PREOPERATIVE ASSESSMENT

Preoperative assessment of outpatients has become increasingly important because patients are presenting for ambulatory surgery with more complex medical conditions and may be taking multiple chronic medications (see Chapter 25 ). It is essential to develop an effective method of screening these patients preoperatively to avoid costly delays and last-minute cancellations.^[6] Such screening may be accomplished by means of a telephone interview by a trained nurse^[65] or by a visit to a preoperative evaluation clinic.^{[66] [67]} The use of computerized questionnaires before preoperative evaluation by the anesthesiologist can also be a time-saving and efficient practice. Computerized questionnaires are more accurate in listing positive and negative historical information than a physician interview is and can be used to predict the need for preoperative laboratory testing. ^[68] Several laptop computer-based questionnaires have been developed, and clinical studies suggest that these computerized

2594

The use of a preoperative questionnaire along with a telephone screening interview was highly effective in reducing cancellations and surgical delays. ^{[69] [70]} However, when an assessment was performed 1 to 2 weeks before surgery in a preadmission clinic, it was reported to provide a benefit for only 6% of patients.^[71] A trained nurse using a rule-based computer program in which the identified medical problems and abnormal laboratory findings were reviewed by an anesthesiologist was found to reduce cancellation from 4.8% to 1.8%.^[72] It would appear that the quality of information obtained from the preanesthetic visit is improved by using a standardized questionnaire form.^[73]

Preoperative Evaluation

The primary objective of the preoperative assessment is to identify patients who have concurrent medical problems requiring further diagnostic evaluation or active treatment before surgery. Patients with specific anesthetic concerns (e.g., difficult airway, MH susceptibility) or those with a high risk for perioperative anesthetic and surgical complications should be identified. Preexisting medical conditions that may be associated with adverse events include hypertension (e.g., perioperative cardiovascular events); obesity, asthma, and smoking (e.g., perioperative respiratory events); and gastroesophageal reflux disease (e.g., intubation-related events).^{[51] [74]} Of the three primary components of a preoperative assessment (i.e., history, physical examination, and laboratory testing), the medical history is clearly the most valuable. ^{[75] [76]} Studies of medical ambulatory consultations showed that 86% of diagnoses depended entirely on the information obtained from the patient's history.^[76] A further 6% of diagnoses were discovered by careful physical examination, and only 8% were determined by laboratory investigations or radiographs. Routine preoperative laboratory testing of patients before ambulatory surgery is unjustified and wasteful of health care resources.^[77]

Studies have found that over 60% of routinely ordered preoperative screening tests would be eliminated if testing were based solely on recognizable indications and that

TABLE 68-4 -- Laboratory test recommendations for outpatients scheduled to undergo ambulatory surgery procedures under general anesthesia

Age Range	Men	Women
<40	None	Pregnancy test *
40–49	Electrocardiogram	Hematocrit level, pregnancy test *
50–64	Electrocardiogram	Hemoglobin or hematocrit level, electrocardiogram
65–74	Hemoglobin or hematocrit level, electrocardiogram, serum urea nitrogen, glucose	Hemoglobin or hematocrit level, electrocardiogram, serum urea nitrogen, glucose
>75	Hemoglobin or hematocrit level, electrocardiogram, serum urea nitrogen, chest radiograph †	Hemoglobin or hematocrit level, electrocardiogram, serum urea nitrogen, chest radiograph †
Modified from Roizen MF: Cost-effective preoperative laboratory testing. JAMA 271:319, 1994. Copyright 1994. American Medical Association.

*If a woman of childbearing potential cannot rule out being pregnant.
†The benefit-risk ratio of a chest radiograph for asymptomatic individuals older than 50 years is not clear.

For otherwise healthy outpatients undergoing superficial surgical procedures (e.g., biopsy, dilatation and curettage, herniorrhaphy, arthroscopy, vein stripping), no laboratory tests appear to be indicated in males, and only a hemoglobin (or hematocrit) test may be appropriate for females. Obviously, patients with chronic diseases (e.g., hypertension, diabetes) require additional laboratory studies (e.g., electrolytes, glucose). Patients with an unexplained hemoglobin concentration of less than 10 g/dL should undergo further evaluation before elective outpatient surgery because a low hemoglobin level may be associated with diseases that could influence perioperative mortality and morbidity. Eliminating routine preoperative testing (even in elderly outpatients) will allow cost savings without compromising the safety and quality of patient care ( Table 68-4 ).^{[79] [80] [81] [82]}

In addition to the anesthesiologist's evaluation, the preoperative visit could be used by the nursing staff to assess, prepare, and educate the patient; by the facility's business office to perform a financial interview; and to familiarize the patient and family with the center. To avoid unexpected delays resulting from incomplete assessment, all paperwork, including the consent form, history and physical examination, and laboratory test results, should be reviewed before arrival for surgery. A well-planned and smooth-functioning ambulatory surgery program can yield many benefits to patients and their families, as well as to surgeons. Appropriate patient preparation before the day of surgery can prevent unnecessary delays, absences ("no shows"), last-minute cancellations, and inadequate perioperative care.