Question 28

College answer

Not available.

Discussion

a) 

Advantages:

• Anticoagulation is not required
• There is no immunogenic extracorporeal circuit
• Haemodynamically better tolerated
• Markedly decreased risk of dialysis disequilibrium syndrome
• Does not require an expensive machine
• Less nursing staff workload, as compared to CVVHDF
• The patient may remain ambulant while intermittent PD is in progress
• An unexpected source of glucose, for patients who need extra calories

Contraindications

• Recent abdominal surgery
• Acute severe pulmonary oedema or immediately life-threatening electrolyte derangement (eg. sever hyperkalemia)
• Peritoneal adhesions or previous major abdominal surgery is only a relative contraindication, as it only makes laparoscopic catheter placement more challenging.
• Patients who have diaphragmatic pleuroperitoneal connections (i.e. all the fluid will end up in the chest)
• Patients in severe respiratory failure, who are at the border of requiring mechanical ventilation
• Patients with intraabdominal sepsis or abdominal wall infections
• Pregnant patients
• Patients with poorly controlled diabetes
• Shocked patients will have poorer peritoneal blood flow, and therefore lower efficiency of dialysis via the peritoneal membrane.

Complications

• Peritonitis
• Perforation of a viscus (emergency catheter placement)
• Respiratory failure
• Pleural effusion
• Protein loss- up to 20g/day, or perhaps even higher if you have peritonitis
• Hypernatremia due to water removal
• Gastro-oesophageal reflux
• Poor solute clearance
• Catheter insertion site leakage
• Abdominal hernias

b)

Essential components of an acute PD prescription:

• Dialysate concentration: usually 1.5-2.5% dextrose,  up to 4.25% to increase fluid removal
• Exchange volume is the administered volume, and this is usually 2L (30-40ml/kg)
• Inflow time is the time it takes to fill the peritoneal cavity, and this is usually 15-30 minutes (200ml/min). 
• Dwell time is the period for which the exchange volume remains in the peritoneal cavity (30 -90 minutes)
• Outflow time depends on the volume and the catheter; it is a gravity-dependent drainage of dialysate fluid.
• Number of exchanges: 4-6 exchanges per day for a stable patient, more if rapid solute control is required