The MBC group consisted of 936 surgical patients. The average MBC was 611 mL (SD ± 209 mL, range 150 to 1400 mL). The incidence of urinary catheterization was 9.1% (85/936) (Table 2).
Table 2
Demographic and Clinical Characteristics of Patients in the MBC group
MBC group | N = 936 |
Patient data | |
Women, No. (%) | 493 (53) |
Age, mean (SD), y | 47.9 (15) |
Height, mean (SD), cm | 176 (10) |
Weight, mean (SD), kg | 81.4 (17) |
BMI, mean (SD), kg/m2 | 26.3 (5) |
Type of Surgery, No. (%) | |
Head/Neck | 209 (22) |
Thoracic/Breast | 77 (8) |
Spine | 33 (4) |
Abdominal | 273 (29) |
Extremities | 344 (37) |
Study Data | |
MBC, mean (SD), ml | 611 (209) |
Residual volume, mean (SD), ml | 33 (53) |
Voided before surgery, No. (%) | 877 (94) |
Time before surgery, mean (SD), min | 59 (48) |
Volume at Holding, mean (SD), ml | 52 (81) |
General Anesthesia, No. (%) | 639 (68) |
Spinal Anesthesia, No. (%) Articaine, No. (%) Bupivacaine, No. (%) | 297 (32) 235 (79) 62 (21) |
Total volume infused, mean (SD), ml | 1,492 (647) |
Procedure time, mean (SD), minutes | 61 (40) |
BMI – Body Mass Index, MBC – Maximum Bladder Capacity, SD – Standard Deviation |
UNIVARIATE RISK FACTORS FOR URINARY CATHETERIZATION5
Modifiable risk factors
Figure A displays all identified (un) modifiable risk factors potentially associated with urinary catheterization (p < 0.10). The strongest modifiable risk factor for urinary catheterization was spinal anesthesia. Coupled to spinal anesthesia, and therefore not displayed in Fig. 1A-C, was the regression of the sensory block. If the sensory block was higher than dermatome T12, voiding was difficult and 69% of these patients had to be catheterized (RR 12.8, 95%CI 8.4 to 18.3; p < 0.0001). When the sensory block had regressed below dermatome S3, the incidence was 5.7% (RR 0.8, 95%CI 0.4 to 1.6; p = 0.49). Another modifiable risk factor was a preoperative bladder volume of 150 mL or more (RR≥ 150mL 2.4, 95%CI 1.6 to 3.5; p < 0.02). The total volume infused over 1 liter was not a significant risk factor for urinary catheterization (RR 0.7, 95%CI 0.4 to 1.1, p = 0.09). Also, not significant were the perioperative used drugs piritramide (i.v. or s.c.) (RR 1.0, 95%CI 0.7 to 1.6; p = 0.91); ephedrine (RR 1.3, 95%CI 0.8 to 2.0, P = 0.33) and atropine (RR 1.2, 95%CI 0.7–1.9, p = 0.5). For phenylephrine the numbers were too small to analyse.
Unmodifiable risk factors
A smaller MBC increased the incidence of urinary catheterization. Of the 300 patients with an MBC < 500 mL 14% were catheterized. Compared to 9% of the 398 patients with an MBC between 500 mL and 800 mL and 2% of the 199 patients with an MBC ≥ 800 mL (MBC< 500mL RR 7.0, 95%CI 2.5 to 19.1; p < 0.001). Older age (≥ 60) was a risk factor for urinary catheterization (RR 3.3, 95%CI 2.2 to 4.9; p < 0.0001). Also, a higher IPSS was a risk factor in the univariate analysis. In patients with ‘severe’ symptoms (IPSS 20–35) the incidence of urinary catheterization was 22% (RR 2.7, 95%CI 1.5 to 5.2, p = 0.002).
The strongest unmodifiable risk factor ‘related to surgery’ was the duration of surgery (RR30 − 60 4.5, 95%CI 1.8 to 11.3, RR> 60 5.1, 95%CI 2.1 to 12.8; p < 0.001). For the location of surgery, comparing head/neck/thoracic (general anesthesia), with surgery on the abdomen or extremity (general or spinal anesthesia) the incidence increased from 4.9–11.8% and 10.2% respectively (RRabdomen 2.4, 95%CI 1.3 to 4.4; p < 0.004 and RR lower extremity 2.1, 95%CI 1.1 to 3.7; p = 0.012). Another unmodifiable risk factor was the first scan ≥ 250 mL at the PACU (incidence 18.6% compared to 6.3% <250 mL (RR 3.0, 95%CI 1.9 to 4.4; p < 0.001).
Having no urge to void at the moment the MBC was reached turned out to be an unmodifiable risk factor. Of the 84 patients who were catheterised 60 patients had no urge to void (71%) (RR 4.8, 95%CI 3.1 to 5.9; p < 0.001). Gender (RR 0.8, 95%CI 0.5 to 1.2, p = 0.31) and preoperative known hypertension (RR 1.6, 95%CI 1.0 to 2.5, p = 0.07) did not reach statistical significance throughout all analysis. Anti-depressant drugs were used by 58 patients (6%) of which 18% was catheterized (RR 2.8; p < 0.001) and 61 patients used diazepam (6.5%) of which 23% was catheterized (RR 1.8; p = 0.02). For diabetes the number were too small to analyse (26 patients = 3.1%).
FULL MULTIVARIABLE ANALYSIS
In Figure B is displayed a full multivariable analysis for urinary catheterization in the MBC group including all potential risk factors with a level of p < 0.10 from univariate analysis. Using the backward elimination strategy, location of surgery and ‘severe’ IPSS were not identified as independent risk factors in the multivariable analysis.
FINAL MULTIVARIABLE ANALYSIS
In Figure C is displayed the final multivariable model. Spinal anesthesia was the main modifiable risk factor with a RR for hyperbaric bupivacaine of 8.1 and for articaine the RR was 3.1. The unmodifiable risk factors MBC (RR 6.7), duration of surgery (RR 5.5), first scan at PACU ≥ 250 mL (RR 2.1) and age ≥ 60 (RR 2.0) were identified as independent risk factors.
TIME OF VOIDING or CATHETERIZATION and SPEED of BLADDER FILLING
In Table 3 is calculated the time from the start of anesthesia till patients were able to void or were catheterized. The speed of bladder filling was estimated during this time period. This was done by subtracting the preoperative scanned bladder volume from the last scanned bladder volume before spontaneous voiding or catheterization. In both general and spinal anesthesia spontaneous voiding occurred after 280 min (4.5hrs). The scanned bladder volume was around 450 mL and the speed of bladder filling of 100 mL/u. Catheterization after general anesthesia happened significant later than after spinal anesthesia (352 ± 157 min versus 205 ± 74 min, p < 0.001). Spinal anesthesia patients who were catheterized (203 ± 94 mL/hour, p = 0.005) had a twice as high urine production than patients who voided spontaneously (107 ± 63 mL/hour).
Table 3
Time to catheterization/voiding after general or spinal anesthesia
| N | MEAN | STANDARD DEVIATION | MINIMUM | MAXIMUM |
GENERAL ANESTHESIA | | | | | |
Spontaneous | | | | | |
Time (minutes) | 580 | 282# | ± 117 | 70 | 808 |
Scan volume (mL) | 595 | 412 | ± 206 | 0 | 1000 |
Rate (mL/hour) | 569 | 100 | ±66 | 0 | 388 |
Catheter | | | | | |
Time (minutes) | 26 | 352#* | ± 157 | 178 | 710 |
Scan volume (mL) | 31 | 602 | ± 216 | 298 | 1000 |
Rate (mL/hour) | 25 | 137 | ±84 | 32 | 317 |
SPINAL ANESTHESIA | | | | | |
Spontaneous | | | | | |
Time (minutes) | 238 | 273^ | ±82 | 99 | 712 |
Scan volume (mL) | 238 | 452 | ± 224 | 49 | 999 |
Rate (mL/hour) | 234 | 107& | ±63 | 11 | 379 |
Catheter | | | | | |
Time (minutes) | 44 | 205^* | ±74 | 99 | 397 |
Scan volume (mL) | 52 | 626 | ±179 | 330 | 999 |
Rate (mL/hour) | 43 | 203& | ±94 | 94 | 469 |
with their bladder filling rates.
N, with missing data
Time = time to catheterization or voiding
Scan volume = scanned bladder volume before voiding or catheterization
Rate = speed of bladder filling from start of anesthesia till voiding or catheterization
# General anesthesia spontaneous (282 min) versus catheter (352 min), p = 0.032
^ Spinal anesthesia spontaneous (273 min) versus catheter (205 min), p < 0.001
* Spinal anesthesia (205 min) versus general anesthesia (352 min) with catheter, p < 0.001
& Spinal anesthesia rate of bladder filling catheter (203 mL/hour) versus spontaneous (107 mL/hour), p = 0.005