General | July 10, 2015 | Author: The Super Pharmacist
Dialysis is the process of removing waste and excess water from the blood. It is primarily used medically in patients as an artificial replacement for the kidney function, and as such is commonly used in individuals who have experienced kidney failure. It is most commonly used in patients who have progressive, often worsening kidney conditions (such as chronic kidney disease) or an acute injury (such as acute renal failure, caused by an obstruction to the urinary tract).
There are two main types of dialysis – haemodialysis (in which blood is filtered using a dialyser and a dialysis machine) and peritoneal dialysis (in which blood is filtered within the body, after the abdomen is filled with a sterile solution).
Haemodialysis can be offered on both an inpatient and outpatient basis, with patients who are able to self-manage their own condition able to keep dialysis equipment at home. In this situation, dialysis will often be undertaken whilst the patient is asleep (‘nocturnal daily haemodialysis’) and lasts for between 6-8 hours, and is performed between 3-7 times a week depending on the severity of condition.
Most guidelines recommend at least 3 sessions of haemodialysis per week where renal failure is present, typically for between 3.5-4 hours (1). To monitor the effects of dialysis, patients both at home and in hospitals often submit measurements regarding the dose and efficacy of their haemodialysis to inform periodic medical reviews. Many renal networks, or groups of physicians, will often use this data to perform clinical and administrative audits to identify areas of good practice. Similarly, post-dialysis blood sampling is also important for monitoring dialysis performance, and is obtained by health professionals via a procedure known as the stop-dialysate flow method. A number of other monitoring indices are also taken throughout the process of dialysis to monitor how well patients are responding to treatment. This includes pre-dialysis biochemical parameters, serum bicarbonate concentrations, serum potassium, serum phosphate, serum calcium, and haemoglobin concentration (2).
Peritoneal Dialysis involves a sterile solution called dialysate being run through a tube into the peritoneal cavity (the abdominal cavity around the intestine), with the process of osmosis and diffusion pushing waste products through the peritoneum into the dialysate which is then drained and replaced with fresh dialysate. This will typically occur 4-5 times per day (3).
There are two main forms of peritoneal dialysis: Continuous Ambulatory Peritoneal Dialysis (CAPD) in which dialysis solution is placed into a catheter as the patient undertakes their everyday activities, and Continuous Cycler-assisted Peritoneal Dialysis CCPD) in which a cycler machine fills and drains the solution from the patient’s abdomen whilst they sleep. Peritoneal Dialysis is a less efficient form of dialysis than haemodialysis. As such, it tends to run on longer cycles in order to process similar amounts of waste, and it is most frequently administered at home so that patients do not have to frequently attend clinics.
Many of the same markers used in haemodialysis to monitor performance are also undertaken when peritoneal dialysis is often being administered, although they are generally taken less frequently due to it largely being a form of treatment undertaken at home. Frequency of dialysis is determined by a number of patient characteristics such as kidney function, fluid gained since previous dialysis, weight, and the waste that has accumulated in the blood since the previous dialysis session. The function of the peritoneal membrane must also be monitored throughout treatment, as changes in its structure and efficiency can sometimes lead to complications such as peritoneal sclerosis. The permeability of the membrane can vary greatly between patients, and is strongly correlated with patient morbidity and mortality (4).
The decision on whether or not patients should undertake dialysis is not something that a physician will take lightly. Whether or not dialysis should be undertaken, and which particularly dialysis should be undertaken, should be discussed in conjunction with patients and a decision should be made based on their medical condition, lifestyle factors (including capacity for self-care), and professional judgement.
A number of acute or chronic conditions may precipitate dialysis: a common framework for deciding if dialysis is required in cases of acute illness is often determined using a clinical guideline commonly referred to as ‘AEIOU’. This refers to a number of indications that are important when reviewing kidney function (5):
Acidemia (increased acidity in the blood and tissue) in situations where sodium bicarbonate cannot be used to address to the condition due to concerns over fluid overload
Electrolyte irregularities i.e. severe hyperkalemia (elevated levels of potassium in the blood)
Intoxication (poisoning) with a substance that can be removed from the body by dialysis (i.e. isopropanol, ethylene glycol, salicylic acid)
Overloads of fluids that would not typically respond to treatment with diuretics
Uremia (urea in the blood) complications such as encephalopathy and pericarditis (inflammation of the fibrous sac around the heart)
There is very little comparative literature between different dialysis, largely in recognition of the fact that their administration depends less on which method is more efficacious than the other, and more around what is most suitable for each patient and their individual circumstances. There is some literature around patient experience of dialysis, with peritoneal administration consistently preferred on account of its ease of use and reduced hospital visits (6). Most literature focuses on comparative risks, benefits and questions of access rather than efficacy between both methods. There is a sizeable evidence base examining the type of solutions used in peritoneal administration and their impact on patient outcome (7).
1. The Renal Association: Haemodialysis http://www.renal.org/guidelines/modules/haemodialysis#sthash.jrcvaQRK.dpbs (last accessed 27th June 2015)
2. Brunelli SM, Sibbel S, Do TP, Cooper K, Bradbury BD (2015) Facility Dialysate Calcium Practices and Clinical Outcomes Among Patients Receiving Hemodialysis: A Retrospective Observational Study Am J Kidney Dis doi: 10.1053/j.ajkd.2015.03.038 (Epub)
3. NICE Guidelines [CG125] Peritoneal Dialysis: Treatment of Stage 5 Chronic Kidney Disease https://www.nice.org.uk/guidance/cg125 (last accessed 27th June 2015)
4. Churchill DN, Thorpe KE, Nolph KD, Keshaviah PR, Oreopoulos DG, Pagé D (1998) Increased peritonealmembrane transport is associated with decreased patient and technique survival for continuous peritoneal dialysis patients J Am Soc Nephrol 9(7):1285-92
5. Irwin RSS, James MR (2008) Irwin and Rippe's intensive care medicine. Lippincott Williams & Wilkins. pp. 988–999
6. Sinnakirouchenan R, Holley JL (2011) Peritoneal dialysis versus haemodialysis: risks, benefits, and access issues Adv Chron Kid Disease 18(6):428-32
7. Rodrigues A (2009) Cost benefits of peritoneal dialysis in specific groups of patients Contrib Nephrol doi: 10.1159/000223812