CRUSH INJURIES – Pathophysiology, Symptoms, Management and Treatment
CRUSH INJURIES – Pathophysiology, Symptoms, Management and Treatment
A crush injury occurs when a body part is subjected to a high degree of force or pressure, usually after being squeezed between two heavy objects. Most often accidental, crush injuries are responsible for broken bones, severe bruising, bleeding, lacerations, and compartment syndrome. Crush injuries are common in car accidents, falls and in any situation that can lead to a structure collapsing. But there are also varying degrees of crush injuries, from slamming a finger in a door to limbs being trapped and crushed for an extended period of time.
Damage related to crush injuries includes: Bleeding, bruising, compartment syndrome, fracture, laceration (open wound), nerve injury and secondary infection.
PATHOPHYSIOLOGY
Crush injury can follow prolonged continuous pressure on muscle tissue. Crush injury can lead to crush syndrome. Ischemia reperfusion (when the pressure is released from the crushed limb) is the main mechanism of muscle injury in crush syndrome. There are traumatic rhabdomyolysis. Muscle injury causes large quantities of potassium, phosphate, myoglobin, creatine kinase and urate to leak into the circulation. Myoglobin levels in the plasma are normally very low. If a significant amount of skeletal muscle is damged (>100g), excess myoglobin is filtered by the kidneys and can cause renal tubular obstruction and renal damage; the excess myoglobin is nephrotoxic. Intravascular volume depletion and renal hypoperfusion, combined with myoglobinuria, result in renal dysfunction.
Crush syndrome is characterized by:
Hypovolaemic shock (due to sequestration of water in the injured muscle cells)
Hyperkalemia (release of cellular potassium by the injured muscle cells)
SYMPTOMS
Depending on the severity of the crush injury, the symptoms will differ. For a minor injury (i.e. a finger in a door or dropping something on a toe) there can be bruising, lacerations and moderate pain. However, the recovery time is significantly shorter than a major crush injury, as is the degree of the symptoms.
In the case of a major crush injury, there is often serious damage below the skin, including tissues, organs, muscles and bones. A crush injury will often cut off the flow of blood in the damaged appendage, leading to serious muscle and tissue damage, as well as numbness and possible paralysis. There is also a much greater chance for infection in the damaged tissues and muscles. The force of the impact can also cause serious damage to the skin, in some cases completely removing layers and leaving the wound exposed to infection and deformity. Infection can lead to amputation in extreme cases. Nausea, vomiting, confusion and agitation may occur as consequences of disturbed body chemistry; urea, creatinine, uric acid, potassium, phosphate, and creatine kinase are elevated.
In many cases of crush injuries, compartment syndrome will take place. When the muscles and tissues are deprived of blood for too long after a crush injury accident occurs, there is a strong chance that the nerves will become severely damaged and the victim will experience muscle death. While most common in crush injuries to the legs, compartment syndrome can occur in any part of the body that is crushed and trapped between two objects for too long. When compartment syndrome is settling in, the first sign is extreme pain, followed by the tingling sensation of “pins and needles” that a limb experiences when it is “asleep” and then eventually paralysis of the limb. Once the paralysis has set in, the pulse will be nonexistent in the affected limb. A visual sign of compartment syndrome is swollen skin with a shiny appearance.
INITIAL MANAGEMENT
- The patient must be assessed in keeping with the usual criteria for assessing a severely injured person
- Assessment of ‘airway, breathing and circulation’ should be carried out
- Attention should be given to life-threatening injuries
- Venous access should be obtained as early as possible, ideally before the trapped limb is freed and decompressed.
- In the adult, a saline infusion of 1,500 ml/hour should be initiated during extrication. Early, vigorous hydration (10 litres/day) helps preserve renal function
- Because of the very high risk of acute kidney injury, a catheter should be inserted at an early stage and urine output monitored.
- Because of the need to maintain fluid balance, a central venous line is usually required.
TREATMENT
In the case of minor crush injuries, medical attention shouldn’t be necessary. Simply clean the wound with fresh water, especially if bleeding is present, to avoid infection. Apply ice to the point of injury and keep it compressed to alleviate pain. Should there be considerable swelling and limited or no mobility in the affected extremity, medical attention may be necessary in order to obtain an X – ray and determine if there is a break. Fractures are often a cause of compartment syndrome.
If the wound is considerably greater with moderate to heavy bleeding, immediate medical attention is required, and a tetanus shot will be necessary, as well as other antibiotics. In serious crush injuries, in which compartment syndrome has already set in or is inevitable, immediate surgery (most likely a fasciotomy) will be required to eliminate the pressure on the muscles and nerves. If the injury is not treated immediately and compartment syndrome exists for considerable time, then amputation may be required. Many cases of serious crush injury will require multiple surgeries to complete nerve and tendon repairs.