Haemodialysis

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A comprehensive topic overview

Introduction

Renal replacement therapy (RRT) refers to life-supporting treatments for severe acute kidney injury (AKI) or end stage
kidney disease.
1
Haemodialysis (HD) is a form of RRT that
administration\:
2
Conventional HD is a type of intermittent RRT that usually involves four hours per session, three times per week
Continuous HD involves
care settings

Indications for RRT

Acute RRT
Important indications can be remembered using the mnemonic AEIOU\:
3,4,5
Acidosis\: severe metabolic acidosis, pH \<7.2
Electrolyte disturbance\: severe, refractory hyperkalaemia, >7.0
Ingested toxins\: BLAST (barbiturates, lithium, alcohol, salicylate, theophylline)
Refractory pulmonary oedema
Uraemia\: manifesting as pericarditis/encephalopathy
Chronic RRT
NICE recommends the initiation of chronic RRT when there is the presence of\:
1
Symptomatic uraemia (pericarditis/encephalopathy)
Biochemical measures (electrolyte or acid-base disturbances that are refractory to medical therapy) or uncontrollable

Asymptomatic with an eGFR of 5-7 ml/min/1.73m
2
Other indications outlined by Kidney Disease Improving Global Outcomes (KDIGO) include\:
5
Anorexia
Reduced energy level
Weight loss with no other potential explanation
Progressive deterioration in nutritional status that is refractory to interventions

Types of dialysis

Dialysis is a form of RRT which replaces the kidney’s role in
remove excess water and uraemic wastes. 6,7It also removes excess acid, regulates electrolyte levels, and eliminate
metabolic waste products.However, dialysis cannot replace the kidney’s ability to produce EPO (erythropoietin) and activate vitamin D via 1 alpha-
hydroxylase.
6,7
Figure 1. Summary of dialysis modalities

Choice of dialysis modalities

All patients who are likely to require RRT should be o
supportive management and controlling symptoms but without RRT).
1,5
NICE does not provide a straightforward recommendation in the initial choice of dialysis modality, apart from
recommending peritoneal dialysis (PD) as the
1
The choice of dialysis modality should re
options are presented and explained to them.

Vascular access in haemodialysis

Access in haemodialysis refers to forming an arti
dialysis machine. The most common options are arteriovenous access and central venous catheter access.
Arteriovenous access
Arteriovenous access is indicated in long-term dialysis, which involves surgical anastomoses between an artery and a
vein. 5,8
It is most commonly formed in the non-dominant arm between the radial artery and the cephalic vein, called a
radio-cephalic 8
Other possibilities include brachio-cephalic
There are two main types of arteriovenous access\:
5,8
Arteriovenous
for HD. An AVF takes at least six to eight weeks to mature, allowing the thickening of the vein’s wall to withstand arterial
pressure. NICE recommends establishing an AV
Arteriovenous graft (AVG)\: a synthetic or biological graft is used to connect an artery to a vein. The most common type
of graft is polytetra
two weeks). However, it is at greater risk of developing thrombosis and infection and has a shorter life than AVF.
Care of a
Dialysis access is extremely precious, and precautions must be taken to preserve and care for the
Precautions during HD include\:
8
Needles should only be inserted by a trained operatorAvoid needling the same site repetitively, as it increases the risk of a false aneurysm (pseudoaneurysm) formation
General precautions include\:\:
8
Do not perform venepuncture from a
Do not perform intravenous cannulation between the elbow and wrist
Do not apply a blood pressure cu
For more information on examining a renal system examination.
Importantly, the absence of thrill on palpation and the absence of bruit on auscultation suggests thrombosis.
Patients should be educated to examine the
radiology (local thrombolysis) or surgery is warranted to salvage the
8
Figure 2. A
haemodialysis
Central venous catheter (CVC) access
Catheters used in HD have two openings, one to draw blood from the veins to the dialysis circuit (red), one to drain dialysed
blood back to the patient (blue).
Two main types of CVCs are used to obtain central venous access in HD\:
8,9
Temporary dialysis catheter\: allows immediate use when emergency dialysis is indicated in AKI. Potential sites for
catheter insertion include the internal jugular, subclavian and femoral veins. Due to the much higher risk of infection, they
should only be left in situ for less than two weeks.
Tunnelled haemodialysis catheter\: a large bore, double-lumen venous catheter is inserted in a central vein and is
‘tunnelled’ subcutaneously helping to reduce the risk of infection. A classic indication for the use of tunnelled catheter is
while waiting for a
Choosing haemodialysis access
KDIGO recommends that the choice of HD access should primarily depend on the likelihood of long-term survival,
de
5
If long-term survival is likely to be more than one year, an AVF is preferred. If creating an AVF is not feasible, a cu
tunnelled haemodialysis catheter should be considered.
If long-term survival is likely to be less than one year, AVG or CVC are more appropriate unless opting for conservative
management without RRT.

Principles of HD

The HD apparatus is made up of the blood circuit and the dialysis solution circuit that is bridged by a dialyser, where
arti
The HD circuit is described below\:
A pump removes blood from the patient to the machine
Blood is anticoagulated with heparin to prevent clotting
Blood is pumped through a dialyser where
Filtered blood is returned to the patient, while used dialysate is discarded
Throughout the circuit, the blood pressure is being monitored. Importantly, a post-pump pressure monitor helps detect
impending clotting within the circuits. A venous air trap and air detector is also present to ensure that no air enters the
individual circulation and causing an air embolism.
8How does the dialyser
In HD, the dialyser
semi-permeable membrane.
The dialysate is a solution of puri
bu
8
In the dialyser, excess water and unwanted solutes passively di
dialysate
dialysate.
Only water and low-molecular-weight solutes can pass through the semi-permeable membrane, so blood cells and other
intravascular proteins are not lost. Blood and dialysate
maximises the concentration gradient and the e
Figure 3. A haemodialysis machineFigure 4. The dialyser
Figure 5. A simpli
Haemodialysis vs haemoHaemodialysis removes solute by di
removing larger molecular weight solutes (>20kDa).
8
Haemo
required. 8
Since large volumes are
large molecules to be removed e
Continuous haemo
critical care setting.
8
Assessing dialysis adequacy in HD
Kt/V is a measurement of urea clearance and is considered the most clinically valid measurement of dialysis adequacy
and dose.
10
The Renal Association clinical practice guideline for haemodialysis recommends\:
10
A minimum of 12 hours of HD per week
Monitoring of dialysis dose on a monthly basis
Target dialysis dose should consistently achieve a minimum Kt/V of 1.2
The above points apply for thrice weekly patients, the conventional HD regimen.

Contraindications

The only absolute contraindications for maintenance HD are\:
5
Absence of possible vascular access
Haemodynamic instability
Some relative contraindications include coagulopathy and needle phobia.
7

Complications

Medical emergencies
Some reactions are considered medical emergencies where prompt recognition and immediate cessation of dialysis is
warranted\:
7,11,12
Dialysis disequilibrium syndrome\: acute cerebral oedema secondary to the rapid shifting of mainly urea from the blood.
To prevent this, consider starting with a shorter
slow down the rate of urea clearance.
Dialyser reactions\: interaction between blood components and the HD machine semi-permeable membrane. It could
either be IgE-mediated (type A), causing an anaphylactic-like presentation, or anaphylactoid/non-IgE-mediated (type B),
causing back and/or chest pain that is usually self-limiting.
Acute intravascular haemolysis\: can be caused by chemical reactions (e.g. contamination of dialysate by chlorine,
copper, zinc, chloramine, formaldehyde etc.) or mechanical forces (e.g. kinking of the lines, overheating of the dialysate

Air embolism
Haemorrhage from vascular access
Intra-dialytic complications
The following are some common complications one may experience during HD\:
7,11,12
Hypotension can occur as blood is being pumped out of the circulation at a rate of 300-500 mL/min and is irrespective
of the cardiac cycle. Risk is increased in patients with high interdialytic weight gains.
Muscle cramps, especially in the lower limbs. The exact pathogenesis is unknown, it is thought to be caused by muscle
hypoperfusion with secondary impaired muscle relaxation.
A range of non-speci
pruritus are common for individuals to experience during HD.
13Long-term complications
Dialysis-related complications
7,11,12
Increased risk of bleeding\: caused by platelet dysfunction due to CKD and/or platelet contact with the dialysis
membrane.
Electrolyte disturbances\: hyperkalaemia is the most common, as well as hyponatraemia, hypocalcaemia, and
hyperphosphataemia. These may give rise to fatal cardiac arrhythmias.
CKD-MBD (chronic kidney disease-mineral bone disorder)
Acquired cystic kidney disease
Dialysis-related amyloidosis
Vascular access-related complications
7,11,12
Loss of access due to thrombosis or central venous stenosis
Catheter-related bacteraemia
Local aneurysm or pseudoaneurysm
Dialysis access-associated steal syndrome\: distal limb ischaemia secondary to the AV access shunting blood away
from the limb
Dialysis vascular access haemorrhage
Cardiovascular disease
The risk of cardiovascular disease is 10 to 20 times higher in patients undergoing dialysis than in normal people; it is the
leading cause of death in these patients\:
6,14-16
In
hypertension and cardiovascular diseases.
An immunological response involving macrophages and granulocytes occurs against the arti
resulting in increased free radical production and oxidative stress.
Interleukin-1 inhibits the peripheral conversion of T4 to T3, where low T3 levels contribute to left ventricular
hypertrophy.
Non-speci
11
Insomnia
Bone and joint pain
Restless leg syndrome
Loss of libido and erectile dysfunction
Dry mouth
Anxiety

Key points

Haemodialysis is a form of renal replacement therapy that arti
The conventional haemodialysis schedule involves a four-hour session three times a week.
The ideal vascular access for haemodialysis is an arteriovenous
being used.
Hemodialysis utilises passive di
Headaches, muscle cramps, and hypotension are common side e
haemodialysis.
Cardiovascular disease is the leading cause of death in patients who are on long-term dialysis.

References

National Institute for Health and Care Excellence (NICE). Renal replacement therapy and conservative management
(Clinical guideline [NG107]). NICE 2018. Published 2018 Oct. Available from\: [LINK]Pauly RP. Survival comparison between intensive hemodialysis and transplantation in the context of the existing literature
surrounding nocturnal and short-daily hemodialysis. N e p h r o l o g y D i a l y s i s T r a n s p l a n t a t i o n 2013 Jan;28(1)\:44-7.
Malhotra A. Acute Kidney Injury (AKI). G e r i a t r i c T r a u m a a n d A c u t e C a r e S u r ge r y 2017 Jul;367-380.
Baker JB, Navarro Y, Sisroe TA, Everett C. Indications for Urgent and Emergent Hemodialysis. A n n a l s o f V a s c u l a r S u r g e r y
2024 Jan;98\:39-40.
Chan CT, e t a l . Dialysis initiation, modality choice, access, and prescription\: conclusions from a Kidney Disease\: Improving
Global Outcomes (KDIGO) Controversies Conference. K i d n e y I n t e r n a t i o n a l 2019 Jul;96(1)\:37-47.
Vadakedath S, Kandi Venkataramana. Dialysis\: A Review of the Mechanisms Underlying Complications in the Management
of Chronic Renal Failure. C u r e u s 2017 Aug;9(8)\:e1603.
Murdeshwar HN, Anjum F. Hemodialysis. T r e a s u r e I s l a n d ( F L ) \: S t a t P e a r l s P u b l i s h i n g 2 0 2 4 J a n [Internet]. Updated\: 2023 Apr.
Available from\: [LINK]
Steddon, S. et al. Chapter 4 Dialysis. Oxford Handbook of Nephrology and Hypertension. Oxford\: Oxford University Press,
2018.
Hemodialysis Catheters\: How to Keep Yours Working Well. National Kidney Foundation. 2018. Available from\: [LINK]
Ashby D, e t a l . Renal Association Clinical Practice Guideline Haemodialysis. The Renal Association. 2019 Jul. Available from\:
[LINK]
NHS. Dialysis. Last reviewed\: 2021 Sep. Available from\: [LINK]
Krause RS. Dialysis Complications of Chronic Renal Failure. M e d s c a p e . Last updated\: 2023 Nov. Available from\: [LINK]
Headache attributed to disorder of homeostasis. The International Classird
Available from\:
[LINK]
Survival and Cause of Death in Adult Patients Receiving Renal Replacement Therapy. The Renal Association UK Renal
Registry. Available from\: [LINK]
Bhandari SK, e t a l . Causes of Death in End-Stage Kidney Disease\: Comparison between the United States Renal Data
System and a Large Integrated Health Care System. A m e r i c a n J o u r n a l o f N e p h r o l o g y 2022 Mar;53(1)\:32-40.
Saravanan P, Davidson NC. Risk Assessment for Sudden Cardiac Death in Dialysis Patients. C i r c u l a t i o n \: A r r h y t h m i a a n d
E l e c t r o p h y s i o l o g y 2010 Oct;3(5)\:553-559.
Image references
Figures 1 - 4. Deborah Grove
Figure 5. YassineMrabet. A diagram of a haemodialysis circuit. License\: [CC BY-SA]

Reviewer

Dr Roberta Callus
Consultant Nephrologist
Deborah Grove
Consultant Nurse for Renal Medicine

Acute Kidney Injury (AKI)
Chronic Kidney Disease (CKD)
Glomerular Disease (Glomerulonephropathies)
Henoch-Schönlein Purpura (IgA Vasculitis)
Hyperkalaemia

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