Clinical Case: Shortness of Breath in a Woman With Hypertension, Diabetes

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In the emergency department, the patient was found to be lethargic, with marked shortness of breath and oxygen saturations in the low 70s.
In the emergency department, the patient was found to be lethargic, with marked shortness of breath and oxygen saturations in the low 70s.

A 67-year-old woman with history of hypertension, insulin-dependent diabetes, and coronary artery disease presents to the emergency department shortly after being discharged from an outside hospital, where she was admitted for pyelonephritis complicated by cardiac arrest, according to her family.

After a week in the intensive care unit at the outside facility, she was transferred to a step-down unit and eventually discharged to a nursing facility. Little else is known about her care there. The family reports that her clinical status has been worsening since discharge. The nursing facility reported a history of congestive heart failure as communicated from the other hospital, but the family denies any hospitalizations for heart failure.

In the emergency department, the patient was found to be lethargic, with marked shortness of breath and oxygen saturations in the low 70s. Physical examination revealed a morbidly obese woman (body mass index 40) tachypnea (respiratory rate of 38), tachycardia with an irregular rhythm, bilateral rales, dry skin, and bilateral 3+ pitting edema.

She is using accessory muscles, and jugular venous distention is present. Mean arterial blood pressure is 65 mm Hg. Electrocardiogram shows multifocal atrial tachycardia. Chest radiograph shows bilateral alveolar infiltrates. Blood gas measures reveal severe hypoxemia with respiratory alkalosis and elevated alveolar-arterial oxygen gradient. Other laboratory results show markedly high leukocytosis and lactate levels.

She is intubated in the emergency department for hypoxemic respiratory failure and started on empiric antibiotics with vancomycin and piperacillin/tazobactam. Once stabilized, she is transferred to the intensive care unit, where she is further stabilized.

What is the next best diagnostic imaging test?

A. Computed tomographic pulmonary angiography

B. Bedside transthoracic echocardiography

C. Bedside transesophageal echocardiography

D. Ventilation perfusion scan

Answer: B. Bedside transthoracic echocardiography

This woman was hospitalized recently for pyelonephritis and now has sepsis and acute respiratory distress syndrome (ARDS). Pulmonary embolism is not suspected at this time and computed tomographic angiography or ventilation perfusion scan would not be the next step. However, given her history of heart failure and her clinical presentation, cardiogenic pulmonary edema caused by left heart failure should be ruled out before ARDS can be diagnosed, according to the Berlin definition.

ARDS is an inflammatory form of hypoxemic respiratory failure resulting in the loss of alveolar aeration.1 Despite some successful advances in treatment strategies, the overall mortality of ARDS still remains higher than 40%.2 

In this patient, transthoracic echocardiogram revealed normal left ventricular function but markedly reduced right ventricular dilatation and systolic failure. Acute cor pulmonale resulting in right heart failure can occur as a result of increased vasoconstriction and vascular remodeling of the pulmonary vasculature in individuals with ARDS.2 Acute cor pulmonale has been associated with 25% to 50% of cases of ARDS and is independently associated with increased in-hospital mortality as well as increased 28-day mortality.2 The risk for cor pulmonale is increased with higher peak end-expiratory pressures, partial pressure of carbon dioxide, and driving pressures.2

Reducing these factors by using lung protective ventilation and prone positioning has been shown to reduce mortality in patients with ARDS. Prone positioning in particular has been associated with the use of lower peak end-expiratory pressure and targeted plateau pressure, both of which ultimately decrease pulmonary artery pressure and improve right ventricular dilation and function.

Transesophageal echocardiography may be helpful in patients with poor echocardiographic windows because of obesity and mechanical ventilation, however, a transthoracic echocardiogram should be attempted first, given the invasive nature of the former technique.

References

  1. Ranieri VM, Rubenfeld GD, Thompson BT, et al; ARDS Definition Task Force. Acute respiratory distress syndrome: the Berlin definition. JAMA. 2012;307(23):2526-2533.
  2. Biswas A. Right heart failure in acute respiratory distress syndrome: an unappreciated albeit a potential target for intervention in the management of the disease. Indian J Crit Care Med. 2015;19(10):606-609.
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