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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.56 no.6 Campinas Nov./Dec. 2006
Preoperative exams: a critical analysis*
Exámenes complementarios preoperatorios: análisis crítico
Lígia Andrade da Silva Telles Mathias, TSAI; Álvaro Antonio Guaratini, TSAII; Judymara Lauzi Gozzani, TSAIII; Luiz Antonio RivettiIV
do Serviço e Disciplina de Anestesiologia da FCM-ISCMSP; Professora Adjunta
de Anestesiologia; Responsável pelo CET/SBA, ISCMSP
IIMestre em Medicina, Doutorando da FCM-ISCMSP, Médico Assistente - Hospital Central da ISCMSP
IIIMestre em Biologia Molecular, Doutora em Medicina, Médica Assistente - Hospital Central da ISCMSP
IVProfessor Adjunto do Departamento de Cirurgia e Chefe da Disciplina de Cirurgia Cardíaca da FCM-ISCMSP
CONTENTS: The results obtained from a systematic revision of the evidence available from 1966 to 1996, from the recommendations of the task force of the American Society of Anesthesiologists, from the systematic revision of evidence from 1997 to 2002, and from the English National Health Service Orientation Guide.
CONCLUSIONS: Preoperative exams should not be based on standard routines, but on the patient's history, physical exam, and type and extent of surgery.
CONTENIDO: Se analizaron los resultados observados en revisión sistemática con las evidencias disponibles entre los años 1966 y 1996, en recomendaciones del contingente de la Sociedad Norteamericana de Anestesiólogos, en actualización de la revisión sistemática incluyendo evidencias desde 1997 a 2002 y en el Guía de Orientación del National Health Service de la Inglaterra.
CONCLUSIONES: los exámenes preoperatorios no deben ser solicitados basados en rutinas, sino orientados por la hoja clínica, por el examen físico y por el tipo y porte del procedimiento quirúrgico.
Preoperative exams are aimed at identifying or diagnosing diseases and dysfunctions that can endanger the perioperative management; evaluate the functional dysfunction caused by diseases that had already been diagnosed and are being treated; and to help formulate specific or alternative plans for the anesthetic care 1.
One should consider relevant criteria, disease prevalence, and the sensibility and specificity of the exams when requesting preoperative exams. Some diseases, such as cardiac and respiratory, due to their relevance, may interfere in the choice of the anesthetic technique and in the evolution of the patient. The very low prevalence of specific diseases in asymptomatic patients does not justify the usefulness of the exam in decreasing morbidity. Exams with low sensitivity may lead more frequently to false negative results and, therefore, patients with risk factors for specific morbidities who are evaluated by those exams are scheduled for surgery without the proper preoperative care 2. On the other hand, exams with low specificity have a higher incidence of false positive results, leading to the realization of further exams, therefore increasing costs and morbidity 3. The current tendency is to request preoperative exams according to the patient's history or physical exam; the needs of the surgeons or residents that treat the patient; and monitoring of exams that might change during the surgery or associated procedures 2,4.
From 1960 to 1980, laboratory exams were considered the ideal screening method for preexisting diseases or those yet to be diagnosed. A "batch" of exams was done for virtually every patient undergoing surgery, regardless of age, physical status, or type of surgery, even for the simplest procedures 5,6. From the 1990s on, due to cost rationalization, there was the preoccupation of limiting the number of exams only to those that were really indicated, according to the patient's history and physical exam 7-10.
It is estimated that about 10% of the 30 billion dollars spent annually in the USA with laboratory exams correspond to preoperative exams. When one takes into account the patient's history and physical exam, 60% to 70% of laboratory exams are not really necessary 11-20. After defining the minimal standards for laboratory exams, there was a reduction in hospital costs without decreasing the quality of preoperative evaluation 21-31.
ANALYSIS OF THE LITERATURE
Searching the literature from 1961 on, we found a large number of reports on the subject. However, due to the reach, extension, and analytical inference capability of each one, there are three main sources to be analyzed 1.
These publications are: the Systematic Review, published by Munro et al. (1997) of the Health Technology Assessment (HTA), a division of the National Health Service (NHS), the English organ equivalent to the Ministry of Health, that encompasses all the evidence available from 1966 to 1996 32, the Practice Advisory for Preanesthesia Evaluation, of the Task Force (TF) of the American Society of Anesthesiologists (ASA) 1, the Evidence, Methods & Guidance of the above mentioned HTA-NHS 33, the 1997 systematic revision (1997-2002), and informal and formal consensus, discussions in closed forums about the results of the questionnaire and a final consensus.
Table I presents the main characteristics and differences among the three publications.
The three sources mentioned considered "routine" exams those requested to identify conditions that were not detected by the clinical history and physical exam in seemingly healthy, asymptomatic patients, and without any clinical indication 1,32,33 (Tabelas II a XI).
Joo et al. 34 published a systematic revision of the value of preoperative X-rays as a diagnostic tool. They found 14 reports that fulfilled the inclusion criteria; the studies were non-controlled and non-randomized. They concluded that the number of changes observed in chest X-rays increased with age and with the number of risk factors, and that most changes neither modified the perioperative management nor affected the postoperative evolution.
Munro et al. 32 concluded that "routine" preoperative exams presented little or no benefit to apparently healthy patients. However, they argued that it was not clear yet whether or not "routine" exams benefit a population of asymptomatic patients that present a higher risk for intraoperative complications, such as the elderly.
The ASA-TF 1 and the HTA-NHS 33 concluded that, according to the original text of ASA-TF the available literature does not have rigorous enough information on preoperative routine exams allowing non-ambiguous recommendations to be made. Thus, it was proposed that routine preoperative exams should not be made. Instead, exams should be requested in order to guide and optimize perioperative management, and that the indication of preoperative exams should be based on information obtained from the patient's chart, history, and physical exam, and type and scale of the surgical procedure.
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Dra. Lígia Andrade da Silva Telles Mathias
Alameda Campinas, 139/41
01404-000 São Paulo, SP
Submitted for publication
10 de março de 2006
Accepted for publication 07 de agosto de 2006
* Received from Faculdade de Ciências Médicas da Irmandade da Santa Casa de Misericórdia de São Paulo (ISCMSP), São Paulo, SP