Peritoneal dialysis

A slow form of dialysis, utilising the peritoneum as the dialysis membrane. It is now rarely used in UK Critical Care Units, having been largely superseded by continuous haemofiltration. The technique does not require complex equipment although continuous fl ow techniques do require continuous generation of dialysate. Treatment is labour-intensive and there is considerable risk of peritoneal infection.

Peritoneal access

For acute peritoneal dialysis, a trochar and cannula are inserted through a small skin incision under local anaesthetic. The skin is prepared and draped as for any sterile procedure. The commonest approach is through a small midline incision 1cm below the umbilicus. The subcutaneous tissues and peritoneum are punctured by the trocar which is withdrawn slightly before the cannula is advanced towards the pouch of Douglas. In order to avoid damage to intraabdominal structures, 1–2L warmed peritoneal dialysate may be infused into the peritoneum by a standard, short intravascular cannula prior to placement of the trocar and cannula system. If the midline access site is not available, an alternative is to use a lateral approach, lateral to a line joining the umbilicus and the anterior superior iliac spine (avoiding the inferior epigastric vessels).

Dialysis technique

Warmed peritoneal dialysate is infused into the peritoneum in a volume of 1–2L at a time. During the acute phase, fluid is flushed in and drained continuously (i.e. with no dwell time). Once biochemical control is achieved, it is usual to leave fluid in the peritoneal cavity for 4–6h before draining. Heparin (500IU/L) may be added to the fi rst six cycles to prevent fibrin catheter blockage. Thereafter, it is only necessary if there is blood or cloudiness in the drainage fluid.

Peritoneal dialysate

The dialysate is a sterile balanced electrolyte solution with glucose at 75mmol/L for a standard fluid or 311mmol/L for a hypertonic fluid (used for greater fluid removal). The fluid is usually potassium-free since potassium exchanges slowly in peritoneal dialysis although potassium may be added if necessary.

Complications

• Fluid leak                          Poor drainage

                                 Corticosteroid therapy

                                           Obese or elderly patient

• Catheter blockage              Bleeding

• Infection                           White cells >50/mL, cloudy drainage fluid

• Hyperglycaemia                  Absorption of hyperosmotic glucose

• Diaphragm splinting

Treatment of infection

It is possible to sterilise the peritoneum and catheter by adding appropriate antibiotics to the dialysate. Suitable regimens include:

• Cefuroxime 500mg/L for two cycles, then 200mg/L for 10d.

• Gentamicin 8mg/L for one cycle daily.