Test yourself: Preoperative evaluation

The following cases and commentary, which address preoperative evaluation, are excerpted from ACP's Medical Knowledge Self-Assessment Program (MKSAP 14).

Case 1: Mass in the adrenal gland

A 38-year-old woman is found to have a 3 cm heterogeneous mass in the right adrenal gland during evaluation for abdominal discomfort. Plasma fractionated metanephrines are twice the upper limit of normal concentration. A 24-hour urine collection for metanephrines contains 2.5 times the normal daily excretion. Pheochromocytoma is suspected and laparoscopic adrenalectomy is planned within the next 14 to 21 days.

The blood pressure is 206/110 mm Hg, and the pulse rate 104/min. She is taking no medication at this time.

Which of the following would be indicated first before surgery?

A. Carvedilol therapy
B. Blood transfusion
C. Fine-needle aspiration of the mass
D. Phenoxybenzamine therapy

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Case 2: Renal transplantation

A 35-year-old man with a 20-year history of type 1 diabetes mellitus is undergoing preoperative evaluation for renal transplantation. His clinical course has been complicated by hypertension, diabetic retinopathy, and peripheral neuropathy that limits his ability to walk. His blood pressure is 142/85 mm Hg. His LDL cholesterol is 140 mg/dL (3.62 mmol/L) and his HDL cholesterol is 30 mg/dL (0.78 mmol/L). He currently smokes a half of a pack of cigarettes daily. His electrocardiogram is shown. Medical consultation is requested for evaluation of his preoperative cardiovascular risk.

Which of the following is the most appropriate recommendation at this time?

A. No further evaluation is needed
B. Serum C-reactive protein level
C. 24-hour electrocardiographic monitoring
D. Pharmacologic stress nuclear study
E. Coronary angiography

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Case 3: Colon mass

A 54-year-old woman undergoes urgent preoperative evaluation before resection of a partially obstructing mass in the descending colon. She has lost 9 kg (20 lb) over the past 6 months. Her history includes moderately severe chronic obstructive pulmonary disease (COPD) but no known coronary artery disease. She smokes 1 pack of cigarettes daily. Her only medication is a combined ipratropium–albuterol oral inhaler.

On physical examination, she appears ill. The blood pressure is normal. Weight is 48.9 kg (108 lb). Oxygen saturation is 88% on room air. On cardiopulmonary examination, the lungs are clear, with distant breath sounds and a prolonged expiratory phase, and the heart has a regular rhythm without murmur or gallop. On abdominal examination, high-pitched bowel sounds are heard, and a 6 cm mass, tender to palpation, is detected in the left lower quadrant of the abdomen. Laboratory tests are normal except for a hemoglobin of 10.0 g/dL (100 g/L) and a serum albumin level of 2.9 g/dL (29 g/L). The chest radiograph shows only changes consistent with COPD, and the electrocardiogram is normal.

In addition to routine use of scheduled bronchodilator treatments and supplemental oxygen, which of the following strategies is most appropriate in preventing postoperative pneumonia in this patient?

A. Intravenous hyperalimentation
B. Prophylactic corticosteroids
C. Prophylactic antibiotics
D. Incentive spirometry
E. Enteral hyperalimentation

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Case 4: Nephrectomy

A 55-year-old man presents for a preoperative evaluation. The patient will undergo nephrectomy in 1 week for treatment of renal cell carcinoma with local extension outside the kidney but no distant metastases. The remainder of the medical history is unremarkable, and the physical examination is noncontributory.

Preoperative hemoglobin is 11 g/dL (110 g/L). He is anticipated to lose at least 3 units of blood during surgery, and perhaps more if the tumor bed is highly vascular.

Which of the following approaches is most likely to minimize this patient's need for donor transfusion?

A. Preoperative erythropoietin for 4 weeks
B. Preoperative autologous blood donation
C. Intraoperative acute normovolemic hemodilution
D. Intraoperative cell salvage

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Case 5: Symptomatic gallstones

A 32-year-old obese woman with type 2 diabetes mellitus is scheduled to undergo laparoscopic cholecystectomy for treatment of symptomatic gallstones. Abdominal ultrasonography shows multiple gallstones without cholecystitis and a normal common bile duct caliber.

Lab studies show a plasma glucose of 180 mg/dL (9.99 mmol/L), serum aspartate aminotransferase of 52 U/L, serum alanine aminotransferase of 60 U/L, serum alkaline phosphatase of 90 U/L and serum total bilirubin of 0.6 mg/dL (10.26 µmol/L).

Which of the following studies should be performed preoperatively?

A. Endoscopic retrograde cholangiopancreatography
B. Biliary scintigraphy (HIDA scan)
C. CT scan of the abdomen
D. No additional tests are needed

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Case 6: Trauma-induced aseptic necrosis

A 40-year-old man undergoes preoperative evaluation for trauma-induced aseptic necrosis requiring hip replacement. His medical history is noncontributory, and no lymphadenopathy or hepatosplenomegaly was noted on physical examination.

Preoperative hemoglobin was 14.5 g/dL (145 g/L). The patient has type Group O blood, is Rh positive, and had a negative antibody screen. He received two units of autologous blood during surgery. The postoperative hemoglobin was 11.3 g/dL (113 g/L). Four days after surgery, a wound infection developed, for which he received a high-dose second-generation cephalosporin. At that time, the hemoglobin was 9.5 g/dL (95 g/L), serum haptoglobin was 140 mg/dL (1400 mg/L), reticulocyte count was 5.5% of erythrocytes, and serum lactate dehydrogenase was 170 U/L. A repeated antibody screen was negative, and the direct antiglobulin test (DAT test) was weakly positive for IgG but not complement. Elution studies performed by the blood bank were nonreactive.

Which of the following is most likely explanation for this patient's serologic findings?

A. Cold autoantibody reaction
B. Warm autoantibody reaction
C. Drug-dependent antibody reaction
D. Transfusion-related alloantibody reaction

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Answers and Commentary

Case 1

Correct answer: D. Phenoxybenzamine therapy.

Surgical resection is the only cure for pheochromocytoma, and perioperative mortality may approach 4% due to comorbid conditions such as renal insufficiency and congestive heart failure. Blood pressure control should be initiated within 2 weeks before nonemergent surgery, using α-adrenergic antagonists. The goal of therapy is to reduce blood pressure to <140/90 mm Hg; however, many patients will be limited by orthostasis.

Phenoxybenzamine, 2 to 4 mg orally three times a day, is initiated and titrated every 48 to 72 h to blood pressure goals. Phenoxybenzamine is a noncompetitive α-blocker, and up to 100 mg/d may be required to achieve proper blood pressure goal. The drug minimizes hypertensive crisis during intubation, induction, and tumor manipulation, but its half-life of 24 h often contributes to postoperative hypotension. Doxazosin, another α-antagonist, has been occasionally substituted for phenoxybenzamine. Within the past decade, calcium channel blockers, such as nicardipine, have been employed with good results in place of α-blockade, but there is less experience with calcium channel blockade.

β-Adrenergic antagonists must never be administered before α-blockers. β-Blockade permits unopposed αagonist activity, causing hypertensive crisis. β-Blockers may be administered for heart rate control after α-blockers have effected meaningful blood pressure reduction.

Within the week before surgery, intravenous volume expansion with high sodium diet and intravenous saline may be initiated in the absence of congestive heart failure. Intraoperatively, nitroprusside, esmolol, and norepinephrine may variably be required for blood pressure control. Postoperatively, if blood pressure fails to normalize, the patient may be experiencing hypertensive glomerulosclerosis, underlying essential hypertension, or may be harboring a malignant pheochromocytoma with unsuspected metastases.

Fine-needle aspiration may precipitate a hypertensive crisis; the procedure is never performed if pheochromocytoma is suspected. Preoperative blood transfusion was formerly suggested, but current anesthesia management has made this maneuver unnecessary.

Key Points

  • The goal of preoperative blood pressure control in patients with pheochromocytoma is <140/90 mm Hg.
  • α-Adrenergic blockade is used to reduce preoperative blood pressure in patients with pheochromocytoma.

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Case 2

Correct answer: D. Pharmacologic stress nuclear study.

In this patient with diabetes, dyslipidemia, smoking, and hypertension, the Framingham 10-year likelihood of a cardiac event is 18%, compared to an average event rate of 5% for men of this age. In addition, diabetic patients frequently do not have angina despite the presence of ischemia (silent ischemia). This patient's electrocardiogram is consistent with left ventricular hypertrophy, based on an S wave in lead V2 plus an R wave in lead V6 >35 mV, left axis deviation, and lateral ST-T changes. Left atrial enlargement also is present. Because the transplant team would defer transplantation until after coronary revascularization if significant disease were present, further evaluation is needed. A pharmacologic stress nuclear study is an appropriate diagnostic approach that provides information on the presence and severity of coronary ischemia.

Exercise electrocardiographic stress testing would be less useful in this patient because his ability to exercise could be limited by peripheral neuropathy; in addition, the baseline electrocardiogram would likely show resting ST-segment changes due to left ventricular hypertrophy. Serum C-reactive protein levels are a marker of systemic inflammation, and population-based studies have demonstrated that elevated levels are associated with an increased risk of coronary disease. However, C-reactive protein levels are not helpful in detection of inducible ischemia in an individual patient.

Although a 24-hour electrocardiogram could show ST-segment changes in a patient with silent ischemia, this approach is less sensitive and specific than stress testing, and its value would be limited in this patient with an abnormal resting electrocardiogram. Coronary angiography provides definitive evaluation of coronary anatomy and would likely demonstrate coronary artery disease in this patient. However, most clinicians would perform a stress imaging study first, both for diagnosis and to target which vessel should be considered for revascularization if multiple lesions are present.

Key Points

  • The risk of coronary artery disease in diabetic patients is 2 to 4 times higher than in nondiabetic patients.
  • The pretest likelihood of disease should be calculated using available algorithms in patients with coronary risk factors.

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Case 3

Correct answer: D. Incentive spirometry.

The evidence is good that routine postoperative lung expansion (for example, incentive spirometry or deep-breathing exercises) prevents postoperative pulmonary complications. Based on current evidence, no modality is clearly superior to the other, but nasal continuous positive airway pressure may be particularly useful in patients who are not able to perform incentive spirometry. The evidence is insufficient to determine whether prophylactic corticosteroids or antibiotics prevent pneumonia.

Multiple trials have shown that routine intravenous or enteral hyperalimentation in malnourished patients does not prevent postoperative pulmonary complications except perhaps in the severely malnourished or in those expected to be without oral intake for an extended period (for example, 2 or 3 weeks). There is emerging evidence suggesting that enteral nutrition especially formulated to enhance the immune system may prevent postoperative infection.

Key Point

  • The evidence is good that routine postoperative lung expansion (for example, incentive spirometry or deep-breathing exercises) prevents postoperative pulmonary complications.

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Case 4

Correct answer: C. Intraoperative acute normovolemic hemodilution.

Intraoperative acute normovolemic hemodilution involves the aseptic removal and transferal of blood into anticoagulated storage bags just before surgery, while normovolemia is maintained during phlebotomy with intravenous fluids. This process is a suitable alternative to blood transfusion for this patient. With intraoperative acute normovolemic hemodilution, multiple units of blood may be withdrawn from the patient and stored in the operating room until they are needed. The number of units to be removed depends on the patient's preoperative hematocrit and the number of blood units expected to be lost during surgery. Usually, a minimum hematocrit threshold of 25% to 28% is maintained, depending on the patient's cardiovascular reserve. Normovolemic hemodilution assures that the patient receives fresh autologous blood that has a hematocrit higher than the blood lost during surgery. Hemodilution has none of the clerical risks associated with blood banking.

Eliminating automatic transfusion triggers can reduce the need for blood transfusion in many situations, aside from surgical procedures with substantial acute blood loss. This patient's anemia would make it difficult for him to donate sufficient autologous blood units before surgery. In addition, stored autologous blood units are subject to contamination, clerical error, and improper storage.

Administration of erythropoietin may improve this patient's anemia preoperatively but will not eliminate the need for blood replacement during surgery. Intraoperative cell salvage has many of the benefits of hemodilution but is not used during surgery for cancer because of the risk of contaminating the recovered blood with tumor cells, which can theoretically lead to hematogenous metastasis.

Key Point

  • Intraoperative acute normovolemic hemodilution ensures delivery of autologous blood with a hematocrit higher than the blood lost during surgery and has none of the clerical risks associated with blood banking.

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Case 5

Correct answer: D. No additional tests are needed.

This patient, who is scheduled to undergo laparoscopic cholecystectomy, has mildly elevated serum aminotransferase values. Although abnormal aminotransferase values typically occur in patients with choledocholithiasis (common bile duct stones), this patient has a normal common bile duct caliber. Her serum alkaline phosphatase and bilirubin values are also normal. The slightly abnormal laboratory values may therefore be due to fatty liver alone. In this setting, no additional preoperative tests are required, although the surgeon may elect to perform intraoperative cholangiography to identify any associated common bile duct stones that can be removed either at the time of surgery or postoperatively by endoscopic retrograde cholangiopancreatography (ERCP).

ERCP is indicated preoperatively when a patient is likely to have common bile duct stones that can be removed by therapeutic ERCP. Preoperative ERCP is most appropriate for patients with abnormal liver chemistry values greater than twice the upper limit of normal (including serum total bilirubin >3 mg/dL) associated with common bile duct dilatation or jaundice. Biliary scintigraphy (HIDA scan) that fails to visualize the gallbladder will confirm a suspected diagnosis of chronic cholecystitis but cannot diagnose common bile duct stones. Given the ultrasonographic findings, a CT scan of the abdomen is unlikely to provide any additional information.

Key Point

  • Preoperative endoscopic retrograde cholangiopancreatography is indicated prior to laparoscopic cholecystectomy only for patients with gallstones and possible concomitant common bile duct stones.

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Case 6

Correct answer: C. Drug-dependent antibody reaction.

This patient's antibody screen (indirect antiglobulin test) identifies serum antibodies capable of reacting with reagent red blood cells. The direct antiglobulin test (Coomb's direct test) identifies globulins already on the surface of the patient's erythrocytes. These serologic findings are indicative of a drug-dependent antibody in this patient. One of the most common mechanisms of drug-induced antibody, often producing a positive direct antiglobulin test, occurring with the use of cephalosporins, causes alteration of the erythrocyte membrane and results in nonspecific deposition of IgG and other serum proteins. This mechanism does not cause hemolysis nor complement activation. The serologic findings in this patient are indicative of a drug-dependent antibody.

Cold reactive autoantibodies are IgM antibodies and are not a cause of a positive IgG antibody test. Many cold autoantibodies are merely cold agglutinins and only react at room temperature or lower but can cause hemolysis if they react at temperatures closer to 37°C (98.6°F). In this case, the direct antibody test would be positive for complement but not IgG. Warm reactive autoantibodies are IgG antibodies and cause a positive direct antiglobulin test because IgG reacts with the red blood cells, and can occasionally cause complement activation. Warm autoantibodies that are recovered by elution from direct antiglobulin test–positive red blood cells will react with all cells tested rather than be nonreactive. Drug-dependent antibodies recovered in a eluate will only be detected if the drug is used in the test system.

This patient has never received donor blood and therefore has not been sensitized to develop alloantibodies against donor red blood cells. During a hemolytic transfusion reaction, the direct antibody test may be positive for IgG, but the antibody is present on the repeated antibody screen, and elution would show reactivity with antigen-positive cells. In the absence of hemolysis, the elevated reticulocyte count probably reflects this patient's response to surgical blood loss that was incompletely corrected by only two autologous units of blood. Other causes of the lower hemoglobin include ongoing bleeding and/or blood loss from continued phlebotomy for laboratory testing.

Key Point

  • Patients with a drug-induced antibody reaction do not have indications of hemolysis or evidence of complement activation on direct antibody testing.