Abstract

Introduction

The waiting time for day-surgeries is a relevant issue in the access to health care. It is considered to be excessive (longer than 12 weeks or 90 days) in several countries that are members of the Organization for Economic Co-operation and Development (OECD)¹1. OECD. Towards High Performing Health Systems: the OECD Health Project (versão eletrônica); 2004. Disponível em www.oecd.org/dataoecd/ (Acessado em 10 de novembro de 2007).
www.oecd.org/dataoecd/... . As a consequence of economic, social and demographic changes, with the resulting implications for health care costs, increasing the efficiency and efficacy of health services became relevant to enable their greater profitability²2. Hurst J, Siciliani L. Explaining waiting times variations for eletive surgery across OECD countries . OECD Health Working Papers; 2003. Disponivel em www.oecd.org/dataoecd/ (Acessado em 10 de novembro de 2007).
www.oecd.org/dataoecd/...

3. Barkun,Barkun JS. Waiting lists for surgery. Can J Surg 2002; 45(5). (versão eletrônica). Disponível em www.ncbi.nlm.nih.gov/pubmed/ (Acessado em 30 de novembro de 2007).
www.ncbi.nlm.nih.gov/pubmed/... ^{- 4}4. Waddell JP, MD. Wait times and health care resources. Can J Surg 2003; 47(6). (versão eletrônica). Disponível em www.ncbi.nlm.nih.gov/pubmed/ (Acessado em 27 de novembro de 2007).
www.ncbi.nlm.nih.gov/pubmed/... . The development of day-surgeries in outpatient clinics is one of the strategies that has been found to be efficient in the reduction of surgical waiting time. In general, countries with shorter day-surgery waiting times are also those with higher percentages of day-surgery procedures in outpatient clinics⁵5. Oudhoff JP, Timmermans DRM, Knol DL, Bijnen AB, Wal G. ( 2007) Waiting for eletive general surgery: impact on health quality of life and psychosocial consequences , doi:10.1186/1471-2458-7-164 (versão electrónica). Disponível em www.pubmedcentral.nih.gov/ (Acessado em 27 de fevereiro de 2008).
www.pubmedcentral.nih.gov/...

6. Davis K, Schoen C, Schoenbaum SC et al. Mirror, mirror on the wall: an update on the quality of American health through the patient's lens (versão eletrônica). The Commonwealth Fund, 2006. Disponível em www.commonwealthfund.org/publications/ (Acessado em 03 de novembro de 2007).
www.commonwealthfund.org/publications/... ^{- 7}7. Willcox S, Seddon M, Dunn S et al, Measuring and reducing waiting times: A cross-national comparison of strategies. (versão electronica) Health Affairs 2007; 26 (4): 1078-1087. Disponível em www.commonwealthfund.org/usr_doc/. (Acessado em 3 de novembro de 2007).
www.commonwealthfund.org/usr_doc/.... . The present study aimed to describe the existing relationship between the percentage of outpatient surgeries performed and surgical waiting time of day-surgeries in hospitals that provide these procedures in the Serviço Nacional de Saúde (SNS – National Health Service), in Continental Portugal, in 2006.

The National Health Service in Portugal

The Portuguese health system has been based on the SNS since 1979 and it is characterized as a public insurance with universal coverage, equality, reduced costs for users receiving services, and funding from regulatory taxes and rates⁸8. Biscaia AR, Ferrinho P et al. Cuidados de Saúde Primários em Portugal – Reformar para Novos Sucessos . Lisboa: Padrões Culturais Editora; 2006

9. Campos CD, Simões J. O Percurso da Saúde: Portugal na Europa . Lisboa: Almedina; 2011. ^{- 10}10. Simões J. Retrato Politico da Saúde – Dependência do Percurso e Inovação em Saúde: da Ideologia ao Desempenho . Lisboa: Almedina; 2009.. The SNS is complemented by private and voluntary health insurances and by several health sub-systems, usually associated with professional activities. Private health care providers play a role that complements the SNS, rather than representing a comprehensive alternative. Health units can be divided into three types: hospitals, which provide health care services such as surgeries and consultations of several specialties; health centers, which provide consultations with general practitioners and some specialties and nursing care; and, lastly, health units, which only provide consultations with general practitioners and some nursing care services¹⁰10. Simões J. Retrato Politico da Saúde – Dependência do Percurso e Inovação em Saúde: da Ideologia ao Desempenho . Lisboa: Almedina; 2009. ^{, 12}12. OPSS. Relatório de Primavera 2008 . Observatório Português de Sistemas de Saúde; 2006..

Portugal has adopted a gate-keeping system, according to which patients have to seek a general practitioner for an initial evaluation and, if necessary, they are referred to a specialist¹³13. Santos R. Tipos de Hospitais 1989 . Disponível em http://portalcodgdh.minsaude.pt/index. php (Acessado em 2009 e 2012).
http://portalcodgdh.minsaude.pt/index.... . Aiming to improve financial sustainability and to provide greater functional and organizational autonomy to hospitals, a new legal regime of management of hospitals covered by the SNS was approved in 2002.

Outpatient surgeries and waiting times

In 2008, Portugal ranked 26^thin a classification of health care systems conducted in 31 European countries and promoted in Brussels by the Health Consumer Powerhouse organization, which emphasizes the insufficient access to treatment and long waiting time^15,16. On an international level, throughout the last decade, several programs were developed with the objective of reducing day-surgery waiting time¹⁷17. Zalmanov M. As US outpatient surgery rates soar, ambulatory surgical centers shown to be safer than doctor's offices or hospitals for same–day procedures . Disponível em www.prweb.com/releases/2007/09. (Acessado em 5 de novembro de 2007).
www.prweb.com/releases/2007/09.... ^{, 18}18. Westert GP. Geographical variations in surgery: outpatients versus inpatient treatment. (versão electronica). Revue Medicale de l'Assurance Maladie 2002; 33(1). Disponível em www.ameli.fr/fileadmin/ (Acessado em 22 de outubro de 2007).
www.ameli.fr/fileadmin/... . In Portugal, these programs were initially directed towards the increase in surgical production¹¹11. OPSS. Relatório de Primavera 2006 – Um ano de governação em Saúde . Observatório Português de Sistemas de Saúde; 2006. ^{, 12}12. OPSS. Relatório de Primavera 2008 . Observatório Português de Sistemas de Saúde; 2006., making available additional funding for this purpose. These programs resulted in the partial reduction in surgical waiting lists and were somewhat efficient, although not achieving the expected results¹⁹19. Tribunal de Contas. Auditoria ao acesso aos cuidados de saúde do SNS . 2007. Disponível em www.tcontas.pt. (Acessado em 5 de novembro de 2007).
www.tcontas.pt....

20. Francisco AP. Avaliação de Desempenho – Hospitais SA . DGS; 2005. ^{- 21}21. Lemos P. Indicações e Vantagens da Cirurgia de Ambulatório. Revista da SPA 1998; 9: 104-13. The concept of maximum clinically acceptable waiting time was then introduced, when a maximum waiting time was defined as an indicator of performance and efficiency of health services, according to the clinical status and pathology involved^22,23. One of the strategies internationally implemented to reduce day-surgery waiting time includes the promotion of outpatient surgeries⁵5. Oudhoff JP, Timmermans DRM, Knol DL, Bijnen AB, Wal G. ( 2007) Waiting for eletive general surgery: impact on health quality of life and psychosocial consequences , doi:10.1186/1471-2458-7-164 (versão electrónica). Disponível em www.pubmedcentral.nih.gov/ (Acessado em 27 de fevereiro de 2008).
www.pubmedcentral.nih.gov/...

6. Davis K, Schoen C, Schoenbaum SC et al. Mirror, mirror on the wall: an update on the quality of American health through the patient's lens (versão eletrônica). The Commonwealth Fund, 2006. Disponível em www.commonwealthfund.org/publications/ (Acessado em 03 de novembro de 2007).
www.commonwealthfund.org/publications/... ^{- 7}7. Willcox S, Seddon M, Dunn S et al, Measuring and reducing waiting times: A cross-national comparison of strategies. (versão electronica) Health Affairs 2007; 26 (4): 1078-1087. Disponível em www.commonwealthfund.org/usr_doc/. (Acessado em 3 de novembro de 2007).
www.commonwealthfund.org/usr_doc/.... ^{, 24}24. Natário A et al. Cirurgia de Ambulatório: recomendações para o seu desenvolvimento . DGS, Direcção de Serviços e Planeamento; 2001 (versão eletrônica). Disponível em www.srsdocs. com/parcerias/publicacoes/ (Acessado em 29 de novembro de 2007).
www.srsdocs.... . The practice of outpatient surgeries in Portugal began in the 1990s, when certain hospital institutions developed organized programs under this surgical regime. In 1997, the percentage of outpatient surgical interventions remained at 8.9%²⁴24. Natário A et al. Cirurgia de Ambulatório: recomendações para o seu desenvolvimento . DGS, Direcção de Serviços e Planeamento; 2001 (versão eletrônica). Disponível em www.srsdocs. com/parcerias/publicacoes/ (Acessado em 29 de novembro de 2007).
www.srsdocs.... .

However, the interest in the development of such practice only increased in recent times. According to the National Outpatient Surgery Surveys conducted by the Associação Portuguesa de Cirurgia de Ambulatório (APCA – Portuguese Outpatient Surgery Association) in 71 Portuguese public hospitals, in 1999, 2001 and 2003, the percentage of outpatient surgeries in the total number of surgeries corresponded to 5.5%, in 1999, 7.2% in 2001, and nearly 14.6% in 2003²⁵25. Associação Portuguesa de Cirurgia de Ambulatório – APCA. I Inquérito Nacional de Cirurgia de Ambulatório ; 1999.

26. Associação Portuguesa de Cirurgia de Ambulatório – APCA. II Inquérito Nacional de Cirurgia de Ambulatório ; 2001. ^{- 27}27. Associação Portuguesa de Cirurgia de Ambulatório – APCA. III Inquérito Nacional de Cirurgia de Ambulatório ; 2003.. As a result of the effort made to increase the development of outpatient surgeries, there was an increase in their percentage between 2004 and 2006, reaching values of nearly 24% of all planned surgeries²⁸28. Direção Geral de Saúde. O desenvolvimento da Cirurgia de Ambulatório como objectivo etratégico do hospital. DGS; 2005.. A national survey conducted by the Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório (CNADCA – National Outpatient Surgery Development Committee)³¹31. Ministério da Saúde. Cirurgia de Ambulatório: um modelo de qualidade centrada no utente – Relatório Final. Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório. Outubro de 2008.in 61 SNS hospitals, in 2008, concluded that the main obstacles to the implementation of outpatient surgeries were the at the level of hospital management and organization (physical conditions of health establishments; top management engagement; human resources, especially anesthesiologists; insufficient infrastructure and organizational difficulties, mainly in the management of teams and units; experiences and acceptance of health professionals; and the difficulties in the post-operative follow-up period) and at the level of patients (population's lack of information about outpatient surgery characteristics, the social conditions of the Portuguese population and the difficulty in users' transportation between their place of residence and the hospital institution)³¹31. Ministério da Saúde. Cirurgia de Ambulatório: um modelo de qualidade centrada no utente – Relatório Final. Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório. Outubro de 2008.. Currently, after some years of implementation of both additional production programs and outpatient surgery development programs, there was a reduction in the mean waiting time for day surgeries from 6 to 8 months in 2005 and previous years, and from 2.5 to 3.5 months in 2010 (data refer to the first semester of 2010 published by the Health System Management Center). Additionally, there was an increase in the percentage of outpatient surgeries of approximately 50% (data refer to the entire country in 2010 published by the Health System Management Center)³⁰30. Indicadores do SNS – UGIC. I Semestre de 2010 . Disponível em www.acss.min-saude.pt (Acessado em 01 de março de 2012).
www.acss.min-saude.pt... .

The main objective was to study the existing associations between surgical waiting time (dependent variable) and the percentage of day surgeries (independent variable). In addition, the secondary objective was to investigate possible associations with other study variables that were potential determinants³⁴34. Murteira JF. Análise Exploratória de Dados – Estatística Descritiva. Lisboa: Editora McGraw-Hill; 1993. ^{, 35}35. Harrell Jr. FE. Regression Modeling Strategies. New York; Ed. Springer-Verlag; 2001..

Material, Population and Methods

Study design

An observational, ecological and analytical study was performed with health units³².

Population and sample

The study population included all SNS hospital units that provided surgical services in 2006. According to the Direção Geral da Saúde (DGS – General Health Management Office)³³33. DGS/DSIA/Divisão de Estatística; 2006. Centros de Saúde e Hospitais: Recursos e Produção do SNS-2005 . Disponível em www.dgsaude.pt (Acessado em 25 de março de 2008).
www.dgsaude.pt... , there were 85 hospitals in Continental Portugal in 2006. This study included 73 hospitals as some were excluded for not having surgical services (psychiatric hospitals, rehabilitation and physiotherapy centers etc.) or due to unavailable data.

Data source

Data were provided by the Administração Central de Serviços de Saúde (ACSS – Health Service Management Center), especially the Sistema de Informação de Acompanhamento e Contratualização (SIAC – Contract and Follow-up Information System) and the DGS Department of Statistics, including information about the hospital and hospital management types, performance indicators (occupancy rate, mean stay, discharged patients and discharged patients per bed, number of patients-day), population covered, human resources and existing installations. Data on waiting times and total, conventional and outpatient surgical production for each hospital were obtained from the Unidade Central de Gestão de Inscritos para Cirurgia (UGIC – Central Unit of Management of Patients Listed for Surgery) and mean values for all hospitals were subsequently calculated.

Statistical analysis

The relative numbers of surgeons and anesthesiologists were given according to specialty for each hospital and their sum was required to obtain the total numbers. Descriptive analysis was performed for numerical variables, with the calculation of the measures of central tendency (mean, mode and median), measures of non-central tendency (quartiles, deciles, percentiles and outlier observations), measures of dispersion (total variation and interquartile amplitude, standard deviation, variation and dispersion coefficients) and comparison of frequencies (ratios, proportions and percentages). Relative and absolute frequencies were used for the nominal and ordinal variables.

The inferential analysis was performed with Spearman's correlation analysis and multiple linear regression (backward stepwise, with a PIN <0.05 and POUT > 0.1)³⁵35. Harrell Jr. FE. Regression Modeling Strategies. New York; Ed. Springer-Verlag; 2001. ^{, 36}36. Henriques A, Neves C, Pesquita I. Estudos correlacionais e estudos causal-comparativos. Metodologia da Investigação I . DEFCUL; 2004. (versão electrónica). Disponível em www.educ.fc.ul.pt/docentes/ (Acessado em 27 de fevereiro de 2008).
www.educ.fc.ul.pt/docentes/... .

A total of 15 sample elements were eliminated in the construction of the linear regression model as they did not have data on some of the variables included in the model. Thus, the sample of the final model includes 58 hospital units. The analysis of the outliers enabled the identification of extreme cases considered to be influential for the models, which will be excluded in the construction of new regression functions. Observations in which the standardized residue had an absolute value higher than 1.96 for a significance level of 5% were considered as outliers. Additionally, observations that disrespected the conditions imposed on residues or that were not within the imposed limits for at least three of the remaining criteria considered were regarded as be extreme influential cases. The criteria established enabled the identification of ten outliers in the model, which were excluded from the analysis model, thus reducing the total number of cases from 58 to 48.

Description of variables

Dependent variables: The dependent variable in the present study is the day surgery waiting time (quantitative variable) in each of the health institutions studied. “Waiting time” is defined as the number of calendar days between the moment when a surgical intervention is indicated by a specialist and the moment when it is performed⁵⁵55. Regulamento do SIGIC. Portaria 45/2008 de 15 de janeiro.. A “surgical indication” is the therapeutic proposal in which a surgical intervention is expected to be performed with the resources of planned surgeries⁵⁵55. Regulamento do SIGIC. Portaria 45/2008 de 15 de janeiro.. The mean overall waiting time in days was used, regardless of this being associated with a conventional or outpatient surgery. The waiting time calculated from the sum of waiting times of patients listed for surgery, divided by the total number of patients listed and converted to days (multiplied by 30), was used to obtain this variable.

Independent variables: The independent variables are those that theoretically predict the dependent variables⁵². The percentage of outpatient surgical procedures performed in each hospital was the independent variable of this study. An “outpatient surgery” is understood as a planned surgical intervention carried out under general, loco-regional or local anesthesia, usually during hospitalization, which can be safely performed in adequate facilities, according to the existing lege artis , following admission and subsequent discharge within 24 hours and not including minor surgeries⁵⁵. The calculation of this percentage is based on the number of outpatient surgeries as a numerator and the number of outpatients surgeries added to the number of conventional surgeries as the denominator.

The “management type” dichotomous nominal variable was made functional in the following way: EPE management type and SA management type, as these were the most frequent existing management types.

• ·

  Number of surgeons existing per hospital;

• ·

  Number of anesthesiologists existing in each hospital;

• ·

  Total number of physicians existing in each hospital;

• ·

  Number of conventional ward and outpatient nurses, i.e. the number of nurses present in the conventional surgical ward or outpatient clinic or both, existing in each hospital;

• ·

  Number of operating rooms (conventional and outpatient surgeries), i.e. the number of operating areas aimed at outpatient and/or conventional surgeries;

• ·

  Number of hospitalization days, defined by the total number of days used by all hospitalized patients in several services of a hospital, except on their days of discharge in 365 days³³;

• ·

  Number of released patients, defined by the total number of patients who did not remain in the hospital, as they were discharged, deceased or transferred to another hospital, in 365 days, and those released per bed, i.e. the rate of patients discharged from hospitalization, and the total number of beds³³33. DGS/DSIA/Divisão de Estatística; 2006. Centros de Saúde e Hospitais: Recursos e Produção do SNS-2005 . Disponível em www.dgsaude.pt (Acessado em 25 de março de 2008).
  www.dgsaude.pt... ;

• ·

  Population covered by each hospital, i.e. the total population living in a certain geographic area served by a certain hospital;

• ·

  Hospital type, described as central, district or level 1 district hospital⁵⁶. In the perspective of the classification used in the present study¹³13. Santos R. Tipos de Hospitais 1989 . Disponível em http://portalcodgdh.minsaude.pt/index. php (Acessado em 2009 e 2012).
  http://portalcodgdh.minsaude.pt/index.... ^{, 14}14. Instituto Nacional de Estatística (INE), 2002. Disponível em www.ine.pt. (Acessdo em março de 2012).
  www.ine.pt.... , it should be clarified that the Central Hospital is considered to be that one whose area of geographic intervention determines a hospital area of influence or part of it, and it is characterized by the existence of a great number of specialties. The number of existing specialties depends on whether the institution is a General Hospital, with a great number of existing specialties, or a Specialized Hospital, with a limited number of specialties. The Central Hospital corresponds to the most sophisticated and distinct level of care and is capable of providing care for all clinical situations, except for exceptional cases that can only be treated in a different Central Hospital. Apart from the health care function, this hospital type includes scientific research and it may have a teaching function and be associated with universities (University Hospital). District Hospitals are those whose geographic intervention area corresponds to a district or part of it and which can be classified according to the their levels of difference or specialties: basic district hospital , intermediate level district hospital or distinct level district hospital¹³13. Santos R. Tipos de Hospitais 1989 . Disponível em http://portalcodgdh.minsaude.pt/index. php (Acessado em 2009 e 2012).
  http://portalcodgdh.minsaude.pt/index.... . Level 1 district hospitals, also known as level 1 hospitals, are those whose hospitalization is usually limited to more basic specialties: Internal Medicine, General Surgery, Obstetrics, Gynecology and Pediatrics, apart from Orthopedics, which can be included in some cases¹⁴14. Instituto Nacional de Estatística (INE), 2002. Disponível em www.ine.pt. (Acessdo em março de 2012).
  www.ine.pt.... . Aiming to statistically treat or analyze the data, the operationalization of this variable was performed in the following way: 1. Central Hospital, 2. District Hospital, and 3. Level 1 District Hospital.

Results

Descriptive analysis

The sample was comprised of 47% district hospitals, 28% of central hospitals and 25% of level 1 hospitals. A total of 56% of hospitals with company management or Entidade Pública Empresarial (EPE – Public Company Institution) and 44% with Setor Público Administrativo (SPA – Public Administrative Sector) management were observed. In 2006, there was a mean surgical bed occupancy of 160 beds, a mean of 7,282 discharged patients and 47 discharged patients per bed, a mean of 42,147 patients-day, a mean stay of 5.6 days and a mean occupancy rate of 67%.

The mean population served by the hospitals was 433,791 users, with a mean of 5,922 surgical procedures performed (conventional and outpatient surgeries), including a mean of conventional surgeries of 4,399 and a mean of outpatient surgeries of 1,524, which corresponds to a mean percentage of outpatient surgeries of 24% (median of 23%) for the sample. Additionally, a mean of 38 nurses per conventional surgical ward and six nurses per outpatient surgical ward were found. The mean of conventional surgical wards was six, while that of outpatient surgical wards was one for the entire sample. The mean overall waiting time was 116 days, reflecting an improvement in waiting time values when compared to previous years. However, there is a great variation in the overall waiting time among different health units, ranging from 15 to 274 days. In the analysis of waiting time per type of surgery, the mean waiting time for conventional surgeries was 121 days and that for outpatient surgeries was 88 days. Moreover, in the analysis of waiting time per hospital type, the overall waiting time was higher among district hospitals (134 days), followed by central hospitals (119 days) and type 1 hospitals (87 days) and these differences were statistically significant ( Figure 1 ). The overall waiting time was identical for both the EPE and SPA types of management ( Figure 2 ).

Inferential analysis

There was a statistically significant inverse relation between the percentage of outpatient surgeries and overall waiting time for the entire sample, using Spearman's correlation ( Table 1 ).

Multiple linear regression analysis

The regression model initially included all independent variables of the study. Using a systematic analysis process of the importance of each variable in the developed models, those that were not relevant were eliminated step by step, according to the criteria of significance analysis of independent variables and those of maximization of the adjusted determination coefficient, through the Backward Stepwise procedure³⁵35. Harrell Jr. FE. Regression Modeling Strategies. New York; Ed. Springer-Verlag; 2001.. Subsequently, the analysis of outliers and refining of the model through exclusion of these outliers was performed. An outlier was considered as an observation in which the standard residue had an absolute value higher than 1.96 for a significance level of 5%. The estimates of coefficients of significant independent variables included in the model indicate the following ( Tables 2 and 3 ):

• ·

  The increase of 1% in the percentage of outpatient surgeries is associated with the reduction in the mean waiting time of 2.32 days, while the other variables remained constant;

• ·

  The district hospital type is associated with the increase in the mean waiting time of 27.18 days, while the other variables remained constant;

• ·

  The SPA management type is associated with the increase in the mean waiting time of 36.34 days, when compared to the EPE management type, while the other variables remained constant;

• ·

  The increase of one unit in surgical bed occupancy is associated with the increase in mean waiting time of 2.66 days, while the other variables remained constant;

• ·

  The increase of one thousand units in hospitalization days is associated with the increase in mean waiting time of 6.3 days, while the other variables remained constant;

• ·

  The increase in bed occupancy rate of 1% is associated with the increase in mean waiting time of 8.27 days, while the other variables remained constant;

• ·

  The increase in mean stay in a unit is associated with the reduction in mean waiting time of 84.51 days, while the other variables remained constant;

• ·

  The increase in the discharged patients/bed ratio in a unit is associated with the reduction in mean waiting time of 7.41 days, while the other variables remained constant;

• ·

  The increase of one nurse in the conventional surgical ward is associated with the reduction in mean waiting time of 1.13 days, while the other variables remained constant;

• ·

  The increase of one conventional surgical ward is associated with the increase in mean waiting time of 18.12 days, while the other variables remained constant;

• ·

  The increase in one unit in the number of conventional surgeries is associated with the reduction in mean waiting time of 0.015 days, while the other variables remained constant;

• ·

  The increase of one unit in the number of outpatient surgeries is associated with the increase in mean waiting time of 0.033 days, while the other variables remained constant;

• ·

  The increase of one surgeon is associated with the reduction in mean waiting time of 2.83 days, while the other variables remained constant.

Discussion

It could be concluded that there was an increase in the percentage of outpatient surgeries in 2006, compared to previous years, although with great variability among different health units, regardless of their geographic location or dimension (assessed in terms of surgical production), ranging between 0% and 75%. The analysis of human resources and materials found a greater amount of resources for conventional surgical wards, reflecting a clear numerical disadvantage of outpatient surgical wards in terms of facilities and health professionals specialized in this practice, which could be one of the reasons for their performance being lower than what was expected³⁸38. Department of Human Services, State Government of Victoria, Australia; 2007. Extended day surgery: Guidelines for the implementation and evaluation of 23-hour service models in Victoria . (versão electronica). Disponível em www.health.vic.gov.au/eletivesurgery (Acessado em 12 de novembro de 2007).
www.health.vic.gov.au/eletivesurgery...

39. Canadian Institute for Health Information; 2007. Surgical volume trends within and beyond wait times priority areas. (versão eletrônica). Disponível em www.cihi.ca (Acessado em 27 de outubro de 2007).
www.cihi.ca...

40. Taylor MC, Hadorn DC. Developing priority criteria for general surgery: results from the Western Canada Waiting List Project. Can J Surg 2002: 45(5): 351-7. (versão eletrônica). Disponível em www.ncbi.nlm.nih.gov/pubmed/ (Acessado em 26 de fevereiro de 2008).
www.ncbi.nlm.nih.gov/pubmed/...

41. The Australian Institute of Health and Welfare. Epidemiology and Health Information Branch; 1996. Variations in elective surgery procedure rates: intra-state and inter-state comparisons. (versão eletrônica). Disponível em www.health.qld.gov.au/publications/ infocirc Acessado em 23 de outubro de 2007).
www.health.qld.gov.au/publications/... ^{- 42}42. Department of Health. NHS. UK: 2002. Day surgery: Operational guide – waiting, booking and choice . (versão eletrônica). Disponível em www.dh.gov.uk/en/Publicationsandstatistics/ (Acessado em 29 de novembro de 2007).
www.dh.gov.uk/en/Publicationsandstatisti... .

The analysis of waiting time per hospital type showed that the waiting time for conventional surgeries (mean and median) and outpatient surgeries (mean and median) is higher in district hospitals than central hospitals, with statistically significant differences³⁴. The reasons for the poorer performance of district hospitals are associated with user-related factors (longer distance between the user's home and the hospital, greater difficulty in transportation), which are out the scope of this study³¹31. Ministério da Saúde. Cirurgia de Ambulatório: um modelo de qualidade centrada no utente – Relatório Final. Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório. Outubro de 2008. ^{, 41}41. The Australian Institute of Health and Welfare. Epidemiology and Health Information Branch; 1996. Variations in elective surgery procedure rates: intra-state and inter-state comparisons. (versão eletrônica). Disponível em www.health.qld.gov.au/publications/ infocirc Acessado em 23 de outubro de 2007).
www.health.qld.gov.au/publications/... ^{, 42}42. Department of Health. NHS. UK: 2002. Day surgery: Operational guide – waiting, booking and choice . (versão eletrônica). Disponível em www.dh.gov.uk/en/Publicationsandstatistics/ (Acessado em 29 de novembro de 2007).
www.dh.gov.uk/en/Publicationsandstatisti... ( Figures 1 and 2 ).

Spearman's correlation analysis ( Table 1 ) for the entire sample (73 health units with surgical services) confirms the hypothesis that the percentage of outpatient surgeries performed is associated with waiting time, so that the higher the percentage of outpatient surgeries, the shorter the mean overall waiting time. Thus, the multiple linear regression analysis confirmed the “percentage of outpatient surgeries” as a determinant variable of waiting time. Thus, the increase of 1% in the percentage of outpatient surgeries is associated with the decrease in overall waiting time of 2.32 days, while the other variables remained constant. Other variables directly associated with waiting time were “district hospital type” and “SPA management type”. “Percentage of outpatient surgeries”, “number of surgeons” and “number of nurses in the conventional surgical ward” were variables inversely associated with waiting time⁴⁶46. Martin S. Jacobs R. Rice N. Smith P. Waiting times for eletive surgery: a hospital – based approach. University of York Centre for Health Economics, Department of Economics; 2003. (versão eletrônica). Disponível em www.york.ac.uk/media/che/documents/reports/wait2.pdf (Acessado em 05 de novembro de 2007).
www.york.ac.uk/media/che/documents/repor...

47. McIntosh T, Fafard P et al. The taming of the queue IV: New frontiers of wait time measurement, monitoring, and management . Canadian Policy Research networks; 2007. (versão eletrônica). Disponível em www.cprn.org/ (Acessado em 06 de novembro de 2007).
www.cprn.org/... ^{- 48}48. Bosch X. Spain cuts waiting times for surgery. Br Med J 1999; 318: 71817181, 419; 93;117. (versão eletrônica). Disponível em www.bmj. bmjjournals.com (Acessado em 26 de fevereiro de 2008).
www.bmj.... ( Tables 2 and 3 ). The association with hospital management type – with the best performance being observed among the EPE hospitals – is encouraging in view of the reality experienced by Portugal, as it moves from the SPA model to the EPE model¹²12. OPSS. Relatório de Primavera 2008 . Observatório Português de Sistemas de Saúde; 2006. ^{, 13}13. Santos R. Tipos de Hospitais 1989 . Disponível em http://portalcodgdh.minsaude.pt/index. php (Acessado em 2009 e 2012).
http://portalcodgdh.minsaude.pt/index.... . The results of the regression analysis were in agreement with those found in other studies¹1. OECD. Towards High Performing Health Systems: the OECD Health Project (versão eletrônica); 2004. Disponível em www.oecd.org/dataoecd/ (Acessado em 10 de novembro de 2007).
www.oecd.org/dataoecd/... ^{, 22}22. Lemos P. A cirurgia em regime de ambulatório no HGSA – uma década de experiência . GICCA – HGSA 1998-2005.

23. Lemos P. Enquadramento nacional e internacional de cirurgia do ambulatório. Hospitais SA – Unidade de Missão ; 2003 (versão eletrônica). Disponivel em www.hospitaisepe.min-saúde.pt/ (Acessado em 12 de novembro de 2007).
www.hospitaisepe.min-saúde.pt/...

24. Natário A et al. Cirurgia de Ambulatório: recomendações para o seu desenvolvimento . DGS, Direcção de Serviços e Planeamento; 2001 (versão eletrônica). Disponível em www.srsdocs. com/parcerias/publicacoes/ (Acessado em 29 de novembro de 2007).
www.srsdocs....

25. Associação Portuguesa de Cirurgia de Ambulatório – APCA. I Inquérito Nacional de Cirurgia de Ambulatório ; 1999.

26. Associação Portuguesa de Cirurgia de Ambulatório – APCA. II Inquérito Nacional de Cirurgia de Ambulatório ; 2001. ^{- 27}27. Associação Portuguesa de Cirurgia de Ambulatório – APCA. III Inquérito Nacional de Cirurgia de Ambulatório ; 2003. ^{, 31}31. Ministério da Saúde. Cirurgia de Ambulatório: um modelo de qualidade centrada no utente – Relatório Final. Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório. Outubro de 2008., in terms of determining factors: infrastructure (number of wards available for surgery), human resources (number of surgeons and nurses available), hospital type, and hospital management type. The number of anesthesiologists was not found to be a determining factor of waiting time, although its number was lower (nearly half) than that of surgeons and although the lack of anesthesiologists had been considered as a relevant factor in other studies³¹31. Ministério da Saúde. Cirurgia de Ambulatório: um modelo de qualidade centrada no utente – Relatório Final. Comissão Nacional para o Desenvolvimento da Cirurgia de Ambulatório. Outubro de 2008. ^{, 34}34. Murteira JF. Análise Exploratória de Dados – Estatística Descritiva. Lisboa: Editora McGraw-Hill; 1993. ^{, 35}35. Harrell Jr. FE. Regression Modeling Strategies. New York; Ed. Springer-Verlag; 2001..

With regard to the model used in the multiple regression analysis, it should be emphasized that the hypothesis of “absence of multicollinearity”^35,36was not observed in the linear regression model constructed, probably due to the small dimension of the sample with regard to the number of variables. The fact that this hypothesis was not confirmed hinders the use of this model to predict waiting times, although this was not the main objective of the present study.

Conclusion

Despite the limitations of this type of study, the results obtained from the multivariate analysis showed that ambulatory surgery appears to be associated with shorter waiting time for elective surge­ries⁴²42. Department of Health. NHS. UK: 2002. Day surgery: Operational guide – waiting, booking and choice . (versão eletrônica). Disponível em www.dh.gov.uk/en/Publicationsandstatistics/ (Acessado em 29 de novembro de 2007).
www.dh.gov.uk/en/Publicationsandstatisti...

43. Department of Human Services. State Government of Victoria. Australia; 2007. Extended day surgery: Guidelines for the implementation and evaluation of 23-hour service models in Victoria . (versão eletrônica). Disponível em www.health.vic.gov.au/eletivesurgery (Acessado em 12 de novembro de 2007).
www.health.vic.gov.au/eletivesurgery... -⁴⁴44. Americano M. Recomendações para Programas de Cirurgia de Ambulatório . Direção Geral de Saúde, Lisboa: DGS; 2001.. Thus, it could be concluded that their development should be promoted as a strategy to improve access to health services⁴⁶46. Martin S. Jacobs R. Rice N. Smith P. Waiting times for eletive surgery: a hospital – based approach. University of York Centre for Health Economics, Department of Economics; 2003. (versão eletrônica). Disponível em www.york.ac.uk/media/che/documents/reports/wait2.pdf (Acessado em 05 de novembro de 2007).
www.york.ac.uk/media/che/documents/repor...

47. McIntosh T, Fafard P et al. The taming of the queue IV: New frontiers of wait time measurement, monitoring, and management . Canadian Policy Research networks; 2007. (versão eletrônica). Disponível em www.cprn.org/ (Acessado em 06 de novembro de 2007).
www.cprn.org/... ^{- 48}48. Bosch X. Spain cuts waiting times for surgery. Br Med J 1999; 318: 71817181, 419; 93;117. (versão eletrônica). Disponível em www.bmj. bmjjournals.com (Acessado em 26 de fevereiro de 2008).
www.bmj.... . Additionally, other potentially determining factors of waiting time for day surgeries could be identified and “hospital management type” and “number of surgical theatres available” were those that apparently had the greatest influence and are useful for the work of health authorities.

The present results must be interpreted according to the limitations of this study and a more in-depth analysis may be required in the future.

Conflicts of interest: authors declared no conflicts of interest.

Ethical approval: The present study was approved by the Research Ethics Committee of the Institute of Hygiene and Tropical Medicine (IHMT) at the New University of Lisbon.

Acknowledgements: Authors would like to thank Professor Paulo Pereira for his support in the statistical data treatment.

References

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