Categorization of the hemodynamic response to hemodialysis: the importance of baroreflex sensitivity

Visual three-dimensional representation of beat-to-beat electrocardiogram traces during hemodiafiltration

This study evaluated the usefulness of the three-dimensional representation of electrocardiogram traces (3DECG) to reveal acute and gradual changes during a full session of hemodiafiltration (HDF) in end-stage renal disease (ESRD) patients. Fifteen ESRD patients were included (six men, nine women, age 46 ± 19 years old). Serum electrolytes, blood pressure, heart rate, and blood urea nitrogen (BUN) were measured before and after HDF. Continuous electrocardiograms (ECGs) obtained by Holter monitoring during HDF were used to produce the 3DECG. Several major disturbances were identified by 3DECG images: increase in QRS amplitude (47%), decrease in T-wave amplitude (33%), increase in heart rate (33%), and occurrence of arrhythmia (53%). Different arrhythmia types were often concurrent and included isolated supraventricular premature beats (N = 5), atrial fibrillation or atrial bigeminy (N = 2), and isolated premature ventricular beats (N = 6). Patients with decrease in T-wave amplitude had higher potassium and BUN (both before HDF and total removal) than those without decrease in T-wave amplitude (P < 0.05). Concurrent acute and gradual ECG changes during HDF are identified by the 3DECG, which could be useful as a preventive and prognostic method.

Associations of endothelial dysfunction and arterial stiffness with intradialytic hypotension and hypertension

Intradialytic hypotension and hypertension are both independently associated with mortality among persons with end-stage renal disease on hemodialysis. Endothelial dysfunction and arterial stiffness are two possible mechanisms underlying these phenomena, but their association with hemodynamic instability during dialysis has not been evaluated. Thirty patients were recruited from chronic dialysis units at San Francisco General Hospital and San Francisco Veterans Affairs Medical Center. Endothelial dysfunction was assessed with flow-mediated dilation of the brachial artery after upper arm occlusion. Arterial stiffness was assessed using carotid-femoral pulse wave velocity measured by tonometry. Intradialytic hypotension and hypertension were defined as the average decrease in systolic blood pressure (SBP) over 1 week, as well as the frequency over 1 month of hypotension or hypertension. Every 5% decrease in flow-mediated dilation was associated with a 7.5 mmHg decrease in SBP after adjustment for phosphorus, body mass index, atherosclerosis, and ultrafiltration (P=0.02). Every 5 m/s increase in pulse wave velocity was associated with an 8 mmHg increase in SBP after adjustment for predialysis SBP and ultrafiltration (P=0.03). Over 1 month, every 5% lower flow-mediated dilation was associated with a 10% higher frequency of hypotension (P=0.09), and every 5 m/s increase in pulse wave velocity was associated with an 15% higher frequency of hypertension (P=0.02). In a cross-sectional analysis of 30 dialysis patients, endothelial dysfunction and arterial stiffness were independently associated with intradialytic hypotension and intradialytic hypertension, respectively. Elucidating these potential mechanisms of hemodynamic instability during dialysis may facilitate development of treatment strategies specific to this pathophysiology.

Intradialytic hypotension

Intradialytic hypotension (IDH) is common in children during conventional, 4 hour haemodialysis (HD) sessions. The declining blood pressure (BP) was originally believed to be caused by ultrafiltration (UF) and priming of the HD circuit, however emerging data now supports a multifactorial aetiology. Therefore strategies to improve haemodynamic stability need to be diverse and address specific patient requirements or risks. In the treatment of IDH immediate action is required to stop or reduce the severity of symptoms that may precede or follow. Typically UF is slowed or stopped, a fluid bolus is given and in resistant cases the HD session is prematurely discontinued. Patients complete their treatment under-dialysed and volume expanded. Chronically, repeated episodes of IDH cause devastating, multi-system morbidity with an increased risk of mortality. This had provided the impetus for more haemodynamically friendly dialysis prescriptions that attenuate the risk of IDH. During pediatric HD several preventative strategies have been tested but with variable success. Of these, dialysate sodium profiling, UF guided by relative blood volume (RBV) algorithms, cooling and intradialytic mannitol appear to be the most effective. However in refractory cases one may be left with no option but to switch dialysis modality to haemodiafiltration (HDF) or more frequent or prolonged HD regimens.