A 92-year-old man presented with iron-deficiency anemia. Upon evaluation, guaiac-positive stools were found and follow-up colonoscopy revealed an invasive adenocarcinoma of the cecum. He was scheduled for a laparoscopic right hemicolectomy. Preoperative stress echocardiogram revealed no significant cardiac dysfunction. Immediately before surgery, sequential compression devices were placed on his legs to reduce the risk for venous thromboembolic disease. Following his uncomplicated operation, pulse oximetry showed oxygen desaturation requiring supplemental oxygen. The patient developed paroxysmal tachycardia on the third postoperative day. He had no chest pain or mental status alteration. On physical examination, his pulse was 130/min and irregularly irregular, blood pressure was 126/59 mm Hg, and breath sounds were diminished in bibasilar lung fields. The abdomen was soft and laparoscopy port sites were clean and free of erythema, blood, or exudate. A bedside 12-lead electrocardiogram showed atrial fibrillation with rapid ventricular response and no ST-segment elevation. Portable chest x-ray showed pulmonary edema. Laboratory values are shown in the Table.
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Box Section Ref ID
The patient is in congestive heart failure and needs a loop diuretic.
The patient is in congestive heart failure and should have a pulmonary artery catheter placed.
The patient has a pulmonary embolus and needs computed tomography angiography of the chest.
The patient has symptomatic anemia and needs 2 units of packed red blood cells transfused.
A. The patient is in congestive heart failure and needs a loop diuretic
Serum b-type natriuretic peptide (BNP) levels are commonly used to predict systolic dysfunction in congestive heart failure. BNP is a peptide with diuretic and vasodilatory effects, secreted by cardiomyocytes in response to intraventricular volume increases.1,2 BNP levels may be used to estimate left ventricular end-diastolic volume when pulmonary artery catheterization and bedside echocardiography are unavailable. Among patients with systolic failure, BNP levels greater than 100 pg/mL correlate with pulmonary capillary wedge pressure (PCWP) greater than 15 mm Hg with a sensitivity of 57% to 74%.1,2 BNP does not correlate with pulmonary capillary wedge pressure in patients with normal systolic function who have conditions such as pulmonary embolism, septic shock, acute respiratory distress syndrome, or acute renal failure.3- 5
BNP levels may predict postoperative morbidity. Elevated BNP predicted cardiac morbidity after major vascular operations.6 Serial postoperative BNP levels parallel net fluid balance with an increase and gradual decline, an effect amplified in patients with poor cardiovascular compliance.7 The Medicare midpoint reimbursement for a BNP assay is $63.8 Measuring BNP level is a cost-effective alternative to invasive procedures and imaging modalities for assessment of postoperative fluid volume status.
This patient’s tachyarrhythmia is the most immediate concern. A bedside 12-lead electrocardiogram is necessary to exclude acute ischemia and unstable rhythms. In this setting, the cause of paroxysmal atrial fibrillation should be investigated. Supraventricular tachycardia in elderly postoperative patients commonly occurs from electrolyte disturbances, volume overload, myocardial infarction, and atrial fibrillation.9 An echocardiogram, serial serum troponin levels, and a ventilation-perfusion scan were ordered to evaluate the possibility of myocardial infarction or pulmonary embolism.
This patient’s BNP level is elevated, reflecting stretch of ventricular cardiomyocytes. The elevated BNP level, positive fluid balance, pulmonary edema, and persistent supplemental oxygen requirement suggest the patient has volume overload and would benefit from loop diuretics. Although the patient experienced some hypoxia, given the high likelihood for congestive heart failure, administration of diuretics is indicated. If the patient did not improve after diuresis and remained hypoxic, evaluation for a pulmonary embolus by computed tomography angiography would be reasonable. Transfusion when the patient has volume overload is not indicated and should be reconsidered after the diuretics are given and the hemoglobin level remeasured.
A single postoperative BNP level may not be a reliable indicator of volume status. Because this patient’s atrial fibrillation and renal insufficiency may contribute to elevated baseline BNP, preoperative and serial BNP levels may have provided more independently accurate information about the extent of his hypervolemia. Congestive heart failure can also be diagnosed by pulmonary artery catheter placement or by echocardiography.
Other low-cost, noninvasive assessments of volume overload include daily weight measurement and portable chest radiography, which may show evidence of fluid overload. Low diastolic filling volume and respiratory variation of inferior vena cava diameter can be visualized with bedside echocardiography.10 Clinicians may also consider pulmonary artery catheterization and measurement of pulmonary capillary wedge pressure, which estimates left ventricular end-diastolic volume in the absence of pulmonary hypertension or valvular disease.
This patient was successfully treated with diuretics. Ventilation-perfusion scan showed no segmental perfusion defect, and echocardiogram showed no ventricular dyskinesis. On the fifth postoperative day, the patient was discharged to home in good condition. At his outpatient visit 2 weeks later, he remained free of complications.
Oliguria and tachycardia suggest inadequate intravascular fluid volume.
Dyspnea and polyuria suggest fluid overload. These are attenuated by age, nutritional status, general anesthesia, and major surgery.7,9
Elderly patients often have several comorbid conditions and reduced glomerular filtration rates that, in combination with postoperative inflammation, may mask fluid shifts between intravascular and extravascular compartments.9
Serially elevated BNP levels suggest excessive intravascular fluid volume that may be explained by intravenous fluid administration or by physiologic fluid shifts.
When the BNP level is less than 100 pg/mL, hypervolemia is unlikely.
Corresponding Author: Justin P. Wagner, MD, Department of Surgery, David Geffen School of Medicine of UCLA, 10833 Le Conte Ave 72-235 CHS, Los Angeles, CA 90095 (firstname.lastname@example.org).
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
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