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Preventing catheter blockages
PREVENTING CATHETER BLOCKAGES
BARRY SIMPSON
My recent spate of catheter blockageshas beenstopped by taking 50mg Nitrofurantoin about 8pm daily and repositioning my catheter by pulling it forward immediately after going to bed to try to ensure that the intake is not being obstructed by my bladder wall. After taking 50mg per day for 30 days, I have been trying to determine the minimum effective continuation dose: so far, it appears to be no more than 3 or4x50mg tablets per week if supporting methods, listed on p6, are also used to keep my catheter clear. All of my blockages occurred before an infection had been demonstrated: using Nitrofurantoin to treat only proven infections looks unlikely to prevent many blockages.
WHAT CAUSED THE BLOCKAGES?
From January to July 2016 the misery of my spinal injury was aggravated by the torment of catheter blockages. Here are a few observations to help identify what had been causing them:
1 My suprapubic catheter was installed in May 2013, about 4 months after my spinal injury. I had no blockage during the first two years and eight months but I had 23 between 17/1/16 and 24/7/16. Towards the end of that period, they became more frequent.
2 All the blockages occurred soon after changing positions from sitting upright in my wheelchair to lying flat on my back in bed. On every occasion I have wakened up sweating and trembling with exceptionally violent spasms,usually between midnight and 1am.
3 The nurse has never taken more than a few minutes to unblock the obstruction.
4Only once has a blockage recurred during the same night. On this occasion, two nurses arrived at 10.50 and replaced my catheter which was choked with 'sludge'. At 2.40am I woke sweating again. The same nurses returned. This time the blockage was 'positional'.
5 There were at least two causes of the blockages - bacterial and physical obstruction.
BACTERIAL BLOCKAGES
6 For about half of the blockages, the nurse mentioned sediment and/or 'pus' as the likely cause. On some occasions, including the most recent, only 36 hours after a bladder wash-out, the nurse said there was no sediment.
7 My leg bag is supposed to be changed weekly. On 3 or 4 occasions, the nurse has mentioned a dirty leg bag, when the carers (and me) had forgotten about it or when we had run out of them.
8 I have never had a blockage on a night following taking any Nitrofurantoin during the day - but that was not very often until 24/7/16. On the morning following several of the blockages I have had a bout of sweating which has always been stopped by taking Nitrofurantoin. This seems to indicate that I had a urinary infection,andthat the infection was caused by bacteria which alsocaused the blockage the night before.A urine sample has never been taken at the time of a blockage or soon after. However, it seems likely that the bacteria killed by Nitrofurantoin created the sediment which resulted in most of the blockages. It is curious that I had no blockages between installation of my catheter in May 2013 and 17/1/16 despite having more than a dozen urinary infections during this period.
BLOCKAGES BY PHYSICAL OBSTRUCTION
9 Weekly bladder wash-outs were started soon after the blockages began. I have never had a blockage on the following night, but I have had them soon after.
10 For about half the blockages, the nurse mentioned a physical obstruction, such as a collapsed tube. I do not know why physical obstructions were absent from May 2013 until January 2016. Maybe there was a change in type or brandof catheter in December 2015 or January 2016?
11 For the most recent blockage, the nurse offered the following explanation:the end of the catheter tube might be pressing up against my bladder wall, so obstructing the intake.This fits well with what two or three other nurses have said: 'I'm not sure what caused the blockage but wiggling the catheter where it enters the bladder seemed to unblock it'.
AN INITIAL TRIAL: 15th JULY - 12th AUGUST 2016
From 17/1/16 to 24/7/16 I had 23 blockages, including 6 from 15 - 24/7/16.It seemed that infections by bacteria were responsible for the majority of the blockages (point 8 above)and the position of my catheter for the others(point 11). It is likely that some blockages were caused by a combination of the two: a constriction not severe enough to block the flow of urine caused sediment to collect on the upstream side and this caused a blockage.
Since 24/7/16 Ihave taken50mg Nitrofurantoin each day at about 8pm to allow time for it to take effect beforemoving from wheelchair to bed(point 8) and pulled my catheter forward away from the bladder wallimmediately after going to bed(point 11). From 24/7/16 - 12/8/16I had no blockage in 20 nights.
SoWITHOUTNitrofurantoin and catheter repositioning: 10 nights, 6 blockages;
WITHNitrofurantoin and catheter repositioning: 20 nights, no blockage.
It looks obvious that there is a connection between Nitrofurantion/catheter repositioning and stopping blockages. The strength of the evidence can be measured like this:
what are the chances of having 6 blockages on the first 10 nights (without Nitrofurantoin) and none on the following 20 (with Nitrofurantoin) if Nitrofurantoin and catheter repositioninghad no effect?
That can be calculated like this:
if there had been just one blockage, the chances of it being in the first 10 nights would have been 10 divided by the total number of nights (30) = 0.3333;
if there had been two blockages the chances of both of them being in the first 10 nights would have been 0.3333 multiplied by 0.3333 = 0.1111 and so on ...... until
the chances of 6 blockages all being in the first 10 nights is 0.3333 multiplied by itself five times or 0.33336= 0.0014, that is 14 chances in 10000 or 1 chance in 714.
This can also be calculated using the binomial distribution where the probability of success for a single trial is again 10/30 = 0.3333, the number of trials is 6 (the number of blockages on all 30 nights) and the number of successes (hardly the right word for a catheter blockage - the number of blockages during the first 10 nights)is also 6.
The probability just calculated is 'if there is no association between Nitrofurantoin and catheter blockages, what are the chances of getting 6 blockages in the 10 nights without Nitrofurantoin?' It can also be calculated the other way round: what are the chances of there being no blockage in 20 nights with Nitrofurantoin if lack of blockagesis not associated with it? In this case, the probability of success for a single trial is 20/30 = 0.6667 the number of trials is 6 (the number of blockages on all 30nights) and the number of successes (the number of blockages on the last 20 nights) is 0. The answer is the same, that is, probability = 0.0014.
The multinomial distribution can also be used with 2 outcomes (blockage/ no blockage) probability of outcome 1 (blockage) is 10/30 = 0.3333; frequency of outcome 1 (number of blockages when not taking Nitrofurantoin) = 6; probability of outcome 2 (no blockage) is 20/30 = 0.6667; frequency of outcome 2 is 0 (the number of blockages when taking Nitrofurantoin). The answer is the same as before (p = 0.0014).
This too can be calculated the other way round: outcome 1 (no blockage, probability 0.6667, frequency 0); outcome 2 (blockage, probability 0.3333, frequency 6) with the same result.
So for the 30 nights of the trial, it is possible to say that taking Nitrofurantoin and catheterrepositioning were associated with stopping my catheter blockages with only a very small chance of being wrong(probability 0.0014) which is 1 chancein 714.
That was the situation on 13/8/16. It is changing every day. If I have a blockage, the chances of the statement being wrong will increase. If I do not have a blockage, the chances of the statement being wrong will become even smaller; for example when the number of nights without a blockage reached 50 (12th September), the probability became (10/60)6 = 0.16676 = 0.000021, that is 21 chances in a million or 1 in 47,619.
Such probabilities as p = 0.0014 or p = 0.000021 do not predict the frequency with which I can expect a blockage; neither do they predict the proportion of patients with a condition the same as mine having their blockages stopped. Allthey mean is that in my case, it is almost certain that taking Nitrofurantoin and repositioning my catheter have reduced the chances of getting a blockage: p = 0.000021 (the probability of there not beingan association) or 1-p = 0.999979 (the probability of there being an association)are measures of the chance that Nitrofurantoin and catheter repositioning are associated with catheter blocking;they are not measures of what that association is, that is, how much they reduce the chances of a blockage.
Sofor patients with a conditionthe same asmine, the treatment can be expected to reduce the frequency of blockages for almostall of them.
It is possible to predict the number of blockages within any specified period using the Poisson probability distribution:
For example, suppose we wish to predict the chance of 1 blockage in a period of 7 days, the Poisson random variable would be 1. The average rate of success is the average number of blockages which in the past have occurred in 7 days (number of blockages/number of days in observation period x 7). To predict the chance of 2 blockages in 28 days, the Poisson random variable would be 2 and the average rate of success would be the average number of blockages in 28 days. As long as there are no blockages on nights following taking Nitrofurantoin, the average number of blockages for any period is 0: so until there is a blockage, the prediction of future blockages for any period is zero.
NITROFURANTOIN AND BLOCKAGES 17th JANUARY to 22nd AUGUST 2016
My first blockage occurred on the night of 16/17th January. 22nd August was the last day of he period when I took 50mg Nitrofurantoin every day.
Total number of days = 219
Days with Nitrofurantoin (estimate) = 52; no blockage
Days without Nitrofurantoin (estimate) = 167; 23 blockages
Using the same methods as above, p (the probability that there has been no association between taking Nitrofurantoin and the absence of catheter blockages) = (167/219)23 = 0.762623 = 0.0020, that is 20 chances in 10000 or 1 in 500.
DOSAGE OF NITROFURANTOIN
I am now trying to determine the minimum effective dose of Nitrofurantoin. Having taken 50mg every day from 24th July until 22nd August (30 days), this has been reduced to no more than 3 or4 times per week:
August 24, 25, 26, 28, 29, 30;
September 1, 2, 4, 7, 8, 10, 13, 16, 18, 19, 22, 25;
October 1, 5, 6, 7, 11, 14, 15, 17, 20 (100mg), 21, 22, 23, 25, 29, 31;
November 4, 5, 7, 10, 13, 16, 19, 22, 24, 26, 28;
December 1, 3, 5, 8, 11, 12, 17, 22, 31;
January
I have omitted it on days when I was not feverish, as might warn of a urinary infection, and when there was little or no sediment in my catheter, including days when I had a bladder wash-out. I also omitted Nitrofurantoin when my catheter had been replaced. On reflection, this was perhaps unwise. At least twice (18/10/16 and once before the blockages started) catheter replacement has been followed by a urinary infection.
Why not take Nitrofurantoin in the more usual way (4x50mg per day for 7 days) to treat proven urinary infections? For me, this is not effective for long; also, all my catheter blockages have occurred before an infection has been demonstrated. 50mg per day, reducing after 30 days has had no side-effects and has used less medication.
CONCERNS ABOUT TAKING NITROFURANTOIN LONG-TERM
The Users' Information Leaflets issued by Dr Reddy's Laboratories and Genfura do not mention preventing catheter blockages as a use of Nitrofurantoin. They do include 50mg or 100mg at bedtime for the prevention of further infections but do not say for how long. The leaflets list many possible side-effects but so far, I have not experienced any.
Will it cease to be effective after a while? So far it hasn't. It has already provided me with a very welcome relief from the misery of regular catheter blockages, possibly prevented internal damage and saved a significant amount of nurses' time.
Brumfitt and Hamilton-Miller support the use of Nitrofurantoin for long-term (12 months) prevention of urinary infections: see also and
CATHETERS
Has the catheter had any influence on the occurrence of blockages? I can refer only to the catheters I have had. There is a widely-held view that catheter production has lagged a long way behind the technology available and is failing patients badly.
The standard period between changes of catheter has been 12 weeks, but there have been some variations. It was changed shortly before 11pm on 23/7/16 by a night nurse attending a blockage and wasfollowed less than 4 hours later by a blockage of the new catheter,described by the nurse as 'positional'. The catheter that was replaced coincided with more blockages than any other I have had. I had no further blockage with the new catheter which was replaced on 18/10/16. In my case so far, there is no substantial evidence connecting blockages with particular catheters or with the period of time since installation ..... but absence of evidence is not evidence of absence.
SUPPORTING METHODS TO REDUCE CATHETER BLOCKAGES
Although Nitrofurantoin and catheter repositioning have eliminated blockages so far, often there is sediment in my catheter: so supporting methods are used to keep it clear:
SUPPORTING METHODS TO REDUCE THE CHANCES OF CATHETER BLOCKAGES
1 High water intake: widely recommended to wash out loose sediment and to dilute urine and bacterial concentration: possibly a necessary but not sufficient method to prevent blockages. It certainly did not cause the sudden cessation of blockages from 24/7/16.
2 Bladder wash-outs: I have never had a blockage on the night immediately following a wash-out but I have had at least one on the night after that: they reduce but do not eliminate blockages.
3 Loosening any sediment in the catheter by rolling it between the hands.
4 Adding vinegar to food seems to be followed by a clearer catheter (by lowering urine pH and acting as an antibiotic). Lemon juice has a similar effect.
It looks possible that the sediment was caused by reducing the amount of Nitrofurantoin below 50mg per day and that the supporting methods might be alternatives to higher doses. Nitrofurantoin does appear to clear sediment from the catheter not much longer than an hour after taking it - as would be expected from its property of preventing blockages.
BACTERIA CAUSING CATHETER BLOCKAGES
It seems likely that the bacteria killed by Nitrofurantoin created the sediment which resulted in most of the blockages. Samples of the contents of the catheter at the times of blockages would have been useful to test this. Quick urine tests using paper sticks to detect bacteria and test pH are worth trying to help decide whether or not Nitrofurantoin is needed to prevent an imminent blockage, although their reliability will be limited: we do not know what bacteria caused the blockages and so can not be sure that such tests would identify them.
However, Nitrofurantoin has been shown to be effective against: Citrobacter species, Coagulase negative staphylococci, E. coli, Enterococcus faecalis, Klebsiella species, Staphylococcus aureus, Staphylococcus saprophyticus, Streptococcus agalactiae
Many or all strains of the following genera are resistant to Nitrofurantoin: Enterobacter, Klebsiella, Proteus, Pseudomonas
Without knowing which bacteria caused the blockages, we can not be sure that Nitrofurantoin is the most selective antibiotic to deal with them. Also, we do not know at what pH the blockages occurred.
BLADDER STONES AND CATHETER BLOCKAGES
The methods explained in this paper will be effective only for blockages caused by certain types of bacteria or certain catheter positions. It remains to be seen to what proportion of catheter blockages these conditions apply. In July 2016, before taking Nitrofurantoin as part of this treatment, a rehabilitation consultant suggested to me that kidney stones might be the cause of my blockages. Bits breaking off the stones would block the catheter. In the absence of any samples from my catheter having been taken at the time of a blockage, this seemed a reasonable possibility, but now that the blockages have been demonstrated to be bacteriological (otherwise they would not have been stopped by Nitrofurantoin) it looks unlikely in my case - but not necessarily in others.
After reading an earlier version of this paper in November 2016, a urology consultant suggested to me that mine might be a case of bladder stones because these can cause re-infection. Repeated infections, might in some cases, be prevented by removal of bladder stones.
The following are commonly mentioned symptoms of bladder stones, not necessarily soon after their formation:
1 lower abdominal pain, 2 pain or discomfort when urinating, 3 difficulty when starting or a stop-start in urinating, 4 cloudy or dark-coloured urine, 5 discomfort or pain in the penis, 6 urinating more frequently, especially at night, 7 blood in the urine.
Spinal injury and consequent loss of sensation and use of a catheter might reduce awareness of some of these symptoms. Cloudy urine is commonly mentioned but not sediment which would be needed to cause a catheter blockage. Darkening of urine is also a usual consequence of taking Nitrofurantoin.
Anyone with persistent catheter blockages might be recommended by their medical practitioner to have a cystoscopy, an examination of the bladder with a fine telescope, to detect whether there are any stones. Stickler and Feneley suggest that Proteus mirabilis produced by bladder stones is a likely cause of catheter blockages
However, Nitrofurantoin is not effective against most strains of Proteus. See also
So Nitrofurantoin is unlikely to prevent blockages caused by bladder stones.
ATITUDES TOWARDS CATHETER BLOCKAGES
The nurses, particularly the night nurses, have left me with the impression that catheter blockages are much more common than they need to be. Often, they left me with a cheery 'See you again soon'. The prevailing attitude in both the medical and nursing professions that they are an inevitable consequence of having a catheter should be questioned.
In November 2016 I 'phoned the night nurses to thank them for coming to unblock my catheter on 23 nights between January and July, to explain why I have not called them out since July, and to offer to send them a copy of this paper: 'We don't give out e-mail addresses over the phone'.
Meanwhile, patients wake in the early hours of the morning, sweating profusely, trembling with massive shocks of spasms, resulting in urine being forced back to the kidneys and in extreme cases, autonomic dysreflexia, internal damage and death. Night nurses rush between patients to unblock catheters which do not need to be blocked. Sometimes they have taken over 2 hours to reach me (although the average is about 1 hour 20 minutes), explaining that they have had a lot of patients with blocked catheters that night.
Recently, a nurse from the local health authority called to assess my condition. A friend who was with me mentioned my catheter blockages and offered her this paper: no thanks. 'It's something they can live with'.