Point-of-care Ultrasound for Internists– Benefits and Limitations

Dan Schnobrich, MD Med-Peds Hospitalist

University of Minnesota November 2, 2012

After this presentation, participants will be able to:

• Describe Point-of-Care Ultrasound and distinguish how it differs from traditional uses

• Define current evidence and limitations for applications that might be of high interest for internists

• Articulate challenges regarding this disruptive innovation and the need of role of professional societies in and determining training and quality standards

Characteristics of ultrasound paradigms

3. Point-of-care: Limited (often dichotomous), goal-directed exams by the clinician at the point-of care to guide immediate management

1. Traditional: Images acquired by technologists, described and analyzed by specialists in detail often many hours later 2. Procedural

A common case • 65 year old man with 80 pk-yrs, CHF, moderate

COPD is admitted from ED with increasing dyspnea and a non-productive over the last 3 days. Slight PND. No increase in his baseline pedal edema. Mild improvement with albuterol.

• RR:26 HR:85, BP: 125/95. • -Trop, - D-dimer, BNP 1500 (nl 200-800) • CXR unremarkable (hyper expanded)? • EKG basically nl

• As you go to examine your patient, what findings

can help you?

An common case

• Exam reveals a man in mild-moderate respiratory distress, 1+ pedal edema, and crackles at his bases.

Brief parasternal short axis: normal squeeze

Inferior vena cava with nl size and variability with respiration

Lung ultrasound reveals A-lines throughout upper and lower lung fields (representative images shown)

Characteristics of point-of-care ultrasound

POSITIVES: • In many cases exceeds the standards of our physical exam • Can be performed in several minutes, comparable to traditional

physical exam • Involves personal contact between physician and patient at the

bedside. • Immediate, repeatable • Without any appreciated harms such as ionizing radiation • After initial equipment purchase and training time, virtually free. NEGATIVES: • Operator –dependent • High start up costs • Many limitations of technology compared to CT/ MRI

Many applications have been described

(Moore and Copel, NEJM, 2011)

• Today we’ll focus on applications which are relatively well-developed and may be of immediate interest

• We will limit ourselves to the literature from internal medicine, emergency medicine, and critical care

Inferior vena cava can help estimate

intravascular volume

• Our physical exam is often limited • Inferior vena cava influenced by volume status

– Often large and invariable with respiration when overloaded

– Often smaller collapsible with respiration when hypovolemic

Inferior vena cava can help estimate intravascular volume

TECHNICAL/ PHYSIOLOGY: • Changes with fluids given/ removed/ lost: -Closely tracks blood volume during ultrafiltration (Tetsuka1995; Katzarski 1997, Agarwal 2011)

-Blood donors, 1 of 2 studies -improves with treatment of shock (Yanagawa, 2005, Ferrada, 2012))

DIAGNOSTIC ACCUARCY: • Correlates moderately with Invasively Measured CVP (Brennan 2007; Stawicki

2009; Goonewardena 2010; ; Yildirimturk, 2011; De Lorenzo 2012; Uthoff 2012 ; Wiwatworapan 2012)

• Correlates with other markers: -dialysis complications ()

-expert status of volume (Carr, 2007)

AFFECTS MANAGEMENT:: • Predicts changes in Cardiac Index with fluid bolus (Barbiert, 2004, Feiseel 2004,

Machare-Delgado, 2011)

Cardiac: Contractility , Effusion

CONTRACTILITY: DIAGNOSTIC ACCUARCY: • Better estimates contractility than traditional physical exam (Kobal 2005; Martin 2007)

• Correlates moderately well with traditional Echo but falls short of that expected of cardiologists (DeCara 2003; Alexander 2004; Martin 2007; Kirpatrick 2008; Lucas 2009; Andersen 2011; Kimura 2011

MANAGEMENT CHANGES: • Medicine residents with limited training can detect EF< 40% with

sensitivity, specificity 94%, NPV: 88%, PPV: 97% In this setting this occurred 22 hours before echo results available (Razi, 2011)

PERICARDIAL EFFUSIONS: DIAGNOSTIC ACCUARCY: • Hospitalists’ sensitivity much better than their physical exam (0.07 to 0.79 (Martin, 2007)

• Moderate sensitivity (lowest 0.54) and specificity (0.68-0.99) compared with traditional Echo (Lucas 2009; DeCara 2003; Martin 2007; Alexander, 2004; Vignon 2007; Andersen 2011)

Cardiac:

MANAGEMENT CHANGES: • Useful in determing etiology of hypotension/

shock, finding cause in 50-80% (Vignon 1994, Jones 2004, Joseph 2004, Jones

2005)

• Influences plan fluid/ vasopressor management in 14- 50% of critically ill patients (Vignon 1994, Stanko 2005, Orme 2009,)

• Others noted changes of management in 16-37% (Hauser 1989, Jensen 2004, Manasia 2005)

Pulmonary: Comet tails and Interstitial Syndrome

COMET TAILS: Vertical, hyperechoic lines that obliterate A- lines, go to end of screen

These become dominant when

interstitial spaces become thickened (interstitial syndrome), which occurs in :

1. pulmonary edema 2. ARDS 3. Interstitial fibrosis 4. Pneumonias

Healthy lung (horizontal A-lines predominate)

Alveolar interstitial syndrome (vertical B-lines have replaced A-lines)

Pulmonary: Interstitial Syndrome

DIAGNOSTIC ACCUARCY: • Lung ultrasound appears superior to CXR for ruling in and

out significant interstitial syndrome (Kobal 2005; Martin 2007)

• Presence or absence of interstitial syndrome effectively differentiates cardiogenic vs. pulmonary etiologies of dyspnea

Study: yr: n: sensitivity specificity PPV NPV

Lichtenstein 1998 66 100 92

Cibinel 2012 80 94 84 88 92

Siva 2012 218 100 95 96 100

Sperandeo 2012 193 Unable to differentiate COPD and cardiogenic

Pulmonary: Pneumothorax

DIAGNOSTIC ACCUARCY: • Point-of-care Ultrasound is very accurate in the diagnosis of

pneumothorax

Study n Gold Standard Sensitivity Specifici: ty PPV NPV Licthenstein 111 CXR, CT 95 91 87 100 Lichtenstein 115 CXR, CT 100 96 89 100 Dulchavsky 382 CXR, CT 94 100 95 99

Blaivas 176 CT/ chest tube 98 99 98 99 Rowarn 27 CT 100 94 92 100 Soldati 109 CT 92 99 96 99

Adapted from Volpicelli et al, 2012

Pulmonary: Pleural Effusions

DIAGNOSTIC ACCURACY: • Point-of care Ultrasound superior to

physical diagnosis (Lichtensetein 2004, Patterson 2004)

• Detected with sonography at higher rate than CXR (Lichtenstein 1999, Kocijancic 2003, Lichtenstein 2004, Medford 2010)

Superficial abscesses

DIAGNOSTIC ACCURACY:

MANAGEMENT CHANGES: Iverson et al: (n: 65) changed management in 9/65 Jaovishidha: (n: 38): no correlation in mgmt chance. Referral population where most common indication for referral was to eval for necrotizing fasciitis. Squire: (n: 64), 17/18 patient where physician exam and US divergent success/ failure of I&D agreed with US.

SENSITIVITY SPECIFICITY n: Exam alone US Exam alone US Berger et. al 40 0.76 (0.5-0.89) 0.83 (0.36-0.99) 0.83 (0.36-0.89) 0.67 (0.24-.94) Iverson et. al 65 0.79 (0.71-0.84) 0.98 (0.90-0.99) 0.67 0.69 (0.58-0.73)

Squire et al. 64 0.86 (0.76-0.93) 0.98 (0.93-1.00) 0.70 (0.55-0.82) 0.90.88 (0.76-0.96)

Abdominal Aortic Aneursym

DIAGNOSTIC ACCURACY: Numerous, small studies show that various types of

providers can detect AAA with good sensitivity and specificity

Study n: Setting: Sens Spec Avg diff (mm) Bailey (2001) 80 Primary Care 100 100 Blois (2012) 45 Primary Care 100 100 2 Tayal (2003) 125 ED 100 98 Knaut (2005) 104 ED 4 Costantino (2005) 238 ED 94 100 4.4 Dent (2007) 120 ED 96 100 Moore (2008) 179 ED 3.9

Deep Venous Thrombosis

DIAGNOSTIC ACCURACY:

• Physician-performed compression

ultrasonography can be very sensitive and accurate for DVT.

• It appears to vary significantly from study to study

Study n S (%) SP (%) PPV (%) NPV (%) Blaivas 112 ED 100 97 (94-100) 94 (87-100) 100 Frazee 76 ED 88 (65-98) 75 (62-86) 53 (34-71) 95.7

Magazzini 399 ED 100 (96-100) 98 (97-98) 94 (89-93) 100 (99-100)

Jacob 121 ED 89 (51-99) 97 (92-99) Kline 183 ED 70 (50-86) 89 (83-94) 53 (36-69) 95 (91-98) Crisp 199 ED 100 (92-100) 99 (96-100) 98 (94-100) 100 Kory 128 CC 86 96 Torres-Macho 76 ED 92 (82-100) 98 (94-100) 96 (88-100) 96 (90-100)

Adapted from Torres- Macho et al.

Back to our case

Brief parasternal short axis: normal squeeze

Inferior vena cava with nl size and variability with respiration

Lung ultrasound reveals A-lines throughout upper and lower lung fields (representative image shown)

Some themes

• Literature is heterogenous by application. For some, just in technical and diagnostic accuracy. In other applications has moved on to decision making and patient outcomes research. (Hwang, 2011)

• There do appear to be numerous areas in which ultrasound offer us an opportunity to improve our physical exam

• There is great need to evaluate outcomes such as length of stay, missed diagnoses, etc.

“Disruptive innovation” • A radical, non-incremental, innovation that goes

on to disrupt an existing market/ framework and displace it in a way that is not expected in the field.

• Not surprisingly, many traditional imagers (e.g. radiologists and cardiologist), have voiced significant concern, noting that in many cases it did not meet the high standard that their fields have established.

• “That it will ever come into general use, notwithstanding its value, is extremely doubtful; because its beneficial application requires much time and gives a good bit of trouble both to the patient and the practitioner; because its hue and character are foreign and opposed to all our habits and associations.”

“Disruptive innovation”

• “That it will ever come into general use, notwithstanding its value, is extremely doubtful; because its beneficial application requires much time and gives a good bit of trouble both to the patient and the practitioner; because its hue and character are foreign and opposed to all our habits and associations.”

London Times, 1834

“Disruptive innovation”

1999: AMA resolution 802 • Acknowledged, “broad and diverse use of ultrasound,”

and that it is, “within the scope of practice of appropriately trained physicians.”

• Hospitals should grant privileges based upon, “recommended training and education standards developed by each physician's respective specialty society”

- specified training (didactic, bedside practice, apprenticing) - saving images, clear documentation, and performing QI/QA - staying within limitations of literature - oversight by specialty society

Response by Professional Societies:

• Emergency Physicians published thorough reviews of literature applicable to their uses, standards for training, and QI/QA, in in 2001

• Critical Care published 2008 • The American College of Physicians has not yet

developed these standards and policies.

• “In fact, within a decade of the publication of On Mediate Auscultation, popular sentiment in favor of the technique had become so strong that a physician who did not employ the stethoscope jeopardized his professional reputation. Some physicians who did not know how to auscultate patients took to carrying stethoscopes with them for display purposes”

(Reiser, 1979)

Risks of failing to adopt training and QI/QA standards:

Take home points

• Point-of-care Ultrasound is an emerging tool that can augment many areas of our physical exam

• The evidence surrounding this is heterogenous in quality, and there is little patient-outcome data

• There is significant need for standards in training and quality to ensure that this done in a way that benefits our patients.

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