Despite the low morbidity and mortality associated with cataract surgery, a preoperative medical evaluation is often performed to “clear” patients for surgery. The Agency for Health Care Policy and Research (now known as the Agency for Healthcare Research and Quality) guidelines for the management of cataracts, published in 1993, endorsed “appropriate” testing but did not specify which tests were necessary. In a nationwide survey, the majority of ophthalmologists, anesthesiologists and internists believed that routine preoperative tests are not necessary for cataract surgery but stated that they order them because of institutional requirements, medicolegal concerns or the assumption that another physician wants the testing done. Schein and colleagues performed a large study to assess whether the information obtained on preoperative testing plays a role in reducing the peri- and postoperative complications of cataract surgery.
The randomized prospective study was conducted at nine medical centers and included 19,557 cataract operations in 18,189 patients. Excluded were patients who were less than 50 years of age, who were to receive general anesthesia, who had sustained a myocardial infarction within the previous three months or who had any preoperative testing during the 28 days before enrollment.
A medical history and physical examination were obtained in each patient. Patients were randomly assigned to have routine preoperative tests or not to have such tests. Pre-operative testing consisted of a 12-lead electrocardiogram, complete blood count and determination of serum electrolyte, blood urea nitrogen, creatinine and glucose levels.
The authors assessed the occurrence of the following adverse events: myocardial ischemia, myocardial infarction, congestive heart failure, cardiac arrhythmia, hypertension, hypotension, stroke, transient ischemic attack, bronchospasm, respiratory failure, oxygen desaturation, diabetic ketoacidosis, nonketotic hyperosmolar syndrome and hypoglycemia. In addition, a new or worsening medical problem that required treatment was also considered an adverse event. When an adverse event was suspected by the data collectors, the case was reviewed by two physicians to assure that the event met the study definition of an adverse event. If so, the case was then reviewed by two additional physicians who made a clinical judgment as to whether preoperative testing would have affected the probability of the event occurring and whether a relationship between the event and cataract surgery was plausible.
Perioperative data were available for 100 percent of the 18,189 patients and one-week postoperative data were available for 99.8 percent of the patients. The mean age of the entire group was 73 years; 60 percent were women. The preoperative testing group and the group not undergoing preoperative testing had the same cumulative rate of medical events (31.1 per 1,000 operations). The most common events were hypertension and arrhythmias (primarily bradycardia), constituting 68 percent of the adverse events in the preoperative testing group and 61 percent of the adverse events in the group not having preoperative testing. Two deaths occurred in patients who did not have preoperative testing and one death occurred in the patients who received preoperative testing.
One third of the adverse events in both groups had a plausible causal relationship to cataract surgery. When the data were further stratified for age, race, sex, coexisting illness and anesthesia risk class, there was again no difference between the two groups. It was calculated that preoperative testing might have decreased the likelihood or the severity of the event for 5.9 and 4.2 percent of the intraoperative events in the no-testing and routine-testing groups, respectively. For postoperative events, it was calculated that preoperative testing would have decreased 6.6 percent and 16.4 percent of the events in the preoperative testing and the no-testing groups, respectively.
The authors conclude that routine testing before cataract surgery does not reduce perioperative morbidity and mortality. They state that most abnormalities can be predicted on the basis of an adequate history and physical examination. Moreover, when laboratory abnormalities are found, they rarely seem to lead to changes in perioperative management. The authors believe the common practice of obtaining routine preoperative tests for cataract surgery should be eliminated.
editors note: According to the authors of this study, the annual cost of routine medical testing before cataract surgery is more than $150 million. The findings from this study may cause primary care physicians, ophthalmologists and anesthesiologists to alter the practice of obtaining preoperative tests in patients who are scheduled for cataract surgery. It is likely that similar findings would be documented regarding the value of preoperative testing for other types of outpatient surgery.—j.t.k.