-THE JOURNAL OF UROLOGY
Vol. 117, February
Copyright © 1977 by The Williams & Wilkins Co.
Printed in U.S.A.
EVALUATION OF A VENTED DRAINAGE SYSTEM IN PREVENTION OF BACTERIURIA THOMAS P. MONSON,* FIDEL V. MACALALAD, J. WAYNE HAMMAN
AND
CALVIN M. KUNIN
From the Department of Medicine, University of Wisconsin and the Veterans Administration Hospital, Madison, Wisconsin, and the Abbott Laboratories and the Department of Surgery, Northwestern University Medical School, Chicago, Illinois
ABSTRACT
A vented urinary drainage system was compared to an otherwise identical non-vented system in a prospective, randomized, double-blind study. Among the 316 female patients evaluated there was a significant reduction in the rate of bacteriuria after 10 days using the vented system (66 per cent in the non-vented group versus 26 per cent in the vented group, p less than 0.05), while no significant difference could be demonstrated among the 190 male patients. We used urine hemoglobin as an indicator of mucosal trauma that might predispose to bacteriuria and no significant difference could be shown between the 2 drainage systems. and insertion of the catheter an initial urine specimen was collected; drainage bag identification and location were accomplished by means of the patient charge slip sent to Central Supply. A daily report of all drainage bags was compiled by the study nurse. Drainage bags were supplied by Abbott Laboratories in sterile packages identified only with a study code number. The code was not broken until the study was completed. Descriptions of drainage systems. The drainage system consists of a drain line with 122 cm. (48 inches) of tubing, 0.7 cm. (9/32 inches) in diameter, that enters the top of the 2,500 ml. drainage bag (fig. 1). In this top vented system filtered air is admitted into the drainage line through a circumferential vent built into the catheter connector. The vent consists of a 0.45 mµ. non-wet bacterial-retentive filter. For the control non-vented system used in our study the bacterial-retentive filter was occluded with plastic to prevent air entry in a manner such that the 2 systems could not be distinguished. Units were numbered in a randomized fashion for blind assignment to patients. Monitoring of the system. All urethral catheters were monitored daily by a study nurse by aspiration of a small quantity of urine from the proximal end using a sterile disposable syringe. The area to be punctured was prepared by sponging with a 70 per cent alcohol solution. Urine specimens obtained in this manner were brought to the laboratory within 1 to 2 hours. A dilution pour plate was prepared using trypticase soy agar. Plates were allowed to harden and were read after 24 to 48 hours. Colony counts were reported by number, with 10,000 colonies per milliliter or greater in 2 consecutive specimens considered the significant level of bacteriuria for the purpose of this study. Hemoglobin analysis. Urine for hemoglobin assay was taken simultaneously with specimens for culture and frozen at minus MATERIALS AND METHODS 35C until assayed. Analysis of urine hemoglobin was done Study procedure. This study was performed in a 500-bed according to the technique of McCall 1 5 using a Turner 350 community hospital to compare a top vented with a control spectrophotometer. non-vented system. Nurses, attendants and orderlies were Analysis of data. All patients with an initially positive urine instructed in the care of the drainage bag. They were particu- culture and those whose catheter or drainage bag was removed larly urged not to break the connection between the catheter or changed within 24 hours after insertion were deleted from and drainage tube. Irrigation of the catheters was discouraged, the study. Charts were reviewed as patients were discharged except for procedures necessary for the care of postoperative from the hospital, died or when catheters were removed. urologic patients and when obstruction of the catheter was Pertinent clinical characteristics, including concomitant use of suspected. After random assignment of the drainage system systemic antimicrobial agents, were recorded. The cumulative risk of developing bacteriuria was calculated by the life table Accepted for publication May 14, 1976. * Current address: Department of Medicine, Veterans Administra- method, which provides the expected rates of bacteriuria, tion Hospital, 300 E. Roosevelt Rd., Little Rock, Arkansas 72206. making adjustments for the loss of patients from the study
The indwelling urethral catheter is one of the most frequently used and valuable forms of urinary diversion. However, it carries the risk of acquisition of bacteriuria with time. Several studies have demonstrated the value of closed drainage in delaying bacteriuria associated with the indwelling urethral catheter and the ineffectiveness of systemic chemoprophylaxis. 1 • 7 The advantages and limitations of the closed drainage system were examined by Kunin and McCormack. 7 They found that during routine use in a general hospital 50 per cent of male patients acquired bacteriuria in 13.5 days, while the same proportion of female patients became infected by 11 days. Ancillary measures to improve catheter care have been largely unsuccessful, including application of antimicrobialcontaining catheter lubricants or of catheters impregnated with antimicrobial substances, 8 direct daily intraurethral instillation through catheter ports of lubricant containing polymyxin B 9 and the use of a hydrophilic polymer-coated catheter. 10 An evaluation of 8 different drainage systems, some with air vents and 1 without, has shown no significant difference in the rates of bacterial colonization. 11 Several investigators have sought to decrease the risk of catheter-associated bacteriuria by venting the proximal end of the drainage line. 12' 13 The rationale was to eliminate potential mucosal trauma resulting from negative pressure in the drain line, pulling the mucosa into the eyes of the catheter. Tupasi and Kunin found that 1 top vented system did not alter the flow of urine into the bag or retention of urine in the tubing. 14 However, no bacteriologic studies were done. Our study was designed to evaluate in a controlled, randomized, double-blind fashion the efficacy of another top vented system in delaying the onset of bacteriuria when compared to a non-vented system.
216
217
VENTED DRA!l..,T1\GE PRE\!ENTit~JG INFECTION
Filtered
Filtered
air
air
vented system showed a definite decrease in risk of bacteriuria (17 of 160 vented versus 40 of 156 non-vented). Application of the life table method to the cumulative 10-day experience yields bacteriuric rates of 66 and 26 per cent for non-vented and vented groups, respectively (p less than 0005). Analysis of the daily cumulative p values revealed a remarkable stability about the p equal to 0.03 level (0.029 to 0.034), with the exception of day 2 when p equaled 0.01. If the differential effect of the vented system were constant one would expect progressively smaller p values as evidence accumulated. Thus, the constant probability suggests a diminishing effect during the 10-day period, a diminishing sample size or both. An attempt was made to monitor catheter-induced trauma associated with each drainage system by measuring urinary hemoglobin in each specimen. Frequency of hemoglobinuria was approximately 90 per cent for vented and non-vented patients. When evaluated on days 4, 5 and 6, the values ranged from 2 to 6 mg. per 100 ml. urine, with the exception of l patient in the vented group who had 83.5 mg. per 100 ml. on day 5. TABLE
1. Characteristics of 506 patients in study Vented No.(%) Pts.
Department: Medical Surgical OB-GYN Urology Orthopedic Neurology Age (yrs.): 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90 or greater
FIG. 1. Drainage system and circumferential vent in catheter connector.
prior to the bacteriuric end point. 1 • Statistical analysis was done by modification of the life table method to use Fisher's exact tests (l-tailed). 17 Each tail probability, Pi, was converted into a normal score, Zi, using the normal table in reverse; the normal scores were added and the sum divided by V!to get a resultant standard normal variable for which a probability was then ascertained in the normal probability table.
Sex: Female Male Antimicrobials: All Penicillin Ampicillin Carhenicillin Cephalosporins Erythromycin Tetracycline Chloramphenicol Clindamycin Gentamicin Streptomycin Kanamycin Diabetes Totals
Non-Vented No.("') Pts. ,n
57 29 66 44 38 17
(23) (12) (26) (16) (15) (7)
68 39 54 38 39 17
(27) (15) (21) (15) (15) (7)
2 19 25 42 30 43 58 30 2
(1) (8) (10) (17) (12) (17) (23) (12) (1)
1 15 20 33 44 47 59 32 4
(0.5) (6) (8) (13) (17) (18) (23) (13) (2)
160 (64) 91 (36)
156 (61) 99 (39)
128 5 24 2 81 0 14 0 3 11 0 0 23 251
125 6 28 3 75 2 16 2 1 9 1 2 23 255
(51) (4) (19) (2) (63) (0) (11) (0) (2) (9)
(0) (0) (9) (50)
(49) (5) (22) (2) (60) (2) (13) (2) (1) (7) (1) (2) (9)
(50)
RESULTS
Characterization of the population. Of the 1,915 patients screened 506 were available for evaluation under the protocol. Matching of the 2 drainage bag groups was quite good, as shown in the breakdown by age, sex, service, receipt of antimicrobial therapy and diagnosis of diabetes (table 1). Classification of organisms recovered from patients who acquired bacteriuria is shown in table 2. The distribution of species is similar between groups. Figure 2 reveals the decrease of patients at risk as catheters were removed or patients died or were discharged from the hospital. The cumulative risk of infection for vented and non-vented groups according to sex is shown in figure 3. Within the group of male patients no significant difference in bacteriuric rates could be demonstrated after 10 days (12 of 91 vented versus 12 of 99 non-vented). In contrast, female patients using the
TABLE
2. Characterization of micro-organisms recovered in cases in
which bacteriuria developed during catheterization Vented No.(%)
Pts. Escherichia coli Enterococcus Pseudomonas Proteus Klebsiella Staphylococcus Enterobacter Serratia Diphtheroid Yeast
8 5 3 0 0 2 1
(38) (24) (14) (0) (0) (10) (5) 1 (5) 0 (0) 1 (5)
Non-Vented No. Pts, (%) 19 7 6 5 3 3 0 0 2 2
(40) (15) (13) (11) (6) (6) (0) (0) (4) (4)
218
MONSON AND ASSOCIATES
300 Key:
250
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Vol. 117, February
Copyright © 1977 by The Williams & Wilkins Co.
Printed in U.S.A.
EVALUATION OF A VENTED DRAINAGE SYSTEM IN PREVENTION OF BACTERIURIA THOMAS P. MONSON,* FIDEL V. MACALALAD, J. WAYNE HAMMAN
AND
CALVIN M. KUNIN
From the Department of Medicine, University of Wisconsin and the Veterans Administration Hospital, Madison, Wisconsin, and the Abbott Laboratories and the Department of Surgery, Northwestern University Medical School, Chicago, Illinois
ABSTRACT
A vented urinary drainage system was compared to an otherwise identical non-vented system in a prospective, randomized, double-blind study. Among the 316 female patients evaluated there was a significant reduction in the rate of bacteriuria after 10 days using the vented system (66 per cent in the non-vented group versus 26 per cent in the vented group, p less than 0.05), while no significant difference could be demonstrated among the 190 male patients. We used urine hemoglobin as an indicator of mucosal trauma that might predispose to bacteriuria and no significant difference could be shown between the 2 drainage systems. and insertion of the catheter an initial urine specimen was collected; drainage bag identification and location were accomplished by means of the patient charge slip sent to Central Supply. A daily report of all drainage bags was compiled by the study nurse. Drainage bags were supplied by Abbott Laboratories in sterile packages identified only with a study code number. The code was not broken until the study was completed. Descriptions of drainage systems. The drainage system consists of a drain line with 122 cm. (48 inches) of tubing, 0.7 cm. (9/32 inches) in diameter, that enters the top of the 2,500 ml. drainage bag (fig. 1). In this top vented system filtered air is admitted into the drainage line through a circumferential vent built into the catheter connector. The vent consists of a 0.45 mµ. non-wet bacterial-retentive filter. For the control non-vented system used in our study the bacterial-retentive filter was occluded with plastic to prevent air entry in a manner such that the 2 systems could not be distinguished. Units were numbered in a randomized fashion for blind assignment to patients. Monitoring of the system. All urethral catheters were monitored daily by a study nurse by aspiration of a small quantity of urine from the proximal end using a sterile disposable syringe. The area to be punctured was prepared by sponging with a 70 per cent alcohol solution. Urine specimens obtained in this manner were brought to the laboratory within 1 to 2 hours. A dilution pour plate was prepared using trypticase soy agar. Plates were allowed to harden and were read after 24 to 48 hours. Colony counts were reported by number, with 10,000 colonies per milliliter or greater in 2 consecutive specimens considered the significant level of bacteriuria for the purpose of this study. Hemoglobin analysis. Urine for hemoglobin assay was taken simultaneously with specimens for culture and frozen at minus MATERIALS AND METHODS 35C until assayed. Analysis of urine hemoglobin was done Study procedure. This study was performed in a 500-bed according to the technique of McCall 1 5 using a Turner 350 community hospital to compare a top vented with a control spectrophotometer. non-vented system. Nurses, attendants and orderlies were Analysis of data. All patients with an initially positive urine instructed in the care of the drainage bag. They were particu- culture and those whose catheter or drainage bag was removed larly urged not to break the connection between the catheter or changed within 24 hours after insertion were deleted from and drainage tube. Irrigation of the catheters was discouraged, the study. Charts were reviewed as patients were discharged except for procedures necessary for the care of postoperative from the hospital, died or when catheters were removed. urologic patients and when obstruction of the catheter was Pertinent clinical characteristics, including concomitant use of suspected. After random assignment of the drainage system systemic antimicrobial agents, were recorded. The cumulative risk of developing bacteriuria was calculated by the life table Accepted for publication May 14, 1976. * Current address: Department of Medicine, Veterans Administra- method, which provides the expected rates of bacteriuria, tion Hospital, 300 E. Roosevelt Rd., Little Rock, Arkansas 72206. making adjustments for the loss of patients from the study
The indwelling urethral catheter is one of the most frequently used and valuable forms of urinary diversion. However, it carries the risk of acquisition of bacteriuria with time. Several studies have demonstrated the value of closed drainage in delaying bacteriuria associated with the indwelling urethral catheter and the ineffectiveness of systemic chemoprophylaxis. 1 • 7 The advantages and limitations of the closed drainage system were examined by Kunin and McCormack. 7 They found that during routine use in a general hospital 50 per cent of male patients acquired bacteriuria in 13.5 days, while the same proportion of female patients became infected by 11 days. Ancillary measures to improve catheter care have been largely unsuccessful, including application of antimicrobialcontaining catheter lubricants or of catheters impregnated with antimicrobial substances, 8 direct daily intraurethral instillation through catheter ports of lubricant containing polymyxin B 9 and the use of a hydrophilic polymer-coated catheter. 10 An evaluation of 8 different drainage systems, some with air vents and 1 without, has shown no significant difference in the rates of bacterial colonization. 11 Several investigators have sought to decrease the risk of catheter-associated bacteriuria by venting the proximal end of the drainage line. 12' 13 The rationale was to eliminate potential mucosal trauma resulting from negative pressure in the drain line, pulling the mucosa into the eyes of the catheter. Tupasi and Kunin found that 1 top vented system did not alter the flow of urine into the bag or retention of urine in the tubing. 14 However, no bacteriologic studies were done. Our study was designed to evaluate in a controlled, randomized, double-blind fashion the efficacy of another top vented system in delaying the onset of bacteriuria when compared to a non-vented system.
216
217
VENTED DRA!l..,T1\GE PRE\!ENTit~JG INFECTION
Filtered
Filtered
air
air
vented system showed a definite decrease in risk of bacteriuria (17 of 160 vented versus 40 of 156 non-vented). Application of the life table method to the cumulative 10-day experience yields bacteriuric rates of 66 and 26 per cent for non-vented and vented groups, respectively (p less than 0005). Analysis of the daily cumulative p values revealed a remarkable stability about the p equal to 0.03 level (0.029 to 0.034), with the exception of day 2 when p equaled 0.01. If the differential effect of the vented system were constant one would expect progressively smaller p values as evidence accumulated. Thus, the constant probability suggests a diminishing effect during the 10-day period, a diminishing sample size or both. An attempt was made to monitor catheter-induced trauma associated with each drainage system by measuring urinary hemoglobin in each specimen. Frequency of hemoglobinuria was approximately 90 per cent for vented and non-vented patients. When evaluated on days 4, 5 and 6, the values ranged from 2 to 6 mg. per 100 ml. urine, with the exception of l patient in the vented group who had 83.5 mg. per 100 ml. on day 5. TABLE
1. Characteristics of 506 patients in study Vented No.(%) Pts.
Department: Medical Surgical OB-GYN Urology Orthopedic Neurology Age (yrs.): 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90 or greater
FIG. 1. Drainage system and circumferential vent in catheter connector.
prior to the bacteriuric end point. 1 • Statistical analysis was done by modification of the life table method to use Fisher's exact tests (l-tailed). 17 Each tail probability, Pi, was converted into a normal score, Zi, using the normal table in reverse; the normal scores were added and the sum divided by V!to get a resultant standard normal variable for which a probability was then ascertained in the normal probability table.
Sex: Female Male Antimicrobials: All Penicillin Ampicillin Carhenicillin Cephalosporins Erythromycin Tetracycline Chloramphenicol Clindamycin Gentamicin Streptomycin Kanamycin Diabetes Totals
Non-Vented No.("') Pts. ,n
57 29 66 44 38 17
(23) (12) (26) (16) (15) (7)
68 39 54 38 39 17
(27) (15) (21) (15) (15) (7)
2 19 25 42 30 43 58 30 2
(1) (8) (10) (17) (12) (17) (23) (12) (1)
1 15 20 33 44 47 59 32 4
(0.5) (6) (8) (13) (17) (18) (23) (13) (2)
160 (64) 91 (36)
156 (61) 99 (39)
128 5 24 2 81 0 14 0 3 11 0 0 23 251
125 6 28 3 75 2 16 2 1 9 1 2 23 255
(51) (4) (19) (2) (63) (0) (11) (0) (2) (9)
(0) (0) (9) (50)
(49) (5) (22) (2) (60) (2) (13) (2) (1) (7) (1) (2) (9)
(50)
RESULTS
Characterization of the population. Of the 1,915 patients screened 506 were available for evaluation under the protocol. Matching of the 2 drainage bag groups was quite good, as shown in the breakdown by age, sex, service, receipt of antimicrobial therapy and diagnosis of diabetes (table 1). Classification of organisms recovered from patients who acquired bacteriuria is shown in table 2. The distribution of species is similar between groups. Figure 2 reveals the decrease of patients at risk as catheters were removed or patients died or were discharged from the hospital. The cumulative risk of infection for vented and non-vented groups according to sex is shown in figure 3. Within the group of male patients no significant difference in bacteriuric rates could be demonstrated after 10 days (12 of 91 vented versus 12 of 99 non-vented). In contrast, female patients using the
TABLE
2. Characterization of micro-organisms recovered in cases in
which bacteriuria developed during catheterization Vented No.(%)
Pts. Escherichia coli Enterococcus Pseudomonas Proteus Klebsiella Staphylococcus Enterobacter Serratia Diphtheroid Yeast
8 5 3 0 0 2 1
(38) (24) (14) (0) (0) (10) (5) 1 (5) 0 (0) 1 (5)
Non-Vented No. Pts, (%) 19 7 6 5 3 3 0 0 2 2
(40) (15) (13) (11) (6) (6) (0) (0) (4) (4)
218
MONSON AND ASSOCIATES
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250
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