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ASRA Pain Medicine Update

POCUS Spotlight: Rapid Ultrasound for Shock and Hypotension (RUSH) Protocol for the Perioperative Setting

Nov 8, 2026, 21:03 by Rachel Douglas, DO, Pablo Pérez d’Empaire, MD, FRCPC, FCCM, FASE, Andrés Saba Santiago, MD, Marcello Succi, MD, and Laura Girón Arango, MD

Cite as: Douglas R, Pérez d’Empaire P, Santiago AS, et al. POCUS spotlight: rapid ultrasound for shock and hypotension (RUSH) protocol for the perioperative setting. ASRA Pain Medicine News 2026;51. https://doi.org/10.52211/asra110126.009.

POCUS Spotlight

Introduction

Postoperative hypotension is correlated with a 2.5 times greater risk of myocardial injury and patient mortality, an increased risk of delirium and longer hospital length of stay.1,2 Identifying etiology quickly matters.2 The rapid ultrasound for shock and hypotension (RUSH) protocol has a high degree of accuracy in differentiating etiologies of shock in emergency and trauma settings.3 In the attached videos and accompanying article, we present an amended version of the RUSH protocol for the everyday anesthesiologist, with a focus on troubleshooting perioperative hypotension.

Indications

Assessing for etiology of perioperative hypotension and shock.

Acquisition

Protocol

The RUSH protocol uses the HI-MAP acronym to outline the exam sequence: heart, inferior vena cava (IVC), Morrison’s pouch, abdominal views/focused assessment with sonography in trauma (FAST), and pulmonary scanning.4 There are 10 views in total. We start with four cardiac views: parasternal long axis (PLAX), parasternal short axis (SAX), apical four-chamber (A4C), and subcostal four-chamber (SC4C). Then, the protocol includes the IVC, Morrison’s pouch in the left upper quadrant (LUQ), the splenorenal view in the right upper quadrant (RUQ), and bladder views in the suprapubic area. Finally, the protocol incorporates anterior pulmonary views. We adapted the original RUSH protocol by excluding the scan to assess for an abdominal aneurysm, as this is an uncommon finding in the perioperative setting, and instead added the SAX and SC4C views. These views are especially useful for anesthesiologists because the SAX view quickly assesses left ventricle (LV) contractility and patient volume status, and the SC4C is easy to acquire in supine, intubated patients.

Video 1. This educational video covers the sequence and image acquisition for the amended RUSH protocol using the HI-MAP sequence.

Patient Positioning/Preparation

The patient should be supine and can be rotated into a left tilt for the cardiac views.

Transducer Selection

To obtain the images, ideally use a phased-array probe for all views to improve efficiency, but you may change your probe selection for better resolution. The phased array is required for all the cardiac views. For abdominal views, you may use phased array and curvilinear probes, and for thoracic lung, you may use any probe. We suggest using the phased array probe when efficiency is important.

Interpretation and Medical Decision-Making:

We will use the HI-MAP algorithm (see Figure 1) to evaluate shock types: hypovolemic, distributive, obstructive, and cardiogenic (see Video 2).

Figure 1. This figure shows where to obtain each view for the HI-MAP algorithm: H = heart, I = IVC, M = Morrison’s pouch, A = abdominal, and P = pulmonary.
Video 2. This in-depth educational video explains how POCUS findings can help diagnose shock etiology in the perioperative setting.

POCUS Findings by Shock Etiology

Table 1. This table shows common POCUS findings in different types of shock. LV = left ventricle, IVC = inferior vena cava, FAST = focused assessment with sonography in trauma, LVOT = left ventricular outflow tract, SAM = systolic anterior motion of the anterior mitral valve leaflet, IVS = interventricular septum, RV = right ventricle)
SHOCK TYPEPOCUS FINDINGS BY ETIOLOGY
HypovolemicSmall LV cavity with preserved function, collapsible/ flat IVC, potential + FAST exam
DistributiveHyperdynamic LV function, possible dynamic left ventricular outflow tract (LVOT) obstruction, normal/ low potential lung pathology
Obstructive (all subtypes have enlarged IVC, +/- B lines)
  • Pneumothorax: lung point, absent lung sliding and lung pulse. *Lung point might not be identifiable in large pneumothorax with a significant tension component.
  • Tamponade: pericardial effusion with echo findings of tamponade
  • HOCM: hypertrophic IV septum, dynamic LVOT obstruction with systolic anterior motion (SAM)
  • PE: RV enlargement/dysfunction, McConnell’s sign, interventricular septum (IVS) flattening
CardiogenicLV dysfunction, regional wall motion abnormalities, valvular disease, normal or dilated IVC, possible lung B lines

Hypovolemic Shock

Hypovolemic shock is the most common type of shock encountered in the operating room.5 Hypovolemic shock results from a critical reduction in intravascular volume, initially compensated by increased vascular resistance but progressing to reduced cardiac output and hypotension. Common causes of hypovolemic shock encountered in the operating room include hemorrhagic and non-hemorrhagic causes. Overall, the heart and IVC POCUS exam has been shown to be reliable for ruling out or evaluating hypovolemic shock, with sensitivity and specificity of 95%.3

Heart: In hypovolemic shock, the left ventricular cavity often appears small, or you may see an underfilled left ventricle, with the cavity nearly collapsing at end-systole, commonly described as a “kissing ventricle.”6 This is best observed in the SAX view (see Figure 2). The heart may also be hyperdynamic, as further explained in our distributive shock section.

Figure 2. In hypovolemic shock, a “kissing ventricle,” appreciated by thickening and collapsing ventricles in the SAX view, indicates volume reduction.

IVC: The IVC is often small and may show pronounced collapsibility in spontaneously breathing patients (see Figure 3), indicating volume responsiveness.7

Figure 3. IVC collapse to less than 50% during normal respiration indicates reduced intravascular volume.

Morrison’s Pouch and Abdomen: If there is an intra-abdominal bleed in the peritoneum, you will likely observe free fluid in dependent areas, including Morrison’s pouch (see Figure 4), above the spleen (peri-splenic space), and behind the bladder.

Figure 4. Fluid in Morrison’s pouch may suggest intra-abdominal bleeding as the cause of hypovolemic shock.

Pulmonary: Pulmonary findings are usually minimal.

Distributive Shock

In distributive shock, the principal pathophysiological mechanisms are peripheral vasodilation, a lack of volume response, and tissue hypoxia, resulting in relative hypovolemia and, consequently, hypotension.8 Multiple etiologies can cause distributive shock: sepsis, anaphylaxis, neurogenic shock, adrenal insufficiency, high block level after spinal anesthesia, pancreatitis, and toxicities. It is the most common overall cause of shock among patients presenting to the hospital, accounting for more than half of shock cases.9

Heart: Although left ventricular contractility can be normal in some cases, the most common finding in distributive shock is a hyperdynamic heart.10 A hyperdynamic heart refers to how the heart contracts, not necessarily its contraction rate. It is characterized by vigorous (hypercontractile) wall motion and a low end-systolic volume, with an ejection fraction greater than 70%. This finding can be challenging to differentiate from hypovolemia. However, in hypovolemia, both end-systolic and end-diastolic volumes are smaller, whereas in distributive shock, only the end-systolic volume is smaller.11 In advanced POCUS, you can consider using the left ventricular outflow tract velocity-time integral (LVOT VTI) to help differentiate, with LVOT VTI potentially lower in hypovolemic shock.12 This was discussed in a recent POCUS Spotlight article in this newsletter.13 In the surgical setting, you may have a mixed hypovolemic and distributive shock etiology. In this situation, ultrasound can help you assess whether the heart appears empty vs. hyperdynamic and guide vasopressor therapy versus intravascular volume resuscitation. In sepsis, you may also see sepsis-induced cardiomyopathy, which presents with a moderately dilated LV and reduced ejection fraction (EF) and is often reversible with recovery within 7-10 days after the onset of sepsis.14

IVC: In distributive shock, the IVC usually looks small and collapsible. However, it may also be dilated if there is an obstructive pathology, ie, pericardial effusion.11

Morrison’s Pouch and Abdomen: In distributive shock, there shouldn’t be any appreciable abdominal pathology on ultrasound. However, when interrogating the lower thoracic cavities, you may see pulmonary findings.

Pulmonary: If the lungs have an infectious septic etiology, you may see pathology such as pleural effusion (see Figure 5), exudate, empyema, or B lines, among other findings. In early sepsis, anaphylaxis, or a high spinal, you would expect the lungs to appear normal.15

Figure 5. A positive spine sign is when you can see vertebral shadows in the thoracic cavity, indicating a pleural effusion, which may be present in distributive shock.

Obstructive Shock

In the perioperative setting, obstructive shock is mostly caused by tension pneumothorax, cardiac tamponade, left ventricular outflow tract obstruction, or acute pulmonary embolism. All these conditions impair cardiac filling or outflow, thereby reducing effective cardiac output. In brief, during the HI-MAP sequence, you will see unique cardiac findings and a distended IVC, while Morrison’s pouch and other abdominal findings are normal. The pulmonary findings may vary based on the etiology.

Pneumothorax

A tension pneumothorax is a life-threatening emergency in which air enters the pleural space, causing mediastinal shift and obstructing venous return.

In pneumothorax, lung ultrasound may reveal findings consistent with a pneumothorax, such as absent lung sliding, absent lung pulse, and the presence of a lung point (see Figure 6).16 However, even though the lung point is pathognomonic and 100% specific for a pneumothorax,17 it won’t be found in a large tension pneumothorax. As noted in the Lichenstein paper where the lung point was first described, a lung point may be absent in a large pneumothorax where the lung is fully collapsed.18 Also of note, lack of lung sliding is not specific to pneumothorax and may also occur with lung bullae, pleurodesis, mainstem intubation, or lung collapse. A recent POCUS Spotlight article in the newsletter described lung findings in pneumothorax.19

Figure 6. A lung point is pathognomonic for a pneumothorax.

Theoretically, in a tension pneumothorax, air compresses the heart and obstructs your view of it. But if you could see the heart, you would see evidence of an underfilled, hyperdynamic heart.

Cardiac Tamponade

Cardiac tamponade is primarily a clinical diagnosis that often presents with exertional dyspnea, hemodynamic instability, and distended neck veins with minimal respiratory variation, but classic physical findings occur in fewer than 40% of confirmed cases.20 Ultrasound is therefore valuable for confirming the diagnosis, with pericardial fluid appearing as an anechoic collection within the pericardial sac (see Figure 7); up to 50 mL of pericardial fluid can be physiologic, so assessment should include at least two cardiac views. In the PLAX view, fluid posterior to the aorta suggests a pleural effusion, whereas fluid anterior to the aorta indicates a pericardial effusion.

Additional sonographic features suggestive of cardiac tamponade include right atrial and right ventricular systolic collapse and a heart that may appear to swing within a large pericardial effusion. Right atrial collapse is the earliest ultrasound sign of cardiac tamponade. This is because the increased pericardial pressure impairs right aorta filling when the chamber pressure is lowest.6

Figure 7A. Hyperechoic fluid collection anterior to the descending aorta indicates a pericardial effusion.

Hypertrophic Obstructive Cardiomyopathy

Obstructive shock may also result from dynamic left ventricular outflow tract obstruction, which in the perioperative setting could be associated with hypertrophic obstructive cardiomyopathy (HOCM).21 Typical findings of HOCM include a small, hyperdynamic LV with asymmetric septal hypertrophy, causing near-complete or partial obliteration of the ventricular cavities, and characteristic systolic anterior motion of the mitral valve, partially obstructing the LVOT during systole (see Figure 8).

Figure 8. This image shows increased interventricular septum size and obstruction of the left ventricular outflow tract by the anterior leaflet of the mitral valve. IVS = interventricular septum, LVOT = left ventricular outflow tract

Pulmonary Embolism

When a pulmonary embolus (PE) is present, three main useful signs may be seen on cardiac ultrasound: right ventricular dilation, septal flattening, and McConnell’s sign. RV dilatation, with the right ventricle exceeding approximately 60% of the left ventricular size, is the most common sign during PE (see Figure 9).22 The most specific echocardiographic finding associated with pulmonary embolism is the McConnell’s sign, characterized by akinesis of the right ventricular free wall with preserved apical contraction of both ventricles. Despite its high specificity, McConnell’s sign can be seen in other conditions, such as right ventricular infarction, so clinical correlation is necessary.23 Flattening of the interventricular septum or a D-shaped left ventricle is considered an indirect marker of RV strain (Figure 10).22

Figure 9. In pulmonary embolism, right ventricular dilation, as shown above, is the most common ultrasound finding.
Figure 10. Flattening of the interventricular septum is a common ultrasound finding in pulmonary embolism.

Bone Cement Implantation Syndrome (BCIS) is a perioperative pulmonary embolic phenomenon characterized by a “shower” of hyperechoic emboli during cemented orthopedic procedures such as arthroplasties.24 During cementation, the exothermic expansion of acrylic polymers elevates intramedullary pressure, driving medullary fat, marrow, bone debris, thrombi, and possibly cement into the venous circulation. This can precipitate acute pulmonary hypertension and right ventricular dysfunction, producing hypoxemia, hypotension, and in severe cases, cardiac arrest.25 Notably, a study reported high intra- and interobserver reliability in identifying embolic phenomena during hip arthroplasty using a severity rating scale based solely on the IVC view.26

Figure 11. Showering of microemboli within the right side of the heart occurs in the setting of bone implantation syndrome.

Cardiogenic shock

Cardiogenic shock in the perioperative setting results from intrinsic cardiac dysfunction leading to a critical reduction in cardiac output despite adequate intravascular volume.6

Heart: When investigating cardiac function, you should assess four features with each view:

  1. global left ventricular systolic function
  2. regional wall motion abnormalities
  3. right vs left-sided involvement
  4. valvular function

If the global ventricular systolic function is reduced, you may see a left ventricle that is moderately dilated, not contracting well, and although there is some excursion of the mitral valve, it may not touch the interventricular septum (see Figure 12).6

Figure 12. This figure demonstrates a dilated left ventricle and an anterior mitral valve leaflet that is not approximating the interventricular septum during end diastole, suggesting poor function.

To assess regional wall motion abnormalities, the cohesive contraction of cardiac walls is often best appreciated in the PSAX view. When assessing the right versus the left heart function, the A4C and SC4C are great views for comparing all four chambers. These views, as well as the PLAX, are also good for assessing valvular function.27

IVC: The IVC may appear full.

Morrison’s Pouch and Abdomen: In Morrison’s pouch and the abdomen, you wouldn’t expect much change in the abdomen itself. However, in advanced POCUS, you may be able to assess volume congestion in the kidneys and liver.

Pulmonary: You may also see evidence of a pleural effusion or increased B lines.

The RUSH HI-MAP protocol is well-researched and has been shown to be a definitive method for quickly assessing perioperative hypotension in the emergency department setting. In this article, we amended the HI-MAP protocol to help anesthesiologists quickly discern etiologies of perioperative hypotension and shock states.

Rachel Douglas, DO, is a staff anesthesiologist and assistant professor in the department of anesthesiology and pain management at the Humber River Hospital at the University of Toronto in Canada.
Pablo Pérez d’Empaire, MD, FRCPC, FCCM, FASE, is director of the Perioperative POCUS Fellowship Program, a staff anesthesiologist, and an assistant professor in the department of anesthesiology and pain medicine at the Sunnybrook Health Sciences Centre at the University of Toronto in Canada.
Andrés Saba Santiago, MD, is a POCUS fellow in the department of anesthesiology and pain medicine at Toronto Western Hospital at the University of Toronto in Canada.
Marcello Succi, MD, is a POCUS fellow in the department of anesthesiology and pain medicine at the Toronto Western Hospital at the University of Toronto in Canada.
Laura Girón Arango, MD, is a staff anesthesiologist in the department of anesthesiology and pain medicine at Toronto Western Hospital at the University of Toronto in Canada.

References

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