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Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension (SALVATION): A Practical Echo-guided Approach Proposal

Published:April 17, 2021DOI:https://doi.org/10.1053/j.jvca.2021.04.009
      Despite the valuable use of modern applications of perioperative ultrasound across multiple disciplines, there have been limitations to its implementation, restricting its impact on patient-based clinical outcomes. Point-of-care ultrasound evaluation of hypoxia and hypotension is an important tool to assess the underlying undifferentiated etiologies in a timely manner. However, there is a lack of consensus on the formal role of ultrasound during evaluation of perioperative hypoxia or hypotension. The previous ultrasound algorithms have adopted a complex technique that possibly ignore the pathophysiologic mechanisms underlying the conditions presenting in a similar fashion. The authors here propose a simple, sequential and focused multiorgan approach, applicable for the evaluation of perioperative hypotension and hypoxia in emergency scenarios. The authors believe this approach will enhance the care provided in the postanesthesia care unit, operating room, and intensive care unit.

      Key Words

      IN THE current era, point-of-care ultrasound is an essential tool for diagnosis, procedural guidance, and assessment of therapeutic management across multiple specialties. The popularity of point-of-care ultrasound has expanded as a useful adjunct in the perioperative arena as it can be deployed rapidly to a preanesthesia room, the operating room, or the post-anesthesia care unit (Video 1).
      • Bainbridge D
      • McConnell B
      • Royse C.
      A review of diagnostic accuracy and clinical impact from the focused use of perioperative ultrasound.
      ,
      • Yeh L
      • Montealegre-Gallegos M
      • Mahmood F
      • et al.
      Assessment of perioperative ultrasound workflow understanding: a consensus.
      Unlike a formal cardiology-based echocardiogram, which can often take 45-to-60 minutes, a focused, goal-directed, and multiorgan study can be performed in a shorter time span. Additionally, perioperative ultrasound offers a 35% reduction in medical expenses via increased diagnostic certainty, avoidance of radiology/cardiology consults, and subsequent expensive tests (computed tomography scan, magnetic resonance imaging), reduction in hospital stay, and fewer complications.
      • Melniker LA
      • Leibner E
      • McKenney MG
      • et al.
      Randomized controlled clinical trial of point-of-care, limited ultrasonography for trauma in the emergency department: the first sonography outcomes assessment program trial.
      ,
      • Shokoohi H
      • Boniface KS
      • Pourmand A
      • et al.
      Bedside ultrasound reduces diagnostic uncertainty and guides resuscitation in patients with undifferentiated hypotension.
      Despite the evidence demonstrating the cost-effective nature and protocolized use of transesophageal echocardiography (TEE) and transthoracic echocardiography (TTE) recommended by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists, its impact on patient-specific outcomes (morbidity and mortality) is limited due to its restricted implementation and lack of consensus on the formal role during evaluation of perioperative hypoxia or hypotension.
      • Fair J
      • Mallin M
      • Mallemat H
      • et al.
      Transesophageal echocardiography: guidelines for point-of-care applications in cardiac arrest & resuscitation.
      • Atkinson P
      • Bowra J
      • Milne J
      • et al.
      International Federation for Emergency Medicine consensus statement: sonography in hypotension and cardiac arrest (SHoC): An international consensus on the use of point of care ultrasound for undifferentiated hypotension and during cardiac arrest.
      • Hahn RT
      • Abraham T
      • Adams MS
      • et al.
      Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.
      • Mitchell C
      • Rahko PS
      • Blauwet LA
      • et al.
      Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults: Recommendations from the American Society of Echocardiography.
      Various subspecialty training programs exist for clinicians to train and acquire high levels of expertise in the use and interpretation of point-of-care ultrasound and echocardiography. The American Society of Anesthesiologists recently initiated a Diagnostic POCUS Certificate Program, with similar initiative by The National Board of Echocardiography, allowing critical-care-trained physicians to sit for a special certification examination, both reflecting the growing use and need for standardized practice. For successful management of undifferentiated hypotension or hypoxia in any setting, in addition to the knowledge and skills required, an institutional safety culture has to be implemented into education, training, and everyday practice as a standard of care.
      • Mahmood F
      • Matyal R
      • Skubas N
      • et al.
      Perioperative ultrasound training in anesthesiology.
      ,
      • Bhagra A
      • Tierney DM
      • Sekiguchi H
      • et al.
      Point-of-Care ultrasonography for primary care physicians and general internists.
      A more focused level of training and proficiency can be achieved in a short time and can serve as an extremely valuable tool for the assessment of many life-threatening clinical scenarios.
      Many practical algorithms have been developed for the evaluation of circulatory and respiratory failure.
      • Lichtenstein DA.
      BLUE-protocol and FALLS-protocol: Two applications of lung ultrasound in the critically ill.
      • Seif D
      • Perera P
      • Mailhot T
      • Riley D
      • Mandavia D.
      Bedside ultrasound in resuscitation and the rapid ultrasound in shock protocol.
      • Manson W
      • Mike Hafez N
      The rapid assessment of dyspnea with ultrasound: RADiUS.
      The previously published ultrasound protocols have adopted a complex technique to evaluate multiple systems at a time, with less focus on underlying pathophysiologic mechanism and presenting symptoms.
      • Lichtenstein DA.
      BLUE-protocol and FALLS-protocol: Two applications of lung ultrasound in the critically ill.
      ,
      • Seif D
      • Perera P
      • Mailhot T
      • Riley D
      • Mandavia D.
      Bedside ultrasound in resuscitation and the rapid ultrasound in shock protocol.
      ,
      • Moitra VK
      • Einav S
      • Thies K-C
      • et al.
      Cardiac Arrest in the Operating Room.
      The authors here believe incorporation of clinical symptoms and the underlying pathophysiology with the ultrasound examination enhances the critical thinking process of evaluating a differential diagnosis. Thus, the authors propose a comprehensive yet simple, focused, and multiorgan evaluation algorithm to aid in the identification of causes of hypoxia and hypotension and to serve as a guide to therapeutic management.

      Proposed Algorithm

      The proposed “simplified” algorithm based on divisions via arms of algorithm for evaluation of both hypoxia or hypotension incorporates three steps for assessment of hypotension by estimation of contractility, afterload, and preload, as well as evaluation of hypoxia through lung windows (Fig 1, Fig 2). The workflow represents a pathophysiologic and symptom-based assessment of vital organs and a differential diagnosis based on ultrasound findings in patients. The algorithm is meant to simplify the workflow and reinforce the thought process of a comprehensive differential diagnosis of the rescuer-provider in situations in which time is a priority. The targeted audience for this algorithm includes all perioperative physicians involved in the care of patients, with identification of major dysfunction as the main goal of this protocol.
      Fig 1
      Fig 1Appropriate views of simplified algorithm for evaluation of perioperative hypoxia and hypotension (Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension [SALVATION]).
      Fig 2
      Fig 2Sequence of simplified algorithm for evaluation of perioperative hypoxia and hypotension (SALVATION). Abbreviations: DVT, deep vein thrombosis; LV, left ventricle; EDA, end-diastolic area; EPSS, mitral valve E-point septal separation; ESA, end-systolic area; IVC, inferior vena cava; MAPSE, mitral annular plane systolic excursion; RV, right ventricle; S’, systolic excursion velocity; SALVATION, Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension; TAPSE, tricuspid annular plane systolic excursion.

      Step 1: Contractility and Afterload Evaluation

      Contractility

      Focused ultrasound demonstrates potential causes of hemodynamic instability, provides key pathophysiologic data, and assists in management. Urgent assessment of contractility of the heart is based on visual qualitative assessment (eye-balling) and semiquantitative measures. The standard views to evaluate the contractility include parasternal long- and short-axis views (scanned from base to apex via tilting the probe), the apical four-chamber (obtain apical three-chamber and two-chamber views if unclear or suspicion of wall motion abnormality), and the subcostal four-chamber views (Fig 3). Qualitative assessment involves evaluation of both right and left ventricles for size, shape, and function.
      Fig 3
      Fig 3Step 1: Contractility and afterload evaluation of simplified algorithm for evaluation of perioperative hypoxia and hypotension (SALVATION) protocol. Abbreviations: DTA, descending thoracic aorta; DVT, deep vein thrombosis; IAS, interatrial septum; IVS, interventricular septum; IVC, inferior vena cava LA, left Atrium; LV, left ventricle; LVOT, left ventricular outflow tract; PMA, point of maximal impulse; RA, aight atrium; RV, right ventricle; SALVATION, Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension.

      Left Ventricle (LV)

      The shape of a normal left ventricle (LV) is ellipsoid with a conical apex in a longitudinal view with a circular appearance in transverse cross-section view. Measurements for LV size commonly are performed for end-diastole (EDA) and end-systole (ESA). Regional and global left ventricular function provides information for diagnostic, incrementally prognostic, as well as therapeutic options. The LV function assessment with eye-balling is based on wall thickening and circumferential shortening and can be divided into normal function (ejection fraction [EF] >55%), mild (EF 41%-55%), moderate (EF 31%-40%), and severe dysfunction (EF <30%).
      • Margossian R
      • Schwartz ML
      • Prakash A
      • et al.
      Comparison of echocardiographic and cardiac magnetic resonance imaging measurements of functional single ventricular volumes, mass, and ejection fraction (from the Pediatric Heart Network Fontan Cross-Sectional Study).
      There is evidence that eye-balling LV function can be as effective as Simpsons method and quantitative assessment.
      • Gudmundsson P
      • Rydberg E
      • Winter R
      • Willenheimer R.
      Visually estimated left ventricular ejection fraction by echocardiography is closely correlated with formal quantitative methods.
      Good ventricular contractility is identified with optimal wall thickening and circumferential shortening during systole. Taking into account the time available, additional quantitative measures can be employed to either confirm the visual findings of hypodynamic LV or to further quantify the severity of ventricular dysfunction. The preference of any of these techniques relies upon the comfort level and choice of the provider. The global LV systolic function can be estimated by fractional shortening that is based on radius change of the LV internal diameter determined in parasternal long-axis at EDA and ESA derived from 2D measurements or M-mode echocardiography. Normal is defined as 25% change in radius on M-Mode or >18% change on 2D measurements. The caveat to use of fractional shortening is the measurement of myocardial function in only one plane, less reliability with regional wall motion abnormalities, and easily affected by preload and afterload.
      • Lang RM
      • Badano LP
      • Mor-Avi V
      • et al.
      Recommendations for cardiac chamber quantification by echocardiography in adults: An update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.
      Another alternative for estimating LV function is the mitral valve E-point septal separation (EPSS). Normally, the anterior leaflet of the mitral valve should approach or touch the interventricular septum in early diastole and is defined as the E-point of the mitral valve cycle. The amount of separation between the septum and leaflet of the valve in early diastole is defined as the EPSS.
      • McKaigney CJ
      • Krantz MJ
      • La Rocque CL
      • et al.
      E-point septal separation: A bedside tool for emergency physician assessment of left ventricular ejection fraction.
      Particularly, a measurement greater than 7 mm has been demonstrated to predict poor left ventricular function.
      • Massie BM
      • Schiller NB
      • Ratshin RA
      • et al.
      Mitral-septal separation: New echocardiographic index of left ventricular function.
      A limitation of EPSS is that mitral valve disease or severe aortic regurgitation can elevate this measurement without the presence of impaired LV EF. An alternate method as a surrogate of the left ventricular function is the mitral annular plane systolic excursion, which measures the lateral mitral annular movement toward the apex during LV systole.
      • Bergenzaun L
      • Öhlin H
      • Gudmundsson P
      • et al.
      Mitral annular plane systolic excursion (MAPSE) in shock: A valuable echocardiographic parameter in intensive care patients.
      It is performed in an apical four-chamber view by placing the M-mode cursor parallel to the LV walls. The distance moved by the mitral annular plane toward the apex is measured from the lowest point at EDA to aortic valve closure at ESA. Normal values are greater than 8 mm and lie within an acceptable range of 12 ± 2 mm. However, it is less reliable with wall motion abnormality and is only representative of longitudinal function of the LV. Additionally, peak systolic velocity of annular displacement (S’) by tissue Doppler is another measure of contractility and global LV function. Peak mitral annular descent is measured in the apical view. Normal peak lateral mitral annular systolic velocity greater than 5.4 cm/s predicts an EF of >50%.
      • Chengode S.
      Left ventricular global systolic function assessment by echocardiography.
      Severely depressed LV function can lead to pulmonary edema and congestion that can be evaluated for further evidence by identification of lung rockets (three or more B-lines) or bilateral B-line pattern.
      • Lichtenstein DA.
      BLUE-protocol and FALLS-protocol: Two applications of lung ultrasound in the critically ill.
      Moreover, the presence of left-sided valvular abnormality (regurgitant or stenotic) can be assessed by eye-balling the appearance and mobility of the valve. The severity of valvular lesions can be evaluated further for regurgitant lesions through visualizing the 2D findings (increase in atrial or ventricular size, hyperdynamic LV) and qualitative color-Doppler imaging (jet area and width of vena contracta). The severity of stenotic lesions is evaluated based on 2D findings of valve opening and leaflet mobility, valvular calcification, and thickness.
      • Bhavnani SP
      • Sola S
      • Adams D
      • et al.
      A randomized trial of pocket-echocardiography integrated mobile health device assessments in modern structural heart disease clinics.
      The patent foramen ovale also can be evaluated in the subcostal window utilizing color-Doppler imaging either at rest or employing maneuvers.

      Right Ventricle (RV)

      The RV has a pyramidal shape on a longitudinal view and a crescent shape on a transverse view. A normal RV appears to be two-thirds in size of the LV on qualitative assessment. Because of the complex anatomy of the RV creating interdependence with the LV, its functional assessment includes septal wall motion analysis as well. Septal wall motion is best assessed in parasternal short-axis view. Normally, the LV protrudes into the RV during systole. Motion physiology of the RV involves shortening of the long axis from base to apex, radial/inward movement of the free wall, and circumferential contraction of the RV outflow tract.
      • Haddad F
      • Hunt SA
      • Rosenthal DN
      • et al.
      Right ventricular function in cardiovascular disease, part I: Anatomy, physiology, aging, and functional assessment of the right ventricle.
      Taking into account the time available, additional quantitative measures can be employed to either confirm the visual findings or further quantify the severity of RV dysfunction. Tricuspid annular planar systolic excursion is a technique that can be used to assess longitudinal systolic function of the right ventricle. It is performed in a similar fashion to the mitral annular plane systolic excursion but the M-mode cursor is placed along the RV free wall as perpendicular to the lateral tricuspid annulus as possible. Tricuspid annular planar systolic excursion >1.6 cm is considered the lower normal limit.
      • Haddad F
      • Hunt SA
      • Rosenthal DN
      • et al.
      Right ventricular function in cardiovascular disease, part I: Anatomy, physiology, aging, and functional assessment of the right ventricle.
      Another alternative method for evaluation of RV function is systolic excursion velocity S'. It is acquired by placing the pulsedDoppler or colorDoppler on the lateral tricuspid annulus to obtain the longitudinal velocity of tricuspid annulus and basal free wall segment during systole. S’ is >9.5 cm/s is considered the normal range.
      • Choudhary G
      • Malik AA
      • Stapleton D
      • et al.
      Assessment of right ventricle by echocardiogram.

      Afterload

      To identify causes leading to hypotension or hypoxia, evaluation of afterload on the heart is necessary. Since the RV is a thin-walled chamber, it is particularly sensitive to high afterload downstream and leads to ventricular dysfunction with volume or pressure overload. In addition, RV overload affects LV diastolic function, leading to higher filling pressures. The flattening of the interventricular septum occurs in volume or pressure overload of the RV, forming a D-shaped LV at EDA or ESA, respectively.
      • Kaul S.
      The interventricular septum in health and disease.
      Acute increases in both pressure and volume afterload on RV are correlates of massive pulmonary embolism. The typical ultrasound findings of pulmonary embolism include a dilated RV, D-shaped LV on parasternal short-axis view due to deflection of the interventricular septum toward the left from the right due to higher pressures, McConnell sign (akinesis of the free wall of RV with apical sparing), and possibly a hyperechoic shadow of thrombus (Fig 4).
      • Oh SB
      • Bang SJ
      • Kim MJ.
      McConnell's sign; a distinctive echocardiographic finding for diagnosing acute pulmonary embolism in emergency department.
      If the pulmonary embolism findings are present, evaluation of deep venous thrombosis can be performed by simple compression of bilateral femoral and popliteal veins using a linear transducer. Veins are compressed in a transverse plane with a downward pressure to obliterate the lumen. A deep venous thrombosis is suspected if the anterior and posterior walls fail to touch each other (Fig 5). Rarely, intracardiac masses, such as atrial myxoma, also can cause obstruction of flow and increase the afterload on the left ventricle. Another cause of unexplained hypotension is dynamic obstruction of the left ventricular outflow tract, also known as "systolic anterior motion". The echocardiographic findings include systolic motion of the mitral valve toward the interventricular septum on 2D and M-mode, and turbulent flow in the left ventricular outflow tract on color-flow Doppler. Low afterload can be identified via the kissing papillary muscle sign accompanied by a normal ventricular EDA and small ESA, which are reflective of a hyperdynamic ventricle and peripheral vasodilation. When the internal walls of the ventricle or the papillary muscles can be seen touching each other during systole, this is referred to as the "kissing papillary muscle sign". These signs of low afterload could be seen in early sepsis, anaphylaxis, or neurogenic shock. Postoperatively, the intensive care unit team may face challenges in employment of TTE due to the site of surgery. However, the availability of different views can be used to gain information of hemodynamic status, such as the subcostal fourchamber, which can be used in cardiac surgery patients; while parasternal views are accessible in patients with prior abdominal surgery.
      Fig 4
      Fig 4Abnormal findings seen in tamponade, pulmonary embolism, and tension pneumothorax. Abbreviations: IVC, inferior vena cava; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle; TAPSE, tricuspid annular plane systolic excursion.
      Fig 5
      Fig 5Step 1: Deep Venous thrombosis evaluation in a simplified algorithm for evaluation of the perioperative hypoxia and hypotension (SALVATION) protocol. Abbreviations: DVT, deep vein thrombosis; IVC, inferior vena cava; SALVATION, Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension.

      Step 2: Preload Evaluation

      Preload Status

      During the evaluation of unexplained hypotension, it is mandatory to rapidly assess the preload status (Fig 6, Fig 7). Estimation of the volume status can be performed by the size of the ventricles, kissing papillary muscles, ventricular EDA and ESA. The size of the ventricles can be estimated in apical four-chamber and parasternal views, whereas kissing papillary muscles and assessment of EDA/ESA are best estimated in the parasternal short-axis mid-papillary view.
      • Franchi F
      • Vetrugno L
      • Scolletta S.
      Echocardiography to guide fluid therapy in critically ill patients: check the heart and take a quick look at the lungs.
      If this is accompanied with decreased EDA, it is considered a sign of hypovolemia (Fig 8). An estimate of fluid status also can be made by evaluation of the inferior vena cava (IVC) in the subcostal IVC view. The respiratory variation seen in a spontaneously breathing patient is such that IVC collapses on inspiration and distends on expiration due to shifts in intrathoracic pressure. The reverse happens in patients on mechanical ventilation where IVC distends on inspiration. M-mode Doppler placed on the IVC can quickly document the dynamic change of the vessel's diameter during the respiratory cycle. IVC with <2 cm diameter and inspiratory collapse >50% usually signify reduction in preload. However, prior treatment with vasodilators or diuretics or patients on mechanical ventilation should be taken into consideration with assessment of the IVC.
      Fig 6
      Fig 6Step 2: Preload evaluation of simplified algorithm for evaluation of perioperative hypoxia and hypotension (SALVATION) protocol. Abbreviations: ICS, intercostal space; IVC, inferior vena cava; RA, right atrium; SALVATION, Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension.
      Fig 7
      Fig 7Step 2: Preload evaluation of the abdominal aorta in a simplified algorithm for evaluation of perioperative hypoxia and hypotension (SALVATION) protocol. Abbreviations: AAA, abdominal aortic aneurysm; Ao, aorta; CT, celiac trunk; HA, hepatic artery; SA, splenic artery.
      Fig 8
      Fig 8Abnormal findings seen in hypovolemia and sepsis. Abbreviations: EDA, end-diastolic area; ESA, end-systolic area; IVC, inferior vena cava; LV, left ventricle; RV, right ventricle; SALVATION, Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension.

      Source of Preload Reduction

      After evaluation of the preload has been carried out, the next step is to identify the cause of reduction in preload if present. The reduction in preload can be due to either concealed blood loss or collections of fluid in peritoneal, pericardial, and pleural cavities. The peritoneal cavity can be evaluated for the presence of collection of fluid with the FAST examination. The scan constitutes a standard three-view (right upper quadrant, left upper quadrant, and pelvis) examination of the abdomen to evaluate free fluid. Specific views incorporate the space between the liver and kidney (hepatorenal space or Morison pouch), the area around the spleen, and the area around and behind the bladder (pouch of Douglas). Free intraperitoneal fluid is represented by a dark or anechoic area in any of these potential spaces. These areas correspond to the most dependent areas of the peritoneal cavity in a supine patient. Because the FAST examination relies on the patient's position, it should be taken into account while interpreting the examination. A Trendelenburg position can shift the fluid to the upper abdominal regions, while an upright position can transfer the fluid to the pelvis. If free fluid is detected, the possibility of acute hemorrhage from hepatic or splenic injury, ruptured aorta, or ruptured ectopic pregnancy has to be considered. Particularly, if aortic aneurysm and dissection are suspected, the abdominal aorta is scanned from the epigastrium down to the iliac bifurcation. A maximal diameter >3 cm suggests an abdominal aortic aneurysm. The presence of an echogenic intimal flap along the course of THE aorta suggests dissection that can be confirmed further with distinct blood flow on color-flow Doppler. Patients with ascites can confound this assessment as it will appear the same as acute bleeding.
      Fluid collection also can be present in the thorax in the form of pleural effusion or hemothorax. The thoracic cavity is evaluated by aiming the probe above the diaphragm and visualizing the lung for dark anechoic areas seen in the supradiaphragmatic view as well as ‘spine sign’, which is visualization of thoracic vertebral bodies above the diaphragm through the fluid medium.
      • Ahmed AA
      • Martin JA
      • Saul T
      • Lewiss RE.
      The thoracic spine sign in bedside ultrasound: Three cases.
      Another cause of decreased preload includes acute pericardial effusions causing cardiac tamponade. Sonographic characteristics of tamponade include early systolic right atrial collapse and early diastolic right ventricular collapse, reduced EDA and/or ESA, and presence of an echogenic fluid in the pericardial cavity.

      Step 3: Hypoxia Evaluation

      Direct approach using lung ultrasound can address pulmonary causes of unexplained hypoxia (Fig 9). In the absence of lung rockets of pulmonary edema from a left-sided heart anomaly, there is a need to evaluate the pulmonary etiology of respiratory failure. The pulmonary views are obtained bilaterally in the anterior chest. The normal lung sonographic findings include normal lung sliding (to-and-fro movement of the pleural line that spreads homogeneously generating the seashore sign in M-mode), few comet-tails or B-lines (discrete, vertical, hyperechoic reverberation artifacts that arise from the pleural line), and A lines that are equidistant, hyperechoic, horizontal lines arising below the pleural line. Lung consolidations can be an underlying etiology of hypoxia. The sign for consolidation is the shred sign defined as the irregular border between the consolidated and aerated lung.
      Fig 9
      Fig 9Step 3: Hypoxia evaluation of simplified algorithm for evaluation of perioperative hypoxia and hypotension (Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension [SALVATION]) protocol.
      Tension pneumothorax can also present with hypoxia in a patient with hemodynamic instability. Its characteristic sonographic findings include absent lung sliding, prominent A-lines, lung point, and absent lung pulse on the left side.
      • Husain L
      • Wayman D
      • Carmody K
      • et al.
      Sonographic diagnosis of pneumothorax.
      Lung point is defined as the junction between a sliding lung and absent sliding, and its identification is 100% specific for pneumothorax (Fig 4).
      • Lichtenstein D
      • Mezière G
      • Biderman P.
      The “lung point”: An ultrasound sign specific to pneumothorax.
      The presence of either lungsliding or comet-tail artifact suggests parietal and visceral pleura are in contact and excludes pneumothorax. The associated echocardiographic findings include hyperdynamic LV, dilated IVC, and reduced ventricular EDA and/or ESA.

      Case Example

      A 60-year-old man, with a history of coronary artery disease and type 2 diabetes mellitus, presented to the operating room for coronary artery bypass grafting. The patient was intubated and a central line was placed using ultrasound guidance in the left internal jugular vein. Postoperatively, in the postanesthesia care unit, the patient's blood pressure decreased to 60/20 mmHg and oxygen saturations dropped to 94% on 2 L of oxygen. Bedside TTE for ventricular contractility demonstrated a hyperdynamic LV. The preload and afterload assessment revealed a dilated IVC and reduced EDA and/or ESA. The lung ultrasound also was performed and revealed absence of lung sliding, absent B-line artifacts, presence of prominent A-lines, and lung point on the left side. Left-sided pneumothorax was suspected, and needle decompression was performed with subsequent chest tube placement.

      Training Model

      A multimodal education program on Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension (SALVATION) protocol is devised to impart baseline knowledge and develop workflow and motor skills for practical application of this approach. A similar approach to prior courses developed by the authors’ team
      • Matyal R
      • Mitchell JD
      • Mahmood F
      • et al.
      Faculty-focused perioperative ultrasound training program: a single-center experience.
      • Mitchell JD
      • Montealegre-Gallegos M
      • Mahmood F
      • et al.
      Multimodal perioperative ultrasound course for interns allows for enhanced acquisition and retention of skills and knowledge.
      • Mahmood F
      • Bortman J
      • Amir R
      • et al.
      Training Surgical residents for ultrasound-guided assessment and management of unstable patients.
      for multidisciplinary groups and present in prior literature
      • Sanders JA
      • Navas-Blanco JR
      • Yeldo NS
      • et al.
      Incorporating perioperative point-of-care ultrasound as part of the anesthesia residency curriculum.
      • Ramsingh D
      • Rinehart J
      • Kain Z
      • et al.
      Impact assessment of perioperative point-of-care ultrasound training on anesthesiology residents.
      • Ramsingh D
      • Bronshteyn YS
      • Haskins S
      • et al.
      Perioperative point-of-care ultrasound: From concept to application.
      can be utilized to gain knowledge via online web-based interactive modules followed by the workflow and motor skills hands-on practice on haptic, mixed-reality simulators to achieve a level of proficiency in this specific approach. This innovative teaching program offers educational training without any risk to the patient or consequences of failure (the lack of need for long-duration in-person training, enabling perioperative physicians to learn new protocols while upholding social distancing policy). The modules incorporate illustrations, video clips, and in-module questions to improve engagement of the viewer. It is necessary that trainees are taught integration of ultrasound findings with clinical scenario because there is a possibility of the artifacts with ultrasound imaging. Previously, the authors successfully have trained surgical residents using the similar approach for ultrasound-guided evaluation of hemodynamic instability.
      • Mahmood F
      • Bortman J
      • Amir R
      • et al.
      Training Surgical residents for ultrasound-guided assessment and management of unstable patients.
      The target audience of the SALVATION training program includes multidisciplinary perioperative clinicians at multiple levels of training (midlevel providers, medical students, residents, and attending physicians). The authors have incorporated the SALVATION training, along with the education on portable ultrasound probe such as the Butterfly iQ handheld probe (Butterfly Network, Inc, Guilford, CT) and VScan Extend handheld ultrasound dual probe (GE Healthcare, Chicago, IL). Portability of these devices allows improved feasibility in protocol implementation and offers integrated teleguidance from a trained practitioner to guide a novice or a junior colleague. The efficacy of the training program will be evaluated using cognitive knowledge tests at the baseline and end of the program, along with application of knowledge, workflow understanding, and manual skills on live human models and simulators in an objective structured clinical examination at the end of training. To further evaluate the transferability and impact on clinical management, a formal structured reporting system will be provided to faculty and trainees participating in the SALVATION training program. The data from the reporting system will be surveyed to assess if the findings from the use of the SALVATION protocol changed the preliminary diagnosis, affected clinical management, and changed subsequent morbidity and mortality outcomes in the future.
      The limitations to the superiority of the current SALVATION training model over other ultrasound protocols available in the prior literature included the lack of objective metrics to determine its efficacy. Possible metrics to be evaluated comprise achievement of competency by participants as well, as the clinical transferability of protocol impacting the perioperative course of patients that needs to be addressed in future study. In addition, the challenges to implementation of the SALVATION training program are two-tier, with dependance on motivation by faculty to use ultrasound and motivation of institution to adopt for resident and faculty in-training sessions.

      Conclusions

      During evaluation and management of hypoxia and hypotension, efforts should be focused to direct the attention toward the optimization of the workflow of the perioperative ultrasound and echocardiography algorithm to assist the clinician in thinking through their differential diagnosis and initiating timely and targeted therapeutics. Its implementation into education, training, and everyday practice will promote a culture of institutional safety practices.

      Conflict of interest

      None.

      Appendix. Supplementary materials

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      Linked Article

      • A RUSH to SALVATION? Practical and Tested Ultrasound-Guided Evaluations of Critically Ill Patients Already Exist
        Journal of Cardiothoracic and Vascular AnesthesiaVol. 35Issue 12
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          We read with great enthusiasm the recently published article, “Simplified Algorithm for Evaluation of Perioperative Hypoxia and Hypotension (SALVATION): A Practical Echo-guided Approach Proposal,” by Fatima et al.1 We applaud the authors’ in-depth evaluation of a sequence of ultrasound images to assess for abnormal pathologies as sources of hypoxia and hypotension in the perioperative setting. The algorithm assesses for the presence or absence of critical pathology such as obstruction, extravascular blood, and pneumothorax.
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