Generalities -- Basic Notions -- The Ultrasound Equipment -- Specific Notions of Ultrasound in the Critically Ill -- General Ultrasound: Normal Patterns -- Organ by Organ Analysis -- Peritoneum -- Gastrointestinal Tract -- Liver -- Gallbladder -- Urinary Tract -- The Retroperitoneal Space -- Spleen, Adrenals, and Lymph Nodes -- Upper Extremity Central Veins -- Inferior Vena Cava -- Lower Extremity Veins -- Pleural Effusion and Introduction to the Lung Ultrasound Technique -- Pneumothorax and Introduction to Ultrasound Signs in the Lung -- Lung -- Lung Ultrasound Applications -- Mediastinum -- General Ultrasound of the Heart -- Head and Neck -- Soft Tissues -- Clinical Applications of Ultrasound -- Ultrasound in the Surgical Intensive Care Unit -- Ultrasound in Trauma -- Emergency Ultrasound Outside the Intensive Care Unit -- Interventional Ultrasound -- Emergency Ultrasound and Antibiotic Therapy -- Analytic Study of Frequent and/or Severe Situations -- Learning and Logistics of Emergency Ultrasound -- Ultrasound, a Tool for the Clinical Examination -- Concluding Remarks.