There are likely to be two reasons. First, they may be hypertensive because the disease that was responsible for their kidney failure was associated with or caused hypertension. This is true for patients with hypertensive nephrosclerosis, and for most patients with glomerulonephritis, diabetic nephropathy and polycystic kidney disease. Second, they may be hypertensive because they are overloaded. A direct relation between volume status and blood pressure is well recognised in dialysis patients. The higher the interdialytic weight gain, the greater the pre-dialysis blood pressure and the greater is the decrease in blood pressure during dialysis.

BP and mortality are inversely related in dialysis patients, which is the opposite that in the general population (Fig. 40.1). The likely explanation is that cardiac disease in haemodialysis patients lowers blood pressure and raises mortality (not that lowering blood pressure in renal patients is harmful).

Expert opinion, which is based on observational data rather than randomised trials, suggests a pre-dialysis SBP 140–160 mmHg and a pre-dialysis DBP between 70 and 90 mmHg. Optimal post dialysis BP is thought to be 135–155 mmHg for systolic and unchanged at 70–90 mmHg for diastolic. Patients with fistulas may be feeling apprehensive about the insertion of their dialysis needles, and if so this could exaggerate the alarm reaction that occurs every time a patient’s blood pressure is taken. For this reason, the first blood pressure reading after a patient has started dialysis, which is usually within 5 min of initiating treatment before any significant fluid has been removed, may give a better indication of pre-dialysis blood pressure.

Normovolaemia. This can usually be achieved by salt restriction, ultrafiltration and by reducing dialysate sodium concentration, provided the patient is willing to play their part by limiting weight gains between dialysis. Reduction of dry weight is worth attempting in a hypertensive dialysis patient even in the absence of clinical signs of volume overload. If successful then this can reduce and sometimes eliminate the need for antihypertensive drugs. For these reasons it is always more logical to re-evaluate dry weight than to start or increase antihypertensive drugs.

“Dry weight” is the term used to indicate a dialysis patient’s optimal body weight. This is the weight at which they are euvolaemic, i.e. neither too wet nor too dry. A common issue for patients on long term RRT is fluid overload or being “wet”, especially if unfortunate enough to be anuric. Bearing in mind that 1 kg of body weight approximates 1 litre of water a patient’s weight can be used to monitor their fluid balance, and in particular their inter-dialytic weight gain (see Q8) (Fig. 40.2).

Practically, by checking their weight pre-dialysis. Clinically, a patient who is over their dry weight will usually have oedema and/or be breathless, though a surprising number of overloaded patients have no symptoms whatsoever. They might well be hypertensive. The most likely reason for being over dry weight in a dialysis dependent patient is failure to adhere to fluid restriction.

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