Which of the following statement(s) is/are true concerning the consequences of vascular injuries?

a. Outcome is time-dependent

b. Further injury can take place after restoration of blood flow

c. Acute acidosis, hyperkalemia and myoglobin-induced renal failure can be consequences of severe extremity ischemia

d. Ischemia to peripheral nerves and muscles can be tolerated to up to four hours without permanent injury

Local consequences of vascular injuries are generally related to acute arterial occlusion from thrombosis after injury. The results of ischemia distal to the injury sites may lead to limb or organ loss. The degree of tissue loss is related to the adequacy of collateral flow, the sensitivity of distal tissue to ischemia, and the delay involved in repairing the injury and restoring blood flow. With regard to these latter issues, the variability is great. The brain is more sensitive to ischemia because of high basal energy requirements in the absence of glycogen stores. Brain ischemia for longer than 4 minutes results in irreversible injury. The nerves and muscles are much more resilient, tolerating periods of ischemia up to 4 hours without permanent injury. An important principle of vascular repairs, however, is that the outcome is timedependent, necessitating an aggressive approach and a high priority.

The mechanism of injury from acute arterial ischemia includes both the initial anoxic phase when blood flow is ceased and reperfusion phase after restoration of blood flow. Termed the reperfusion injury, this phase includes the production of toxic metabolites and an inflammatory response which causes significant endothelial damage. The events associated with restoration of arterial blood flow after complete ischemia extend the magnitude and severity of the original insult in skeletal muscle and peripheral nerves. If the severity of ischemia is significant enough to cause skeletal muscle necrosis, rhabdomyalysis with the release of potassium and myoglobin into the systemic circulation follows. Acute acidosis, hyperkalemia, and myoglobin-induced renal failure can occur.