RESUMO
INTRODUCTION: Oncologic esophagectomy is a two-cavity procedure with considerable morbidity and mortality. Complex anatomy and the proximity to major vessels constitute a risk for massive intraoperative hemorrhage. Currently, there is no conclusive consensus on the ideal anesthesiologic countermeasure in case of such immense blood loss. The objective of this work was to identify the most promising anesthesiologic management in case of intraoperative hemorrhage with regards to tissue perfusion of the gastric conduit during esophagectomy using hyperspectral imaging (HSI). MATERIAL AND METHODS: An established live porcine model (n=32) for esophagectomy was used with gastric conduit formation and simulation of a linear stapled side-to-side esophagogastrostomy. After a standardized procedure of controlled blood loss of about 1 L per pig, the four experimental groups (n=8 each) differed in anesthesiologic intervention i.e. (I) permissive hypotension, (II) catecholamine therapy using noradrenaline, (III) crystalloid volume supplementation and (IV) combined crystalloid volume supplementation with noradrenaline therapy. HSI tissue oxygenation (StO2) of the gastric conduit was evaluated and correlated with systemic perfusion parameters. Measurements were conducted before (T0) and after (T1) laparotomy, after hemorrhage (T2) and 60 minutes (T3) and 120 minutes (T4) after anesthesiologic intervention. RESULTS: StO2 values of the gastric conduit showed significantly different results between the four experimental groups with 63.3% (±7.6%) after permissive hypotension (I), 45.9% (±6.4%) after catecholamine therapy (II), 70.5% (±6.1%) after crystalloid volume supplementation (III) and 69.0% (±3.7%) after combined therapy (IV). StO2 values correlated strongly with systemic lactate values (r=-0.67; CI -0.77 to -0.54), which is an established prognostic factor. CONCLUSION: Crystalloid volume supplementation (III) yields the highest StO2 values and lowest systemic lactate values and therefore appears to be the superior primary treatment strategy after hemorrhage during esophagectomy with regards to microcirculatory tissue oxygenation of the gastric conduit.
RESUMO
This work investigates linear and non-linear parametric reduced order models (ROM) capable of replacing computationally expensive high-fidelity simulations of human body models (HBM) through a non-intrusive approach. Conventional crash simulation methods pose a computational barrier that restricts profound analyses such as uncertainty quantification, sensitivity analysis, or optimization studies. The non-intrusive framework couples dimensionality reduction techniques with machine learning-based surrogate models that yield a fast responding data-driven black-box model. A comparative study is made between linear and non-linear dimensionality reduction techniques. Both techniques report speed-ups of a few orders of magnitude with an accurate generalization of the design space. These accelerations make ROMs a valuable tool for engineers.
Assuntos
Corpo Humano , Aprendizado de Máquina , Humanos , IncertezaRESUMO
BACKGROUND: High dose N acetylcysteine (NAC), a mucolytic, anti-inflammatory and antioxidant agent has been shown to significantly reduce exacerbations, and improve quality of life in placebo controlled, double blind randomised (RCT) studies in patients with COPD, and in an open, randomised study in bronchiectasis. In this pilot, randomised, double-blind, placebo-controlled study, we wished to investigate the feasibility of a larger clinical trial, and the anti-inflammatory and clinical benefits of high dose NAC in bronchiectasis. AIMS: Primary outcome: to assess the efficacy of NAC 2400 mg/day at 6 weeks on sputum neutrophil elastase (NE), a surrogate marker for exacerbations. Secondary aims included assessing the efficacy of NAC on sputum MUC5B, IL-8, lung function, quality of life, and adverse effects. METHODS: Participants were randomised to receive 2400 mg or placebo for 6 weeks. They underwent 3 visits: at baseline, week 3 and week 6 where clinical and sputum measurements were assessed. RESULTS: The study was stopped early due to the COVID pandemic. In total 24/30 patients were recruited, of which 17 completed all aspects of the study. Given this, a per protocol analysis was undertaken: NAC (n = 9) vs placebo (n = 8): mean age 72 vs 62 years; male gender: 44% vs 50%; baseline median FEV11.56 L (mean 71.5 % predicted) vs 2.29L (mean 82.2% predicted). At 6 weeks, sputum NE fell by 47% in the NAC group relative to placebo (mean fold difference (95%CI: 0.53 (0.12,2.42); MUC5B increased by 48% with NAC compared with placebo. Lung function, FVC improved significantly with NAC compared with placebo at 6 weeks (mean fold difference (95%CI): 1.10 (1.00, 1.20), p = 0.045. Bronchiectasis Quality of life measures within the respiratory and social functioning domains demonstrated clinically meaningful improvements, with social functioning reaching statistical significance. Adverse effects were similar in both groups. CONCLUSION: High dose NAC exhibits anti-inflammatory benefits, and improvements in aspects of quality of life and lung function measures. It is safe and well tolerated. Further larger placebo controlled RCT's are now warranted examining its role in reducing exacerbations.
Assuntos
Acetilcisteína , Bronquiectasia , Adulto , Humanos , Masculino , Idoso , Acetilcisteína/efeitos adversos , Qualidade de Vida , Projetos Piloto , Bronquiectasia/tratamento farmacológico , Inflamação/tratamento farmacológico , Anti-Inflamatórios/efeitos adversos , Método Duplo-CegoRESUMO
The UK National External Quality Assessment Service (NEQAS) provide an external proficiency testing (EPT) service for clinical laboratories. UK NEQAS for Histocompatibility and Immunogenetics (H&I) has been providing EPT schemes for over 45 years and has grown during this time to provide 19 EPT schemes. Accurate human leucocyte antigen (HLA) typing is critical to support safe clinical services, including transplantation, therefore high quality, relevant EPT schemes are required as part of a laboratory's quality assurance. This article reviews the development of the HLA typing EPT schemes, from the first HLA phenotyping scheme in 1975, via the first HLA genotyping scheme in 1992, through to the introduction in 2017 of HLA third field assessment results from next-generation sequencing technology. In addition, the introduction of EPT schemes to cover HLA associated diseases and pharmacogenetic reactions, including HLA-B27, HLA*B*57:01 and HLA-DQ for coeliac disease are discussed. The accuracy of laboratory EPT results for HLA phenotyping are >96% (2018-2022), HLA genotyping >99% (2020-2022), HLA-B27 testing >99% (2018-2022) and B*57:01 testing >99% (2017-2022). However, for HLA genotyping for coeliac disease 22%-46% of laboratories made errors in 2020-2022. On investigation, the high rate of unsatisfactory performance was attributed to laboratories lacking specific knowledge to interpret HLA genotyping results and accurately report HLA types for coeliac disease. A misleading commercial kit insert was also identified. The assessment of scheme results has uncovered several issues which have been addressed with the intention of educating participants and improving clinical services. The UK NEQAS for H&I EPT schemes have evolved over the past four decades to reflect changes in HLA typing technology, laboratory clinical practice and to cover post-analytical interpretative elements of HLA typing.
RESUMO
BACKGROUND: Successful implementation of digital health systems requires contextually sensitive solutions. Working directly with system users and drawing on implementation science frameworks are both recommended. We sought to combine Normalisation Process Theory (NPT) with participatory co-design methods, to work with healthcare stakeholders to generate implementation support recommendations for a new electronic patient reported outcome measure (ePRO) in renal services. ePROs collect data on patient-reported symptom burden and illness experience overtime, requiring sustained engagement and integration into existing systems. METHODS: We identified co-design methods that could be mapped to NPT constructs to generate relevant qualitative data. Patients and staff from three renal units in England participated in empathy and process mapping activities to understand 'coherence' (why the ePRO should be completed) and 'cognitive participation' (who would be involved in collecting the ePRO). Observation of routine unit activity was completed to understand 'collective action' (how the collection of ePRO could integrate with service routines). RESULTS: The mapping activities and observation enabled the research team to become more aware of the key needs of both staff and patients. Working within sites enabled us to consider local resources and barriers. This produced 'core and custom' recommendations specifying core needs that could be met with customised local solutions. We identified two over-arching themes which need to be considered when introducing new digital systems (1) That data collection is physical (electronic systems need to fit into physical spaces and routines), and (2) That data collection is intentional (system users must be convinced of the value of collecting the data). CONCLUSIONS: We demonstrate that NPT constructs can be operationalised through participatory co-design to work with stakeholders and within settings to collaboratively produce implementation support recommendations. This enables production of contextually sensitive implementation recommendations, informed by qualitative evidence, theory, and stakeholder input. Further longitudinal evaluation is necessary to determine how successful the recommendations are in practice.
Assuntos
Eletrônica , Medidas de Resultados Relatados pelo Paciente , Inglaterra , Humanos , Pesquisa Qualitativa , Reino UnidoAssuntos
Emigração e Imigração , Tuberculose , Humanos , Austrália/epidemiologia , Incidência , Tuberculose/epidemiologia , OcupaçõesRESUMO
Incompatible living donor kidney transplantation (ILDKT) has been established as an effective option for end-stage renal disease patients with willing but HLA-incompatible living donors, reducing mortality and improving quality of life. Depending on antibody titer, ILDKT can require highly resource-intensive procedures, including intravenous immunoglobulin, plasma exchange, and/or cell-depleting antibody treatment, as well as protocol biopsies and donor-specific antibody testing. This study sought to compare the cost and Medicare reimbursement, exclusive of organ acquisition payment, for ILDKT (n = 926) with varying antibody titers to matched compatible transplants (n = 2762) performed between 2002 and 2011. Data were assembled from a national cohort study of ILDKT and a unique data set linking hospital cost accounting data and Medicare claims. ILDKT was more expensive than matched compatible transplantation, ranging from 20% higher adjusted costs for positive on Luminex assay but negative flow cytometric crossmatch, 26% higher for positive flow cytometric crossmatch but negative cytotoxic crossmatch, and 39% higher for positive cytotoxic crossmatch (p < 0.0001 for all). ILDKT was associated with longer median length of stay (12.9 vs. 7.8 days), higher Medicare payments ($91 330 vs. $63 782 p < 0.0001), and greater outlier payments. In conclusion, ILDKT increases the cost of and payments for kidney transplantation.
Assuntos
Incompatibilidade de Grupos Sanguíneos/economia , Rejeição de Enxerto/economia , Teste de Histocompatibilidade/economia , Falência Renal Crônica/cirurgia , Transplante de Rim/economia , Doadores Vivos , Complicações Pós-Operatórias/economia , Estudos de Casos e Controles , Feminino , Seguimentos , Taxa de Filtração Glomerular , Rejeição de Enxerto/epidemiologia , Sobrevivência de Enxerto , Humanos , Testes de Função Renal , Masculino , Pessoa de Meia-Idade , Prognóstico , Qualidade de Vida , Estudos Retrospectivos , Fatores de RiscoRESUMO
Organ shortage is the major limitation to kidney transplantation in the developed world. Conversely, millions of patients in the developing world with end-stage renal disease die because they cannot afford renal replacement therapy-even when willing living kidney donors exist. This juxtaposition between countries with funds but no available kidneys and those with available kidneys but no funds prompts us to propose an exchange program using each nation's unique assets. Our proposal leverages the cost savings achieved through earlier transplantation over dialysis to fund the cost of kidney exchange between developed-world patient-donor pairs with immunological barriers and developing-world patient-donor pairs with financial barriers. By making developed-world health care available to impoverished patients in the developing world, we replace unethical transplant tourism with global kidney exchange-a modality equally benefitting rich and poor. We report the 1-year experience of an initial Filipino pair, whose recipient was transplanted in the United states with an American donor's kidney at no cost to him. The Filipino donor donated to an American in the United States through a kidney exchange chain. Follow-up care and medications in the Philippines were supported by funds from the United States. We show that the logistical obstacles in this approach, although considerable, are surmountable.
Assuntos
Análise Custo-Benefício , Doação Dirigida de Tecido , Custos de Cuidados de Saúde/legislação & jurisprudência , Falência Renal Crônica/economia , Transplante de Rim/economia , Doadores Vivos/provisão & distribuição , Obtenção de Tecidos e Órgãos/economia , Países em Desenvolvimento , Taxa de Filtração Glomerular , Sobrevivência de Enxerto , Recursos em Saúde , Acessibilidade aos Serviços de Saúde , Humanos , Falência Renal Crônica/cirurgia , Testes de Função Renal , Transplante de Rim/legislação & jurisprudência , Transplante de Rim/métodos , Filipinas , Formulação de Políticas , Prognóstico , Fatores de Risco , Obtenção de Tecidos e Órgãos/métodos , Estados UnidosRESUMO
PURPOSE: Perioperative chemotherapy confers a 3-year progression free survival advantage following resection of colorectal liver metastases (CRLM), but is associated with significant toxicity. Chemoembolisation using drug eluting PVA microspheres loaded with irinotecan (DEBIRI) allows sustained delivery of drug directly to tumour, maximising response whilst minimising systemic exposure. This phase II single arm study examined the safety and feasibility of DEBIRI before resection of CRLM. METHODS: Patients with resectable CRLM received lobar DEBIRI 1 month prior to surgery, with a radiological endpoint of near stasis. The trial had a primary end-point of tumour resectability (R0 resection). Secondary end-points included safety, pathologic tumour response and overall survival. RESULTS: 40 patients received DEBIRI, with a median dose of 103 mg irinotecan (range 64-175 mg). Morbidity was low (2.5%, CTCAE grade 2) with no evidence of systemic chemotoxicity. All patients proceeded to surgery, with 38 undergoing resection (95%, R0 resection rate 74%). 30-day post-operative mortality was 5% (n = 2), with neither death TACE related. 66 lesions were resected, with histologic major or complete pathologic response seen in 77.3% of targeted lesions. At median follow up of 40.6 months, 12 patients (34.3%) had died of recurrent disease with a median overall survival of 50.9 months. Nominal 1, 3 and 5-year OS was 93, 78 & 49% respectively. CONCLUSIONS: Resection after neoadjuvant DEBIRI for CRLM is feasible and safe. Single treatment with DEBIRI resulted in tumour pathologic response and median overall survival comparable to that seen after systemic neoadjuvant chemotherapy. Registered at clinicaltrials.gov (NCT00844233).
Assuntos
Antineoplásicos Fitogênicos/administração & dosagem , Camptotecina/análogos & derivados , Quimioembolização Terapêutica/métodos , Neoplasias Colorretais/patologia , Hepatectomia , Neoplasias Hepáticas/terapia , Metastasectomia , Terapia Neoadjuvante , Camptotecina/administração & dosagem , Intervalo Livre de Doença , Feminino , Humanos , Irinotecano , Neoplasias Hepáticas/secundário , Masculino , Microesferas , Pessoa de Meia-Idade , Resultado do TratamentoAssuntos
Seleção do Doador , Doadores Vivos , Humanos , Transplante de Rim , Obtenção de Tecidos e ÓrgãosRESUMO
The following Consensus Statement is endorsed by The International Menopause Society, The North American Menopause Society, The Endocrine Society, The European Menopause and Andropause Society, The Asia Pacific Menopause Federation, The International Osteoporosis Foundation and The Federation of Latin American Menopause Societies.
Assuntos
Terapia de Reposição de Estrogênios , Pós-Menopausa , Feminino , Saúde Global , Humanos , Saúde da MulherRESUMO
We propose that some deceased donor (DD) kidneys be allocated to initiate nonsimultaneous extended altruistic donor chains of living donor (LD) kidney transplants to address, in part, the huge disparity between patients on the DD kidney waitlist and available donors. The use of DD kidneys for this purpose would benefit waitlisted candidates in that most patients enrolled in kidney paired donation (KPD) systems are also waitlisted for a DD kidney transplant, and receiving a kidney through the mechanism of KPD will decrease pressure on the DD pool. In addition, a LD kidney usually provides survival potential equal or superior to that of DD kidneys. If KPD chains that are initiated by a DD can end in a donation of an LD kidney to a candidate on the DD waitlist, the quality of the kidney allocated to a waitlisted patient is likely to be improved. We hypothesize that a pilot program would show a positive impact on patients of all ethnicities and blood types.
Assuntos
Seleção do Doador , Sobrevivência de Enxerto , Transplante de Rim , Doadores de Tecidos/provisão & distribuição , Obtenção de Tecidos e Órgãos/métodos , Incompatibilidade de Grupos Sanguíneos , Humanos , Listas de EsperaRESUMO
BACKGROUND: Liver resection before primary cancer resection is a novel strategy advocated for selected patients with synchronous colorectal liver metastases (sCRLM). This study measured outcomes in patients with sCRLM following a liver-first or classical approach, and used a validated propensity score. METHODS: Clinical, pathological and follow-up data were collected prospectively from consecutive patients undergoing hepatic resection for sCRLM at a single centre (2004-2014). Cumulative disease-free survival (DFS), cancer-specific survival (CSS) and overall survival (OS) were calculated by means of Kaplan-Meier analysis. Survival differences were analysed in the whole cohort and in subgroups matched according to Basingstoke Predictive Index (BPI). RESULTS: Of 582 patients, 98 had a liver-first and 467 a classical approach to treatment; 17 patients undergoing simultaneous bowel and liver resection were excluded. The median (i.q.r.) BPI was significantly higher in the liver-first compared with the classical group: 8·5 (5-10) versus 8 (4-9) (P = 0·030). Median follow-up was 34 months. The 5-year DFS rate was lower in the liver-first group than in the classical group (23 versus 45·6 per cent; P = 0·001), but there was no difference in 5-year CSS (51 versus 53·8 per cent; P = 0·379) or OS (44 versus 49·6 per cent; P = 0·305). After matching for preoperative BPI, there was no difference in 5-year DFS (37 versus 41·2 per cent for liver-first versus classical approach; P = 0·083), CSS (51 versus 53·2 per cent; P = 0·616) or OS (47 versus 49·1 per cent; P = 0·846) rates. CONCLUSION: Patients with sCRLM selected for a liver-first approach had more oncologically advanced disease and a poorer prognosis. They had inferior cumulative DFS than those undergoing a classical approach, a difference negated by matching preoperative BPI.
Assuntos
Neoplasias Colorretais/patologia , Hepatectomia/métodos , Neoplasias Hepáticas/secundário , Neoplasias Hepáticas/cirurgia , Adulto , Idoso , Colectomia , Neoplasias Colorretais/cirurgia , Bases de Dados Factuais , Feminino , Seguimentos , Humanos , Neoplasias Hepáticas/mortalidade , Masculino , Pessoa de Meia-Idade , Pontuação de Propensão , Análise de Sobrevida , Resultado do TratamentoRESUMO
BACKGROUND: Elderly patients experience a different spectrum of disease and poorer outcomes than younger patients. This study investigated the impact of age and medical comorbidities on the management and outcome of patients ≥65 years. METHODS: A retrospective review of all patients ≥65 years (481 patients with 525 primary melanomas) presenting with AJCC clinical stage I-II melanoma to an Australian cancer centre between 2000 and 2008. RESULT: The median age was 74 years (65-94) with a male predominance (313 males, 65.0%) and median tumour thickness of 1.90 mm (IQR = 0.40-2.90, T1 = 33%, T2 = 20%, T3 = 24%, T4 = 23%). Inadequate surgical margins of excision (<10 mm) were common in older patients independent of site, thickness and ulceration (OR = 1.04, 95%CI = 1.00-1.07, p = 0.038). Inadequate excision margins were strongly associated with time to local recurrence, independent of age, thickness, ulceration and mitotic rate (HR = 3.00, 95%CI = 1.49-6.03, p = 0.0021), but not time to progression (p = 0.10) or disease specific survival (DSS, p = 0.27). Overall survival (OS) was strongly related to increasing age (HR = 1.04, 95%CI = 1.01-1.07, p = 0.015) and comorbid medical conditions (HR = 1.26, 95%CI = 1.12-1.42, p < 0.001), as assessed by the Charlson comorbidity index (CCI). DSS was significantly related to CCI (HR = 1.20, 95%CI = 1.01-1.42, p = 0.041) and not age (p = 0.46), when adjusting for thickness, ulceration and mitotic rate on multivariate analysis. CONCLUSION: Older patients present with poor prognosis melanomas yet are less likely to receive adequate surgical excision margins resulting in higher rates of local recurrence. In melanoma patients ≥65 years, the increasing number of medical comorbidities explains much of the age related variations in OS and DSS and should be considered when planning treatment.
Assuntos
Neoplasias de Cabeça e Pescoço/mortalidade , Melanoma/mortalidade , Recidiva Local de Neoplasia/epidemiologia , Neoplasias Cutâneas/mortalidade , Úlcera Cutânea/epidemiologia , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Austrália/epidemiologia , Biópsia , Carcinoma Basocelular/epidemiologia , Carcinoma de Células Escamosas/epidemiologia , Comorbidade , Feminino , Neoplasias de Cabeça e Pescoço/epidemiologia , Neoplasias de Cabeça e Pescoço/patologia , Humanos , Linfonodos/patologia , Masculino , Margens de Excisão , Melanoma/epidemiologia , Melanoma/patologia , Índice Mitótico , Prognóstico , Modelos de Riscos Proporcionais , Estudos Retrospectivos , Linfonodo Sentinela/patologia , Biópsia de Linfonodo Sentinela/estatística & dados numéricos , Neoplasias Cutâneas/epidemiologia , Neoplasias Cutâneas/patologia , Taxa de Sobrevida , Carga TumoralRESUMO
A kidney-paired donation (KPD) pool consists of transplant candidates and their incompatible donors, along with nondirected donors (NDDs). In a match run, exchanges are arranged among pairs in the pool via cycles, as well as chains created from NDDs. A problem of importance is how to arrange cycles and chains to optimize the number of transplants. We outline and examine, through example and by simulation, four schemes for selecting potential matches in a realistic model of a KPD system; proposed schemes take account of probabilities that chosen transplants may not be completed as well as allowing for contingency plans when the optimal solution fails. Using data on candidate/donor pairs and NDDs from the Alliance for Paired Donation, the simulations extend over 8 match runs, with 30 pairs and 1 NDD added between each run. Schemes that incorporate uncertainties and fallbacks into the selection process yield substantially more transplants on average, increasing the number of transplants by as much as 40% compared to a standard selection scheme. The gain depends on the degree of uncertainty in the system. The proposed approaches can be easily implemented and provide substantial advantages over current KPD matching algorithms.
Assuntos
Algoritmos , Técnicas de Apoio para a Decisão , Seleção do Doador/métodos , Transplante de Rim , Doadores Vivos , Incerteza , Simulação por Computador , Seleção do Doador/organização & administração , Humanos , Modelos EstatísticosRESUMO
Failure to convert computer-identified possible kidney paired donation (KPD) exchanges into transplants has prohibited KPD from reaching its full potential. This study analyzes the progress of exchanges in moving from "offers" to completed transplants. Offers were divided into individual segments called 1-way transplants in order to calculate success rates. From 2007 to 2014, the Alliance for Paired Donation performed 243 transplants, 31 in collaboration with other KPD registries and 194 independently. Sixty-one of 194 independent transplants (31.4%) occurred via cycles, while the remaining 133 (68.6%) resulted from nonsimultaneous extended altruistic donor (NEAD) chains. Thirteen of 35 (37.1%) NEAD chains with at least three NEAD segments accounted for 68% of chain transplants (8.6 tx/chain). The "offer" and 1-way success rates were 21.9 and 15.5%, respectively. Three reasons for failure were found that could be prospectively prevented by changes in protocol or software: positive laboratory crossmatch (28%), transplant center declined donor (17%) and pair transplanted outside APD (14%). Performing a root cause analysis on failures in moving from offer to transplant has allowed the APD to improve protocols and software. These changes have improved the success rate and the number of transplants performed per year.
Assuntos
Internet , Transplante de Rim , Obtenção de Tecidos e Órgãos/métodos , Algoritmos , Técnicas de Apoio para a Decisão , Seleção do Doador/métodos , Seleção do Doador/organização & administração , Seleção do Doador/tendências , Humanos , Doadores Vivos , Modelos Estatísticos , Obtenção de Tecidos e Órgãos/organização & administração , Obtenção de Tecidos e Órgãos/tendências , Estados UnidosRESUMO
This study assessed whether the abundance of girellids and kyphosids was related to cover of the palatable green algae, Ulva australis and Ulva compressa, on rocky intertidal reefs in Jervis Bay, New South Wales, Australia. No relationship was found between Ulva spp. cover and abundance of Girella tricuspidata, Girella elevata and Kyphosus sydneyanus during a period of relatively low Ulva spp. cover (i.e. February 2011 to March 2011), but during a period of significantly higher Ulva spp. cover (i.e. October 2011 to November 2011) there was a strong correlation between Ulva spp. cover and G. tricuspidata abundance. Spatial analysis indicated that the abundance of G. tricuspidata was consistent across time, suggesting G. tricuspidata were not moving between reefs in response to variation in Ulva spp. cover between periods but rather that large schools of G. tricuspidata resided on reefs that had relatively higher Ulva spp. cover at certain times of the year.