Point of Care Ultrasound

Point of Care Ultrasound
For Rural Emergency Prepared by Shane Barclay MD

Goals and Objectives Learn basic terminology and settings on the ultrasound machine. Learn the techniques for: substernal cardiac for detecting pericardial effusion aortic scanning for AAA detecting free fluid in the abdomen detecting fluid or air in the chest cavity detecting fluid in the lung detecting pneumonia

Why these scans? They form most of the basis of the eFAST exam. These are technically some of the harder scans to perform. Therefore ‘everything’ after this is easy!

What the student needs to learn
Sight recognition Muscle memory First looking at a CXR Will ‘hold your hand’

EDE eFAST RUSH POCUS

EDE: “Emergency Department Echo” Developed by Dr
EDE: “Emergency Department Echo” Developed by Dr. Ray Wiss EDE 1, IP certification, EDE 2, EDE 3

eFAST: Extended Focused Assessment for Shock Trauma Extended Focused Assessment with Sonography for Trauma

RUSH: Rapid Ultrasound for Shock and Hypotension

Types of ultrasound teaching
POCUS – Point of Care Ultrasound Is the general descriptor for Physicians using ‘bed side ultrasound’.

Before you start scanning patients
Demographics on the patient. Know how to enter. If at all possible save your images. Tell the patient what you are going to do and what you are NOT going to do. You are not doing a ‘formal ultrasound’.

Now for the boring part!

Terminology Ultrasound produces sound waves that either pass through tissues, or if the tissue is ‘solid’, reflect back to the probe, which in turn ‘makes an image’. As the waves pass through tissue, they lose energy, called attenuation. The energy lost is converted into heat.

Terminology Depth Gain Echogenic Echolucent Hyperechoic Hypoechoic Frequency /penetration/resolution Modes of Transmission Artifact types

Terminology Depth This is the depth, in centimeters, the probe will generate an image, from the skin into the body cavity or organ.

Terminology Gain This allows you to change the ‘strength’ of the signal being returned to the probe. Increasing gain makes the image ‘brighter’. Decreasing gain makes the image ‘darker’.

Terminology Echogenic Tissues that ‘reflect’ back waves (ie bone) will produce an ‘echo’ which on the screen will appear ‘white’. Echogenic structures are white.

Terminology Echolucent Structures that don’t reflect back waves, or allow the waves to pass through them, such as fluid, are called ‘Echolucent’. We like echolucent structures to use as an ‘acoustic window’.

Terminology Echolucent Acoustic ‘windows’ can be: gel between the probe and skin, fluid (urine filled bladder) or solid (structures like the liver)

Terminology Hyperechoic Refers to structures that ‘produce more waves’ (ie are more solid) and will therefore appear more ‘white’. Often used interchangeably with ‘Echogenic’.

Terminology Hypoechoic Refers to structures that ‘produce less echo waves’ therefore are ‘darker’. Often used interchangeably with ‘echolucent’.

Terminology Frequency /penetration/resolution Ultrasound probes have different frequencies – range 2.0 – 5.0 MHz. Frequency is what determines the degree and depth of penetration as well as resolution of ultrasound waves.

Terminology Frequency /penetration/resolution Frequency and penetration are inversely related: Higher frequency – lower (shallow) penetration Lower frequency – higher (deeper) penetration Higher frequency – higher resolution Lower frequency – lower resolution

Terminology Probes (Transducers) Most eFAST can be done using a ‘curved array’ probe. These are low frequency which allows for deeper penetration, but at the expense of resolution.

Curved – low frequency, good penetration but lower resolution
Curved – low frequency, good penetration but lower resolution. Used for abdomen and eFAST Linear – high freq. shallow but good resolution. For superficial structures. Phased – high freq, shallow penetration, good resolution. Mainly for cardiac.

By any other name! Transvaginal Endocavity

By any other name! Do not start using this on a 15 year old male with suspected peritonsillar abscess and call it a ‘transvaginal ultrasound probe’! Call it an ‘endo-cavity probe’.

Terminology ‘Mode’ (Mode of Transmission) B – Brightness. Most common use. M – Motion. D – Doppler. Can be color Doppler or pulsed wave.

Terminology Artifact - any structure in an ultrasound image that does not have a corresponding anatomic tissue structure Refraction or Edge artifact Shadowing artifact Reverberation or ring down artifact Comet tail artifact Mirror (image) artifact Anisotropy Slide Lobe artifact

Terminology 1. Refraction or Edge artifact – shadow like image when u/s waves are passing by a small walled or large curved structure (ie bladder)

Refraction or edge artifact

Terminology 2. Shadowing artifact – appearance of ‘blackness’ behind solid structures – ie shadow behind bone or stone.

Shadowing artifact

Terminology 3. Reverberation or Ring down artifact – highly reflective interfaces which cause waves to reflect multiple times back to the probe superimposing images on the monitor (i.e. pleura)

Ring down artifact These lines are often called “A” lines.

Terminology 4. Comet Tail artifact – hyperechoic reverberation artifacts arising from the pleural line and spreading down toward the lower edge of the screen and are most frequently normal findings. In the lung when several comet tail artifacts (or B lines) are present they are often called ‘lung rockets’.

Comet tail artifact or lung rockets

Terminology 5. Mirror image artifact – another form of reverberation artifact, occurring when reflective surfaces return multiple echoes back to the probe.

Mirror image artifact Kidney Actual liver ‘Mirror’ image of the liver
Here the liver appears to be on the chest cavity side of the diaphragm (bright white line).

Terminology 6. Anisotropy – when u/s waves hit tendons, nerves or ligaments at 90 degrees, they can appear very dark or Echolucent (look like fluid)

Anisotropy artifact

Terminology 7. Side Lobe artifact – u/s beams from the edge of the probe are weak and when they hit a highly reflective object an echo returns to the probe which can be misinterpreted as an object from the center of the probe.

Side lobe artifact Red arrow shows air filled bowel. Red dots show side lobe artifacts of the bowel image

Enough Terminology !

The knobs you need to know
Initially there are only 2 knobs on the ultrasound machine you need to know Depth Gain (‘brightness’)

POCUS scans Aortic scanning Abdomen – free fluid
Cardiac substernal Aortic scanning Abdomen – free fluid Pleural view - for detecting fluid in the chest cavity

Cardiac substernal Aortic scanning Abdomen – free fluid Pleural view - for detecting fluid in the chest cavity Pneumothorax Interstitial lung fluid Pneumonia

Cardiac – substernal/subxiphoid
There are 3 views of the heart – Substernal, Parasternal Long (PSL) and Apical 4 chamber. We will only consider the substernal view for now. It is intended to look for 2 things. Pericardial effusion Cardiac standstill.

Cardiac – substernal/subxiphoid
It is intended to look for 2 things. Pericardial effusion Cardiac standstill. However can also be used to detect: 3. Right Ventricular dilation – massive PE, CHF 4. Ventricular contractility.

Cardiac – substernal TECHNIQUE: For ALL POCUS scans, remember the pneumonic for starting: “DOG” Depth (set to maximum to ensure seeing the structure you want) Orientation (the probe indicator is to the patient’s right or towards their head – there are exceptions you will learn later on) Gel (use lots! – if your image starts to look blurry, always think of adding more gel)

Cardiac – substernal TECHNIQUE: Used a curved array probe. Set depth to maximum (24-28 cm) Start with the probe completely flat on the abdomen, indicator to patient’s right side. Start just above the umbilicus. Slowly slide up towards the sternum, watching for ‘beating’. Identify the pericardium – should be able to see the Right Ventricle and the Septum (“7” sign)

Cardiac – substernal TECHNIQUE: Remember the most ‘dependent’ part of the heart will be under the right ventricle, which will appear at the ‘top’ (near field) of the screen. Slowly sweep the pericardium ‘down’ to view for any effusion.

Cardiac – substernal

“Echo” – substernal Orientation? Cardiology/Radiology echos will appear with different orientation – it’s a long story!

Pericardial Effusion Pericardium normally can contain around 50 cc fluid. Not visible with ultrasound. PCE will be evident on ultrasound with: ~ 100 mls posterior only in systole ~ mls posterior, throughout cardiac cycle ~ > 300 mls anterior and posterior PCE do NOT change shape during systole. Most patients can accommodate up to 200 mls before hemodynamic compromise begins to occur.

Pericardial Effusion Pitfalls in PCE scanning: Some patients have a layer of epicardial fat (not related to body habitus) which can be Echolucent and appear ONLY anteriorly. PCE will appear posteriorly first and never only anteriorly. As you sweep down then, an epicardial fat layer will disappear, whereas a PCE will get bigger.

Pericardial Effusion Effusion
Note: the effusion is at the ‘top’ of the screen, which doesn’t seem like the most dependent part. You need to be aware of the orientation of the probe and patient.

Pericardial Effusion

Pericardial Effusion Effusion

Pericardial Effusion Following are two short (2 minute) videos on cardiac scanning. Note: They use a cardiac probe, not a curved array. And on the second video they use a ‘echo’ orientation, ie the probe indicator is to the patient’s left.

Aortic scan for AAA Technique: DOG: Depth, Orientation, Gel Place line of gel from xyphoid to umbilicus. Using curved array probe, place with indicator to patients right, transversely and perpendicular to abdomen. Start right against the xyphoid sternum.

Aortic scan for AAA This image actually shows a cardiac probe, but the rest is correct for an aortic scan. Note 4-5th finger stabilizing probe on the abdomen.

Aortic scan for AAA Landmarks and Identifying the Aorta - First landmark is the Thoracic spine. - Aorta is located immediately anterior to the spine and usually slightly to the patient’s left. - The IVC is usually located to the right of the Aorta. - Aortic wall is thicker than the IVC and is usually round, whereas the IVC can be teardrop, curved etc. - Aorta is non compressible like the IVC. - IVC will collapse with inspiration. (sniff test)

Aortic scan for AAA

Pancreas Splenic vein SMA IVC Aorta Left Renal vein

Aortic scan for AAA

Aortic scan for AAA This structure is the SMA and if visualized, you know you are cephalad enough to start an aortic scan.

Aortic scan for AAA What is a ‘Positive AAA scan’? Any part of the aorta that is greater than 3 cm in AP diameter, measuring from the outside wall of the aorta. This, in a patient who presents with abdominal pain and a clinical picture consistent with a possible ruptured AAA.

Aortic scan for AAA Once landmarks and the Aorta are identified, take note of the depth markers on the machine. In ‘your mind’ mark ‘3 cm’ distance.

Aortic scan for AAA

Aortic scan for AAA Once identified, take note of the depth markers on the machine. In ‘your mind’ mark ‘3 cm’ distance. Then slowly make your way down the aorta, keeping it centered and visible at all times. If you loose sight of the aorta, go up until you see it again. You can try compression of the abdomen to ‘push’ bowel out of the way. Or ask the patient to take in a breath and hold. These 2 techniques will often, but not always, allow you to visualize the aorta.

Aortic scan for AAA AAA POCUS will be one of the most common scans that will be ‘indeterminate’ – unable to visualize the whole aorta. If you are unable to visualize the WHOLE aorta, from xiphoid to iliac bifurcation, the scan is ‘indeterminate’.

Aortic scan for AAA However, if you see an area of the aorta that is greater than 3 cm in AP measurement, that is a ‘positive’ scan. Do not continue to scan. Stop. Call the radiologist and vascular surgeon. You can then go back and scan for size etc.

AAA – what is wrong here? Measure AP not transversely.

AAA This is the lumen of the aorta. Blue arrow is thrombus in the AAA.
Red arrow is the thoracic spine

Aortic scan for AAA Aortic ultrasound is ~ 100% sensitive and 98% specific for aneurysm. However you may not be able to diagnose a rupture as ¾ of aneurysms rupture into the retroperitoneum. An Aorta > 3 cm is considered positive. Measure the outer edge anterior to posterior.

Aortic scan for AAA Iliac arteries: When doing aortic scan you go until you see the bifurcation of the iliac arteries. Continue for another 2 cm or so. An iliac artery > 1.5 cm diameter is considered an aneurysm.

Abdominal Scan for Free fluid
80 % of significant bleeds will be detected in the RUQ (Morison’s pouch) – so always start there. Blood and fluid from the pelvis, abdomen and LUQ will all drain eventually into the RUQ. Early splenic injury will be detected in the LUQ. You can increase yield by putting patient in Trendelenburg (if they can tolerate it)

Abdominal Scan - RUQ RUQ: ‘DOG’ Place probe in longitudinal plane with marker towards patient’s head, at the level of the xyphoid in the posterior axillary line. Start with the probe ‘on the stretcher’. Slide probe anterior and posterior (‘up and down’) to find the liver/renal interface. Then slide probe in longitudinal plane to find interface. Sweep.

Abdominal Scan - RUQ

Abdominal Scan In the RUQ blood will initially track between the caudal tip of the liver and Gerota’s fascia of the kidney – Morison’s pouch. You must visualize the caudal tip of the liver. (Remembering your anatomy, it goes from Gerota’s fascia, perinephric fat, renal capsule and then the renal parenchyma)

Abdominal Scan -RUQ Perinephric fat Gerota’s Fascia

Abdominal Scan - RUQ Free Fluid

Abdominal Scan - LUQ The LUQ is a harder scan because the spleen and Lt kidney are higher up in the abdomen, the spleen is more mobile and smaller. Free fluid here will often accumulate between the spleen and diaphragm. The most dependent point of the LUQ is the subdiaghragmatic space and not the splenic/renal interface. Therefore essential to visualize the diaphragm (6-9 o’clock position)

Abdominal Scan - LUQ Diaphragm “6-9 o’clock”

LUQ Scan - positive Spleen Free Fluid Diaphragm Kidney

Pelvic Scan You want to visualize the rectovesical pouch in men and the rectouterine pouch (Pouch of Douglas) in women. A single transverse sweep is usually sufficient if the bladder is full enough. The edge of the bladder is the area where free fluid will be seen. Ultrasound can usually identify blood over mls.

Female Pelvic Scan - Positive

Female Pelvic Scan - Positive
Look for the ‘Mickey Mouse’ Sign

Male Pelvic Scan

Pelvic Scan If you see free fluid in the pelvis, always scan the RUQ as well.

pleural effusion Use a curved array probe in the same position as looking for free fluid in the abdomen. Visualize the diaphragm - (‘6 – 9 o’clock’ position) Usually cephalad to the diaphragm you will see ‘liver’ or ‘spleen’ due to “mirror image artifact”. Often the diaphragm can be hard to visualize. If it is clearly seen suspect an effusion.

Normal view RUQ Normal lung that looks like ‘liver’ due to mirror image artifact.

Normal LUQ view Normal lung that looks like ‘spleen’ due to mirror image artifact.

pleural effusion Ultrasound can detect as little as 50 cc fluid (by contrast, a CXR needs between cc ml before you will see blunting of the costophrenic angle on a PA CXR) On Ultrasound look for ‘black fluid’ cephalad to the diaphragm.

pleural effusion An effusion will appear as ‘black’ above the diaphragm. As the effusion grows, the lung will appear as a ‘solid organ’ as it collapses and will often ‘float or wave’ in the pleural fluid with respiration. As a general rule, separation of the visceral pleura from the parietal fluid indicates a 3 cm effusion, consistent with about 500 ml fluid.

Right pleural effusion
Collapsed lung Free pleural fluid

Left pleural effusion

Pneumothorax Sensitivity of POCUS for pneumothorax is around 86 – 98% versus 35 – 75% for CXR. In trauma patients CXR is much less sensitive than POCUS. Up to 35% of pneumos are missed by CXR in trauma patients, because they are small, the patient is lying supine and thus the pneumothorax will be superior in the chest cavity and not seen on x-ray.

Pneumothorax Use a linear array probe at the 4 – 6th interspace in the mid clavicular line. A curved array probe can be used, especially if you can set the frequency high (ie 5MHz) Locate 2 ribs. The area of interest is the pleural line between the 2 ribs.

Pneumothorax ‘Pleural line’ from Ring down artifact.
Sometimes called ‘A’ lines.

Pneumothorax What to look for and what is a Positive Scan
Lung Sliding. Comet tail and lung rockets. M mode. Lung Point.

Pneumothorax 1. Lung Sliding Look for ‘lung sliding’. This is motion on the pleural line that is often described as ‘ants crawling on a line’. Absence of lung sliding indicates a pneumothorax.

Pneumothorax 2. Comet tails and lung rockets These are often normal findings, especially comet tails (reverberation artifact) Presence of comet tails or lung rockets excludes a pneumothorax. (more on lung rockets with Interstitial fluid)

Comet tail artifact

Lung rockets

Lung rockets – ‘b’ lines
A few lung rockets (1 - 2) can be normal. More than 3 can indicate interstitial fluid (ie Congestive Heart Failure) More on interstitial fluid in subsequent slides!

Pneumothorax 3. M Mode With the probe held steady on the chest, press ‘M’ for M mode (motion mode). A normal lung will have horizontal lines (waves) in the near field (correlate to the chest wall) and hazy or ‘sand’ appearance in the far field (lung). This is often referred to as the ‘seashore sign’. Waves coming in to the sandy beach.

Pneumothorax 3. M Mode In a pneumothorax, there will be a ‘barcode’ sign, with the waves coming but NO sandy beach, just more horizontal lines.

Pneumothorax Pleura

Pneumothorax 4. Lung Point. This is where the lung separates from the chest wall ie the edge of the pneumothorax. This is 100% specific, but only about 65% sensitive for a pneumo. False positive lung point can be the heart or liver edge – so beware. As well, a lung point will NOT be seen in a complete collapsed lung.

Pneumothorax 4. Lung Point. If you find a pneumo, look for the lung point by going step by step down the lateral chest wall until it is found. If the lung point is in the mid to posterior axillary line, this will usually indicate a pneumothorax large enough to require a chest tube. (If this is a trauma and your are air medivacing the patient, they ALL require a chest tube!)

Pneumothorax

Pneumothorax - video

Pneumothorax

Subcutaneous emphysema
If subcutaneous emphysema is present no need to look for or confirm a pneumothorax. If you are having difficulty seeing the ribs and pleural line, it can indicate subcutaneous emphysema as the air in the tissue will scatter the ultrasound beam.

Pitfalls in Pneumothorax
Cardiac and Liver lung point. These can look like a lung points. Best to find the cardiac and liver edge first then go cephalad to look for lung sliding and other findings of a pneumothorax. Absent lung sliding – can be seen with ARDS, pulmonary contusion, fibrosis, COPD and pleural adhesions. As well, POCUS has reduced accuracy after 24 hours post pneumothorax due to adhesions.

Interstitial lung fluid
In a normal lung you will see ‘A’ lines, which are horizontal lines from ring down artifact of the pleura. With interstitial fluid or consolidation there will not be A lines. Comet tails (reverberation artifact) are normal : 1 – 3 per rib interspace. Lung Rockets are defined when 4+ B lines are evident. This indicates interstitial lung fluid. (97% sensitive, 95% specific) Multiple Lung Rockets can coalesce and appear as a ‘white curtain’.

Interstitial lung fluid
Multiple lung rockets is most commonly CHF, but can also be seen with ARDS and pneumonia. Pneumonia can often look like a ‘solid organ’ in the chest cavity.

Pneumonia CXR versus Ultrasound Sensitivity Specificity CXR 64% 90%
Am J. Emerg. Med, May 2015 Sensitivity Specificity CXR 64% 90% U/S % % Plus U/S cheaper, safer and more convenient

Pneumonia In pneumonia, fluid (inflammatory and pus) fill the alveoli. In early pneumonia, the fluid filled alveoli are surrounded by air filled lung, and B lines often result. Once consolidation occurs, the fluid filled lung will appear solid. Appearance is like the liver (called hepatization)

Pneumonia Hepatization refers to the lung appearance of white (hyperechoic) specs and branching lines. These are air bronchograms made up of air and fluid trapped in the bronchi. With imaging, you may see ‘dynamic air bronchograms’ which appear as white ‘bubbles’ moving within the bronchi.

Pneumonia

Dynamic air bronchograms
With real time imaging, you may see ‘dynamic air bronchograms’ which appear as white ‘bubbles’ moving within the bronchi.

Dynamic air bronchograms

Pneumonia Irregular consolidation – ‘shred sign’ With lobar consolidation, the borders of the consolidation will be well defined. With irregular consolidation the border between consolidation and aerated lung is irregular, known as ‘shred sign’

Pneumonia

Pneumonia vs atelectasis
Can be difficult to distinguish. History and exam can help. Atelectasis will also result in solid, non aerated lung like pneumonia. Pneumonia – lung remains the same size. Often see dynamic air bronchograms. Atelectasis – lung is reduced in size. No dynamic air bronchograms. Often have related effusion.

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Point of Care Ultrasound

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