NMS. Casos Clínicos

17

Chapter 1 ♦ Preoperative Care

have a rapid cardiac workup prior to surgery. This should include a comparison of the pre- vious ECG with the current ECG . Because the patient has rest pain, so the patient would not tolerate an exercise stress test, but the patient should undergo a Persantine thallium stress test or dobutamine echocardiogram to assess current cardiac status. If reversible ischemia is present, the patient may need a cardiac cathe- terization to determine whether a coronary revascularization procedure is necessary prior to lower extremity bypass. Case Variation 1.6.2. The patient tells you that he had an acute MI 3 years ago. The most common cause of early postoperative death following lower extremity revascularization is MI. ◆ ◆ Studies have found that the rate of reinfarction with prior history of MI is as high as 15% in patients undergoing vascular surgery and rises to 37% in patients who have had a recent MI . The risk of cardiac death or recurrent MI decreases as the duration from surgery increases (i.e., the time interval between MI and surgery). ◆ ◆ The patient should undergo a stress test. If reversible ischemia is present, the patient should undergo cardiac catheterization. If only an irreversible defect is present, no cardiac cathe- terization is necessary if no other abnormalities are present. The irreversible defect is most likely due to his old MI. Case Variation 1.6.3. The patient tells you that he had an acute MI 3 months ago. ◆ ◆ In 2009, the ACC/AHA proposed a set of guidelines to estimate coronary risk related to noncardiac surgery (see Table 1-2). Because he is having a vascular procedure performed, he should have a cardiology evaluation and stress test performed. Occurrence of MI more than 30 days before noncardiac surgery is an intermediate risk factor. Case Variation 1.6.4. The patient tells you that there was an acute MI 3 weeks ago. ◆ ◆ The ACC/AHA criteria stipulate that MI within 30 days of noncardiac surgery is a major risk factor for perioperative cardiac complications. If possible, the surgery should be delayed . Case Variation 1.6.5. The patient tells you that he had a non–Q-wave MI 9 months ago. ◆ ◆ Non–Q-wave MIs generally signify a nontransmural infarct , which leaves peri-infarct myocardium at risk for further infarction during and after surgery. This patient should have a stress test to determine whether reversible ischemia is present. If so, coronary revas- cularization may be necessary before surgery. Case Variation 1.6.6. The patient’s ECG shows left bundle branch block (LBBB). ◆ ◆ The presence of this conduction disturbance should prompt a careful evaluation for underlying cardiopulmonary disease . If invasive intraoperative monitoring is necessary in patients with LBBB, placement of a pulmonary artery catheter increases the risk of con- current right bundle branch block (RBBB), so transthoracic pacing capabilities should be readily available. RBBB is a normal variant in up to 10% of the general population, but it is more frequently seen in patients with significant pulmonary disease . SAMPLE ◆ ◆ LBBB is never a normal variant and is highly suggestive of underlying isch- emic heart disease.