SASSIA DONALDSON-MORGAN, MICHAEL YEE and LEWIS A. EISEN

Overview

Significant advancements have been made in the use of ultrasound technology since its inception in the early 1950s.¹ These advances have revolutionized the practice of critical care medicine. Currently, clinicians in the intensive care unit (ICU) have at their disposal a tool at the bedside that augments the physical examination and is safe, portable, noninvasive, and readily available.

Safety

Ultrasound technology uses sound waves, and through reflection, refraction, and attenuation of these ultrasound beams, image acquisition occurs, thus limiting the patient’s exposure to radiation, unlike chest radiography and computed tomography.^2,3 The lack of radiation exposure also allows multiple sites to be evaluated repeatedly with minimal risk to the patient (Chapter 1).

Immediate assessment of hemodynamically unstable patients is possible with the use of ultrasound, and the need for transportation with possible complications is reduced.

Availability

Ultrasound is available to intensivists 24 hours per day, 7 days per week. It is also under control of the primary provider of care, so it is readily accessible when needed to avoid delay in diagnosis and therapeutic intervention. Also, bedside ultrasound enables immediate reassessment of patients after therapeutic interventions to confirm appropriateness of the care instituted.

Time efficiency

Bedside ultrasound enables immediate integration between the clinical scenario that requires investigation and the operator. This allows a more focused, goal-directed evaluation of hemodynamically unstable patients with immediate interpretation of data and implementation of personalized therapy.⁴

On review of the literature, the time needed to obtain information during bedside ultrasound evaluation is very brief given the magnitude of information obtained during each evaluation (Table 59-1). Appropriate, focused examinations can be performed as part of routine practice on teaching rounds.

Critical care ultrasound is clinically useful

Goal-directed echocardiography enables qualitative assessment of left and right ventricular size and function, identification of pericardial effusion and evaluation for tamponade physiology, measurement of internal vena cava (IVC) diameter, and assessment of respiratory variation to determine preload responsiveness.^17,20,21 Critical care ultrasound (CCU) facilitates bedside detection of pleural fluid and pneumothorax and can be used to guide thoracocentesis for diagnostic-therapeutic purposes, as well as other invasive procedures (e.g., placement of thoracostomy tubes, paracentesis, abscess drainage). CCU guides arterial and central venous cannulation and facilitates the placement of peripherally inserted central catheters and hemodialysis catheters.²² CCU detects venous thrombosis¹⁴ and free intraperitoneal and pericardial fluid (focused assessment with sonography for trauma) and facilitates the evaluation of patients for acute renal dysfunction^23–25 and volume status.

Teaching tool

CCU can be used in conjunction with the physical examination to improve accuracy and clinical utility and enhance the teaching of various physiologic principles.²⁶ It can provide immediate feedback to confirm or refute the physical findings. For example, within a few minutes of using CCU the cause of life-threatening conditions triggering hypotension can be elucidated or excluded from the differential diagnosis. If a resident hears a typical murmur of mitral regurgitation on physical examination, this can be confirmed within minutes with bedside echocardiography. Immediate feedback enhances learning.

A typical day on intensive care rounds at montefiore hospital

The value of CCU can best be appreciated during routine patient care rounds. It would be ideal to perform focused ultrasound examinations during this time, when information is gathered and used to formulate management plans. A characteristic day in our 14-bed medical ICU is described next.

Bed 2. A morbidly obese 23-year-old woman with drug-induced liver failure and subsequent aplastic anemia was admitted to the ICU with neutropenic fever and septic shock secondary to gram-negative bacteremia. The patient is receiving appropriate broad-coverage antibiotics. She is febrile and hypotensive and requires increasing dosages of vasopressor support. Focused echocardiography is performed to evaluate left ventricular function (ruling out cardiogenic shock), the presence of pericardial effusion (ruling out cardiac tamponade), and evidence of right ventricular dilatation and strain (acute pulmonary embolism). The IVC is visualized to determine the diameter and presence of respiratory variation while on mechanical ventilation (intravascular hypovolemia). The examinations show that the heart is hyperdynamic and that significant respiratory variation suggestive of distributive shock is present. The patient is given a fluid bolus. In light of the new fever, all preexisting invasive catheters will be removed and replaced. Since this patient has underlying thrombocytopenia, the use of real-time ultrasonography to guide central venous catheter and arterial catheter placement will help achieve higher first-pass success and reduce complications.

Bed 3. A 47-year-old man with hepatitis C cirrhosis was admitted because of upper gastrointestinal hemorrhage secondary to esophageal varices. The patient is now undergoing evaluation for possible liver transplantation. The transplant surgeon believes that he is volume-overloaded, but the hepatologist believes that he is volume-depleted. Central venous pressure measured via his right internal jugular catheter is 6 mm Hg. Focused echocardiography and IVC analysis reveal normal cardiac function with an IVC diameter of 2.5 cm. The patient is not intravascularly depleted and will not benefit from further fluid administration.

Bed 5. A 63-year-old man with chronic obstructive lung disease was admitted for hypoxic respiratory failure secondary to multilobar pneumonia. The patient still requires support from the mechanical ventilator. A portable chest radiograph is obtained but interpretation is limited because of excessive soft tissue and poor technique. It is difficult to distinguish on a chest radiograph whether a pleural effusion, worsening infiltrates, or atelectasis is present. Lung ultrasound shows the presence of a moderate right pleural effusion, probably parapneumonic. A pigtail drainage catheter is placed at the bedside by the ICU team under direct ultrasound guidance, and 1 L of fluid was drained.

Bed 7. A 29-year-old man with mixed connective tissue disease (MCTD) was admitted for severe myositis and respiratory distress. The patient is taking corticosteroids, and generalized weakness developed during his ICU course. Arterial blood gas analysis now shows mild respiratory acidosis. Ultrasound is used to assess the patient’s diaphragm. No change in diaphragmatic thickness is noted during inspiration, which suggests diaphragmatic weakness or paralysis, in part attributable to the patient’s MCTD. In concert with the rheumatology service, a course of high-dose corticosteroids was started.

Bed 8. A 70-year-old man was admitted for chronic pancreatitis and lower gastrointestinal bleeding. The patient has a urinary Foley catheter in place and just 35 mL of urine drained over the past 2 hours. The nurse mentions that there was difficulty inserting the catheter. Ultrasound is used to visualize the bladder and confirm proper catheter placement. Assessment of the IVC showed significant respiratory variation. The patient is probably hypovolemic and is given a fluid bolus based on the ultrasound findings. Finally, his urinary output improves.

Bed 12. A 57-year-old woman with acute promyelocytic leukemia was admitted for hypoxemic respiratory failure that developed within hours after receiving a transfusion of red blood cells and plasma. A chest radiograph showed bilateral infiltrates consistent with cardiogenic pulmonary edema or acute respiratory distress syndrome (ARDS). Diuretics were ordered for the patient before coming to the ICU. CCU shows that the patient’s left ventricular function is normal and the IVC has significant respiratory variation. These findings suggest that ARDS has developed secondary to transfusion-related acute lung injury and that she does not have cardiogenic pulmonary edema. The order for diuretics was canceled.

Bed 13. An 83-year-old woman with monoclonal gammopathy of unknown significance was admitted to the ICU because of an acute change in mental status and hypoxia. She was initially hospitalized for cholecystitis, but her hospital course has been complicated by left tibial and fibular fractures after a fall. She is currently receiving a heparin infusion empirically. A bedside examination with compression ultrasonography is performed immediately on rounds, and a left common femoral venous thrombus is found. This finding supports the suspicion of pulmonary embolism. The patient will continue full anticoagulation.

Bed 14. A 77-year-old obese woman with chronic obstructive pulmonary disease was admitted because of hypercapnic respiratory failure. Her course is complicated by the development of new atrial fibrillation, for which she is now receiving a heparin infusion. Overnight, swelling developed in her left shoulder and the upper part of her chest, and a recent decrease in her hemoglobin level was documented. Bedside ultrasound examination of the swollen area shows a new fluid collection in the subcutaneous tissue over the left shoulder and chest. The findings suggest a probably expanding hematoma. The heparin infusion is stopped and surgery is consulted.

CCU-derived information augments the history and physical examination and can lead to significant changes in management plans. The use of CCU for diagnostic and therapeutic purposes should become an integral part of every critical care unit’s rounds.

Pearls and highlights

References