Generalized cost-effectiveness analysis to assess treatment value in hepatitis C.

OBJECTIVES: To estimate the comprehensive value of direct-acting antivirals (DAAs) for the treatment of hepatitis C virus (HCV) compared with peginterferon alfa and ribavirin (PEG/riba) employing a generalized cost-effectiveness analysis (GCEA). STUDY DESIGN: To assess the societal-level cost-effectiveness of DAA treatment for HCV, we extended a previously published discrete-time Markov simulation model of HCV transmission and progression to include market dynamics and broader elements of value. METHODS: We followed a stepwise process to add novel value elements to a traditional CEA model for HCV treatments. For each additional element of value, we estimated incremental cost-effectiveness ratios (ICERs) of DAAs compared with PEG/riba. RESULTS: The health technology assessment (HTA)-style model yielded an ICER value of $64,512 per quality-adjusted life-year (QALY). Adding transmission dynamics resulted in an ICER value of $52,971 per QALY, whereas accounting for transmission dynamics and dynamic price and efficacy further decreased ICER values by 90% to $6406 per QALY. Incorporating genericization, productivity loss, caregiver spillover, and differential valuations of LYs vs quality of life, disease severity, and insurance value further decreased the ICER value to $4487 per QALY, a 93% reduction from the baseline HTA-style CEA to the fully realized GCEA. CONCLUSIONS: Our GCEA study results confirm that DAAs are a cost-effective treatment for HCV compared with PEG/riba even when using conventional cost-effectiveness approaches. Incorporating broader elements of value resulted in more than a 10-fold improvement in cost-effectiveness, emphasizing the substantive impact of a generalized approach and the importance of incorporating GCEAs into decision-making.

Estimating Productivity Loss from Breast and Non-Small-Cell Lung Cancer among Working-Age Patients and Unpaid Caregivers: A Survey Study Using the Multiplier Method.

Background. Traditional approaches to capturing health-related productivity loss (e.g., the human capital method) focus only on the foregone wages of affected patients, overlooking the losses caregivers can incur. This study estimated the burden of productivity loss among breast cancer (BC) and non-small-cell lung cancer (NSCLC) patients and individuals caring for such patients using an augmented multiplier method. Design. A cross-sectional survey of BC and NSCLC patients and caregivers measured loss associated with time absent from work (absenteeism) and reduced effectiveness (presenteeism). Respondents reported pre- and postcancer diagnosis income, hours worked, and time to complete tasks. Exploratory multivariable analyses examined correlations between respondents' clinical/demographic characteristics-including industry of employment-and postdiagnosis productivity. Results. Of 204 patients (104 BC, 100 NSCLC) and 200 caregivers (100 BC, 100 NSCLC) who completed the survey, 319 participants (162 BC, 157 NSCLC) working ≥40 wk/y prediagnosis were included in the analysis. More than one-third of the NSCLC (33%) and BC (43%) patients left the workforce postdiagnosis, whereas only 15% of caregivers did. The traditional estimate for the burden of productivity loss was 66% lower on average than the augmented estimate (NSCLC patients: 60%, BC patients: 69%, NSCLC caregivers: 59%, and BC caregivers: 73%). Conclusions. Although patients typically experience greater absenteeism, productivity loss incurred by caregivers is also substantial. Failure to account for such impacts can result in substantial underestimation of productivity gains novel cancer treatments may confer by enabling patients and caregivers to remain in the workforce longer. Our results underscore the importance of holistic approaches to understanding this impact on both patients and their caregivers and accounting for such considerations when making decisions about treatment and treatment value. Highlights: Cancer can have a profound impact on productivity. This study demonstrates how the disease affects not only patients but also the informal or unpaid individuals who care for patients.An augmented approach to calculating health-related productivity loss suggests that productivity impacts are much larger than previously understood.A more comprehensive understanding of the economic burden of cancer for both patients and their caregivers suggests the need for more support in the workplace for these individuals and a holistic approach to accounting for these impacts in treatment decision making.

Patient preferences for treatment in relapsed/refractory diffuse large B-cell lymphoma: a discrete choice experiment.

Aim: We quantified patient preferences for second-line diffuse large B-cell lymphoma therapies, including attributes of chimeric antigen receptor (CAR) T-cell therapy. Materials & methods: Using a discrete choice experiment, we surveyed 224 diffuse large B-cell lymphoma patients from the USA and Europe. Patients chose between two treatment options defined by six attributes with predefined levels for overall survival, adverse events (severe cytokine-release syndrome, severe neurological toxicities, severe infection) and time to return to pre-treatment functioning. Results: Increasing the probability of 1-year survival was most important to patients, followed by avoiding risks of cytokine-release syndrome and neurological toxicities. Respondents required a 13-14 percentage point increased 1-year survival probability to accept risks of treatment-associated adverse events. Conclusion: Patients prioritize survival and will accept certain adverse event risks to gain survival improvements.

Chimeric antigen receptor (CAR) T-cell therapy is a new treatment for patients with diffuse large B-cell lymphoma. CAR T-cell therapies are made from a patient's own cells, modified in a laboratory and used to attack cancer cells. While CAR T-cell therapies may increase long-term survival, they can also cause temporary but serious side effects, including neurological issues (e.g., headache, confusion, brain swelling) and cytokine-release syndrome (CRS), an inflammatory condition that can cause fever, breathing difficulties and organ dysfunction. To understand how patients' perspectives of CAR T-cell therapy compared with their perspectives on other treatments for diffuse large B-cell lymphoma, we surveyed 224 patients in the USA and Europe. They were asked to choose between two treatments in a series of choice sets, each displaying varying levels of aspects of cancer therapies, including survival and risks of serious side effects. Their choices allowed us to measure which factors were most important to patients when making decisions about treatment. We found that increasing the probability of survival was most important, followed by avoiding risks of neurological complications and CRS. Patients were willing to accept increased risks of neurological toxicities and CRS if they could obtain a 13­14 percentage point increase in the probability of surviving for at least 1 year after treatment.

Effect of Global Ventilation to Perfusion Ratio, for Normal Lungs, on Desflurane and Sevoflurane Elimination Kinetics.

BACKGROUND: Kinetics of the uptake of inhaled anesthetics have been well studied, but the kinetics of elimination might be of more practical importance. The objective of the authors' study was to assess the effect of the overall ventilation/perfusion ratio (VA/Q), for normal lungs, on elimination kinetics of desflurane and sevoflurane. METHODS: The authors developed a mathematical model of inhaled anesthetic elimination that explicitly relates the terminal washout time constant to the global lung VA/Q ratio. Assumptions and results of the model were tested with experimental data from a recent study, where desflurane and sevoflurane elimination were observed for three different VA/Q conditions: normal, low, and high. RESULTS: The mathematical model predicts that the global VA/Q ratio, for normal lungs, modifies the time constant for tissue anesthetic washout throughout the entire elimination. For all three VA/Q conditions, the ratio of arterial to mixed venous anesthetic partial pressure Part/Pmv reached a constant value after 5 min of elimination, as predicted by the retention equation. The time constant corrected for incomplete lung clearance was a better predictor of late-stage kinetics than the intrinsic tissue time constant. CONCLUSIONS: In addition to the well-known role of the lungs in the early phases of inhaled anesthetic washout, the lungs play a long-overlooked role in modulating the kinetics of tissue washout during the later stages of inhaled anesthetic elimination. The VA/Q ratio influences the kinetics of desflurane and sevoflurane elimination throughout the entire elimination, with more pronounced slowing of tissue washout at lower VA/Q ratios.

Arterial and Mixed Venous Kinetics of Desflurane and Sevoflurane, Administered Simultaneously, at Three Different Global Ventilation to Perfusion Ratios in Piglets with Normal Lungs.

BACKGROUND: Previous studies have established the role of various tissue compartments in the kinetics of inhaled anesthetic uptake and elimination. The role of normal lungs in inhaled anesthetic kinetics is less understood. In juvenile pigs with normal lungs, the authors measured desflurane and sevoflurane washin and washout kinetics at three different ratios of alveolar minute ventilation to cardiac output value. The main hypothesis was that the ventilation/perfusion ratio (VA/Q) of normal lungs influences the kinetics of inhaled anesthetics. METHODS: Seven healthy pigs were anesthetized with intravenous anesthetics and mechanically ventilated. Each animal was studied under three different VA/Q conditions: normal, low, and high. For each VA/Q condition, desflurane and sevoflurane were administered at a constant, subanesthetic inspired partial pressure (0.15 volume% for sevoflurane and 0.5 volume% for desflurane) for 45 min. Pulmonary arterial and systemic arterial blood samples were collected at eight time points during uptake, and then at these same times during elimination, for measurement of desflurane and sevoflurane partial pressures. The authors also assessed the effect of VA/Q on paired differences in arterial and mixed venous partial pressures. RESULTS: For desflurane washin, the scaled arterial partial pressure differences between 5 and 0 min were 0.70 ± 0.10, 0.93 ± 0.08, and 0.82 ± 0.07 for the low, normal, and high VA/Q conditions (means, 95% CI). Equivalent measurements for sevoflurane were 0.55 ± 0.06, 0.77 ± 0.04, and 0.75 ± 0.08. For desflurane washout, the scaled arterial partial pressure differences between 0 and 5 min were 0.76 ± 0.04, 0.88 ± 0.02, and 0.92 ± 0.01 for the low, normal, and high VA/Q conditions. Equivalent measurements for sevoflurane were 0.79 ± 0.05, 0.85 ± 0.03, and 0.90 ± 0.03. CONCLUSIONS: Kinetics of inhaled anesthetic washin and washout are substantially altered by changes in the global VA/Q ratio for normal lungs.

Simulating the Fiscal Impact of Anti-Obesity Medications as an Obesity Reduction Strategy.

While substantial public health investment in anti-smoking initiatives has had demonstrated benefits on health and fiscal outcomes, similar investment in reducing obesity has not been undertaken, despite the substantial burden obesity places on society. Anti-obesity medications (AOMs) are poorly prescribed despite evidence that weight loss is not sustained using other strategies alone.We used a simulation model to estimate the potential impact of 100% uptake of AOMs on Medicare and Medicaid spending, disability payments, and taxes collected relative to status quo with negligible AOM use. Relative to status quo, AOM use simulation would result in Medicare and Medicaid savings of $231.5 billion and $188.8 billion respectively over 75 years. Government tax revenues would increase by $452.8 billion. Overall, the net benefit would be $746.6 billion. Anti-smoking efforts have had substantial benefits for society. A similar investment in obesity reduction, including broad use of AOMs, should be considered.

CAR-T therapy and historical trends in effectiveness and cost-effectiveness of oncology treatments.

Aim: This study examines how chimeric antigen receptor T-cell (CAR-T) therapy's incremental effectiveness and cost-effectiveness profile fits into the recent history of anticancer treatments. Materials & methods: We conducted graphical and multivariable analyses using data from the Cost-Effectiveness Analysis Registry of the Tufts Medical Center and the Institute for Clinical and Economic Review's analysis of CAR-T therapies. We collected additional information including the US FDA approval years for pharmacologic innovations. Results: CAR-T provided 5.03 (95% CI: 3.88-6.18) more incremental quality-adjusted life-years than the average pharmaceutical intervention and 4.61 (95% CI: 1.67-7.56) more than the average nonpharmaceutical intervention, while retaining similar cost-effectiveness. There was evidence of worsening cost-effectiveness by approval year for pharmaceutical interventions. Limitations: Analysis is limited to anticancer treatments studied in cost-utility analyses, estimated to cover approximately 60% of FDA-approved antineoplastic agents. Conclusion: CAR-T therapy breaks a pattern of stagnant efficacy growth in pharmaceutical innovation and demonstrates significantly greater incremental effectiveness and similar cost-effectiveness to prior innovations.

The Societal Value of Broader Access to Antiobesity Medications.

OBJECTIVE: Obesity and its complications place an enormous burden on society. Yet antiobesity medications (AOM) are prescribed to only 2% of the eligible population, even though few individuals can sustain weight loss using other strategies alone. This study estimated the societal value of greater access to AOM. METHODS: By using a well-established simulation model (The Health Economics Medical Innovation Simulation), the societal value of AOM for the cohort of Americans aged ≥ 25 years in 2019 was quantified. Four scenarios with differential uptake among the eligible population (15% and 30%) were modeled, with efficacy from current and next-generation AOM. Societal value was measured as monetized quality of life, productivity gains, and savings in medical spending, subtracting the costs of AOM. RESULTS: For the 217 million Americans aged ≥ 25 years, AOM generated $1.2 trillion in lifetime societal value under a conservative scenario (15% annual uptake using currently available AOM). The introduction of next-generation AOM increased societal value to $1.9 to $2.5 trillion, depending on uptake. Finally, societal value was higher for younger individuals and Black and Hispanic individuals compared with White individuals. CONCLUSIONS: This study suggests that AOM provide substantial gains to patients and society. Policies promoting broader clinical access to and use of AOM warrant consideration to reach national goals to reduce obesity.

PO2 oscillations induce lung injury and inflammation.

BACKGROUND: Mechanical ventilation can lead to ventilator-induced lung injury (VILI). In addition to the well-known mechanical forces of volutrauma, barotrauma, and atelectrauma, non-mechanical mechanisms have recently been discussed as contributing to the pathogenesis of VILI. One such mechanism is oscillations in partial pressure of oxygen (PO2) which originate in lung tissue in the presence of within-breath recruitment and derecruitment of alveoli. The purpose of this study was to investigate this mechanism's possible independent effects on lung tissue and inflammation in a porcine model. METHODS: To separately study the impact of PO2 oscillations on the lungs, an in vivo model was set up that allowed for generating mixed-venous PO2 oscillations by the use of veno-venous extracorporeal membrane oxygenation (vvECMO) in a state of minimal mechanical stress. While applying the identical minimal-invasive ventilator settings, 16 healthy female piglets (weight 50 ± 4 kg) were either exposed for 6 h to a constant mixed-venous hemoglobin saturation (SmvO2) of 65% (which equals a PmvO2 of 41 Torr) (control group), or an oscillating SmvO2 (intervention group) of 40-90% (which equals PmvO2 oscillations of 30-68 Torr)-while systemic normoxia in both groups was maintained. The primary endpoint of histologic lung damage was assessed by ex vivo histologic lung injury scoring (LIS), the secondary endpoint of pulmonary inflammation by qRT-PCR of lung tissue. Cytokine concentration of plasma was carried out by ELISA. A bioinformatic microarray analysis of lung samples was performed to generate hypotheses about underlying pathomechanisms. RESULTS: The LIS showed significantly more severe damage of lung tissue after exposure to PO2 oscillations compared to controls (0.53 [0.51; 0.58] vs. 0.27 [0.23; 0.28]; P = 0.0025). Likewise, a higher expression of TNF-α (P = 0.0127), IL-1ß (P = 0.0013), IL-6 (P = 0.0007), and iNOS (P = 0.0013) in lung tissue was determined after exposure to PO2 oscillations. Cytokines in plasma showed a similar trend between the groups, however, without significant differences. Results of the microarray analysis suggest that inflammatory (IL-6) and oxidative stress (NO/ROS) signaling pathways are involved in the pathology linked to PO2 oscillations. CONCLUSIONS: Artificial mixed-venous PO2 oscillations induced lung damage and pulmonary inflammation in healthy animals during lung protective ventilation. These findings suggest that PO2 oscillations represent an independent mechanism of VILI.

Cost variation and savings opportunities in the Oncology Care Model.

OBJECTIVES: This study seeks to identify service categories that present the greatest opportunities to reduce spending in oncology care episodes, as defined by the CMS Oncology Care Model (OCM). Regional variation in spending for similar patients is often interpreted as evidence that resources can be saved, because higher-spending regions could achieve savings by behaving more like their lower-spending counterparts. STUDY DESIGN: We used Surveillance, Epidemiology, and End Results Medicare data from 2006-2013 for this retrospective observational cohort study. Analysis focused on patients with non-small cell lung cancer, advanced (stage III or IV) breast cancer, renal cell carcinoma, multiple myeloma, or chronic myeloid leukemia. METHODS: Episodes were identified for patients with the 5 included cancers, following the episode definition used in the OCM. We estimated standardized episode-level spending for a standard patient across subcategories of care for each hospital referral region (HRR) defined by the Dartmouth Atlas. The contribution of each subcategory to interregional variation in total spending reflects that subcategory's potential to yield savings. RESULTS: Chemotherapy and acute inpatient hospital care tended to be the highest contributors to interregional variation. Imaging, nonchemotherapy Part B drugs, physician evaluation and management services, and diagnostics were negligible contributors to interregional variation for all 5 cancers. CONCLUSIONS: Chemotherapy and inpatient hospital care offer the most potential to reduce spending within OCM-defined episodes. Other sources of savings differ by type of cancer. Assuming patient outcomes are not compromised, low-spending HRRs may be models for lowering cost in cancer care.

Share of Oncology Versus Nononcology Spending in Episodes Defined by the Centers for Medicare & Medicaid Services Oncology Care Model.

PURPOSE: Performance-based payments to oncology providers participating in the Centers for Medicare & Medicaid Services (CMS) Oncology Care Model (OCM) are based, in part, on overall spending in 6-month episodes of care, including spending unrelated to oncology care. The amount of spending likely to occur outside of oncologists' purview is unknown. METHODS: Following the OCM definition of an episode, we used SEER-Medicare data from 2006 to 2013 to identify episodes of cancer care for the following diagnoses: breast cancer (BC), non-small-cell lung cancer, renal cell carcinoma, multiple myeloma (MM), and chronic myeloid leukemia. Claims were categorized by service type and, separately, whether the content fell within the purview of oncology providers (classified as oncology, with all other claims nononcology). We calculated the shares of episode spending attributable to oncology versus nononcology services. RESULTS: The percentage of oncology spending within OCM episodes ranged from 62.4% in BC to 85.5% in MM. The largest source of oncology spending was antineoplastic drug therapy, ranging from 21.8% of total episode spending in BC to 67.6% in chronic myeloid leukemia. The largest source of nononcology spending was acute hospitalization and inpatient physician costs, ranging from 6.6% of overall spending for MM to 10.4% for non-small-cell lung cancer; inpatient oncology spending contributed roughly similar shares to overall spending. CONCLUSION: Most spending in OCM-defined episodes was attributable to services related to cancer care, especially antineoplastic drug therapy. Inability to control nononcology spending may present challenges for practices participating in the OCM, however.

Modeling the impacts of restrictive formularies on patients with HIV.

OBJECTIVES: To model the impacts of restrictive formulary designs on outcomes for patients with HIV and to demonstrate the costs of restricting access to novel HIV regimens with better safety and efficacy profiles. STUDY DESIGN: We modified an epidemiological model of HIV incidence, progression, and treatment to simulate the effects of 5 formulary scenarios on patient outcomes in the United States. METHODS: Using a cohort of HIV-susceptible individuals, we followed patients through HIV infection, disease progression, and death. Patients transitioned in and out of treatment states once infected. Treatment discontinuation, efficacy, and the rate of adverse events (AEs; renal failure and bone fracture) in each formulary scenario depended on the treatment path and regimens included. Outcomes of interest included all-cause cumulative deaths, annual rates of AEs, and costs associated with treating those AEs. RESULTS: All outcomes of interest were more favorable in less restrictive formulary scenarios that provided fewer barriers to appropriate treatments. By 2025, more restrictive formularies would have resulted in 171,500 more cumulative bone and renal events among treated patients with HIV compared with an open formulary. This corresponds to AE treatment costs of $3.65 billion in more restrictive formularies compared with $1.43 billion in an open formulary. Finally, compared with an open formulary, there would be an additional 16,200 cumulative deaths in more restrictive formularies. CONCLUSIONS: Less restrictive formulary designs, which allow patients with HIV to initiate potentially safer and more efficacious regimens based on their proclivity to AEs, yield better outcomes and reduce costs.

Greater Spending Associated with Improved Survival for Some Cancers in OCM-Defined Episodes.

BACKGROUND: Previous research finds significant variation in spending and utilization across regions, with little evidence of differences in outcomes. While such findings have been interpreted as evidence that spending can be reduced without compromising patient outcomes, the link between spending variation and outcomes remains a critical question. OBJECTIVE: To use evidence from geographic variations in spending and an individual-level survival analysis to test whether spending within oncology care episodes is associated with survival, where episodes are defined as in the Center for Medicare and Medicaid Innovation's Oncology Care Model (OCM). METHODS: In this retrospective cohort analysis, patient data from the Surveillance, Epidemiology and End Results Medicare (SEER-Medicare) database for 2007-2013 were linked to hospital referral regions (HRRs) using ZIP codes. Patients in the SEER program are a part of selected population-based cancer registries throughout the United States whose records are linked to Medicare enrollment and claims data (93% of elderly registry patients were successfully linked to Medicare data). Episodes of cancer care were defined as in the OCM: 6 months following a triggering chemotherapy claim. We analyzed episodes of care for 5 tumor types: advanced breast cancer (BC), non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), multiple myeloma (MM), and chronic myeloid leukemia (CML). We removed the effects of differentials in Medicare payment rates, which were mostly geographic. Regression analysis was then used to calculate standardized spending levels for each HRR, that is, spending adjusted for differences in patient and episode characteristics. To examine the effect of spending during OCM-defined episodes on individual-level survival, we used Cox regression with patient characteristics and standardized HRR spending per episode as covariates. To address concerns that may arise from multiple comparisons across the 5 tumor types, we used the Benjamini-Hochberg procedure to control the false discovery rate. RESULTS: Our analysis showed significant differences in standardized spending across HRRs. Compared with spending at the 20th percentile episode, spending at the 80th percentile ranged from 25% higher ($57,392 vs. $45,995 for MM) to 47% higher ($36,920 vs. $24,127 for RCC), indicating practice style variation across regions. The hazard of dying for patients with NSCLC and MM statistically significantly decreased by 7% (HR = 0.93, P = 0.006) and 13% (HR = 0.87, P = 0.019), respectively, for a $10,000 increase in standardized spending (in 2013 U.S. dollars). For the 3 other cancers, spending effects were not statistically significant. After using the Benjamini-Hochberg procedure with a 5% false discovery rate, the effects of increased spending on improved survival for NSCLC and MM remained statistically significant. CONCLUSIONS: The association we found between spending and survival suggests caution may be warranted for physicians, pharmacists, other health care professionals, and policymakers involved in efforts to reduce across-the-board spending within OCM-defined episodes for at least 2 of the 5 cancers studied. DISCLOSURES: Funding for this research was provided by Novartis Pharmaceuticals to Precision Health Economics in support of research design, analysis, and technical writing services. The funder provided input on study design and comments on the draft report. Baumgardner, Shahabi, and Linthicum are employees of Precision Health Economics (PHE), a health care consultancy to the insurance and life science industries, including firms that market oncology therapies. Vine was an employee of PHE at the time of this research. Zacker is an employee of and shareholder in Novartis Pharmaceuticals. Lakdawalla is a consultant to PHE and holds equity in its parent company, Precision Medicine Group.

Detection of inspiratory recruitment of atelectasis by automated lung sound analysis as compared to four-dimensional computed tomography in a porcine lung injury model.

BACKGROUND: Cyclic recruitment and de-recruitment of atelectasis (c-R/D) is a contributor to ventilator-induced lung injury (VILI). Bedside detection of this dynamic process could improve ventilator management. This study investigated the potential of automated lung sound analysis to detect c-R/D as compared to four-dimensional computed tomography (4DCT). METHODS: In ten piglets (25 ± 2 kg), acoustic measurements from 34 thoracic piezoelectric sensors (Meditron ASA, Norway) were performed, time synchronized to 4DCT scans, at positive end-expiratory pressures of 0, 5, 10, and 15 cmH2O during mechanical ventilation, before and after induction of c-R/D by surfactant washout. 4DCT was post-processed for within-breath variation in atelectatic volume (Δ atelectasis) as a measure of c-R/D. Sound waveforms were evaluated for: 1) dynamic crackle energy (dCE): filtered crackle sounds (600-700 Hz); 2) fast Fourier transform area (FFT area): spectral content above 500 Hz in frequency and above -70 dB in amplitude in proportion to the total amount of sound above -70 dB amplitude; and 3) dynamic spectral coherence (dSC): variation in acoustical homogeneity over time. Parameters were analyzed for global, nondependent, central, and dependent lung areas. RESULTS: In healthy lungs, negligible values of Δ atelectasis, dCE, and FFT area occurred. In lavage lung injury, the novel dCE parameter showed the best correlation to Δ atelectasis in dependent lung areas (R2 = 0.88) where c-R/D took place. dCE was superior to FFT area analysis for each lung region examined. The analysis of dSC could predict the lung regions where c-R/D originated. CONCLUSIONS: c-R/D is associated with the occurrence of fine crackle sounds as demonstrated by dCE analysis. Standardized computer-assisted analysis of dCE and dSC seems to be a promising method for depicting c-R/D.

Effect of Bronchoconstriction-induced Ventilation-Perfusion Mismatch on Uptake and Elimination of Isoflurane and Desflurane.

BACKGROUND: Increasing numbers of patients with obstructive lung diseases need anesthesia for surgery. These conditions are associated with pulmonary ventilation/perfusion (VA/Q) mismatch affecting kinetics of volatile anesthetics. Pure shunt might delay uptake of less soluble anesthetic agents but other forms of VA/Q scatter have not yet been examined. Volatile anesthetics with higher blood solubility would be less affected by VA/Q mismatch. We therefore compared uptake and elimination of higher soluble isoflurane and less soluble desflurane in a piglet model. METHODS: Juvenile piglets (26.7 ± 1.5 kg) received either isoflurane (n = 7) or desflurane (n = 7). Arterial and mixed venous blood samples were obtained during wash-in and wash-out of volatile anesthetics before and during bronchoconstriction by methacholine inhalation (100 µg/ml). Total uptake and elimination were calculated based on partial pressure measurements by micropore membrane inlet mass spectrometry and literature-derived partition coefficients and assumed end-expired to arterial gradients to be negligible. VA/Q distribution was assessed by the multiple inert gas elimination technique. RESULTS: Before methacholine inhalation, isoflurane arterial partial pressures reached 90% of final plateau within 16 min and decreased to 10% after 28 min. By methacholine nebulization, arterial uptake and elimination delayed to 35 and 44 min. Desflurane needed 4 min during wash-in and 6 min during wash-out, but with bronchoconstriction 90% of both uptake and elimination was reached within 15 min. CONCLUSIONS: Inhaled methacholine induced bronchoconstriction and inhomogeneous VA/Q distribution. Solubility of inhalational anesthetics significantly influenced pharmacokinetics: higher soluble isoflurane is less affected than fairly insoluble desflurane, indicating different uptake and elimination during bronchoconstriction.

Implementation of a Tele-urology Program for Outpatient Hematuria Referrals: Initial Results and Patient Satisfaction.

OBJECTIVE: To report on results from a new tele-urology pathway for managing hematuria consults, including a survey of patient attitudes and satisfaction with such a program. Recent guideline changes have relaxed the definition of microscopic hematuria and may have significantly increased the number of hematuria evaluations. MATERIALS AND METHODS: Patients referred to the Atlanta Veterans Administration Medical Center with hematuria were scheduled for a tele-urology clinic encounter utilizing a telephone call to obtain hematuria-related clinical information via a standardized algorithm. At subsequent cystoscopy, patients were evaluated with a 29-question survey regarding overall acceptance and satisfaction of the clinic (8 questions) and impact factors (21 questions). RESULTS: One hundred fifty veterans participated in the survey. Median time from consult request to appointment was 12 days and thereafter to cystoscopy was 16 days. Patients reported high acceptance and overall satisfaction with telephone evaluation; mean scores exceeded 9 out of 10 for overall satisfaction, efficiency, convenience, friendliness, care quality, understandability, privacy, and professionalism. When presented with a choice, nearly all patients (98%) preferred telephone-based encounters to face-to-face clinic visits. Underlying negative factors responsible for patients' preferences included transportation-related issues (97%) and logistical clinic issues (65%). Ninety-seven percent of patients reported high-quality evaluation. CONCLUSION: Patients report high acceptance and satisfaction with telephone clinics as a mechanism for expedited hematuria evaluation, primarily due to avoiding barriers related to transportation and clinical operations, as well as a perceived high quality of evaluation. Telephone appointments have potential to positively impact healthcare access and productivity.

Bronchoconstriction induced by inhaled methacholine delays desflurane uptake and elimination in a piglet model.

Bronchoconstriction is a hallmark of asthma and impairs gas exchange. We hypothesized that pharmacokinetics of volatile anesthetics would be affected by bronchoconstriction. Ventilation/perfusion (VA/Q) ratios and pharmacokinetics of desflurane in both healthy state and during inhalational administration of methacholine (MCh) to double peak airway pressure were studied in a piglet model. In piglets, MCh administration by inhalation (100 µg/ml, n=6) increased respiratory resistance, impaired VA/Q distribution, increased shunt, and decreased paO2 in all animals. The uptake and elimination of desflurane in arterial blood was delayed by nebulization of MCh, as determined by Micropore Membrane Inlet Mass Spectrometry (wash-in time to P50, healthy vs. inhalation: 0.5 min vs. 1.1 min, to P90: 4.0 min vs. 14.8 min). Volatile elimination was accordingly delayed. Inhaled methacholine induced severe bronchoconstriction and marked inhomogeneous VA/Q distribution in pigs, which is similar to findings in human asthma exacerbation. Furthermore, MCh-induced bronchoconstriction delayed both uptake and elimination of desflurane. These findings might be considered when administering inhalational anesthesia to asthmatic patients.

Ventilation/perfusion distributions revisited.

PURPOSE OF REVIEW: A major cause of hypoxemia in anesthesia is ventilation-perfusion (VA/Q) mismatch. With more advanced surgery and an aging population, monitoring of VA/Q is of increasing importance. RECENT FINDINGS: The classic multiple inert gas elimination technique has been simplified with a new approach based on mass spectrometry. VA/Q distributions can also be measured, at the bedside, by varying inspired oxygen concentration. MRI, 3-dimensional single photon emission computed tomography, positron emission tomography, and electrical impedance tomography enable imaging of perfusion and ventilation, and in some of the techniques also the distribution of inflammation. One-lung ventilation with thoracoscopy and capnothorax require careful monitoring of VA/Q, made possible bedside by electrical impedance tomography. Carbon dioxide, but not air, for pneumoperitoneum enhances shift of perfusion to ventilated regions. Ventilatory support during cardiopulmonary resuscitation causes less VA/Q mismatch when inspired oxygen concentrations are lower. Mechanisms of redistribution of lung blood flow by inhaled nitric oxide include endothelin-mediated vasoconstriction in collapsed lung regions. SUMMARY: Methods are continuously developing to simplify measurement of VA/Q and also to relate VA/Q to inflammation. The recording of VA/Q has helped to explain important aspects of gas exchange in thoracic anesthesiology and in intensive care medicine.