotomy lobectomy) needs to be tested for inclusion in the logistic regression. If the procedure is a true covariate but excluded in lieu of category of procedure (e.g., lung resection), estimates of the odds ratios for other independent variables are biased. In addition, actual durations are sometimes used as the independent variable, rather than scheduled (forecasted) durations. Only the scheduled duration is known when a patient would be randomized in a trial of preoperative or intraoperative intervention and/or meets with the surgeon and anesthesiologist preoperatively. By reviewing the literature about logistic regression and about predicting case duration, we show that the use of actual instead of scheduled duration can result in biased logistic regression results.

In vivo demonstration of cavitation potential of a mechanical heart valve

Cavitation is implicated as the cause of pitting and erosion of explanted mechanical heart valves that failed. Previous in vitro studies demonstrated transient negative pressure spikes upstream of mechanical heart valves at the instant of leaflet closure. When the magnitude of the transient negative pressure spike is below the vapor pressure of the fluid flowing across the mechanical valve, cavitation bubbles have been documented near the valve housing or occluder disc. To test for the presence of transient negative pressure spikes that are conducive to cavitation in vivo, we measured left atrial pressure at the valve orifice after mitral valve replacement. Mitral valves were replaced with 27 mm prostheses in 10 goats (50-60 kg). Control animals (Group 1, n = 5) received pericardial valves. Study animals (Group 2, n = 5) received bileaflet pyrolytic carbon valves. Pressure was recorded from a high frequency atrial transducer at hyperdynamic and hypodynamic states. Transient negative pressure spikes did not occur in any Group 1 animal. Transient negative pressure spikes below the vapor pressure of blood (-713 mm Hg) were recorded in four of five Group 2 animals at the hyperdynamic state: -900, -950, -800, -400, and -1,400 mm Hg (p = 0.048 Group 1 versus Group 2, Fishers exact test). No cavitation potential exists in vivo after bioprosthetic valve implantation. Transient negative pressure spikes below the vapor pressure of blood occur in vivo at hyperdynamic physiologic states when this bileaflet pyrolytic carbon valve is implanted in the mitral position. These studies demonstrate the potential for cavitation with implanted mechanical valves in vivo.

Definitive Treatment of Poor-Risk Patients with Stage I Lung Cancer A Single Institution Experience

Purpose: Lung cancer remains the leading cause of cancer death in both men and women. A substantial number of patients with early stage non-small cell lung cancer (NSCLC) are unfit for standard surgery due to cardiopulmonary dysfunction and/or other comorbidity. The appropriate management for this population has not been defined. Methods: Retrospective analysis of patients with clinical stage I NSCLC judged to be unsuitable for lobectomy between 1996 and 2005. Results: Ninety-six patients, representing 23% of all patients treated for clinical stage I NSCLC were included in this analysis. The median age was 73 years and most patients were female. Patients underwent limited resection (LR, n = 45), primary radiotherapy (RT, n = 39) or radiofrequency ablation (n = 12). With median follow-up of 30 months, 61 patients remain alive. Actuarial 3-year survival is 65% following LR and 60% after primary RT. Local tumor relapse and distant metastases were observed with approximate equal probability following either LR or RT. Conclusion: Medical inoperability does not necessarily correspond to poor survival in patients with early stage NSCLC. A nihilistic approach is not warranted towards this population, and prospective trials are needed to better define optimal treatment strategies.

Prospective Trial of Thoracic and Spine Surgeons' Updating of Their Estimated Case Durations at the Start of Cases

BACKGROUND:Surgeon estimates of case durations are important for operating room (OR) management decision making because many cases are rare combinations of procedures with few or no historical data. Thoracic and spine surgeons updated their scheduled OR times on the day of surgery just before the “time out” in the OR. METHODS:All elective (scheduled) general thoracic (n = 39) and spine surgery (n = 48) cases at 1 hospital were studied over 3-month and 1.5-month periods, respectively. RESULTS:Among cases with a change in predicted duration, most changes were made based on updates to the surgical or anesthetic procedures (thoracic 85%, spine 86%). For thoracic surgery, there was overall no significant median reduction in absolute prediction error (median 0 minutes, 95% confidence interval [CI] 0–0 minutes). Among the 37% of cases with changed predicted durations, there was a significant reduction in absolute error (median 38 minutes, 95% CI >7.5 minutes). For spine surgery, there was overall no reduction in the absolute error (median 0 minutes, 95% CI 0–0 minutes). Among the 29% of cases with changed predicted durations, absolute error was no worse, but not significantly better (point estimate of median reduction 34 minutes, 95% CI >0 minutes). Secondary observations made were no effect of updates on bias, frequent rounding of scheduled durations to the nearest half hour, and increased predictive error caused by decisions that reduced expected overutilized OR time. CONCLUSIONS:A systematic program of routinely and/or always asking for updated case duration predictions will not substantively improve OR management decision making. However, when a change in surgical approach, surgical procedure, or anesthetic procedure is identified (e.g., at the intraoperative briefing before case start), the updated estimate of case duration should be used, because such updates are not worse and often better than original estimates.

Application of a similarity index to state discharge abstract data to identify opportunities for growth of surgical and anesthesia practices.

INTRODUCTION: Most surgical and anesthesia groups are interested in expanding their practices and recruiting more patients. Methods have been developed to help hospitals identify surgical specialties with the potential for growth by determining whether the hospital is performing fewer of certain types of procedures than expected in a given specialty. However, these methods are not appropriate for physicians who may practice at more than one hospital and want to determine the potential for growth in their regions. METHODS: We examined potential markets for growth of surgical and anesthesia practices in Iowa and New York State using state discharge abstract data. Several patient demographic groups and several surgical specialties were examined. Each state was divided into regions, and data were analyzed three ways: (1) A similarity index compared each region to the rest of the state. (2) The number of procedures performed on patients who left their home regions for care was determined. (3) A similarity index compared procedures performed on patients who left their home regions for care with procedures performed on patients who remained within their home regions. RESULTS: The methods successfully identified several geographic regions with previously unrecognized growth potential. Access to care was limited in these regions. The methods correctly showed few opportunities for growth in geographic regions where expansion was already known to be unlikely. CONCLUSIONS: A count of the number of procedures performed on patients who left their home regions, in combination with the similarity index, is a useful method for screening state discharge abstract data to identify geographic regions where surgical and anesthesia practices could grow.

Laparoscopic excision of gastric mass yields intra-abdominal esophageal duplication cyst.

A 69-year-old man with presumed solid gastric mass determined by computed tomography, endoscopic ultrasonography, and fine-needle aspiration underwent videoscopic excision of what resulted in a cystic structure consistent with intra-abdominal esophageal duplication cyst. Esophageal duplication cysts are rare congenital lesions that are difficult to diagnose. They seldom occur entirely below the diaphragm, and occurrence in adults is unusual. Only six such cases are reported in the literature. When diagnosis is made, treatment decisions are not always straight forward, although excision is frequently pursued. The current case describes this unique finding and presents laparoscopic excision as a safe treatment alternative.