A Review of Midodrine for the Treatment of Intradialytic Hypotension

maintenance hemodialysis.It has an incidence rate varying from 10 to 30% [2,5,7-9].Significantly, IDH is associated with increased mortality, decreased quality of life, loss of vascular access and myocardial infarction [1][2][3][4][5]8].Moreover, it can lead to dialysis inadequacy as patients often cut short their time on dialysis due to suffering from symptoms of dizziness, fatigue cramps and blurred vision which can be debilitating [2,4,8].Defining IDH has been proven to be difficult with various agencies reporting different definitions.The general consensus is though, that it is best defined as a systolic blood pressure of <100 mmHg, or a blood pressure drop of more than 20 mmHg with symptoms [4,10].The pathogenesis of dialysis hypotension is complex and poorly understood.Originally autonomic dysfunction secondary to uremia was thought to be responsible.It is now believed that transient intravascular hypovolemia is thought to be the major etiological factor behind IDH.Compensatory physiological mechanisms in response to the induced hypovolemia include alterations in cardiac output by increased heart rate and contractility.Augmentation of cardiac preload by venous capacitance and return, arteriolar venoconstricition and plasma refilling from interstitial fluid and intracellular compartments [11].There have been several therapeutic measures employed to manage the effects of IDH.These measures include withholding antihypertensive therapy on dialysis days, avoiding large meals on dialysis, sodium profiling, alterations in ultrafiltration rates on dialysis and cooling of the dialysate.As described earlier, increasing the duration and frequency of dialysis sessions has also been performed.Evidence supporting these treatments are however, limited as few prospective trials exist [1,5,8].Midodrine, an alpha 1 agonist has long been a therapeutic agent for dialysis hypotension, since it was first discovered to be successful in the treatment of orthostatic hypotension in autonomic neuropathy and other forms of orthostatic hypotension such as spinal cord injury [9].Since 1996, midodrine has been studied to help provide safe and