Point-of-Care Ultrasonography for Primary Care Physicians and General Internists Anjali Bhagra, MBBS; David M. Tierney, MD; Hiroshi Sekiguchi, MD; and Nilam J. Soni, MD, MSc Abstract Point-of-care ultrasonography (POCUS) is a safe and rapidly evolving diagnostic modality that is now utilized by health care professionals from nearly all specialties. Technological advances have improved the portability of equipment, enabling ultrasound imaging to be executed at the bedside and thereby allowing internists to make timely diagnoses and perform ultrasound-guided procedures. We reviewed the liter- ature on the POCUS applications most relevant to the practice of internal medicine. The use of POCUS can immediately narrow differential diagnoses by building on the clinical information revealed by the tradi- tional physical examination and refining clinical decision making for further management. We describe 2 common patient scenarios (heart failure and sepsis) to highlight the impact of POCUS performed by internists on efficiency, diagnostic accuracy, resource utilization, and radiation exposure. Using POCUS to guide procedures has been found to reduce procedure-related complications, along with costs and lengths of stay associated with these complications. Despite several undisputed advantages of POCUS, barriers to implementation must be considered. Most importantly, the utility of POCUS depends on the experience and skills of the operator, which are affected by the availability of training and the cost of ultrasound devices. Additional system barriers include availability of templates for documentation, electronic storage for image archiving, and policies and procedures for quality assurance and billing. Integration of POCUS into the practice of internal medicine is an inevitable change that will empower internists to improve the care of their patients at the bedside. ª 2016 Mayo Foundation for Medical Education and Research n Mayo Clin Proc. 2016;91(12):1811-1827 P oint-of-care ultrasonography (POCUS) is a safe and rapidly evolving diagnostic modality. Traditionally, ultrasonogra- phy has been used by imaging specialists, such as radiologists and cardiologists; however, it is now utilized by health care professionals from nearly all specialties. Technological ad- vances have improved portability and minia- turization of equipment, allowing ultrasound imaging at the bedside to make timely diagno- ses and guide procedures. Over the past several years, there has been emerging interest in the routine use of POCUS to potentially expedite and provide cost-efficient, high-value care. 1 This technology has been touted as the “vi- sual stethoscope” of the 21st century. 2,3 The stethoscope, developed 200 years ago, is the classic icon for the traditional diagnostic phys- ical examination and is still the most widely used tool to examine patients at the bedside. It is interesting to note, however, that the stethoscope is truly a “stethophone” because it allows only listening to the human body (steth ¼ chest, phone ¼ sound), rather than truly looking inside the body (scope ¼ to look in). However, as true “scopes,” portable ultrasound devices can generate high-quality images revealing the structure and function of organs. 4 The traditional bedside physical examination has been on the decline within internal medicine for several years for various reasons. 5-9 This increase in ambiguity in diag- nosis is potentially unsettling to internal med- icine physicians who see a variety of complex presentations and want to “do no harm.” Globally, medical education still emphasizes teaching traditional physical examination; however, no patient outcomes data justify application of physical examination tech- niques learned for commonly encountered clinical conditions. As an example, little data exist regarding an evaluation of central venous pressure using jugular venous distention in a morbidly obese patient. Moreover, many From the Division of General Internal Medicine (A.B.) and Division of Pul- monary and Critical Care Medicine (H.S.), Depart- ment of Medicine, Mayo Clinic, Rochester, MN; Abbott Northwestern Hospital, Medical Educa- tion Department, Minne- apolis, MN (D.M.T.); and Section of Hospital Medi- cine, South Texas Veter- ans Health Care System and Division of Pulmonary Diseases and Critical Care Medicine, University of Texas Health Science Center, San Antonio, TX (N.J.S.). REVIEW Mayo Clin Proc. n December 2016;91(12):1811-1827 n http://dx.doi.org/10.1016/j.mayocp.2016.08.023 www.mayoclinicproceedings.org n ª 2016 Mayo Foundation for Medical Education and Research 1811
Transcript
REVIEW
Point-of-Care Ultrasonography for Primary CarePhysicians and General Internists
Anjali Bhagra, MBBS; David M. Tierney, MD; Hiroshi Sekiguchi, MD;and Nilam J. Soni, MD, MSc
Abstract
Point-of-care ultrasonography (POCUS) is a safe and rapidly evolving diagnostic modality that is nowutilized by health care professionals from nearly all specialties. Technological advances have improved theportability of equipment, enabling ultrasound imaging to be executed at the bedside and thereby allowinginternists to make timely diagnoses and perform ultrasound-guided procedures. We reviewed the liter-ature on the POCUS applications most relevant to the practice of internal medicine. The use of POCUS canimmediately narrow differential diagnoses by building on the clinical information revealed by the tradi-tional physical examination and refining clinical decision making for further management. We describe 2common patient scenarios (heart failure and sepsis) to highlight the impact of POCUS performed byinternists on efficiency, diagnostic accuracy, resource utilization, and radiation exposure. Using POCUS toguide procedures has been found to reduce procedure-related complications, along with costs and lengthsof stay associated with these complications. Despite several undisputed advantages of POCUS, barriers toimplementation must be considered. Most importantly, the utility of POCUS depends on the experienceand skills of the operator, which are affected by the availability of training and the cost of ultrasounddevices. Additional system barriers include availability of templates for documentation, electronic storagefor image archiving, and policies and procedures for quality assurance and billing. Integration of POCUSinto the practice of internal medicine is an inevitable change that will empower internists to improve thecare of their patients at the bedside.
ª 2016 Mayo Foundation for Medical Education and Research n Mayo Clin Proc. 2016;91(12):1811-1827
From the Division ofGeneral Internal Medicine(A.B.) and Division of Pul-monary and Critical CareMedicine (H.S.), Depart-ment of Medicine, MayoClinic, Rochester, MN;Abbott NorthwesternHospital, Medical Educa-tion Department, Minne-apolis, MN (D.M.T.); andSection of Hospital Medi-cine, South Texas Veter-ans Health Care Systemand Division of PulmonaryDiseases and Critical CareMedicine, University ofTexas Health ScienceCenter, San Antonio, TX(N.J.S.).
P oint-of-care ultrasonography (POCUS)is a safe and rapidly evolving diagnosticmodality. Traditionally, ultrasonogra-
phy has been used by imaging specialists,such as radiologists and cardiologists; however,it is now utilized by health care professionalsfrom nearly all specialties. Technological ad-vances have improved portability and minia-turization of equipment, allowing ultrasoundimaging at the bedside to make timely diagno-ses and guide procedures. Over the past severalyears, there has been emerging interest in theroutine use of POCUS to potentially expediteand provide cost-efficient, high-value care.1
This technology has been touted as the “vi-sual stethoscope” of the 21st century.2,3 Thestethoscope, developed 200 years ago, is theclassic icon for the traditional diagnostic phys-ical examination and is still the most widelyused tool to examine patients at the bedside.It is interesting to note, however, that thestethoscope is truly a “stethophone” because
Mayo Clin Proc. n December 2016;91(12):1811-1827 n http://dx.dowww.mayoclinicproceedings.org n ª 2016 Mayo Foundation for M
it allows only listening to the human body(steth ¼ chest, phone ¼ sound), rather thantruly looking inside the body (scope ¼ tolook in). However, as true “scopes,” portableultrasound devices can generate high-qualityimages revealing the structure and functionof organs.4 The traditional bedside physicalexamination has been on the decline withininternal medicine for several years for variousreasons.5-9 This increase in ambiguity in diag-nosis is potentially unsettling to internal med-icine physicians who see a variety of complexpresentations and want to “do no harm.”Globally, medical education still emphasizesteaching traditional physical examination;however, no patient outcomes data justifyapplication of physical examination tech-niques learned for commonly encounteredclinical conditions. As an example, little dataexist regarding an evaluation of central venouspressure using jugular venous distention in amorbidly obese patient. Moreover, many
i.org/10.1016/j.mayocp.2016.08.023edical Education and Research
important cardiopulmonary abnormalities thatare easily and rapidly detected by POCUS,such as pericardial fluid, left ventricular (LV)systolic dysfunction, and pleural effusion, areoften missed by traditional physical examina-tion. It is conceivable that patients’ increas-ingly complex medical conditions,physicians’ declining physical examinationskills, and society’s expectation for higherstandards of medical care are all leading toincreased utilization of POCUS for more accu-rate bedside assessments of patients.
POCUS can immediately narrow thedifferential diagnosis by building on clinicalinformation revealed by the history and phys-ical examination10,11 and refine clinical deci-sion making for further work-up andtreatment.12 Recent studies have found thatclinical management involving the early useof POCUS accurately guides diagnosis, signifi-cantly reduces physicians’ diagnostic uncer-tainty, and also changes management andresource utilization.13 From a patient perspec-tive, “very low” discomfort was reportedduring POCUS of the heart, lungs, and deepveins, and most patients agreed to be evalu-ated with POCUS in an emergency depart-ment.14 Additionally, use of POCUS in theemergency department has been reported toimprove patient satisfaction and short-termhealth care resource utilization.15-17
LITERATURE REVIEW AND CLINICALAPPLICATIONSPOCUS can be helpful in a variety of commonclinical conditions by quickly identifyingabnormalities that may not be revealed by atraditional physical examination.2 For instance,consider the evaluation of a patient presentingwith unexplained dyspnea. In these patients,POCUS of the lungs can rapidly detect pleuraleffusions, pulmonary edema (B lines, a typeof comet tail artifact),18 pneumonia (consolida-tion with dynamic air bronchograms),19 orpneumothorax (absence of pleural sliding andpresence of a lung point sign).20
Other conditions readily detected withPOCUS include abdominal aortic aneu-rysms,21 deep venous thromboses,22 and peri-toneal free fluid.23 Central venous pressurecan be estimated by assessing the inferiorvena cava (IVC) or internal jugular vein sizeand collapsibility.24 Focused cardiac
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ultrasonography can expeditiously assessglobal LV and right ventricular function anddetect the presence of a pericardial effusion.25
Other common POCUS applications includevascular, musculoskeletal, sinus, ocular, nerve,thyroid, gallbladder, liver, spleen, renal, testic-ular, and bladder imaging (Figure 1).
Several medical and surgical subspecialtieshave adopted POCUS protocols to rule in orrule out certain conditions using an algo-rithmic approach. Common protocols includeBLUE (Bedside Lung Ultrasound in Emer-gency) for acute respiratory failure,26 FAST(Focused Assessment with Sonography inTrauma) for peritoneal free fluid,27 RUSH(Rapid Ultrasound for Shock and Hypoten-sion) for shock,28,29 and CLUE (Cardiovascu-lar Limited Ultrasound Examination) for heartfailure.30 These protocols offer a logicalPOCUS workflow for specific clinical sce-narios and provide a foundation to integratePOCUS findings into clinical decision making.
POCUS is not simply a diagnostic algorithmbut rather a tool used by a skilled clinician at thebedside to guide clinical decisionmaking in realtime. Although almost any diagnostic evalua-tion can be aided by POCUS (Figure 1, Table),we will describe 2 common patient scenariosto highlight the impact of POCUS on efficiency,diagnostic accuracy, resource utilization, radia-tion exposure, and patient satisfaction.
CASE 1A 41-year-old man with hypertension, type 2diabetes mellitus, and asthma presented to theoutpatient clinic with worsening shortness ofbreath. The shortness of breath had begunabruptly while the patient was at work in a cab-inet woodworking shop. He had been evaluatedin an urgent care clinic 1 week before presenta-tion and treated with a short course of cortico-steroids and inhaled albuterol. His symptomsimproved initially but subsequently worsened.He reported frequent ankle swelling that hadrecently increased. A review of systems revealedloud snoring at night but no angina, orthopnea,paroxysmal nocturnal dyspnea, recent travel/immobilization, or infectious symptoms.
Traditional Physical ExaminationTraditional physical examination revealed thefollowing:
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d Vital signs: Temperature, 36.2�C; pulse rate,90 beats/min; blood pressure, 128/85 mmHg; respiratory rate, 15 breaths/min; oxygensaturation, 95%; body mass index (calcu-lated as weight in kilograms divided byheight in meters squared), 31 kg/m2
d Head, ears, eyes, nose, and throat: Mildbilateral tenderness on percussion overmaxillary sinuses
d Pulmonary: Distant lung sounds, occasionalexpiratory wheezing bilaterally
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d Cardiovascular: Distant heart sounds, nomurmur, neck veins not visible, mild bilat-eral edema of the ankles
d Abdomen: Protuberant, no palpable hepa-tosplenomegaly, no shifting dullness or fluidwave
d Skin: No abnormalities
Differential Diagnosis. On physical examina-tion, the differential diagnosis includes asthmaexacerbation, congestive heart failure, allergic
pneumonitis secondary to wood dust, pneu-monia, and pulmonary hypertension due toobstructive sleep apnea.
Plan With Traditional Physical ExaminationAlone. For patients with the aforementionedfindings on traditional physical examination,the following steps would be taken:
d Outpatient chest radiographyd Addition of inhaled glucocorticoid andcontinuation of albuterol for asthma
d Follow-up in 3 to 5 days if no improvementnoted
POCUS-Assisted Physical ExaminationPOCUS-assisted physical examinationrevealed the following:
d Head, ears, eyes, nose, and throat: No fluidlevel present in either maxillary sinus(Figure 2, A)
FIGURE 2. Case 1. Point-of-care ultrasonographcompared with abnormal, fluid-filled maxillary sinus ((right) and abnormal lung with pulmonary edright diaphragm with pleural effusion and dilated inview of the heart showing thickened left ventricuaorta (Ao).
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d Pulmonary: Lung sliding bilaterallythroughout (Supplemental Video 1, availableonline at http://www.mayoclinicproceedings.org), multiple bilateral B lines (�3 per inter-space) in upper and lower lung fields(Figure 2, B; Supplemental Video 1), smallbilateral pleural effusions with associatedatelectasis (Figure 2, C; SupplementalVideo 2, available online at http://www.mayoclinicproceedings.org)
d Cardiovascular: Measurement of IVC was2.8 cm with less than 50% collapse on inspi-ration (Figure 2, C; Supplemental Video 2),no pericardial effusion, LV wall thickness of2 cm septal and 1.9 cm posterior, LV sys-tolic function severely reduced (Figure 2,D; Supplemental Video 3, available onlineat http://www.mayoclinicproceedings.org),no major mitral or tricuspid regurgitation,right ventricle difficult to view but doesnot appear substantially enlarged
ic images. A, Normal maxillary sinus (left)right). B, Pulmonary images showing normal lungema (left). C, View at the level of theferior vena cava (IVC). D, Parasternal long-axislar (LV) walls, left atrium (LA), and ascending
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d Abdomen: Liver span and spleen sizenormal, no ascites visible
Differential Diagnosis. Based on POCUSexamination findings of a plethoric IVC, bilat-eral B lines, pleural effusions, and severelyreduced LV systolic function, the primary diag-nosis in the differential is acute decompensatedsystolic heart failure with pulmonary edema andelevated central venous pressure. Asthma exac-erbation, allergic pneumonitis, pneumonia,and pulmonary hypertension with obstructivesleep apnea are highly unlikely based on thePOCUS examination findings.
Plan With POCUS-Assisted Physical Exam-ination. For patients with the aforementionedfindings on POCUS-assisted physical exami-nation, the following steps would be taken:
d Admit to hospital from clinicd Comprehensive transthoracic echocardiog-raphy to evaluate LV function and pericar-dial effusion the next morning
d Cardiac ischemic work-upd Intravenous diuresis
DiscussionThe identification of elevated central venouspressure (IVC dilation with minimalcollapse),38,49-53 pulmonary edema (bilateralinterstitial syndrome B lines),54-56 and pleuraleffusions combined with an unanticipatedreduction in LV systolic function25,41,57-64
dramatically changed this patient’s evaluationand management. During his inpatient work-up, isolated LV noncompaction was diagnosedafter cardiac magnetic resonance imaging andcoronary angiography.
Shortness of breath entails a broad differen-tial, and the addition of POCUS in real time atthe bedside can tremendously help mitigatedelay in appropriate testing and diag-nosis.26,33,34,65-74 The presence of B lines onthe initial pulmonary ultrasonography in thispatient focuses the differential on heart failure,pneumonia, interstitial lung disease, and poten-tially pulmonary embolism.26,55,56,74-76 Thedistribution of B lines is helpful in further nar-rowing the differential diagnosis.26 The presenceof bilateral diffuse B lines makes cardiogenicpulmonary edema, viral pneumonia, and other
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causes of diffuse interstitial lung abnormalitiesmost likely. The differential diagnosis is furthernarrowed by focused cardiac ultrasonographyto assess LV systolic function57,58,60,77 and anIVC examination to estimate the central venouspressure.78 In the absence of cardiac findingssuggestive of cardiogenic pulmonary edema, afocused work-up or empirical treatment ofpneumonia would have ensued.
The following workflow may be employed.(1) The lack of B lines on pulmonary ultraso-nography rules out dyspnea from hydrostaticcardiogenic pulmonary edema.26,54 (2) Thelack of consolidation or B lines reduces thelikelihood of pneumonia considerably; in apatient with a low pretest probability of pneu-monia, the diagnosis can be ruled out (notethat although the sensitivity of POCUS forpneumonia is high in critically ill patients,central pneumonia can be missed, especiallyin less severe cases frequently seen in out-patient presentations).19,26,34,66,70,71,74,79-81
(3) The differential diagnosis now includesobstructive lung disease and pulmonaryvascular disease that can be difficult to distin-guish with basic POCUS applica-tions.19,26,34,66,70,71,74,79-81 (4) Auscultationat this point may be valuable if findings ofobstructive lung disease, such as decreasedbreath sounds and wheezing, are present.(5) If findings of obstructive lung disease arenot present, a combination of venous andfocused cardiac ultrasonography can furthernarrow the differential diagnosis to improveefficiency of further work-up (Figure 3).
CASE 2A 69-year-old man with cirrhosis secondary toalcohol abuse, benign prostatic hypertrophy,type 2 diabetes mellitus, and nephrolithiasiswas admitted to the hospital with lethargy,confusion, increased abdominal distention,and a subjective fever over the preceding 24hours. He reported minimal oral intake anda mild productive cough for the past 2 weeks.A syncopal episode while getting out of bedprompted transport to the emergency depart-ment. Initial laboratory tests in the emergencydepartment revealed acute renal failure (ARF),leukocytosis, thrombocytopenia, and elevatedtroponin T level. Electrocardiography revealedsinus tachycardia with 1- to 2-mm lateralST-segment depression.
History, cardiacultrasonography,laboratory data History, laboratory data
History, traditional physicalexamination, cardiac
ultrasonography, laboratorydata, formal imaging
FIGURE 3. Typical point-of-care ultrasonography (POCUS)eintegrated approach to a patient presenting with shortness of breath.ARDS ¼ acute respiratory distress syndrome; a ¼ Supplemental Video 1; b ¼ Supplemental Video 6; c ¼ Supplemental Video 2.Supplemental videos are available online at http://www.mayoclinicproceedings.org.
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Traditional Physical ExaminationTraditional physical examination revealed thefollowing:
d Vital signs: Temperature, 37.7�C; pulse rate,110 beats/min; blood pressure, 72/32 mmHg; respiratory rate, 28 breaths/min; oxygensaturation, 91%; body mass index, 18 kg/m2
d Pulmonary: Decreased lung sounds bilater-ally at the bases, intermittent bibasilarcrackles
d Cardiovascular: Tachycardia, regularrhythm, no murmur, neck veins not visible,warm bilateral lower extremities with mildedema to the shin (right greater than left)
d Abdomen: Protuberant abdomen withbulging flanks and dullness to percussion,moderate diffuse tenderness on palpationwithout acute peritoneal signs, liver andspleen examination limited due to abdom-inal distention and pain, no costovertebralangle tenderness
d Skin: No jaundice, dilated venous patternon abdomen, palmar erythema, no rash
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Differential Diagnosis. (1) Hypotension andtachycardia secondary to (a) sepsis due to spon-taneous bacterial peritonitis (SBP), pneumonia,or biliary process, (b) cardiogenic shock due toalcoholic cardiomyopathy or ischemia, (c)obstructive shock from cardiac tamponade orpulmonary embolism, or (d) hypovolemicshock from diuretics and reduced intake; and(2) ARF secondary to (a) prerenal etiologies,including hypotension vs hepatorenal physi-ology, or (b) postrenal etiologies, such as benignprostatic hypertrophy or nephrolithiasis.
Plan With Traditional Physical ExaminationAlone. For patients with the aforementionedfindings on traditional physical examination,the following steps would be taken:
d Chest radiography to evaluate for possiblepulmonary infiltrate
d Blood and urine cultures, urinalysis, andliver biochemical tests
d Abdominal ultrasonography to evaluate forpossible obstructive biliary process and
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ascites, followed by diagnostic paracentesisperformed in the radiology department
d Central venous catheter (CVC) placementfor central venous pressure monitoring,fluid resuscitation, and possible vasopressorsupport
d Initiation of empirical broad-spectrum anti-biotics to cover potential pulmonary andabdominal sources of sepsis
d Comprehensive transthoracic echocardiog-raphy to evaluate LV function and pericar-dial effusion the next morning
d Renal ultrasonography in the radiologydepartment to evaluate for hydronephrosis
d Bladder scan or empirical urinary catheterplacement to measure postvoid residualurine volume
d Serial laboratory measurements of lactateand troponin levels with fluid resuscitation
POCUS-Assisted Physical ExaminationPOCUS-assisted physical examinationrevealed the following:
d Pulmonary: Bilateral lung sliding notedthroughout, bilateral elevated hemidia-phragm to tip of scapula with small bilateralpleural effusions and few B lines in bothdependent lung fields associated with mildbilateral atelectasis
d Cardiovascular: Focused cardiac ultrasonogra-phy revealed trace pericardial effusion, normalright ventricle size with increased contractility,hyperdynamic LVwith “kissing” endocardium(Supplemental Video 3, available online athttp://www.mayoclinicproceedings.org), IVCless than 1 cm in diameter with 100% collapseexcept during expiration (SupplementalVideo 4, available online at http://www.mayoclinicproceedings.org). Lower extremityvascular assessment revealed completecompression of saphenous veins, common/deep/superficial femoral veins, and poplitealveins bilaterally
d Abdomen: Moderate ascites throughout(Figure 4, A; Supplemental Video 5,available online at http://www.mayoclinicproceedings.org), small liver (8-cm midcla-vicular span) with scalloped cortex, enlargedspleen (19 cm in long axis and 8 cm in shortaxis) (Figure 4, B), minimally distendedbladder (Figure 4, C), and no hydronephro-sis (Figure 4, D). Gallbladder was noted to
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be normal with no sonographic Murphysign
Differential Diagnosis. Based on the POCUSfindings of a collapsed IVC, hyperdynamicLV, ascites, splenomegaly, and cirrhotic liver,the differential diagnosis was narrowed tohypovolemia secondary to sepsis syndromedue to SBP or possible biliary process andARF due to a prerenal/renal etiology.
Plan With POCUS-Assisted Physical Exam-ination. For patients with the aforementionedfindings on POCUS-assisted physical exami-nation, the following steps would be taken:
d Bedside paracentesis with ultrasound guid-ance to evaluate for SBP (SupplementalVideo 5)
d Immediate volume resuscitationd Serial bedside POCUS of LV, IVC, and lungsduring fluid resuscitation to monitor forearly signs of pulmonary edema with lowthreshold for transfer to critical care unitfor vasopressor and fluid support
d Empirical broad-spectrum antibiotics tocover possible SBP and biliary source ofsepsis
d Blood and urine cultures, urinalysis, andliver biochemical tests
d Consider right upper quadrant ultrasonog-raphy for possible obstructive biliary process
d Serial laboratory testing including lactateand troponin levels with fluidresuscitation
d Comprehensive transthoracic echocardio-graphy to evaluate LV function and pericar-dial effusion the next morning
DiscussionBedside ultrasound-guided paracentesis hasbeen reported to be safe and effective whenperformed by nonradiologists82-84 and canquickly identify the source of sepsis. Volumeresuscitation guided by POCUS includesdiscontinuation of intravenous fluids whenthe POCUS examination reveals early signsof pulmonary edema74,85 or when minimalchange in stroke volume occurs with a passiveleg raise.86-91 This patient was transitioned tothe intensive care unit for initiation of earlyvasopressor support. The ARF normalized
FIGURE 4. Case 2. Point-of-care ultrasonographic images. A, Cirrhotic liver with surrounding ascites.B, Enlarged spleen measuring 18.5�8.2 cm compared with a normal sized spleen (inset). C, Minimallydistended bladder in transverse plane with approximately 75 mL of urine. D, Normal kidney withouthydronephrosis compared with kidney with moderate hydronephrosis (inset).
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over the next 48 hours with fluid resuscitationand vasopressor support.
Hypotension has a broad differential diag-nosis, as in this case, and poses a diagnosticand therapeutic challenge to internists.POCUS of the heart, lungs, abdomen, and pe-ripheral vascular system can expedite evalua-tion for potential etiologies of hypovolemic,distributive, cardiogenic, or obstructiveshock.29,66,92-97 Serial POCUS can be used tomonitor ongoing fluid resuscitation and helpdetermine the need for vasopressorsupport.85,98
Acute renal failure is common in the inpa-tient setting and often creates a diagnosticdilemma. A POCUS examination of the kid-neys has been found to rapidly and effectivelyrule out hydronephrosis and guide the needfor urinary catheterization.99 POCUS of thelungs and cardiovascular system supplementsthe renal examination by providing
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information on hemodynamics to assess renalperfusion.100-103
CHALLENGES AND PITFALLSDespite the several undisputed advantages ofutilizing POCUS, there are several barriersand pitfalls to consider. First, there are chal-lenges relating to equipment and technology.POCUS can be performed with a variety ofavailable equipment: full-sized traditional ma-chines, laptop-sized devices, and pocket-sizeddevices. Even ultrasound transducers that canbe plugged directly into handheld computersare now available. Although many physiciansgenerally prefer compact ultrasonography de-vices for portability, these devices have limitedability to adjust image quality. Concerns havebeen raised about small handheld systemswith regard to their narrow sector, smallerfield of view, lower resolution, and simplifiedtransducer technology.25,104,105 Although
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studies have documented that small ultraso-nography devices can be used to answerfocused questions,18,61,106-115 operators mustbe aware of their limitations.
From an operator and training perspective,studies have found that the utility of a POCUSexamination depends on the experience andskills of the operator.42,48,116-120 Operatortraining is crucial for POCUS to be utilizedcorrectly in patient care, and studies haverevealed that barriers to POCUS adoptioninclude insufficient faculty training, high costof ultrasonography machines, and timerequired to train physicians.45,121 The relativelyhigh level of operator dependency comparedwith other diagnostic testing is reasonably ex-pected, given the multiple skills required toperform a POCUS examination. First, a POCUSexamination begins with formulation of a spe-cific clinical question and a decision to utilizePOCUS to answer this question.122 Next, acqui-sition of images requires knowledge of sono-graphic windows, ultrasound physics, andhand-eye-brain coordination to manipulatethe transducer to optimize image quality.122
Interpretation of POCUS images requires skillsthat are independent from physical examinationskills, and operators must recognize artifactsthat are encountered during image acquisitionand interpretation.122 Most importantly,POCUS findings must be interpreted and inte-grated with other clinical data to effectivelyguide clinical decision making.122 Failureduring any step of this multistep process mayundermine the true value of using POCUS.
The skills needed to perform POCUS ex-aminations have not been uniformly taughtin undergraduate or graduate medical educa-tion. Although a movement to integratePOCUS education into medical schools orinternal medicine residency programs hasbeen gaining momentum over the pastdecade,43,121,123-129 there is no consensus onthe training required to reach adequatePOCUS competency levels in general internalmedicine.25,104,110,111,130-133 It is generallyagreed that training must include basic knowl-edge of ultrasound physics and supervisedimage acquisition and interpretation prac-tice.25,104,110,111,130-133
Other potential challenges include theavailability of templates for documentation,electronic storage for image archiving, and
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policies and procedures for quality assuranceand billing. Emergency medicine societieshave addressed these issues and assistedphysicians in understanding correct andcompliant coding for the past 2 de-cades.37,39,40 In terms of billing, POCUS canpotentially influence the evaluation and man-agement code by affecting the complexity ofmedical decision making (Current ProceduralTerminology).112-115 Some believe that reim-bursement is essential to cover the substantialcost of POCUS education and equipment pur-chasing and maintenance.112-115 Conversely,others view POCUS as an extension of thephysical examination, which raises concernsthat a heavy focus on billing may block theroutine use of POCUS.116-118 Future reim-bursement systems that capture an “episodeof care,” also known as “bundling,” will likelychange the perspectives on POCUS billing,documentation, and image archiving.112,117
As the workflow for POCUS in internal medi-cine matures, medical practices will berequired to provide the administrative infra-structure needed to meet these evolving stan-dards of care for use of POCUS.25,104,116
For effective integration of POCUS into clin-ical care, quality assurance is an importantconsideration. Although quality assurance hasbeen emphasized to avoid misinterpretation ofimages, most malpractice cases related toPOCUS in emergency medicine have been dueto failure to perform a POCUS examination ina timely manner, rather than misinterpretationor misdiagnosis with the use of POCUS.76 Theextent to which quality assurance will be neededin internal medicine and other specialties is yetto be determined because increased legal risksmay occur with either failure to use POCUS ormisinterpretation of POCUS images.
FUTURE RESEARCHEarly POCUS research focused on diagnosticaccuracy to establish that health care profes-sionals with focused training in ultrasonogra-phy can acquire and interpret imagesaccurately. The diagnostic accuracy of front-line physicians performing POCUS examina-tions has been compared with imagingacquired by full-time sonographers and inter-preted by imaging specialists, primarily radiol-ogists or cardiologists. Several publishedstudies have proven that POCUS has
diagnostic accuracy similar to that of criterionstandard imaging studies for specific findings,such as pneumothorax,67,119 pericardial effu-sion,42,120 or lower extremity deep venousthrombosis.48 However, few studies havecompared the diagnostic accuracy of POCUSvs the traditional diagnostic approach usinghistory and physical examination. Interest-ingly, these studies have clearly confirmedthe superiority of POCUS. For instance, halfas many major cardiac findings were missedwhen a cardiac physical examination per-formed by experienced cardiologists wassupplemented with a focused cardiac ultraso-nographic examination.121 Although a fairercomparison may be to compare the diagnosticaccuracy of POCUS to that of physical exami-nation, rather than criterion standard imagingstudies, few comparative studies of internist-performed physical examinations, with orwithout the addition of POCUS, have beenpublished.45
During the past 15 years, POCUS researchhas shifted focus from diagnostic accuracy todemonstration of improved health outcomes.Use of POCUS to guide bedside procedureshas been reported to reduce procedure-related complications, including arterial punc-tures during central venous catheterization,134
postthoracentsis pneumothorax, and postpar-acentesis bleeding complications, along withthe costs and lengths of stay associated withthese complications.123,124 However, few ran-domized trials have been published, and apaucity of data exists supporting the routineuse of POCUS for diagnostic evalua-tions.15,69,77,125-127 Only one randomized trialwith internal medicineetrained physicians hasbeen published comparing routine focusedcardiac ultrasonography vs standard care inhospitalized general medicine patients. Thisstudy found a potential reduction in lengthof stay with the use of POCUS in the cohortof patients with heart failure.43 Thus, compar-ative studies evaluating the clinical and healthservices outcomes of usual care with andwithout the routine use of POCUS by inter-nists for different conditions are needed.
Another interesting facet of POCUSresearch is whether the higher-priority focusis physician training or clinical outcomes. Afundamental question has yet to be answered:How do we effectively train health care
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professionals, ranging from medical studentsto senior attending physicians, to utilizePOCUS? Experts generally agree that the useof POCUS requires basic knowledge of ultraso-nography, image acquisition and interpretationskills, and an understanding of integration ofPOCUS findings into clinical decision making.If we believe that the focus should be outcomesresearch rather than training, then we are rele-gated to performing studies with a few expertsperforming all POCUS examinations, whichmay be biased toward benefit because theexperts’ skill level is beyond what may beachievable by a physician with average POCUSskills. On the contrary, if we believe trainingshould be the focus, then medical institutions,including medical schools, hospitals, andhealth care systems, will have to invest intraining physicians in basic POCUS applica-tions before large effectiveness trials can beundertaken to evaluate the impact of POCUSon clinical outcomes. As this debate hascontinued, medical schools have begun toinvest heavily in integrating POCUS traininginto clinical skills education, and positive stu-dent reviews and publicity continue to drivethis integration in medical school curricula.Meanwhile, practicing internists are feelinggrowing pressures to acquire basic POCUSskills because their trainees may have moreadvanced POCUS skills than they do.
From a health care system perspective, thefield of POCUS is ripe for health servicesresearch because an increasing number ofPOCUS applications are recommended byevidence-based guidelines. For example,consider the use of ultrasound guidance toplace CVCs. Since the early 2000s, ultrasoundguidance for placement of CVCs has beenrecommended by national patient safetyand quality organizations on the basis of severalrandomized trials and meta-analyses128,129,135;however, the use of ultrasound guidance toinsert CVCs has not been universally adoptedin clinical practice. Investigations usingmethods from implementation science mayreveal barriers to adoption of POCUS use forCVC insertion. Lessons learned from studyingthis implementation gap may guide futureimplementation of POCUS use within the prac-tice of internal medicine.
Certain POCUS applications with well-proven benefits, such as use of ultrasound
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guidance for insertion of CVCs, are primed forsystem-wide implementation. However, adiversified approach to POCUS research isneeded in view of the varying levels of evi-dence supporting different POCUS applica-tions. For known POCUS applications thatare not yet the standard of care, such as eval-uation of acute dyspnea with POCUS, addi-tional clinical outcomes and health servicesresearch will likely be needed to confirmbenefit and assess the effect on health carecosts, length of stay, and patient experience.For other newer, novel POCUS applications,such as elastography and 3-dimensional ultra-sound imaging, diagnostic accuracy studiesare needed to establish their role in clinicalmedicine. Underlying this broad spectrum ofclinical research needs is the need for educa-tional research to help us understand how toeffectively train physicians to use POCUS.Educational research will help us define thescope of training, identify resources needed(equipment, faculty/staff time), and set realisticgoals for training programs.
CONCLUSIONEmpowering internists to assess patients usingPOCUS is an inevitable change in the practiceof internal medicine that has already begun todisseminate. The ability to visualize patho-physiologic features in real time using POCUScan provide expedited, high-quality, safe, andcost-conscious patient care. As new clinicaland educational research emerges, our under-standing of how to integrate POCUS into clin-ical practice will improve, and routine use ofPOCUS in clinical practice will establish newstandards of care.
SUPPLEMENTAL ONLINE MATERIALSupplemental material can be found online athttp://www.mayoclinicproceedings.org. Sup-plemental material attached to journal articleshas not been edited, and the authors takeresponsibility for the accuracy of all data.
Abbreviations and Acronyms: ARF = acute renal failure;CVC = central venous catheter; IVC = inferior vena cava;LV = left ventricular; POCUS = point-of-care ultrasonog-raphy; SBP = spontaneous bacterial peritonitis
Correspondence: Address to Anjali Bhagra, MBBS, Divisionof General Internal Medicine, Mayo Clinic, 200 First St SW,Rochester, MN 55905 ([email protected]).
Mayo Clin Proc. n December 2016;91(12):1811-1827 n http://dx.dowww.mayoclinicproceedings.org
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