There is an increasing prevalence of end-stage kidney disease and it is therefore likely that you will be involved in the care of dialysis patients. Dialysis patients can be quite complex and daunting to deal with as a newly qualified doctor. Often, you will also need to refer to the renal team, but here is a practical guide for common issues you will likely have to deal with. Some common medical emergencies in dialysis patients are described with guidance on when to refer to the renal team. The important thing as a junior doctor is recognising an urgent situation, escalating appropriately and initiating the basic immediate management. You should escalate ALL cases to your seniors.
Types of Dialysis
Before going into the medical issues in dialysis patients, here is a recap of some of the basic terminology. Dialysis is a form of renal replacement therapy (RRT), which is initiated to take over the role of the human kidneys. This can be long-term/permanent in the case of end-stage kidney disease or temporary in severe acute kidney injury to allow time for the kidneys to recover. RRT serves two main functions: (i) to normalise blood biochemistry (hyperkalaemia, acidosis, uraemia) and (ii) to remove excess fluid.
Haemodialysis (HD): blood is removed, ‘equilibrates’ with dialysate across a semi-permeable membrane and the ‘cleaned’ blood is given back to the body. HD machines are also capable of ultrafiltration (UF), to achieve a net fluid loss. Some form of vascular access is needed for HD. Preferably, this is an arterio-venous (AV) fistula (a surgical connection between artery and vein to allow regular wide-bore cannulation). Another option is a central venous catheter (CVC); these can go straight into the vein (non-tunnelled, NTCVC, inserted in the ward using US) or can be tunnelled under the skin before entering the vein (TCVC; inserted by interventional radiology). Dialysis lines must have at least two lumens and are wider bore than ‘medical’ CVCs. The last option is an AV graft, which is like a fistula, but involves synthetic material which can be cannulated.
Peritoneal dialysis (PD): the peritoneum is used as the semi-permeable membrane. Dialysate fluid is put into the abdominal cavity (via Tenckhoff catheter) and left to equilibrate with blood across the peritoneal membrane. Two types: (i) continuous ambulatory PD (CAPD) which involves 3-5 manual exchanges throughout the day and (ii) automated PD (APD) where exchanges are done by a machine overnight.
Haemofiltration (HF): a type of RRT, but not strictly speaking dialysis. Practically this is similar to HD in that you need vascular access, but instead of dialysis across a semi-permeable membrane, fluid is removed by UF and then ‘clean’ fluid is added back. Typically, HF is used in the critical care setting and tends to be continuously running in the background (‘CVVHF’).
In the general medical inpatient setting, the most common form of RRT you will come across is HD. This guide will focus mainly on haemodialysis patients with end-stage renal disease. AKI patients dependent on RRT tend to be managed in specialist renal units.
‘Clerking in’ a dialysis patient
There are several pertinent considerations when admitting a dialysis patient to the hospital. Knowing these facts will also help when making a referral to the Renal team:
What type of dialysis? i.e. HD or PD?
What vascular access do they use for dialysis?
TCVC, AV fistula or AV graft? Always ensure to examine their access site for signs of infection. Note that dialysis lines should not be used for routine administration of IV drugs/fluids or to draw blood due to risk of infection. Fistulas/grafts should not be cannulated or used for drawing blood and you should not put a tourniquet or blood pressure cuff over these.
What is their normal dialysis schedule?
Most HD patients will dialyse 3x/week (usually Mon/Wed/Fri or Tues/Thurs/Sat). When they are next ‘due’ for dialysis will be important to know for planning dialysis.
What is their ‘dry weight?’
AKA ‘target weight’ or ‘ideal body weight.’ This is the bodyweight when euvolemic (i.e. without any signs of fluid overload) and is used as a guide by dialysis nurses for how many litres of UF is needed. E.g. if a patient is 77kg pre-dialysis and their dry weight is 75kg, the nurse will aim for 2L of UF. This may need to be adjusted in patients with weight loss.
Where do they normally dialyse?
Most patients will attend an outpatient dialysis centre (which could be in the same hospital but not always); some will dialyse at home. If the patient is admitted, you will need to arrange dialysis for them. They might be able to attend their normal dialysis slot if it’s in the same hospital and they are well enough to attend. If not, you will need to liaise with the local dialysis unit and/or renal team to make appropriate arrangements. The person to contact varies between hospitals but there is often a separate renal doctor on-call for dialysis than for general renal advice. Unwell or unstable patients will likely need to be transferred to the Renal Ward and dialysed there as the outpatient areas do not usually have any medical cover.
Dialysis-specific medications. HD patients will have medications to be given on/after dialysis. These are usually given by the dialysis centre nurses so may not be on the GP repeat prescription. These should still be included in your medicines reconciliation and prescribed on their drug chart. Common examples include an IV erythropoiesis-stimulating agent (e.g. darbepoetin), IV iron and oral alfacalcidol.
Tips for inpatient management of dialysis patients
Starting new medications
Many drugs are contraindicated in renal impairment and may be dialysed. Therefore, dose adjustment or timing adjustment (e.g. to be given after dialysis) may be necessary. A good first port-of-call is the Renal Drug Handbook. If in doubt, discuss with pharmacists/renal team. Common drugs to avoid – morphine, NSAIDs, trimethoprim (hyperkalaemia), nitrofurantoin, metformin (lactate acidosis), DOACs.
Interpreting renal function tests
Dialysis patients are usually anuric/oliguric and have close to no residual renal function. Creatinine and urea are cleared by dialysis and will rise between sessions. eGFR is calculated from serum creatinine so is a meaningless entity and should not be used. For medication dosing etc, assume a GFR of < 10 mL/min/1.73m2.
IV fluids and fluid restriction
Dialysis patients excrete minimal fluid between dialysis sessions and should have a fluid restriction in place (usually 500-1000 mL depending on residual urine output). IV fluids should be used with extreme caution and only when the patient is fluid deplete.
Remember not to perform venepuncture on a fistula! Fistulas are usually made in the non-dominant arm. Ideally use the dominant arm for venepuncture or cannulation. Using the back of the hand can preserve veins for future fistulas. Blood tests can also be taken during a dialysis session – liaise with the dialysis nurses.
Iodine-based contrast for CT scans may be nephrotoxic. For HD patients, this is fine as the contrast is dialysed out and there is minimal systemic toxicity – however, this must be timed appropriately. Gadolinium contrast for MRI scans is absolutely contraindicated (risk of systemic toxicity – ‘nephrogenic systemic fibrosis’).
Low molecular weight heparin is not routinely prescribed in HD patients, but if there is a strong indication (e.g. after hip surgery), then dose adjustment will be required.
If you need to give blood, products can be transfused during a dialysis session with ultrafiltration to compensate for the extra fluid; liaise with the dialysis nurses to arrange this. There is a risk of ‘allosensitisation’ to foreign antigens which is cumulative with multiple transfusions and complicate HLA matching for renal transplantation. Therefore, for dialysis patients that may be transplant candidates, blood transfusion should only be when absolutely necessary. If you are unsure whether a patient is a transplant candidate or not, check with the renal team.
Common Medical Emergencies in Dialysis Patients
Acute Shortness of Breath
The differential diagnosis for shortness of breath is much the same in dialysis patients compared to other patients, but there is an increased likelihood that this is due to pulmonary oedema secondary to systemic fluid overload. The breathless dialysis patient should be regarded as having pulmonary oedema until proven otherwise.
Clues in the history for fluid overload include a long gap since the last dialysis (e.g. presenting on Monday morning after dialysis on Friday), exceeding fluid restriction and missed dialysis sessions. Patients are often hypoxic, chest examination will reveal bilateral inspiratory crackles and there will be other signs of fluid overload (e.g. hypertension, elevated JVP, peripheral oedema).
Immediate management is similar in principle to the management of pulmonary oedema in patients with normal renal function, but with a few differences:
- Always ensure you consider acute myocardial infarction (which may present atypically)
- Oxygen should be given to correct hypoxia
- Nitrates (e.g. SL GTN or GTN IV infusion) can be given to reduce afterload but avoid if hypotensive
- Opioids can be given to relieve the sensation of breathlessness, but morphine should be avoided/used very cautiously. Usually, Alfentanil would be the preferred option
- The definitive management is fluid removal – they need to be dialysed urgently with ultrafiltration.
- Loop diuretics will not work if the patient is anuric but can be tried if there is some residual renal function.
- Contact the on-call renal registrar ASAP to arrange dialysis. If there is no facility for emergency dialysis (e.g. in a DGH), then in some cases emergency venesection may be necessary to relieve pulmonary oedema and stabilise the patient before transfer (remember ABCDE – hypoxia will kill before anaemia).
Potassium is cleared by the kidneys and patients with CKD and those on dialysis should be given dietary advice to keep oral potassium intake low. However, hyperkalaemia is still common in the dialysis population and should be managed urgently to reduce the chance of life-threatening cardiac arrhythmias. Again, the management is like patients with normal renal function, but it will not resolve on its own and the renal on-call should be contacted for urgent haemodialysis with cardiac monitoring (i.e. on the renal ward).
Serum K+ 5.5 – 5.9 mmol/L = mild hyperkalaemia; HD is needed same day
Serum K+ 6.0 – 6.4 mmol/L = moderate hyperkalaemia; requires urgent HD; perform ECG
Serum K+ ≥ 6.5 mmol/L = severe hyperkalaemia; urgent HD (insulin-dextrose if delay); perform ECG
Perform a 12-lead ECG to look for changes associated with hyperkalaemia (i.e. tall tented T waves, P wave flattening, prolonged PR interval, QRS complex prolongation) and give a bolus of IV calcium gluconate if changes present (10 mL of 10%; can be repeated if ECG changes persist). The patient should be kept on a cardiac monitor.
If there is a delay in arranging HD and hyperkalaemia is severe, then measures to shift potassium intracellularly should be considered i.e. insulin/glucose infusion (refer to local guidelines, but usually 8-10 units of soluble insulin e.g. actrapid in 100 mL 20% glucose) and/or nebulised salbutamol (5-10 mg). Note that dialysis will only remove serum potassium and not intracellular potassium, so there may be a rebound hyperkalaemia even after dialysis in patients who have had large amounts of insulin. Always check a post-HD potassium level.
Calcium resonium and other potassium binders are rarely used in the setting of haemodialysis but may occasionally be indicated if there is a delay in setting up dialysis.
When asked to review a HD patient with signs of infection or sepsis (e.g. fevers, tachycardia, hypotension, tachypnoea, raised inflammatory markers), always consider line infection in addition to the other common sites of origin.
Sepsis Six in the HD patient
- Oxygen therapy
- Empirical antibiotics: broad-spectrum to cover possible line infection
- IV fluids: use cautiously and only if signs of volume depletion. Give small boluses (e.g. 250 mL) and re-assess.
- Blood cultures: take peripheral cultures; TCVC cultures to be taken on dialysis
- Measure lactate level
- No benefit measuring urine output in the context of end-stage renal disease
The risks of infection are greatest with non-tunnelled central lines (used only for temporary access), then for tunnelled central venous lines (TCVC). Risks are greater for femoral than for neck lines. AV grafts are synthetic material and can also become infected. The risk is lowest for AV fistula infection.
The CVC site should be examined for signs of infection (erythema, tenderness, pus). Both gram-positive and gram-negative infections are common and broad-spectrum empirical antibiotics are needed (as per trust guidelines for CVC infection). Contact the Renal on-call team as the patient will likely need the line removed and a new line inserted (usually 48 hours plastic-free). Haemodialysis will need to be scheduled around line exchange and these patients are usually best managed in the renal ward.
- Review: Management of the dialysis patient for the hospital physician
- A useful summary of different types of dialysis: https://oscestop.com/Dialysis.pdf
- Renal Drug Handbook 5th Ed (save and have on your phone!): https://medicinainterna.net.pe/sites/default/files/The_Renal_Drug_Handbook_The_Ultimate.pdf
- Pulmonary Oedema
Written by Dr Sidhant Seth (FY1)
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