Board Simulation in Critical Care Medicine
Aanchal Kapoor
Jorge A. Guzman
POINTS TO REMEMBER:
Acute Respiratory Distress Syndrome
The incidence of acute respiratory distress syndrome (ARDS) has been estimated in the range of 5 to 15 cases per 100,000 per year.
Transfusion-related acute lung injury (TRALI) is becoming an increasingly recognized cause of ARDS. TRALI should be suspected when symptoms of ARDS develop within 6 hours of transfusion of blood or blood products.
The objectives of mechanical ventilation in ARDS are not to normalize arterial blood gas values, but to provide adequate support for oxygenation and acid-base balance, while avoiding further injury that can be induced by mechanical ventilation.
The only ventilation strategy that has been demonstrated in randomized controlled trials to improve the mortality in ARDS is the use of low-stretch (6 cc/kg predicted body weight tidal volume) ventilation.
Current fluid management recommendations for patients in ARDS with adequate urine output and not in shock include use of diuretics as necessary to target CVP <4 mmHg or PAOP <8 mmHg.
Recent randomized controlled trials of the pulmonary artery catheter utilization in several populations, including ARDS, have failed to demonstrate improved outcomes.
Patients who survive ARDS tend to recover normal or near-normal lung function, although patients with severe ARDS are sometimes left with some degree of restrictive defect.
Despite return of lung function, many patients who survive ARDS have persistent functional disability and are not working 1-year post-ICU discharge.
Shock
Shock is defined as a physiological state characterized by inadequate tissue perfusion leading to decreased tissue oxygen delivery.
The most common causes of shock in the intensive care unit population may be grouped into several categories.
Hypovolemic shock—commonly due to hemorrhage, external volume loss (e.g., ketoacidosis), or third spacing (e.g., pancreatitis).
Cardiogenic shock—predominantly secondary to depressed myocardial function, mostly secondary to acute myocardial infarction, malignant dysrhythmias, acute valvular regurgitation, or nonischemic cardiomyopathies.
Distributive shock—characterized by loss of vascular tone; septic shock is most frequent; other causes include adrenal insufficiency, neurogenic shock, liver cirrhosis, overdoses, and anaphylaxis.
Early clinical and laboratory markers of compromised tissue perfusion include decreased urinary output, decreased skin perfusion, changes in mental status, elevated serum lactate levels, and increased heart and respiratory rate.
Central venous (ScvO2) or the mixed venous oxygen saturation (SvO2) can be very useful when assessing a patient in shock.Related posts:
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