Haemodialysis cleans a patient’s blood (via removal of excess fluid and waste products) from outside of their body, using a haemodialysis machine. Sometimes, haemodialysis is required short-term in the case of an acute kidney injury secondary to an acute condition such as sepsis. Other times, haemodialysis is required long-term (indefinitely) for patients with end-stage chronic kidney disease secondary to diabetes or hypertension, for example.

Haemodialysis is a complex process and patients are managed by a multidisciplinary team of healthcare professionals. If we also consider these patients in the context of their (often numerous) comorbidities, we can understand that haemodialysis patients are particularly big users of our healthcare services.

First, patients require vascular access. This is achieved by one of the following methods:

Most patients will travel to a haemodialysis centre 3 times per week for their dialysis session. Most commonly, patient bookings are scheduled for a morning or afternoon session on either:

• Monday, Wednesday & Friday, or
• Tuesday, Thursday & Saturday

The length of the dialysis session can be varied depending on the patient’s requirements. However, most sessions take 4-5 hours. You can understand that this is a significant time commitment for patients and so very few are able to maintain full time employment.

During the haemodialysis session, the patient is connected to the dialysis machine.

1. The dialysate is pumped through the dialyser. Note: the electrolyte concentration of the dialysate may be altered depending on the patient’s individual requirements.
2. At the same time, blood is being removed from the patient and pumped through the dialyser in the opposite direction compared to the dialysate. ‘Clean’ blood is then returned to the patient.

Inside the Dialyser

The dialyser is a plastic chamber which contains bundles of capillary tubes within which the blood circulates. Outside of these bundles, the dialysate circulates in the opposite direction.

Solutes and excess fluid move from the blood into the dialysate fluid by diffusion and ultrafiltration.

• Diffusion: The passive transfer of small solute molecules (e.g., urea, creatinine, etc.) from an area of higher concentration (blood) to an area of lower concentration (the dialysate).
• Ultrafiltration: The removal of fluid from the blood due to a driving pressure across the semipermeable membrane..

Watch the video at the link below for a summary of these key points.

https://www.freseniusmedicalcare.com/en/media/multimedia/videos/understanding-hemodialysis-video

Haemodialysis is more efficient than peritoneal dialysis at removing drugs from the circulation. 

There are various physicochemical characteristics that influence the degree to which drugs are removed from the blood by haemodialysis.

1. Molecular weight
2. Water solubility
3. Protein binding
4. Volume of distribution

The type of dialysis membrane, blood flow rates, and dialysate flow rates also play a major role in determining the degree to which drugs are removed from the blood by haemodialysis.

In addition to the considerations outlined in the previous section on chronic kidney disease, there are some additional special considerations regarding the medication management of haemodialysis patients. These are not the same as for peritoneal dialysis patients.

Special considerations for haemodialysis patients include:

1. Hypotension. This is a common complication of dialysis. We can understand this if we remember that haemodialysis involves the removal of blood from the body. When blood is removed from the body (albeit temporarily) blood pressure can decrease. If we don’t have enough blood pressure, then we aren’t able to maintain blood flow through the circuit and the patient at the same time. Often, this will mean that dialysis needs to be slowed or stopped altogether. As pharmacists, it is essential that we consider the timing of administration of antihypertensive drugs. We often need haemodialysis patients to withhold their antihypertensive medications in the morning on their dialysis days. It is important that patients are provided with education regarding the indications for each of their medications. For webster packed patients it is important that the packs reflect the plan to prevent hypotension during the dialysis session.
2. Fluid balance. Haemodialysis patients will often have a fluid restriction and monitor their weights regularly. Sometimes patients gain too much fluid between dialysis sessions and so the dialysis ‘prescription’ (i.e., the dialysate composition, flow rates and/or session duration) requires modification in order to return the patient to their ‘dry weight’ (i.e., their ideal starting weight). Loop diuretics are only used if the patient is still producing some urine, in which case high doses are often required (e.g., furosemide 250mg BD (morning & midday)). For patients who are completely anuric, loop diuretics are ineffective and so should be ceased.
3. Renal function cannot be estimated from any equation because creatinine levels fluctuate (i.e., creatinine levels are high prior to dialysis and decrease after dialysis). We assume that the GFR is less than 10ml/min. When checking and recommending drug doses, pharmacists should consult specialist renal drug dosing references, e.g., the Renal Drug Database, as the recommendations also differ depending on the type of dialysis the patient is receiving. Moreover, the timing of doses in relation to the haemodialysis session should be considered so that drugs that are readily dialysed off are administered after dialysis. Similarly, laboratory test results (e.g., for electrolyte levels) should be interpreted in relation to (1) the time the blood was taken and (2) the time of the haemodialysis session.

Finally, don’t forget the importance of liaison with other members of the multidisciplinary team.

• Haemodialysis necessitates major changes to a patient’s lifestyle. Social workers play a very important role in helping the patient to maintain social and emotional wellbeing.
• Dietitians also play a massive role in helping to optimise the nutritional status of patients with end stage renal failure on dialysis (PD or HD). For example, they can provide patients with advice about how to safely avoid phosphate-rich foods while still ensuring adequate protein intake.

Always consider the patient’s individual treatment goals and how these influence your treatment recommendations when you are working with patients who have been diagnosed with renal disease!!! It’s important to remember that the treatment goals will be very different for:

• A patient with CKD stage 3b, vs
• A patient who has recently commenced on peritoneal dialysis, vs
• An anuric patient who has been receiving haemodialysis for the past 5 years.

Renal transplant is generally considered to be the preferred type of renal replacement therapy as it improves quality of life and can increase longevity. However, because patients with end-stage renal failure often have extensive comorbidities, only approximately 30% of patients are fit enough for both the transplant and the associated postoperative immunosuppression.

Only a kidney donated by a patient’s own identical twin would be genetically identical. In all other cases, the immune system recognises the transplanted kidney as ‘foreign’ and so attempts to destroy it. As such, patients require life-long immunosuppressive therapy to prevent organ rejection.

Immunosuppressive drug classes used to prevent organ rejection include:

• Corticosteroids
• Most commonly prednisolone/prednisone
• Antimetabolites
• Azathioprine
• Mycophenolate
• Calcineurin inhibitors
• Ciclosporin
• Tacrolimus
• Mammalian Target of Rapamycin (mTOR) Inhibitors
• Everolimus
• Sirolimus
• Biologic agents
• Antithymocyte globulins
• Basiliximab

There are many possible complications associated with immunosuppression to prevent organ rejection. These include:

• Cytomegalovirus (CMV)
• A common virus
• Rarely causes any problems in healthy people but can be fatal in immunosuppressed people
• The greatest risk is when:
• CMV-seronegative patients (R-) receive an organ from a CMV-seropositive donor (D+)
• CMV-seropositive patients (R+) receive T cell depleting antibodies
• Prophylaxis against CMV is prescribed according to local transplant centre procedure
• First line agent is valganciclovir (cytotoxic)
• Alternatives include ganciclovir (cytotoxic) and valaciclovir
• Duration of prophylaxis is generally 3-6 months following transplant

• Pneumocystis Jirovecii Pneumonia (PJP)
• Formerly known as Pneumocystis Carinii Pneumonia (PCP)
• A serious fungal infection of the lungs
• An opportunistic infection that affects immunosuppressed patients
• Prophylaxis against PJP is used in all kidney transplant recipients
• First line agent is trimethoprim with sulfamethoxazole
• Alternative agents include dapsone, atovaquone, and pentamidine (nebulised)
• Duration of prophylaxis can vary between transplant centres, but is generally lifelong
• Malignancy

Transplant medicine is complex.

• Patients should be on a combination of 3 immunosuppressants. A common combination is tacrolimus + mycophenolate +prednisolone. The combination regime is used (1) to target different parts of the immune system and (2) to enable each drug to be used at a relatively lower dose to help to prevent dose-related adverse effects (which can be life threatening!).
• It is very important to check that patients are adherent with their prescribed transplant medications to prevent rejection.
• Many transplant medications have a narrow therapeutic index and require therapeutic drug monitoring for dose optimisation.
• Many transplant medications also interact with other drugs. You should check for drug interactions every time you review a patient who has had any type of organ transplant in the past.