Print version ISSN 1020-4989
Rev Panam Salud Publica vol.10 n.1 Washington Jul. 2001
Objective. The objective of this study was to investigate whether routine medical testing before cataract surgery reduces the rate of complications during the perioperative period in adults.
|Cataracts, utilization of health services, elderly, diagnostic tests, preoperative care.|
Around the world, cataracts are the most prevalent cause of visual loss, and an increase in their number can be expected over the next several decades as the median age of the population rises (1-3). The only effective treatment for cataracts is surgery, but cataract surgery has fortunately become one of the safest, most successful, and most frequently performed outpatient surgeries (4-6).
Previous studies in developed countries have demonstrated that physicians usually request routine tests regardless of the patient's preoperative status, but there is a lack of information relative to developing countries (7, 8). Some of the reasons for requesting nonselective tests are that cataract patients tend to be elderly and to have serious coexisting illnesses; another common argument is that the individual cost of tests is low (1, 9, 10).
That accepted dogma regarding the validity of preoperative medical testing is now being questioned, and what was considered optimum preoperative care is being reassessed worldwide from the perspective of medical necessity and costs (11, 12). The need for routine laboratory tests before cataract surgery and other types of elective surgery has been questioned in several studies (8, 9, 11). There is evidence that selective requests for preoperative tests would be a more rational approach (7, 8, 13). Arterial hypertension, bronchospasm, and arrhythmia account for more than 90% of intraoperative medical events in cataract surgery, and routine tests do not appear to predict them (9, 14).
Seventy percent of laboratory tests ordered preoperatively in general surgery are not required, based on the patient history and the results of phys-ical examination (15, 16). More than 250 000 cataract surgeries are performed each year in Brazil (17). Given the number of those operations, there is a significant potential economic impact to rationalizing preoperative testing for low-income populations in developing countries and for public health services that are under functional and economic strain. And while true now, that concern will grow in the future as the populations of developing countries continue to age.
The aim of this prospective randomized clinical trial was to investigate whether routine medical testing before cataract surgery reduced the rate of complications during the perioperative period.
Patients and medical procedures
The study was carried out in an academic medical center in Brazil. The medical center's human-subjects committee approved the study protocol. All the surgeries were performed at that same academic medical center, at the State University of Campinas, Brazil.
Patients scheduled to undergo cataract surgery were recruited between 10 February 2000 and 10 January 2001. Patients were excluded from the study if they were less than 40 years old, were undergoing surgery on the second eye, were to receive general anesthesia, or had had a myocardial infarction within the preceding 3 months. All patients provided written informed consent before enrollment in the study.
For the patients who agreed to participate in the study, the scheduled cataract operation was randomly assigned to one of two groups: 1) to be preceded by routine testing (the "routine-testing group") or 2) not to be preceded by routine medical testing (the "selective-testing group"). All patients had a preoperative medical assessment performed by a physician. If the patient was assigned to the selective-testing group, it was requested that no preoperative testing be performed unless the patient presented with a new or worsening medical problem that would warrant medical evaluation with testing, even if surgery were not planned. For patients assigned to the routine-testing group it was requested that three tests be done: a 12-lead electrocardiogram, a complete blood count, and measurements of serum glucose.
Data collection and outcomes
Preoperative data were collected by means of a medical-history form, completed by the physician at the time of preoperative medical examination. Intraoperative medical events and treatments were recorded on a standardized form by the ophthalmologist or a member of the nursing staff.
The definitions of adverse medical events used in the study are listed in Table 1. Two of the study's researchers, an internist and a cardiologist, reviewed the relevant medical records in order to determine whether one of the study's definitions of an adverse event was met. These reviewers were not informed of the study-group assignment of the patients. Medical events that occurred before discharge on the day of surgery were considered as related to the surgery. We did not include medical events after discharge because of difficulties in following up these patients.
Sample size and statistical analysis
A sample size of 1 000 patients (500 per group) was planned. With an assumption of an adverse medical event rate of 9% in the routine-testing group, this sample size provided a 90% probability of detecting a difference as small as 7% in the selective-testing group. Results of these analyses were considered as statistically significant when the P values were < 0.05. We used Epi Info 2000 computer software (United States Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America) for the statistical analyses. For categorical variables, chi-square (Yates) tests and Fisher's tests were used; for continuous variables, one-way analysis of variance (ANOVA) tables were used.
We enrolled 1 025 patients scheduled to undergo cataract surgery between 10 February 2000 and 10 January 2001. The sample consisted of 512 patients assigned to the routine-testing group and 513 patients assigned to the selective-testing group. The two groups had similar proportions of operations that were canceled and not subsequently rescheduled, 2% in each group.
The two groups were well balanced in terms of age, with a mean age of 66.4 years (standard deviation (SD) = 11.9 years) among the routine-testing group and of 66.7 years (SD = 11.4 years) among the selective-testing group (ANOVA P = 0.734). The groups were also well balanced with respect to sex and risk of perioperative complications (Table 2) as well as coexisting illness (Table 3).
The cumulative rate of medical events was similar in the two groups, 9.6% in the routine-testing group and 9.7% in the selective-testing group (P = 0.923). The types of medical events were similar in both groups (Table 4). Treatment for hypertension accounted for 85.4% of the events in the routine-testing group and 87.8% of the events in the selective-testing group.
At the beginning of the 21st century, in terms of cataracts, worldwide there were 25 million blind individuals (visual acuity (VA) < 3/60) and 110 million visually impaired individuals (VA < 6/60) (1, 3, 19). In an era when cost-benefit analysis is applied to all aspects of medical practice, including cataract surgery (20), unselective preoperative routine testing is no longer justified.
Forty years ago, physicians relied primarily on history-taking and physical examination to make preoperative medical assessments of cataract patients. Tests were ordered selectively to confirm clinical impressions. With advances in technology and the growing use of multiphasic batteries of laboratory tests, the goal became to formulate an early, presymptomatic diagnosis so as to optimize care. However, the use of these batteries of tests magnified two problems: the need to determine which tests, if any, should be required preoperatively, and the question of what should be done when test results are unexpectedly abnormal (21).
Ambulatory surgical procedures on an outpatient basis have proliferated in the last 20 years, as it became apparent that many procedures could be done in an ambulatory setting more cheaply and yet safely (22, 23). There are controversies regarding requests for preoperative tests for brief outpatient procedures. For patients undergoing cataract surgery there is a marked variation within and across physician specialties concerning the use of and rationale for medical tests, according to a survey conducted with ophthalmologists, anesthesiologists, and internists in the United States of America (24).
Too little knowledge can be a dangerous thing. Nonetheless, the apparent remedy¾acquiring new information¾may create a more hazardous situation. In comparison to selectively ordered laboratory testing, screening-laboratory testing is a less comprehensive, less efficient, and less cost-effective tool, and it can lead to further unnecessary studies or treatments, costly delay in the performance of the procedures, and adverse medicolegal consequences if abnormal results are overlooked (8, 9, 14, 25).
The use of selective laboratory testing based on the medical history and the judgment of the surgeon in collaboration with capable consultants has been shown to be effective in recognizing subclinical problems in high-risk individuals and managing potentially complicating conditions (8, 9, 13, 26, 27).
Our study had some limitations. It registered only clinically significant morbidities; for example, isolated atrial extrasystoles and other minor arrhythmias were not included. Another limitation was that a relatively succinct routine was adopted for patients assigned to the routine-testing group, applying just three tests: 12-lead electrocardiogram, complete blood count, and measurements of serum glucose. Nevertheless, those are the most-requested preoperative tests for cataract surgery, and they were the standard routine at the academic medical center where this study was done (23, 24). Another limitation was that medical events related to the surgery were limited to just the period after the ambulatory procedure and before discharge. However, in one study (9), that period encompassed more than 75% of the cardiopulmonary events occurring within 7 days after the surgery. It is important to emphasize that the focus of our study was a relatively healthy population undergoing a low-risk procedure.
We believe medical assessment provides an important opportunity for physicians to reduce perioperative morbidity by optimizing preoperative status and planning perioperative management. However, the clinical usefulness of routine preoperative medical testing before cataract surgery is unproven. The results of this study suggest that routine medical testing before cataract surgery does not reduce the rate of complications during the perioperative period, and that it would be more efficient not to request routine preoperative tests unless they are indicated by patient history or physical examination. We think this is particularly true in developing countries, with their limited financial resources and their desire to clear the backlog of cataract cases.
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Manuscript received 27 April 2001. Revised version accepted for publication on 27 June 2001.
¿Es necesario hacer pruebas clínicas rutinarias antes de la cirugía de cataratas?
Objetivos. El objetivo de este estudio consistió en determinar si la realización rutinaria de pruebas clínicas antes de la cirugía de cataratas reduce la tasa de complicaciones perioperatorias en adultos.
1 State University of Campinas ¾ UNICAMP, Department of Ophthalmology, Campinas, São Paulo, Brazil. Send correspondence to: Rodrigo Pessoa Cavalcanti Lira, Rua Visconde de Itaparica n. 174, apt. 203 B, 50710-090 ¾ Recife - PE ¾ Brazil; telephone: 55 81 3228.0510; fax: 55 81 3231.5532; e-mail: email@example.com