## **Core Concept**
Haemodialysis is a procedure used to filter waste products from the blood when the kidneys are no longer able to perform this function. It involves the use of a dialyzer and a dialysate solution to remove toxins. The procedure requires adequate blood flow and vascular access.

## **Why the Correct Answer is Right**
The correct answer, **severe hypotension**, is a condition where haemodialysis may not be advisable or may require careful management. Haemodialysis involves the removal of fluid from the blood, which can further decrease blood pressure in a patient with severe hypotension. This can lead to inadequate blood flow through the dialyzer and potentially worsen the patient's condition.

## **Why Each Wrong Option is Incorrect**
* **Option A: Severe hyperkalemia** - Haemodialysis is actually indicated for severe hyperkalemia as it can rapidly decrease potassium levels in the blood, making this option incorrect as an "except" choice.
* **Option B: Fluid overload** - Haemodialysis is used to remove excess fluid from the body in cases of fluid overload, making this a correct indication rather than an exception.
* **Option D: Uremic pericarditis** - Haemodialysis is often necessary for patients with uremic pericarditis as it helps in removing the toxins that contribute to this condition.

## **Clinical Pearl / High-Yield Fact**
A key clinical consideration for haemodialysis is the patient's vascular access. Common types of vascular access include arteriovenous fistulas, arteriovenous grafts, and central venous catheters. Complications can arise with each type, making proper management and maintenance crucial.

## **Correct Answer: C. severe hypotension**