Catheter blocking

• Smaller volumes of urine cause higher concentrations of debris which can lead to blocking
• Oral intake as well as output such as sweating can affect output volume

Recommendations:

• Ensure a consistent fluid intake – 2-3 litres of water a day is recommended

Poor flow can lead to an increase in the incidence of encrustations as the urine:

• settles in the tubing, promoting blockage from static debris
• has more contact time with the catheter which causes a biofilm to form

Recommendations:

• Empty the drainage bag regularly as flow can be affected when the bag is two thirds full
• Promote free drainage by ensuring no kinks in the tubing and that the drainage bag is lower than the bladder
• Elevate feet during the day to reduce lower limb oedema
• Ensure a constant intake of fluids
• Limit diuretics

• Bacteriuria or colonisation of the urine can develop as soon as 48 hours after the catheter is inserted
• Colonisation is common with E coli, Pseudomonas aureginosa, Proteus, Klebsiella, Provedincia.
• Bacteria floating in the urine are planktonic and can be treated with antibiotics
• A biofilm is a living layer that is described as slimy and glue-like, is caused by the micro-organisms colonising on the synthetic surface of the catheter and tubing
• The growth of the biofilm is promoted by the moist environment. Poor urine flow also allows longer contact time with the bacteria and the catheter to form the film
• The bacteria that form the biofilm are genetically different as they produce secretions that 'cement' the biofilm making it impervious to antibiotic therapy
• The urine can re-colonise after antibiotic treatment has been completed
• Despite having a closed urinary drainage system, colonisation can develop within four weeks of the catheter change

Recommendations:

• Maintain clean catheter technique when changing catheters
• General hygiene is also important
• A closed catheter system postpones bacteriuria or bacteria growth in the urine. A closed system is a one-way flow of urine from the bladder and there are no breaks in the system
• Regular catheter changes will prevent colonisation
• If possible, change the catheter when commencing antibiotic therapy

• The normal pH averages 6.0 but can range from 4.5—8.0.
• There is considerable encrustation at pH less than 6.7
• The activity of urease is dependent on pH. Urease is more active in an acid pH causing more urea to convert into ammonia
• Ammonia in solution is alkaline
• Ammonia also damages the protective layer of urothelial cells which defend against infection
• Urease producing bacteria are:
  • Proteus mirabilis, Morganella morganii, Provedencia stuartii, Klebsiella pneumoniae, Proteus rettgeri, Proteus vulgaris, Staphylococcus aureus
• Urease producing bacteria also lead to a higher risk for calculi formation
• There is no evidence to suggest a balanced diet and moderate intake of food groups has any bearing on urine pH
• Medications and oral solutions such as antacids, urinary alkaliniser and diet soft drinks that contain citrate and can cause the urine to be more alkaline

Recommendations:

• Take a measurement of the urine pH
• Take a micro-urine to detect any urease producing bacteria
• If a urease producing organism is present, alkaline therapy such as citrates or sodium bicarbonate may reduce crystallisation and subsequent blockages

• Encrustation is the development of crystals in the catheter tubing
• There are two types of encrustration. These are:
  • Struvite (magnesium ammonium phosphate)
  • Apatite (calcium phosphate)
• Calcium salts are a large component of catheter encrustations
• Struvite, not developed from a biofilm, is reversible. It is only reversible if the urine is low in phosphate, magnesium and calcium salts or the urine is acidified.
• Non blockers have a wider safety margin between their normal urine pH and that at which crystallization occurs (~1.4 variance in pH)
• The phosphate precipitates or separates in the solution and stops forming crystals. This happens in alkaline urine and starts at pH values of 6.7 and peaks at pH of 7.5

Recommendations:

• Antibiotic therapy is not effective with encrustation and long-term use can lead to developing resistant bacteria
• Encrustations are less pronounced on silicone and hydrogel catheters
• Moderate the intake of magnesium and calcium in the diet. Magnesium is found in diet soft drinks, herbal teas and fruit juices. A high calcium diet also contains more potassium, phosphate and magnesium which can contribute to the encrustation
• Performing a bladder washout with saline or water to remove the debris or crystals has limited supporting evidence and is more likely to cause spasticity and mucosal irritation.
• Some commercial acid-based and antimicrobial irrigation preparations can be helpful (e.g. Suby G/R, Microdox, PHMB) if administered as per the manufacturer's recommendations.