A 65-year-old woman with no history of pulmonary or cardiovascular issues presents to the emergency department with nausea, fatigue, and fullness and pain of the abdomen. The nurse knows the assessment tests that will be ordered first will include:

Choice A reason:
Vitamin K (phytonadione) is the antidote for warfarin overdose. It works by promoting the synthesis of clotting factors that are inhibited by warfarin, thereby reversing the anticoagulant effects. In cases of excessive warfarin intake, administering vitamin K helps restore normal clotting function.

Choice B reason:
Protamine sulfate is the antidote for heparin overdose, not warfarin. It works by neutralizing the anticoagulant effects of heparin, but it has no effect on warfarin-induced anticoagulation. Therefore, it is not appropriate for this situation.

Choice C reason:
A PTT lab test measures the effectiveness of the intrinsic pathway of coagulation and is primarily used to monitor heparin therapy. It is not relevant for managing warfarin overdose, as warfarin affects the extrinsic pathway, which is measured by the PT/INR test.

Choice D reason:
While an INR lab test is essential for monitoring the therapeutic levels of warfarin, the immediate need in this situation is to reverse the effects of the overdose. Administering vitamin K is the necessary intervention to counteract the excessive anticoagulation caused by warfarin.

Choice A reason:
While decreased cerebral blood flow can contribute to various neurological conditions, it is not the primary cause of hepatic encephalopathy. Hepatic encephalopathy is primarily associated with liver dysfunction rather than cerebrovascular issues. Thus, this choice is incorrect.
Choice B reason:
Impaired ammonia metabolism is the primary cause of hepatic encephalopathy. When the liver is unable to adequately convert ammonia to urea due to chronic liver disease, ammonia accumulates in the bloodstream. This leads to toxic effects on the brain, resulting in the symptoms of hepatic encephalopathy. Therefore, this choice accurately reflects the underlying pathophysiology of the condition.
Choice C reason:
Hyperbilirubinemia and jaundice are common in liver disease but are not the primary causes of hepatic encephalopathy. These conditions result from impaired bilirubin metabolism and do not directly lead to the neurological manifestations seen in hepatic encephalopathy. Therefore, this choice is incorrect.
Choice D reason:
Fluid and electrolyte imbalances can occur with chronic liver disease but are not the primary cause of hepatic encephalopathy. While they may exacerbate the condition, the main issue is the accumulation of ammonia due to impaired liver function. Hence, this choice is incorrect.