Impact of Integrated Cardiopulmonary Ultrasound on Clinical Outcome of Shocked Patients in Intensive Care Unit

The diagnosis of shock is based on clinical, hemodynamic, and biochemical signs. It is manifested with systemic arterial hypotension with mean arterial pressure less than 70 mm Hg, with reflex tachycardia. Also, there are clinical signs of tissue hypoperfusion, including cutaneous hypoperfusion with cold clammy skin, renal hypoperfusion with resulting oliguria (urine output [UOP] \<0.5 ml/kg/h) and neurologic hypoperfusion with altered mental state. Tissue hypoperfusion leads to anaerobic tissue metabolism with hyperlactatemia (>1.5 mmol/L).

Assessment of hemodynamic status and lines of management of the acute circulatory shock remains a challenging issue in emergency medicine and critical care. As the use of invasive hemodynamic monitoring declines, bedside-focused ultrasound (US) has become a valuable tool in the evaluation and management of patients in shock.

Four types of shock exist, including hypovolemic, cardiogenic, distributive, and obstructive shock. Clinical assessment and classification of shock is extremely difficult in critically ill patients as there is sometimes an overlap between these types. Incorporation of bedside ultrasound in patients with undifferentiated shock allows for rapid evaluation of reversible causes of shock and improves accurate diagnosis in undifferentiated hypotension.

Currently, the critical care ultrasound (CCUS) has been widely advocated as the preferred tool to assess hemodynamics, including accurately estimating pathophysiological changes of shock. This information, therefore, can be carried out into protocols to guide shock treatment. However, despite previous recommendations, current protocols are subjective and empirical, without listing specific variables as indicators, such as ejection fraction (EF), mitral annular plane systolic excursion (MAPSE), tricuspid annular plane systolic excursion (TAPSE),mitral or tricuspid annular peak systolic velocity (S'-MV or S'-TV), inferior vena cava (IVC), and lung ultrasound score (LUSS).

CCUS examination on ICU admission which performed by the experienced physician provide valuable information to assist the caregivers in understanding the comprehensive outlook of the characteristics of hemodynamics and lung pathology. Those key variables obtained by CCUS predict the possible prognosis of patients, hence deserve more attention in clinical decision making.

Lung ultrasound has been widely used in diagnosing pulmonary diseases including pneumonia, connective tissue diseases and interstitial lung diseases. For patients in the intensive care unit (ICU), more attention is paid to monitoring the development of lung pathologic changes, which guides the therapy. Lung insults caused by inflammation, trauma or water increase always lead to infiltration, which results in the loss of lung air. Depending on the severity of the aeration loss and water increase, each part of the lung generates different ultrasound signs upon exam.

The lung ultrasound score (LUSS) is the sum of the scores of each exam zone and has been justified as a respectable semiquantitative score to measure the lung aeration loss caused by different lung pathologic changes, such as pneumonia, atelectasis, pleural effusion, and lung edema.

Lung Ultrasound Protocol (LUSS): Reliable techniques have been used based on the international evidence-based recommendations for point-of-care lung ultrasound that recommended using a complete eight-zone lung ultrasound examination to evaluate the LUSS. The anterior and lateral chest wall are divided into eight areas. Areas 1 and 2 denote the upper anterior and lower anterior chest areas, respectively, and areas 3 and 4 denote the upper lateral and basal lateral chest areas, respectively.