Management of Enlarging Tracheoesophageal Fistula with Voice Prosthesis in Laryngectomized Patients.

Management of Enlarging tracheoesophageal fistula (TEF) with Voice Prosthesis in Laryngectomized Head and Neck Cancer Patients. OBJECTIVES: An enlarging TEF following voice prosthesis placement impacts patient quality of life, risks airway compromise, and can lead to aspiration pneumonia. Pharyngoesophageal strictures have previously been reported to be associated with TEF enlargement and leakage. We describe a series of patients with enlarging TEFs after Tracheoesophageal puncture (TEP) for voice prosthesis who required pharyngoesophageal reconstruction. METHODS: Retrospective case series of laryngectomized H&N cancer patients with primary or secondary TEP who underwent surgical management for enlarging TEF site between 6/2016-11/2022. RESULTS: Eight patients were included. The mean age was 62.8 years old. Seven patients had a history of hypothyroidism. Of seven with prior H&N radiation history, two had both historical and adjuvant radiation. Two of the eight TEPs were placed secondarily. Mean time from TEP to enlarging TEF diagnosis was 891.3 days. Radial forearm-free flaps were used in five patients. Six had stenosis proximal to the TEF whereas one had distal stenosis and one had no evidence of stenosis. Mean length of stay was 12.3 days. Mean follow-up was 400.4 days. Two required a second free flap for persistent fistula. CONCLUSION: Surgical reconstruction of enlarging TEFs due to TEP/VP placement is effective in combination with addressing underlying pharyngeal/esophageal stenosis contributing to TEF enlargement and leakage. Radial forearm-free flaps have the additional benefit of a long vascular pedicle to access more distant and less-irradiated recipient vessels. Many fistulae are resolved after the first flap reconstruction, but some may require subsequent reconstruction in case of failure. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:198-206, 2024.

Cost-analysis of in-office versus operating room sialendoscopy: Comparison of cost burden and outcomes.

PURPOSE: Office-based procedures in otolaryngology are increasingly utilized to increase efficiency, reduce cost, and eliminate risks associated with surgery. Gland-preserving surgical management of sialadenitis and sialolithiasis are often performed in the operating room, although many surgeons are moving this practice to clinic. We aim to determine the difference in patient charges and perioperative outcomes for salivary gland procedures performed in the clinic versus the OR. METHODS: Retrospective series of patients presenting with sialolithiasis, acute or chronic sialadenitis, and stricture between 2010 and 2019. Demographics, perioperative variables, setting, and charge data were collected. RESULTS: 528 patients underwent operative intervention (n = 427 office, n = 101 OR). Cohort demographics were comparable. Sialolithiasis was the most common presenting diagnosis in both cohorts. Both cohorts had similar rates of complete (p = 0.09) and partial (p = 0.97) response to treatment. A higher percentage of patients in the OR group reported no improvement (21.4 vs 12.2%, p = 0.034). Overall complications were similar (p = 0.582). Mean charges were statistically greater in the OR ($5560.35 OR vs $1298.33 office, p < 0.001). Operative time was significantly reduced in the office group (21.8 min vs 60.85 min, p < 0.001). CONCLUSIONS: Appropriately selected patients can be successfully treated in outpatient clinic without compromising patient safety or quality while significantly reducing the financial burden to patients and the healthcare system.

Head and neck osteosarcomas: Analysis of treatment trends and survival outcomes in the United States (2004-2016).

BACKGROUND: Head and neck osteosarcoma (HNOS) is a rare primary bone tumor with limited data to guide treatment approaches. METHODS: The NCDB was used to identify patients diagnosed with HNOS. Kaplan-Meier and Cox multivariate regression were used to examine the impact of each treatment on overall survival (OS). RESULTS: We identified 821 patients diagnosed with HNOS. Utilization of neoadjuvant chemotherapy + surgery increased from zero cases in 2004 to 24% of cases in 2016. Among surgically treated patients, 5-year OS was 55.8% (CI: 51.7-60.1%). No difference was seen in OS between each treatment cohort on multivariate analysis. However, neoadjuvant chemotherapy + surgery + adjuvant chemotherapy had improved 18-month survival compared to surgery alone (95.8% vs. 78.5%, p = 0.031). CONCLUSIONS: Our study demonstrated no survival benefit in perioperative chemotherapy or radiation therapy; however, short-term survival improvement in patients receiving both neoadjuvant and adjuvant chemotherapy displays promise and requires further investigation.

Transoral robotic surgery versus nonrobotic resection of oropharyngeal squamous cell carcinoma.

The aim of this study is to evaluate the impact of transoral robotic surgery (TORS) compared to nonrobotic surgery (NRS) on overall survival in oropharyngeal squamous cell carcinoma (OPSCC). We performed a retrospective study of patients with HPV+ and HPV- OPSCC undergoing TORS or NRS with neck dissection using the National Cancer Database from the years 2010-2016. Among patients with OPSCC in our cohort, 3167 (58.1%) patients underwent NRS and 2288 (41.9%) underwent TORS. TORS patients demonstrated better overall survival than NRS patients (HPV+ patients: aHR 0.74, p = 0.02; HPV- patients: aHR 0.58, p < 0.01). Subsite analysis showed TORS was correlated with improved survival in base of tongue (BoT) primaries for both HPV+ (aHR 0.46, p = 0.01) and HPV- (aHR 0.42, p = 0.01) OPSCC. Compared to NRS, TORS is associated with improved overall survival for HPV+ and HPV- OPSCC, as well as greater overall survival for BoT primaries.

Prevalence of Sensorineural Hearing Loss in Pediatric Patients with Sickle Cell Disease: A Meta-analysis.

OBJECTIVES: To determine the prevalence of Sensorineural Hearing Loss (SNHL) attributable to Sickle Cell Disease (SCD) in the global pediatric population and to identify factors contributing to its severity. STUDY DESIGN: Meta-analysis. METHODS: We performed a comprehensive literature search for scientific articles in PubMed, Scopus, CINAHL, Web of Science, and the Cochrane Library that reported the incidence of hearing loss in populations under 18 years of age with excluding studies analyzing patients on iron chelation therapy, adults, or those without objective audiological analysis. RESULTS: We identified 138 initial studies with 17 selected for analysis after applying the exclusion criteria. A total of 1,282 SCD patients and 553 controls were included in the meta-analysis. There was a statistically significant increase in the prevalence of SNHL in children with SCD compared to the general population with a cumulative risk ratio of 3.33. CONCLUSION: This is the first systematic investigation of the relationship between SCD and SNHL in pediatric patients across the globe. The increased prevalence of SNHL in the pediatric SCD population warrants future research into the predictors of SNHL severity and merits routine audiometric monitoring of SCD patients to reduce the social and developmental morbidity of hearing loss at a young age. PROSPERO Registration #: CRD42019132601. Laryngoscope, 131:1147-1156, 2021.

Characterization of Sensorineural Hearing Loss in Adult Patients With Sickle Cell Disease: A Systematic Review and Meta-analysis.

OBJECTIVES AND MAIN OUTCOME MEASURES: To determine the prevalence of sensorineural hearing loss (SNHL) attributable to sickle cell disease (SCD) in the global adult population and to identify factors contributing to its severity. STUDY DESIGN: Systematic Review and Meta-analysis. METHODS: We performed a comprehensive literature search for scientific articles in PubMed, Scopus, CINAHL, Web of Science, and the Cochrane Library that reported the incidence of hearing loss in populations over 18 years of age with SCD. RESULTS: We identified 138 studies from the initial search, 12 of which met inclusion criteria and were utilized for data analysis. A total of 636 SCD patients and 360 controls were included in the Cochrane Review Manager 5.3 meta-analysis. There was a statistically significant increase in the prevalence of SNHL in adults with SCD compared with the general population with a cumulative risk ratio (RR) of 6.03. CONCLUSIONS: This is the first systematic investigation of the relationship between SCD and SNHL in adult patients across the globe. SNHL is more prevalent in patients with SCD, specifically those of the HbSS genotype, than the general population likely due to the pathophysiology of the disease and its effects on labyrinthine microvasculature. The increased prevalence of SNHL in the adult SCD population warrants future research into the predictors of SNHL severity and merits routine audiometric monitoring of adult SCD patients.

Pediatric head and neck rhabdomyosarcoma: An analysis of treatment and survival in the United States (1975-2016).

INTRODUCTION: Rhabdomyosarcoma (RMS) is the most common soft tissue head and neck sarcoma in children. Stringent analysis of survival data is imperative to optimize treatment. METHODS: The National Cancer Database (NCDB, 2004-2016) and the Surveillance, Epidemiology, and End Results Program (SEER, 1975-2016) were queried for patients ages 0-19 with RMS of the head and neck. Survival trends were analyzed using univariable logistic regression and Chi-square pairwise comparisons. Survival by treatment was analyzed using log-rank tests, Kaplan Meier, and multivariable Cox-proportional hazards regression. RESULTS: 1147 (63.3% age <10 years, 54.3% male) and 459 (71.4% age <10 years, 53.6% male) patients were identified in NCDB and SEER, respectively. In NCDB, embryonal (n = 625, 54.5%) and alveolar (n = 300, 26.2%) were the most common histology and nonparameningeal/non-orbital (n = 634, 55.3%), followed by parameningeal (n = 303, 26.4%) and orbital (n = 210, 18.3%) the most common location. Five-year overall survival (OS) was 70.3% with lower mortality risk for embryonal histology (adjusted HR [aHR] = 0.69, p = 0.0038). Orbital tumors had greatest survival (5-year OS = 92.4%) of all sites, and their mortality risk was higher with chemotherapy and radiation compared to surgery and radiation (aHR = 6.27, p = 0.0302). SEER analysis showed average increased survival by 4% per year (p < 0.0001), but no significant 5-year OS difference when comparing 1976-1980 and 2006-2010 (p = 0.0843). CONCLUSIONS: Major prognostic factors for survival in childhood RMS of the head and neck were embryonal histology, orbital site, extent of disease, and use of SRT for orbital tumors. Larger population studies are required to demonstrate survival differences between treatment modalities for other sites.

Hold the Salt: History of Salt Restriction as a First-line Therapy for Menière's Disease.

OBJECTIVES: To determine the historical origins of the usage of the salt restriction diet as an intervention for Menière's disease (MD). METHODS: Articles on MD and salt restriction were identified using Pubmed and Google scholar. Original manuscripts from 19th and 20th century as well as selected otological textbooks in English, German, and French were also reviewed. RESULTS: The oldest recommendation of salt restriction in the literature was by Dederding (1889-1955) in 1929. She and her mentor, Sydney Holger Mygind (1884-1970), believed MD was caused by dysfunctional water metabolism. In several published manuscripts, they proposed that a reduced salt and fluid diet was an effective treatment for MD. Their contemporaries supported their findings, most notably, Albert C. Furstenberg (1890-1969) who suggested salt restriction alone as treatment for MD. Furstenberg, in his initial study implementing salt restriction in 15 patients with MD and then in a larger study with 150 patients, was the first to produce results that supported salt restriction as therapy for MD. It was not until 1980, when LB Jongkees first published his criticism of this treatment, that salt restriction was questioned. Since then, numerous published articles have been critical of salt restriction therapy and skeptical of its initial adoption into clinical practice. CONCLUSIONS: Since Dederding's and Mygind's publications in 1929 and Furstenberg's trial in 1934, the salt restriction diet has remained a primary first-line treatment for MD. Since the 1950s, various publications have both supported and argued this treatment, and the evidence of its validity remains inconclusive.

The impact of chronic kidney disease on postoperative complications in patients undergoing revision total knee arthroplasty: A propensity matched analysis.

OBJECTIVES: Though the role of chronic kidney disease (CKD) has been studied previously in primary arthroplasty procedures of the hips and knees, there is a paucity of literature analyzing CKD's impact on surgical outcomes in revision total knee arthroplasty (rTKA) patients. As the number of patients with CKD requiring revision surgery increases, more vigilant pre-operative and post-operative measures can be taken to ensure successful outcomes. This retrospective study sought to 1) determine differences in demographics and preoperative comorbidities of patients with normal or mild CKD and those with moderate/severe CKD and 2) establish moderate/severe CKD as an independent risk factor for complications in the 30-day postoperative period in patients undergoing rTKA. METHODS: The ACS-NSQIP database was queried for patients who had undergone rTKA from 2005 to 2016. Patient were assigned to one of five CKD severity classes after eGFR calculation and were further stratified into two cohorts: stages 1/2 vs. stages 3/4/5. After propensity matching to generate a matched normal/mild CKD cohort of rTKA patients, univariate and multivariate analyses were used to assess differences and the impact of severe CKD on the risk for complications. RESULTS: There were significant differences in several demographic features, comorbidities, and complications between the two cohorts upon univariate analyses. Upon multivariate analyses, CKD of moderate/severe/failure status was found to be a significant independent risk factor for acute renal failure (OR 18.097, 95% CI 4.970-65.902, p < 0.001), blood transfusions (OR 1.697, 95% CI 1.500-1.919, p < 0.001), return to the operating room (OR 1.257, 95% CI 1.009-1.566, p = 0.041), extended length of stay (OR 1.707, 95% CI 1.292-2.255, p < 0.001), and mortality (OR 2.165, 95% CI 1.116-4.200, p = 0.022) in the 30-day postoperative period. CONCLUSION: This current study found moderate/severe CKD to be an independent risk factor for several complications and should guide healthcare professionals for better patient-optimization. Orthopaedic surgeons should factor in CKD severity in the management of patients undergoing rTKA to effectively mitigate the effects of adverse events.

Sedation withdrawal following single stage laryngotracheal reconstruction: Does dexmedetomidine help?

OBJECTIVES: Single-stage laryngotracheal reconstruction (SS-LTR) requires a period of post-operative intubation, during which time adequate sedation is needed to ensure graft healing. Commonly used agents include benzodiazepines, opioids, and more recently, dexmedetomidine, a centrally-acting α2 adrenoreceptor. This study aims to compare withdrawal outcomes between various sedation regimens following SS-LTR. METHODS: Retrospective chart review of 56 patients who underwent SS-LTR between 2008 and 2018 at a tertiary free-standing children's hospital was performed. Of 47 patients with complete records, 18 patients received dexmedetomidine for >75% of their intubation period with midazolam (DexWM), 9 received dexmedetomidine for >75% without midazolam (DexWOM), and 20 received dexmedetomidine for <75% with midazolam (noDex). RESULTS: There was no significant difference in length of PICU or hospital stay between the groups. The noDex group trended toward a higher re-intubation rate of 25%, as compared with 11% of DexWOM and 5.6% of DexWM (p = 0.21). There was no significant difference in days of oral sedation taper required or Withdrawal Assessment Tool (WAT-1) score for post-extubation days 1 and 3. By post-extubation day 5, 100% of the DexWM group had WAT-1 scores <3 as compared with 71.4% of the noDex group (p = 0.037). Notably, lower average daily doses of dexmedetomidine and midazolam were used in the DexWM group, as compared with the DexWOM and noDex groups, respectively. CONCLUSION: Dexmedetomidine as a primary sedation agent with midazolam allows for adequate sedation following SS-LTR. The combination of the two drugs in the DexWM group not only reduced the dosage of each drug needed, but also significantly improved WAT-1 scores by post-extubation day 5, as compared with the alternative sedation regimens.

Quality of life outcomes following velopharyngeal insufficiency surgery.

OBJECTIVES: Velopharyngeal insufficiency (VPI) may be due to functional or anatomic causes, and can lead to speech deficits, communication difficulty, and emotional strain on patients and their caregivers. The VPI Effects on Life Outcomes (VELO) instrument quantifies quality of life outcomes in VPI patients both before and after VPI surgery. This study aims to identify pre-operative patient characteristics associated with better post-operative quality of life. METHODS: This study is a retrospective chart review of 51 patients who underwent VPI surgery between 2009 and 2018 at a tertiary free-standing children's hospital. A 26-item parent-proxy VELO questionnaire was administered by telephone to parents to assess their child's quality of life post-VPI surgery. RESULTS: Twenty-seven parents responded to the VELO questionnaire. Average post-operative VELO score was significantly higher in non-syndromic patients as compared with syndromic patients. Average post-operative VELO score was not significantly different between patients with and without submucous cleft (SMC) or those with mild to moderate versus severe pre-operative hypernasality. On multivariate analysis, absence of genetic syndrome, lack of submucous cleft, and presence of severe-pre-operative hypernasality were significantly and positively associated with increased post-operative VELO scores. CONCLUSION: Children who undergo VPI surgery are more likely to have better post-operative quality of life outcomes if their VPI was not associated with a genetic syndrome or submucous cleft. Non-syndromic and non-SMC patients with severe pre-operative hypernasality may benefit significantly from VPI surgery and have improved post-operative quality of life.

Genicular Nerve Radiofrequency Ablation for Painful Knee Arthritis: The Why and the How.

BACKGROUND: Genicular nerve radiofrequency ablation (GNRFA), including conventional, cooled, and pulsed techniques, has been used in the management of symptomatic knee osteoarthritis (OA). This new and innovative treatment option has the capacity to decrease pain and improve function and quality of life in certain patients. GNRFA is reserved for patients with symptomatic knee OA who have had failure of conservative treatment and have had failure of or are poor candidates for surgery. GNRFA has been shown to consistently provide short-term (3 to 6-month), and sometimes longer, pain relief in patients. GNRFA has been demonstrated to be safe to administer repeatedly in patients who respond well to this minimally invasive procedure. DESCRIPTION: GNRFA is a 2-step procedure. First, patients are given a diagnostic block under fluoroscopy or ultrasound guidance. Specifically, 1 mL of lidocaine is injected using a 20-gauge, 3.5-in (8.9-cm) spinal needle around the superior lateral, superior medial, and inferior medial genicular nerve branches. The diagnostic block is extra-articular. If the patient reports a ≥50% reduction in baseline pain for a minimum of 24 hours following the injection, then the patient is a candidate for genicular ablation. The osseous landmarks for the diagnostic block are exactly the same as for the ablation procedure. Both procedures are well tolerated in the office setting under local skin anesthesia or can be done in the operating room under conscious sedation using a low-dose sedative such as midazolam for anxious patients. General anesthesia is not required for GNRFA. This procedure is most commonly performed by interventional pain specialists but may also be performed by any physician with appropriate training. In some jurisdictions, physician assistants and nurse practitioners may perform this procedure subject to their supervision requirements. ALTERNATIVES: Conservative treatment for symptomatic knee OA includes weight loss management, physical and aquatic therapy, bracing, lateral wedge insoles, transcutaneous nerve stimulation, nonsteroidal anti-inflammatory drugs in combination with a proton pump inhibitor, autologous blood-based therapies, and cortisone and hyaluronic acid injections1,2. Surgical treatment for symptomatic knee OA includes knee arthroscopy, high tibial osteotomy, total knee replacement, and unicompartmental knee replacement in patients without lateral compartment disease2. It should be noted that there is some evidence suggesting that steroid injection, viscosupplements, and arthroscopy are not effective for the management of knee OA. RATIONALE: Thermal GNRFA differs from all other treatment alternatives because this procedure causes denaturing of the 3 sensory nerves primarily responsible for transmitting knee pain from an arthritic joint to the central nervous system. In this procedure, heating occurs from an intense alternating electrical field at the tip of the cannula, which produces sufficient heat to denature the proteins in the target tissue. The accepted heating parameters for this procedure are 70° to 80°C for 60 or 90 seconds. A commonly raised question is whether this procedure precipitates a Charcot-type joint. The Charcot joint involves much more than reduced innervation; it occurs in the context of chronically compromised vascularity and altered soft-tissue characteristics as well as peripheral neuropathy. Moreover, a Charcot-type joint does not develop because the deafferentation of the weight-bearing joint is partial3. To our knowledge, no Charcot-type joints have been reported after this procedure. Conversely, data from an animal study have shown that selective joint denervation may lead to the progression of knee OA4. The ablation procedure is done outside the knee joint, unlike alternatives such as intra-articular therapies and surgery. The effectiveness of nonsurgical knee OA interventions in alleviating pain and improving joint function is generally inadequate1. However, GNRFA appears to be an emerging alternative for patients who have had failure of conservative and surgical treatments. It is not uncommon in our clinical practice for patients to achieve adequate pain control following ablation for up to 1 year. GNRFA provides temporary relief from symptomatic knee OA because it does not eliminate the potential for peripheral nerve regrowth and regeneration, and thus pain, to return.

Classifying highly imbalanced ICU data.

Highly imbalanced data sets are those where the class of interest is rare. In this paper, we compare the performance of several common data mining methods, logistic regression, discriminant analysis, Classification and Regression Tree (CART) models, C5, and Support Vector Machines (SVM) in predicting the discharge status (alive or deceased, with "deceased" being the class of interest) of patients from an Intensive Care Unit (ICU). Using a variety of misclassification cost ratio (MCR) values and using specificity, recall, precision, the F-measure, and confusion entropy (CEN) as criteria for evaluating each method's performance, C5 and SVM performed better than the other methods. At a MCR of 100, C5 had the highest recall and SVM the highest specificity and lowest CEN. We also used Hand's measure to compare the five methods. According to Hand's measure, logistic regression performed the best. This article makes several contributions. We show how the use of MCR for analyzing imbalanced medical data significantly improves the method's classification performance. We also found that the F-measure and precision did not improve as the MCR was increased.

Observations on surgical demand time series: detection and resolution of holiday variance.

BACKGROUND: Surgical scheduling is complicated by both naturally occurring and human-induced variability in the demand for surgical services. Surgical demand time series are decomposed into periodic, lagged, and linear trends with frequent occurrences of nonconstant variations in mean and variance. The authors used time series methods to model surgical demand time series in order to improve the scheduling of scarce surgical resources. METHODS: With institutional approval, the authors studied 47,752 surgeries undertaken at a large academic medical center. They initially extracted periodic information from the time series using two frequency domain techniques: the harmonic F test and the multitaper test. They subsequently extracted lagged (correlated) behavior using a seasonal autoregressive integrated moving average model. Finally, they used moving variance filters on the residuals to identify variance in the time series that coincided with major US holidays. RESULTS: Linear terms such as periodic cycles, trends, and daily and weekly lags explained 80% of the variance in the raw time series. In the residuals, the authors used moving variance filters to detect nonlinear variance artifacts that correlated with surgical activities on specific US holidays. CONCLUSIONS: After extracting linear terms, the remaining variance was attributable to a combination of nonlinear and unexplained random events. The authors used the term holiday variance to describe a specific nonlinear disturbance in surgical demand attributable to statutory US holidays. Resolving these holiday variances may assist in management and scheduling of scarce surgical personnel and resources.

Corrected QT interval prolongation after an overdose of escitalopram, morphine, oxycodone, zopiclone and benzodiazepines.

Escitalopram is the recently marketed S-enantiomer of the widely used antidepressant citalopram. Data from intentional overexposure to this medication are limited. Twelve-lead electrocardiogram (ECG) effects from racemic citalopram have been described; however, the present report is the first, to the best of the authors' knowledge, that describes all the reported abnormalities in a single patient receiving escitalopram. A 52-year-old man with a history of depression treated with escitalopram 10 mg/day, extended-release morphine 30 mg/day and zopiclone 15 mg/day was found unconscious at his home. He was known to have attempted suicide three weeks previously. Partially emptied bottles of escitalopram, morphine, oxycodone, zopiclone, lorazepam and diazepam were found close to the patient. He was transferred to the emergency department, where airway management and other supportive care were initiated. The patient was transferred to the intensive care unit. The initial 12-lead ECG demonstrated junctional rhythm at 48 beats/min, a wide complex escape (145 ms) with right bundle branch morphology and a prolonged corrected QT interval at 650 ms. Cardiac monitoring was undertaken. No ventricular arrhythmias or torsade de pointes were detected. No specific treatment for shortening the QT was implemented. Another 12-lead ECG performed 48 h later demonstrated sinus tachycardia with a normal corrected QT, normal PR interval and normal QRS duration. The effects of the overdose of escitalopram on the ECG and its interactions with other drugs are reviewed.

Modeling ischemia-induced dyssynchronous myocardial contraction.

Left ventricular (LV) contraction dyssynchrony is not easily quantified. We previously described a model for quantifying LV dyssynchrony that referenced regional amplitude and phase angles to global LV systole using esmolol-induced regional dyskinesis. We tested the hypothesis that our sine wave model and phase angle analysis of regional dyssynchrony in a canine model could also assess dyssynchrony of contraction during regional ischemia. Hence we compared intracoronary esmolol and matched regional ischemia in 10 anesthetized open-chest dogs. Regional and total LV volumes (conductance catheter), piezoelectric crystal shortening, and LV pressures were measured before, during, and after esmolol-induced apical dyskinesis and matched regional ischemia. We defined regional phase angle of contraction (alpha) as the relative distance, measured in degrees, that regional minimal volume differed from global end-systole. We also compared maximal stroke volume (SV), observed effective SV (that portion of regional SV contributing to total SV for each treatment), and calculated effective SV (total regional SV x cosine alpha). Dobutamine infusion increased homogeneity of regional alpha relative to baseline. Both esmolol and ischemia significantly delayed (P < 0.05) apical contraction as quantified by increased alpha (12.4 degrees +/- 28.1 degrees to 27.4 degrees +/- 30.4 degrees and 54.2 degrees +/- 32.6 degrees , respectively) (mean +/- sd) and decreased regional effective SV (4.7 +/- 2.5 mL to 3.6 +/- 2.2 mL and 4 +/- 2.5 mL, respectively) relative to baseline. Our study indicates that intracoronary esmolol and ischemia induced qualitatively similar mechanical effects on myocardial function and that a sine wave model to estimate regional effective SV is a sensitive method to detect and quantify regional dyssynchrony induced by ischemia. Potentially, phase angle and regional amplitude analyses may prove to be effective measures to identify and quantify the beneficial effects of resynchronization therapies on myocardial function.

An outpatient segmentation model: estimation of stakeholder costs.

This research describes a constraint-based heuristic model of capacity segmentation for outpatient facilities used to estimate the effect of segmentation constraints on stakeholders. Growth of free-standing ambulatory surgery centres has been dramatic in recent years with institutions being urged by governments and insurers to segment inpatients (IP) and outpatients (OP) to reduce costs and improve services. Critics of segmentation argue it is a false economy to separate inpatients and outpatients since pooling of patients in large IP facilities offers economies of scale and opportunities for parallel processing, not to mention elimination of infrastructure. We implemented a constraint-based heuristic model of capacity segmentation for OP facilities and used it to estimate the effect of segmentation on stakeholders.