Focus on POCUS · Tutorial
A window-by-window walkthrough of the bedside ultrasound exam used in the NMCSN shock pathway. Where to put the probe, what you should see, what you are looking for, and the mistakes that catch people out. No prior ultrasound experience assumed.
You do not need to finish this tutorial — or the scan — before calling. POCUS sharpens a shock call. It is never a prerequisite for one.
Step 0
Five decisions, none of which take longer than the machine takes to boot.
Pick the probe. Phased array, roughly 3.5–5 MHz, for the heart, the IVC and the abdomen — the small footprint fits between ribs. Linear, roughly 7.5–10 MHz, for lung sliding and vascular access. A curved array is an acceptable substitute for the abdominal and IVC views but is awkward on the heart.
Choose the preset. Cardiac preset for cardiac windows. It is not cosmetic: cardiac presets flip the screen orientation marker to the right of the image, so the same probe rotation gives a different picture under an abdominal preset. If your images look mirrored, this is usually why.
Set depth first, gain second. Start deep enough to see the far pericardium, then reduce until the heart fills about two thirds of the screen. Gain up until blood pools look black and myocardium looks grey — not until everything looks bright.
Position the patient if you can. Left lateral decubitus brings the heart to the chest wall and rescues a poor parasternal window. Supine and flat is fine for subxiphoid. A patient who is too unstable to reposition is a patient you scan supine — do not delay care for a better image.
Know the question. You are not producing a formal echo report. You are answering one question at a time: is there fluid around the heart, does the left ventricle squeeze, is the right ventricle too big, is the IVC full or flat, are the lungs wet, is the aorta normal.
Orientation
Every probe has a raised ridge, groove or light on one side — the indicator. Whatever the indicator points at appears on the marked side of the screen. In the cardiac preset that marker sits on the right of the image; in abdominal and lung presets it sits on the left. Nearly every “my picture is backwards” problem is one of three things:
The apex points the wrong way, or the liver appears on the wrong side.
Dark vertical bands cut the image into slices.
No recognisable structure at any depth.
Novices sweep too fast and too far. Millimetres of translation and a few degrees of tilt change the whole picture.
The walkthrough
Work through them in sequence the first few times. Once the sequence is habit, take them in whatever order the patient in front of you allows.
If you get one window, get this one. It works in the patient who cannot be repositioned, it is the fastest route to tamponade, and it answers the two questions that change management most.
Probe position and orientation. Diagram, not to scale.
Phased array, cardiac preset, depth 18–22 cm to start.
Flat under the xiphoid process, almost lying on the abdomen. Press the probe into the skin and aim up toward the left shoulder, using the liver as your acoustic window.
Indicator to the patient’s left (screen-right in cardiac preset).
Liver nearest the probe, then all four chambers in one plane. The right ventricle is the chamber closest to you.
Pericardial tamponade. It is an obstructive, not a cardiogenic, mechanism — it needs drainage, not inotropes. Call the shock line anyway: this patient still needs the team, and tamponade is one of the findings that moves fastest when it is named early.
The single most information-dense cardiac window. Function, filling, the valves and the aorta in one image.
Probe position and orientation. Diagram, not to scale.
Phased array, cardiac preset, depth 14–18 cm.
Immediately left of the sternum, third or fourth interspace. Probe flat on the chest, aimed straight down at the heart.
Indicator toward the patient’s right shoulder.
Right ventricular outflow tract on top, then the LV in long axis with the mitral valve, the aortic valve and the aortic root; descending aorta as a dark circle behind.
It supports a primary pump problem — classic cardiogenic physiology. Under the NMCSN pathway the numbers alone already met the trigger; this window tells the shock team what they are walking into.
The cleanest look at the septum, which is where the right ventricle tells you it is in trouble.
Probe position and orientation. Diagram, not to scale.
Phased array, cardiac preset. Same window as long axis.
From the long-axis view, rotate the probe 90° clockwise without moving off the window. Tilt down toward the apex until you find the papillary muscles.
Indicator toward the patient’s left shoulder.
A doughnut — the LV in cross section with two papillary muscles — and the crescent-shaped RV wrapped around it.
Acute right heart strain, with pulmonary embolism high on the list. This is one of the findings the algorithm treats as mechanical — it does not make the shock non-cardiac, and it does not delay the call.
The best window for comparing the two ventricles side by side.
Probe position and orientation. Diagram, not to scale.
Phased array, cardiac preset, depth 16–20 cm.
At the point of maximal impulse, roughly the fifth interspace in the mid-clavicular line, aiming up toward the right shoulder. Left lateral decubitus positioning helps enormously here.
Indicator toward the patient’s left.
The apex at the top of the screen with all four chambers below it, LV on the screen-right in cardiac preset.
McConnell’s sign, suggestive of acute pulmonary embolism. Under the pathway this counts as POCUS supporting a cardiac cause — it belongs in the call, not in a delay.
It converts “should I give fluid?” from a guess into an argument.
Probe position and orientation. Diagram, not to scale.
Phased array or curved array, depth 14–18 cm.
Just below the xiphoid, slightly right of midline, oriented head to toe. Find the IVC where it enters the right atrium and measure about 2 cm downstream.
Indicator toward the patient’s head.
A long dark tube running through the liver into the right atrium, with hepatic veins draining into it.
Cardiogenic — wet and cold. High filling pressure, poor pump, pulmonary congestion. Giving fluid here makes the patient worse.
The lungs are where a failing left heart shows itself first, and where a fluid decision gets its sanity check.
Probe position and orientation. Diagram, not to scale.
Linear probe for sliding and B-lines; phased or curved array works for effusion.
Anterior chest at the second to fourth interspace, then the lateral chest in the mid-axillary line, then the posterolateral base. Probe perpendicular to the ribs so two ribs and the pleural line form a bat sign.
Indicator toward the patient’s head.
Two rib shadows with a bright pleural line between them, shimmering as the patient breathes.
No. Shock is frequently mixed, and POCUS cannot exclude a second process. It does tell you a cardiac contribution is present, which is what the shock team needs to hear.
It is the step that stops the pathway going down the wrong road.
Probe position and orientation. Diagram, not to scale.
Curved or phased array, depth 14–20 cm.
Transverse across the epigastrium, then sweep down to the umbilicus following the aorta. Then the standard FAST windows: right upper quadrant, left upper quadrant, pelvis.
Indicator to the patient’s right.
The aorta as a round, pulsatile, thick-walled vessel anterior to the vertebral body; the IVC beside it, thinner and compressible.
This is a surgical emergency and it goes to the surgical pathway. The point of scanning the pipes is exactly this: to find the shock that is not cardiogenic before anyone commits to a cardiogenic plan.
Integration
No single window decides anything. The pattern across the pump, the tank and the pipes is what points to a shock state — and the full four-state table lives on the main Focus on POCUS page. What follows is the shorthand.
| Pattern | Pump | Tank (IVC / lungs) | Leading hypothesis |
|---|---|---|---|
| Cold and wet | Poor squeeze, dilated LV | Plump IVC, bilateral B-lines | Cardiogenic |
| Cold and dry | Poor squeeze | Flat IVC, dry lungs | Cardiogenic with low filling — the one mistaken for hypovolaemia |
| Warm and dry | Hyperdynamic, small LV cavity | Flat, collapsing IVC | Distributive or hypovolaemic |
| Right-sided | Dilated RV, septal flattening | Plump IVC, clear lungs | PE, RV infarct or acute cor pulmonale |
| Obstructive | Effusion with chamber collapse | Plump IVC | Tamponade |
Four cautions worth memorising.
A normal-looking left ventricle does not exclude cardiogenic shock — RV-dominant failure, acute valvular rupture, ventricular septal defect and tachyarrhythmia all present with a preserved-looking LV.
Cold and dry is the pattern most often mistaken for simple hypovolaemia, and the one where fluid does the most harm.
A dilated right ventricle may be chronic. Thick RV walls point to chronic disease rather than an acute event.
POCUS sensitivity in distributive shock is only about 0.73. A scan that does not look cardiac has not ruled out a cardiac contribution.
What this means for activation
The NMCSN activation pathway asks two questions before the exclusions: are the numbers there, and is this cardiogenic? POCUS is one of two ways to answer the second question — a classic clinical picture is the other, and either one is enough. If you have no ultrasound, or the scan is inconclusive, the pathway still activates.
Nothing on this page should delay a call. If a patient is deteriorating in front of you, the scan can wait and the phone cannot.
Transfer line currently routes to Heart Hospital of New Mexico. UNM coming soon.
Practice
Short, deliberately incomplete, and written the way the information actually arrives. Decide before you open the answer.
The numbers already met the trigger — hypotension with a lactate over 2. POCUS supports a cardiac cause, so the second gate is satisfied. Ask the goals-of-care question, then call. Do not give a fluid bolus into a plump IVC with a failing ventricle.
This scan points away from the heart. Under the pathway that routes to the sepsis or other pathway rather than a shock call — which is the point of scanning at all. Resuscitate and treat the source. If the picture changes, or the patient stops responding as expected, come back through the pathway.
Send a venous lactate — it counts, and you should not wait for arterial. Meanwhile, the vasopressor requirement is already a trigger on its own. You do not have POCUS and you may not have a clear cause; the pathway has an answer for that, and it is call anyway. Concern from the bedside clinician is reason enough.
Keep going
This page will get you oriented. It will not get you competent — that takes a probe in your hand and someone experienced beside you. NMCSN runs hands-on sessions and can bring them to your unit.
