A 62-year-old man undergoes a partial pancreatectomy for exocrine pancreatic cancer. The surgery is complicated by excessive peripancreatic bleeding requiring careful surgical hemostasis. The patient receives packed red blood cell transfusion during the surgery as well as intravenous normal saline. He is transferred to the surgical intensive care unit for close monitoring and is successfully extubated. Twelve hours later, the nurse reports decreased oxygen saturation. The patient has received multiple doses of morphine for pain control since the surgery. Temperature is 37.5 C (99.5 F), blood pressure is 80/40 mm Hg, pulse is 112/min, and respirations are 28/min. The patient's pulse oximetry shows 87% on 4 L nasal cannula oxygen. Examination reveals bilateral basal crackles. The abdomen is mildly distended and tender, and bowel sounds are decreased. There is no rebound tenderness or rigidity. Pulmonary artery catheter readings show a cardiac index of 2 L/min/m² (normal, 2.8-4.2) and a pulmonary capillary wedge pressure of 20 mm Hg (normal, 6-15). Which of the following is the most likely etiology of this patient's current condition?

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11ec25c8_d8aa_02ac_bc81_5b2247d639bc_MD0003_00 This patient is most likely in cardiogenic shock due to an acute myocardial infarction (MI). Perioperative MI is common in patients undergoing noncardiac surgery; intraoperative hemorrhage requiring blood transfusion increases the risk (likely due to reduced oxygen delivery to the myocardium). Patients with perioperative MI often lack chest pain, possibly due to receipt of postoperative pain control (eg, morphine). Significant infarction of the left ventricle leads to impaired contractility and a decrease in left ventricular stroke volume. Cardiac index (CI), which is a measure of cardiac output (stroke volume × heart rate) adjusted per body surface area, is low as tachycardia cannot make up for the decrease in stroke volume. The increased pressure in the left ventricle is transmitted back to the left atrium and the lungs; therefore, pulmonary capillary wedge pressure (PCWP), which estimates left atrial pressure, is elevated. Patients experience dyspnea and hypoxemia due to pulmonary edema, and lung examination reveals bilateral crackles. Decreased cardiac output leads to hypotension, for which the body attempts to compensate by peripheral vasoconstriction and increased systemic vascular resistance. Low tissue perfusion signals the tissues to extract more oxygen from the blood, which decreases mixed venous oxygen saturation. Decreased cardiac output (Choice A) Acute pancreatitis can progress to systemic inflammatory response syndrome and lead to distributive shock. Pulmonary artery catheterization (PAC) reveals high CI and low PCWP. (Choice B) Hypotension due to adrenal crisis is caused by distributive shock and intravascular volume depletion. PAC reveals normal or high CI and normal or low PCWP. (Choice D) Obstructive shock due to pulmonary embolism may lead to a decrease in CI due to decreased delivery of blood through the pulmonary circulation (decreased left ventricular preload). PCWP is usually normal or low. Obstructive shock (Choice E) Retroperitoneal hemorrhage leads to intravascular volume depletion and hypovolemic shock. CI and PCWP are typically low. hypovolemic shock (Choice F) Transfusion-related acute lung injury (TRALI) refers to the development of fever, hypotension, and noncardiogenic pulmonary edema within 6 hours of blood product administration. Because left ventricular function is typically normal, PAC reveals normal or high CI and normal or low PCWP. Educational objective: Patients with perioperative myocardial infarction may lack chest pain and can develop cardiogenic shock due to left ventricular systolic dysfunction. Pulmonary artery catheterization reveals a low cardiac index and elevated pulmonary capillary wedge pressure. References: Characteristics and short-term prognosis of perioperative myocardial infarction in patients undergoing noncardiac surgery: a cohort study. (http://www.ncbi.nlm.nih.gov/pubmed/21502650) Association between major perioperative hemorrhage and stroke or Q-wave myocardial infarction. (http://www.ncbi.nlm.nih.gov/pubmed/22679143)

A 62-Year-Old Man Undergoes a Partial Pancreatectomy for Exocrine Pancreatic