ACES and RUSH: Resuscitation Ultrasound Protocols

Abdominal and cardiac evaluation with sonography in shock (ACES) and rapid ultrasound for shock and hypotension (RUSH) are point-of-care ultrasound (POCUS) examinations indicated in cases of nontraumatic, undifferentiated hypotension, or shock. In hypotension, early diagnosis and goal-directed therapy are essential for optimal outcomes and lead to decreased mortality. Both ACES and RUSH protocols examine the chest and abdominal cavities by ultrasound in order to rapidly evaluate for reversible causes of shock and improve an accurate diagnosis. Each of these protocols combines many of the same core ultrasound elements, differing mainly in the exam sequence.

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Overview

Background

  • History and physical exams often lack the necessary sensitivity and specificity to diagnose acute pathology accurately.
  • Ultrasound is being integrated early into resuscitation efforts for:
    • Speed
    • Ease of use
    • Cost
    • Availability
    • Good sensitivity and specificity 
  • For the care of critically ill cases, multiple resuscitation protocols have been recently developed for ultrasound including ACES and RUSH.
  • Bedside ultrasonography allows for rapid evaluation of reversible causes of shock and improves diagnosis accuracy in undifferentiated hypotension.

Basics of ultrasonography

  • Imaging:
    • Sonography is an imaging technique based on ultrasound (high-frequency, inaudible sound waves). 
    • In medical imaging, the sound waves have a frequency of 2–18 megahertz (MHz). 
    • Sonography equipment utilizes a transducer that acts as an emitter and receptor of sound waves and a central computer that processes the electrical signals to generate an image.
  • Terminology: 
    • Hyperechoic (e.g., surface of bone, urinary tract calculi, fat-containing lesions): a structure that produces a high-amplitude echo (lighter grays and white)
    • Hypoechoic (e.g., abscesses without gas, solid tumors without calcifications or fat): a structure that produces a low-amplitude echo (darker grays)
    • Anechoic (e.g., simple cysts): a structure that produces no echo at all (looks completely black)
    • Isoechoic: a structure that produces an echo of a very similar amplitude to its environment and is very difficult to distinguish
  • Probes:
    • Curvilinear or convex probe: 
      • “Abdominal probe”
      • 2–5 MHz (low frequency)
      • High penetration
      • Big footprint
      • Bad for movement
      • Uses: most internal organs, aorta, abdomen, lung, pleura, gynecology
    • Phased array probe:
      • “Cardiac probe”
      • 1–5 MHz (low frequency)
      • High penetration
      • Small footprint
      • Great for movement
      • Uses: cardiac, pleura
    • Linear probe:
      • “Vascular probe”
      • 6–13 MHz probe (high frequency)
      • Low penetration 
      • Big footprint
      • Uses: vascular, pleural, optic nerve, venous access

Abdominal and Cardiac Evaluation with Sonography in Shock (ACES)

Definition

Abdominal and cardiac evaluation with sonography in shock is a POCUS examination exam used in cases of nontraumatic undifferentiated hypotension performed in the ER.

Principles

  • The protocol consists of 6 windows including cardiac, peritoneal, pleural, inferior vena cava (IVC), and aortic views.
  • The goal is to shorten the time it takes to establish a diagnosis and deliver an early goal-directed therapy.
  • Indications:
    • Nontraumatic hypotension/shock
      • Hypovolemic 
      • Obstructive
      • Cardiogenic 
      • Distributive
    • Contraindications:
      • No absolute contraindications 
      • Should not delay resuscitation efforts

Protocol

  1. Cardiac view:
    • Transverse subxiphoid 4-chamber view
    • Evaluates cardiac function and pericardial effusion/tamponade
  2. IVC:
    • Longitudinal subxiphoid view 
    • Measurement of diameter and collapse index
  3. Screen of the abdominal aorta:
    • Sliding slightly left of midline from the diaphragm to its bifurcation
    • Look for abdominal aortic aneurism (AAA).
  4. Morison’s pouch (hepatorenal fossa) and ipsilateral lung base view:
    • Look for free peritoneal.
    • Look for pleural fluid.
  5. Splenorenal fossa and lung base view:
    • Look for free peritoneal.
    • Look for pleural fluid.
  6. Pelvic view:
    • Looking at bladder volume
    • Look for free pelvic fluid.
Abdominal and Cardiac Evaluation with Sonography in Shock protocol-01

Abdominal and cardiac evaluation with sonography in shock (ACES) protocol:
1: 1 or more cardiac views
2: Inferior vena cava view
3: Screen of the abdominal aorta
4: Right and 5: Left flank views for pleural and peritoneal fluid
6: Pelvic view for bladder size and free fluid

Image by Lecturio.
Table: ACES protocol: Possible findings in shock
Type of shockCardiacIVCAortaPeritoneal fluid/bloodPleural fluid/blood
SepticHyperdynamic LV or hypodynamic in late sepsisNarrow/collapsed IVCNormalSurgical/gynecological sepsisPneumonia, empyema
CardiogenicHypodynamic LV/↓ EFNormalNormalNormalNormal
HypovolemicHyperdynamic LVNarrow/collapsed IVCAAASpontaneous splenic rupture, perforated viscous, gynecological bleedingNormal
Obstructive (cardiac)Pericardial effusion, cardiac tamponadeVariable IVCNormalNormalNormal
Obstructive (pulmonary)Dilated RV, ↑ LV to RV ratioDilated IVCNormalNormalNormal
AAA: abdominal aortic aneurysm
IVC: inferior vena cava
LV: left ventricle
RV: right ventricle
EF: ejection fraction

Rapid Ultrasound for Shock and Hypotension (RUSH)

Definition

Rapid ultrasound for shock and hypotension is a POCUS examination protocol that focuses on assessment of the heart and major vessels that is divided into 3 steps: “pump,” “tank,” and “pipes.”

Principle

  • Free fluid within the peritoneal cavity will settle into dependent areas within the peritoneum when the patient is supine, which can be detected via ultrasound imaging.
  • An easily learned and quickly performed shock ultrasound protocol
  • The goal is to rapidly identify causes of shock and begin an early goal-directed therapy.
  • Indications:
    • Nontraumatic hypotension/shock
      • Hypovolemic 
      • Obstructive
      • Cardiogenic 
      • Distributive 
    • Contraindications:
      • No absolute contraindications 
      • Should not delay resuscitation efforts

Protocol

  1. Pump (cardiac view):
    • Question: Is the pump working?
    • Pericardium (pericardial effusion/tamponade)
    • Left ventricle (size and contractility status)
    • Relative size of the left ventricle to the right ventricle
  2. Tank (volume status):
    • Question: Is the tank full, leaking, or compromised?
    • Fullness of the tank: evaluation of the inferior cava and jugular veins for size and collapse with inspiration
    • Leakiness of the tank (blood loss, fluid extravasation, or other pathologic fluid collections): views of the hepatorenal, splenorenal fossae, and bladder to assess for intraperitoneal collections and pleural effusion
    • Tank compromise: assessments of both hemithoraces for pneumothorax 
    • Tank overload: assessments of both hemithoraces for pulmonary edema
  3. Pipes (arteries and veins):
    • Question: Are the pipes obstructed or blocked?
    • Systematic assessment of major arteries and veins for abnormalities:
      • Ruptured pipes: AAA, aortic dissection
      • Clogged pipes: deep vein thrombosis (DVT)
Probe placement for the RUSH exam-01

Probe placement for the rapid ultrasound for shock and hypotension (RUSH) exam

Image by Lecturio.
Table: RUSH protocol: Possible findings in shock
Type of shockPumpTankPipes
CardiogenicHypodynamic LV, ↓ EF, dilated heartDilated IVC, distended jugular veins, lung rockets, pleural fluid, peritoneal fluidNormal
HypovolemicHyperdynamic LV, small chamber sizeNarrow IVC, flat jugular veins, peritoneal fluid, pleural fluidNormal
ObstructiveHyperdynamic LV, pericardial effusion, cardiac tamponade, RV strain, cardiac thrombusDilated IVC, distended jugular veins, absent lung sliding (pneumothorax)DVT
DistributiveHyperdynamic LV in early sepsis, hypodynamic LV in late sepsisNormal/small IVC (early sepsis), peritoneal fluid (sepsis), pleural fluid (sepsis)Normal
AAA: abdominal aortic aneurysm
IVC: inferior vena cava
LV: left ventricle
RV: right ventricle
EF: ejection fraction
DVT: deep vein thrombosis

Clinical Relevance

  • Sonography: an imaging technique based on ultrasound (high-frequency, inaudible sound waves). In medical imaging, the sound waves have a frequency of 2–18 MHz. The equipment uses a transducer acting as the emitter and receptor of the sound waves and a central computer processing electrical signals to generate an image. The general advantages of this type of imaging is its low cost, availability, and safety. 
  • Hemopericardium (tamponade): the accumulation of excess fluid in the pericardial space around the heart that increases pressure restricting cardiac filling and results in decreased cardiac output. Symptoms include dyspnea, hypotension, muffled heart sounds, jugular venous distension, and pulsus paradoxus. Diagnosis is confirmed with echocardiography. Management is emergent pericardiocentesis or pericardiotomy.
  • Hemothorax: a collection of blood in the pleural cavity. Hemothorax most commonly occurs due to damage to the intercostal arteries. Patients present with shortness of breath, chest pain, hypotension, tachycardia, decreased lung sounds, and dullness on percussion of the chest. Diagnosis is by chest X-ray. Management is with tube thoracostomy drainage, video-assisted thoracoscopic surgery (VATS), or thoracotomy.
  • Pneumothorax: a life-threatening condition in which air collects in the pleural space, causing collapse of the lung. Patients present with chest pain, dyspnea, and diminished breath sounds. Diagnosis is made with imaging, though tension pneumothorax is a clinical diagnosis. Management is based on the size and stability of the patient and can include needle decompression and chest tube (thoracostomy) placement. 
  • Pleural effusion: the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Management is dependent on the underlying condition and whether the effusion is causing respiratory distress.

References

  1. Alpert E. A. (2019). The ABCDs of ResUS – Resuscitation Ultrasound. Cureus, 11(5), e4616.
  2. Atkinson, P. R., McAuley, D. J., Kendall, R. J., Abeyakoon, O., Reid, C. G., Connolly, J., & Lewis, D. (2009). Abdominal and Cardiac Evaluation with Sonography in Shock (ACES): an approach by emergency physicians for the use of ultrasound in patients with undifferentiated hypotension. Emergency medicine journal: EMJ, 26(2), 87–91. 
  3. Nicks B. A., & Gaillard J. P. (2020). Approach to nontraumatic shock. Tintinalli J. E., & Ma O, & Yealy D. M., & Meckler G. D., & Stapczynski J, & Cline D. M., & Thomas S. H. (Eds.), Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill.
  4. Cardiac ultrasound. Baston C. M., & Moore C, & Krebs E. A., & Dean A. J., & Panebianco N (Eds.), (2018). Pocket Guide to POCUS: Point-of-Care Tips for Point-of-Care Ultrasound. McGraw-Hill.
  5. Fritz D. A. (2017). Emergency bedside ultrasound. Stone C, & Humphries R. L. (Eds.), CURRENT Diagnosis & Treatment: Emergency Medicine, 8e. McGraw-Hill. 
  6. Perera, P., Mailhot, T., Riley, D., & Mandavia, D. (2010). The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically lll. Emergency medicine clinics of North America, 28(1), 29–vii.

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