Brain death due to fat embolism - could moderate hypercapnia and prone position be blamed for the tonsillar herniation?

Femoral Nailing in a Porcine Model Causes Bone Marrow Emboli in the Lungs and Systemic Emboli in the Heart and Brain

Background

Shaft fractures of the femur are commonly treated with intramedullary nailing, which can release bone marrow emboli into the bloodstream. Emboli can travel to the lungs, impairing gas exchange and causing inflammation. Occasionally, emboli traverse from the pulmonary to the systemic circulation, hindering perfusion and resulting in injuries such as heart and brain infarctions, known as fat embolism syndrome. We studied the extent of systemic bone marrow embolization in a pig model.

Methods

Twelve anesthetized pigs underwent bilateral intramedullary nailing of the femur, while 3 animals served as sham controls. Monitoring included transesophageal echocardiography (TEE), pulse oximetry, electrocardiography, arterial blood pressure measurement, and blood gas and troponin-I analysis. After surgery, animals were monitored for 240 minutes before euthanasia. Post mortem, the heart, lungs, and brain were biopsied.

Results

Bone marrow emboli were found in the heart and lungs of all 12 of the pigs that underwent intramedullary nailing and in the brains of 11 of them. No emboli were found in the sham group. The pigs subjected to intramedullary nailing exhibited significant hypoxia (PaO2/FiO2 ratio, 410 mm Hg [95% confidence interval (CI), 310 to 510) compared with the sham group (594 mm Hg [95% CI, 528 to 660]). The nailing group exhibited ST-segment alterations consistent with myocardial ischemia and a significant increase in the troponin-I level compared with the sham group (1,580 ng/L [95% CI, 0 to 3,456] versus 241 ng/L [95% CI, 0 to 625] at the 240-minute time point; p = 0.005). TEE detected emboli in the right ventricular outflow tract, but not systemically, in the nailing group.

Conclusions

Bilateral intramedullary nailing caused bone marrow emboli in the lungs and systemic emboli in the heart and brain in this pig model. The observed clinical manifestations were consistent with coronary and pulmonary emboli. TEE detected pulmonary but not systemic embolization.

Clinical Relevance

Femoral intramedullary nailing in humans is likely to result in embolization as described in our pig model. Focused monitoring is necessary for detection of fat embolism syndrome. Absence of visual emboli in the left ventricle on TEE does not exclude the occurrence of systemic bone marrow emboli.

Strategies for hemodynamic maintenance of potential brain-dead donor: integrative review

OBJECTIVE

To learn about the scientific production on strategies adopted for hemodynamic maintenance of brain-dead patients.

METHODS

Integrative review with articles published between 2007 and 2019, in Scientific Electronic Library Online (SciELO), Latin American and Caribbean Health Sciences Literature (LILACS), PubMed® and ScienceDirect. The descriptors " Hemodinâmica AND Morte Encefálica " and "Hemodynamics AND Brain Death" were used. Exclusion criteria were non-human research and gray literature.

RESULTS

A total of 21 articles were listed. As strategies, the use of drugs - noradrenaline (n=8), vasopressin (n=7), dobutamine (n=6), hydrocortisone (n=4) and methylprednisolone (n=4); invasive (n=10) and noninvasive (n=13) cardiac monitoring; control of ventilatory parameters (n=12); and correction of fluid and electrolyte disturbances (n=17) were highlighted.

CONCLUSION

The main strategies found in this integrative review were regulation of blood pressure and temperature, use of catecholamines and corticosteroids, in addition to the need for an early diagnosis of brain death. However, the lack of clearer protocols on the subject is notorious, making management with the potential donor difficult.

Isolated and early-onset cerebral fat embolism syndrome in a multiply injured patient: a rare case

Background

Fat embolism syndrome (FES) is a rare complication that can occur between 12 and 72 h after the initial insult. Isolated cerebral FES without pulmonary symptoms is rarer. Early fracture fixation might prevent FES. We report a case of multiple-fracture with FES despite definite fixation three hours post-injury.

Case presentation

A 54-year-old man presented with multiple fractures: left femoral shaft (AO B2), left distal radius (AO C3), left comminuted patella, right comminuted 1st metatarsal base and left 2nd-4th metatarsal neck. Because he was stable, we gave him early total care and definite fixation, which required seven hours and yielded no complications. After he recovered from anesthesia, however, his eyes deviated right, his right upper arm was paralyzed, his consciousness level was poor, and his Glasgow Coma Scale score was E3VeM4. Chest X-rays showed clear lung fields, and brain computed tomography showed no intracranial hemorrhage. He did, however, have tachycardia, anemia, and thrombocytopenia. Brain magnetic resonance images showed a hyperintensive starfield pattern on diffuse weighted images, which suggested cerebral FES. After supportive care, his consciousness cleared on postoperative day 17, and he recovered full right upper arm muscle power after four months; however, he had a significant cognitive deficit. One-year post-injury, after regular rehabilitation therapy, he was able to independently perform his activities of daily living but still had a residual mild cognitive deficit.

Conclusion

Early fixation can attenuate but not eliminate the incidence of FES. Early assessment and rehabilitation therapy might be required for patients with cerebral FES and cognitive deficits; however, such deficits are difficult to predict and need long-term follow-ups.

Prone Positioning for Management of Fat Embolism Syndrome in a Patient with Spine Fracture; An Unusual Scenario and Review of Literature

Fat embolism syndrome is a rare but fatal complication seen commonly in patients with polytrauma. Its earliest manifestation is hypoxemia due to deposition of fat globules in pulmonary circulation which can progress to severe acute respiratory distress syndrome, the treatment of which is mainly supportive. We describe the case of a 17-year-old male who was admitted in our intensive care unit (ICU) for severe hypoxemia due to fat embolism. He had burst fracture of 5th lumbar vertebra with canal compromise along with other fractures. Failing conventional ventilation, the patient was placed in prone position taking proper precautions in positioning giving due consideration to his unstable lumbar spine. There was no neurological insult and in the next two days, he was weaned off from the ventilator. Though prone position is relatively contraindicated in patients with unstable spine, we employed early prone positioning taking adequate precautions, the benefit of which we believe outweighed the risk.