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Diagnosis Deconstructed: Navigating the Occult

Morchi, Ravi MD

doi: 10.1097/01.EEM.0000453164.24287.5a
Diagnosis Deconstructed

Dr. Morchiis the director of the Medical Screening Examination program at Harbor UCLA Medical Center and an assistant professor of emergency medicine at UCLA's David Geffen School of Medicine. Read his past columns athttp://bit.ly/MorchiCollection.

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A young man falls from his motor bike onto his left leg. He is awake, alert, and has normal cardiopulmonary function without cervical spine pain. Practitioners note a 6 cm laceration of skin overlying his calcaneus. He has normal Achilles tendon function.

The area is cleansed, irrigated, and repaired while in the prone position. Hours after the procedure, the patient is turned supine and feels lightheaded and faint. Blood pressure reads 73/33 mm Hg, and heart rate is 40 bpm. Let us consider blood before we fall back on a vagal event as his diagnosis.

Is this hemorrhage? No external signs of bleeding and no mention of blood loss at the field. Internally, both thoracic cavities are clear to auscultation with equal chest rise and no pain. No indication of a hemothorax. Abdominal exam is soft, and an ultrasound shows normal IVC parameters and no free fluid. Neither of the patients' thighs are enlarged, and he has no extensive ecchymosis to signify loss of blood into soft tissues.

Retroperitoneum and true pelvis. The two cavities are confluent behind the retroperitoneal curtain as it reflects inferiorly and anteriorly to become the roof of the pelvis. I relate the retroperitoneum to backstage and the pelvis to the orchestra below stage. Blood in the retroperitoneum can trigger a vagal response. It is categorized in zones.

Zone 1 is a hematoma overlying the aorta and IVC. It is concerning for an injury to a major vascular structure or to the celiac or SMA take-offs. It often requires operative exploration.

Zone 2 is a lateral hematoma around either kidney, possibly emanating from renal vasculature. Selective exploration may be undertaken in penetrating trauma or if the abdomen is open for another reason and the hematoma is expanding intra-operatively.

Zone 3 hematomas are inferior to the iliac crest, along the iliacus muscle or pelvic rim. They may arise from tributaries of external or internal iliac vessels, or more often from multiply fractured, unstable pelvic bone injuries. Blood in the true pelvis or zone 3 can be managed conservatively with orthopedic stabilization, interventional radiologic embolization of culprit vessels, or extraperitoneal packing with or without ligation of the internal iliac arteries for patients with hemodynamic instability. Invisible retroperitoneal and true pelvis hemorrhage should be on the minds of clinicians facing unexplained hypotension in a trauma patient.

A low mechanism event in this particular case without evidence of pelvic bone fracture or complaints of abdominal or back pain would make EPs end investigation short of a CT. Ultimately, major hemorrhage of any sort and at any site will be less likely with normal IVC parameters during an episode of hypotension.

Is there another source for occult blood loss? The main consideration would be in unconscious patients with facial trauma resulting in fractured maxillae and pterygoid plates. Lacerated maxillary arteries can pump blood into the posterior nasopharynx of a head-injured victim who, status post-intubation, continues to have blood flow back into his esophagus. He will demonstrate hypotension in the setting of continued blood replacement and have negative CT scans of the chest, abdomen, and pelvis. The diagnosis will need to come from the OG tube or the EP who performed intubation. Eventually, melena may pour out of his rectum. A combination of posterior packing, endoscopy, and angioembolization are considerations for therapy.

The patient is allowed to rest before having ambulation tested. He again becomes bradycardic and diaphoretic. Despite attempts to discharge him, he feels faint and has to be brought back to the bedside. Bradycardia and peripheral vasodilation from a second vagal episode?

Serial hemoglobin measurements showed a drop from 14 to 11.6 after hours of saline administration. Large amounts of hemorrhage producing hypotension should materialize as bigger drops over this prolonged time period. His blood pressure and heart rate in the supine position normalize again.

Radiographs of the lower leg reveal gas in the proximal calf, well above the laceration. Simple tracking of environmental air? Only if this was a puncture wound or impalement, in which case the wound is much deeper than its length leads us to believe. A rapidly advancing necrotizing soft tissue infection? Rare cases have been described evolving over hours.

Simple irrigation in the ED will not adequately cleanse the full length of injurywhen impalement devitalizes a long length of tissue deep within a limb. Many patients require operative exploration with assessment of soft tissue viability, possible debridement, and washout. They require the same thing in cases of necrotizing infections. Sometimes, an amputation.

His limb is re-examined, and a surgical consult is called. His leg is noted to have edema around the medial aspect of the knee, blotchy ischemic change over the anterior lower leg, and edema and tenderness of the proximal calf. Compartments are soft. All of this transpires hours after the injury and far superior to the break in skin over the calcaneus.

A CT scan reveals heterogeneous fascial thickening as high up as the proximal thigh, a moderate-sized fluid collection extending above and below the medial side of his knee, and subcutaneous stranding and fascial thickening of the deep and superficial posterior compartments of his lower leg. These findings are accompanied by air sprinkled around but not within muscle groups.

He is taken to the OR, where the original laceration is opened and an incision is extended for adequate distal limb exploration. Fascia of his posterior compartment is incised, and the muscle appears viable. No fasciitis and no myositis. A second incision is made medial to the knee and a moderate hematoma is evacuated. Again, fascia and muscle appear viable.

Diagnosis? A shearing injury that tears off the subcutaneous layer of the fascia below. It commonly occurs near bony prominences like the greater trochanter, knee, lumbar spine, or iliac crests. Shearing disrupts perforating vessels attempting to ascend from fascia into the subcutaneous layer above. Disconnected and devascularized subcutaneous means necrosis of fat and sometimes dermis. The potential space created below can be occupied by serous fluid, blood, or necrotic fat debris. Initial events are solely traumatic, and there need not be an associated infection. Findings can evolve over hours. Depending on the patient's condition, management ranges from simple aspiration of the fluid collection with compression bandages to formal operative exploration.

Occult, internal degloving injuries can be difficult to diagnose because no break in dermis was seen at the point of subcutaneous shearing. Increased vagal tone can accompany this and other soft tissue injuries. If missed, the macerated tissue and potential space created can lead to local or systemic inflammatory complications and even inoculation of underlying bone.

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