Diagnostic Imaging, Ultrasound and Interventional Radiology

Diagnostic Imaging, Ultrasound and Interventional Radiology

Hang Ho, MD and Terence O’Keeffe, MB ChB

Augusta University Medical Center, Augusta, GA, USA

  1. Which of the following patients is most likely to respond to intravenous fluid administration?

    1. A patient with a 5% increase in aortic flow velocity after passive leg raise.
    2. A patient with an IVC collapsibility index of (CI) 87%.
    3. A patient with hyperechoic reverberation artifacts at the pleura on ultrasound evaluation of the lungs.
    4. A patient whose right common carotid artery diameter did not significantly change with passive leg raise.
    5. An increase in systolic blood pressure of <10 points with passive leg raise.

    Determining which patients will respond favorably to fluid resuscitation is a key skill required in the critical care setting, but has been notoriously difficult. Bedside ultrasound has become an increasingly useful tool for assessment. Measurements that have been studied include IVC collapsibility index, aortic flow velocity, evaluation for pulmonary edema, and evaluation of common carotid artery diameter.

    An IVC CI close to 100% suggests that the patient will be highly likely to respond favorably to volume resuscitation. The IVC collapsibility index is one of the more frequently utilized measures and can be obtained with bedside ultrasound of the inferior vena cava. The IVC Collapsibility Index ranges from 0–100% and is described with the following equation:


    where the maximum and minimal vessel diameters are the diameters obtained during at least one full respiratory cycle. A IVC CI of 100% suggests high volume responsiveness, while an IVC CI approaching 0% suggests minimal/no volume responsiveness.

    A is incorrect. Aortic flow velocity is based on the premise that the left ventricular outflow tract diameter is relatively constant, and therefore any increase in flow through this area correlates to a proportionate increase in stroke volume. Therefore, a measurement of aortic flow velocity at the aortic root can be correlated with an increase in stroke volume. An aortic flow velocity increase of >14% after passive leg raise is associated with volume responsiveness. An increase <10% is associated with a high negative predictive value of volume responsiveness.

    B is the correct answer. An IVC CI approaching 0% suggests low volume responsiveness, while an IVC CI of 100% suggests minimal/no volume responsiveness.

    C is incorrect. This is a description of B lines, which are an ultrasound finding consistent with pulmonary edema. This patient would likely not benefit from additional IV fluid administration.

    D is incorrect. Significant carotid artery diameter increase with passive leg raise is correlated with volume responsiveness. No significant change would suggest that the patient is not intravascularly depleted.

    E is incorrect. Passive leg raise will increase systolic blood pressure at least transiently in a hypovolemic patient. A patient with fairly minimal increase in systolic blood pressure is unlikely to benefit from additional intravascular fluid administration.

    Answer: B

    Feissel M, Michard F, Mangin O, et al. Respiratory changes in aortic blood velocity as an indicator of fluid responsiveness in ventilated patients with septic shock. Chest 2001 Mar; 119(3):867–873.

    Hilbert T, Klaschik S, Ellerkmann R, et al. Common carotid artery diameter responds to intravenous volume expansion: an ultrasound observation. Springerplus 2016 Jun; 5(1):853.

    Pourmand A, Pyle M, Yamane D, et al. The utility of point‐of‐care ultrasound in the assessment of volume status in acute and critically ill patients. World Journal of Emergency Medicine 2019 Jul; 10(4):232–238.

  2. Which of the following findings on transcranial doppler ultrasound of the middle cerebral artery suggests a high risk of mortality and/or morbidity associated with traumatic brain injury?

    1. High mean velocity, high diastolic velocity, high pulsatility index
    2. Low mean velocity, high diastolic velocity, high pulsatility index
    3. Low mean velocity, low diastolic velocity, high pulsatility index
    4. High mean velocity, high diastolic velocity, low pulsatility index
    5. Low mean velocity, high diastolic velocity, low pulsatility index

    Transcranial doppler (TCD) is a noninvasive ultrasound (US) study used to measure cerebral blood flow velocity (CBF‐V) in the major intracranial arteries. It involves use of low‐frequency (≤2 MHz) US waves to insonate the basal cerebral arteries through relatively thin bone windows. Transcranial doppler of the middle cerebral artery is a modality used to predict prognosis related to traumatic brain injury. Mean velocity, diastolic velocity, and pulsatility index are measured to identify hypoperfusion, which is correlated with increased morbidity and mortality. Hypoperfusion on transcranial doppler is defined as the presence of two of the following:

    1. Mean velocity <35 cm/sec
    2. Diastolic velocity <20cm/sec
    3. Pulsatility index >1.4

    Therefore, the correct answer is C. Answers A, B, D, and E do not meet these criteria.

    Answer: C

    Santbrink HV, Schouten JW, Steyerberg EW, et al. Serial transcranial doppler measurements in traumatic brain injury with special focus on the early post‐traumatic period. Acta Neurochirurgica 2002 Nov; 144(11):1141–1149.

    Ziegler D, Cravens G, Poche G, et al. Use of transcranial doppler in patients with severe traumatic brain injuries. Journal of Neurotrauma 2017 Jan; 34(1):122–127.

  3. The use of the IVC collapsibility index (CI) collapsibility index for assessment of intravascular volume status would be least useful in which of the following scenarios?

    1. In a pregnant patient
    2. To predict post‐anesthesia hypotension
    3. In a patient with positive pressure ventilation
    4. In a septic patient
    5. In a patient with suspected PE

    IVC collapsibility index is one of several measures that can be obtained to assess volume status in a critically ill patient. In a spontaneously breathing patient, inspiration generates negative intrathoracic pressure which subsequently is transmitted to the central venous system. The intra‐abdominal inferior vena cava collapses on inspiration when the central venous pressure is lower than the intra‐abdominal pressure. Positive pressure ventilation conversely increases intrathoracic pressure during inspiration. Therefore, patients who are on positive pressure ventilation may not demonstrate inspiratory IVC collapsibility indices which correlate accurately with volume status. It is not recommended to use IVC CI to guide therapy or intervention in mechanically ventilated patients.

    Answers A, B, D, and E are all appropriate applications of the IVC collapsibility index.

    Answer: C

    Porter, TR, Shillcutt, SK, Adams MS, et al. Guidelines for use of echocardiography as a monitor for therapeutic intervention in adults: a report from the American Society of Echocardiography. Journal of the American Society of Echocardiography 2015; 28:40–56.

  4. A 63‐year‐old obese man is postoperative day 4 after exploratory laparotomy, sigmoidectomy, and end‐colostomy for perforated diverticulitis. He has been minimally mobile due to his body habitus. He develops sudden onset of lightheadedness and shortness of breath. Vitals are significant for sinus tachycardia to 120 bpm, hypotension to 87/60 mmHg, and pulse oximeter shows hypoxia to 78%. Chest x‐ray is unremarkable. Which of the following would confirm the diagnosis?

    1. Anechoic layer between the heart and pericardium on TTE
    2. IVC size <2.1 cm which collapses >50% during respiration
    3. Troponin level of 7.6
    4. CT of the chest with IV contrast
    5. Diffuse ST elevation across the lateral leads

    The scenario presented above is consistent with a pulmonary embolus with right heart strain. Pulmonary embolism should always be suspected in patients with major surgery or trauma and/or prolonged immobility. Typical presentation involves acute onset hypoxia, sinus tachycardia. Severe cases will present with hypotension and evidence of right heart strain on echocardiography demonstrated by RVIDD/LVIDD > 0.9. The pathognomic echocardiogram finding is S1Q3T3 (prominent S wave in lead I, Q wave and inverted T wave in lead III).

    A is not correct. This is a finding consistent with pericardial effusion. Pericardial effusion can present similarly but is unlikely to present with significant hypoxia.

    B is not correct. These values suggest hypovolemia and are not consistent with pulmonary embolism.

    C is not correct. While pulmonary emboli can present up to 50% of the time with elevated cardiac biomarkers, this finding is nonspecific and does not confirm a specific diagnosis without correlation with additional data.

    E. This is found in pericarditis, which classically presents as chest pain alleviated by sitting up or leaning forward associated with shortness of breath. However, it is unlikely to cause significant hypotension or hypoxia. The more likely diagnosis is pulmonary embolism, which would be confirmed by CT of the chest with IV contrast.

    Answer: D

    Levis JT . ECG diagnosis: pulmonary embolism. The Permanente Journal 2011; 15(4):75

    Porter, TR, Shillcutt, SK, Adams MS, et al. Guidelines for use of echocardiography as a monitor for therapeutic intervention in adults: a report from the American Society of Echocardiography. Journal of the American Society of Echocardiography 2015; 28:40–56.

  5. A 32‐year‐old helmeted man presents after a downhill skiing accident where he fell and struck the left side of his neck. Under which of the following circumstances would he have an absolute indication for CTA?

    1. Leforte I fracture
    2. Closed head injury with diffuse axonal injury and GCS <6
    3. Fracture of the spinous process of T1
    4. Isolated first rib fracture
    5. Unremarkable neurologic exam with small nonexpanding Zone II neck hematoma

    The diagnosis of blunt cerebrovascular trauma is essential in the workup of a patient with blunt trauma to the head and neck. The following are risk factors for blunt cerebrovascular trauma:

    High‐energy transfer mechanism associated with:

    • Displaced mid‐face fracture (LeForte II or III)
    • Basilar skull fracture with carotid canal involvement
    • Closed head injury consistent with diffuse axonal injury and GCS < 6
    • Cervical vertebral body or transverse foramen fracture, subluxation, or ligamentous injury at any level
    • Any fracture at C1‐C2
    • Near hanging with anoxia
    • Clothesline‐type injury or seat belt abrasion with significant swelling, pain or altered mental status

    A is incorrect. LeForte II and III are indications for CTA. A LeForte I fracture is a transverse fracture through the maxilla and pterygoid plates and therefore will not involve the carotid canals.

    B is the correct answer. Closed head injury with GCS < 6 and concern for diffuse axonal injury on imaging should prompt a CTA neck.

    C is incorrect. Thoracic spine injuries do not necessitate CTA of the neck. Furthermore, injuries such as spinous process fractures or transverse process fractures without ligamentous injury or involvement of the transverse foramen do not represent a high risk for BCVI. CTA is recommended in the setting of vertebral body fractures, fractures involving the transverse foramen, subluxation, or ligamentous injury at any cervical spine level.

    D is incorrect. Isolated first rib fractures are a relative, not absolute, indication for CTA neck.

    E is incorrect. A clothesline‐type injury does not mandate a CTA neck in a patient who remains neurologically unremarkable with no significant pain or altered neurologic exam.

    Answer: B

    Geddes AE, Burlew CC, Wagenaar AE, et al. Expanded screening criteria for blunt cerebrovascular injury: a bigger impact than anticipated. American Journal of Surgery 2016 Dec; 212(6):1167–1174.

    Western Trauma Association. Screening for and Treatment of Blunt Cerebrovascular Injuries Algorithm (2020). https://www.westerntrauma.org/western‐trauma‐association‐algorithms/screening‐for‐and‐treatment‐of‐blunt‐cerebrovascular‐injuries‐algorithm/references/

  6. An 18‐year‐old man who is hemodynamically normal presents after sustaining a gunshot wound to the posterior lower right thigh from a handgun. EMS reports brisk red bleeding on scene. On presentation, the patient has a nonpulsatile hematoma adjacent to the wound with palpable distal pulses bilaterally. ABI on the affected limb is 0.7. What is the next best step?

    1. Surgical exploration and vascular repair
    2. Interventional radiology consultation
    3. Observation and local wound care
    4. CTA of the affected extremity
    5. Vascular ultrasound

    Penetrating extremity trauma should always include assessment of the peripheral vasculature starting with pulse exam and ankle‐brachial indices. Hard signs of vascular trauma should prompt surgical exploration. In the absence of hard signs of vascular injury, the presence of an abnormal ABI should prompt further diagnostic evaluation either in the form of CTA or vascular ultrasound. CTA is indicated in this patient, who demonstrates several soft signs of peripheral vascular injury in the setting of an abnormal ABI (defined as less than or equal to 0.9).

    A is not correct. Immediate operative intervention is indicated in the setting of hard signs of vascular injury: (1) external arterial bleeding; (2) a rapidly expanding hematoma; (3) any of the classical signs of arterial occlusion (pulselessness, pallor, paresthesias, pain, paralysis = 5 “P”s); and (4) a palpable thrill/audible bruit.

    B is not correct. Interventional radiology consultation for therapeutic intervention is indicated in the setting of active extravasation or arteriovenous fistula with an injury to the profunda femoris, anterior tibial, posterior tibial, or peroneal arteries.

    C is not correct. Observation is only appropriate if no injury is demonstrated on imaging OR if the only injury identified is isolated occlusion of the profunda femoris, posterior tibial, anterior tibial, or peroneal artery.

    D is the correct answer. In the absence of hard signs of vascular injury, the presence of an abnormal ABI should prompt further diagnostic evaluation either in the form of CTA or vascular ultrasound. CTA is indicated in this patient, who demonstrates several soft signs of peripheral vascular injury in the setting of an abnormal ABI (defined as less than or equal to 0.9).

    E is not correct. While vascular ultrasound has been found to have excellent accuracy in identifying arterial injury with sensitivity ranging from 50–100% and specificity >95%, this modality’s utility is limited to use in centers where vascular ultrasound technicians and/or ultrasound‐experienced vascular surgeons are available. Therefore, in the practice setting described above, this would not be the best choice.

    Answer: D

    Biffl WL, Ray CE, Jr., Moore EE, Mestek M, Johnson JL, Burch JM . Noninvasive diagnosis of blunt cerebrovascular injuries: a preliminary report. The Journal of Trauma 2002; 53:850–856.

    Western Trauma Association. Evaluation and Management of Peripheral Vascular Injury Part 1 (2020). https://www.westerntrauma.org/western‐trauma‐association‐algorithms/evaluation‐and‐management‐of‐peripheral‐vascular‐injury/note‐m/

  7. A 23‐year‐old woman presents as a passenger in a high‐speed rollover MVC. Her presenting vitals are a heart rate of 90 bpm, blood pressure 130/85 mm Hg, respiratory rate 24 breaths/minute, and SaO2 98%. She has moderate left upper abdominal pain on exam without peritonitis. Her fast is negative. She proceeds to CT, where she is found to have a distal pancreatic parenchymal laceration with moderate peripancreatic edema. What is the next best step in management?

    1. Distal pancreatectomy
    2. MRCP
    3. Exploratory laparotomy with drainage
    4. Expectant management
    5. ERCP

    Findings as described above of peripancreatic edema and pancreatic laceration in the setting of blunt abdominal trauma are concerning for pancreatic ductal injury. In an unstable patient with abnormal hemodynamics, operative exploration should be pursued. In a stable patient where nonoperative intervention is an option, MRCP is the appropriate modality to evaluate for ductal injury and is less invasive than ERCP.

    A is not correct. Distal pancreatectomy is indicated for lacerations with high risk of ductal injury to the left of the SMV. However, in this stable patient with concerning findings for such an injury on CT, MRCP to better define the extent of the injury is preferable prior to proceeding to the OR.

    C is not correct. It is best to further define the nature of the injury with MRCP in this stable patient. Laparotomy with drainage is indicated if the patient has indications for emergent laparotomy, such as refractory hemodynamic instability on presentation or peritonitis, and is subsequently found to have a low‐risk laceration to the pancreas on exploration.

    D is not correct. Expectant management is appropriate in the setting of normal pancreas or mid peripancreatic edema, but not in the setting of a parenchymal laceration. The presence of a parenchymal laceration necessitates further investigation.

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Dec 15, 2022 | Posted by in CRITICAL CARE | Comments Off on Diagnostic Imaging, Ultrasound and Interventional Radiology

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