PRINCIPLES OF URINARY CATHETERISATION

Over the last 40 years significant advances have been made in catheterisation. These can be summarised under the following heading:

Urinary catheters were initially fixed in the bladder and allowed to air, or at least to drain into a bottle placed on the floor. Urinary infection would occur because concentrated growths of organisms would occur in the bottle. Urine would be then pushed back up the tube into the bladder and this would predispose to infection.

As a rule of thumb it is generally appreciated that with open indwelling catheter drainage urinary infection will occur in 100% percent of patients within three days.

In the 1950’s and early 1960’s urologists took a special interest in this and insisted that their patients have closed sealed catheter drainage. This improved the situation with closed sealed catheter drainage so that with closed catheter drainage into a bag one would expect 100% of the patients to be infected in approximately 14 days rather than three days. Over the next 10 to 15 years doctors came to appreciate that they could delay the onset of these infections a little by using antibiotics, but that delay was very little and the type of organisms found in the bladder were more resistant to infection if antibiotics were used as a means of treating these infections.

The next biggest change came in the early 1970’s under the guidance of Dr Lapides. He introduced a concept of draining the bladder frequently in preference to leaving an indwelling tube in the bladder. He understood that an indwelling tube in the bladder would predispose to organisms travelling up into the bladder inside the tube as well as travelling in the space between the tube and the urethra.

By introducing intermittent catheterisation the majority of the population are free from infection for most of the year. It has become well established that in male patients the average infection rate is close to 1%. This means that out of every 1000 catheterisations a significant degree of infection is seen on 10 occasions, as normal patients catheterise themselves approximately 4 times a day, and as there are 365 days in a year these patients will normally catheterise themselves 1500 times a year. It is therefore to be expected that one will see approximately 15 events a year where infection can be confirmed to be present in the patient’s bladder if one is looking for this in catheterised patients using intermittent catheterisation. This represents an enormous improvement compared to a situation where a patient would have an indwelling catheter. If the patient with an indwelling catheter for a year had regular samples taken the samples would be infected 100% of the time rather than 1% of the time.

Infection is defined as more than 10⁶ - i.e. more than 100,000 organisms per mL. The concentration of organisms in the bladder is a dynamic process which depends upon how many organisms remain in the bladder after the bladder is emptied.

The number of organisms that remain in the bladder relate to the concentration of organisms in the bladder prior to the bladder being emptied, and relate to the volume of urine that remains in the bladder after the bladder is emptied. This can be minimised by making sure that the bladder is pressed firmly by the patient to empty all fluid out of the bladder at the end of catheterisation.

In addition to draining organisms out of the bladder it is important not to push organisms into the bladder, and it is obviously important not to have organisms on the catheter at the time that it is introduced into the bladder. In this area the addition of a silicone tip which protects the catheter from contamination has been a significant advance for management of patients. At lease six trials have been necessary to try and validate the information relating to this.

The number of organisms in the bladder increase by 2 times in the first 20 minutes, and 2 times in the second 20 minutes, and again 2 times in the third twenty minutes so that the actual number of organisms have increased 8 times within the first hour. In the first hour if only 2mL of urine was present in the bladder at the beginning of the first hour then it will be 102mL at the end of the first hour. This means that the volume of urine in the bladder has increased by 50 times in the first hour and the number of organisms will have increased by 8 times. In the patient who has poorly emptied his bladder and left 50mL of urine in the bladder then at the end of the first hour then he will have 150mL in the bladder which means that the volume will have increased to three times its original size but the number of organisms will have increased by 8 times. It is therefore important that if the concentration is to drop in the first hour that the volume left in the bladder was very low.

After the first hour the volume of urine in the bladder tends to increase from just over 100mL to 200mL and yet the organisms increased by 8 times in the second hour. For this reason there is a very fast rise in organisms in the second hour. Every hour from then on the total number of organisms in the bladder rises approximately 8 times and the concentration of the urine rises close to 8 times each hour. If a patient who catheterises himself every 8 hours is compared to one who catheterises himself every 4 hours the risk of infection in the bladder is 2000 times higher with the individual catheterising himself every 8 hours. This is because we are dealing with a doubling every 20 minutes.

From a practical point of view it is very useful to take a stand on behalf of Proctor and Gamble to state that if we are going to reduce the problem of urinary tract infection a silicone tip to bypass the distal urethra organisms is only one of the important tools.

Probably the most important tool is a teaching and training programme to emphasis to patients that the interval between catheterisation should be kept as low as possible and in all cases less than 6 hours if it is practical in patients who have catheter induced infections, then if their infections are not under control one should insist that they keep to 4 hourly catheterisation. This is obviously difficult for a group of patients.

In addition to this, the volume of fluid that the patient drinks will affect how much urine is being produced each hour. The more urine that is produced each hour the more dilute the mixture of organisms and this may be an additional factor which decreases the risk of infection. Keeping the instruments clean appears to be moderately useful but bypassing the organisms of the urethra is probably more significant itself than keeping the instruments clean.

Only over the last 5 years has significant data accumulated to show that bypassing organisms in the urethra is a significant addition. By referring to the various studies one can quote a variety of incidents of infection but the general trend is to be able to decrease the incidents of infection from 0.9% or 1% down to approximately 0.6%. The best study to validate this is a randomised prospective study undertaken at Ranchos Los Amigos Hospital and published in 1985 by Nancy Young. This study, as well as 4 or 5 other studies shows a significant decrease of infection in patients using the urinary catheter introducer. It should be remembered that the studies undertaken at Ranchos Los Amigos at Texas Rehabilitation Institute in Washington and in Toronto involve a combination of patients who are associated with rehabilitation hospitals. Most of these patients will be doing self catheterisation rather than actually being catheterised by the nurse. The data shows a substantial decrease from 0.9% to 0.6% in the patients involved. These were not specifically patients admitted for control of urinary tract infection.

We would therefore expect a decrease in urinary tract infection of approximately 30% by introducing the catheter tip. This should lead to the average patient experiencing 8 or 9 events where significant bacteria is present. During a 12 month period this should lead to a decrease which is much more significant than this than in the patients with a strong predisposition to urinary tract infections.

In practice, the patients that have frequent urinary tract infections will benefit by a programme using the O’Neil Catheter, especially if it is combined with an active teaching programme to catheterise more frequently. The trial results to-date suggest that 30% gain will be achieved even if they do not catheterise more frequently. It remains my opinion that combining an appropriate training programme plus the product will offer the best chance of making an impact with the market.

I hope these notes are useful.