Perfusion

Perfusion items almost always come as a neurovascular check after a cast, fracture, or arterial procedure, with the “tell” being a sudden change on the affected side. Act on the earliest finding: pain out of proportion, worsened by passive stretch and unrelieved by opioids, plus paresthesia signals compartment syndrome — escalate and keep the limb at heart level (never elevate above the heart or ice it, which further drops arterial flow). Don’t wait for pulselessness, pallor, or paralysis; those are late. For a tight cast the correct first action is to notify the provider to bivalve/loosen it, not to medicate.

Distinguish perfusion (a whole-tissue delivery problem) from its relatives: ischemia is reduced flow in a localized bed, typically a single narrowed artery; shock is systemic perfusion failure; and hypoxia can occur with normal perfusion (a lung-oxygenation problem). The classic trap is treating a cool, pulseless, mottled limb as “poor circulation” rather than a limb-threatening emergency. Memory hook: the limb-ischemia 6 P’s — Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia — with pain and paresthesia first.