Preoperative medical evaluation of the healthy patient

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Recommendations

General recommendations for routine preoperative laboratory studies in healthy patients include the following :

Complete blood count

Anemia is present in approximately one percent of asymptomatic patients; surgically significant anemia has an even lower prevalence. However, anemia is common following major surgery. Thus, a baseline hemoglobin measurement is recommended in patients who are undergoing surgery that is expected to result in significant blood loss. In contrast, hemoglobin measurement is not necessary for those undergoing minor surgery unless the history is suggestive of anemia. The frequency of significant unsuspected white blood cell or platelet abnormalities is also low. Unlike the hemoglobin concentration, however, there is little rationale to support baseline testing of either. Nevertheless, obtaining a complete blood count, including white count and platelet measurement, can be recommended if the cost is not substantially greater than the cost of a hemoglobin concentration alone.


Electrolytes

The frequency of unexpected electrolyte abnormalities is low, 0.6 percent

in one report. Routine electrolyte determinations are not recommended unless the patient has a history that increases the likelihood of an abnormality (e.g., current use of diuretics).

Renal function

Mild to moderate renal impairment is usually asymptomatic; the prevalence of an elevated creatinine among asymptomatic patients with no history of renal disease is only 0.2 percent. However, the prevalence increases with age. Renal insufficiency can be associated with excess surgical morbidity, and necessitates dosage adjustment of some medications that may be used perioperatively (e.g., muscle relaxants). Serum creatinine concentrations must be measured in patients over the age of 50. It should also be ordered when hypotension is likely or when nephrotoxic medications will be used.

Blood glucose

The frequency of glucose abnormalities increases with age. However, the incidence of asymptomatic hyperglycemia is unknown. Controlled studies have not found a relationship between operative risk and diabetes, except in those undergoing vascular surgery or coronary artery bypass grafting. Thus, routine measurement of blood glucose is not recommended prior to elective surgery; exceptions may include those at high risk for diabetes (e.g., obese patients, steroid use, or those with family history).

Liver function tests

Unexpected liver enzyme abnormalities are uncommon. Severe liver function abnormalities are associated with increased surgical morbidity and mortality, but it is not clear if mild abnormalities have a similar impact. Clinically significant liver disease would most likely be suspected on the basis of the history and physical examination; thus, routine liver enzyme testing is not recommended.

Tests of hemostasis

Unexpected abnormalities of the prothrombin time (PT) or partial thromboplastin time (PTT) are uncommon, particularly if one is trying to identify severe abnormalities that are likely to result in a change in preoperative management. In addition, the relationship between an abnormal result and the risk of perioperative hemorrhage is not well defined, but appears to be low, particularly in those who are thought to The two theoretical reasons to obtain a preoperative urinalysis are to identify unsuspected renal disease or urinary tract infection.However, the urinalysis is not necessary for the detection of asymptomatic renal disease if a serum creatinine measurement is obtained. In addition, the relationship between asymptomatic urinary tract infection and surgical infection is unclear. There is no difference in the rate of wound infections between those patients with abnormal preoperative urinalyses and those with normal preoperative studies. Routine urinalysis is not recommended preoperatively for most surgical procedures.

Electrocardiogram

Routine electrocardiograms (ECGs) have a low likelihood of changing perioperative management in the absence of known cardiac disease. Nevertheless, detecting a recent myocardial infarction is important since it is associated with high surgical morbidity and mortality. In addition, unrecognized infarctions may be relatively common; the proportion of unrecognized infarcts is higher in women and in older men. The prevalence of abnormal ECG's increases exponentially with age. Important ECG abnormalities in patients younger than 45 years with no known cardiac disease are very infrequent. Detecting unsuspected arrhythmias may also impact perioperative risk; a rhythm other than sinus, premature atrial contractions, or more than five premature ventricular beats on a preoperative ECG all increase the risk of perioperative cardiac events. In addition, a preoperative ECG can be important as a baseline to compare with postoperative ECG abnormalities.

An ECG must be obtained in:

  • Men older than 45 years

  • Women older than 55 years

  • Known cardiac disease

  • Clinical evaluation suggesting the possibility of cardiac disease

  • Patients at risk for electrolyte abnormalities, such as diuretic use

  • Systemic disease associated with possible unrecognized heart disease, such as diabetes mellitus or hypertension

  • Patients undergoing major surgical procedures

Chest radiograph

Abnormal chest x-rays are seen with increasing frequency with age. However, chest x-rays add little to the clinical evaluation in identifying patients at risk for perioperative complications. One study screened 905 surgical admissions for the presence of clinical factors that were thought to be risk factors for an abnormal preoperative chest x-ray ( age over 60 years, or clinical findings consistent with cardiac or pulmonary disease). No risk factors were evident in 368 patients; of these, only one (0.3 percent) had an abnormal chest x-ray, which did not affect the surgery. On the other hand, 504 patients had identifiable risk factors; of these, 114 (22 percent) had significant abnormalities on preoperative chest x-ray. These findings were supported by a meta-analysis of 21 studies of routine chest radiography. Of a total of 14,390 routine chest x-rays, there were 1444 abnormal studies; only 140 were unexpected, and only 14 (0.1 percent) of all routine chest x-rays influenced management. Thus, preoperative chest x-rays should not be routinely performed. An exception is in patients over the age of 60 and those with suspected cardiac or pulmonary disease. Although the relationship between the findings on chest x-ray and perioperative morbidity are not well defined in these populations, it is reasonable to look for unanticipated findings since they are relatively common.

Pulmonary function tests

Routine pulmonary function tests are not indicated for most healthy patients prior to surgery. These tests generally should be reserved for patients who have uncharacterized dyspnea. However, there are some subsets of patients in whom preoperative spirometry is warranted to determine the risk of postoperative pulmonary complications. The American College of Physicians suggests obtaining spirometry in the following circumstances:

  • Patients undergoing resective lung surgery, coronary bypass surgery or upper abdominal surgery with a history of tobacco use or dyspnea

  • Patients undergoing head and neck or orthopedic surgery with uncharacterized pulmonary disease

  • All patients undergoing lung resection

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