Clinical Signs and Symptoms

The symptoms and signs of acute ischemia are often summarized as the “five Ps”: pain, pallor, pulselessness, paresthesia, and paralysis. Besides being helpful for establishing diagnosis, careful evaluation of the five Ps is useful for assessing the severity of ischemia. Sometimes a sixth P’s is used – poikolothermia, meaning a low skin temperature that does not vary with the environment.

Pain: For the typical patient, as the one described above, the pain is severe, continuous, and localized in the foot and toes. Its intensity is unrelated to the severity of ischemia. For instance, it is less pronounced when the ischemia is so severe that the nerve fibers transmitting the sensation of pain are damaged. Patients with diabetes often have neuropathy and a decreased sensation of pain.

Pallor: The ischemic leg is pale or white initially, but when ischemia aggravates the color turns to cyanotic blue. This cyanosis is caused by vessel dilatation and desaturation of hemoglobin in the skin and is induced by acidic metabolites in combination with stagnant blood flow. Consequently, cyanosis is a graver sign of ischemia than pallor.

Pulselessness: A palpable pulse in a peripheral artery means that the flow in the vessel is sufficient to give a pulse that is synchronous with vessel dilatation, which can be palpated with the fingers. In general, palpable pulses in the foot therefore exclude severe leg ischemia. When there is a fresh thrombus, pulses can be felt in spite of an occlusion, so this general principle must be applied with caution. Palpation of pulses can be used to identify the level of obstruction and is facilitated by comparing the presence of pulses at the same level in the contralateral leg.

When the examiner is not convinced that palpable pulses are present, distal blood pressuresmust be measured. It is prudent to always measure the ankle blood pressure. This is a simple way to verify ischemia and the measurement can be used to grade the severity and serve as a baseline for comparison with repeated examinations during the course of treatment. (This will be discussed further later.) The continuous-wave (CW) Doppler instrument does not give information about the magnitude of flow because it registers only flow velocities in the vessel. Therefore, an audible signal with a CW Doppler is not equivalent to a palpable pulse, and a severely ischemic leg can have audible Doppler signals.

Paresthesia: The thin nerve fibers conducting impulses from light touch are very sensitive to ischemia and are damaged soon after perfusion is interrupted. Pain fibers are less ischemia-sensitive. Accordingly, the most precise test of sensibility is to lightly touch the skin with the fingertips, alternating between the affected and the healthy leg. It is a common mistake to believe that the skin has been touched too gently when the patient actually has impaired sensitivity. The examiner then may proceed to pinching and poking the skin with a needle. Such tests of pain fibers evaluate a much later stage of ischemic damage. The anatomiclocalization of impaired sensation is sometimes related to which nerves are involved. Frequently, however, it does not follow nerve distribution areas and is circumferential and most severe distally. Numbness and tingling are other symptoms of ischemic disturbance of nerve function.

Paralysis: Loss of motor function in the leg is initially caused by ischemic destruction of motor nerve fibers and at later stages the ischemia directly affects muscle tissue. When palpated, ischemic muscles are tender and have a spongy feeling. Accordingly, the entire leg can become paretic after proximal severe ischemia and misinterpreted as a consequence of stroke. Usually paralysis is more obscure, however, presenting as a decreased strength and mobility in the most distal parts of the leg where the ischemia is most severe. The most sensitive test of motor function is to ask the patient to try to move and spread the toes. This gives information about muscular function in the foot and calf. Bending the knee joint or lifting the whole leg is accomplished by large muscle groups in the thigh that remain intact for a long time after ischemic damage in the calf muscle and foot has become irreversible.

Date: 2014-12-29; view: 951