Overview
Definition:
Aortic cross-clamping in trauma refers to the temporary occlusion of the aorta, typically the descending thoracic aorta, proximal to the site of injury or during critical operative maneuvers to control hemorrhage or facilitate distal surgical access in the context of severe thoracic trauma.
Epidemiology:
Injuries to the aorta are rare but have a high mortality rate, often associated with high-energy blunt or penetrating trauma
Aortic transection or rupture has a mortality of up to 80%, with many succumbing pre-hospital
Emergency aortic cross-clamping is a life-saving but high-risk intervention reserved for hemodynamically unstable patients with massive hemorrhage.
Clinical Significance:
Effective management of catastrophic hemorrhage from aortic injuries is paramount to patient survival
Aortic cross-clamping, when indicated, can dramatically reduce blood loss and stabilize the patient, providing a window for definitive repair
However, it is associated with significant physiological derangements and complications, requiring careful patient selection and execution.
Indications
Indications:
Emergency aortic cross-clamping is indicated in trauma patients presenting with: Massive, uncontrolled hemorrhage from the thoracic aorta or its branches, leading to profound hemodynamic instability (e.g., shock, pulselessness) despite resuscitation efforts
Rupture or transection of the aorta with active bleeding
Extracranial hemorrhage unresponsive to other measures
During emergent median sternotomy for severe mediastinal hematoma or suspected aortic arch injury with uncontrolled bleeding.
Contraindications:
Absolute contraindications are few in extremis, but relative contraindications include severe pre-existing comorbidities that preclude survival even with aortic control (e.g., catastrophic brain injury)
Known unreconstructible aortic injury
Prolonged ischemia time likely to result in irreversible organ damage
Inability to achieve adequate proximal control of the aorta.
Patient Selection:
Careful patient selection is critical
Patients must be hemodynamically unstable with evidence of ongoing catastrophic bleeding directly attributable to the aorta or major branches
A rapid assessment of injury pattern, associated injuries, and potential for survival with intervention is essential.
Preoperative Preparation
Resuscitation:
Aggressive fluid resuscitation with blood products (packed red blood cells, fresh frozen plasma, platelets) is crucial
Maintain permissive hypotension if penetrating trauma patient with active bleeding
Early institution of massive transfusion protocol.
Anesthesia Considerations:
General anesthesia with rapid sequence induction
Careful anesthetic management to avoid further hemodynamic compromise
Invasive monitoring including arterial line, central venous catheter, and possibly pulmonary artery catheter
Titrated vasopressors and inotropes readily available.
Surgical Planning:
Rapid assessment of imaging (FAST exam, CT angiography if available and stable enough) to delineate injury location and extent
Preoperative planning should include anticipated surgical approach (e.g., median sternotomy, thoracotomy) and available vascular grafts or repair materials.
Procedure Steps
Surgical Approach:
The typical surgical approach for descending thoracic aortic cross-clamping in trauma is a left posterolateral thoracotomy at the level of the aortic injury
A median sternotomy may be necessary for arch injuries or if associated cardiac or mediastinal injuries are present.
Aortic Dissection And Mobilization:
The aorta is meticulously dissected from surrounding tissues, taking care to avoid injury to adjacent structures like the vagus nerve, esophagus, and sympathetic chain
Adequate mobilization is required for safe placement of the aortic clamp.
Cross Clamping Technique:
A vascular clamp (e.g., Satinsky clamp, Cooley clamp, or bulldog clamp) is applied across the aorta proximal to the injury
The duration of clamping should be as short as possible, typically aiming for less than 20-30 minutes, due to the risk of ischemic injury distal to the clamp
In cases of extensive injury or complex repair, partial clamping or shunting techniques may be considered.
Hemostasis And Repair:
Once the aorta is cross-clamped, hemorrhage is controlled
Definitive repair of the aortic injury is then performed, which may involve direct suture repair, patch angioplasty, or interposition of a prosthetic graft
After repair, the clamp is gradually released, carefully monitoring for leaks and ensuring distal perfusion.
Complications
Ischemic Complications:
Spinal cord ischemia leading to paraplegia is a major concern, particularly with prolonged clamping or clamping of the descending aorta proximal to the origin of the left subclavian artery
Visceral ischemia (kidneys, intestines) and lower extremity ischemia can also occur.
Reperfusion Injury:
Release of the aortic clamp can lead to a sudden drop in blood pressure due to the release of acidic metabolites and inflammatory mediators from the ischemic tissues
This can precipitate or exacerbate organ dysfunction.
Hemodynamic Instability:
Sudden increase in afterload due to aortic occlusion can lead to hypertension and myocardial strain
Conversely, after clamp release, rapid fluid shifts and vasodilation can cause hypotension
Arrhythmias are also common.
Bleeding And Thrombosis:
Bleeding at the repair site or from mobilization of adhesions is a risk
Thrombosis of the repaired vessel or graft can occur, leading to limb ischemia or organ infarction.
Postoperative Care
Monitoring:
Close monitoring of vital signs, urine output, and neurological status is essential
Continuous ECG monitoring for arrhythmias
Frequent laboratory assessments including CBC, electrolytes, renal function, and coagulation profile.
Hemodynamic Management:
Maintain adequate blood pressure and perfusion pressure to vital organs
Titrate vasopressors and inotropes as needed
Aggressive fluid management to ensure adequate intravascular volume.
Pain Control:
Effective pain management is crucial, often requiring patient-controlled analgesia (PCA) or epidural anesthesia
Adequate pain relief can improve respiratory function and reduce the risk of complications.
Mechanical Ventilation:
Patients often require mechanical ventilation postoperatively due to significant thoracic trauma and prolonged surgical intervention
Weaning from the ventilator should be gradual and carefully monitored.
Key Points
Exam Focus:
Indications for emergency aortic cross-clamping in trauma are limited to uncontrolled hemorrhage and hemodynamic instability
Know the typical approach (left thoracotomy for descending aorta) and clamp types
Spinal cord ischemia is the most feared complication.
Clinical Pearls:
Permissive hypotension in trauma patients with hemorrhage can be beneficial
Use the shortest possible clamping time and consider intercostal artery ligation management to minimize ischemic burden
Always have a vascular graft readily available.
Common Mistakes:
Delaying aortic cross-clamping in a dying patient due to hesitation
Inadequate mobilization of the aorta, leading to injury
Prolonged clamping time leading to irreversible ischemic damage
Failure to adequately monitor and manage post-clamping hemodynamic instability.