Biomimetic urine flow control can preserve bladder function in patients with indwelling catheterization

Abstract

For patients with long-term indwelling catheterization, bladder function will be affected. It is necessary to explore whether biomimetic urine flow control (BUFC) can improve bladder function in patients undergoing indwelling catheterization. A retrospective, data-only, cohort study was carried out. The patients admitted to the intensive care unit, who had retained catheter and been continuously using a urodynamic monitoring system for over 30 days were selected. They were divided into 2 groups based on whether they were using BUFC function. The urodynamic monitoring data of the 2 groups were compared and analyzed. A total of 30 patients were included in the final analysis, including 15 in the BUFC group and 15 in the unobstructed group. The Urinary Volume and maximal urinary flow rate of the unobstructed group showed a continuous downward trend, while the BUFC group remained stable, and there was a statistical difference (P < .05) between the 2 groups since day 20. The bladder ultrasound imaging showed that the bladder volume of the BUFC group did not decrease significantly on the 30th day. BUFC technology, which provided by a urodynamic monitoring system, has potential protective effects of the bladder function after indwelling catheterization.

1. Introduction

Patients admitted to intensive care unit (ICU) are usually in coma, shock or sedation and analgesia treatment, so they retained catheter for urination and urine volume monitoring.^[1] As a nursing routine,^[2] urinary volume recording can truly reflect the dynamic balance of human body fluids and cardiac or renal functions. Accurate urine volume monitoring helps to determine changes in the condition and guide the development of treatment plans.^[3,4] All along, the time when patients take out the catheter has been determined by doctors based on experience. If the catheter is removed too early, the patient bladder function has not been restored and they are still unable to urinate autonomously, which will lead to a second intubation and increase the patient risk of pain and infection. And if the catheter is removed too late, the catheter will stay in the patient body for too long, which greatly increases the probability of urinary tract infection^[5,6] and reducing quality of life.^[7] Therefore, the right time to remove the catheter is very important. Before deciding whether to take out the catheter, the doctor needs to refer to whether the function of the bladder detrusor is normal.^[8] The bladder pressure at the urination point,^[9] one-time urination volume, and maximum indwelling catheterization urine flow rate can directly reflect the functional status of the bladder detrusor muscle, especially the maximum indwelling catheterization urine flow rate.^[10] The higher the urine flow rate of indwelling catheterization, the better the contractile function of the bladder detrusor muscle.^[11]

For patients with long-term indwelling catheterization, bladder function training should be performed before removing the catheter. The relationship between indwelling catheterization time and lower urinary tract dysfunction is unclear. There are 2 main types of lower urinary tract dysfunction depending on the functional phase of the lower urinary tract affected (filling or voiding phase). Due to possible bladder contracture, the effective capacity of the bladder decreases. Early literature suggested that, the tidal urine drainage method of regularly clamping and opening the catheter was used to train bladder function,^[12] but it has the drawbacks of being cumbersome, overflowing urine, and infection. In addition, relying solely on experience to apply tidal drainage has the uncertainty of bladder filling and the inaccuracy of operator execution time, which also makes it difficult for tidal urine drainage to achieve the ideal bladder function training effect. Can automatic, accurate, and dynamic urine volume recording be achieved during the process of indwelling catheterization? Can biomimetic urine flow control (BUFC) be performed during indwelling catheterization based on the physiological characteristics of the bladder? Can bladder function be preserved after indwelling catheterization without bladder function training? We conducted a retrospective study hoping to provide some inspiration for the answers to these questions.

2. Material and methods

2.1. Study design

A retrospective, data-only, clinical control study was carried out at a tertiary comprehensive, teaching hospital (Tongde Hospital of Zhejiang Province) in Zhejiang, China. Tongde Hospital of Zhejiang Province Institutional Review Boards approved the study and granted waiver of patient informed consent considering this is not an intervention study. The patients admitted to the ICU of Tongde Hospital of Zhejiang Province from August 2022 to April 2023, who had retained catheter and been continuously using a urodynamic monitoring system for over 30 days were selected. They were divided into 2 groups match 1:1 based on whether they were using BUFC function. The urodynamic monitoring data of the 2 groups for day 1, day 5, day 10, day 15, day 20, day 25, and day 30 were selected to compare and analyze, for indicating the protective effect of BUFC technology on bladder compliance.

2.2. BUFC technology

BUFC technology is a function provided by a urodynamic monitoring system (Zhejiang Lexin Medical Technology Co., Ltd, China). The urodynamic monitoring system consists of a host, display screen, pressure sensor, weighing sensor, control pipeline valve, etc. The host mimics the brain, receiving bladder pressure and controlling the opening/closing of pipeline valves. The pressure sensor mimics the bladder stretch receptor to sense the bladder pressure. The pipeline valve mimics the urethral sphincter to control the opening/closing of the urinary tract. Under BUFC mode, when the system detects that the pressure inside the bladder has reached the set pressure threshold (15 cm H₂O) or the urination interval time (2 hours) has reached the set value, the system automatically opens the valve for urination. After urinating for a period of time (duration of urination), the valve automatically closes and begins to store urine. Under unobstructed mode, only 1 cycle (2 hours urination interval time or 15 cm H₂O bladder pressure) is activated every 24 hours to monitor the maximum urine flow rate (MUFR) and the urine storage process is not carried out in other time. Its working principle is shown in Figure 1.

Figure 1.

Schematic diagram of biomimetic principle.

2.3. Study population

The inclusion criteria were as follows: Age > 18. Patients admitted to ICU need to retain catheter for treatment. The retention period shall not be <30 days. A urodynamic monitoring system was used for urodynamic monitoring.

The exclusion criteria were as follows: Organic diseases of the bladder; The patient condition continues to worsen; Urine volume < 400 mL/d; Urodynamic monitoring data is incomplete. Due to concerns about the possibility of infection caused by urinary storage,^[13] some patients adopt an unobstructed mode, while others adopt a biomimetic urinary control mode. They can be divided into 2 groups: BUFC group and unobstructed group.

2.4. Outcome

Two main indicators of bladder function were selected: average voiding volume^[14] and MUFR.^[15,16] Urinary flow rate is defined as the amount of fluid discharged through the urethra per unit time, and is calculated as a function of time to determine the rate of urination, expressed in mL/s. During the examination, doctors drain urine into a collection container connected to an electronic measuring device based on the patient daily urination habits and posture. MUFR refers to the maximum measured value of urine flow rate after artificial correction of pseudo images. The urodynamic monitoring system recorded these 2 indicators in real-time. The data of day 1, day 5, day 10, day 15, day 20, day 25, and day 30 were selected to analyze.

2.5. Statistical method

Continuous variables are presented as means with standard deviations. Categorical variables are presented as number with percent. P values were generated using t-tests or Chi squared tests where appropriate. We generated a diagram to visualize the changes in patients’ status (average voiding volume and MUFR) over time using GraphPad V9. All analyses were conducted using Stata/SE V17 and 2-sided 0.05 as the threshold for significance.

3. Results

3.1. The general characteristics of the patients

A total of 30 patients were included in the final analysis, including 15 in the BUFC group and 15 in the unobstructed group. The general characteristics of the patients was shown as Table 1. There was no statistically significant difference in gender, age, and main diagnosis between the 2 groups (P > .05).

Table 1.

General characteristics of the patient.

Characteristic	BUFC (n = 15)	Unobstructed (n = 15)	P
Gender: male	8 (53.3%)	9 (60.0%)	.713
Female	7 (46.7%)	6 (40.0%)	.713
Age (yr, mean ± SD)	78.2 ± 10.8	75.1 ± 13.1	.490
Main diagnosis: septic shock	1 (6.7%)	2 (13.3%)	.543
Cerebral hemorrhage	3 (20.0%)	3 (20.0%)	1.000
Cerebral infarction	3 (20.0%)	1 (6.7%)	.283
Pulmonary infection	2 (13.3%)	2 (13.3%)	1.000
Other	6 (40.0%)	7 (46.7%)	.713
Catheter infection within 30 dy	1 (6.7%)	1 (6.7%)	1.000

BUFC = Biomimetic urine flow control.

3.2. The average voiding volume and MUFR

The average voiding volume and MUFR of the unobstructed group showed a continuous downward trend, while the BUFC group remained stable, and there was a statistical difference (P < .05) between the 2 groups since day 20. There was no statistically significant difference in average voiding volume and MUFR of BUFC group compared with day 1 (P > .05). The average voiding volume and MUFR of unobstructed group was lower in day 20, day 25, and day 30 compared with day 1 (P < .05). Detailed results can be found in Table 2 and Figure 2.

Table 2.

The trend of average voiding volume and maximal urinary flow rate (MUFR).

Visits	Average voiding volume (mL)			MUFR (mL/s)
	BUFC (n = 15)	Unobstructed (n = 15)	P	BUFC (n = 15)	Unobstructed(n = 15)	P
Dy 1	89.4 ± 38.8	103.3 ± 23.8	.246	3.39 ± 1.28	3.71 ± 1.05	.469
Dy 5	98.3 ± 29.9	95.5 ± 22.7	.775	3.28 ± 1.07	3.26 ± 0.91	.956
Dy 10	101.9 ± 28.6	91.0 ± 9.4	.171	3.47 ± 1.23	3.19 ± 0.55	.430
Dy 15	93.4 ± 24.0	82.3 ± 12.9	.127	3.31 ± 0.83	2.95 ± 0.53	.160
Dy 20	94.9 ± 21.3	76.5 ± 10.9*	.006	3.37 ± 0.87	2.67 ± 0.52*	.011
Dy 25	88.9 ± 21.3	58.3 ± 14.1*	<0.001	3.15 ± 0.87	2.05 ± 0.43*	<.001
Dy 30	84.4 ± 22.0	47.2 ± 18.6*	<0.001	3.13 ± 1.15	1.71 ± 0.64*	<.001

BUFC = biomimetic urine flow control.

^*Compared with dy 1, P < .05.

Figure 2.

Trends in average voiding volume and MUFR. MUFR = maximal urinary flow rate.

3.3. The bladder ultrasound imaging

The bladder ultrasound imaging showed that the bladder volume of the biomimetic control group did not decrease significantly on the 30th day, but the bladder volume of the unobstructed group decreased significantly. The ultrasound image of the bladder was shown as Figure 3.

Figure 3.

Typical images of bladder ultrasound in 2 groups (30 dy after indwelling catheter).

4. Discussion

Bladder pressure measurement through a Foley catheter is the current standard in monitoring for intra-abdominal hypertension and abdominal compartment syndrome (ACS).^[17] Routine intensive care combined with bladder pressure monitoring can be used as a routine monitoring content in the comprehensive intensive care treatment unit. It can timely detect intra-abdominal hypertension, take intervention measures, prevent the occurrence of ACS^[18] and multiple organ dysfunction, and reduce the mortality rate of ACS patients. The correlation between bladder measurement of intra-abdominal pressure (IAP) and direct measurement of IAP is high, and the bladder pressure measurement technology is simple, safe, and feasible, which is considered the “gold standard” for IAP measurement, so the bladder pressure can be continuously and dynamically monitored during indwelling catheterization with the urodynamic monitoring system, indirectly reflecting changes in abdominal pressure. The commonly used method for measuring IAP is indirect measurement through the bladder, so the urodynamic monitoring system can simultaneously monitor IAP.

Urine catheters are often reservoirs of multidrug-resistant bacteria and sources of pathogens transmission to other patients.^[19] The urinary tract is the commonest source of nosocomial infection, particularly when the bladder is catheterized.^[13] Urinary tract infections related to catheters often occur in the medical system.^[20] Indwelling catheters are strongly associated with the development of bacteriuria, which can lead to significant morbidity in hospitalized patients.^[21] Catheter-associated urinary tract infection remains one of the most prevalent, preventable, health care-associated infections.^[22] We aimed to reduce inappropriate use of catheters to reduce health care-associated infections.^[23] Further organisms tend to be acquired by patients catheterized for more than 30 days.^[13]The use of biomimetic urinary control technology has not yet been discussed in relation to urinary tract infection.^[24]

The urodynamic monitoring system achieved automatic, accurate, and dynamic urine volume recording during the process of indwelling catheterization. BUFC can be performed during indwelling catheterization based on the physiological characteristics of the bladder by the urodynamic monitoring system. By comparing the ultrasound in day 30 and urine volume under the same conditions, we can roughly evaluate the condition of bladder contracture. We can definitely believe that bladder function can be preserved after indwelling catheterization with BUFC technology. It is worth pointing out that our study has several limitations that must be acknowledged. Firstly, our study was retrospective. We do not have the opportunity to adopt indicators that better represent bladder function, such as bladder outlet obstruction index and bladder contractility index. Secondly, this was a single-center study with a limited sample size. This study conducted a preliminary exploratory analysis on the use of BUFC technology, and higher levels of evidence-based medical evidence are needed to verify in the future.

5. Conclusions

BUFC technology, which provided by a urodynamic monitoring system, has potential protective effects of the bladder function after indwelling catheterization. Further design of large sample, multicenter randomized controlled trials can be carried out to clarify the value of promotion and use in ICUs.

Acknowledgments

Thanks to all the participants and clinical researchers. Thanks to all the peer reviewers who contributed to the continuous improvement of this article.

Author contributions

Conceptualization: Minrong Xu, Mahong Hu, Xiujuan Xu.

Data curation: Wei Zhang, Lingxiang Sheng.

Formal analysis: Lingxiang Sheng.

Funding acquisition: Xiujuan Xu.

Investigation: Minrong Xu, Wei Zhang.

Methodology: Minrong Xu, Mahong Hu.

Project administration: Xiujuan Xu.

Resources: Minrong Xu, Lingxiang Sheng.

Software: Minrong Xu.

Supervision: Minrong Xu.

Visualization: Minrong Xu.

Writing – original draft: Minrong Xu.

Writing – review & editing: Xiujuan Xu.