Recent Advances in the Prevention and Management of Intradialytic Hypotension

Abstract

A symptomatic reduction in BP during or immediately after dialysis occurs in approximately 20 to 30% of dialysis sessions. The treatment includes stopping or slowing the rate of ultrafiltration, placing the patient in the Trendelenburg position, decreasing the blood flow rate, and restoring intravascular volume. Such episodes predispose the patient to leave the dialysis unit volume overloaded and if repetitive can lead to inadequate clearance. Intradialytic hypotension and orthostatic hypotension after the procedure are significant and independent risk factors affecting mortality in dialysis patients. 1 This clinical commentary focuses on recent advances in the prevention and management of intradialytic hypotension.Dialysis hypotension is the result of an inadequate cardiovascular response to the reduction in blood volume that occurs when a large volume of water is removed during a short period of time. In a typical dialysis procedure, an ultrafiltrate volume that is equal to or greater that the entire plasma volume is often removed.Despite the large ultrafiltrate volume, plasma volume typically decreases by only approximately 10 to 20%. This ability to maintain plasma volume during ultrafiltration requires mobilization of fluid from the interstitial into the intravascular space. Vascular refilling is influenced by both patient-specific and treatment-related factors that dictate the distribution of water between the body fluid compartments.The amount of interstitial fluid available for vascular refilling is influenced by the dry weight set for the patient. When the volume of interstitial fluid is small, any ultrafiltrate volume will more likely be associated with hemodynamic instability. This explains the development of hypotension when patients undergo dialysis below their true dry weight. By contrast, increased amounts of interstitial fluid will expand the volume of fluid accessible for refilling of the intravascular space and, therefore, decrease the likelihood of hypotension. In most patients, a dry weight that minimizes the amount of interstitial fluid present is selected because chronic volume overload has long-term deleterious effects on the cardiovascular system.The determination of dry weight is largely assessed empirically by trial and error. The dry weight is set at the weight below which unacceptable symptoms, such as cramping, nausea, and vomiting, or hypotension occur. The dry weight is highly variable in many patients and can fluctuate with intercurrent illnesses (e.g., diarrhea, infection) and with changes in hematocrit (as with erythropoietin). A number of methods have been proposed to define more objectively the dry weight of the patient (Table 1). Comparative studies have generally favored methods based on bioimpedance measurements, which provide an assessment of extracellular and intracellular volume and total body water. 2-4 A variant of this technique in which continuous intradialytic measurements are confined to the calf shows particular promise because the relative volume of excess extrac...

The effect of hemodialysis on intraocular pressure

“…18 This biofeedback system prevents hypotension via the regulation of the ultrafiltration rate and facilitates the protection of the optic nerve from the hazardous effects of hypotension, which can offer protection against ischemia and reperfusion damage in glaucoma patients and individuals prone to glaucoma. 19 Aqueous humor dynamics in a glaucomatous eye differs from the normal eye.…”

Intradialytic Hypotension and Risk of Cardiovascular Disease

“…These findings could have widespread implications in the treatment of patients with ESRD undergoing HD, considering that IDH is estimated to occur in 20%-30% of all dialysis treatments (depending on the definition used for IDH) (4), and that IDWG has been shown to increase the risk of CV events and mortality (10,11).…”

“…The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) defines IDH as "a decrease in systolic BP by $ 20 mmHg or a decrease in mean arterial pressure by 10 mmHg associated with symptoms that include abdominal discomfort; yawning; sighing; nausea; vomiting; muscle cramps; restlessness; dizziness or fainting; and anxiety" (3). On the basis of the KDOQI definition, IDH occurs in approximately 20%-30% of all HD sessions (4). IDH mainly occurs during dialysis when plasma fluid removal through ultrafiltration outpaces the rate of refilling (5).…”

Cooling dialysate during in-center hemodialysis: Beneficial and deleterious effects

“…It occurs in approximately 20%-30% of dialysis sessions [2] and is the most frequent complication of renal replacement therapy [3] . IDH is multifactorial in etiology but is largely attributed to the rapid reduction of blood volume that occurs with ultrafiltration and the inadequate cardiovascular response to the reduction in blood volume [2,4] . Populations predisposed to IDH include the elderly and those with diabetes and cardiovascular diseases [3] .…”