Peritoneal dialysis in practice
The day I had scheduled Wednesday's Facebook and Instagram post on renal function to go out, we ended up performing peritoneal dialysis in my practice. This isn't something I have done often, but it's a cool procedure and one which is fantastic from a nursing point of view, so I wanted to share some points with you!
Peritoneal dialysis (PD) is most commonly performed in patients with acute kidney injury (AKI) where haemodialysis is not possible/available. Though, its use has been reported less commonly in other conditions.
How does it work?
The peritoneum is a partially permeable membrane which forms the lining of the abdominal cavity and lines the abdominal organs. Through this partially permeable membrane, substances can diffuse (via osmosis).
The principle of PD is that we instil a solution (dialysate) causing substances (metabolites, toxins, etc) to diffuse from an area where they are in high concentration (e.g. the bloodstream), to an area of low concentration (the dialysate) across this membrane. The dialysate is then removed, and with it, these harmful substances.
So how is it done?
A catheter is placed surgically and aseptically connected to a 3-way tap, sterile fluid collection system, and sterile fluid line and dialysate bag. The dialysate fluid can either be bought commercially or created using a mixture of Hartmann's solution, and varying concentrations of glucose. Heparin may also be added to prevent clotting of the catheter.
Set volumes of dialysate are instilled over a carefully controlled period, ideally with an infusion pump. Following this, the fluid is left in the abdomen for a specific period of time, before the catheter is opened to the fluid collection system and drained, again for a specific period of time.
Nursing Considerations
This process is incredibly labour-intensive for nurses and there are a lot of nursing considerations for us to keep in mind:
Aseptic Technique
The patient's lines, connectors, dialysate and fluid collection system must be handled and assembled aseptically. Sterile gloves must be worn whenever they are handled, any connections must be wrapped in alcohol-soaked or chlorhexidine-soaked swabs and tape, the system must not be disconnected at any point, and the dialysate solution, fluid collection system and lines must be changed every 24 hours. Lines should be wiped over with chlorhexidine solution every 4 hours. Dressings should be replaced every 12-24 hours and the peritoneal catheter site inspected for signs of redness, swelling, thickening or fluid leakage. At the beginning of each PD cycle (known as an exchange), the fluid collection bag should be flushed with dialysate, to flush out any bacteria which may be present in the collection system.
Careful Management of Lines and Catheters
These patients have many lines and in addition to the PD system, they will generally have a urinary catheter, and a peripheral or ideally central venous catheter. All lines must be clearly labelled at both the patient end and the bag/syringe end of the line. The PD system should be labelled clearly so that dialysate in, dialysate out, and the catheter can be easily identified. Urine bags and PD collection bags should also be clearly labelled.
The number of lines attached to these patients means they can become tangled easily, so patients should be monitored closely and repositioned as needed to prevent this.
Monitoring Temperature
These patients can become very cold if care is not taken when instilling dialysate. The fluid should be warmed prior to instillation and a fluid warmer used. The patient's temperature should be monitored regularly and warming utilised to prevent hypothermia.
Monitoring Fluids in and Fluids out
The volumes of dialysate instilled in and retrieved should be carefully measured and recorded, and balances recorded for each exchange (PD cycle). These should be compared with general fluids in (IV fluids + enteral fluid intake) and urine output.
General Patient Monitoring
In addition to monitoring the patient's temperature and wound/catheter site, regular vitals should be obtained. Elevations in respiratory rate and alterations in respiratory effort should be monitored for. Heart rate and respiratory rate should be monitored every 1-2 hours, and blood pressure and temperature should be assessed 3-4 times daily. The patient's hydration parameters should be regularly assessed and they should be weighed at least twice daily to evaluate fluid balance. Blood samples should also be collected regularly to assess renal parameters, electrolytes and acid/base status; due to the frequent blood sample requirements, a central venous catheter should ideally be placed, to avoid repeated venipuncture.
References
Advanced Monitoring and Procedures for Small Animal Emergency & Critical Care, Burkitt Creedon & Davis, 2012.
Peritoneal dialysis in Veterinary Medicine, Cooper & Labato: https://www.vetsmall.theclinics.com/article/S0195-5616(10)00152-X/fulltext
Peritoneal Dialysis in Cats with Acute Kidney Injury: 22 Cases, Cooper & Labato: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2010.0655.x
