Carol J Bennet, Mary N Young, Salman S Razi, Rodney Adkins, Frances Diaz and Annie McCleary.

Purpose: We attempted to determine whether an introducer tip catheter reduces urinary tract infection in spinal cord injured patients on intermittent catheterisation.

Materials and Methods: The introducer tip catheter bypasses the colonised 1.5 cm of the distal urethra. Enrolled patients were prospectively entered into the study in alternate groups depending on whether they reflex voided 1 - on intermittent catheterisation with the introducer tip catheter but not voiding spontaneously or wearing an external urinary catheter, 2 - same as group 1 but using a nonintroducer tip catheter, 3 - on intermittent catheterisation with the introducer tip catheter, voiding by reflex and wearing an external urinary catheter, and 4 - same as group 3 but using a nonintroducer tip catheter.

Results: Statistical significance was shown when comparing patients using versus not using the introducer tip catheter regardless of whether an external urinary catheter was worn (p= .0121). A greater difference was noted between patients using and not using the introducer tip catheter in the intermittent catheterisation only group

(p= 0.0098).

Conclusion: The introducer tip catheter decreased urinary tract infections in hospitalised men with spinal cord injury on intermittent catheterisation.

In the last several decades intermittent catheterisation has become the urological management option of choice for patients with spinal cord injury^1-3. Although intermittent catheterisation has decreased the incidence and severity of urinary tract infection in hospitalised patients, hospital acquired gram-negative organisms in the urine, many of which are resistant to antibiotics, have become a major concern. Such infections result in increased morbidity, loss of patient therapy time, increased hospital stay and increased cost of rehabilitation. Numerous articles associate colonisation of the distal urethra in spinal cord injured patients with increased incidence of urinary tract infections in men with spinal cord injury. Montgomerie^4-5 and Gilmore^6-7 et al performed multiple studies on the colonisation of Pseudomonas and Klebriella in the perineum and urethra in spinal cord injured men, and they demonstrated considerably more colonisation when patients were wearing external catheters. Hirsh et al believed that colonisation beneath the external catheter and extension into the distal urethra placed patients at greater risk for urinary tract infection when they were concurrently on an external catheter and intermittent catheterisation⁸. We examined the urinary tract infection rate in hospitalised patients on intermittent catheterisation using a sterile introducer tip catheter system that bypasses the colonised portion of the urethra, and compared results to those of patients on intermittent catheterisation but not using an introducer tip catheter system.

The MMG/O’Neil catheter system was originally developed in Australia for obstetrics patients.⁹ The system consists of a plastic catheter enclosed in a prelubricated plastic sleeve and urethral introducer tip that protects the catheter from contamination by the colonised first 1.5cm of urethra (see figure). All patients underwent catheterisation using the MMG/O’Neil system or that system with the introducer tip removed, as packaged and sterilised by the manufacturer. Both catheter kits contained povidone-iodine swabs for skin preparation. Approval was obtained from the Food and Drug Administration to remove the introducer tip selectively from the catheter system.

The study included 11 tetraplegic and 16 paraplegic patients 17 to 38 years old (mean age plus or minus standard deviation 26 ± 7.5). Inclusion criteria were normal excretory urography or renal ultrasound within 6 months of injury, on intermittent catheterisation, off antibiotics for 24 hours and negative urinalysis. Patients were prospectively entered into the study in alternate groups depending on whether they reflex voided: 1-on intermittent catheterisation with the introducer tip catheter but not voiding spontaneously or wearing an external urinary catheter; 2-same as group 1 but using a nonintroducer tip catheter, 3-on intermittent catheterisation with the introducer tip catheter, voiding by reflex and wearing an external urinary catheter, and 4-same as group 3 using a nonintroducer tip catheter. Informed consent was obtained from all patients.

A total of 19 spinal cord injured patients accounted for 27 data points, of whom 8 were entered in the introducer and nonintroducer tip groups, including 3 in the voiding groups. Patients were treated on a spinal injury unit consisting of 8 rooms. All groups were similar in regard to age, levels of injury and caregiver versus self-catheterisation. Urodynamics were done to determine if high intravesical pressures had an influence on any group more than another (table 1). Every attempt was made to control intravesical pressures below 40cm water with anticholinergic therapy. In 1 patient bladder pressures remained elevated above 100cm water despite pharmacological therapy. However, he was entered in the introducer and nonintroducer tip groups. After a urinary tract infection was identified the patient was removed from study, treated with antibiotics for 10 days according to sensitivity and then reassigned as a new subject to a different group. The infection rate was determined by the catheterisation-to-urinary tract infection ratio. Bacteria was defined as greater than 10⁶ colony forming units per ml. Urine cultures and urinalysis were obtained by sterile catheterisation weekly or when patients were symptomatic. All cultures and urinalysis were obtained during the same catheterisation for comparison. The criteria for determining a symptomatic urinary tract infection were established by the consensus validation conference sponsored by the National Institute on Disability and Rehabilitation Research.¹⁰ Symptomatic urinary tract infection included fever, increased spasms, automatic dysrefexia, cloudy urine and positive leukocytes or leukocyte esterase.

Because the number of subjects was small and variance within the groups differed, catheterisation data were analysed using the nonparametric Kruskal-Wallis 1-way analysis of variance. Groups were then combined in different configurations and the Kruskal-Wallis test was repeated for each group combination.¹² The association of intravesical pressure and urinary tract infection was assessed using correlation analysis. General descriptive statistics, measurements of central tendency, frequency distributions and cross tabulations were done to describe the study population with statistical significance at p<0.05.

Table 1 shows that the various risk factors were similar among comparable groups. Table 2 shows infection rate results for patients catheterised with introducer and nonintroducer tip catheters in the different groups. There was no significant difference in the number of patients catheterised every 4 or 6 hours among comparable groups. Patients who reflex voided underwent catheterisation every 8 hours. The mean number of catheterisations before infection in each group is also shown in table 2.

There was an overall significant difference among the 4 groups (p=0.0806) with a stronger effect when comparing patients using (groups 1 and 3 combined) versus not using the introducer tip catheter (groups 2 and 4 combined), regardless of whether an external urinary catheter was worn (p=0.0131). The most pronounced difference was between patients using the introducer tip catheter versus those not in the intermittent catheterisation only group (group 1 versus group 2, p=0.0093). No significant difference was found when comparing men wearing versus not wearing an external urinary catheter regardless of whether the introducer tip catheter was used (groups 1 and 2 combined versus groups 3 and 4 combined). There was no significant difference between the voiding only groups.

Organisms colonising the bladder were Klabriella and Enteroicoccus in all groups. The nonintroducer tip groups had Staphylococcus colonisation, which was not present in the introducer tip groups. In addition, the nonintroducer tip/external urinary catheter group was colonised with Pseudomonas and Citrobacter. Only 4 cultures had less than 10⁶ colony-forming units per ml. Those 4 cultures yielded 3 organisms each that combined to more than 10⁶ colony-forming units per ml, and were considered to represent infections. all positive cultures correlated with positive urinalysis for Leukocytes and leukocyte esterase. However, positive urinalysis did not correlate with positive cultures in more than 40% of the cases.

Discussion

Two previous studies showed a significant decrease in infection rates in hospitalised spinal cord injured patients using the MMG/O’Neil system catheter system. Charbonneau-Smith reported that 77.8% of controls using a sterile system with a straight catheter had more than 1 infection per hospitalisation compared to only 44.4% of the group using the MMG/O’Neil system.¹² We previously noted a 30% decrease in infection in 3 years using the MMG/O’Neil system.¹³ These previous studies compared the MMG/O’Neil system to other sterile catheter tray systems. We compared the MMG/O’Neil system with and without the introducer tip, while examining other known factors that place spinal cord injured patients at increased risk for a urinary tract infection.

As recently as 1993, the validation conference sponsored by the National Institute on Disability and Rehabilitation Research listed the risk factors for urinary tract infection in the spinal cord injured population as an over distended bladder, vesicoureteral reflux, high pressure voiding, large post-void residuals, stones in the urinary tract and outlet obstruction.¹⁰ The conclusion was that, although the risk of infection is decreased with intermittent catheterisation, risk of urinary tract infection still exists. Other studies established additional factors that place spinal injured patients on intermittent catheterisation at greater risk for urinary tract infection, including wearing a external catheter and caregiver intermittent catheterisation.^14,16

Increased intravesical pressure and detrusor-sphincter dyssynergia are variables that greatly impact the urinary tract infection rate of spinal cord injured patients on intermittent catheterisation. Lapides reported that increased intravesical pressure and detrusor over distension can cause a loss of tissue immunity and impaired bladder circulation associated with an increased incidence of symptomatic urine infection.¹⁶ ______ established mean detrusor pressure in the voiding groups as 68cm water, while the nonvoiding groups had a mean bladder pressure of 82cm water. Since variability in the number of catheterisations before infection in the groups with lower pressures was high (standard deviation ± 68) and the number of cases was small in the high pressure groups, the influence of intravesical pressures on the urinary tract infection rate was not adequately assessed.

The number of patients in the voiding and high pressure groups was controlled by study parameters that ensured that all high pressure bladders were treated with anticholinergics. Thus, the number of patients in the voiding groups was restricted to those in whom intravesical pressure was not decreased by pharmacological agents. Although the urinary tract infection rate was considerably higher in the groups with high intravesical pressures (mean 34 versus 88 catheterisations per infection), due to small numbers a statistically significant difference was not established. In comparable nonvoiding groups the difference between the introducer and nonintroducer tips was clearly robust (p<0.093), as was the overall difference between all introducer tip catheter groups compared to all nonintroducer tip catheter groups (p<0.01).

Interestingly, in support of previous reports on risk factors for urinary tract infection in the spinal cord injured population, the patient with the highest infection rate (26 and 28 catheterisations per infection with the introducer and nonintroducer tip catheters, respectively) had intravesical pressures greater than 100cm water despite pharmacological intervention with anticholinergic therapy. He also had detrusor-sphincter dyssynergia, voided by reflex, wore an external urinary catheter and required caregiver intermittent catheterisation. In contrast, the patient with the lowest infection rate (256 catheterisations per urinary tract infection with the introducer tip catheter) had intravesical pressures less than 40cm water. He was continent between catheterisations, did not wear an external urinary catheter and performed self-catheterisation.

The MMG/O’Neil system catheter system with an introducer tip that bypasses the colonised distal urethra significantly decreased the urinary tract infection rate in hospitalised spinal cord injured men on intermittent catheterisation. All risks of increased urinary tract infections should be considered in urological bladder management of spinal cord injured patients.