Utility of Point-of-Care Ultrasonography in Diagnosing Submassive Pulmonary Thromboembolism in a Trauma Patient and Subsequent Anesthetic Management: Case Report and Literature Review

Abstract

Point-of-care ultrasonography is defined as ultrasonography brought to the patient's bedside and performed by the provider in real time. The clinician can use these real-time dynamic images immediately (rather than images recorded by a sonographer and interpreted later), allowing findings to be directly correlated with the patient's presenting signs and symptoms. Point-of-care ultrasonography is easily repeatable if the patient's condition changes. Over the past decade, the use of point-of-care ultrasonography has extended to emergency settings and intensive care units. The role of ultrasound in triage patients is not only limited to the Focused Assessment with Sonography for Trauma which includes assessment for hemoperitoneum and hemopericardium, it has also been used to detect the presence of hemothorax, pneumothorax, and intravascular filling status in a trauma patient. However, the use of ultrasonography in detecting pulmonary thromboembolism in trauma has not been commonly reported. We report a patient in whom submassive pulmonary embolism was detected by lung ultrasound and thereafter operated for bilateral open Grade III lower-limb fractures. The surgery was proceeded under bilateral ultrasound-guided femoral sciatic nerve block.

INTRODUCTION

Prehospital point-of-care ultrasound (POCUS) is revolutionizing the care of trauma victims, especially when applied in emergency settings. The role of ultrasound in triage patients is not only limited to the Focused Assessment with Sonography for Trauma (FAST) which includes assessment for hemoperitoneum and hemopericardium, but it has also been used to detect the presence of hemothorax, pneumothorax, and intravascular filling status (E-FAST).[1] The diagnosis of pulmonary embolism (PE) is often more troublesome in emergency settings, particularly when considered as a cause of sudden circulatory failure (so-called “massive” PE). For these unstable patients, the hazard of transportation to the computed tomography (CT) scanner in order to exclude PE is not insignificant. Furthermore, it may not be possible in patients with known allergy to contrast media, severe renal insufficiency, and pregnant women[2] to undergo CT pulmonary angiography (CTPA) for early detection of PE. In such settings, POCUS has proved to be a valuable alternative diagnostic tool. We report the utility of point-of-care ultrasonography in successfully diagnosing submassive pulmonary thromboembolism in a triage patient and subsequent anesthetic management for bilateral open Grade IIIB lower-limb fractures.

CASE REPORT

The consent of the patient was obtained before publishing this report. A 35-year-old male, weighing 86 kg, presented with multiple fractures of bilateral upper and lower limbs following road traffic accident. On examination, he was fully conscious, cooperative having respiratory rate of 38 breaths per minute, heart rate 104 beats per minute and blood pressure 142/76 mm of Hg in supine position. His room air saturation was 85% which increased to 100% on ventimask having FiO2 of 0.6. On auscultation, fine crackles were present in bilateral lung fields. His routine blood investigations showed hemoglobin – 8 g/dL, platelet count – 1.3 lakhs, and total lymphocyte count – 8800 μL^{− 1}, and room air arterial blood gas (ABG) showed pH – 7.408, PaO₂– 48.5 mmHg, PCO₂– 34.3 mmHg, HCO₃– 21.2 mEq/L, and Base excess – −2.7. Upper and lower limb roentgenograms revealed a closed fracture of left shaft of the humerus and open grade IIIB fractures of left both bone leg and right fourth and fifth metatarsals. Chest roentgenogram showed patchy areas of consolidation throughout the right lung fields and left upper lobe [Figure 1].

Figure 1.

Chest X-ray of a patient at presentation. Patchy areas of consolidation seen throughout the right lung and left upper zone

Lung ultrasonography was done according to the SLESS protocol (six-field evaluation).[3] An “A” pattern was observed on all left lung fields, while on the right lung, an “A” pattern was observed on the apex, but some “B-” lines were seen in the anterior part of the lung base, and small subpleural consolidation was seen in more posterior position [Figure 2], thus raising suspicion of PE. Therefore, urgent CTPA was advised which confirmed the presence of pulmonary thromboembolism [Figure 3]. A plain CT scan of the brain showed tentorial subdural hemorrhage and left basal ganglia contusion which required conservative management.

Figure 2.

Lung ultrasonography picture of the patient showing subpleural consolidation (marked with red arrows) P - Pleura C - Costal shadow

Figure 3.

Computed tomography pulmonary angiography – Mediastinal window showing multiple filling defects in branches of the right pulmonary artery

Since the fractures required immediate fixation in view of their complex nature, it was decided to proceed the surgery under bilateral ultrasound-guided femoral sciatic nerve block. Ultrasound-guided bilateral sciatic nerve blocks were administered through popliteal approach.[4] Following individual sciatic nerve blocks, femoral nerve blocks were also given. Fifteen minutes following the second block, after confirming loss of temperature sensation up to L₂ level, the surgery was started. Supplemental O₂ administered through a venturi mask with FiO2 of 0.6 maintained a SpO₂ of 92%. Intraoperative hemodynamics remained within normal limits. However, the respiratory rate varied between 26 and 30 breaths per minute. Intraoperative ABG showed pH – 7.4, PaO₂– 135.7 mmHg, PCO₂– 33.8 mmHg, HCO₃– 20.4 mEq/L, and BE – −3.6 on FiO₂ of 0.6. The surgery was completed uneventfully in 1 h 30 min. Six hours postsurgery, injection Clexane 0.6 mg.kg^-1 twice daily was started. He was also started on tablet warfarin 4 mg once daily till international normalized ratio (INR) of 2 was achieved. Following INR of 2, injection Clexane was stopped, and the patient was discharged in stable condition.

DISCUSSION

Pulmonary thromboembolism is responsible for 200,000–300,000 hospital admissions worldwide every year.[5] Despite decades of research on PE, the diagnosis remains elusive in many situations, and the fatality rate remains significant.[5] PE can present with a multitude of complaints, and it is essential to keep a low threshold when deciding to include it in the differential. The availability of compact ultrasound machines helps in establishing early differential diagnosis of PE, which guides the further course of investigations and subsequent management.

Literature shows various case reports documenting the use of POCUS for early diagnosis of lung contusion and acute respiratory distress syndrome in blunt trauma patients.[6] However, in polytrauma patients without any chest injuries presenting in acute hypoxemia, POCUS can help to diagnose certain occult causes including acute respiratory distress syndrome and PE. Peripheral parenchymal consolidations are visible on lung ultrasound when an embolic vascular occlusion occurs.[7] These consolidations are due either to necrosis of lung parenchyma (infarction) or to atelectasis, related to the breakdown of surfactant with extravasation of blood.[7] The presence of A profile on lung ultrasonography with few subpleural consolidations is diagnostic of PE.[7] B-lines are usually absent or <3 in PE [Figures 4 and 5].[8]

Figure 4.

Lung ultrasonography showing multiple A-lines P - Pleura C - Costal shadow

Figure 5.

Lung ultrasonography showing multiple B-lines P - Pleura C - Costal shadow

A recent systematic review of accuracy test studies of lung US for the diagnosis of PE in patients with clinical suspicion of PE has demonstrated a sensitivity of 87.0% and a specificity of 81.8% when this technique was used as a single test.[9] The use of triple point-of-care ultrasonography which includes a combination of echocardiography, compressive leg ultrasonography, and lung ultrasonography has been found to increase the sensitivity and specificity to 90% and 86.2% in diagnosing PE.[10] In our patient, lung ultrasonography demonstrated A profile in most of the lung scans with areas of subpleural consolidation seen in the right lung, which leads to suspicion of PE. We chose to undergo CTPA as it was feasible to do it on emergency basis in our hospital.

Our case report highlights the potential use of point-of-care ultrasonography in making early diagnosis of PE. This not only avoids unnecessary delay in establishing differential diagnosis but also guides the further management course in patients, especially those presenting to emergency department with unstable hemodynamics. Thus, we conclude that POCUS is a highly promising modality for diagnosing occult abnormalities such as PE in the emergency department. Although POCUS has become a common modality these days, its application for diagnosing PE in triage settings has rarely been reported. Therefore, in the presence of limitations to CTPA, POCUS and recently triple POCUS can provide alternate diagnostic strategies for PE.

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Conflicts of interest

There are no conflicts of interest.