Which antidote should be readily available for a client receiving heparin?

The antidote that should be readily available for a client receiving heparin is protamine sulfate. Heparin is an anticoagulant that works by inhibiting clotting factors in the blood, and in the event of an overdose or excessive anticoagulation, it may lead to increased risk of bleeding. Protamine sulfate acts directly to neutralize the effects of heparin, effectively reversing its anticoagulant properties.

When administered, protamine sulfate binds to heparin to form a stable complex that has no anticoagulant activity. This makes it crucial in emergency situations where rapid reversal of heparin's effects is necessary, such as before surgical procedures or in cases of significant bleeding. The other options, while important in their own contexts, do not effectively reverse the effects of heparin. For instance, vitamin K is primarily used for warfarin overdose, fresh frozen plasma contains clotting factors but is not a direct antidote to heparin, and calcium gluconate is used to manage calcium levels but does not address the anticoagulant effects of heparin. Thus, protamine sulfate is the specific and appropriate antidote for heparin-induced anticoagulation.