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Ultrasound to reduce cognitive errors in the ED
American Journal of Emergency Medicine (2012) 30, 2030–2033
www.elsevier.com/locate/ajem
Brief Report
Ultrasound to reduce cognitive errors in the ED Fabrizio Elia MD ⁎, Francesco Panero MD, Paola Molino MD, Giovanni Ferrari MD, Franco Aprà MD High Dependency Unit, San Giovanni Bosco Hospital, Piazza Donatore del Sangue 3, 10154 Torino, Italy Received 14 February 2012; revised 4 April 2012; accepted 4 April 2012
Abstract Emergency medicine setting is intrinsically prone to a greater risk of medical errors than other specialties. Cognitive errors are particularly frequent when the clinical decision-making process heavily relies on heuristics. These could be defined as “mental shortcuts,” which enable physicians to rapidly overcome both time and efforts required by the normative reasoning. Our article demonstrates how emergency physicians' thinking may be affected by failed heuristics, through the description of 3 real clinical cases. We aimed to show how the proper use of a widespread and easy-learning technology, such as goal-directed, focused ultrasonography, may both counteract cognitive errors and favor the right interpretation of other examinations. © 2012 Elsevier Inc. All rights reserved.
Emergency medicine is intrinsically prone to a greater risk of medical errors than other specialties [1-3]. Emergency physicians usually are called to care for unstable patients with life-threatening conditions, to take both rapid and sharp decisions about unclear clinical pictures and to exercise into probabilistic reasoning. Among several types of medical errors, cognitive ones, namely, cognitive failures occurring during the clinical decision making process, are associated with a higher morbidity [4,5] and have been recently investigated by a lot of literature [6-9]. Cognitive errors are particularly frequent when the clinical decision-making process heavily relies on heuristics [3,6]. These could be defined as “mental shortcuts,” such as maxims and rules of thumb, which enable physicians to rapidly overcome both time and efforts required by the normative reasoning [6,7]. Heuristics are often unconsciously used by many emergency physicians
⁎ Corresponding author. Tel.: + 39 3333601931; fax: +39 0112402236. E-mail addresses: [email protected] (F. Elia), [email protected] (F. Panero), [email protected] (P. Molino), [email protected] (G. Ferrari), [email protected] (F. Aprà). 0735-6757/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2012.04.008
because they prove useful and effective most of the times, but failed heuristics may produce cognitive errors. In this article, we aimed to investigate how emergency physicians' thinking may be affected by failed heuristics, through the description of 3 real clinical cases. We aimed, therefore, to show how the proper use of a widespread and easy-learning technology, such as goal-directed focused ultrasonography (US), may both counteract cognitive errors and favor the right interpretation of other examinations.
1. Case 1 A 68-year-old man presented to the emergency department (ED) with a 1-week history of fever, diarrhea, oliguria and weakness. His medical history was unremarkable. On arrival, the patient appeared in moderate distress. The blood pressure was 80/50 mm Hg; the pulse, 110 beats per minute rhythmic; the respiratory rate, 20 breaths per minute; the oxygen saturation, 95% while breathing ambient air and the temperature, 37°C. Extremities appeared cool while lung, hearth and abdomen did not show any abnormality; jugular
Ultrasound, cognitive errors and emergency medicine veins were plane. Laboratory tests yielded a high white blood cell count and a normal D-dimer. Sinusal tachycardia and a mild cardiomegaly with a bilateral basal pleural effusion were, respectively, seen on electrocardiogram (ECG) and chest radiography. A presumptive diagnosis of either septic or hypovolemic shock due to a gastrointestinal infection was made: intravenous fluid replacement, antibiotics and amines were begun. Nevertheless, hemodynamic instability persisted despite adequate fluid administration. A bedside US examination performed by an emergency physician highlighted a pericardial effusion with right atrial wall collapse. An urgent pericardiocentesis was performed; after the removal of several deciliters of hematic fluid, hemodynamic parameters turned back to the reference range. Fluid analysis revealed neoplastic cells, and a chest computed tomography discovered a lung cancer involving the pericardium.
2. Case 2 A 60-year-old woman presented to the ED because of malaise, oliguria and dyspnea. Her medical history included hypertension, rheumatoid arthritis on steroidal therapy, obstructive sleep apnea syndrome, hypothyroidism, previous episodes of urinary tract infection and deep venous thrombosis. Her mobility was impaired by both obesity and musculoskeletal pain. On arrival, she appeared in acute distress. Blood pressure was 80/50 mm Hg; the pulse was 120 beats per minute rhythmic; the temperature, 37°C and the oxygen saturation was 90% on air. Lower extremities appeared cool and edematous, whereas the remainder of the examination was normal. The ECG demonstrated sinusal tachycardia with no signs of myocardial ischemia. Blood tests yielded leukocytosis, renal failure, and increased D-dimer levels. Pulmonary embolism was suspected. A computed tomography of the chest was obtained and confirmed the presence of massive pulmonary embolism. Aggressive fluid infusion was instituted and the patient was transferred to our unit to perform thrombolytic therapy. Despite the large amount of fluid, she still appeared shocked. A bedside US disclosed a normokinetic and not dilatated right ventricle with a small and collapsing inferior vena cava. In consideration of these findings, thrombolytic therapy was withhold and the patient underwent further fluid resuscitation and amines. Preliminary results of urine analysis confirmed a urinary tract infection. Early goal-directed therapy was implemented with success and the patient's conditions gradually improved.
3. Case 3 A 75-year-old man presented to the ED with 1-week history of dyspnea. The patient was a smoker and had a medical history of hypertension, hypertrophic cardiopathy
2031 with recurrent episodes of heart failure and mood disorder. He was normotensive, afebrile, tachycardic (115 beats per minute) tachypneic (respiratory rate 25 breaths per minute) and his saturation was 92% in room air. Physical examination revealed bilateral basal rales and both cool and diaphoretic skin; other findings were unremarkable such as the ECG. Supine chest x-rays showed mild interstitial pulmonary edema. Two hours later, his conditions worsened and a severe respiratory failure became evident. Treatment with diuretics, nitrates, morphine and noninvasive ventilation were started upon a presumptive diagnosis of pulmonary edema. On arrival into our high dependency unit, he appeared cold, hypotensive, tachycardic and tachypneic (respiratory rate, 33 breaths per minute). Peripheral saturation was 90% on 50% of inspired oxygen. A bedside US revealed no signs of interstitial syndrome on both chest anterior and lateral scans, whereas an alveolar consolidation with dynamic bronchogram was detected on the right lower lung field; the left ventricle appeared small, hypertrophic and hyperdynamic and inferior vena cava showed a complete inspiratory collapse. A diagnosis of pneumonia was made and proper therapy addressed. The day after, chest x-ray was repeated and an alveolar consolidation appeared on the right lower lung field. Streptococcus pneumoniae urinary antigen tests turned indeed positive.
4. Discussion Emergency physicians are expected to have several skills: procedural, affective and cognitive [8]. Cognitive faculties deserve particular attention, as they are the bases of the clinical decision-making process. “Evidence-based medicine” as with the Bayesian method has been stressed as the axiomatic approach to the modern medicine. Nevertheless, the human abilities are limited and both gathering and retrieving information are inaccurate processes [2,9]. Furthermore, in emergency medicine, “a priori” probabilities often are unknown, whereas missing data and ambiguities are frequent so that the “flesh and blood” decision making is the rule, whereas normative and robotic models are the exception [8,10]. This particular field favors intuitive and automatic tools as heuristics [1,5]. All 3 of our cases are presented as prototypical of the heuristic reasoning in clinical situations requiring a rapid decision under uncertainty. In case 1, the patient presented a clinical picture compatible with septic or hypovolemic shock. Anamnesis was significant for previous fever and diarrhea so that any other relevant detail was not further elicited by the physician and a premature diagnosis of septic shock was made. As being more frequent than cardiac tamponade, sepsis and hypovolemia may have come into physician's mind more readily than other diagnosis even because they were confirmed by congruent physical findings (cold extremities, plane jugulars, sinusal tachycardia, etc). A “representativeness bias” took place. Representativeness
2032 occurs when a clinical condition is considered unlikely unless the presentation is prototypical of it. As fitting most but not all of available data, septic shock was considered the prominent diagnosis. On the contrary, cardiac tamponade was not taken into account because typical signs were absent. No other competing diagnosis was hypothesized, neither when chest x-ray reported both an unexplained mild cardiomegaly and bilateral pleural effusion. Physician stood anchored to his initial judgment and prematurely closed the case. “Anchoring” is the tendency to stick with the initial impression and not to adjust it according to further data. As in this case, anchoring goes often together with the confirmation bias (when physicians consider only data consistent with their hypothesis while the others are scotomized) and the “premature closure” (ceasing to look for differential diagnosis). Similarly, in case 2, heuristics of representativeness (congruent clinical picture with a previous episode of deep venous thrombosis), confirmation bias (a chest computed tomography was ordered to confirm the diagnosis but a history of recurrent urinary infection passed unnoticed) and premature closure are clear. A further cognitive bias highlighted through this case is “search satisfying.” It occurs when the diagnostic reasoning stops as soon as something is found. Unfortunately, diagnostic findings may appear as accidental discoveries unrelated to the present illness, especially using new imaging technologies. In our case, the patient was diagnosed with pulmonary embolism, but no US signs of obstructive shock were discovered. In patients with pulmonary embolism presenting with shock, the absence of US signs of right ventricular dysfunction excludes pulmonary embolism as a cause of hemodynamic instability [11]. As pulmonary embolism was initially confirmed by the computed tomography, a sort of “blind obedience” was put by the emergency physicians who did not look for other details. Blind obedience is defined as the “undue deference to either authority or technology” [7]. Blind obedience, confirmation bias, search satisfying and premature closure appear strictly linked in this case. US examination and critical reappraisal of the whole story highlighted some anamnestic details previously unnoticed and prevented unnecessary therapies. Case 3 underscores how physicians tend to persist on the same hypothesis if it has been diagnosed several times before. This is the so called “posterior probability error”: a history of recurrent diastolic heart failure lowered the “a posteriori” probability for any diagnosis different from heart failure [6,8]. Probably a certain grade of both confirmation bias and blind obedience were due to the x-rays findings, not considering that x-rays may be misleading in supine patients, radiographic signs of pneumonia need time to appear, and sometimes, radiography remains negative. On the contrary, US may be useful in the diagnosis of alveolar consolidation, also for patients with radio-occult pneumonia [12,13]. Furthermore, US finding of typical diffuse B-lines pattern shows high sensitivity resulting a rule-out test for the
F. Elia et al. alveolar-interstitial syndrome and allowing to distinguish between cardiogenic and noncardiogenic dyspnea [14,15]. Several strategies have been proposed to counteract cognitive errors. Literature has invoked many debiasing techniques such as metacognition, prospective hindsight, comprehensive differential diagnosis, pattern recognition, consideration of the opposite, checklists implementation or proper use of follow-up [3,4]. Some of these have proved to ameliorate both patients' outcomes and length of stay in the intensive care unit [5]. Their common denominator is to enable the physician to critically reexamine, step by step, the cognitive paths that has lead him to take some decision. Here, we propose a different approach to limit such predictable bias: the judicious use of “visual medicine.” Emergency goaldirected, focused US is relatively easy learning, repeatable, low cost; it does not use ionizing radiation and helps to diagnose life-threatening conditions, guide invasive procedures, treat medical emergencies, and monitor pathologic changes [16]. Some have argued the US probe as an extension of the stethoscope and point-of-care US as the visual inspection beyond the physical examination [14]. In the 3 presented cases, US provided a valuable help to the definition of the right diagnosis. In the first, it discriminated between septic shock and cardiac tamponade, whose specific characteristics were lacking (no jugular distension and normal ECG voltages) and further guided an evacuative pericardiocentesis. In the second, it fully defined a massive pulmonary embolism as not being the cause of the shock (no US signs of acute right heart failure) and lead to the reappraisal of other competing causes of hemodynamic instability. In the last, it provided a visual differentiation between 2 opposite causes of dyspnea and guaranteed the institution of a life-saving therapy, even before classic imaging techniques had turned positive. Nevertheless, US may be exposed to the same pitfalls and has its own limitations. First, both hypothesis generation and differential diagnosis process should drive the “proper” use of goal-directed, focused US as with any other test. This means that it must be implemented whenever clear questions need to be addressed and US is technically able to answer these ones. If the first requirement should not be met, either “incidental” or meaningless US findings might divert the physician from the right interpretation of the clinical picture and promote further unnecessary or even dangerous examinations. In the 3 presented cases, US properly fulfilled 3 of 5 tasks that traditionally have been assigned to its application in the emergency setting: diagnostic, procedure guidance and symptom or sign based [16]. However, a lot of literature has assessed the effectiveness of clinical US and newer evidence is available for several core emergency US applications (trauma, shock, dyspnea, chest pain, etc). Moreover, the technical applicability of US has several meanings. Like any other test, it has definite sensibility and specificity in the identification of any clinical picture; these characteristics are even more variable, as it is an operatordependent technique. Therefore, like any other practical or
Ultrasound, cognitive errors and emergency medicine cognitive debiasing technique, US needs specific training. It does not work outside the “Bayesian model”: ultrasound findings should always be interpreted in terms of likelihood ratios and posterior probabilities according to both the clinical picture and the epidemiology of diseases; nevertheless, US can itself elicit alternative diagnosis, give further information to make tasks easier and provide reliable feedbacks. We think that the clinical decision-making procedure should be a continuous process of generation of competing hypothesis, asking for proper examinations, gathering new data according to them and interpreting information with respect to both previous and epidemiologic ones to formulate a diagnosis of probability. Continuous reappraisal and critical interpretation of all information are the mainstay of both the diagnosing process and the conscious use of heuristics. Ultrasonography may deserve an important role in overcoming our cognitive limits as any other debiasing strategy. In the same way, its correct application requires adequate training, knowledge of its limitation and deliberate critic.
References [1] Croskerry P, Norman G. Overconfidence in clinical decision making. Am J Med 2008;121:S24-9. [2] Berner ES, Graber ML. Overconfidence as a cause of diagnostic error in medicine. Am J Med 2008;121(5 Suppl):S2-23.
2033 [3] Croskerry P. Cognitive forcing strategies in clinical decision making. Ann Emerg Med 2003;41:110-20. [4] Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med 2003;78:775-80. [5] Ely JW, Graber ML, Croskerry P. Checklists to reduce diagnostic errors. Acad Med 2011;86(3):307-13. [6] Gorini A, Pravettoni G. An overview on cognitive aspects implicated in medical decisions. Eur J Intern Med 2011;22:547-53. [7] Redelmeier DA. Improving patient care. The cognitive psychology of missed diagnoses. Ann Intern Med 2005;142:115-20. [8] Croskerry P. The cognitive imperative: thinking about how we think. Acad Emerg Med 2000;7:1223-31. [9] Kuhn GJ. Diagnostic errors. Acad Emerg Med 2002;9:740-50. [10] Adams JG, Bohan JS. System contributions to error. Acad Emerg Med 2000;7(11):1189-93. [11] Torbicki A, Perrier A, Konstantinides S, et al, ESC Committee for Practice Guidelines (CPG). Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC). Eur Heart J 2008;29: 2276-315. [12] Parlamento S, Copetti R, Di Bartolomeo S. Evaluation of lung ultrasound for the diagnosis of pneumonia in the ED. Am J Emerg Med 2009;27:379-84. [13] Soldati G, Testa A, Silva FR. Chest ultrasonography in lung contusion. Chest 2006;130:533-8. [14] Lichtenstein DA. Ultrasound in the management of thoracic disease. Crit Care Med 2007;35:S250-61. [15] Lichtenstein D, Meziere G. A lung ultrasound sign allowing bedside distinction between pulmonary edema and COPD: the comet-tail artifact. Intensive Care Med 1998;24:1331-4. [16] American College of Emergency Physicians. Emergency ultrasound guidelines. www.acep.org.
www.elsevier.com/locate/ajem
Brief Report
Ultrasound to reduce cognitive errors in the ED Fabrizio Elia MD ⁎, Francesco Panero MD, Paola Molino MD, Giovanni Ferrari MD, Franco Aprà MD High Dependency Unit, San Giovanni Bosco Hospital, Piazza Donatore del Sangue 3, 10154 Torino, Italy Received 14 February 2012; revised 4 April 2012; accepted 4 April 2012
Abstract Emergency medicine setting is intrinsically prone to a greater risk of medical errors than other specialties. Cognitive errors are particularly frequent when the clinical decision-making process heavily relies on heuristics. These could be defined as “mental shortcuts,” which enable physicians to rapidly overcome both time and efforts required by the normative reasoning. Our article demonstrates how emergency physicians' thinking may be affected by failed heuristics, through the description of 3 real clinical cases. We aimed to show how the proper use of a widespread and easy-learning technology, such as goal-directed, focused ultrasonography, may both counteract cognitive errors and favor the right interpretation of other examinations. © 2012 Elsevier Inc. All rights reserved.
Emergency medicine is intrinsically prone to a greater risk of medical errors than other specialties [1-3]. Emergency physicians usually are called to care for unstable patients with life-threatening conditions, to take both rapid and sharp decisions about unclear clinical pictures and to exercise into probabilistic reasoning. Among several types of medical errors, cognitive ones, namely, cognitive failures occurring during the clinical decision making process, are associated with a higher morbidity [4,5] and have been recently investigated by a lot of literature [6-9]. Cognitive errors are particularly frequent when the clinical decision-making process heavily relies on heuristics [3,6]. These could be defined as “mental shortcuts,” such as maxims and rules of thumb, which enable physicians to rapidly overcome both time and efforts required by the normative reasoning [6,7]. Heuristics are often unconsciously used by many emergency physicians
⁎ Corresponding author. Tel.: + 39 3333601931; fax: +39 0112402236. E-mail addresses: [email protected] (F. Elia), [email protected] (F. Panero), [email protected] (P. Molino), [email protected] (G. Ferrari), [email protected] (F. Aprà). 0735-6757/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2012.04.008
because they prove useful and effective most of the times, but failed heuristics may produce cognitive errors. In this article, we aimed to investigate how emergency physicians' thinking may be affected by failed heuristics, through the description of 3 real clinical cases. We aimed, therefore, to show how the proper use of a widespread and easy-learning technology, such as goal-directed focused ultrasonography (US), may both counteract cognitive errors and favor the right interpretation of other examinations.
1. Case 1 A 68-year-old man presented to the emergency department (ED) with a 1-week history of fever, diarrhea, oliguria and weakness. His medical history was unremarkable. On arrival, the patient appeared in moderate distress. The blood pressure was 80/50 mm Hg; the pulse, 110 beats per minute rhythmic; the respiratory rate, 20 breaths per minute; the oxygen saturation, 95% while breathing ambient air and the temperature, 37°C. Extremities appeared cool while lung, hearth and abdomen did not show any abnormality; jugular
Ultrasound, cognitive errors and emergency medicine veins were plane. Laboratory tests yielded a high white blood cell count and a normal D-dimer. Sinusal tachycardia and a mild cardiomegaly with a bilateral basal pleural effusion were, respectively, seen on electrocardiogram (ECG) and chest radiography. A presumptive diagnosis of either septic or hypovolemic shock due to a gastrointestinal infection was made: intravenous fluid replacement, antibiotics and amines were begun. Nevertheless, hemodynamic instability persisted despite adequate fluid administration. A bedside US examination performed by an emergency physician highlighted a pericardial effusion with right atrial wall collapse. An urgent pericardiocentesis was performed; after the removal of several deciliters of hematic fluid, hemodynamic parameters turned back to the reference range. Fluid analysis revealed neoplastic cells, and a chest computed tomography discovered a lung cancer involving the pericardium.
2. Case 2 A 60-year-old woman presented to the ED because of malaise, oliguria and dyspnea. Her medical history included hypertension, rheumatoid arthritis on steroidal therapy, obstructive sleep apnea syndrome, hypothyroidism, previous episodes of urinary tract infection and deep venous thrombosis. Her mobility was impaired by both obesity and musculoskeletal pain. On arrival, she appeared in acute distress. Blood pressure was 80/50 mm Hg; the pulse was 120 beats per minute rhythmic; the temperature, 37°C and the oxygen saturation was 90% on air. Lower extremities appeared cool and edematous, whereas the remainder of the examination was normal. The ECG demonstrated sinusal tachycardia with no signs of myocardial ischemia. Blood tests yielded leukocytosis, renal failure, and increased D-dimer levels. Pulmonary embolism was suspected. A computed tomography of the chest was obtained and confirmed the presence of massive pulmonary embolism. Aggressive fluid infusion was instituted and the patient was transferred to our unit to perform thrombolytic therapy. Despite the large amount of fluid, she still appeared shocked. A bedside US disclosed a normokinetic and not dilatated right ventricle with a small and collapsing inferior vena cava. In consideration of these findings, thrombolytic therapy was withhold and the patient underwent further fluid resuscitation and amines. Preliminary results of urine analysis confirmed a urinary tract infection. Early goal-directed therapy was implemented with success and the patient's conditions gradually improved.
3. Case 3 A 75-year-old man presented to the ED with 1-week history of dyspnea. The patient was a smoker and had a medical history of hypertension, hypertrophic cardiopathy
2031 with recurrent episodes of heart failure and mood disorder. He was normotensive, afebrile, tachycardic (115 beats per minute) tachypneic (respiratory rate 25 breaths per minute) and his saturation was 92% in room air. Physical examination revealed bilateral basal rales and both cool and diaphoretic skin; other findings were unremarkable such as the ECG. Supine chest x-rays showed mild interstitial pulmonary edema. Two hours later, his conditions worsened and a severe respiratory failure became evident. Treatment with diuretics, nitrates, morphine and noninvasive ventilation were started upon a presumptive diagnosis of pulmonary edema. On arrival into our high dependency unit, he appeared cold, hypotensive, tachycardic and tachypneic (respiratory rate, 33 breaths per minute). Peripheral saturation was 90% on 50% of inspired oxygen. A bedside US revealed no signs of interstitial syndrome on both chest anterior and lateral scans, whereas an alveolar consolidation with dynamic bronchogram was detected on the right lower lung field; the left ventricle appeared small, hypertrophic and hyperdynamic and inferior vena cava showed a complete inspiratory collapse. A diagnosis of pneumonia was made and proper therapy addressed. The day after, chest x-ray was repeated and an alveolar consolidation appeared on the right lower lung field. Streptococcus pneumoniae urinary antigen tests turned indeed positive.
4. Discussion Emergency physicians are expected to have several skills: procedural, affective and cognitive [8]. Cognitive faculties deserve particular attention, as they are the bases of the clinical decision-making process. “Evidence-based medicine” as with the Bayesian method has been stressed as the axiomatic approach to the modern medicine. Nevertheless, the human abilities are limited and both gathering and retrieving information are inaccurate processes [2,9]. Furthermore, in emergency medicine, “a priori” probabilities often are unknown, whereas missing data and ambiguities are frequent so that the “flesh and blood” decision making is the rule, whereas normative and robotic models are the exception [8,10]. This particular field favors intuitive and automatic tools as heuristics [1,5]. All 3 of our cases are presented as prototypical of the heuristic reasoning in clinical situations requiring a rapid decision under uncertainty. In case 1, the patient presented a clinical picture compatible with septic or hypovolemic shock. Anamnesis was significant for previous fever and diarrhea so that any other relevant detail was not further elicited by the physician and a premature diagnosis of septic shock was made. As being more frequent than cardiac tamponade, sepsis and hypovolemia may have come into physician's mind more readily than other diagnosis even because they were confirmed by congruent physical findings (cold extremities, plane jugulars, sinusal tachycardia, etc). A “representativeness bias” took place. Representativeness
2032 occurs when a clinical condition is considered unlikely unless the presentation is prototypical of it. As fitting most but not all of available data, septic shock was considered the prominent diagnosis. On the contrary, cardiac tamponade was not taken into account because typical signs were absent. No other competing diagnosis was hypothesized, neither when chest x-ray reported both an unexplained mild cardiomegaly and bilateral pleural effusion. Physician stood anchored to his initial judgment and prematurely closed the case. “Anchoring” is the tendency to stick with the initial impression and not to adjust it according to further data. As in this case, anchoring goes often together with the confirmation bias (when physicians consider only data consistent with their hypothesis while the others are scotomized) and the “premature closure” (ceasing to look for differential diagnosis). Similarly, in case 2, heuristics of representativeness (congruent clinical picture with a previous episode of deep venous thrombosis), confirmation bias (a chest computed tomography was ordered to confirm the diagnosis but a history of recurrent urinary infection passed unnoticed) and premature closure are clear. A further cognitive bias highlighted through this case is “search satisfying.” It occurs when the diagnostic reasoning stops as soon as something is found. Unfortunately, diagnostic findings may appear as accidental discoveries unrelated to the present illness, especially using new imaging technologies. In our case, the patient was diagnosed with pulmonary embolism, but no US signs of obstructive shock were discovered. In patients with pulmonary embolism presenting with shock, the absence of US signs of right ventricular dysfunction excludes pulmonary embolism as a cause of hemodynamic instability [11]. As pulmonary embolism was initially confirmed by the computed tomography, a sort of “blind obedience” was put by the emergency physicians who did not look for other details. Blind obedience is defined as the “undue deference to either authority or technology” [7]. Blind obedience, confirmation bias, search satisfying and premature closure appear strictly linked in this case. US examination and critical reappraisal of the whole story highlighted some anamnestic details previously unnoticed and prevented unnecessary therapies. Case 3 underscores how physicians tend to persist on the same hypothesis if it has been diagnosed several times before. This is the so called “posterior probability error”: a history of recurrent diastolic heart failure lowered the “a posteriori” probability for any diagnosis different from heart failure [6,8]. Probably a certain grade of both confirmation bias and blind obedience were due to the x-rays findings, not considering that x-rays may be misleading in supine patients, radiographic signs of pneumonia need time to appear, and sometimes, radiography remains negative. On the contrary, US may be useful in the diagnosis of alveolar consolidation, also for patients with radio-occult pneumonia [12,13]. Furthermore, US finding of typical diffuse B-lines pattern shows high sensitivity resulting a rule-out test for the
F. Elia et al. alveolar-interstitial syndrome and allowing to distinguish between cardiogenic and noncardiogenic dyspnea [14,15]. Several strategies have been proposed to counteract cognitive errors. Literature has invoked many debiasing techniques such as metacognition, prospective hindsight, comprehensive differential diagnosis, pattern recognition, consideration of the opposite, checklists implementation or proper use of follow-up [3,4]. Some of these have proved to ameliorate both patients' outcomes and length of stay in the intensive care unit [5]. Their common denominator is to enable the physician to critically reexamine, step by step, the cognitive paths that has lead him to take some decision. Here, we propose a different approach to limit such predictable bias: the judicious use of “visual medicine.” Emergency goaldirected, focused US is relatively easy learning, repeatable, low cost; it does not use ionizing radiation and helps to diagnose life-threatening conditions, guide invasive procedures, treat medical emergencies, and monitor pathologic changes [16]. Some have argued the US probe as an extension of the stethoscope and point-of-care US as the visual inspection beyond the physical examination [14]. In the 3 presented cases, US provided a valuable help to the definition of the right diagnosis. In the first, it discriminated between septic shock and cardiac tamponade, whose specific characteristics were lacking (no jugular distension and normal ECG voltages) and further guided an evacuative pericardiocentesis. In the second, it fully defined a massive pulmonary embolism as not being the cause of the shock (no US signs of acute right heart failure) and lead to the reappraisal of other competing causes of hemodynamic instability. In the last, it provided a visual differentiation between 2 opposite causes of dyspnea and guaranteed the institution of a life-saving therapy, even before classic imaging techniques had turned positive. Nevertheless, US may be exposed to the same pitfalls and has its own limitations. First, both hypothesis generation and differential diagnosis process should drive the “proper” use of goal-directed, focused US as with any other test. This means that it must be implemented whenever clear questions need to be addressed and US is technically able to answer these ones. If the first requirement should not be met, either “incidental” or meaningless US findings might divert the physician from the right interpretation of the clinical picture and promote further unnecessary or even dangerous examinations. In the 3 presented cases, US properly fulfilled 3 of 5 tasks that traditionally have been assigned to its application in the emergency setting: diagnostic, procedure guidance and symptom or sign based [16]. However, a lot of literature has assessed the effectiveness of clinical US and newer evidence is available for several core emergency US applications (trauma, shock, dyspnea, chest pain, etc). Moreover, the technical applicability of US has several meanings. Like any other test, it has definite sensibility and specificity in the identification of any clinical picture; these characteristics are even more variable, as it is an operatordependent technique. Therefore, like any other practical or
Ultrasound, cognitive errors and emergency medicine cognitive debiasing technique, US needs specific training. It does not work outside the “Bayesian model”: ultrasound findings should always be interpreted in terms of likelihood ratios and posterior probabilities according to both the clinical picture and the epidemiology of diseases; nevertheless, US can itself elicit alternative diagnosis, give further information to make tasks easier and provide reliable feedbacks. We think that the clinical decision-making procedure should be a continuous process of generation of competing hypothesis, asking for proper examinations, gathering new data according to them and interpreting information with respect to both previous and epidemiologic ones to formulate a diagnosis of probability. Continuous reappraisal and critical interpretation of all information are the mainstay of both the diagnosing process and the conscious use of heuristics. Ultrasonography may deserve an important role in overcoming our cognitive limits as any other debiasing strategy. In the same way, its correct application requires adequate training, knowledge of its limitation and deliberate critic.
References [1] Croskerry P, Norman G. Overconfidence in clinical decision making. Am J Med 2008;121:S24-9. [2] Berner ES, Graber ML. Overconfidence as a cause of diagnostic error in medicine. Am J Med 2008;121(5 Suppl):S2-23.
2033 [3] Croskerry P. Cognitive forcing strategies in clinical decision making. Ann Emerg Med 2003;41:110-20. [4] Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med 2003;78:775-80. [5] Ely JW, Graber ML, Croskerry P. Checklists to reduce diagnostic errors. Acad Med 2011;86(3):307-13. [6] Gorini A, Pravettoni G. An overview on cognitive aspects implicated in medical decisions. Eur J Intern Med 2011;22:547-53. [7] Redelmeier DA. Improving patient care. The cognitive psychology of missed diagnoses. Ann Intern Med 2005;142:115-20. [8] Croskerry P. The cognitive imperative: thinking about how we think. Acad Emerg Med 2000;7:1223-31. [9] Kuhn GJ. Diagnostic errors. Acad Emerg Med 2002;9:740-50. [10] Adams JG, Bohan JS. System contributions to error. Acad Emerg Med 2000;7(11):1189-93. [11] Torbicki A, Perrier A, Konstantinides S, et al, ESC Committee for Practice Guidelines (CPG). Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC). Eur Heart J 2008;29: 2276-315. [12] Parlamento S, Copetti R, Di Bartolomeo S. Evaluation of lung ultrasound for the diagnosis of pneumonia in the ED. Am J Emerg Med 2009;27:379-84. [13] Soldati G, Testa A, Silva FR. Chest ultrasonography in lung contusion. Chest 2006;130:533-8. [14] Lichtenstein DA. Ultrasound in the management of thoracic disease. Crit Care Med 2007;35:S250-61. [15] Lichtenstein D, Meziere G. A lung ultrasound sign allowing bedside distinction between pulmonary edema and COPD: the comet-tail artifact. Intensive Care Med 1998;24:1331-4. [16] American College of Emergency Physicians. Emergency ultrasound guidelines. www.acep.org.