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The following categories for stratifying levels of severity of acute limb ischemia are recommended (see below). They have been adopted from the original SVS/ISCVS reporting standards,1 which have undergone recent modifications, including the classification of acute limb ischemia.2 Although this approach attempts to stratify limbs into defined groups for decision-making purposes, it should be recognized that it is not yet possible to achieve this with absolute certainty, and qualifying remarks throughout the text must be heeded. Although the original classification has been widely used in clinical trials and has been shown to correlate with outcome, this newer modification has not been prospectively tested and evaluated.3 A very similar classification to that one proposed above has been independently developed and proposed by a Working Party on Thrombolysis in the Management of Limb Ischemia, also without prospective testing.4 In the absence of much-needed markers of ischemia, this approach, based on clinical observation and logic, has prevailed, but clearly prospective testing is needed, as are ischemic markers. Some markers, such as creatinine phosphokinase, have been tested for extremity as well as mesenteric ischemia, but the need for a rapid test with good clinical correlation has not yet been met.5 6
Levels of Severity
I. Viable
Not immediately threatened; no continuing ischemic pain; no neurological deficit; skin capillary circulation adequate; clearly audible Doppler arterial flow signals in a pedal artery.
II. Threatened viability
Implies reversible ischemia in a limb that is salvageable, avoiding major amputation, if arterial obstruction is relieved quickly. Two levels within this category are recognized for therapeutic purposes, and their differences are tabulated in Table XXXIII: Ila, marginally threatened, and Ilb, immediately threatened. Neither category has clearly audible Doppler signals in pedal arteries. Patients with marginally threatened extremities (Ila) may experience numbness and have transient or minimal sensory loss, limited to the toes. Continuous pain is absent. In contrast, immediately threatened (IIb) limbs have persistent ischemic rest pain, or detectable loss of sensation above the toes or a continuing lack of all sensation in the toes, or any motor loss (paresis or paralysis).
III. Major, irreversible ischemic change
This level usually requires major amputation or results in significant, permanent neuromuscular damage, regardless of therapy. Profound sensory loss and muscle paralysis extending above the foot, absent...