The Impact of Hemodialysis and Arteriovenous Access Flow on Extracranial Hemodynamic Changes in End-Stage Renal Disease Patients

Randomized trial comparing standard versus thermocontrolled haemodialysis using intradialytic cardiac, brain and renal magnetic resonance imaging

BACKGROUND

Ischaemic end-organ damage during haemodialysis (HD) is a significant problem that may be ameliorated by intradialytic cooling. A randomised trial was performed to compare standard HD (SHD; dialysate temperature 37°C) and programmed cooling of the dialysate [thermocontrolled HD (TCHD)] using multiparametric magnetic resonance imaging (MRI) to assess structural, functional and blood flow changes in the heart, brain and kidneys.

METHODS

Prevalent HD patients were randomly allocated to receive either SHD or TCHD for 2 weeks before undergoing serial MRI at four time points: pre-, during (30 min and 180 min) and post-dialysis. MRI measures include cardiac index, myocardial strain, longitudinal relaxation time (T1), myocardial perfusion, internal carotid and basilar artery flow, grey matter perfusion and total kidney volume. Participants then crossed to the other modality to repeat the study protocol.

RESULTS

Eleven participants completed the study. Separation in blood temperature between TCHD (-0.1 ± 0.3°C) and SHD (+0.3 ± 0.2°C; P = .022) was observed, although there was no difference in tympanic temperature changes between arms. There were significant intradialytic reductions in cardiac index, cardiac contractility (left ventricular strain), left carotid and basilar artery blood flow velocities, total kidney volume, longitudinal relaxation time (T1) of the renal cortex and transverse relaxation rate (T2*) of the renal cortex and medulla, but no differences between arms. Pre-dialysis T1 of the myocardium and left ventricular wall mass index were lower after 2 weeks of TCHD compared with SHD [1266 ms (interquartile range 1250-1291) versus 1311 ± 58 ms, P = .02; 66 ± 22 g/m2 versus 72 ± 23 g/m2, P = .004].

CONCLUSIONS

HD adversely affects cardiac function, reduces carotid and basilar artery blood flow and total kidney volume, but mild dialysate cooling using a biofeedback module did not result in differences in intradialytic MRI measures compared with SHD.

Predictors and Outcomes of Acute Brain Injury in Patients on Venoarterial Extracorporeal Membrane Oxygenation after Cardiopulmonary Resuscitation

Background

Venoarterial (V-A) extracorporeal membrane oxygenation (ECMO) after cardiac arrest often predisposes patients to acute brain injury (ABI), which affects survival and neurological performance. The investigation of the predictors of ABI will be beneficial for further management.

Objectives

To explore the predictors and outcomes of ABI and intracerebral hemorrhage (ICH) in patients experiencing cardiac arrest and cardiopulmonary resuscitation (CPR) with V-A ECMO support.

Methods

We retrospectively analyzed 150 patients who successfully weaned from V-A ECMO support after pre-ECMO CPR at our institution from January 2009 to December 2021. Short-term and long-term outcomes were evaluated. Characteristics before and during ECMO were analyzed for determining the predictors of ABI and ICH.

Results

Of the 150 patients, 66 (44.0%) had ABI. ABI was associated with higher in-hospital mortality (62.1% vs. 21.4%, p < 0.0001) and poorer long-term survival after discharge (p = 0.002). Patients who survived to discharge with ABI had significantly more severe neurological deficits at discharge (84.0% vs. 42.4%, p < 0.0001) and improved little at one year after discharge (33.3% vs. 11.4%, p = 0.027). We found that CPR duration [odds ratio (OR) = 1.04, p = 0.003] was the independent risk factor for ABI, whereas lower platelet counts was the independent risk factor for ICH (OR = 0.96, p = 0.019).

Conclusions

After CPR, development of ABI during V-A ECMO support impacted survival and further neurological outcome. Longer CPR duration before ECMO set up significantly increases the occurrence of ABI. Besides, severe thrombocytopenia during ECMO support increases the possibility of ICH.

Peritoneal dialysis in the setting of acute brain injury: an underappreciated modality

INTRODUCTION

Dialysis is complicated in the setting of acute brain injury (ABI) due to several factors including acute solute shifts, acid base changes, need for anticoagulation, and changes in intracranial pressure. For these reasons, continuous renal replacement therapy (CRRT) is often the chosen modality for renal replacement needs in these patients. Peritoneal dialysis (PD) is less discussed but shares many of the benefits often attributed to CRRT. We describe, from both nephrology and neurosurgical perspectives, a case successfully managed with PD.

CASE

A 25-year-old male with history of end-stage kidney disease (ESKD) secondary to focal segmental glomerulosclerosis on continuous cycling PD for 5 years presented to the hospital with headache and altered mental status. Initial imaging revealed a large intraventricular hemorrhage extending to the fourth ventricle. He underwent an emergent right depressive hemicraniectomy and clot evacuation. Post-operative imaging revealed worsening cerebral edema, intraventricular hemorrhage, and hydrocephalus. The decision was made to continue PD, noting that it retains many of the benefits of CRRT (which it is in fact, a form of) which he tolerated well until the need for a percutaneous gastrostomy tube arose. He was transiently transitioned to hemodialysis but returned to PD once his gastrostomy healed. He continued PD for 1 year without complication and eventually received a kidney transplant.

DISCUSSION

In managing patients with ABI undergoing dialysis, a number of considerations must be undertaken including avoidance of hypotension to maintain cerebral perfusion pressure and minimize ischemia reperfusion injury, avoidance of anticoagulants that can precipitate or worsen bleeding, the potential for cerebral edema due to rapid solute clearance and osmotic dissipation of therapeutic hypernatremia, and the mitigation of intracellular acidosis from bicarbonate delivery. Although underutilized, PD may potentially serve as a viable option for dialysis in the setting of ABI as demonstrated by the case presented.

Cerebral blood flow pulsatility and cerebral artery stiffness acutely decrease during hemodialysis

End-stage kidney disease (ESKD) is associated with increased arterial stiffness and cognitive impairment. Cognitive decline is accelerated in ESKD patients on hemodialysis and may result from repeatedly inappropriate cerebral blood flow (CBF). The aim of this study was to examine the acute effect of hemodialysis on pulsatile components of CBF and their relation to acute changes in arterial stiffness. In eight participants (age: 63 ± 18 years, men: 5), CBF was estimated using middle cerebral artery blood velocity (MCAv) assessed with transcranial Doppler ultrasound before, during, and after a single hemodialysis session. Brachial and central blood pressure, along with estimated aortic stiffness (eAoPWV) were measured using an oscillometric device. Arterial stiffness from heart to MCA was measured as the pulse arrival time (PAT) between electrocardiogram (ECG) and transcranial Doppler ultrasound waveforms (cerebral PAT). During hemodialysis, there was a significant reduction in mean MCAv (-3.2 cm/s, p < 0.001), and systolic MCAv (-13.0 cm/s, p < 0.001). While baseline eAoPWV (9.25 ± 0.80 m/s) did not significantly change during hemodialysis, cerebral PAT increased significantly (+0.027 , p < 0.001) and was associated with reduced pulsatile components of MCAv. This study shows that hemodialysis acutely reduces stiffness of arteries perfusing the brain along with pulsatile components of blood velocity.

Cerebral blood flow regulation in end-stage kidney disease

Patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD) experience an increased risk of cerebrovascular disease and cognitive dysfunction. Hemodialysis (HD), a major modality of renal replacement therapy in ESKD, can cause rapid changes in blood pressure, osmolality, and acid-base balance that collectively present a unique stress to the cerebral vasculature. This review presents an update regarding cerebral blood flow (CBF) regulation in CKD and ESKD and how the maintenance of cerebral oxygenation may be compromised during HD. Patients with ESKD exhibit decreased cerebral oxygen delivery due to anemia, despite cerebral hyperperfusion at rest. Cerebral oxygenation further declines during HD due to reductions in CBF, and this may induce cerebral ischemia or "stunning." Intradialytic reductions in CBF are driven by decreases in cerebral perfusion pressure that may be partially opposed by bicarbonate shifts during dialysis. Intradialytic reductions in CBF have been related to several variables that are routinely measured in clinical practice including ultrafiltration rate and blood pressure. However, the role of compensatory cerebrovascular regulatory mechanisms during HD remains relatively unexplored. In particular, cerebral autoregulation can oppose reductions in CBF driven by reductions in systemic blood pressure, while cerebrovascular reactivity to CO₂ may attenuate intradialytic reductions in CBF through promoting cerebral vasodilation. However, whether these mechanisms are effective in ESKD and during HD remain relatively unexplored. Important areas for future work include investigating potential alterations in cerebrovascular regulation in CKD and ESKD and how key regulatory mechanisms are engaged and integrated during HD to modulate intradialytic declines in CBF.

Cerebro-renal interaction and stroke

Stroke is an event causing a disturbance in cerebral function leading to death and disability worldwide. Both acute kidney injury and chronic kidney disease (CKD) are associated with an increased risk of stroke and cerebrovascular events. The underlying mechanistic approach between impaired renal function and stroke is limitedly explored and has attracted researchers to learn more for developing therapeutic intervention. Common risk factors such as hypertension, hyperphosphatemia, atrial fibrillation, arteriosclerosis, hyperhomocysteinemia, blood-brain barrier disruption, inflammation, etc. are observed in the general population, but are high in renal failure patients. Also, risk factors like bone mineral metabolism, uremic toxins, and anemia, along with the process of dialysis in CKD patients, eventually increases the risk of stroke. Therefore, early detection of risks associated with stroke in CKD is imperative, which may decrease the mortality associated with it. This review highlights mechanisms by which kidney dysfunction can lead to cerebrovascular events and increase the risk of stroke in renal impairment.

Recurrent reversible neurologic deficits during hemodialysis

Acute neurologic complications in patients receiving dialysis may be secondary to either underlying comorbid diseases, or to the dialysis procedure itself. An incident hemodialysis patient suffered recurrent consecutive episodes of transient ischemic attacks (TIA) that occurred only during hemodialysis and resolved upon discontinuation of the procedure. Eventual work-up demonstrated an almost complete occlusion of left internal carotid artery. It is likely that the decrease in cerebral blood flow that occurs during hemodialysis, in conjunction with the severely stenotic internal carotid artery, explained the patient's symptoms. The stenotic lesion was deemed inoperable. The patient was transferred to peritoneal dialysis and had no further TIA events.